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Title: A handbook of systematic botany
Author: Warming, Johannes Eugenius
Language: English
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Copyright Status: Not copyrighted in the United States. If you live elsewhere check the laws of your country before downloading this ebook. See comments about copyright issues at end of book.

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BOTANY ***



                              A HANDBOOK

                                  OF

                           SYSTEMATIC BOTANY

                                  BY

                            DR. E. WARMING

         _Professor of Botany in the University of Copenhagen_

                    WITH A REVISION OF THE FUNGI BY

                           DR. E. KNOBLAUCH,
                              _Karlsruhe_

                       TRANSLATED AND EDITED BY
                       M. C. POTTER, M.A. F.L.S.

           _Professor of Botany in the University of Durham
                College of Science, Newcastle-upon-Tyne
      Author of “An Elementary Text-book of Agricultural Botany”_

                        WITH 610 ILLUSTRATIONS

    [Illustration]

                                London
                        SWAN SONNENSCHEIN & CO
                       NEW YORK: MACMILLAN & CO
                                 1895



                           BUTLER & TANNER,
                      THE SELWOOD PRINTING WORKS,
                          FROME, AND LONDON.



                               PREFACE.


The present translation of Dr. E. Warming’s _Haandbog i den
Systematiske Botanik_ is taken from the text of the 3rd Danish
Edition (1892), and from Dr. Knoblauch’s German Edition (1890), and
the book has been further enriched by numerous additional notes which
have been kindly sent to me by the author. Dr. Warming’s work has long
been recognised as an original and important contribution to Systematic
Botanical Literature, and I have only to regret that the pressure
of other scientific duties has delayed its presentation to English
readers. Dr. Warming desires me to record his high appreciation of the
careful translation of Dr. Knoblauch, and his obligation to him for a
number of corrections and improvements of which he has made use in the
3rd Danish Edition. In a few instances I have made slight additions
to the text; these, however, appear as footnotes, or are enclosed in
square brackets.

In the present Edition the Thallophytes have been revised and
rearranged from notes supplied to me by Dr. Knoblauch, to whom I am
indebted for the Classification of the Fungi, according to the more
recent investigations of Brefeld. The Bacteria have been revised by
Dr. Migula, the Florideæ rearranged after Schmitz, and the Taphrinaceæ
after Sadebeck. The main body of the text of the Algæ and Fungi remains
as it was originally written by Dr. Wille and Dr. Rostrup in the Danish
Edition, though in many places considerable alterations and additions
have been made. For the sake of comparison a tabular key to the
Classification adopted in the Danish Edition is given in the Appendix.

In the Angiosperms I have retained the sequence of orders in the Danish
original, and have not rearranged them according to the systems
more familiar to English students. In any rearrangement much of the
significance of Dr. Warming’s valuable and original observations
would have been lost, and also from a teacher’s point of view I have
found this system of great value. Although at present it may not be
completely satisfactory, yet as an attempt to explain the mutual
relationships, development and retrogression of many of the orders, it
may be considered to have a distinct advantage over the more artificial
systems founded upon Jussieu’s Divisions of Polypetalæ, Gamopetalæ, and
Apetalæ.

With reference to the principles of the systematic arrangement adopted,
I may here insert the following brief communication from the author
(dated March, 1890), which he has requested me to quote from the
preface of Dr. Knoblauch’s edition:--“Each form which, on comparative
morphological considerations, is clearly less simple, or can be shown
to have arisen by reduction or through abortion of another type having
the same fundamental structure, or in which a further differentiation
and division of labour is found, will be regarded as younger, and as
far as possible, and so far as other considerations will admit, will
be reviewed later than the ‘simpler,’ more complete, or richer forms.
For instance, to serve as an illustration: EPIGYNY and PERIGYNY are
less simple than HYPOGNY; the Epigynous _Sympetalæ_, _Choripetalæ_,
_Monocotyledones_ are, therefore, treated last, the _Hydrocharitaceæ_
are considered last under the _Helobieæ_, etc. ZYGOMORPHY is younger
than ACTINOMORPHY; the _Scitamineæ_ and _Gynandræ_ therefore follow
after the _Liliifloræ_, the _Scrophulariaceæ_ after the _Solanaceæ_,
_Linaria_ after _Verbascum_, etc. FORMS WITH UNITED LEAVES indicate
younger types than those with free leaves; hence the _Sympetalæ_
come after the _Choripetalæ_, the _Sileneæ_ after the _Alsineæ_, the
_Malcaceæ_ after the _Sterculiaceæ_ and _Tiliaceæ_, etc.

“ACYCLIC (spiral-leaved) flowers are older than cyclic
(verticillate-leaved) with a definite number, comparing, of course,
only those with the same fundamental structure. The _Veronica_-type
must be considered as younger, for example, than _Digitalis_
and _Antirrhinum_, these again as younger than _Scrophularia_;
_Verbascum_, on the contrary, is the least reduced, and therefore
considered as the oldest form. Similarly the one-seeded, nut-fruited
_Ranunculaceæ_ are considered as a later type (with evident abortion)
than the many-seeded, folicular forms of the Order; the _Paronychieæ_
and _Chenopodiaceæ_ as reduced forms of the _Alsineæ_ type; and the
occurrence of few seeds in an ovary as generally arising through
reduction of the many-seeded forms. The _Cyperaceæ_ are regarded as
a form derived from the _Juncaceæ_ through reduction, and associated
with this, as is so often the case, there is a complication of the
inflorescence; the _Dipsacaceæ_ are again regarded as a form proceeding
from the _Valerianaceæ_ by a similar reduction, and these in their
turn as an offshoot from the _Caprifoliaceæ_, etc. Of course these
principles of systematic arrangement could only be applied very
generally; for teaching purposes they have often required modification.”

In preparing the translation considerable difficulty has been
experienced in finding a satisfactory rendering of several terms which
have no exact equivalent in English. I may here especially mention the
term Vorblatt (Forblad) which I have translated by the term bracteole,
when it clearly applied to the first leaf (or leaves) on a pedicel; but
in discussing questions of general morphology a term was much needed
to include both vegetative and floral shoots, and for this I have
employed the term “Fore-leaf.” Also, the term “Floral-leaf” has been
adopted as an equivalent of “Hochblatt,” and the term “bract” has been
limited to a leaf subtending a flower. I have followed Dr. E. L. Mark
in translating the word “Anlage” by “Fundament.”

At the end of the book will be found a short appendix giving an outline
of some of the earlier systems of Classification, with a more complete
account of that of Hooker and Bentham.

In a book of this character it is almost impossible to avoid some
errors, but it is hoped that these will be comparatively few. In
correcting the proof-sheets I have received invaluable assistance
from Dr. Warming and Dr. Knoblauch, who have kindly read through
every sheet, and to whom I am greatly indebted for many criticisms
and suggestions. I have also to thank Mr. I. H. Burkill for his kind
assistance in looking over the proofs of the Monocotyledons and
Dicotyledons, and Mr. Harold Wager for kindly reading through the
proofs of the Algæ and Fungi. My thanks are also especially due to Mr.
E. L. Danielsen, and I wish to take this opportunity of acknowledging
the very considerable help which I have received from him in
translating from the Original Danish.
                                                     M. C. POTTER.
_January, 1895._



                          TABLE OF CONTENTS.

             BEING THE SYSTEM OF CLASSIFICATION ADOPTED IN
                          THE PRESENT VOLUME.

      (_The Algæ and Fungi rearranged in co-operation with Dr. E.
    Knoblauch, the other Divisions as in the 3rd Danish Edition._)


                                                                PAGE

                    DIVISION I. THALLOPHYTA                        4

    A. Sub-Division. Myxomycetes, Slime-Fungi                      5

    B. Sub-Division. Algæ                                          8

        Class 1. SYNGENETICÆ                                      14

          „   2. DINOFLAGELLATA                                   16

          „   3. DIATOMEÆ                                         18

          „   4. SCHIZOPHYTA                                      22

              Family 1. Schizophyceæ                              22

                 „   2. Bacteria                                  26

        Class 5. CONJUGATÆ                                        41

          „   6. CHLOROPHYCEÆ                                     46

              Family 1. Protococcoideæ                            47

                 „   2. Confervoideæ                              53

                 „   3. Siphoneæ                                  59

        Class 7. CHARACEÆ                                         64

          „   8. PHÆOPHYCEÆ (OLIVE-BROWN SEAWEEDS)                68

              Family 1. Phæosporeæ                                68

                 „   2. Cyclosporeæ                               73

        Class 9. DICTYOTALES                                      76

          „  10. RHODOPHYCEÆ (RED SEAWEEDS)                       77

              Family 1. Bangioideæ                                77

                 „   2. Florideæ                                  78

    C. Sub-Division. Fungi      84

        Class 1. PHYCOMYCETES                                     96

          Sub-Class 1. _Zygomycetes_                              96

              „     2. _Oomycetes_                               100

              Family 1. Entomophthorales                         102

                 „   2. Chytridiales                             102

                 „   3. Mycosiphonales                           104

        Class 2. MESOMYCETES                                     108

          Sub-Class 1. _Hemiasci_                                108

              „     2. _Hemibasidii_                             109

        Class 3. MYCOMYCETES (HIGHER FUNGI)                      114

          Sub-Class 1. _Ascomycetes_                             114

            Series 1. Exoasci                                    116

               „   2. Carpoasci                                  118

              Family 1. Gymnoascales                             118

                 „   2. Perisporiales                            119

                 „   3. Pyrenomycetes                            125

                 „   4. Hysteriales                              132

                 „   5. Discomycetes                             132

                 „   6. Helvellales                              136

                     Ascolichenes                                136

          Sub-Class 2. _Basidiomycetes_                          144

            Series 1. Protobasidomycetes                         145

               „   2. Autobasidiomycetes                         157

              Family 1. Dacryomycetes                            159

                 „   2. Hymenomycetes                            159

                 „   3. Phalloideæ                               172

                 „   4. Gasteromycetes                           173

                     Basidiolichenes                             176

              Fungi Imperfecti                                   176


                DIVISION II. MUSCINEÆ (MOSSES)                   181

        Class 1. HEPATICÆ                                        188

              Family 1. Marchantieæ                              190

                 „   2. Anthoceroteæ                             191

                 „   3. Jungermannieæ                            191

        Class 2. MUSCI FRONDOSI                                  192

              Family 1. Sphagneæ                                 193

                 „   2. Schizocarpeæ                             195

                 „   3. Cleistocarpeæ                            195

                 „   4. Stegocarpeæ                              195


                  DIVISION III. PTERIDOPHYTA                     198

        Class 1. FILICINÆ                                        205

          Sub-Class 1. _Filices_                                 205

              Family 1. Eusporangiatæ                            210

                 „   2. Leptosporangiatæ                         212

          Sub-Class 2. _Hydropterideæ_                           215

        Class 2. EQUISETINÆ (HORSETAILS)                         221

          Sub-Class 1. _Isosporous Equisetinæ_                   221

              „     2. _Heterosporous Equisetinæ_                225

        Class 3. LYCOPODINÆ (CLUB MOSSES)                        226

          Sub-Class 1. _Lycopodieæ_                              226

              „     2. _Selaginelleæ_                            228

        TRANSITION FROM THE CRYPTOGAMS TO THE PHANEROGAMS        234

           Asexual Generation of the Cormophytes                 234

           Sexual Generation; Fertilisation                      243


               DIVISION IV. GYMNOSPERMÆ                          251

        Class 1. CYCADEÆ (CYCADS)                                252

          „   2. CONIFERÆ (PINE-TREES)                           255

              Family 1. Taxoideæ                                 259

                 „ 2. Pinoideæ                                   262

        Class 3. GNETEÆ                                          270

                  Fossil Gymnosperms                             271


                   DIVISION V. ANGIOSPERMÆ                       273

        Class 1. MONOCOTYLEDONES                                 274

              Family 1. Helobieæ                                 278

                 „   2. Glumifloræ                               283

                 „   3. Spadicifloræ                             297

                 „   4. Enantioblastæ                            308

                 „   5. Liliifloræ                               309

                 „   6. Scitamineæ                               323

                 „   7. Gynandræ                                 328

        Class 2. DICOTYLEDONES                                   334

          Sub-Class 1. _Choripetalæ_                             337

              Family 1. Salicifloræ                              337

                 „   2. Casuarinifloræ                           339

                 „   3. Quercifloræ                              340

                 „   4. Juglandifloræ                            349

                 „   5. Urticifloræ                              351

                 „   6. Polygonifloræ                            358

                 „   7. Curvembryæ                               363

                 „   8. Cactifloræ                               375

                 „   9. Polycarpicæ                              377

                 „  10. Rhœadinæ                                 393

                 „  11. Cistifloræ                               406

                 „  12. Gruinales                                416

                 „  13. Columniferæ                              421

                 „  14. Tricoccæ                                 430

                 „  15. Terebinthinæ                             435

                 „  16. Aesculinæ                                439

                 „  17. Frangulinæ                               443

                 „  18. Thymelæinæ                               448

                 „  19. Saxifraginæ                              451

                 „  20. Rosifloræ                                456

                 „  21. Leguminosæ                               466

                 „  22. Passiflorinæ                             475

                 „  23. Myrtifloræ                               482

                 „  24. Umbellifloræ                             490

                 „  25. Hysterophyta                             498

          Sub-Class 2. _Sympetalæ_                               504

                          _A. Pentacyclicæ_                      506

              Family 26. Bicornes                                506

                 „   27. Diospyrinæ                              510

                 „   28. Primulinæ                               511

                          _B. Tetracyclicæ_                      514

              Family 29. Tubifloræ                               514

                 „   30. Personatæ                               517

                 „   31. Nuculiferæ                              531

                 „   32. Contortæ                                541

                 „   33. Rubiales                                548

                 „   34. Dipsacales                              556

                 „   35. Campanulinæ                             560

                 „   36. Aggregatæ                               564

    APPENDIX                                                     574

    INDEX                                                        593



                              CORRIGENDA.


    Page 9, line 12 from top, for _Hydrodicton_ read _Hydrodictyon_.
     „  14, lines 1 and 2 from top, for _as in the preceding case_
        read _in this case_.
     „  14,   „   2 and 15 from top, for _zygote_ read _oospore_.
     „  88, line 15 from bottom, for _Periphyses_ read _periphyses_.
     „ 124,   „   7  „    „   for _Chæromyces_ read _Choiromyces_.
     „ 142,   „   2  „    „   and in Fig. 137, for _Bœomyces_ read
        _Bæomyces_.
     „ 152,   „   2  „   top, for _Pirus_ read _Pyrus_.
     „ 152,   „   5  „    „   for _Crategus_ read _Cratægus_.
     „ 216, Fig. 215, for _Salvina_ read _Salvinia_.
     „ 306, line  6 from top, for _Pista_ read _Pistia_.
     „ 316,   „  26   „   „   after Dracæna insert a comma.
     „ 337,   „  13   „   „   for _end_ read _beginning_.
     „ 483,   „  11   „  bottom, for _Lagerstrœmia_ read
        _Lagerstrœmeria_.

For ä, ö and ü read æ, œ and ue throughout.

The following are not officinal in the British Pharmacopœia:--page 316,
_Dracæna_ (Dragon’s-blood), _Smilax glabra_; p. 321, “Orris-root”;
p. 326, species of _Curcuma_, _Alpinia officinarum_; p. 333,
_Orchis_-species (“Salep”). On page 296, par. 4, only Pearl Barley is
offic. in the Brit. Phar.



               CLASSIFICATION OF THE VEGETABLE KINGDOM.


The Vegetable Kingdom is arranged in 5 Divisions.

Division I.--=Thallophyta=, =Stemless Plants=, or those which
are composed of a “thallus,” _i.e._ organs of nourishment which
are not differentiated into root (in the sense in which this term is
used among the higher plants), stem, or leaf. Vascular bundles are
wanting. Conjugation and fertilisation in various ways; among most of
the Fungi only vegetative multiplication.

   In contradistinction to the Thallophytes all other plants are
   called “Stem-plants” (“Cormophyta”), because their shoots are
   leaf-bearing stems. The name Thallophyta (Stemless-plants) is
   to some extent unsuitable, since many of the higher Algæ are
   differentiated into stem and leaf.

The Thallophytes are again separated into 3 sub-divisions, namely:

    Sub-Division =A.=--=Myxomycetes, Slime-Fungi=, with only 1 class.

    Sub-Division =B.=--=Algæ=, with 10 classes:
        Class 1. Syngeneticæ.
          „   2. Dinoflagellata, Peridinea.
          „   3. Diatomeæ, Diatoms.
          „   4. Schizophyta, Fission Algæ.
          „   5. Conjugatæ.
          „   6. Chlorophyceæ, Green Algæ.
          „   7. Characeæ, Stone-worts.
          „   8. Phæophyceæ, Brown Algæ.
          „   9. Dictyotales.
          „  10. Rhodophyceæ, Red Algæ.

    Sub-Division =C.=--=Fungi=, with 3 classes:
        Class 1. Phycomycetes.
          „   2. Mesomycetes.
          „   3. Mycomycetes, Higher Fungi.

Division II.--=Bryophyta or Muscineæ, Mosses.= These have
leaf-bearing shoots, but neither true roots nor vascular bundles. The
lowest Mosses have, however, a thallus. Fertilisation is accomplished
by means of self-motile, spirally coiled spermatozoids, through the
agency of water. From the fertilised oosphere a “fruit-body” (capsule)
with unicellular organs of reproduction (spores) is produced. The spore
on germination gives rise to the vegetative system, which bears the
organs of sexual reproduction; and this system is divided into two
stages--the protonema, and the leaf-bearing plant produced on it.

Alternation of generations:

     I. The protonema and the entire nutritive system which
          bears the organs of sexual reproduction.
    II. The capsule-like sporangium, with spores.
     2 Classes: 1. Hepaticæ, Liverworts.
                2. Musci, Leafy Mosses.

Division III.--=Pteridophyta or Vascular Cryptogams=, =Fern-like
Plants= having leaf-bearing shoots, true roots, and vascular bundles
with tracheides and sieve-tubes. Fertilisation as in the Mosses. From
the fertilised oosphere the leaf-bearing shoot arises, which bears
on its leaves the reproductive organs, the spores, in capsule-like
sporangia. From the germination of the spore a small prothallium is
formed, which bears the sexual reproductive organs.

Alternation of generations:

     I. Prothallium with organs of sexual reproduction.
    II. Leaf-bearing shoot with capsule-like sporangia.
     3 Classes: 1. Filicinæ, True Ferns.
                2. Equisetinæ, Horsetails.
                3. Lycopodinæ, Club-mosses.

Division IV.--=Gymnospermæ.= The vegetative organs are in the
main similar to those in the 3rd Division; special shoots are modified
into flowers for the service of reproduction. From the oosphere, which
is fertilised by means of the pollen-tube, the leaf-bearing plant is
derived; this passes the first period of its life as an embryo in
the seed, and continues its development when the germination of the
seed takes place. The organs corresponding to the spores of the two
preceding Divisions, are called respectively the pollen-grain and
embryo-sac. The pollen-grains are multicellular; i.e. they contain
an indistinct prothallium. In the embryo-sac a prothallium, rich in
reserve material (endosperm), with female organs of reproduction, is
developed BEFORE FERTILISATION. The pollen-grains are carried
by means of the wind to the ovules; these enclose the embryo-sac, and
are situated on the open fruit-leaf (carpel), which has no stigma.

Alternation of generations:

     I. Prothallium = Endosperm in ovule.
    II. Leaf-bearing plant, with flowers which produce the pollen-sac
          and ovule.
     3 Classes: 1. Cycadeæ.
                2. Coniferæ.
                3. Gnetaceæ.

Division V.--=Angiospermæ=. The members of this group are very
similar to those of Division IV. The ovules are, however, encased in
closed fruit-leaves (ovary), which have a special portion (stigma)
adapted for the reception and germination of the pollen-grains. The
pollen-grains are bicellular, but with only a membrane separating
the two nuclei; they are carried to the stigma by animals (chiefly
insects), by the wind, or by some other means. Endosperm is not formed
till AFTER FERTILISATION. Alternation of generations in the main as in
the Gymnosperms, but less distinct; while the sexual generation, the
prothallium, with the organs of fertilisation, is also strongly reduced.

    2 Classes:[1] 1. Monocotyledones. Embryo with one seed-leaf.
                  2. Dicotyledones. Embryo with two seed-leaves.

   For a long time the vegetable kingdom has been divided
   into. CRYPTOGAMS (so called because their organs
   of reproduction remained for some time undiscovered), and
   PHANEROGAMS or Flowering-plants which have evident
   sexual organs.

   The first three divisions belong to the Cryptogams, and the
   third and fourth divisions to the Phanerogams. This arrangement
   has no systematic value, but is very convenient in many ways.

   The Cryptogams are also known as Spore-plants, since they
   multiply by unicellular organs (spores), and the Phanerogams in
   contradistinction are called Seed-plants (Spermaphyta), since
   they multiply by seeds, multicellular bodies, the most important
   part of which is the embryo (a plant in its infancy). Mosses,
   Ferns, and Gymnosperms are together known as Archegoniatæ, since
   they possess in common a female organ of distinct structure, the
   Archegonium.



                              DIVISION I.

                             THALLOPHYTA.


The thallus in the simplest forms is unicellular; in the majority,
however, it is built up of many cells, which in a few instances are
exactly similar; but generally there is a division of labour, so
that certain cells undertake certain functions and are constructed
accordingly, while others have different work and corresponding
structure. Vessels or similar high anatomical structures are seldom
formed, and the markings on the cell-wall are with few exceptions very
simple. The Myxomycetes occupy quite an isolated position; their organs
of nourishment are naked masses of protoplasm (plasmodia).

As regards the external form, the thallus may be entirely without
special prominences (such as branches, members), but when such are
present they are all essentially alike in their origin and growth,
that is, disregarding the hair-structures which may be developed. A
shoot of a Seaweed or of a Lichen, etc., is essentially the same as
any other part of the plant; only among the highest Algæ (Characeæ,
certain Siphoneæ, _Sargassum_, and certain Red Seaweeds) do we find the
same differences between the various external organs of the plant body
as between stem and leaf, so that they must be distinguished by these
names.

_Roots_ of the same structure and development as in the Seed-plants
are not found, but _organs of attachment_ (rhizoids and haptera) serve
partly the biological functions of the root.

SYSTEMATIC DIVISION OF THE THALLOPHYTES. To the Thallophytes belong
three sub-divisions--Slime-Fungi, Algæ, and Fungi. Formerly the
Thallophytes were divided into Algæ, Fungi, and Lichens. But this
last group must be placed among the Fungi, since they are really
Fungi, which live symbiotically with Algæ. The _Slime-Fungi_ must be
separated from the true Fungi as a distinct subdivision. The _Algæ_
possess a colouring substance, which is generally green, brown, or
red, and by means of which they are able to build up organic compounds
from carbonic acid and water. The Bacteria, especially, form an
exception to the Algæ in this respect; like the Fungi and Slime-Fungi
they have as a rule no such colouring material, but must have organic
carbonaceous food; these plants form no starch, and need no light for
their vegetation (most Fungi require light for fructification). The
Myxomycetes, Bacteria, and Fungi derive their nourishment either as
_saprophytes_ from dead animal or vegetable matter, or as _parasites_
from living animals or plants (hosts), in which they very often cause
disease.

   A remark, however, must be made with regard to this division.
   Among the higher plants so much stress is not laid upon the
   biological relations as to divide them into “green” and
   “non-green”; _Cuscuta_ (Dodder), a parasite, is placed among
   the Convolvulaceæ, _Neottia_ and _Corallorhiza_, saprophytes,
   belong to the Orchidacere, although they live like Fungi,
   yet their relations live as Algæ. In the same manner there
   are some colourless parasitic or saprophytic forms among the
   Algæ, and stress must be laid upon the fact that not only the
   Blue-green Algæ, but also the Bacteria, which cannot assimilate
   carbonic-acid, belong to the Algæ group, Schizophyceæ. The
   reason for this is that systematic classifications must be based
   upon the relationship of form, development, and reproduction,
   and from this point of view we must regard the Bacteria as
   being the nearer relatives of the Blue-green Algæ. All the
   Thallophytes, which are designated Fungi (when the entire
   group of Slime-Fungi is left out), form in some measure a
   connected series of development which only in the lower forms
   (Phycomycetes) is related to the Algæ, and probably through them
   has taken its origin from the Algæ; the higher Fungi have then
   developed independently from this beginning. The distinction
   of colour referred to is therefore not the only one which
   separates the Algæ from the Fungi, but it is almost the only
   characteristic mark by which we can at once distinguish the two
   great sub-divisions of the Thallophytes.

   The first forms of life on earth were probably “Protistæ,”
   which had assimilating colour material, or in other words, they
   were Algæ because they could assimilate purely inorganic food
   substances, and there are some among these which belong to the
   simplest forms of all plants. Fungi and Slime-Fungi must have
   appeared later, because they are dependent on other plants which
   assimilate carbon.[2]


            _Sub-Division I._--=MYXOMYCETES, SLIME-FUNGI.=

The Slime-Fungi occupy quite an isolated position in the Vegetable
Kingdom, and are perhaps the most nearly related to the group of
Rhizopods in the Animal Kingdom. They live in and on organic remains,
especially rotten wood or leaves, etc., on the surface of which their
sporangia may be found.

They are organisms without chlorophyll, and in their vegetative
condition are masses of protoplasm without cell-wall (_plasmodia_).
They multiply by means of _spores_, which in the true Slime-Fungi[3]
are produced in sporangia, but in some others[4] free. The spores
are round cells (Fig. 1 _a_) which in all the true Slime-Fungi are
surrounded by a cell-wall. The wall bursts on germination, and the
contents float out in the water which is necessary for germination.
They move about with swimming and hopping motions like swarmspores
(_e_, _f_), having a cilia at the front end and provided with a
cell-nucleus and a pulsating vacuole. Later on they become a little
less active, and creep about more slowly, while they continue to alter
their form, shooting out arms in various places and drawing them in
again (_g_, _h_, _i_, _k_, _l_, _m_); in this stage they are called
_Myxamœbæ_.

  [Illustration: FIG. 1.--_a-l_ Development of “_Fuligo_” from
  spore to Myxamœba; _a-m_ are magnified 300 times; _m_ is a
  Myxamœba of _Lycogala epidendron_; _l´_ three Myxamœbæ of
  _Physarum album_ about to unite; _o_, a small portion of
  plasmodium, magnified 90 times.]

  [Illustration: FIG. 2.--The plasmodium (_a_) of _Stemonitis
  fusca_, commencing to form into sporangia (_b_); drawn on July
  9. The dark-brown sporangia were completely formed by the next
  morning; _c-e_ shows the development of their external form.]

  [Illustration: FIG. 3.--Four sporangia of _Stemonitis fusca_,
  fixed on a branch. _a_ The plasmodium.]

  [Illustration: FIG. 4.--Sporangium of _Arcyria incarnata_. _B_
  closed; _C_ open; _p_ wall of sporangium; _cp_ capilitium.]

The Myxamœba grows whilst taking up nourishment from the material in
which it lives, and multiplies by division. At a later stage a larger
or smaller number of Myxamœbæ may be seen to coalesce and form large
masses of protoplasm, _plasmodia_, which in the “Flowers of Tan” may
attain the size of the palm of a hand, or even larger, but in most
others are smaller. The plasmodia are independent, cream-like masses of
protoplasm, often containing grains of carbonate of lime and colouring
matter (the latter yellow in the Flowers of Tan). They creep about in
the decaying matter in which they live, by means of amœboid movements,
internal streamings of the protoplasm continually taking place; finally
they creep out to the surface, and very often attach themselves to
other objects, such as Mosses, and form sporangia (Fig. 2). These are
stalked or sessile and are generally cylindrical (Fig. 3), spherical
or pear-shaped (Fig. 4); they rarely attain a larger size than that of
a pin’s head, and are red, brown, white, blue, yellow, etc., with a
very delicate wall. In some genera may be found a “Capillitium” (Fig. 4
_cp_), or network of branched fine strands between the spores. Flowers
of Tan (_Fuligo septica_) has a fruit-body composed of many sporangia
(an Æthalium), which has the appearance of flat, irregular, brown
cakes, inside the fragile external layer of which a loose powder, the
spores, is found. It generally occurs on heaps of tanners’ bark, and
appears sometimes in hot-beds in which that material is used, and is
destructive by spreading itself over the young plants and choking them.

All the motile stages may pass into _resting stages_, the small forms
only surrounding themselves with a wall, but the large ones at the
same time divide in addition into polyhedral cells. When favourable
conditions arise, the walls dissolve and the whole appears again as a
naked (free-moving) mass of protoplasm.

To the genuine Slime-Fungi belong: _Arcyria_, _Trichia_, _Didymium_,
_Physarum_, _Stemonitis_, _Lycogala_, _Fuligo_, _Spumaria_,
_Reticularia_.

Some genera wanting a sporangium-wall belong to the Slime-Fungi:
_Ceratiomyxa_, whose fruit-body consists of polygonal plates, each
bearing stalked spores; _Dictyostelium_, in which the swarm-stage is
wanting and which has stalked spores. _Plasmodiophora brassicæ_ preys
upon the roots of cabbages and other cruciferous plants, causing large
swellings. _Pl. alni_ causes coral-shaped outgrowths on the roots of
the Alder (_Alnus_). _Phytomyxa leguminosarum_ may be found in small
knobs (tubercles) on the roots of leguminous plants. It is still
uncertain whether it is this Fungus or Bacteria which is the cause of
the formation of these tubercles.


                      _Sub-Division_ II.--=ALGÆ=.

=Mode of Life.= The Algæ (except most of the Bacteria) are themselves
able to form their organic material by the splitting up of the carbonic
acid contained in the water, or air in some cases, and for this purpose
need light. The majority live in water, fresh or salt, but many are
present on damp soil, stones, bark of trees, etc.

With the exception of the Bacteria, no saprophytes have actually been
determined to belong to this group, and only very few true parasites
(for instance, _Phyllosiphon arisari_, _Mycoidea_, etc.), but a
good many are found epiphytic or endophytic on other Algæ, or water
plants, and on animals (for instance, certain _Schizophyceæ_ and
_Protococcoideæ_; _Trichophilus welckeri_ in the hairs of _Bradypus_,
the Sloth), and several species in symbiotic relation to various Fungi
(species of Lichen), to Sponges (_e.g. Trentepohlia spongiophila_,
_Struvea delicatula_), and to sundry Infusoria and other lower
animals as Radiolarias, _Hydra_, etc. (the so-called _Zoochlorella_
and _Zooxantella_, which are perhaps partly stages in development of
various Green and Brown Algæ).

=Vegetative Organs.= The cells in all the Algæ (excepting certain
reproductive cells) are surrounded by a membrane which (with the
exception of the Bacteria) consists of pure or altered cellulose,
sometimes forming a gelatinous covering, at other times a harder one,
with deposits of chalk or silica formed in it. The cell-nucleus,
which in the Schizophyta is less differentiated, may be one or more
(_e.g. Hydrodictyon_, _Siphoneæ_) in each cell. Excepting in the
majority of the Bacteria, _colour materials_ (of which _chlorophyll_,
or modifications of it, always seems to be found) occur, which either
permeate the whole cytoplasm surrounding the cell-nucleus, as in most
of the coloured Schizophyta, or are contained in certain specially
formed small portions of protoplasm (chromatophores).

The individual at a certain stage of development consists nearly always
of only one cell; by its division multicellular individuals may arise,
or, if the daughter-cells separate immediately after the division, as
in many of the simplest forms, the individual will, during the whole
course of its existence, consist of only a single cell (unicellular
Algæ). In multicellular individuals the cells may be more or less
firmly connected, and all the cells of the individual may be exactly
alike, or a division of labour may take place, so that certain cells
undertake certain functions, and are constructed accordingly; this
may also occur in parts of the cell in the large unicellular and
multinuclear Algæ (Siphoneæ, p. 62).

The cells in most of the Algæ belong to the _parenchymatous_ form;
these, however, in the course of their growth, may very often become
somewhat oblong; in many Algæ (particularly Fucoideæ and Florideæ)
occur, moreover, _hyphæ-like threads_, which are very long, often
branched, and are either formed of a single cell, or, more frequently,
of a row of cells, having a well-pronounced apical growth. The
parenchymatous as well as the hyphæ-like cells may, in the higher
Algæ (especially in certain Fucoideæ and Florideæ), be further
differentiated, so that they form well-defined anatomico-physiological
systems of tissue, _i.e._ assimilating, conducting, storing, and
mechanical.

With regard to _the external form_, the thallus may present no
differentiation, as in many unicellular Algæ, or in multicellular Algæ
of the lower order, which are then either equally developed in all
directions (_e.g. Pleurococcus_, Fig. 47), or form flat cell-plates
(_Merismopedium_) or threads (_Oscillaria_, Fig. 21). The first step
in the way of differentiation appears as a difference between apex and
base (_Rivularia_, _Porphyra_); but the division of labour may proceed
so that differences may arise between vegetative and reproductive cells
(_Œdogonium_, Fig. 54); hairs and organs of attachment (rhizoids and
haptera), which biologically serve as roots, are developed, and even
leaves in certain forms of high order, belonging to different classes
(_e.g. Caulerpa_, Fig. 59; _Characeæ_, Fig. 61; _Sargassum_, Fig. 72;
and many Florideæ).

=The non-sexual reproduction= takes place _vegetatively_, in many
instances, simply by division into two, and more or less complete
separation of the divisional products (Diatomaceæ, Desmidiaceæ (Fig.
36), many Fission-plants, etc.), or by detached portions of the thallus
(_e.g. Caulerpa_, _Ulva lactuca_, etc.; among many Schizophyceæ,
small filaments known as _hormogonia_ are set free), or _asexually_ by
special reproductive cells (_spores_) set free from the thallus; these
may be either _stationary_ or _motile_. The stationary reproductive
cells (spores) may either be devoid of cell-wall (tetraspores of the
Florideæ), or may possess a cell-wall; in the latter case they may be
formed directly from the vegetative cells, generally by the thickening
of the walls (_akinetes_), or only after a process of re-juvenescence
(_aplanospores_). Aplanospores, as well as akinetes, may either
germinate immediately or may become resting-cells, which germinate only
after a period of rest.

THE MOTILE ASEXUAL REPRODUCTIVE CELLS are spherical, egg- or
pear-shaped, naked, _swarmspores_ (_zoospores_), which have arisen
in other cells (_zoosporangia_), and propel themselves through the
water by means of cilia; or they are _Phyto-Amœbæ_, which have no
cilia and creep on a substratum by means of pseudopodia. The cilia,
which are formed from the protoplasm (in the Bacteria, however, from
the membrane), are mostly situated at the pointed and colourless end,
which is directed forwards when in motion, and are 1, 2 (Fig. 5 _B_),
4 or more. Both the cilia in the Brown Algæ are attached to one side
(Fig. 65); they are occasionally situated in a circle round the front
end (_Œdogonium_, Fig. 6 _a_, and _Derbesia_), or are very numerous
and situated in pairs distributed over a large part or nearly the
whole of the zoospore (_Vaucheria_). Besides being provided with one
or more nuclei (_Vaucheria_), they may also have a red “eye spot”
and vacuoles, which are sometimes pulsating, _i.e._ they appear and
reappear at certain intervals. The swarmspores move about in the
water in irregular paths, and apparently quite voluntarily, revolving
round their longer axes; but they come to the surface of the water in
great numbers either because of their dependence on light, or driven
by warm currents in the water, or attracted by some passing mass of
food material. The swarmspores germinate, each forming a new plant,
as their movement ceases they surround themselves with a cell-wall,
grow, and then divide; in Fig. 6 _b_, two may be seen in the condition
of germination, and about to attach themselves by means of the front
end, which has been developed into haptera (see also Fig. 5 _B_, lowest
figure).

=The sexual reproduction= here, probably in all cases, consists in the
coalescence of two masses of protoplasm, that is, in the fusion of
their nuclei.

  [Illustration: FIG. 5.--_Cladophora glomerata. A_ The lower
  cells are full of swarmspores, whilst from the upper one the
  greater part have escaped through the aperture _m_. _B_ Free and
  germinating swarmspores.]

  [Illustration: FIG. 6.--_Œdogonium_: _a_ (free), _b_ germinating
  swarmspores.]

  [Illustration: FIG. 7.--_Zanardinia collaris. A_ Male
  gametangia (the small-celled) and female gametangia
  (large-celled). _C_ Female gamete. _D_ Male gamete. _B E_
  Fertilisation. _F_ Zygote. _G_ Germinating zygote.]

The simplest and lowest form is termed =conjugation=, or =isogamous=
fertilisation, and is characterized by the fact that the two coalescing
cells (termed gametes) are equal, or almost equal, in shape and size
(the female gamete in the _Cutleriaceæ_, _e.g. Zanardinia collaris_,
Fig. 7, is considerably larger than the male gamete). The cell in
which the _gametes_ are developed is called a _gametaugium_, and the
reproductive cell formed by their union--which generally has a thick
wall and only germinates after a short period of rest--is termed a
_zygote_ or _zygospore_. The conjugation takes place in two ways:--

(_a_) In the one way the gametes are motile cells (_planogametes_,
_zoogametes_, Fig. 8), which unite in pairs during their swarming
hither and thither in the water; during this process they lie side by
side (Fig. 8 _d_), generally at first touching at the clear anterior
end, and after a time they coalesce and become a motionless _zygote_,
which surrounds itself with a cell-wall (Fig. 8 _e_). This form of
conjugation is found in _Ulothrix_ (Fig. 8 _d_), _Acetabularia_, and
other Algæ (Figs. 45, 56, 66).

  [Illustration: FIG. 8.--_Ulothrix zonata_: a portion of
  a thread with zoospores, of which two are formed in each
  cell (zoosporangium), the dark spots upon them are the “red
  eye-spots”; 1, 2, 3, 4 depict successive stages in the
  development of the zoospores; _b_ a single zoospore, at _v_ the
  pulsating vacuole; _c_ portion of a thread with gametes, of which
  sixteen are formed in each gametangium; _d_ gametes free and in
  conjugation; _e_ conjugation has been effected, and the formed
  zygotes are in the resting condition.]

(_b_) Among other Algæ (_e.g. Diatomaceæ_ and _Conjugatæ_), the
conjugating cells continue to be surrounded by the cell-wall of
the mother-cell (_aplanogametes_ in an _aplanogametangium_); the
aplanogametangia generally grow out into short branches, which lie
close together and touch one another, the wall at the point of contact
is then dissolved (Fig. 39). Through the aperture thus formed, the
aplanogametes unite, as in the first instance, and form a rounded
zygote, which immediately surrounds itself with a cell-wall. Various
modifications occur; compare Figs. 37, 39, 41, 43.

  [Illustration: FIG. 9.--Fertilisation in the Bladder-wrack
  (_Fucus vesiculosus_).]

  [Illustration: FIG. 10.--_Sphæroplea annulina._]

The highest form of the sexual reproduction is the =Egg- or Oogamous=
fertilisation. The two coalescing cells are in the main unlike each
other in form as well as size. The one which is considered as the male,
and is known as the _spermatozoid_ (_antherozoid_), developes as a rule
in large numbers in each mother-cell (_antheridium_); they are often
self-motile (except in the Florideæ, where they are named _spermatia_),
and are many times smaller than the other kind, the female, which
is known as the _egg-cell_, (_oosphere_). The egg-cell is always a
motionless, spherical, primordial cell which can either float about
freely in the water, as in the Fucaceæ (Fig. 9), or is surrounded by
a cell-wall (_oogonium_); generally only one oosphere is to be found
in each oogonium, but several occur in _Sphæroplea_ (Fig. 10). The
result of the spermatozoid coalescing with the egg-cell is, as in this
case, the formation of a oospore, which generally undergoes a period of
rest before germination (the Florideæ are an exception, a fruit-body,
_cystocarp_, being produced as the result of coalescence).

   An example of fertilisation is afforded by the Alga, _Sphæroplea
   annulina_ (Fig. 10). The filamentous thallus is formed of
   cylindrical cells with many vacuoles (_r_ in _A_); some cells
   develope egg-cells (_B_), others spermatozoids (_C_), the latter
   in a particularly large number. The egg-cells are spherical,
   the spermatozoids of a club- or elongated pear-shape with two
   cilia at the front end (_G_; _E_ is however a swarmspore).
   The spermatozoids escape from their cells through apertures
   in the wall (_o_ in _C_) and enter through similar apertures
   (_o_ in _B_) to the egg-cells. The colourless front end of the
   spermatozoid is united at first with the “receptive spot” of the
   egg-cell (see _F_), and afterwards completely coalesces with
   it. The result is the formation of a oospore with wart-like
   excrescences (_D_).

The female (_parthenogenesis_) or male (_androgenesis_) sexual cell
may, sometimes without any preceding fertilisation, form a new
individual (_e.g. Ulothrix zonata_, _Cylindrocapsa_, etc.).

=Systematic division of the Algæ.= The Algæ are divided into the
following ten classes:

   1. SYNGENETICÆ; 2. DINOFLAGELLATA, or PERIDINEA; 3. DIATOMACEÆ;
   4. SCHIZOPHYTA, FISSION-ALGÆ; 5. CONJUGATÆ; 6. CHLOROPHYCEÆ,
   GREEN-ALGÆ; 7. CHARACEÆ, STONE-WORTS; 8. PHÆOPHYCEÆ; 9.
   DICTYOTALES; 10. RHODOPHYCEÆ.

Among the lowest forms of the Algæ, the Syngeneticæ, the
Dinoflagellata, and the unicellular Volvocaceæ (Chlamydomoneæ),
distinct transitional forms are found approaching the animal kingdom,
which can be grouped as animals or plants according to their method of
taking food or other characteristics. Only an artificial boundary can
therefore be drawn between the animal and vegetable kingdoms. In the
following pages only those forms which possess _chromatophores_,
and have _no mouth_, will be considered as Algæ.


                        Class 1. =Syngeneticæ.=

The individuals are uni- or multicellular, free-swimming or motionless.
The cells (which in the multicellular forms are loosely connected
together, often only by mucilaginous envelopes) are naked or surrounded
by a mucilaginous cell-wall, in which silica is never embedded. They
contain one cell-nucleus, one or more pulsating vacuoles, and one to
two band- or plate-like chromatophores with a brown or yellow colour,
and sometimes a pyrenoid.

Reproduction takes place by vegetative division, or asexually by
zoospores, akinetes (or aplanospores?). Sexual reproduction is unknown.
They are all fresh water forms.

   To this class may perhaps be assigned the recently arranged and
   very little known orders of _Calcocytaceæ_, _Murracytaceæ_,
   _Xanthellaceæ_, and _Dictyochaceæ_, which partly occur in the
   free condition in the sea, in the so-called “Plankton,” and
   partly symbiotic in various lower marine animals.

The _Syngeneticæ_ are closely related to certain forms in the
animal kingdom, as the Flagellatæ.

Order 1. =Chrysomonadinaceæ.= Individuals, uni- or multicellular,
swimming in free condition, naked or surrounded by a mucilaginous
covering. The cells are generally oval or elongated, with 2 (rarely
only 1) cilia, almost of the same length, and generally with a red
“eye-spot” at their base, and with 2 (rarely 1 only) band-shaped
chromatophores. Reproduction by the longitudinal division of the
individual cells either during the swarming, or during a resting stage;
in the multicellular forms also by the liberation of one or more cells,
which in the latter case are connected together.

   A. Unicellular: _Chromulina_, _Cryptoglena_, _Microglena_,
   _Nephroselmis_.

   B. Multicellular: _Uroglena_, _Syncrypta_ (Fig. 11), _Synura_.

  [Illustration: FIG. 11.--_Syncrypta volvox_: the multicellular
  individual is surrounded by a mucilaginous granular envelope.]

   Among the unicellular Chrysomonadinaceæ are probably classed
   some forms which are only stages in the development of the
   multicellular, or of other _Syngeneticæ_.

Order 2. =Chrysopyxaceæ= are unicellular, and differ mainly
from the preceding in being attached either on a slime-thread
(_Stylochrysalis_), or enclosed in an envelope (_Chrysopyxis_,
Fig. 12). They have two cilia, and multiply by longitudinal
(_Chrysopyxis_) or transverse division, and the swarming of one of the
daughter-individuals (zoospore). Division may also take place in a
motionless stage (_palmella-stage_).

  [Illustration: FIG. 12.--_Chrsopyxis bipes_: _m_ envelope, _Ec_
  chromatophore, _cv_ contractile vacuole.]

Order 3. =Dinobryinaceæ.= The individuals are originally attached,
uni- or multicellular; each individual cell is distinctly contractile,
and fixed at the bottom of a cup-shaped, open envelope. Cilia 2, but
of unequal length. Asexual reproduction by zoospores, which are formed
by straight or oblique longitudinal division of the mother-cell,
during a palmella-stage which is produced in the winter aplanospores.
_Epipyxis_, _Dinobryon_.

Order 4. =Hydruraceæ.= The individuals are attached, without cilia,
multicellular, branched, and with apical growth. The cells are
spherical, but in the final stage almost spindle-shaped, and embedded
in large masses of mucilage. Asexual reproduction by zoospores which
are tetrahedric, with 1 cilia, and by resting akinetes. _Hydrurus_ is
most common in mountain brooks.


                      Class 2. =Dinoflagellata.=

The individuals are of a very variable form, but always unicellular,
and floating about in free condition. The cell is _dorsiventral_,
_bilateral_, _asymmetric_ and generally surrounded by a colourless
membrane, which has _no silica_ embedded in it, but is formed of
a substance allied to _cellulose_. The membrane, which externally
is provided with pores and raised borders, easily breaks up into
irregularly-shaped pieces. In the forms which have longitudinal and
cross furrows, _two cilia_ are fixed where these cross each other, and
project through a cleft in the membrane; one of these cilia _projects
freely_ and is directed longitudinally to the front or to the rear,
the other one _stretches crosswise_ and lies close to the cell, often
in a furrow (cross furrow). The chromatophores are coloured brown or
green and may either be two parallel (_Exuviella_), or several radially
placed, discs, which sometimes may coalesce and become a star-shaped
chromatophore. The coloring material (pyrrophyl) consists, in addition
to a modification of chlorophyl, also of _phycopyrrin_ and _peridinin_;
this colour is sometimes more or less masked by the products of
assimilation which consist of yellow, red or colourless oil (?) and
starch. Cell-nucleus one: in _Polydinida_ several nuclei are found;
contractile vacuoles many, which partly open in the cilia-cleft (Fig.
13 _gs_). In some an eye-spot, coloured red by hæmatochrome, is found.
Pyrenoids occur perhaps in _Exuviella_ and _Amphidinium_.

THE REPRODUCTION takes place as far as is known at present, only
by division. This, in many salt water forms, may take place in the
swarming condition, and, in that case, is always parallel to the
longitudinal axis. The daughter-individuals, each of which retains half
of the original shell, sometimes do not separate at once from each
other, and thus chains (_e.g._ in _Ceratium_) of several connected
individuals may be formed. In others, the division occurs after
the cilia have been thrown off and the cell-contents rounded. The
daughter-cells then adopt entirely new cell-walls. A palmella-stage
(motionless division-stage) sometimes appears to take place, and also
aplanospores (?) with one or two horn-like elongations (_e.g._ in
_Peridinium cinctum_ and _P. tabulatum_); at germination one, or after
division, two or more, new individuals may be formed.

Sexual reproduction has not been observed with certainty.

The Dinoflagellata move forward or backward, turning round their
longitudinal axes; in their motion they are influenced by the action
of light. The motion possibly may be produced only by the transverse
cilium, which vibrates rapidly; whilst the longitudinal cilium moves
slowly, and is supposed to serve mainly as a steering apparatus. They
live principally in salt water, but also in fresh.

Besides the coloured forms, which are able to make their own organic
compounds by the splitting up of the carbonic acid contained in the
water, there are a few colourless forms (_e.g. Gymnodinium spirale_),
or such as do not possess chromatophores (_Polykrikos_); these appear
to live saprophytically, and may be able to absorb solid bodies with
which they come in contact.

Dinoflagellata occur in the “Plankton” of the open sea, where they form
together with Diatomaceæ the basis for the animal life. It is known
with certainty that some salt water forms (like the _Noctiluca_,
which belongs to the animal kingdom and to which they are perhaps
related) produce light, known as phosphorescence.

  [Illustration: FIG. 13.--_A_ and _B Glenodinium cinctum_. _A_
  seen from the ventral side, _B_ from behind; _fg_ transverse
  cilium; _g_ longitudinal cilium; _ch_ chromatophores; _a_ starch;
  _n_ cell-nucleus; _v_ vacuole; _oc_ eye-spot; _C Ceratium
  tetraceros_ from the ventral side; _r_ the right, _b_ the
  posterior horn; _lf_ longitudinal furrow; _gs_ cilium-cleft; _v_
  vacuole; _g_ longitudinal cilium. (_A_ and _B_ mag. 450 times,
  _C_ 337 times.)]

   _Dinoflagellata_ (_Peridinea_, _Cilioflagellata_) are allied
   through their lowest form (_Exuviella_) to the Syngeneticæ and
   especially to the order Chrysomonadinaceæ. They may be divided
   into three orders.

Order 1. =Adinida.= Without transverse or longitudinal furrows, but
enclosed in two shells, and with two parallel chromatophores in each
cell. _Exuviella_, _Prorocentrum_.

Order 2. =Dinifera.= With tranverse and generally longitudinal furrow.
Many radially-placed, disc-formed chromatophores. The most common
genera are--_Ceratium_ (Fig. 13), _Peridinium_, _Glenodinium_ (Fig.
13), _Gymnodinium_, _Dinophysis_.

Order 3. =Polydinida.= With several transverse furrows, no
chromatophores, and several cell-nuclei. Only one genus--_Polykrikos_.

   The order _Polydinida_ deviates in a high degree from the
   other Dinoflagellata, not only by its many tranverse furrows,
   each with its own transverse cilium, and by the absence of
   chromatophores, but also in having several cell-nuclei and a
   kind of stinging capsule, which otherwise does not occur within
   the whole class. It may therefore be questionable whether this
   order should really be placed in the vegetable kingdom.


                         Class 3. =Diatomeæ.=

The individuals--each known as a _frustule_--assume very various
forms and may be unicellular or multicellular, but present no
differentiation; many similar cells may be connected in chains,
embedded in mucilaginous masses, or attached to mucilaginous
stalks. The cells are bilateral or centric, often asymmetrical,
slightly dorsiventral and have no cilia; those living in the free
condition have the power of sliding upon a firm substratum. The cell
contains 1 cell-nucleus and 1–2 plate-shaped or several disc-shaped
chromatophores. The colouring material “_Melinophyl_” contains, in
addition to a modification of chlorophyl, a brown colouring matter,
_diatomin_. 1 or 2 pyrenoids sometimes occur. Starch is wanting and the
first product of assimilation appears to be a kind of oil (?).

  [Illustration: FIG. 14.--_Pinnularia_: _B_, from the edge, shows
  the valves fitting together; _A_, a valve.]

  [Illustration: FIG. 15.--Various Diatomaceæ. A _Diatoma vulgare_.
  B _Tabellaria flocculosa_. C _Navicula tumida_ (lateral views).
  D _Gomphonema constrictum_ (lateral views). E _Navicula
  west[=i][=i]_ (lateral views).]

The cell-walls are _impregnated with silica_ to such a degree that
they are imperishable and are therefore able to contribute in a great
measure to the formation of the earth’s crust. The structure of their
cell-wall is most peculiar and _differs from all other plants_ (except
certain Desmidiaceæ); it does not consist of a single piece but is
made up of two--the “shells”--(compare _Exuviella_ and _Prorocentrum_
among the Dinoflagellata) which are fitted into each other, one being
a little larger than the other and embracing its edge, like a box with
its lid (Fig. 14 _B_). The two parts which correspond to the bottom
and lid of the box are known as _valves_. Along the central line of
the valves a longitudinal _rib_ may often be found, interrupted at
its centre by a small cleft (perhaps homologous with the cilia-cleft
of the Dinoflagellata), through which the protoplasm is enabled to
communicate with the exterior (Fig. 14 _A_). It is principally by
reason of the valves, which bear numerous fine, transverse ribs, striæ
or warts, etc. (Figs. 14, 15, 17), that the Diatomeæ have become so
well known and employed as test objects in microscopical science. When
the division takes place, the two shells are separated a little from
each other, and after the cell-contents have divided into two masses,
two new shells are formed, one fitting into the larger valve, the
other one into the smaller valve of the original frustule. The latter
cell (frustule) is thus, upon the whole, smaller than the mother-cell,
and as the cells do not increase in size, some frustules are smaller
than the ones from which they are derived, and thus, by repeated
divisions, it follows that smaller and smaller frustules are produced.
This continued diminution in size is, however, compensated for by the
formation, when the cells have been reduced to a certain minimum, of
_auxospores_, 2–3 times larger. These may either be formed _asexually_
by the protoplasm of a cell increasing, rounding off and surrounding
itself with a new wall (_e.g. Melosira_) or after _conjugation_,
which may take place with various modifications: 1. Two individuals
unite after the secretion of a quantity of mucilage, and the valves
then commence to separate from each other, on the side which the two
individuals turn towards each other. The protoplasmic bodies now
release themselves from their cell-wall, and each rounds off to form an
ellipsoidal mass; these two protoplasmic masses (gametes) coalesce to
form a zygote, the cell-nuclei and chromatophores also fusing together.
The zygote increases in size, and surrounds itself with a firm, smooth,
siliceous wall--the _perizonium_. The auxospores, whichever way they
arise, are not resting stages. The germination of the zygote commences
by the protoplasm withdrawing itself slightly from the cell-wall and
constructing first the larger valve, and later on the smaller one;
finally the membrane of the zygote bursts (_e.g. Himantidium_). 2.
The conjugation occurs in a similar manner, but the protoplasm of the
cells divides transversely before conjugation into two daughter-cells.
Those lying opposite one another conjugate (Fig. 16) and form two
zygotes. The formation of the perizonium, and germination take place
as in the preceding instance (_e.g. Epithemia_). 3. Two cells place
themselves parallel to each other, and each of the two cell-contents,
without coalescing, becomes an auxospore. The formation of the wall
takes place as in the preceding case. This is found in the Naviculeæ,
Cymbelleæ, the Gomphonemeæ (_e.g. Frustulia_, _Cocconema_).

  [Illustration: FIG. 16.--Conjugation of _Cymbella variabilis_.
  _A_, The protoplasm in the two cells has divided into two masses;
  _B_ these masses coalesce in pairs; the cells (_B C_) enclosed
  in a mucilaginous matrix. _C D_ Auxospores and their formation.]

The Diatomaceæ may be found in salt as well as in fresh water (often
in such masses that the colour of the water or mud becomes yellow or
brown; in the same manner the genera _Chætoceros_, _Rhizosolenia_,
_Coscinodiscus_, and several others, form large slime-masses,
“Plankton” on the surface of the sea), on damp soil and in dust blown
by the wind. They occur as fossils in the recent formations, often
in large deposits (siliceous earth, mountain meal), as in the cement
lime in Jutland, the alluvial deposits beneath Berlin, in clay strata
beneath peat bogs, in guano, etc. These accumulations of fossilized
diatoms are used in the manufacture of dynamite and in various
manufactures.

The Diatomaceæ appear nearest to, and must be placed as a group
co-ordinate with the Dinoflagellata, as they doubtless may be supposed
to derive their origin from forms resembling _Exuviella_, and to have
lost the cilia. The resemblances to the Desmidiaceæ which are striking
in many respects, can only be conceived as analogies, and cannot be
founded upon homologies, and it is therefore impossible to regard them
as proof of genetic relationship. The family contains only one order.

  [Illustration: FIG. 17.--Various Diatomeæ. _A Synedra radians._
  _B Epithemia turgida_ (from the two different sides). _C Cymbella
  cuspidata. D Cocconeis pediculus_ (on the right several
  situated on a portion of a plant, on the left a single one more
  highly magnified).]

Order 1. =Diatomaceæ.= This order may be divided into two
sub-orders, viz.--

Sub-Order 1. =Placochromaticæ.= The chromatophores are discoid, large,
1 or 2 in each cell; the structure of the valves is bilateral and
always without reticulate markings. The following groups belong to
this sub-order: _Gomphonemeæ_, _Cymbelleæ_, _Amphoreæ_, _Achnantheæ_,
_Cocconeideæ_, _Naviculeæ_, _Amphipleureæ_, _Plagiotropideæ_,
_Amphitropideæ_, _Nitzchieæ_, _Surirayeæ_, and _Eunotieæ_.

Sub-Order 2. =Coccochromaticæ.= The chromatophores are granular, small
and many in each cell. The structure of the cells is zygomorphic
or centric, often with reticulate markings. The following groups
belong to this sub-order: _Fragilarieæ_, _Meridieæ_, _Tabellarieæ_,
_Licmophoreæ_, _Biddulphieæ_, _Anguliferæ_, _Eupodisceæ_,
_Coscinodisceæ_, and _Melosireæ_.


                 Class 4. =Schizophyta, Fission-Algæ.=

The individuals are 1--many celled; the thallus consists in many of a
single cell, in others of chains of cells, the cells dividing in only
one definite direction (Figs. 18, 21). In certain Fission-Algæ the
cell-chain branches (Fig. 30) and a difference between the anterior
and the posterior ends of the chain is marked; in some, the cells may
be united into the form of flat plates by the cell-division taking
place in two directions; and in others into somewhat cubical masses, or
rounded lumps of a less decided form, by the divisions taking place in
three directions; or less defined masses may be formed by the divisions
taking place in all possible directions.

The cell-walls rarely contain cellulose, they often swell considerably
(Figs. 20, 22), and show distinct stratifications, or they are almost
completely changed into a mucilaginous mass in which the protoplasts
are embedded, _e.g._ in _Nostoc_ (Fig. 22), and in the “Zooglœa” stage
of the Bacteria (Fig. 27). Sexual reproduction is wanting. Vegetative
reproduction by division and the separation of the divisional products
by the splitting of the cell-wall or its becoming mucilaginous; among
the Nostocaceæ, Lyngbyaceæ, Scytonemaceæ, etc., “Hormogonia” are found;
in _Chamæsiphon_ and others single reproductive akinetes are formed.
Many Fission-Algæ conclude the growing period by the formation of
resting akinetes or aplanospores.

The Schizophyta may be divided into 2 families:

1. SCHIZOPHYCEÆ.

2. BACTERIA.


             Family 1. =Schizophyceæ,[5] Blue-Green Algæ.=

All the Blue-green Algæ are able to assimilate carbon by means of
a colouring material containing chlorophyll (cyanophyll); but the
chlorophyll in this substance is masked by a blue (phycocyan), or red
(phycoerythrin, _e.g._ in _Trichodesmium erythræum_ in the Red Sea)
colouring matter which may be extracted from them in cold water after
death. The colouring matter, in most of them, permeates the whole of
the protoplasm (excepting the cell-nucleus), but in a few (_e.g._
_Glaucocystis_, _Phragmonema_), slightly developed chromatophores are
to be found. Where the cells are united into filaments (cell-chains) a
differentiation into apex and base (_Rivulariaceæ_) may take place, and
also between ordinary vegetative cells and heterocysts; these latter
cannot divide, and are distinguished from the ordinary vegetative cells
(Fig. 22 _h_) by their larger size, yellow colour, and poverty of
contents. Branching sometimes occurs and is either true or spurious.

  [Illustration: FIG. 18.--_Microcoleus lyngbyanus_: _a_ portion of
  a filament, the thick sheath encloses only one cell-chain; in one
  place a cell is drawn out by the movement of the cell-chain; _b_
  the cell-chain has divided into two parts (“hormongonia”) which
  commence to separate from each other.]

The cell-chain in the spurious branching divides into two parts,
of which either one or both grow beyond the place of division
(Fig. 18) and often out to both sides (_e.g. Scytonema_), the
divisions however, always take place transversely to the longitudinal
direction of the cell-chain. In the true branching a cell elongates
in the direction transverse to the cell-chain, and the division
then takes place nearly at right angles to the former direction
(_Sirosiphoniaceæ_).

  [Illustration: FIG. 19.--_Cylindrospermum majus_: _a_ resting
  akinete with heterocyst; _b-d_ germinating stages of a resting
  akinete; _e_ filament with two heterocysts and the formation
  of new akinetes; _f_ part of a filament with a heterocyst, and
  mature resting akinete.]

Cilia are wanting, but the filaments are sometimes self-motile (_e.g._
hormogonia in _Nostoc_) and many partly turn round their axes, partly
slide forward or backward (_Oscillaria_).

Reproduction takes place by spores and hormogonia in addition to simple
cell-division. Hormogonia are peculiar fragments of a cell-chain
capable of motion, and often exhibit a vigorous motion in the sheath,
until at last they escape and grow into a new individual (Fig. 18).
The spores are reproductive akinetes (_Chamæsiphon_, etc.) or resting
akinetes; these latter arise by the vegetative cells enlarging and
constructing a thick cell-wall (Fig. 19 _e f_). On germination,
this cell-wall bursts and the new cell-chain elongates in the same
longitudinal direction as before (Fig. 19 _b c_). Many (_e.g._
_Oscillaria_) may however winter in their ordinary vegetative stage.
Aplanospores are wanting.

The Fission-Algæ are very prevalent in fresh water and on damp soil,
less so in salt water; they also often occur in water which abounds in
decaying matter. Some are found in warm springs with a temperature as
high as 50° C.

The Family may be divided into 2 sub-families:

1. HOMOCYSTEÆ (heterocysts are wanting): _Chroococcaceæ_, _Lyngbyaceæ_
and _Chamœsiphonaceæ_.

2. HETEROCYSTEÆ (heterocysts present): _Nostocaceæ_, _Rivulariaceæ_,
_Scytonemaceæ_ and _Sirosiphoniaceæ_.

Order 1. =Chroococcaceæ.= The individuals are 1--many-celled, but all
the cells are uniform, united to form plates or irregular masses, often
surrounded by a mucilaginous cell-wall, but never forming cell-chains.
Multiplication by division and sometimes by resting akinetes, but
reproductive akinetes are wanting. _Chroococcus_, _Aphanocapsa_,
_Glœocapsa_ (Fig. 20), _Cœlosphærium_, _Merismopedium_, _Glaucocystis_,
_Oncobyrsa_, _Polycystis_, _Gomphosphæria_.

  [Illustration: FIG. 20.--_Glœocapsa atrata_: _A_, _B_, _C_, _D_,
  _E_ various stages of development.]

  [Illustration: FIG. 21.--_Oscillaria_; =a= terminal, =b= central
  portion of a filament.]

Order 2. =Lyngbyaceæ (Oscillariaceæ).= The cells are discoid (Fig.
21), united to straight or spirally twisted, free filaments, which are
unbranched, or with spurious branching. The ends of the cell-chains
are similar. Heterocysts absent. Reproduction by synakinetes, resting
akinetes are wanting. _Oscillaria_ (Fig. 21), _Spirulina_, _Lyngbya_,
_Microcoleus_, _Symploca_, _Plectonema_.

Order 3. =Chamæsiphonaceæ.= The individuals are 1--many-celled,
attached, unbranched filaments with differentiation into apex and base,
without heterocysts. Multiplication by reproductive akinetes; resting
akinetes are wanting. _Dermocarpa_, _Clastidium_, _Chamæsiphon_,
_Godlewskia_, _Phragmonema_.

Order 4. =Nostocaceæ.= The individuals are formed of multicellular,
unbranched filaments, without differentiation into apex and base;
heterocysts present. Reproduction by synakinetes and resting akinetes.

  [Illustration: FIG. 22.--_Nostoc verrucosum. A_ The plant in
  its natural size; an irregularly folded jelly-like mass. _B_ One
  of the cell-chains enlarged, with its heterocysts (_h_), embedded
  in its mucilaginous sheath.]

Some genera are not mucilaginous, _e.g. Cylindrospermum_ (Fig. 19).
The cell-chains in others, _e.g. Nostoc_, wind in between one another
and are embedded in large structureless jelly-like masses, which may
attain the size of a plum or even larger (Fig. 22); sometimes they are
found floating in the water, sometimes attached to other bodies. Other
genera as follows: _Aphanizomenon_ and _Anabæna_ (in lakes and smaller
pieces of water); _Nodularia_ is partly pelagic. Some occur in the
intercellular spaces of higher plants, thus _Nostoc_-forms are found
in _Anthoceros_, _Blasia_, _Sphagnum_, _Lemna_, and in the roots of
_Cycas_ and _Gunnera_; _Anabæna_ in _Azolla_.

Order 5. =Rivulariaceæ.= The individuals are multicellular filaments,
with differentiation into apex and base; spurious branching, and a
heterocyst at the base of each filament, reproduction by synakinetes
and resting akinetes, rarely by simple reproductive akinetes.
_Rivularia_, _Glœotrichia_, _Isactis_, _Calothrix_.

Order 6. =Scytonemaceæ.= The individuals are formed of multicellular
filaments with no longitudinal division; differentiation into apex and
base very slight or altogether absent; branching spurious; heterocysts
present. Reproduction by synakinetes, rarely by resting akinetes and
ordinary reproductive akinetes. _Tolypothrix_, _Scytonema_, _Hassalia_,
_Microchæte_.

Order 7. =Sirosiphoniaceæ.= The individuals are formed of multicellular
threads with longitudinal divisions; true branching and heterocysts,
and often distinct differentiation into apex and base. Reproduction
by synakinetes, rarely by resting akinetes and ordinary reproductive
akinetes. _Hapalosiphon_, _Stigonema_, _Capsosira_, _Nostocopsis_,
_Mastigocoleus_.


                       Family 2. =Bacteria.=[6]

The Bacteria (also known as Schizomycetes, and Fission-Fungi) are the
smallest known organisms, and form a parallel group to the Blue-green
Algæ, but separated from these Algæ by the absence of their colouring
material; chlorophyll is only found in a few Bacteria.

The various forms under which the vegetative condition of the Bacteria
appear, are termed as follows:

1. GLOBULAR FORMS, COCCI (Figs. 27, 30 _c_): spherical or ellipsoidal,
single cells, which, however, are usually loosely massed together and
generally termed “_Micrococci_.”

2. ROD-LIKE FORMS: more or less elongated bodies; the shorter forms
have been styled “_Bacterium_” (in the narrower sense of the word),
and the term “_Bacillus_” has been applied to longer forms which are
straight and cylindrical (Figs. 28, 29, 30 _E_).

  [Illustration: FIG. 23.--_Spirillum sanguineum._ Four specimens.
  One has two cilia at the same end, the sulphur grains are seen
  internally.]

3. THREAD-LIKE FORMS: unbranched, long, round filaments, resembling
those of _Oscillaria_, are possessed by _Leptothrix_ (very thin,
non-granular filaments; Fig. 30 _A_, the small filaments) and
_Beggiatoa_ (thicker filaments, with strong, refractile grains or drops
of sulphur (Fig. 31); often self-motile). Branched filaments, with
false branching like many _Scytonemaceæ_, are found in _Cladothrix_
(Fig. 30 _B_, _G_).

4. SPIRAL FORMS: Rod-like or filamentous bodies, which more or less
strongly resemble a corkscrew with a spiral rising to the left. In
general these are termed _Spirilla_ (Fig. 23); very attenuated spirals,
_Vibriones_ (standing next to Fig. 30 _M_); if the filaments are
slender and flexible with a closely wound spiral, _Spirochætæ_ (Fig.
24).

5. The MERISMOPEDIUM-FORM, consisting of rounded cells arranged in
one plane, generally in groups of four, and produced by divisions
perpendicular to each other.

6. The SARCINA-FORM, consisting of roundish cells which are produced
by cellular division in all the three directions of space, united into
globular or ovoid masses (“parcels”) _e.g. Sarcina ventriculi_ (Figs.
25, 26).

  [Illustration: FIG. 24.--_Spirochæte obermeieri_, in active
  motion (_b_) and shortly before the termination of the fever
  (_c_); a blood corpuscles.]

All Bacteria are unicellular. In the case of the micrococci this is
self-evident, but in the “rod,” “thread,” and “spiral” Bacteria, very
often numerous cells remain united together and their individual
elements can only be recognised by the use of special reagents.

  [Illustration: FIG. 25.--_Sarcina ventriculi._ One surface only
  is generally seen. Those cells which are drawn with double
  contour are seen with the correct focus, and more distinctly than
  those cells lying deeper drawn with single contour.]

  [Illustration: FIG. 26.--_Sarcina minuta_: _a-d_ successive
  stages of one individual (from 4–10 p.m.); _f_ an individual of
  32 cells.]

The condition termed “Zooglœa,” which reminds us of _Nostoc_, is
produced by the cells becoming strongly mucilaginous. A number of
individuals in active division are found embedded in a mass of
mucilage, which either contains only one, or sometimes more, of the
above-named forms. The individuals may eventually swarm out and
continue their development in an isolated condition. Such mucilaginous
masses occur especially upon moist vegetables (potatoes, etc.), on the
surface of fluids with decaying raw or cooked materials, etc. The
mucilaginous envelope is thrown into folds when the Bacteria, with
their mucilaginous cell-walls, multiply so rapidly that there is no
more room on the surface of the fluid.

The cells of the Bacteria are constructed like other plant-cells in
so far as their diminutive size has allowed us to observe them. The
cell-wall only exceptionally shows the reactions of cellulose (in
_Sarcina_, _Leuconostoc_; also in a Vinegar-bacterium, _Bacterium
xylinum_); a mucilaginous external layer is always present. The body
of the cell mostly appears to be an uniform or finely granulated
protoplasm. Very few species (_e.g. Bacillus virens_) contain
chlorophyll; others are coloured red (purple sulphur Bacteria); the
majority are colourless. _Bacillus amylobacter_ shows a reaction
of a starch-like material when treated with iodine before the
spore-formation. Some Bacteria contain sulphur (see p. 37). The body,
which has been described as a _cell-nucleus_, is still of a doubtful
nature.

Artificial colourings with aniline dyes (especially methyl-violet,
gentian-violet, methylene-blue, fuchsin, Bismarck-brown and Vesuvin)
play an important part in the investigations of Bacteria.

MOVEMENT. Many Bacteria are self-motile; the long filaments of
_Beggiatoa_ exhibit movements resembling those of _Oscillaria_. In many
motile forms the presence of cilia or flagella has been proved by the
use of stains; many forms have one, others several cilia attached at
one or both ends (Fig. 23) or distributed irregularly over the whole
body; the cilia are apparently elongations of the mucilaginous covering
and not, as in the other Algæ of the protoplasm. In _Spirochæte_ the
movement is produced by the flexibility of the cell itself. Generally
speaking, the motion resembles that of swarm-cells (_i.e._ rotation
round the long axis and movement in irregular paths); but either end
has an equal power of proceeding forwards.

   The swarming motion must not be confounded with the hopping
   motion of the very minute particles under the microscope
   (Brownian movement).

VEGETATIVE REPRODUCTION takes place by continued transverse division;
hence the name “Fission-Fungi” or “Fission-Algæ,” has been applied to
the Bacteria.

SPORES. The spores are probably developed in two ways. In the
ENDOSPOROUS species (Figs. 28, 29), the spore arises as a new cell
inside the mother-cell. The spores are strongly refractile, smaller
than the mother-cell, and may be compared to the aplanospores of other
Algæ. In addition to these there are the ARTHROSPOROUS species in
which the cells, just as in _Nostoc_ and other Blue-green Algæ, assume
the properties of spores without previously undergoing an endogenous
new construction, and are able to germinate and form new vegetative
generations (Fig. 27). The formation of spores very often commences
when the vegetative development begins to be restricted.

  [Illustration: FIG. 27.--_Leuconostoc mesenterioides_: _a_
  a zooglœa, natural size; _b_ cross section of zooglœa; _c_
  filaments with spores; _d_ mature spores; _e-i_ successive stages
  of germination; in _e_ portions of the ruptured spore-wall are
  seen on the external side of the mucilaginous covering. (_b-i_
  magnified 520.)]

The spores germinate as in _Nostoc_ by the bursting of the external
layer of the cell-wall, either by a transverse or longitudinal cleft,
but always in the same way, in the same species (Fig. 28, example of
transverse cleft).

DISTRIBUTION. Bacteria and their germs capable of development, are
found everywhere, in the air (dust), in surface water, and in the
superficial layers of the soil. The number varies very much in
accordance with the nature of the place, season, etc. They enter,
together with air and food, into healthy animals and occur always in
their alimentary tract.

GROWTH AND REPRODUCTION depend upon the conditions of temperature.
There is a certain minimum, optimum and maximum for each species; for
instance (in degrees Centigrade)--

                                  Minim.     Opt.   Maxim.
    _Bacillus subtilis_             + 6     c. 30    + 50
    _B. anthracis_                   15     20–25      43
    _Spirillum choleræ asiaticæ_      8        37      40 (but grows
                                                           only feebly
                                                           if under
                                                           16°).
    _Bacterium tuberculosis_         28     37–38      42

  [Illustration: FIG. 28.--_Bacillus megaterium_: _a_ outline of a
  living, vegetative cell-rod; _b_ a living, motile, pair of rods;
  _p_ a similar 4-celled rod after the effects of iodine alcohol;
  _c_ a 5-celled rod in the first stages of spore-formation; _d-f_
  successive stages of spore-formation in one and the same pair
  of rods (in the course of an afternoon); _r_ a rod with mature
  spores; _g^1–g^3_ three stages of a 5-celled rod, with spores
  sown in nutritive solution; _h^1–h^2_, _i_, _k_, _l_ stages of
  germination; _m_ a rod in the act of transverse division, grown
  out from a spore which had been sown eight hours previously.
  (After de Bary; _a_ mag. 250, the other figures 600 times).]

  [Illustration: FIG. 29.--_Bacillus amylobacter._ Motile rods,
  partly cylindrical and without spores, partly swollen into
  various special shapes and with spore-formation in the swelling.
  _s_ Mature spore, with thick mucilaginous envelope. (After de
  Bary; mag. 600 times, with the exception of _s_, which is more
  highly magnified.)]

The functions of life cease on a slight excess of the maximum or
minimum temperature, numbness setting in when either of these limits
is passed. _Crenothrix_-threads provided with mucilaginous envelopes
may, according to Zopf, sustain a temperature of-10°. Some Bacteria are
said to be able to resist the exposure to as low a temperature as-110°
for a short time. It is not known at what degree of cold the death of
the Bacteria occurs: the greatest degree of heat which the vegetative
cells can withstand is about the same as that for other vegetative
plant-cells, namely, about 50–60° C. Certain Bacteria, _e.g. B.
thermophilus_, grow and thrive vigorously at 70° C. Many spores, on the
contrary, are able to bear far higher temperatures (in several species
a temperature for some duration of above 100°, those of _Bacillus
subtilis_, for instance, can withstand for hours a temperature of 100°
in nutrient solutions; the spores remain capable of development after
exposure to a dry heat of 123° C.).

The _Desiccation_ of the air, if prolonged, kills many forms when in
the vegetative condition. The spores however can bear a much longer
period of dryness, some even several years.

OXYGEN. Some species cannot live without a supply of free oxygen
(_Aerobic_), _e.g._ the Vinegar-bacteria, the Hay-bacilli, the
Anthrax-bacilli, the Cholera-_Microspira_. Other species again thrive
vigorously without supply of free oxygen, and are even checked in their
development by the admission of air (_Anaerobic_), _e.g._ the butyric
acid Bacterium (_Clostridium butyricium_ = _Bacillus amylobacter_).
A distinction may be drawn between obligate and facultative aerobics
and obligate and facultative anaerobics. Several Bacteria, producing
fermentation, may grow without the aid of oxygen when they are living
in a solution in which they can produce fermentation; but, if this is
not the case, they can only grow when a supply of oxygen is available.
A great number of the pathogenic Bacteria belong to the facultative
anaerobics.

A luminous Bacterium (_Bacillus phosphorescens_) which in the presence
of a supply of oxygen gives a bluish-white light, has been found in
sea-water. Phosphorescent Bacteria have frequently been observed
upon decaying sea-fish, as well as on the flesh of other animals; by
transferring the Bacteria from cod fish to beef, etc., the latter may
be made luminous.

_Organic carbon compounds_ are indispensable for all Bacteria, (except,
as it appears, for the nitrifying organisms), as they can only obtain
the necessary supplies of _carbon_ from this source. The supplies
of _nitrogen_, which also they cannot do without, can be obtained
equally as well from organic compounds as from inorganic salts, such as
saltpetre or ammonia-compounds. The various “ash-constituents” are also
essential for their nourishment.

While Moulds and Yeast-Fungi grow best in an acid substratum, the
_Bacteria_, on the other hand, generally thrive _best_ in a _neutral_
or slightly _alkaline_ one.

In _sterilization_, _disinfection_, and _antisepsis_, means are
employed by which the Bacteria are killed, or checked in their
development, for instance, by heat (ignition, cooking, hot vapours,
hot air, etc.), or poisons (acids, corrosive sublimate). The process
of preserving articles of food, in which they are boiled and then
hermetically sealed, aims at destroying the Bacteria, or the spores of
those which already may be present in them, and excluding all others.

As the Bacteria are unable to assimilate carbon from the carbonic
acid of the air, but must obtain it from the carbon-compounds already
in existence in the organic world, they are either _saprophytes_
or _parasites_. Some are exclusively either the one or the other,
_obligate_ saprophytes or parasites. But there are transitional
forms among them, some of which are at ordinary times saprophytes,
but may, when occasion offers, complete their development wholly or
partly as parasites--_facultative parasites_; others are generally
parasitic, but may also pass certain stages of development as
saprophytes--_facultative saprophytes_.

All chlorophyll-free organisms act in a transforming and disturbing
manner on the organic compounds from which they obtain their
nourishment, and while they themselves grow and multiply, they produce,
each after its kind, compounds of a less degree of complexity, _i.e._
they produce _fermentation_, _putrefaction_, sometimes the formation of
_poisons_, and in living beings often _disease_.

Those organisms which produce fermentation are called _ferments_;
this word, however, is also employed for similar transformations in
purely chemical materials (inorganic ferments or enzymes). Many organic
(“living”) ferments, among which are Yeast-cells and Bacteria, give
off during their development certain inorganic and soluble ferments
(enzymes) which may produce other transformations without themselves
being changed. Different organisms may produce in the same substratum
different kinds of transformation; alcoholic fermentation may for
instance be produced by different species of Fungi, but in different
proportions, and the same species produces in different substrata,
different transformations (_e.g._ the Vinegar-bacteria oxydize diluted
alcohol to vinegar, and eventually to carbonic acid and water).

   In the study of Bacteria it is absolutely necessary to sterilize
   the vessels employed in cultivation, the apparatus, and nutrient
   solutions, _i.e._ to free them from Bacteria germs and
   also to preserve the cultures from the intrusion of any foreign
   germs (“pure-cultures”). A firm, transparent, nutritive medium
   is frequently employed. This may be prepared by adding to
   the nutrient solutions (broth) either gelatine, or--when the
   Bacteria are to be cultivated at blood-heat--serum of sheep’s or
   calf’s blood, agar-agar or carragen; serum alone may in itself
   serve as a nutrient medium. The so-called “plate-cultures” are
   frequently employed, _i.e._ the germs are isolated by
   shaking them with the melted liquid nutrient gelatine, which
   is then spread on a glass plate and allowed to coagulate; when
   later on the individual germs grow into colonies, these remain
   separate in the solid substratum and it is easy to pursue
   their further development. Similar plate-cultures may also be
   cultivated in test-tubes and on microscopic slides. The slides
   and glass plates must be placed in “moist chambers” free from
   Bacteria. By sowing a few cells (if possible one) using a fine
   platinum wire, pure cultures for further investigation may be
   obtained.

   In order to prove the relationship between pathogenic Bacteria
   and certain diseases, the experimental production of pathogenic
   Bacteria by the inoculation of Bacteria from pure cultures into
   healthy animals, is very important.

It has not so far been possible to establish a _classification_
of the Bacteria, as the life-history of many species, has not yet
been sufficiently investigated.[7] The opinions of botanists are at
variance, in many cases, about the forms of growth of a particular
kind. Some species are pleomorphic (many-formed) while others possess
only one form.

The following Bacteria are =Saprophytes=:--

_Cladothrix dichotoma_ is common in stagnant and running water which is
impregnated with organic matter; the cell-chains have false branching.
According to Zopf, _Leptothrix ochracea_ is one of the forms of this
species which, in water containing ferrous iron (_e.g._ as FeCO_{3}),
regularly embeds ferric-oxide in its sheath by means of the activity
of the protoplasm. _Leptothrix ochracea_ and other Iron-bacteria,
according to Winogradsky (1888), do not continue their growth in water
free from protoxide of iron; while they multiply enormously in water
which contains this salt of iron. The large masses of ochre-coloured
slime, found in meadows, bogs, and lakes, are probably due to the
activity of the Iron-bacteria.

  [Illustration: FIG. 30.--_Cladothrix dichotoma._]

Those forms which, according to Zopf’s views, represent the forms
of development of _Cladothrix dichotoma_ are placed together in
Fig. 30. A represents a group of plants, seventy times magnified,
attached to a Vaucheria. The largest one is branched like a tree, with
branches of ordinary form; a specimen with spirally twisted branches
is seen to the right of the figure, at the lower part some small
_Leptothrix_-like forms. _B_ shows the manner of branching and an
incipient _Coccus_-formation. _C_ a _Coccus_-mass whose exit from the
sheath has been observed. _D_ the same mass as _C_ after the course of
a day, the Cocci having turned into _rods_. _E_ a group of Cocci in
which some have developed into shorter or longer rods. _F_ one of these
rods before and after treatment with picric acid, which causes the
chain-like structure to become apparent. _G_ a portion of a plant with
conspicuous sheath, two lateral branches are being formed. _H_ part of
a plant, whose cells have divided and form Cocci. The original form
of the cells in which the Cocci are embedded may still be recognised.
I. _Leptothrix_-filaments with conspicuous mucilaginous sheath, from
which a series of rods is about to emerge; the rod near the bottom
is dead, and has remained lying in the sheath. _K_ part of a plant
which is forming Cocci, those at the top are in the zooglœa-stage, at
the base they are elongating to form rods and _Leptothrix_-filaments.
_L_ a portion of a branched _Cladothrix_, which divides into motile
_Bacillus_-forms; the rays at the free ends indicate the currents
which the cilia produce in the water. _M_ a spirally-twisted, swarming
filament, before and after division into halves. _N_ part of a
tree-like zooglœa with Cocci and short rods.--All of these spirilla,
zooglœa, etc., which Zopf has connected with _Clad. dichotoma_, are
according to Winogradsky, independent organisms.

_Micrococcus ureæ_ produces _urinal fermentation_ (transformation of
urinal matter into ammonium carbonate); aerobic; round cells generally
united to form bent chains or a zooglœa.--Several other kinds of
Bacteria have the same action as this one: in damp soil containing
ammonia-compounds, _saltpetre-formations_ are produced by _M.
nitrificans_ and several different kinds of Bacteria.

_Micrococcus prodigiosus_ is found on articles of food containing
starch; “bleeding bread” is caused by this Bacterium, which has the
power of forming a red pigment; it also occurs in milk, and produces
lactic acid.

_Leuconostoc mesenterioides_ is the frog-spawn Bacterium (Fig. 27)
which is found in sugar manufactories, and has the power of producing
a viscous fermentation in saccharine solutions which have been derived
from plants, _e.g._ in beetroot-sugar manufactories, where large
accumulations of mucilage are formed at the expense of the sugar, with
an evolution of carbonic acid. The cell-rows, resembling somewhat a
pearl necklace, have thick mucilaginous cell-walls, and form white
“Nostoc”-lumps. The mucilage eventually deliquesces and the cells
separate from each other; arthrospores?--Similar viscous deteriorations
occur in beer and wine, which may then be drawn out into long, string
like filaments--“ropiness.”

_Bacterium aceti_, the Vinegar-bacterium, oxidizes alcohol into
acetic acid (acetous-fermentation) and forms a greyish covering of
Bacteria (“Vinegar-mother”) on the surface of the liquid; the acetic
acid formed, becomes by continued oxidization by _B. aceti_, again
transformed into carbonic acid and water. Aerobic; short cylindrical
cells, often united into chains, or to form a zooglœa; sometimes also
rod-and spindle-shaped. The Vinegar-bacteria and other kinds with
ball- or rod-forms sometimes become swollen, spindle-shaped, or oval
links; they are supposed to be diseased forms[8] (“Involution-forms”).

_Bacillus lacticus_ (_Bacterium acidi lactici_, Zopf) is always found
in milk which has stood for some time, and in sour foods (cabbage,
cucumbers, etc.); it turns the milk sour by producing lactic acid
fermentation in the sugar contained in the milk; the lactic acid
formed, eventually causes the coagulation of the casein. It resembles
the Vinegar-bacteria, occurring as small cylindrical cells, rarely in
short rows; not self-motile.--Several other Bacteria appear to act in
the same way, some occurring in the mouth of human beings; some of
these Bacteria give to butter its taste and flavour.

The _kefir-grains_ which are added to milk for the preparation of
kefir, contain in large numbers a Bacterium (_Dispora caucasica_) in
the zooglœa-form, a Yeast-fungus, and _Bacillus lacticus_. Kefir is a
somewhat alcoholic sour milk, rich in carbonic acid; it is a beverage
manufactured by the inhabitants of the Caucasus, from the milk of cows,
goats, or sheep, and is sometimes used as a medicine. In the production
of kefir, lactic acid fermentation takes place in one part of the sugar
contained in the milk, and alcoholic fermentation in another part, and
the casein which had become curdled is partially liquefied (peptonised)
by an enzyme of a Zooglœa-bacterium.

_Bacillus amylobacter_ (_Bacillus butyricus_), the
Butyric-acid-bacterium (Fig. 29), is a very common anaerobic which
produces fermentation in sugar and lactic-acid salts, and whose
principal product is _butyric acid_. It destroys articles of
food and (together with other species) plays a part in the butyric
acid fermentation which is necessary in the making of cheese; it is
very active wherever portions of plants are decaying, in destroying
the cellulose in the cell-walls of herbaceous plants, and is thus
useful in the preparation of flax and hemp. The cells are self-motile,
generally cylindrical, sometimes united into short rows; endosporous;
the spore-forming cells swell, assume very different forms, and show
granulose reaction. The germ-tube grows out in the direction of the
long axis of the spore.

_Bacillus subtilis_, the Hay-bacillus, is developed in all decoctions
of hay; a slender, aerobic, self-motile Bacillus; endosporous
(aplanospores); the spore-wall ruptures transversely on germination.

_Crenothrix kuehniana_ occurs in the springs of many baths, in wells, in
water or drain-pipes.

  [Illustration: FIG. 31.--_Beggiatoa alba_: _a_ from a fluid
  containing abundance of sulphuretted hydrogen; _b_ after lying 24
  hours in a solution devoid of sulphuretted hydrogen; _c_ after
  lying an additional 48 hours in a solution devoid of sulphuretted
  hydrogen, by this means the transverse walls and vacuoles have
  become visible.]

_Beggiatoa_ (parallel with the Blue-green Alga _Oscillaria_). Long
filaments formed of cylindrical cells which are attached by one
of the ends, but which are nearly always free when observed. The
filaments, like those of _Oscillaria_, describe conical figures in
their revolutions, the free filaments slide upwards and parallel with
one another; sheaths are wanting; strongly refractive sulphur drops
are found in the interior. The Beggiatoas are the most prevalent
_Sulphur-bacteria_. They occur, very commonly in large numbers,
wherever plant or animal remains are decaying in water in which
sulphuretted hydrogen is being formed; thus, for example, _B. alba_
(Fig. 31) occurs frequently as a white covering or slimy film on mud
containing organic remains. ~_B. mirabilis_ is remarkable for its
size and its strong peristaltic movements.~ The Sulphur-bacteria
oxidize the sulphuretted hydrogen, and accumulate sulphur in the
shape of small granules of soft amorphic sulphur, which in the living
cell never passes over into the crystalline state. They next oxidize
this sulphur into sulphuric acid, which is immediately rendered
neutral by absorbed salts of calcium, and is given off in the form
of a sulphate, thus CaCO_{3} is principally changed into CaSO_{4}.
In the absence of sulphur the nutritive processes are suspended, and
consequently death occurs either sooner or later. The Sulphur-bacteria
may exist and multiply in a fluid which only contains traces of
organic matter, in which organisms devoid of chlorophyll are not able
to exist. The Beggiatoas very frequently form white, bulky masses
in sulphur wells and in salt water, the traces of organic material
which the sulphur water contains proving sufficient for them. ~The
cellulose-fermentation, to which the sulphur wells in all probability
owe their origin, mainly procures them suitable conditions for
existence. The CaCO_{3} and H_{2}S, formed during the cellulose
fermentation by the reduction of CaSO_{4} is again changed into
CaSO_{4} and CO_{2} by the Sulphur-bacteria (Winogradsky, 1887).--Other
Sulphur-bacteria, the so-called purple Sulphur-bacteria, _e.g._
_B. roseo-persicina_, _Spirillum sanguineum_ (Fig. 23), _Bacterium
sulfuratum_, etc., have their protoplasm mixed with a red colouring
matter (bacterio-purpurin) which, like chlorophyll, has the power,
in the presence of light, of giving off oxygen (as proved by T. W.
Englemann, 1888, in oxygen-sensitive Bacteria). The three purple
Sulphur-bacteria mentioned, are, according to Winogradsky, not
pleomorphic kinds but embrace numerous species.~

Many _Spirilli_ (_Spirillum tenue_, _S. undula_, _S. plicatile_, and
others) are found prevalent in decaying liquids.

Bacteria (especially Bacilli) are the cause of many substances emitting
a foul odour, and of various changes in milk.

=Parasitic Bacteria= live in other living organisms; but the relation
between “host” and parasite may vary in considerable degree. Some
parasites do no injury to their host, others produce dangerous
contagious diseases; some choose only a special kind as host, others
again live equally well in many different ones. There are further
specific and individual differences with regard to the _predisposition_
of the host, and every individual has not the same receptivity at all
times.

THE HARMLESS PARASITES OF HUMAN BEINGS. Several of the above mentioned
saprophytes may also occur in the alimentary canal of human beings;
_e.g._, the Hay-bacillus, the Butyric-acid-bacillus, etc.; but the
gastric juice prevents the development of others, at all events in
their vegetative condition. _Sarcina ventriculi_, “packet-bacterium,”
is only known to occur in the stomach and intestines of human beings,
and makes its appearance in certain diseases of the stomach (dilation
of the stomach, etc.) in great numbers, without, however, being the
cause of the disease. It occurs in somewhat cubical masses of roundish
cells (Fig. 25).

LESS DANGEROUS PARASITES. In the mouth, especially between and on
the teeth, a great many Bacteria are to be found (more than fifty
species are known), _e.g. Leptothrix buccalis_ (long, brittle,
very thin filaments which are united into bundles), Micrococci in
large lumps, _Spirochæte cohnii_, etc. Some of them are known to be
injurious, as they contribute in various ways to the decay of the
teeth (_caries dentium_); a _Micrococcus_, for instance, forms lactic
acid in materials containing sugar and starch, and the acid dissolves
the lime salts in the external layers of the teeth: those parts of
the teeth thus deprived of lime are attacked by other Bacteria, and
become dissolved. Inflammation in the tissues at the root of a tooth,
is probably produced by septic materials which have been formed by
Bacteria in the root-canal.

DANGEROUS PARASITES. In a large number of the infectious diseases of
human beings and animals, it has been possible to prove that parasitic
Bacteria have been the cause of the disease. Various pathogenic
Bacteria of this nature, belonging to the coccus, rod, and spiral
Bacteria groups, are mentioned in the following:--

=Pathogenic Micrococci.= _Staphylococcus pyogenes aureus_ produces
abscesses of various natures (boils, suppurative processes in internal
organs). The same effects are produced by--

_Streptococcus pyogenes_, which is the most frequent cause of malignant
puerperal fever; it is perhaps identical with--

_Streptococcus erysipelatis_, which is the cause of erysipelas in human
beings.

_Diplococcus pneumoniæ_ (A. Fränkel) is the cause of pneumonia, and of
the epidemic cerebro-spinal meningitis.

_Gonococcus_ (Neisser) is the cause of gonorrhea and inflammation of
the eyes.

=Pathogenic Rod-Bacteria.= _Bacterium choleræ gallinarum_, an aerobic,
facultative parasite which produces fowl-cholera among poultry; it is
easily cultivated on various substrata as a saprophyte. The disease
may be conveyed both through wounds and by food, and may also be
communicated to mammals.

_Bacillus anthracis_, the _Anthrax bacillus_ (Fig. 32), chiefly attacks
mammals, especially herbivorous animals (house mice, guinea-pigs,
rabbits, sheep, cattle), in a less degree omnivorous animals (including
human beings), and in a still less degree the Carnivores. Aerobic.
Cylindrical cells, 3–4 times as long as broad, united into long
rod-like bodies, which may elongate into long, bent, and twisted
filaments. Not self-motile. Endosporous. Germination takes place
without the throwing off of any spore-membrane (compare Hay-bacillus p.
37 which resembles it). Contagion may take place both by introduction
into wounds, and from the mucous membrane of the intestines or lungs,
both by vegetative cells and by spores; in intestinal anthrax, however,
only by spores. The Bacillus multiplies as soon as it has entered the
blood, and the anthrax disease commences. The Bacilli not only give off
poison, but also deprive the blood of its oxygen. Vegetative cells only
occur in living animals. This species is a _facultative parasite_ which
in the first stage is a saprophyte, and only in this condition forms
spores.

  [Illustration: FIG. 32.--_Anthrax bacillus_ (_Bacillus
  anthracis_) with red (_b_) and white (_a_) blood-corpuscles.]

  [Illustration: FIG. 33.--_Anthrax bacillus._ The formation of the
  spores; magnified 450 times.]

_Bacillus tuberculosis_ produces tuberculosis in human beings, also
in domestic animals (_perlsucht_). It is a distinct parasite, but may
also live saprophytically. It is rod-formed, often slightly bent, and
is recognised principally by its action with stains (when stained with
an alkaline solution of methyl-blue or carbolic fuchsin, it retains the
colour for a long time even in solutions of mineral acids, in contrast
with the majority of well-known Bacteria): it probably forms spores
which are able to resist heat, dryness, etc.

   _Bacillus lepræ_ produces leprosy; _Bacillus mallei_ produces
   glanders; _Bacillus tetani_, tetanus (the tetanus bacillus
   is very common in soil; anaerobic); _Bacillus diphtheriæ_,
   diphtheria; _Bacillus typhosus_, typhoid fever, etc.

=Pathogenic Spiral Bacteria.= _Spirochæte obermeieri_ (Fig. 24)
produces intermittent fever (febris recurrens); it makes its appearance
in the blood during the attacks of fever, but it is not to be found
during intervals when there is no fever. Obligate parasite.

_Spirillum choleræ asiaticæ_ (_Microspira comma_) without doubt
produces Asiatic cholera; an exceedingly motile spirillum, which is
also found in short, bent rods (known as the “Comma-bacillus”), it
lives in the intestines of those attacked by the disease, and gives off
a strong poison which enters the body. It is easily cultivated as a
saprophyte.

A great many circumstances seem to show that a number of other
infectious diseases (syphilis, small-pox, scarlet-fever, measles,
yellow-fever, etc.) owe their origin to parasitic Bacteria, but this
has not been proved with certainty in all cases.

It has been possible by means of special cultivations (ample supply of
oxygen, high temperature, antiseptic materials) to produce from the
parasitic Bacteria described above (_e.g._ the fowl-cholera and the
anthrax Bacteria) _physiological varieties_ which are distinct from
those appearing in nature and possess a less degree of “virulence,”
_i.e._ produce fever and less dangerous symptoms in those animals
which are inoculated with them. The production of such physiological
varieties has come to be of great practical importance from the fact
that they are used as vaccines, _i.e._ these harmless species produce
in the animals inoculated with them _immunity_ from the malignant
infectious Bacteria from which they were derived. This immunity is
effected by the change of the products of one or more of the Bacteria,
but we do not yet know anything about the way in which they act on
the animal organism. The white blood corpuscles, according to the
Metschnikoff, play the part of “Phagocytes” by absorbing and destroying
the less virulent Bacteria which have entered the blood, and by so
doing they are gradually enabled to overcome those of a more virulent
nature.

  [Illustration: FIG. 34.--_a_ and _b_ The same blood-cell of a
  Frog: _a_ in the act of engulfing an anthrax-bacillus; _b_ after
  an interval of a few minutes when the bacillus has been absorbed.]


                         Class 5. =Conjugatæ.=

The Algæ belonging to this class have chlorophyll, and pyrenoids
round which starch is formed. The cells divide only in one direction,
they live solitarily, or united to form filaments which generally
float freely (seldom attached). Swarm-cells are wanting. _The
fertilisation is isogamous (conjugation) and takes place by means
of aplanogametes._ The zygote, after a period of rest, produces,
immediately on germination, one or more new vegetative individuals;
sometimes akinetes or aplanospores are formed in addition. They only
occur in fresh or slightly brackish water.

Order 1. =Desmidiaceæ.= The cells generally present markings on the
outer wall, and are mostly divided into two symmetrical halves by a
constriction in the middle, or there is at least a symmetrical division
of the protoplasmic cell-contents. The cell-wall consists nearly
always of two layers, the one overlapping the other (Fig. 35 _C_). The
cells either live solitarily or are united into unbranched filaments.
The mass of protoplasm formed by the fusion of the two conjugating
cells becomes the zygote, which on germination produces one (or after
division 2, 4 or 8) new vegetative individual. The chromatophores are
either star-, plate-, or band-shaped, and regularly arranged round the
long axis of the cell.

  [Illustration: FIG. 35.--A Cell of _Gymnozyga brebissonii_,
  external view showing the distribution of the pores. _B A_
  portion of the membrane of _Staurastrum bicorne_ with pores
  containing protoplasmic projections. _C_ Cell-wall of _Hyalotheca
  mucosa_ during cell-division: the central part, being already
  formed, shows the connection with the divisional wall.]

The Desmidiaceæ are not able to swim independently, many species,
however, show movements of different kinds by rising and sliding
forward on the substratum. These movements, which are partly dependent
upon, and partly independent of light and the force of gravitation, are
connected with the protrusion of a mucilaginous stalk. The mucilage,
which sometimes surrounds the whole individual, may acquire a prismatic
structure, it is secreted by the protoplasmic threads which project
through certain pores definitely situated in the walls (Fig. 35
_A_, _B_).

VEGETATIVE MULTIPLICATION takes places by division. A good example of
this is found in _Cosmarium botrytis_ (Fig. 36 _A-D_). The nucleus
and chromatophores divide, and simultaneously the central indentation
becomes deeper, the outer wall is then ruptured making a circular
aperture through which the inner wall protrudes forming a short,
cylindrical canal between the two halves to which it is attached (Fig.
36 _C_). After elongation the canal is divided by a central transverse
wall, which commences as a ring round its inner surface and gradually
forms a complete septum. The dividing wall gradually splits, and the
two individuals separate from each other, each one having an old and
a new half. The two daughter-cells bulge out, receive a supply of
contents from the parent-cells, and gradually attain their mature size
and development (Fig. 36 _B-D_). Exceptions to this occur in some forms.

  [Illustration: FIG. 36.--_Cosmarium botrytis. A-D_ Different
  stages of cell-division.]

  [Illustration: FIG. 37.--_Cosmarium meneghinii_: _a-c_ same
  individual seen from the side, from the end, and from the edge;
  _d-f_ stages of conjugation; _g-i_ germination of the zygote.]

CONJUGATION takes place in the simplest way in _Mesotænium_, where
the two conjugating cells unite by a short tube (conjugation-canal),
which is not developed at any particular point. The aplanogametes
merge together after the dissolution of the dividing wall, like two
drops of water, almost without any trace of preceding contraction, so
that the cell-wall of the zygote generally lies in close contact with
the conjugating cells. The conjugating cells in the others lie either
transversely (_e.g. Cosmarium_, Fig. 37 _d_; _Staurastrum_, etc.),
or parallel to one another (_e.g. Penium_, _Closterium_, etc.), and
emit a short conjugation-canal (Fig. 37 _d_) from the centre of that
side of each cell which is turned towards the other one. These canals
touch, become spherical, and on the absorption of the dividing wall
the aplanogametes coalesce in the swollen conjugation-canal (Fig.
37 _e_), which is often surrounded by a mucilaginous envelope. The
zygote, which is often spherical, is surrounded by a thick cell-wall,
consisting of three layers; the outermost of these sometimes bears
thorn-like projections, which in some species are simple (Fig. 37
_f_), in others branched or variously marked; in some, however, it
remains always smooth (_e.g._ _Tetmemorus_, _Desmidium_). Deviation
from this mode of conjugation may occur within certain genera (_e.g._
_Closterium_, _Penium_). Upon germination the contents of the zygote
emerge, surrounded by the innermost layers of the wall (Fig. 37 _g_,
_h_) and generally divide into two parts which develop into two new
individuals, placed transversely to each other (Fig. 37 _i_); these may
have a somewhat more simple marking than is generally possessed by the
species.

  [Illustration: FIG. 38.--Desmidiaceæ. _A Closterium
  moniliferum_; _B Penium crassiusculum_; _C Micrasterias
  truncata_ (front and end view); _D Euastrum elegans_; _E_
  _Staurastrum muticum_ (end view).]

   The most frequent genera are:--

   _A._ Solitary cells: MESOTÆNIUM, PENIUM (Fig. 38 _B_),
   CYLINDROCYSTIS, EUASTRUM (Fig. 38 _D_), MICRASTERIAS (Fig. 38
   _C_), COSMARIUM (Fig. 36, 37), XANTHIDIUM, STAURASTRUM (Fig. 38
   _E_), PLEUROTÆNIUM, DOCIDIUM, TETMEMORUS, CLOSTERIUM (Fig. 38
   _A_), SPIROTÆNIA.

   _B._ Cells united into filaments: SPHÆROZOSMA, DESMIDIUM,
   HYALOTHECA, GYMNOZYGA, ANCYLONEMA, GONATOZYGON.

Order 2. =Zygnemaceæ.= Cell-wall without markings. The cells are
cylindrical, not constricted in the centre, and (generally) united into
simple, unbranched filaments. The whole contents of the conjugating
cells take part in the formation of the zygote, which on germination
grows out directly into a new filament.

_Spirogyra_ is easily recognised by its spiral chlorophyll band;
_Zygnema_ has two star-like chromatophores in each cell (Fig. 40);
both these genera are very common Algæ in ponds and ditches.

  [Illustration: FIG. 39.--_Spirogyra longata. A_ At the
  commencement of conjugation, the conjugation-canals begin
  to protrude at _a_ and touch one another at _b_; the spiral
  chlorophyll band and cell-nuclei (_k_) are shown. _B_ A more
  advanced stage of conjugation; _a_, _a’_ the rounded female and
  male aplanogametes: in _b’_ the male aplanogamete is going over
  to and uniting with the female aplanogamete (_b_).]

  [Illustration: FIG. 40.--A cell of _Zygnema_. _S_ Pyrenoid.]

  [Illustration: FIG. 41.--_Zygnema insigne_, with zygote.]

  [Illustration: FIG. 42.--Germinating zygote of _Spirogyra
  jugalis_: the young plant is still unicellular; the end which is
  still in the wall of the zygote is elongated and root-like; the
  chromatophore divides and forms the spiral band.]

The conjugation among the Zygnemaceæ takes place in the following
manner: the cells of two filaments, lying side by side, or two cells,
the one being situated above the other in the same filament (Fig. 41),
push out small protuberances opposite each other (Fig. 39 _A_, _a_,
_b_); these finally meet, and the dividing wall is absorbed so that a
tube is formed connecting one cell with the other; the protoplasmic
contents round off, and the whole of these contents of one of the
cells glides through the conjugation-tube and coalesces with that of
the other (Fig. 39 _B_), the aggregate mass then rounds off, surrounds
itself with a cell-wall, and becomes a zygote. A distinct difference
may be found between the cells in the two filaments, those in the one
whose protoplasmic contents pass over being cylindrical, while those
of the recipient one are more barrel-shaped, and of a larger diameter.
The former may be regarded as a male, the latter as a female plant.
The zygote germinates after a period of rest, and grows out into a new
filament (Fig. 42).

Order 3. =Mesocarpaceæ.= The cell-walls are glabrous, unconstricted
in the centre, and united into simple unbranched filaments. The
chromatophore consists of an axial chlorophyll-plate, with several
pyrenoids. The zygote is formed by the coalescence of two cells (Fig.
43) (sometimes three or four), but the whole protoplasmic contents of
the cells do not take part in this process, a portion always remaining
behind; the aplanogametes coalesce in the conjugation-canal. The
zygote thus formed appears incapable of germination until after 3–5
divisions. Of the cells so formed, only one is fertile, the sterile
cells, according to Pringsheim, constituting a rudimentary sporocarp.
The germinating cells grow out into a new filament. In this order,
conjugation has been observed between two cells of the same filament.
The Mesocarpaceæ thrive best in water which contains lime.

  [Illustration: FIG. 43.--Mougeotia calcarea. Cells showing
  various modes of conjugation: at _m_ tripartition; _pg_
  quadripartition; _s_ quinquipartilion of the zygote.]


                 Class 6. =Chlorophyceæ (Green Algæ).=

These Algæ are coloured green by chlorophyll, seldom in combination
with other colouring matter, and then especially with red. The product
of assimilation is frequently starch, which generally accumulates round
certain specially formed portions of protoplasm termed pyrenoids.
The thallus is uni- or multicellular; in the higher forms (certain
Siphoneæ) the organs of vegetation attain differentiation into stem
and leaf. The asexual reproduction takes place in various ways; the
sexual reproduction is effected by conjugation of motile gametes, or
by oogamous fertilisation. The swarm-cells (zoospores, gametes, and
spermatozoids) are constructed symetrically, and have true protoplasmic
cilia, these generally being attached to the front end of the
swarm-cells. Most of these Algæ live in water (fresh or salt); some are
found upon damp soil, stones, or tree-stems, and some live enclosed in
other plants.

The Class is divided into three families:--

1. PROTOCOCCOIDEÆ: Volvocaceæ, Tetrasporaceæ, Chlorosphæraceæ,
Pleurococcaceæ, Protococcaceæ, Hydrodictyaceæ.

2. CONFERVOIDEÆ: Ulvaceæ, Ulothricaceæ, Chætophoraceæ, Mycoideaceæ,
Cylindrocapsaceæ, Œdogoniaceæ, Coleochætaceæ, Cladophoraceæ,
Gomontiaceæ, Sphæropleaceæ.

3. SIPHONEÆ: Botrydiaceæ, Bryopsidaceæ, Derbesiaceæ, Vaucheriaceæ,
Phyllosiphonaceæ, Caulerpaceæ, Codiaceæ, Valoniaceæ, Dasycladaceæ.


                      Family 1. =Protococcoideæ.=

The Algæ which belong to this group are uni- or multicellular with
the cells more or less firmly connected, sometimes in a definite,
sometimes in an indefinite form (Fig. 47). Colonies are formed either
by division or by small unicellular individuals becoming united in a
definite manner; the colonies formed in this latter way are termed
_Cœnobia_. Apical cells and branching are absent. Multiplication
by division; asexual reproduction by zoospores, rarely by akinetes.
Sexual reproduction may be wanting, or it takes place by isogamous,
rarely by oogamous fertilisation.

Some are attached by means of a stalk to other objects (_Characium_,
Fig. 49), others occur as “Endophytes” in the tissues of certain Mosses
or Phanerogams, _e.g. Chlorochytrium lemnæ_, in _Lemna trisulca_;
_Endosphæra_, in the leaves of _Potamogeton_, _Mentha aquatica_,
and _Peplis portula_; _Phyllobium_, in the leaves of _Lysimachia
nummularia_, _Ajuga_, _Chlora_, and species of Grasses; _Scotinosphæra_
in the leaves of _Hypnum_ and _Lemna trisulca_; the majority, however,
live free in water and in damp places. Many species which were formerly
considered to belong to this family have been proved to be higher Algæ
in stages of development.

Order 1. =Volvocaceæ.= The individuals in this order are either
uni- or multicellular, and during the essential part of their life are
free-swimming organisms. They are generally encased in a mucilaginous
envelope, through which 2–6 cilia project from every cell. The
vegetative reproduction takes place by the division of all, or a few,
of the cells of the individual; in some a palmella-stage is found in
addition. The sexual reproduction takes place by isogamous or oogamous
fertilisation.

   The Volvocaceæ may be considered to include the original forms
   of the Chlorophyceæ, because, among other reasons, the motile
   stage is here the most prominent; they also form the connecting
   link between the animal Flagellata, and forms intermediate to
   the _Syngeneticæ_ may perhaps be found amongst them. Three
   series of green Algæ may be supposed to have taken their origin
   from the Volvocaceæ: CONJUGATEÆ (_Desmidiaceæ_) which have lost
   the swarming stage, but whose conjugation is the nearest to the
   fertilisation in _Chlamydomonas pulvisculus_: the PROTOCOCCACEÆ
   in which the vegetative divisions have disappeared, while the
   swarming stage continues to be present, though of shorter
   duration; and TETRASPORACEÆ, in which the vegetative divisions
   are more prominent, whilst the swarming stage is less so.

A. UNICELLULAR INDIVIDUALS. The principle genera are: _Chlamydomonas_,
_Sphærella_, _Phacotus_.--_Sphærella nivalis_ is the Alga which
produces the phenomenon of “Red Snow,” well known on high mountains and
on ice and snow fields in the polar regions. The red colouring matter
which appears in this and other green Algæ, especially in the resting
cells, is produced by the alteration of the chlorophyll.

_Phacotus lenticularis_ has an outer covering incrusted with lime,
which, at death, or after division, opens out into two halves.
Species may be found among _Chlamydomonas_, in which conjugation
takes place between gametes of similar size without cell-wall, but
in _C. pulvisculus_ conjugation takes place between male and female
aplanogametes which are surrounded by a mucilaginous envelope.

  [Illustration: FIG. 44--_Gonium pectorale._]

  [Illustration: FIG. 45.--_Pandorina morum._]

B. MULTICELLULAR INDIVIDUALS. The most important genera are _Gonium_,
_Stephanosphæra_, _Pandorina_, _Eudorina_, _Volvox_.--_Gonium_ has 4
or 16 cells arranged in a definite pattern in a flat plate (Fig. 44).
_Pandorina_ (Fig. 45), has 16 cells arranged in a sphere (Fig. 45 _A_).
The vegetative reproduction takes place in this way: each cell, after
having rounded off, and after the withdrawal of the cilia, divides
itself into 16 new ones (Fig. 45 _B_), each forming a new individual,
which soon grows to the size of the mother-individual. It was in this
Alga that the conjugation of self-motile gametes was first discovered
by Pringsheim, 1869. When conjugation is about to take place, each
cell divides into sixteen, as in vegetative reproduction, but the 16
× 16 cells all separate from one another (Fig. 45 _C_, female gametes,
and _D_, male gametes), and swarm solitarily in the water. The male
are, most frequently, smaller than the female, but otherwise they are
exactly alike; they are more or less pear-shaped, with a colourless
anterior end, 2 cilia, a red “eye-spot,” etc. After swarming for some
time they approach each other, two and two, generally a large and a
smaller one, and come into contact at their colourless end; in a few
moments they coalesce and become one cell (Fig. 45 _E_, _F_), this has
at first a large colourless anterior end, 4 cilia, and 2 “eye-spots”
(Fig. 45 _G_), but these soon disappear and the cell becomes uniformly
dark-green and spherical, and surrounds itself with a thick cell-wall,
losing at the same time its power of motion: the zygote (Fig. 45 _H_)
is formed, and becomes later on a deep red colour. On the germination
of the zygote, the protoplasmic cell-contents burst open the wall (Fig.
45 _J_), and emerge as a large swarmspore (Fig. 45 _K_) which divides
into 16 cells, and the first small individual is formed (Fig. 45 _L_,
_M_).

_Eudorina_ is like _Pandorina_ in structure, but stands somewhat
higher, since the contrast between the conjugating sexual cells is
greater, the female one being a motionless oosphere.

  [Illustration: FIG. 46.--_Volvox globator_, sexual individual:
  _a_ antheridia which have formed spermatozoids; _b_ oogonia.]

The highest stage of development is found in _Volvox_ (Fig. 46). The
cells are here arranged on the circumference of a sphere, and enclose
a cavity filled with mucilage. The number of these cells may vary from
200–22,000, of which the majority are vegetative and not reproductive,
but some become large, motionless oospheres (Fig. 46 _b_); others,
which may appear as solitary individuals, divide and form disc-shaped
masses of from 8–256 small spermatozoids (Fig. 46 _a_). After the
oosphere has been fertilised by these, the oospore surrounds itself by
a thick, sometimes thorny cell-wall, and on germination becomes a new
individual of few cells. A few cells conspicuous by their larger size
may be found (1–9, but generally 8) in certain individuals, and these
provide the vegetative reproduction, each forming by division a new
individual.

Order 2. =Tetrasporaceæ= reproduce both by vegetative divisions and
swarmspores, some have also gamete-conjugation. The principal genera
are: _Tetraspora_, _Apiocystis_, _Dactylococcus_, _Dictyosphærium_,
_Chlorangium_.

Order 3. =Chlorosphæraceæ.= _Chlorosphæra._

Order 4. =Pleurococcaceæ.= In this order the swarm-stages and sexual
reproduction are entirely absent. Vegetative reproduction by division.
The principal genera are: _Pleurococcus_ (Fig. 47), _Scenedesmus_
(Fig. 48), _Raphidium_, _Oocystis_, _Schizochlamys_, _Crucigenia_,
_Selenastrum_.--_Pleurococcus vulgaris_ (Fig. 47) is one of the
most common Algæ throughout the world, occurring as green coverings
on tree-stems, and damp walls, and it is one of the most common
lichen-gonidia.

  [Illustration: FIG. 47.--_Pleurococcus vulgaris._]

  [Illustration: FIG. 48.--_Scenedesmus quadricauda._]

Order 5. =Protococcaceæ.= The cells are motionless, free or affixed
on a stalk (_e.g. Characium_, Fig. 49), either separate or loosely
bound to one another; they never form multicellular individuals.
Multiplication by division is nearly always wanting. Reproduction
takes place by swarmspores, which have 1 or 2 cilia, and sexual
reproduction in some by gamete-conjugation. The principal genera are:
_Chlorococcum_, _Chlorochytrium_, _Chlorocystis_, _Scotinosphæra_,
_Endosphæra_, _Phyllobium_, _Characium_, _Ophiocytium_, _Sciadium_.

  [Illustration: FIG. 49.--_Characium strictum._
  _A_ The cell-contents have divided into many swarmspores.
  _B_ Swarmspores escaping.]

Order 6. =Hydrodictyaceæ.= The individuals are unicellular but
several unite after the zoospore-stage into definitely formed families
(cœnobia). Ordinary vegetative division is wanting, but asexual
reproduction takes place by zoospores (or by motionless cells without
cilia), which unite and form a family similar to the mother-family,
inside the mother-cell, or in a mucilaginous envelope. Where sexual
reproduction is found it takes place by gamete-conjugation. The
principal genera are: _Pediastrum_ (Fig. 50), _Cœlastrum_,
_Hydrodictyon_ (Fig. 51).

  [Illustration: FIG. 5O.--_Pediastrum asperum._]

  [Illustration: FIG. 51.--_Hydrodictyou reticulatum. A_ A cell
  where the zoospores are on the point of arranging themselves to
  form a net. _B_ A cell with gametes swarming out.]

The cœnobium of _Hydrodictyon reticulatum_ (Water-net) is formed of
a large number of cells which are cylindrical, and attached to one
another by the ends (Fig. 51). The asexual reproduction takes place by
zoospores, which are formed in large numbers (7,000–20,000) in each
mother-cell, within which they move about for a time, and then come
to rest and arrange themselves into a new net (Fig. 51 _A_) which is
set free by the dissolution of the wall of the mother-cell, grows,
and becomes a new cœnobium. The sexual reproduction takes place by
gamete-conjugation. The gametes are formed in the same manner as the
zoospores, but in larger numbers (30,000–100,000), and swarm out of the
mother-cell (Fig. 51 _B_). The zygote forms, on germination, 2–5 large
zoospores, each with one or two cilia, these generally swarm about
for a time, and after a period of rest become irregular thorny bodies
(polyhedra); their contents again divide into zoospores, the thorny
external coating of the polyhedra is cast off, and the zoospores,
surrounded by the dilated internal coating, unite to form a small
family, which produces several others in the manner described.


                       Family 2. =Confervoideæ.=

The individuals are always multicellular, the cells firmly bound
together and united into unbranched or branched filaments, expansions,
or masses of cells which grow by intercallary divisions or have
apical growth. In the first seven orders the cells are uninuclear,
but the cells of the remaining three orders contain several nuclei.
Asexual reproduction by zoospores, akinetes or aplanospores. Sexual
reproduction by isogamous or oogamous fertilisation.

   The Confervoideæ, through the Ulvaceæ, are connected with the
   Tetrasporaceæ, and from the _Coleochætaceæ_, which is the most
   highly developed order, there are the best reasons for supposing
   that the Mosses have taken their origin. The _Cladophoraceæ_
   show the nearest approach to the _Siphoneæ_.

Order 1. =Ulvaceæ.= The thallus consists of one or two layers of
parenchymatous cells, connected together to form either a flat membrane
(_Monostroma_, _Ulva_) or a hollow tube (_Enteromorpha_), and may be
either simple, lobed, or branched. Reproduction takes place by detached
portions of the thallus; or asexually by zoospores or akinetes.
Gamete-conjugation is known to take place in some members of this
order, the zygote germinating without any resting-stage. The majority
are found in salt or brackish water.

  [Illustration: FIG. 52.--_Ulothrix zonata_: a portion of a
  filament with zoospores, which are formed two in each cell
  (zoosporangium); the dark spots are the red “eye-spots”; 1,
  2, 3, 4, denote successive stages in the development of the
  zoospores; _b_ a single zoospore, _v_ the pulsating vacuole;
  _c_ portion of a filament with gametes, sixteen are produced in
  each gametangium; _d_ free gametes, solitary or in the act of
  conjugation; _e_ the conjugation is completed, and the formed
  zygote has assumed the resting-stage.]

Order 2. =Ulothricaceæ.= The thallus consists normally of a simple
unbranched filament (sometimes a small expansion consisting of one
layer of cells is formed, as in _Schizomeris_ and _Prasiola_ which
were formerly described as separate genera). Asexual reproduction
takes place by means of zoospores (with 1, 2, or 4 cilia), akinetes
or aplanospores; the last named may germinate immediately, or only
after a period of rest. Sexual reproduction takes place by the
conjugation of gametes of about the same size, each having two cilia
(Fig. 52 _d_). The zygote of _Ulothrix_, on germination, produces a
brood of zoospores which swarm for a time and then elongate to become
_Ulothrix_-filaments (alternation of generations). The gametes may also
germinate without conjugation in the same manner as the zoospores.
The principal genera are: _Ulothrix_, _Hormidium_, _Conferva_,
_Microspora_.--_Ulothrix zonata_ is very common in running fresh water.
Nearly all the species of _Hormidium_ occur on damp soil, tree-stems
and stones.

Order 3. =Chætophoraceæ.= The thallus consists of a single, branched,
erect or creeping filament of cells, often surrounded by mucilage.
The cells have only one nucleus. Asexual reproduction by zoospores
with 2 or 4 cilia, by akinetes, or aplanospores. In many, conjugation
between gametes with 2 cilia may be found. They approach on one side,
Ulothricaceæ, and on the other, Mycoideaceæ. The principal genera
are: _Stigeoclonium_, _Draparnaldia_, _Chætophora_, _Entoderma_,
_Aphanochæte_, _Herposteiron_, _Phæothamnion_, _Chlorotylium_,
_Trichophilus_, _Gongrosira_, _Trentepohlia_. Most of the species of
_Trentepohlia_ are coloured red by the presence of a red colouring
material, which occurs in addition to the chlorophyll. They are aerial
Algæ which live on stones (_T. jolithus_, “violet stone,” so named
on account of its violet-like odour in rainy weather), on bark and
old wood (_T. umbrina_), or on damp rocks (_T. aurea_). _Trichophilus
welckeri_ lives in the hair of Bradypus.

Order 4. =Mycoideaceæ.= The thallus is discoid, consisting of one or
more cell-layers, and is always attached. Asexual reproduction by
zoospores with 2 or 4 cilia. Sexual reproduction in some species by the
conjugation of gametes with 2 cilia. This order forms the connecting
link between _Chætophoraceæ_ and _Coleochætaceæ_. The species occur in
fresh water (_Chætopeltis_) as well as in salt (_Pringsheimia_), on the
carapace of tortoises (_Dermatophyton_ = _Epiclemmydia_), or endophytic
between the cuticle and the epidermal cells of the leaves of tropical
plants, destroying the leaf-tissue (_Mycoidea_).

Order 5. =Cylindrocapsaceæ.= The thallus consists of a simple (rarely,
in parts, formed of many rows) unbranched filament, attached in the
young condition, which has short cells with a single nucleus, and is
enveloped in a thick envelope with a laminated structure. Asexual
reproduction by zoospores with 2 cilia, which are formed 1, 2, or 4 in
each vegetative cell. The antheridia are produced by a single cell,
or a group of cells, in a filament, dividing several times without
increasing in size. Two egg-shaped spermatozoids, each with 2 cilia
(Fig. 53 _D_), are formed in each antheridium, and escape through
an aperture in the side; in the first stages they are enclosed in a
bladder-like membrane (Fig. 53 _B_, _C_). Other cells of the filament
swell out and form oogonia (Fig. 53 _A_), which resemble those of
_Œdogonium_. After fertilisation, the oospore surrounds itself with a
thick wall, and assumes a reddish colour. The germination is unknown.
The unfertilised oospheres remain green, divide often into 2–4
daughter-cells, and grow into new filaments.

  [Illustration: FIG. 53.--_Cylindrocopsa involuta. A_ Oogonium
  with oosphere (_o_) surrounded by spermatozoids (_s_). _B_ Two
  antheridia, each with two spermatozoids. _C_ Spermatozoids
  surrounded by their bladder-like membrane. _D_ Free spermatozoid.]

This order, which only includes one genus, _Cylindrocapsa_, forms the
connecting link between _Ulothricaceæ_ and _Œdogoniaceæ_. The few
species (4) occur only in fresh water.

Order 6. =Œdogoniaceæ.= The thallus consists of branched (_Bulbochæte_)
or unbranched (_Œdogonium_) filaments, attached in the early stages.
The cells may be longer or shorter, and have one nucleus. Asexual
reproduction by zoospores, which have a chaplet of cilia round the base
of the colourless end (Fig. 6 _a_). Sexual reproduction takes place by
oogamous fertilisation. On the germination of the oospore, 4 zoospores
are formed (Fig. 54 _F_). They occur only in fresh or slightly brackish
water. The division of the cells takes place in quite a peculiar and
unusual manner. At the upper end of the cell which is about to divide,
a ring-shaped thickening of soft cellulose is formed transversely round
the wall; the cell-nucleus of the mother-cell and the protoplasm then
divide by a transverse wall into two portions of similar size, and the
cell-wall bursts transversely along the central line of the thickened
ring. The cell-wall thus divides into two parts--the upper one short,
the “cap,” and the lower one much longer, the “sheath.” The portions
of the original cell-wall now separate from each other, the cellulose
ring extending, and supplying an additional length of cell-wall between
them. The cap and sheath will project a little in front of the piece
thus inserted. The dividing wall between the two new cells is formed
near to the uppermost edge of the sheath, and gradually becomes thicker
and firmer. The inserted piece of wall forms the larger part of the
wall of the upper cell: the remainder is formed by the cap. This mode
of division is repeated exactly in the same way, and new caps are
formed close below the first one, one for every division.

   [Illustration: FIG. 54.--_A Œdogonium ciliatum. A_ Female
  plant with three oogonia (_og_) and dwarf-males (_m_). _B_ An
  oogonium with spermatozoid (_z_) seen entering the oosphere
  (_o_) having passed through an aperture near the summit of the
  oogonium; _m_ dwarf-male. _C_ Ripe oospore. _D Œdogonium
  gemelliparum. F_ Portion of a male filament from which
  spermatozoids (_z_) are emerging. _E_ Portion of filament of
  _Bulbochæte_; the upper oogonium still encloses the oospore, in
  the central one the oospore is escaping while the lower one is
  empty. _F_ Four zoospores developed from an oospore. _G_ Zoospore
  germinating.]

Fertilisation takes place in the following way. The oogonium is a
large ellipsoidal, swollen cell (_og_, in Fig. 54 _A_), whose contents
are rounded off into an oosphere with a colourless receptive-spot
(see _B_); an aperture is formed in the wall of the oogonium, through
which the spermatozoids are enabled to enter (_B_). The spermatozoids
are produced either directly, as in _D_ (in pairs), in basal cells
of the filament, or indirectly. In the latter case a swarmspore
(_androspore_) is formed which comes to rest, attaches itself to an
oogonium, germinates, and gives rise to a filament of a very few
cells--_dwarf-male_ (_A_, _B_, _m_). The spermatozoids are formed in
the upper cell of the dwarf-male (_m_), and are set free by the summit
of the antheridium lifting off like a lid. On the germination of the
oospore (_C_), which takes place in the following spring, 4 zoospores
are produced (_F_) (_i.e._ the sexual generation); these swarm about
for a time, and ultimately grow into new filaments.

  [Illustration: FIG. 55.--_Coleochæte pulvinata. A_ A portion
  of a thallus with organs of reproduction; _a_ oogonium before,
  _b_ after fertilisation; _c_ an antheridium, closed; _d_ open,
  with emerging spermatozoid. _B_ Ripe oogonium, with envelope. _C_
  Germination of the oospore. _D_ Zoospore. _E_ Spermatozoid.]

Order 7. =Coleochætaceæ.= The thallus is always attached, and of a
disc- or cushion-shape, formed by the dichotomous branching of filaments
of cells united in a pseudo-parenchymatous manner. Each cell has only
one nucleus. Asexual reproduction by zoospores with 2 cilia (Fig. 55
_D_), which may arise in all the cells. Sexual reproduction by oogamous
fertilisation. The spermatozoids resemble the swarmspores, but are
smaller (_E_), and originate singly (in the species figured) in small
conical cells (_c_, _d_ in _A_). The oogonia are developed at the
extremities of certain branches: they are bottle-shaped cells with very
long and thin necks (_trichogyne_), open at the end (_a_ in _A_); at
the base of each oogonium is a spherical oosphere. The spermatozoids
reach the oosphere through the trichogyne, or through an aperture in
the wall when the trichogyne is absent, and fertilisation having taken
place, the oogonium becomes surrounded by a cell-layer (envelope),
which grows out from the cells near its base (_b_ in _A_), and in this
way a kind of fruit is formed (_B_) (_spermocarp_, _cystocarp_).

The oospore, next spring, divides and forms a parenchymatous tissue
(homologous with the Moss-sporophyte); this bursts open the envelope
(_C_), and a zoospore (homologous with the spores of the Moss-capsule)
arises in each of the cells, and produces a new _Coleochæte_. We have
then, in this case, a still more distinct alternation of generations
than in _Œdogonium_. Only one genus, _Coleochæte_, is known, but it
contains several species, all living in fresh water.

Order 8. =Cladophoraceæ.= This order is probably derived from the
Ulothricaceæ. The thallus consists of a single, unbranched or branched
filament, generally with an apical cell. The cells have each 2 or more
nuclei. Asexual reproduction by zoospores with 2 or 4 cilia, and by
akinetes. Conjugation of gametes with 2 cilia is found in some genera.
They occur in salt as well as in fresh water. The principal genera are:
_Urospora_, _Chætomorpha_, _Rhizoclonium_, _Cladophora_; of the last
named genus the species _C. lanosa_ and _C. rupestris_ are common in
salt water; _C. fracta_ and _C. glomerata_ in fresh water.

Order 9. =Gomontiaceæ.= _Gomontia polyrrhiza_, the only species
hitherto known, is found on old calcareous shells of certain salt water
Molluscs.

Order 10. =Sphæropleaceæ.= The thallus consists of free, unbranched
filaments, with very elongated multinuclear cells. The vegetative
cells form no zoospores. Sexual reproduction by oogamous fertilisation
(see page 13, Fig. 10 _B_). The oospore has a thick wall (Fig. 10
_D_) studded with warts, and assumes a colour resembling red lead. It
germinates only in the following spring, and produces 1–8 zoospores,
each with 2 cilia (Fig. 10 _E_), which grow into new filaments. Only
one species, _Sphæroplea annulina_, is known.


                          Family 3. Siphoneæ.

The thallus has apical growth, and in the vegetative condition consists
generally of one single (in the Valoniaceæ most frequently of more)
multinuclear cell, which may be much branched, and whose separate parts
in the higher forms (_e.g. Bryopsis_, Fig. 57; _Caulerpa_, Fig.
59, etc.) may be differentiated to perform the various physiological
functions (as root, stem and leaf). Vegetative multiplication by
detached portions of the thallus (gemmæ); asexual reproduction
by zoospores, akinetes, or aplanospores. Sexual reproduction by
gamete-conjugation, rarely by oogamous fertilisation. The zygote or
oospore germinates as a rule without any resting-stage.

  [Illustration: FIG. 56.--_Botrydium granulatum_: _a_ an entire
  plant forming swarmspores; _b_ swamspores; _c_ an individual with
  gametangia; _d_, gamete; _e_, _f_, _g_ conjugation; _h_ zygote
  seen from above; _i_ the same in a lateral view.]

Most of the Siphoneæ occur in salt water or on damp soil. Many (_e.g._
_Dasycladaceæ_) are very much incrusted with lime, and occur, in the
fossilized condition, in the deposits from the Cretaceous period to
the present time. The Siphoneæ are connected by their lowest forms
(_Botrydiaceæ_ or _Valonia_) with the Protococcaceæ, but show also,
through the Valoniaceæ, points of relationship to the _Cladophoraceæ_.

Order 1. =Botrydiaceæ.= The thallus in the vegetative condition
is unicellular, club-shaped, with a small single (_Codiolum_) or
repeatedly dichotomously branched system of colourless rhizoids
(_Botrydium_, Fig. 56 _a_), by which it is attached to objects immersed
in salt water (_Codiolum_) or to damp clay soil (_Botrydium_). Asexual
reproduction by zoospores with one (_Botrydium_) or two cilia, and by
aplanospores. The sexual reproduction is only known in _Botrydium_, and
takes place in the following manner: in the part of the thallus which
is above ground and in an active vegetative condition, several round
cells (Fig. 56 _c_) are formed, which may be green or red according as
they grow under water, or exposed to the strong light of the sun. These
cells must be considered as “gametangia” as they produce many gametes
(_d_) provided with two cilia. The zygote (_h_, _i_) formed by the
conjugation (_e_, _f_, _g_) may either germinate immediately, or become
a thick-walled resting-cell of an irregular, angular form.

   Order 2. =Bryopsidaceæ.= The thallus in the vegetative condition
   is unicellular, and consists at the lower extremity of branched
   rhizoids, while the upper portion is prolonged into a stem-like
   structure of unlimited growth, producing, acropetally, branches
   and leaf-like structures. The latter have limited growth,
   and are separated by a cross wall from the stem, and become
   gametangia, or drop off. The gametes have two cilia, and are of
   two kinds: the female, which are green and large and the male,
   which are of brownish colour and smaller. Zoospores or any other
   method of asexual reproduction are unknown. Only one genus,
   _Bryopsis_, living in salt water.

  [Illustration: FIG. 57.--_Bryopsis plumosa_. A the plant, natural
  size. B A portion (enlarged) which shows the growing point (v),
  and the leaves derived from it in acropetal succession.]

   Order 3. =Derbesiaceæ.= Only one genus, _Derbesia_, living in
   saltwater. The zoospores, which are formed in a few lateral,
   swollen zoosporangia, possess one nucleus which has arisen
   through the coalescence of several, and they resemble the
   zoospores of _Œdogonium_ by having a circle of cilia attached at
   the base of the colourless spot.

Order 4. =Vaucheriaceæ.= The thallus consists, in the vegetative
condition, of a single irregularly or dichotomously branched cell,
without differentiation into stem or leaf; root-like organs of
attachment may however occur. Asexual reproduction by zoospores, which
are formed singly in the extremity of a branch cut off by a transverse
wall. They contain many nuclei, and bear small cilia situated in
pairs, which give the appearance of a fine “pile” covering the whole
or a great part of the surface. Akinetes, aplanospores, and phytoamœbæ
(naked masses of protoplasm, without cilia, which creep like an amœba
on a substratum) may occur under certain conditions.

The sexual reproductive organs are formed on short lateral branches,
and are separated from the vegetative cell (Fig. 58 _A_) by cell-walls.
Numerous spermatozoids, each with two cilia, are developed in the
coiled antheridium (_A_, _b_). The oogonium is a thick, egg-shaped,
often oblique cell, with its protoplasm rounded into an oosphere,
which has a hyaline “receptive-spot” (_A_, _a_) immediately beneath
the aperture formed in the wall of the oogonium. A slimy mass, which
serves to receive the spermatozoids, is formed in some species in this
aperture. The spermatozoids when liberated swim towards and enter
the oosphere, which then immediately surrounds itself with a thick
cell-wall. The mature oospore (_B_) contains a large quantity of oil.
At germination the outer cell-wall bursts and a new plant is formed.
There is only one genus, _Vaucheria_, with species living in salt as
well as in fresh water and on damp soil.

  [Illustration: FIG. 58.--_Vaucheria sessilis_. _A_ Fertilisation;
  _b_ the antheridia; _a_ the oogonia; _a_ the receptive spot. _B_
  Oospore.]

Order 5. =Phyllosiphonaceæ= are parasites in the leaves and stalks of
Flowering-plants.

Order 6. =Caulerpaceæ.= The thallus has distinct differentiation into
root, stem and leaf-like members (Fig. 59); it is unicellular. Within
the cell, strong, branched threads of cellulose extend from one side
to the other serving as stays to support the thallus. Reproduction
takes place by detached portions of the thallus; no other modes of
reproduction are known. This order may most approximately be classed
with the _Bryopsidaceæ_. The genus _Caulerpa_ consists of more than
seventy species which inhabit the tropical seas.

Order 7. =Codiaceæ.= The thallus has various forms, but without
distinct differentiation in stem- or leaf-structures, sometimes (_e.g._
_Halimeda_) it is very much incrusted with lime. In the early stages
it is unicellular (later, often multicellular), very much branched,
with the branches, at any rate partly, so united or grown in amongst
one another (Fig. 60) that an apparently parenchymatous cellular
body is formed. Akinetes or aplanospores are wanting; zoospores (or
gametes?) may be developed in some species, however, in special swollen
sporangia. Fertilisation similar to that in _Bryopsis_ occurs perhaps
in _Codium_. They are all salt water forms.

Order 8. =Valoniaceæ.= The thallus is generally multicellular, without
differentation into stem- or leaf-structures, but the cells are
sometimes united together and form a leaf-like reticulate expansion
(_e.g. Anadyomene_). Zoospores are known in some, and they are then
formed directly in the vegetative cells. In others (_e.g. Valonia_),
a mass of protoplasm, which maybe separated through the damaging of
a cell, can surround itself with a cell-wall, and grow into a new
plant. No other modes of reproduction are known. The most important
genera are: _Valonia_, _Siphonocladus_, _Chamædoris_, _Struvea_,
_Microdictyon_, _Anadyomene_. They are all salt water forms.

  [Illustration: FIG. 59.--_Caulerpa prolifera_ (natural size).]

   As already pointed out, the _Valoniaceæ_ occupy a somewhat
   central position among the Siphoneæ, and present points
   of similarity and contrast with the _Botrydiaceæ_ and the
   _Bryopsidaceæ_ through _Valonia_, with the _Dasycladaceæ_
   through _Chamædoris_, and also with the _Cladophoraceæ_ through
   _Siphonocladus_, and _Struvea_.

Order 9. =Dasycladaceæ.= The thallus consists of an axile longitudinal
cell, destitute of transverse walls, attached at the base by root-like
organs of attachment, and producing acropetally whorls of united,
single or branched, leaf-like structures with limited growth. Asexual
reproduction is wanting. Sexual reproduction by conjugation of gametes
which arise in separate, fertile leaves, either directly or from
aplanospores, which develope into gametangia. The principal genera are:
_Acetabularia_, _Dasycladus_, _Neomeris_, _Cymopolia_. All marine.

  [Illustration: FIG. 60.--_Halimeda opuntia._ Plant (natural
  size). _B_ Part of a longitudinal section.]

The curiously shaped _Acetabularia mediterranea_ grows gregariously
on limestone rocks, and shells of mussels in the Mediterranean; it
resembles a minute umbrella with a small stem, sometimes as much as
nine centimetres in height, and a shade which may be more than one
centimetre in diameter. The cell-membrane is thick, and incrusted
with carbonate and oxalate of lime. Only the lower, root-like part of
the thallus, which penetrates the calcareous substratum survives the
winter, and may grow up into a new plant. The sterile leaves, which
drop off early, are dichotomously branched and formed of cylindrical
cells separated from each other by cross-walls, but they are not grown
together. The shade is formed by a circle of 70–100 club-shaped rays
(fertile leaves) grown together, in each ray 40–80 aplanospores are
formed, which become liberated at the breaking of the shade, and later
on are changed to gametangia (compare _Botrydium_) which open by a
lid and allow a large number of egg-shaped gametes with two cilia to
escape. Gametes from various gametangia conjugate with one another; the
product of the conjugation swarms about for some time, rounds off, and
then surrounds itself with a cell-wall. The zygote germinates after
a period of rest and then produces a sexual plant. The aplanospores
(gametangia) thus represent the sexual generation.


                         Class 7. =Characeæ.=

The thallus has a stem with nodes and internodes; and whorls of leaves,
on which may be developed the antheridia and oogonia, are borne at
the nodes. Vegetative reproduction by bulbils and accessory shoots.
Zoospores are wanting. The antheridia are spherical, and contain a
number of filaments in which the spirally coiled spermatozoids, each
with two cilia, are formed. The oogonium is situated terminally, and
is at first naked, but becomes later on surrounded by an investment,
and forms after fertilisation the so-called “fruit.” The oospore, after
a period of rest, germinates by producing a “proembryo,” from which
the young sexual plant arises as a lateral branch. The Characeæ are
distinguished by the structure of their vegetative system as well as by
the spirally-coiled spermatozoids, and stand as an isolated group among
the Thallophytes, of which, however, the Siphoneæ appear to be their
nearest relations. They were formerly, but wrongly, placed near the
Mosses. The class contains only one order, the Characeæ.

Order 1. =Characeæ.= Algæ with a peculiar odour, often incrusted with
lime, and of a brittle nature. They generally grow gregariously in
large masses at the bottom of fresh and brackish water, and are from a
few inches to more than a foot in height. The stem has long internodes
which in _Nitella_ are formed of one cylindrical cell; in _Chara_ of
a similar cell, but closely surrounded by a cortical layer of smaller
ones. The protoplasm in contact with the cell-wall exhibits in a
well-marked degree the movement of rotation (cyclosis), carrying the
chlorophyll corpuscles along with it. The internodes are separated
from each other by a layer of small cells (nodal cells) from which the
leaves are produced. The leaves are borne in whorls of from 5–12 which
regularly alternate with one another as in the higher verticillate
plants; a branch is borne in the axil of the first formed leaf of each
whorl (Fig. 61 _A_, _n_).

  [Illustration: FIG. 61.--_Chara fragilis. A_ Portion of a
  plant, natural size. _B_ Portion of a leaf _b_, with leaflets
  β′-β′′; _a_ antheridium; _c_ oogonium. _C_ A shield.--_Nitella
  flexilis. D_ Filament from antheridium with spermatozoids. _E_
  Free spermatozoids.]

The leaves are constructed in the same manner as the stem; they are
divided into a series of joints, but have only a limited power of
growth; their terminal cell, too, is not enclosed by a cortex. Leaflets
are borne at their nodes. The growth of the stem is unlimited, and
proceeds by means of an apical cell (Fig. 62 _s_). The apical cell
divides into a segment-cell and a new apical cell. The segment-cell
then divides by a transverse wall into two cells, one lying above the
other; the lower one, without any further division, becomes one of the
long, cylindrical, internodal cells (Fig. 62 _in_), and the upper one
(Fig. 62 _n_) divides by vertical walls to form the nodal cells. The
cortical cells (Fig. 62 _r_) which surround the long internodal cells
of _Chara_, are derived from the divisions of the nodal cells; the
cells covering the upper portion of an internodal cell being derived
from the node immediately above it, and those in the lower part of the
internode from the node below it.

  [Illustration: FIG. 62.--_Chara fragilis_: _s_ apical cell; _n_,
  _n_ nodal cells; _in_ internodal cells; _bl_, _bl_ leaves; _r_,
  _r_ the cortical cells.]

  [Illustration: FIG. 63.--Oogonium of _Chara_: _k_ “crown”; _u_
  receptive spot; _s_ spermatozoids.]

The organs of reproduction are very conspicuous by their colour
and form. They are always situated on the leaves, the plants being
very frequently monœcious. The antheridia (Fig. 61 _B_, _a_) are
modified leaflets or the terminal cell of a leaf; they are spherical
and become red when mature. Their wall consists of 8 “shields,”
_i.e._ of plate-like cells, 4 of which cover the upper half, and are
triangular; the 4 round the lower half, to which the stalk of the
antheridia is attached, being quadrilateral, with sides of unequal
length. The shields (Fig. 61 _C_) have dentated edges, with the teeth
fitting into one another, and their faces ornamented with ridges. From
the centre of the internal face of each shield (_C_) a cylindrical
cell, the _manubrium_, projects nearly as far as the centre of the
antheridium; at the inner end of each of the manubria a spherical
cell, the _capitulum_, is situated. Each capitulum bears six secondary
capitula, from each of which four long coiled filaments (_C_, _D_)
project into the cavity of the antheridium. These filaments are divided
by transverse walls into from 100–200 discoid cells, in each of which
a biciliated, coiled spermatozoid is developed (_D_, _E_) from the
nucleus. The spermatozoids escape from their mother-cell and are set
free by the shields separating from one other.

The female organ of reproduction (Fig. 61 _B_, 63) is a small modified
shoot, whose apical cell functions as an oogonium, its protoplasm
forming the oosphere, which has a colourless receptive-spot at the
summit (Fig. 63 _u_). The oogonium is situated on a nodal cell, from
which 5 cells grow out in a circle and coil round the oogonium,
covering it with a close investment. These cells divide once or twice
at the top, so that 5 or 10 small cells are cut off, which project
above the oogonium and form the so-called “crown” (Fig. 63 _k_). The
crown either drops off at fertilisation, or its cells separate to form
a central canal for the passage of the spermatozoids. The wall of the
oosphere[9] above the receptive spot becomes mucilaginous, and allows
the spermatozoid to fuse with the oosphere. The oospore, on germination
(Fig. 64 _sp_), becomes a small filamentous plant of limited growth
(Fig. 64 _i_, _d_, _q_, _pl_)--the proembryo--and from this, as a
lateral outgrowth, the sexual generation is produced.

The order is divided into two sub-orders:--

A. NITELLEÆ. The crown consists of 10 cells; cortex absent: _Nitella_,
_Tolypella_.

B. CHAREÆ. The crown consists of 5 cells; cortex present:
_Tolypellopsis_, _Lamprothamnus_, _Lychnothamnus_, _Chara_.

_Chara crinita_ is parthenogenetic; in large districts of Europe
only female plants are found, yet oospheres are formed capable of
germination.

  [Illustration: FIG. 64.--_Chara fragilis._ Germinating oospore
  (_sp_); _i_, _d_, _g_, _pl_, form together the proembryo rhizoids
  (_w′_) are formed at _d_; _w′_ the so-called tap-root; at _g_ are
  the first leaves of the sexual plant, which appears as a lateral
  bud.]

About 40 species of fossilized _Chara_, determined by their carpogonia,
are known in the geological formations from the Trias up to the present
day.


             Class 8. =Phæophyceæ (Olive-Brown Seaweeds).=

The Phæophyceæ are Algæ, with chromatophores in which the chlorophyll
is masked by a brown colour (phycophæin). The product of assimilation
is a carbohydrate (fucosan), _never true starch_. In the highest
forms (_Fucaceæ_), the thallus presents differentiation into stem,
leaf, and root-like structures. The asexual reproduction takes place
by means of zoospores. The sexual reproduction is effected by the
coalescence of motile gametes, or by oogamous fertilisation. The
swarm-cells are _monosymmetric_, each moved by two cilia which are true
protoplasmic structures, and generally _attached laterally_ (Fig. 65).
The Phæophyceæ are almost entirely saltwater forms; a few species of
_Lithoderma_ live in fresh water.

The class is divided into two families:--

1. PHÆOSPOREÆ: 1 Sub-Family, Zoogonicæ; 2 Sub-Family, Acinetæ.

2. CYCLOSPOREÆ: Fucaceæ.


                        Family 1. =Phæosporeæ.=

The family consists of multicellular plants, whose cells are firmly
united together to form a thallus; this, in the simplest cases, may be
a branched filament of cells (_Ectocarpus_), or, in the highest, may
resemble a stem with leaves (_Laminariaceæ_), while all transitional
forms may be found between these two. The thallus grows by intercalary
divisions (_e.g. Ectocarpus_), or by an apical cell (_e.g._
_Sphacelaria_); pseudo-parenchymatous tissue may sometimes be formed by
cells, which were originally distinct, becoming united together. The
size of the thallus varies; in some species it is quite small--almost
microscopical,--while in the largest it is many metres in length.

The vegetative cells in the lower forms are nearly uniform, but in
those which are more highly developed (_Laminariaceæ_ and _Fucaceæ_),
they are sometimes so highly differentiated that mechanical,
assimilating, storing and conducting systems may be found; the last
named systems are formed of long cells with perforated, transverse
walls, which bear a strong resemblance to the sieve-tubes in the higher
plants.

  [Illustration: FIG. 65.--Swarmspore of _Cutleria multifida_.]

The colouring matter in the living cells (“phæophyl”) contains
chlorophyll; but this is concealed by a brown (“phycophæin”), and a
yellow (“phycoxanthin”) colouring material, and hence all these Algæ
are a lighter or darker _yellow-brown_. Starch is not formed. Asexual
reproduction takes place, (1) by zoospores which arise in unilocular
zoosporangia, and are monosymmetric, with two cilia attached laterally
at the base of the colourless anterior end (Fig. 65), the longer
one being directed forwards and the shorter backwards; or (2) by
aplanospores (?).

  [Illustration: FIG. 66.--_Ectocarpus siliculosus_. _I a-f_ A
  female gamete in the various stages of coming to rest. _II_ A
  motionless female gamete surrounded by male gametes. _III a-e_
  Stages in the coalescence of male and female gametes.]

  [Illustration: FIG. 67.--_Zanardinia collaris_. _A_ Male
  gametangia (the smaller celled) and female gametangia (the
  larger celled). _C_ Female gamete. _D_ Male gamete. _B_, _E_
  Fertilisation. _F_ Zygote. _G_ Germinating zygote.]

Sexual reproduction has only been discovered in a few cases, and takes
place by means of gametes (oogamous fertilisation perhaps occurs in the
Tilopteridæ). The gametes have the same structure as the zoospores,
and arise in multilocular gametangia; these, like the zoosporangia,
are outgrowths from the external surface, or arise as modifications
from it. The conjugating gametes may be similar (_e.g. Ectocarpus
pusillus_), or there may be a more or less pronounced difference of
sex, an indication of which is found in _Ectocarpus siliculosus_ (Fig.
66). When the gametes in this species have swarmed for a time, some,
which are generally larger, are seen to attach themselves by one of the
cilia, which by degrees is shortened to form a kind of stalk (compare
the upper gamete in Fig. 66 _II_); these are the female gametes, which
now become surrounded by a number of males endeavouring to conjugate
with them, but only one succeeds in effecting fertilisation. The
protoplasm of the two gametes coalesces (Fig. 66 _III_), and a zygote
(_e_) is formed. The male gametes which do not conjugate may germinate,
but the plants derived from them are much weaker than those produced
by the zygotes. Strongly pronounced sexual differences are found in
the Cutleriaceæ, in which order the male and female gametes arise in
separate gametangia (Fig. 67 _A_). The male gametes (Fig. 67 _D_) are
much smaller than the female gamete (Fig. 67 _C_); the latter, after
swarming for a short time, withdraws the cilia, and is then ready to
become fertilised (Fig. 67 _B_, _E_), thus we have here a distinct
transition to the oogamous fertilisation which is found in the Fucaceæ.
Alternation of generations is rarely found.

1. Sub-Family. =Zoogonicæ.=

Reproduction by means of gametes and zoospores.

Order 1. =Ectocarpaceæ.= The thallus consists of single or branched
filaments with intercalary growth, extending vertically from a
horizontal, branched filament or a disc, but sometimes it is reduced to
this basal portion only. Zoosporangia and gametangia (for fertilisation
see Fig. 66) are either outgrowths or arise by the transformation of
one or several of the ordinary cells. The most common genera are:
_Ectocarpus_ and _Pylaiella_.

Order 2. =Choristocarpaceæ.= _Choristocarpus_, _Discosporangium_.

Order 3. =Sphacelariaceæ.= The thallus consists of small,
parenchymatous, more or less ramified shoots, presenting a feather-like
appearance. In the shoots, which grow by means of an apical cell (Fig.
68 _S_), a cortical layer, surrounding a row of central cells, is
present. Sporangia and gametangia are outgrowths from the main stem or
its branches. _Sphacelaria_, _Chætopteris_ are common forms.

  [Illustration: FIG. 68.--Apex of the thallus of _Chætopteris
  plumosa_. _S_ Apical cell.]

Order 4. =Encoeliaceæ.= _Punctaria_, _Asperococcus_, _Phyllitis fascia_.

Order 5. =Striariaceæ.= _Striaria_, _Phlœospora_.

Order 6. =Dictyosiphonaceæ.= _Dictyosiphon._

Order 7. =Desmarestiaceæ.= _Desmarestia aculeata_ is common.

Order 8. =Myriotrichiaceæ.= _Myriotrichia._

Order 9. =Elachistaceæ.= _Elachista fucicola_ is a common epiphyte on
species of _Fucus_.

Order 10. =Chordariaceæ.= The shoot-systems are often surrounded
by mucilage. _Chordaria_; _Leathesia difformis_ occurs as rounded,
brown-green masses of the size of a nut, generally attached to other
Seaweeds.

Order 11. =Stilophoraceæ.= _Stilophora rhizodes_ is common.

Order 12. =Spermatochnaceæ.= _Spermatochnus paradoxus_ is common.

Order 13. =Sporochnaceæ.= _Sporochnus._

Order 14. =Ralfsiaceæ.= _Ralfsia verrucosa_ is common as a red-brown
incrustation on stones and rocks at the water’s edge.

Order 15. =Lithodermataceæ.= Some species of the genus _Lithoderma_
occur in fresh water.

  [Illustration: FIG. 69.--_Laminaria digitata_ (much reduced in
  size).]

Order 16. =Laminariaceæ.= The thallus is more or less leathery, and
has generally a root-like lower part (Fig. 69) which serves to attach
it, and a stalk or stem-like part, terminated by a large leaf-like
expansion. Meristematic cells are situated at the base of the leaf,
and from these the new leaves are derived. The older leaf thus pushed
away by the intercalary formation of the younger ones, soon withers
(Fig. 69). Gametes are wanting. Zoosporangia are developed from
the lower part of a simple, few-celled sporangiophore, which is an
outgrowth from a surface-cell and has a large club-formed apical cell.
The sporangia are aggregated into closely packed sori, which cover
the lower part of the terminal leaf, or occur on special, smaller,
lateral, fertile fronds (_Alaria_). Most of the species belonging to
this order live in seas of moderate or cold temperature and occur
in the most northern regions that have yet been explored, forming
their organs of reproduction during the cold and darkness of the
arctic night. _Laminaria_ is destitute of a midrib and has only one
terminal leaf. _L. digitata_ has a broad leaf, which, by the violence
of the waves, is torn into a number of palmate strips (Fig. 69). _L.
saccharina_ has a small, undivided leaf. _Alaria_ has a midrib and
special fertile fronds. _A. esculenta_ occurs plentifully on the west
coast of Norway and on the shores of Great Britain. _Chorda filum_, a
common seaweed, is thick, unbranched, and attains a length of several
metres, without any strong demarcation between stalk and leaf. Some
attain quite a gigantic size, _e.g. Macrocystis pyrifera_, whose
thallus is said sometimes to be more than 300 metres in length. The
_Lessonia_-species, like the above, form submarine forests of seaweed
on the south and south-west coasts of South America, the Cape, and
other localities in the Southern Hemisphere.

   USES. The large Laminarias, where they occur in great numbers,
   are, like the Fuci, used for various purposes, for example, in
   the production of iodine and soda, and as an article of food
   (_Laminaria saccharina_, _Alaria esculenta_, etc.). _Laminaria
   saccharina_ contains a large quantity of sugar (mannit) and is
   in some districts used in the preparation of a kind of syrup;
   in surgical operations it is employed for the distension of
   apertures and passages, as for instance the ear-passage. It
   is by reason of the anatomical peculiarities and structure of
   the cell-walls, that they are employed for this purpose. The
   cell-walls are divided into two layers, an inner one which
   has very little power of swelling, and an outer one, well
   developed and almost gelatinous--the so-called “intercellular
   substance”--which shrivels up when dried, but can absorb water
   and swell to about five times its size. The stalks of _Laminaria
   clustoni_ are officinal.

Order 17. =Cutleriaceæ.= The thallus is formed by the union of the
originally free, band-shaped shoots. The growth is intercalary. Sexual
reproduction by the conjugation of male and female gametes. An asexual
generation of different appearance, which produces zoospores, arises
from the germination of the zygote. _Cutleria_, _Zanardinia_.

Sub-Family 2. =Acinetæ.=

Branched, simple cell-rows with intercalary growth. The organs
of reproduction are partly uni-and partly multicellular; in the
unicellular ones a cell without cilia is formed, which may be destitute
of a cell-wall, but has one nucleus (oosphere?), or which has a
cell-wall and contains several (generally four) nuclei (aplanospores?);
in the multicellular, monosymmetric swarm-cells with two cilia
(spermatozoids?) are formed. The fertilisation has not been observed.

Order 1. =Tilopteridaceæ.= _Haplospora_, _Tilopteris_.


                       Family 2. =Cyclosporeæ.=

The individuals are multicellular, with growth by an apical cell. The
thallus--often bilateral--is differentiated into a root-like structure
(attachment-disc), and stem, sometimes also into leaves (_Sargassum_).
Sometimes a differentiation occurs into various tissue-systems, viz. an
external assimilating tissue, a storing tissue, a mechanical tissue
of thickened, longitudinal, parenchymatous, strengthening cells, and
a conducting tissue of sieve-cells, or of short sieve-tubes with
perforated walls. Colouring material, as in Phæosporeæ. Vegetative
reproduction can only take place by means of detached portions of the
thallus (_Sargassum_), which are kept floating by means of bladders
(Fig. 70 _A_, _a_, Fig. 72). Zoospores are wanting.

The sexual reproduction takes place by oogamous fertilisation. The
oogonia and antheridia are formed inside special organs (conceptacles),
and are surrounded by paraphyses. The conceptacles (Fig. 70 _B_,
Fig. 71 _b_) are small, pear-shaped or spherical depressions,
produced by a special ingrowth of the surface cells of the thallus,
and their mouths (_ostioles_) project like small warts; they are
either situated near the end of the ordinary branches of the thallus
(_Fucus serratus_, Fig. 71 _a_) which may be swollen on this account
(_Fucus vesiculosus_, Fig. 70 _A_, _b_), or on special short branches
(_Ascophyllum_, _Sargassum_). The vertical section of a conceptacle is
seen in Fig. 70 _B_ (see also Fig. 71 _b_) where, in addition to the
paraphyses, oogonia only are seen (_F. vesiculosus_ is diœcious--male
plant, yellow-brown; female plant, olive-brown); but in some
species antheridia, together with oogonia, are produced in the same
conceptacle. The oogonia are large, almost spherical cells, situated on
a short stalk, in each of which are formed from 1–8 (in _Fucus_, 8; in
_Ascophyllum_, 4; in _Halidrys_, 1; in _Pelvetia_, 2) rounded, immotile
oospheres. The wall of the oogonium ruptures, and the oospheres,
still enclosed in the inner membrane, are ejected through the mouth
of the conceptacle, and float about in the water, being finally set
free by the bursting of the inner membrane. The antheridia are oblong
cells (Fig. 70 _C_, _a_), many of which are produced on the same
branched antheridiophore (Fig. 70 _C_); the numerous spermatozoids are
provided with 2 cilia and are very small (Fig. 70 _D_, two antheridia
surrounded by spermatozoids, one being open). The spermatozoids, still
enclosed by the inner membrane of the antheridium, are similarly
set free, and fertilisation takes place in the water, numerous
spermatozoids collecting round the oosphere (Fig. 70 _E_), which is
many times larger, and by their own motion causing it to rotate. After
fertilisation, the oospore surrounds itself with a cell-wall and
germinates immediately, attaching itself (Fig. 70 _F_) to some object,
and by cell-division grows into a new plant.

  [Illustration: FIG. 70.--_Fucus vesiculosus. A_ Portion of
  thallus with swimming bladders (_a_) and conceptacles (_b_). _B_
  Section of a female conceptacle; _h_ the mouth; _p_ the inner
  cavity; _s_ oogonia. _C_ Antheridiophore; _a_ antheridium; _p_
  sterile cells. _D_ Antheridia out of which the spermatozoids are
  escaping. _E_ Fertilisation. _F_ Germinating oospore.]

  [Illustration: FIG. 71.--_Fucus serratus_. _a_ Portion of a male
  plant which has been exposed to the action of the open air for
  some time; small orange-yellow masses, formed by the antheridia,
  are seen outside the mouths of the male conceptacles (nat. size).
  _b_ Cross section through the end of a branch of a female plant,
  showing the female conceptacles (× 4).]

  [Illustration: FIG. 72.--_Sargassum bacciferum_. A portion of the
  thallus, natural size.]

Order 1. =Fucaceæ.= The following species are common on our coasts:
_Fucus vesiculosus_ (Fig. 70) has a thallus with an entire margin,
and with bladders arranged in pairs; _F. serratus_ (Fig. 71) without
bladders, but with serrated margin; _Ascophyllum nodosum_ has
strap-like shoots, which here and there are swollen to form bladders;
_Halidrys siliquosa_ has its swimming bladders divided by transverse
walls; _Himanthalia lorea_, which is found on the west coast of Norway,
and the south coast of England, has a small perennial, button-shaped
part, from the centre of which proceeds the long and sparsely branched,
strap-like, annual shoot, which bears the conceptacles. The Gulf-weed
(_Sargassum bacciferum_, Fig. 72) is well known historically from the
voyage of Columbus; it is met with in large, floating, detached masses
in all oceans, and is found most abundantly in the Atlantic, off the
Canary Islands and the Azores, and towards the Bermudas. The stalked,
spherical air-bladders are the characteristic feature of this genus.
The thallus is more highly developed than in _Fucus_, and there is a
contrast between the stem and leaf-like parts. The portions which are
found floating are always barren, only those attached are fertile.

   USES. The Fucaceæ, like the Laminariaceæ, are used as manure
   (the best kinds being _Fucus vesiculosus_ and _Ascophyllum
   nodosum_), for burning to produce kelp, and as food for domestic
   animals (_Ascophyllum nodosum_ is especially used for this
   purpose).


                        Class 9. =Dictyotales.=

The plants in this class are multicellular, and brown, with apical
growth, new cells being derived either from a flat apical cell, or from
a border of apical cells. The thallus is flat, leaf- or strap-shaped,
attached by haptera, which are either found only at the base, or
on the whole of the lower expansion of the thallus. The cells are
differentiated into the following systems of tissues: an external,
small-celled layer of assimilating cells, generally one cell in
thickness, and an internal, large-celled layer of one or only a few
cells in thickness, forming the mechanical and conducting tissues.
All the reproductive cells are motionless. Asexual reproduction by
naked, motionless spores (tetraspores) which are formed 1–4 in each
tetrasporangium, the latter being outgrowths from the surface cells
of special, sexless individuals. Zoospores are wanting. The sexual
organs are of two kinds, oogonia and antheridia, which are formed from
the surface cells, either on the same or different individuals. The
oogonia are spherical or oval, and are generally placed close together;
each contains one oosphere, which on maturity is ejected into the
surrounding water, and is then naked and motionless. The antheridia
are formed of longitudinal cells, united in groups, whose contents
by repeated divisions--transverse and longitudinal--are divided into
a large number of small, colourless, motionless spermatia--round or
elongated--which are set free by the dissolution of the wall of the
antheridium. The process of fertilisation has not yet been observed.

The Dictyotales, in having tetraspores and spermatia, deviate
considerably from the Phæophyceæ, but may be classed near to the
Tilopteridæ, in which there are asexual spores with 4 cell-nuclei,
which may be considered as an indication of the formation of
tetraspores.

   Order 1. =Dictyotaceæ.= _Dictyota dichotoma_ which has a thin,
   regularly dichotomously divided thallus, occurs on the coasts of
   the British Isles. _Padina_ is found on the south coast.


                Class 10. =Rhodophyceæ (Red Seaweeds).=

The plants comprised in this class are multicellular; they are
simple or branched filaments, or expansions consisting of 1 to
several layers of cells; the thallus may be differentiated (as
in many _Florideæ_), to resemble stem, root, and leaf. The cells
contain a distinctly differentiated nucleus (sometimes several),
and distinct chromatophores, coloured by rhodophyll. The chlorophyll
of the chromatophores is generally masked by a red colouring matter
(phycoerythrin), which may be extracted in cold, fresh water; or rarely
by phycocyan. Pyrenoids occur in some. Starch is never formed in the
chromatophores themselves, but a modification--Florideæ starch--may
be found in the colourless protoplasm. Asexual reproduction by motile
or motionless spores (tetraspores) which are devoid of cilia and of
cell-wall. Swarmspores are never found.

Sexual reproduction is wanting, or takes place by the coalescence of
a spermatium and a more or less developed female cell. The spermatia
are naked masses of protoplasm, devoid of cilia and chromatophores.
The female cell (carpogonium) is enclosed by a cell-wall, and after
fertilisation forms a number of spores, either with or without
cell-walls (carpospores), which grow into new individuals.

The Rhodophyceæ may be divided into two families:

    1. BANGIOIDEÆ.
    2. FLORIDEÆ.


                        Family 1. =Bangioideæ.=

The thallus consists of a branched or unbranched cell-filament, formed
of a single row or of many rows of cells, or of an expansion, one or
two layers of cells in thickness, but without conspicuous pores for the
intercommunication of the cells. The growth of the thallus is chiefly
intercalary. The star-like chromatophores contain chlorophyll and are
coloured blue-green with phycocyan, or reddish with phycoerythrin;
all these colouring matters are occasionally found in the same cell
(_Bangia_-species). Asexual reproduction by tetraspores, without cilia,
but capable of amœboid movements.

Sexual reproduction is wanting, or takes place by the coalescence of a
spermatium with a carpogonium, which is only slightly differentiated
from the vegetative cells, and is devoid of a trichogyne. The
carpospores are destitute of cell-wall and arise directly by the
division of the fertilised oosphere. The Bangioideæ occur chiefly in
salt water.

   Order 1. =Goniotrichaceæ.=--The thallus consists of a
   branched cell-filament without rhizoids. Tetraspores are
   formed directly from the entire contents of the mother-cell,
   without any preceding division. Fertilisation unknown.
   _Asterocystis_, _Goniotrichum_.

   The _Goniotrichaceæ_, through the blue-green _Asterocystis_,
   are allied to the Myxophyceæ, and through _Goniotrichum_ to the
   _Porphyraceæ_.

   Order 2. =Porphyraceæ.=--The thallus is formed of an expansion
   consisting of a layer of 1–2 cells, which, at the base, are
   attached to the substratum by means of a special form of haptera
   (_Porphyra_, _Diploderma_); or of unbranched (very rarely
   slightly branched) filaments, attached at the base by haptera
   (_Bangia_): or it extends from a prostrate cell-disc (various
   species of _Erythrotrichia_). Tetraspores are formed after one
   or more divisions of the mother-cell, either from the whole or
   only a part of its contents; they possess amœboid movements,
   or have a jerky, sliding-forward motion. The antheridia have
   the same appearance as the vegetative cells, but divide several
   times, and several spermatia are formed, either simultaneously
   from the whole contents (_Porphyra_, _Bangia_), or the spermatia
   are successively formed from a part of the contents of the
   antheridium (_Erythrotrichia_). The carpogonium is without a
   trichogyne, but the oosphere has a colourless spot which may
   sometimes rise a little above the surface of the thallus, and
   may be considered as an early stage in the development of the
   trichogyne. The spermatia form a canal through the membrane of
   the carpogonium, and their contents coalesce with the oosphere
   at its colourless spot. The fertilised oosphere divides on
   germination into a number of carpospores, which are set free as
   naked, motionless masses of protoplasm, which grow and give rise
   to new individuals (alternation of generations).


                         Family 2. =Florideæ.=

The thallus has one or more apical cells, grows principally by apical
growth, and may be differentiated into root, stem, and leaf. The
chromatophores vary in form, but have a red or brownish colour, due
to chlorophyll and phycoerythrin. Asexual reproduction by motionless
tetraspores, which generally arise by the division into four of the
contents of the tetrasporangium. The carpogonium has a trichogyne,
and the carpospores, which are formed indirectly from the fertilised
oosphere, possess a cell-wall.

  [Illustration: FIG. 73.--_Callithamnion elegans_: _a_ a plant
  with tetraspores (× 20); _b_ apex of a branch with tetraspores(×
  250).]

  [Illustration: FIG. 74.--_Polysiphonia variegata_: _a_ a portion
  of a male plant with antheridia; _b_ spermatia; _c_ transverse
  section of thallus.]

The thallus may assume very different forms. In the simplest species
it is filamentous and formed of single, branched rows of cells
(_Callithamnion_, etc., Fig. 73). _Ceramium_ has a filamentous thallus,
generally dichotomously forked (Fig. 75), or sometimes pinnately
branched, which, at the nodes, or throughout its entire length, is
covered by a layer of small cortical cells. _Polysiphonia_ (Fig.
74) has a filamentous, much branched thallus, made up of a central
cylindrical cell, surrounded by a layer of other cells, cortical cells,
which in length and position correspond to the central ones. In many of
the Red Algæ the vegetative organs are differentiated into stems and
leaves, the former having, as in _Chara_, unlimited growth in length,
whilst the latter soon attain their full development. _Chondrus_
has a fleshy, gelatinous thallus, without nodes; it is repeatedly
forked into flat branches of varying thickness. _Furcellaria_ has a
forked thallus with thick branches and without nodes. The thallus of
_Delesseria_ (Fig. 76) consists of branches, often bearing leaf-like
structures, with a midrib and lateral ribs springing from it. These
ribs persist through the winter, and at the commencement of the
succeeding period of vegetation the lateral ribs become the starting
points for new leaves. In _Corallina_ the thallus is pinnately
branched, and divided into nodes and internodes. The name has been
given to this genus from the fact that the thallus is incrusted with
carbonate of lime to such a degree that it becomes very hard, and the
whole plant adopts a coral-like appearance. Other genera which are
similarly incrusted, and have a leaf-like or even crustaceous thallus
(such as _Melobesia_, _Lithothamnion_), are included in this family.

In some instances the cells of the thallus may be found
_differentiated_ into more or less well defined tissues, so that it
is possible to find special assimilating, mechanical, and conducting
tissues, the last named in some cases having the double function of
conducting and of serving as a reservoir in which starch is found as
a reserve material. The cells of the Florideæ, which are formed by the
division of a mother-cell into two daughter-cells of unequal size, have
always larger or smaller pits in the cell-walls, and the thin cell-wall
separating two pits from each other is perforated by a number of small
holes. These pits are particularly developed in the conducting tissues,
but sieve-tubes are very rarely to be found.

  [Illustration: FIG. 75.--_Ceramium diaphanum_ (nat. size).]

  [Illustration: FIG. 76.--_Delesseria sanguinea_ (about ⅓).]

_Tetraspores_ may be wanting (_e.g. Lemanea_) or may often arise on
special, non-sexual individuals. In some (_e.g. Batrachospermum_)
only one tetraspore is formed in each tetrasporangium, but the number
is generally four, which may be formed tetrahedrally (Fig. 73) or by
divisional walls perpendicular to each other, or even in a single row.
The tetrasporangia in some species are free (Fig. 73), but in the
majority they are embedded in the thallus.

  [Illustration: FIG. 77.--_A Lejolisia mediterranea_: _r_
  haptera; _s_ longitudinal section through a cystocarp; _p_ the
  empty space left by the liberated spore (_t_). _B-E Nemalion
  multifidum_: _a_ antheridia; _b_ procarpium with trichogyne, to
  which two spermatia are adhering.]

The sexual reproduction (discovered by Thuret and Bornet, 1867)
differs in the essential points from that of all other plants, and
approaches most nearly to the sexual reproduction of the _Bangioideæ_.
The sexual cells are developed from the terminal cells (never nodal
cells) of the branched cell-filaments, which constitute the thallus.
The mother-cells of the spermatia (_spermatangia_) are generally
arranged in a group, in the so-called _antheridia_ (Figs. 74, 77 _A_,
_a_). On becoming ripe the membrane of the spermatangium ruptures
and the _spermatia_ emerge as spherical or ovoid, naked (a little
later they may possess a cell-wall) masses of protoplasm which are
not endowed with the power of motion, and hence are carried passively
by the current of the water in which they may happen to be, to the
female cell. This latter is analogous with the oogonium of the Green
Algæ. The female reproductive organ is termed the _procarpium_, and
consists of two parts, a lower swollen portion--the _carpogonium_
(Fig. 77 _b_ in _A_ and _B_)--which contains the cell-nucleus, and an
upper filamentous prolongation--the _trichogyne_ (Fig. 77 _B_)--which
is homologous with the colourless receptive spot of the oosphere of
the Green Algæ, and the _Porphyraceæ_. In the sexual reproduction
of the majority of the Florideæ, a very important part is played by
certain special cells, rich in cell-contents--the _auxiliary cells_.
These are either dispersed in the interior of the thallus, or are
arranged together in pairs with the cell-filament which bears the
carpogonium, and are generally united with this to form an independent
multicellular _procarpium_. The spermatia attach themselves firmly to
the trichogyne and surround themselves with a cell-wall. The dividing
wall at the point of contact is perforated, and the nucleus of the
spermatium probably travels through the trichogyne to the swollen part
of the procarpium--the _carpogonium_--and fuses with its nucleus. After
fertilisation the trichogyne withers (Fig. 77 _C_), but the lower
portion of the procarpium, constituting the _fertilised oosphere_,
grows out and forms in various ways, first a tuft of spore-forming
filaments known as _gonimoblasts_, and finally the _carpospores_. These
latter form a new asexual generation (compare the germination of the
oospore of _Œdogonium_ and _Coleochæte_).

The gonimoblasts may arise in three ways:--

   1. In the _Nemalionales_, branched filaments grow out from the
   oosphere and form an upright, compressed or expanded tuft of
   spore-forming filaments.

   2. In the _Cryptonemiales_, several branched or unbranched
   filaments (_ooblastema-filaments_) grow out from the oosphere,
   and conjugate in various ways with the auxiliary cells. The
   gonimoblasts are then formed from the single cells produced by
   the conjugation.

   3. In the _Gigartinales_ and _Rhodymeniales_ the oosphere
   conjugates with an auxiliary cell by means of a short
   ooblastema-filament, and from this auxiliary cell a gonimoblast
   is produced.

   The motionless _carpospores_, which sometimes in the early
   stages are naked, and afterwards invested with a cell-wall, are
   developed from the terminal cells (and perhaps also from some
   of the other cells) of the branches of the gonimoblast. The
   gonimoblasts constitute sharply defined parts of the plant in
   which the carpospores arise. These parts are called _cystocarps_
   and are either naked (Fig. 77 _E_), or surrounded by a covering
   (pericarp or involucre, Fig. 77 _A_) formed in different
   ways. On this account the Florideæ were formerly divided into
   GYMNOSPOREÆ (_Batrachospermum_, _Nemalion_, _Ceramium_, etc.)
   and ANGIOSPOREÆ (_Farcellaria_, _Lejolisia_, _Delesseria_,
   _Melobesia_, etc.).

The Florideæ are divided into four sub-families:--

   Sub-Family 1. =Nemalionales.= The fertilised oosphere produces
   directly the gonimoblast.

   Order 1. =Lemaneaceæ.= Algæ of brownish colour and living in
   fresh water. They lack tetraspores, and the very sparingly
   branched fertile filaments, composed of many rows of cells, grow
   out from a proembryo, which consists of a single row of cells
   bearing branches. _Lemanea fluviatilis_, often found on rocks
   and stones in quickly flowing streams.

   Order 2. =Helminthocladiaceæ.= Tetraspores are generally wanting
   (_e.g._ in _Nemalion_) or arise one in each tetrasporangium
   (_e.g. Batrachospermum_) and it is only in _Liagora_
   that four cruciate tetraspores are formed. _Chantransia
   corymbifera_ consists of simple, branched cell-rows, and is
   an independent species. Several other _Chantransia-forms_,
   living in fresh water, are “proembryos” of species of the genus
   _Batrachospermum_. The germinating carpospore grows out into
   filaments and forms a so-called proembryo which, if not shaded,
   attains only a small size, but when growing in shady situations
   presents a much greater development. These highly developed
   proembryos have been described as species of _Chantransia_.
   The proembryo can reproduce by division, or by tetraspores
   which are developed singly in the sporangia; in _B. vagum_ and
   _B. sporulans_ which do not possess fully developed female
   reproductive organs, the proembryos serve almost entirely to
   reproduce the species. The young _Batrachospermum_-plant arises
   from the end of an upright filament of the proembryo. The
   proembryo is generally persistent, and continually produces new
   _Batrachospermums_. These latter bear the sexual reproductive
   organs and also whorls of branches: the central row of cells
   is enclosed by cells growing from the base of the whorls of
   branches, and from these cortical cells secondary proembryos
   are developed. In this alternation of shoots there is really
   no alternation of generations, since the proembryo and the
   shoots with the sexual reproductive organs are parts of the same
   thallus.

   Several species of _Batrachospermum_ have a bluish green or
   verdigris colour. _Nemalion multifidum_ has a brown-red thallus,
   slightly branched, which is attached to rocks near the water’s
   edge.

   Order 3. =Chætangiaceæ.= _Galaxaura_ has a thallus thickly
   incrusted with lime.

   Order 4. =Gelidiaceæ.= _Naccaria, Gelidium._

   Sub-Family 2. =Gigartinales.= The fertilised auxiliary cell
   grows towards the thallus, to produce the gonimoblasts.
   Procarpia generally present.

   Order 5. =Acrotylaceæ.= _Acrotylus._

   Order 6. =Gigartinaceæ.= _Gigartina_, _Phyllophora_,
   _Ahnfeltia_; _Chondrus crispus_, with dark red, dichotomously
   branched thallus, is common on the coasts of Scandinavia and
   Great Britain.

   Order 7. =Rhodophyllidaceæ.= _Rhodophyllis_, _Euthora_;
   _Cystoclonium purpurascens_ is common, and sometimes the ends of
   its branches may be modified into tendril-like haptera.

   Sub-Family 3. =Rhodymeniales.= The fertilised auxiliary cell
   forms the gonimoblast on the side away from the thallus.
   Procarpia are abundantly produced.

   Order 8. =Sphærococcaceæ.= _Gracilaria._

   Order 9. =Rhodymeniaceæ.= _Rhodymenia palmata_ is a common
   species. _Lomentaria_, _Chylocladia_, _Plocamium_.

   Order 10. =Delesseriaceæ.= _Delesseria sanguinea_; _D. alata_
   and _D. sinuosa_ are handsome forms which are not uncommon.

   Order 11. =Bonnemaisoniaceæ.= _Bonnemaisonia._

   Order 12. =Rhodomelaceæ.= _Rhodomela_, _Odonthalia_;
   _Polysiphonia_, of which many species are to be found on the
   coasts of Great Britain, has a filamentous, richly branched
   thallus consisting of a central row of cells surrounded by a
   varying number of cortical cells of similar size--the so-called
   “siphons.”

   Order 13. =Ceramiaceæ.= Pretty Algæ, often branched
   dichotomously, or unilaterally pinnate. _Spermothamnion,
   Griffithsia, Callithamnion, Ceramium, Ptilota._

   Sub-Family 4. =Cryptonemiales.= The cells formed by the
   coalescence of the auxiliary cells and the ooblastema-filaments,
   produce the gonimoblasts. The _carpogonium-filaments_ and
   the auxiliary cells are scattered singly in the thallus.

   Order 14. =Gloiosiphoniaceæ.= _Gloiopeltis._

   Order 15. =Grateloupiaceæ.= _Halymenia, Cryptonemia._

   Order 16. =Dumontiaceæ.= _Dumontia, Dudresnaya._

   Order 17. =Nemastomaceæ.= _Furcellaria_, which has
   dichotomously branched, round shoots, is common on the coasts of
   Great Britain.

   Order 18. =Rhizophyllidaceæ.= _Polyides, Rhizophyllis._

   Order 19. =Squamariaceæ.= The Algæ belonging to this order
   form crust-like coverings on stones, mussel-shells, and on
   other Algæ, but are not themselves incrustated: _Petrocelis_,
   _Cruoria_, _Peyssonellia_.

   Order 20. =Corallinaceæ.= Partly crustaceous, partly erect,
   branched Algæ, thickly incrusted with lime, so that a few
   species (_Lithothamnia_, also called _Nullipora_) occur in
   fossilized condition from Jurassic to Tertiary periods.
   _Melobesia, Lithophyllum, Lithothamnion, Corallina._

USES. “Carragen” is the thallus of _Chondrus crispus_ (Irish Moss)
and _Gigartina mamillosa_. It is a common article of food on the
coasts of Ireland, and swells to a jelly when cooked. It is officinal.
_Rhodymenia palmata_ is generally eaten as food in Ireland and in some
places on the west coast of Norway; it is also used as food for sheep
and hence is termed “Sheep-seaweed.” Agar-Agar is the jelly obtained
from species of _Gelidium_ and _Gigartina_ growing in China and Japan.



                      Sub-Division III. =FUNGI.=


=Mode of Life.= The Fungi have no chlorophyll, and are thus unable in
any stage of their existence to assimilate carbon; they must therefore
live as _saprophytes_ or _parasites_. There is, however, no strong line
of demarcation between these; many Fungi commence as true parasites,
but only attain their full development upon or in dead plants or
animals (_Rhytisma_, _Empusa_). Many saprophytes may occasionally
appear as parasites, and are then designated “_facultative parasites_”
(_Nectria cinnabarina_, _Lophodermium pinastri_), in contradistinction
to those which only appear as parasites, “_obligate parasites_”
(Mildew, Brand-and Rust-Fungi, _Cordyceps_).

The parasites which live on the surface of the host-plant are termed
_epiphytic_ (Mildew, _Fusicladium_); and those living in its tissues
are termed _endophytic_ (_Ustilago_, _Peronospora_). _Epizoic_
(_Oidium tonsurans_, _Laboulbenia_) and _endozoic_ Fungi (_Cordyceps_,
_Entomophthora_), are distinguished, in the same manner, as those
which live on the surface or in the interior of animals. The Fungi
designated _pathogenic_ are especially those which produce disease in
human beings and in animals.

Most of the diseases of plants are attributed to the parasitic Fungi.
These force their way into the host-plant by piercing the outer wall
of the epidermis, as in the Potato-disease; or by growing in through
the stomata, _e.g._ the summer generations of the Rust of Wheat; or
they can only penetrate through a wound, _e.g. Nectria_. Some effect
an entrance into the host-plant by the secretion of a poisonous matter
or ferment, which softens and destroys the cell-walls (_Sclerotinia_).
Some Yeast and Mould Fungi secrete ferments (enzymes), which, for
example, convert cane-sugar into a sugar capable of fermentation.

The relation of the parasitic Fungus to the host-plant is mainly of two
kinds. In the one case, the cell-contents are destroyed, the protoplasm
is killed, and the cellular tissue becomes discoloured and dies
(_Peronospora_, _Armillaria mellea_, _Polyporus_); in the other case,
the parasite has an irritating effect on the cellular tissue, whereby
the affected organ grows more rapidly and becomes larger than normal,
producing _hypertrophy_. Such malformations are termed _Fungi-galls_
(Mycocecidia); in this manner “witches’ brooms” are produced by
_Æcidium_, “pocket-plum” by _Taphrina_, and other deformities by
_Exobasidium_ and _Cystopus candidus_. This hypertrophy may either be
produced by a vigorous cell-multiplication, which is most frequently
the case, or by the enlargement of the individual cells (_Synchytrium_,
_Calyptospora_). The relation between host and Fungus among the Lichens
is of a very peculiar nature, termed “_symbiosis_.”

=Vegetative Organs.= The vegetative parts of a Fungus are termed its
_mycelium_.[10] This is formed of a mass of long, cylindrical, branched
cells resembling threads (and hence termed _hyphæ_), which have a
continued apical growth. The mycelium, in its early development, shows
a well-marked difference between the two main groups of true Fungi:
in the _Phycomycetes_, or Algal Fungi, the mycelium has no transverse
walls, and is therefore unicellular, while in the _Mesomycetes_ and
_Mycomycetes_ it is provided with dividing walls, which gradually arise
during growth, in the youngest hyphæ; intercalary transverse walls
may also be formed at a later period. In the hyphæ of some of the
Higher Fungi (_Hymenomycetes_), connections may be formed between two
contiguous cells of the same hypha, by a protuberance growing out from
an upper cell just above the transverse wall, and forming a junction
with the cell below. These are known as _clamp-connections_; they
appear to be of use in affording communication between the two cells.

The hyphæ of Fungi, where they come in contact with one another,
often grow together, so that =H=-formed combinations (fusions) are
produced, which give rise to very compact felted tissue. When the
hyphæ are not only closely interwoven, but also united and provided
with many transverse walls, the mycelium assumes the appearance of a
tissue with isodiametric cells, and is then termed _pseudo-parenchyma_.
The hyphæ-walls are sometimes very much thickened, and composed of
several layers, and the external layers, by the absorption of water,
may often swell very much and become mucilaginous. In some instances
the walls are colourless, in others coloured, the most frequent colour
being brown. The cell-contents may also be coloured, and in that case
are generally yellow; this colour is chiefly connected with the fat
(oil) which may be found in abundance in the Fungi, whilst starch is
invariably absent in all the true Fungi.

The mycelium assumes many different forms; sometimes it appears as a
thread-like, cobwebby, loose tissue, less frequently as firm strands,
thin or thick membranes, horn-like plates or tuber-like bodies. The
_thread-like_ mycelium may, in the parasitic Fungi, be intercellular
or intracellular, according as it only extends into the interstices
between the cells or enters into the cells proper. In the first case
there are generally found haustoria, or organs of suction (_e.g._ among
the _Peronosporaceæ_; _Taphrina_, on the contrary, has no haustoria);
but haustoria are also found among the epiphytic Fungi (_e.g._
Erysiphaceæ). Intracellular mycelia are found in the Rust-Fungi,
in _Claviceps purpurea_, _Entomophthora_, etc. In spite of its
delicate structure, this mycelium may live a long time, owing to the
circumstance that it continues to grow peripherally, while the older
parts gradually die off (“fairy rings”).

_String-like_ mycelia may be found, for example, in _Phallus_,
_Coprinus_, and are formed of hyphæ, which run more or less parallel
to each other. _Membrane-like_ mycelia are chiefly to be found in
Fungi growing on tree-stems (Polyporaceæ and Agaricaceæ); they may
have a thickness varying from that of the finest tissue-paper to that
of thick leather, and may extend for several feet. The peculiar horny
or leather-like strands and plates which, for instance, appear in
_Armillaria mellea_, are known as _Rhizomorpha_; they may attain a
length of more than fifty feet. The _tuber-like_ mycelia or _sclerotia_
play the part of resting mycelia, since a store of nourishment is
accumulated in them, and after a period of rest they develope organs of
reproduction. The sclerotia are hard, spherical, or irregular bodies,
from the size of a cabbage seed to that of a hand, internally white
or greyish, with a brown or black, pseudo-parenchymatous, external
layer. Sclerotia only occur in the higher Fungi, and are found both in
saprophytes, _e.g. Coprinus_, and in parasites, _e.g. Claviceps_
(Ergot), _Sclerotinia_.

=Reproduction.= SEXUAL REPRODUCTION is found only among the lower Fungi
which stand near to the Algæ, the Algal-Fungi, and takes place by the
same two methods as in the Algæ, namely by _conjugation_ and by the
_fertilisation_ of the egg-cell in the oogonium.

The majority of Fungi have only ASEXUAL reproduction. The
most important methods of this kind of reproduction are the
_sporangio-fructification_ and the _conidio-fructification_.

In the SPORANGIO-FRUCTIFICATION the _spores_ (endospores) _arise
inside_ a mother-cell, the sporangium (Fig. 80). Spores without a
cell-wall, which move in water by means of cilia and hence are known
as _swarmspores_ or _zoospores_, are found among the Oomycetes, the
sporangia in which these are produced being called swarm-sporangia or
zoosporangia (Figs. 86, 87, 91, 94).

In the CONIDIO-FRUCTIFICATION the _conidia_ (exospores) arise on
special hyphæ (conidiophores), or directly from the mycelium. When
conidiophores are present, the conidia are developed upon them
terminally or laterally, either in a basipetal succession (in
many Fungi, for example in _Penicillium_, Fig. 111, _Erysiphe_,
_Cystopus_), or acropetally (in which method the chains of conidia
are often branched; examples, _Pleospora vulgaris_, _Hormodendron
cladosporioides_). All conidia are at first unicellular, sometimes
at a later stage they become two-celled or multicellular through the
formation of partition-walls (_Piptocephalis_). The conidia with thick,
brown cell-walls, and contents rich in fats (_resting conidia_), can
withstand unfavourable external conditions for a much longer period
than conidia with thin walls and poor in contents.

The SPORANGIA arise either from the ordinary cells of the mycelium
(_Protomyces_), or are borne on special hyphæ. They are generally
spherical (_Mucor_, Fig. 80; Saprolegniaceæ), egg-, pear-, or
club-shaped (Ascomycetes), more rarely they are cylindrical or
spindle-shaped. While among the Phycomycetes the size, form, and
number of spores are indefinite in each species, in the Ascomycetes the
sporangia (_asci_) have a definite size, form, and number of spores.
The spores of the Ascomycetes are known as ascospores.

The sporangio-fructification is found under three main forms.

1. FREE SPORANGIOPHORES which are either single (_Mucor_, Fig. 78), or
branched (_Thamnidium_).

2. SPORANGIAL-LAYERS. These are produced by a number of sessile or
shortly-stalked sporangia, being formed close together like a palisade
(_Taphrina_, Fig. 105).

3. SPORANGIOCARPS. These consist usually of many sporangia enclosed in
a covering, they are found only in the Carpoasci, and are also known as
_ascocarps_. The parts of an ascocarp are the _covering_ (_peridium_),
and the _hymenium_, which is in contact with the inner wall of the
peridium, and is generally made up of asci, and sterile, slender
hyphæ. The latter either penetrate between the asci and are branched
and multicellular (_paraphyses_, Figs. 103 _d_, 123, 125, 129), or
clothe those parts of the inner wall which bear no asci (_periphyses_;
among many peronocarpic Ascomycetes, _e.g. Chætomium_, _Sordaria_,
_Stictosphæra hoffmanni_). The ascocarps are produced directly from
the mycelium, or from a _stroma_, that is a vegetative body of various
forms, in which they may be embedded (Figs. 116 _B_, _C_).

Among the conidio-fructifications there are, in the same way, three
divisions.

1. FREE CONIDIOPHORES (Fig. 109). The form of the conidiophores,
the shape, and number of its spores are various. In the most highly
developed Fungi, the Basidiomycetes, there are, however, special more
highly developed conidiophores, the _basidia_, which have a definite
form and spores of a definite shape and number. The conidia borne on
basidia are called _basidiospores_.

2. CONIDIAL-LAYERS. (_a_) The SIMPLEST case of this is found when
the conidiophores arise directly from the mycelium, parallel to
one another, and form a flat body (_e.g. Exobasidium vaccinii_,
_Hypochnus_; among the Phycomycetes, _Empusa muscæ_ and _Cystopus_).
(_b_) In a HIGHER form the conidial-layers are thick, felted threads
(_stroma_) inserted between the mycelium and the _hymenium_ (_i.e._
the region of the conidiophores). Examples are found in a section
of the Pyrenomycetes (Fig. 122). (_c_) The HIGHEST form has the
_basidial-layer_, that is a conidial-layer with more highly developed
conidiophores (basidia). The basidial-layer, with stroma, and the
hymenium (region of the basidia), forms the basidio-fructification,
which is branched in the Clavariaceæ, and hat-shaped in other
Hymenomycetes (in these groups the hymenium is confined to the lower
side of the pileus).

The hymenium of the conidial-layer and basidial-layer is composed
entirely of conidiophores, or of conidiophores and sterile hyphæ
(_paraphyses_) which are probably always unicellular. Paraphyses are
found in _Entomophthora radicans_, and in certain Basidiomycetes
(_e.g. Corticium_).

3. CONIDIOCARPS (_pycnidia_). A special covering surrounds the
conidia-forming elements. The inner side of this covering (_peridium_)
bears the hymenium, _i.e._ those elements from which the conidia are
abstricted. The conidiocarps arise either immediately from the hyphæ
or from a _stroma_ in which they are generally embedded. Conidiocarps
are entirely wanting in the Phycomycetes. On the other hand they are
found among the Ascomycetes and Basidiomycetes, and in the latter group
the conidiocarps contain more highly differentiated conidiophores
(basidia) and are known as _basidiocarps_. Conidiocarps with simple
conidiophores, are found only among the Basidiomycetes, in the
Uredinaceæ, and in _Craterocolla cerasi_. In the Ascomycetes (Figs.
120 _d_, _e_; 117 _a_, _b_; 123 _a_; 124 _b_) the conidiocarps are
visible, as points, to the naked eye, while the basidiocarps of the
Basidiomycetes (Figs. 170, 171, 173–176, 178–180) vary from the size of
a pea to that of a child’s head. The “spermogonia” of the Ascomycetes
and Lichenes, are conidiocarps with small conidia (_microconidia_)
which germinate sometimes more slowly than other conidia, and formerly
were erroneously considered as male reproductive cells, and called
spermatia.

The conidia of the Fungi are not primitive structures. The comparison
of the sporangia and conidia among the Zygomycetes, and among the
species of the genus _Peronospora_ shows, that the conidia are aberrant
formations, and that they have arisen through the degeneration of the
sporangium, which, by the reduction of its spores to one, has itself
become a spore.

   In the genera _Thamnidium_ and _Chætocladium_ the gradual
   diminution of the sporangia, and the reduction of the number
   of spores can be distinctly followed. In _Thamnidium_ the
   number of spores is often reduced to one, which is _free_ in
   the sporangium. In _Chætocladium_ however the sporangia are
   typically _one-spored_, the spore is always united with the
   sporangium, and the two become a single body, the so-called
   _conidium_, which is in reality a closed sporangium. How
   close is the connection between the sporangia and conidia of
   _Thamnidium_ and _Chætocladium_, is seen from the fact that,
   in the conidial stage of _Chætocladium_ the same whorl-form of
   branching appears as in the sporangial stages of _Thamnidium
   chætocladioides_, and also, that the conidia of _Ch.
   fresenianum_ throw off the former sporangium-wall (exosporium),
   while _Ch. jonesii_ germinates without shedding its exosporium.
   The Phycomycetes have doubtless sprung from Water-Algæ and
   inherit the sporangia from them. On this supposition, as the
   Phycomycetes assumed a terrestrial mode of life, the sporangia
   would become adapted to the distribution of the spores by
   means of the air, the sporangia would become small, contain
   dust-like spores, and would eventually become closed-sporangia,
   _i.e._ conidia. The conidia are a terrestrial method for the
   multiplication of Fungi. In the Hemiasci and the Ascomycetes the
   sporangia are still preserved, but in every instance they are
   adapted to terrestrial spore-distribution, their spores being
   set free on the destruction of the sporangium-wall (generally
   shot out) and distributed through the air. For further examples
   of spore-distribution see below, p. 91–93.

The reproduction of Fungi is accomplished not only by spores
and conidia, but also sometimes by _chlamydospores_. These are
fundaments[11] of sporangiophores and conidiophores, which have
taken on a resting condition in the form of a spore, and are able
to germinate and produce carpophores. In the formation of the
chlamydospores the hyphæ accumulate reserve materials at the expense
of the neighbouring cells; in the undivided hyphæ of the Phycomycetes
transverse walls are formed, and finally the chlamydospores are set
free by the decay of the empty cells connecting them with the mycelium.
One must distinguish between _oidia_ and _true chlamydospores_. The
former are more simple, the latter are a somewhat more differentiated
form of carpophore fundaments, which serve for propagation in the same
manner as spores. In _Chlamydomucor racemosus_ the chlamydospores
grow out into the air and form differentiated carpophores. In
the Autobasidiomycetes they only germinate vegetatively, and
not with the formation of fructifications. From _Chlamydomucor_
up to the Autobasidiomycetes the successive development of the
fructification, which is interrupted by the formation of the
chlamydospores, degenerates more and more. Among certain Ustilagineæ
the chlamydospores (brand-spores) no longer germinate with the
production of fructifications. In the Uredinaceæ, only one of the three
chlamydospore-forms has the property of producing fructifications
on germination; the other forms only germinate vegetatively, like
ordinary spores, and in the same manner as the chlamydospores of
the Autobasidiomycetes. In the Hemibasidii, and the Uredinaceæ, in
_Protomyces_, the chlamydospores are the chief means of reproduction.
They are found also among the Ascomycetes.

The sporangia and the conidia of the Fungi have their common origin
in the sporangia of the Phycomycetes. The asci (and the Ascomycetes
which are characterised by these bodies) are descended from the
sporangia-forming, lower Fungi; the basidia (and the Basidiomycetes)
from those which bear conidia. _The sporangia of the Phycomycetes are
the primitive form and the starting point for all the reproductive
forms of the Fungi._ The chlamydospores appear besides in all
classes of Fungi as supplementary forms of reproduction, and are of
no importance in determining relationships. Although the expression
“fruit” must essentially be applied to true Phanerogams, yet, through
usage, the term “_fruit-forms_,” is employed to designate the forms
or means of reproduction of Fungi, and the organs of reproduction
are known as _organs of fructification_, the sporangiophores
and conidiophores as _fruit-bearers_ (_carpophores_), and the
sporangiocarps, conidiocarps, and basidiocarps as “_fruit-bodies_.”

   The majority of Fungi have more than one method of reproduction,
   often on various hosts (Uredinaceæ). Species with one, two,
   or more than two methods of reproduction are spoken of as
   having monomorphic, dimorphic, or pleomorphic fructification.
   Monomorphic, _e.g._ the Tuberaceæ; dimorphic, _Mucor_,
   _Piptocephalis_, Saprolegniaceæ, _Penicillium crustaceum_;
   pleomorphic, _Puccinia graminis_, _Capnodium salicinum_ (in the
   last species there are five methods of reproduction: yeast-like
   conidia, free conidiophores, conidiocarps with small and large
   conidia, and ascocarps).

=The liberation and distribution of the spores and conidia.= The spores
and conidia, on account of their small size and lightness, are spread
far and wide by currents in the air, but in addition to this method,
insects and other animals frequently assist in disseminating them. The
liberation of the conidia is occasionally effected by the complete
shrinking away of the conidiophore, but more frequently by abstriction
from the conidiophores, either by their gradually tapering to a point,
or by the dissolution of a cross-wall (generally of a mucilaginous
nature). The individual links of conidia-chains are detached from
one another in the same way, or often by means of small, intercalary
cells, which are formed at the base of the individual links, and
becoming slimy, dissolve upon the maturity of the spores. Special
contrivances for ejecting the spores and conidia may often be found.
In _Peronospora_ the cylindrical fruit-hyphæ in the dry condition
become strap-shaped and also twisted. These are very hygroscopic,
and the changes of form take place so suddenly, that the spores are
violently detached and shot away. In _Empusa_ a peculiar squirting
mechanism may be found (Fig. 85). Each club-shaped hypha which projects
from the body of the fly, bears a conidium at its apex; a vacuole,
which grows gradually larger, is formed in the slimy contents of the
hypha, and the pressure thereby eventually becomes so great that the
hypha bursts at its apex, and the conidium is shot into the air. By
a similar mechanism, the spores of many of the Agaricaceæ are cast
away from the parent-plants. In the case of _Pilobolus_ (Fig. 84)
the entire sporangium is thrown for some distance into the air by a
similar contrivance, the basal region of the sporangium having, by
the absorption of water, been transformed into a slimy layer which
is readily detached. _Sphærobolus_, a Gasteromycete, has a small,
spherical fruit-body (basidiocarp), the covering of which, when ripe,
suddenly bursts, and the basidiospores contained in it are forcibly
ejected.

_The spores which are enclosed in asci_ are, in some instances, set
free from the mother-cell (ascus) prior to their complete development
(_Elaphomyces_, _Eurotium_). In the case of the majority of the
Pyrenomycetes and Truffles, the asci swell by the absorption of water
into a slimy mass, which gradually disappears, so that the spores lie
free in the fruit-body; they either remain there till the fruit-body
decays, as in those which have no aperture (Perisporiaceæ, Tuberaceæ),
or the slimy mass, by its growth, is forced out through the aperture of
the sporocarp, taking the spores with it (_Nectria_). The ejection of
the spores by mechanical means takes place in a number of Ascomycetes,
and should many spores be simultaneously ejected, a dust-cloud may be
seen with the naked eye to arise in the air from the fruit-body. This
is the case in the larger species of _Peziza_, _Helvella_, _Rhytisma_,
when suddenly exposed to a damp current of air. A distinction is
drawn between a simultaneous ejection of all the spores contained
in the ascus, and an ejection at intervals (successive), when only
one spore at a time is thrown out. The first of these methods is the
most frequent, and is brought about by the ascus being lined with a
layer of protoplasm, which absorbs water to such a degree that the
elastic walls are extended at times to double their original size. The
spores are forced up against the free end of the ascus, a circular
rupture is made at this point, and the elastic walls contract, so
that the fluid with the spores is ejected. Special means may in some
instances be found to keep the spores together, and compel their
simultaneous ejection. Thus, a tough slime may surround all the
spores (_Saccobolus_), or a chain-apparatus, similarly formed of tough
slime; or there may be a hooked appendage from each end of the spores
which hooks into the appendage of the next spore (_Sordaria_). The
paraphyses occurring between the asci in many Ascomycetes, also play a
part in the distribution of the spores, by reason of the pressure they
exercise. The asci in some of the Pyrenomycetes, which are provided
with jar-shaped fruit-bodies, elongate to such an extent that, without
becoming detached from their bases, they reach the mouth of the
fruit-body one at a time, burst and disperse their spores, and so make
room for those succeeding. An ejection of the spores at intervals from
the ascus is rarer. It takes place, for instance, in _Pleospora_, whose
asci have a double wall. The external wall, by absorption of water,
at last becomes ruptured, and the internal and more elastic membrane
forces itself out in the course of a few seconds to one of two or three
times greater length and thickness, so that one spore after another is
forcibly ejected from a narrow aperture at the end of the ascus.

=Germination of spores= (conidia and chlamydospores). In many spores
may be found one or more _germ-pores_, _i.e._ thinner places, either
in the inner membrane (uredospores, _Sordaria_) or in the external
membrane (teleutospores in Rust-Fungi), through which the germination
takes place. Generally this does not occur till the spores have been
set free: in some Ascomycetes germination commences inside the ascus
(_Taphrina_, _Sclerotinia_). The different ways in which the spores
germinate may be classified into three groups.

I. THE ORDINARY GERMINATION occurs by the spore emitting a germ-tube,
which immediately developes into a mycelium. In spores with a double
wall it is only the inner membrane which forms the germ-tube. In
swarmspores a single wall is formed after the withdrawal of the cilia,
and this, by direct elongation, becomes the germ-tube. The protoplasm
accumulated in the spore enters the hypha, which, in pure water, can
only grow as long as the reserve nourishment lasts.

=2.= GERMINATION WITH PROMYCELIUM differs only by the circumstance that
the hypha developed from the germ-tube has a very limited growth, and
hence it does not immediately develope into a mycelium, but produces
conidia (Rust-and Brand-Fungi). This promycelium must only be regarded
as an advanced development of a conidiophore or basidium.

=3.= THE YEAST-FORMATION of conidia consists in the production of
outgrowths, very much constricted at their bases, from one or more
places. Each of the conidia formed in this manner may again germinate
in the same way. When sufficient nourishment is present, a branched
chain of such conidia is formed, and these are finally detached
from one another. Yeast-like buddings from the conidia are produced
in various Fungi, _e.g. Ascoidea_, _Protomyces_, Ustilagineæ,
Ascomycetes, Tremellaceæ, etc. In the Ustilagineæ these conidia are
an important element in the development. The budding conidia of
_Exobasidium_ forms a “mould” on the nutritive solution. The yeast-like
conidia are not to be confounded with the “Mucor-yeast” (comp.
Mucoraceæ). For _Saccharomyces_ see Appendix to the Fungi, page 176.

In a compound spore (_i.e._ when a mass of spores are associated
together) each spore germinates on its own account. There are
sometimes, however, certain among them which do not germinate, but
yield their contents to those which do.

The _length of time_ for which conidia can retain their power of
germination is shortest (being only a few weeks) in those having
thin walls and containing a large supply of water (Peronosporaceæ,
Uredinaceæ). In many spores a resting period is absolutely necessary
before they are able to germinate (resting spores). It has been
observed in some spores and conidia, that the faculty of germinating
may be preserved for several years if the conditions necessary for
germination remain absent (Ustilagineæ, _Eurotium_, _Penicillium_).

The optimum, minimum and maximum temperatures required for the
germination of the spores has been decided in the case of a good many
Fungi. A large portion of the most common Fungi have their optimum at
20°C., minimum at 1–2°C, maximum at 40°C. In the case of pathogenic
Fungi the optimum is adapted to the temperature of the blood. Fungi
living in manure, whose spores are often adapted to germinate in
the alimentary canals of warm-blooded animals, have an optimum
corresponding to the temperature of these animals, but with a little
margin.

=Systematic Division.=--The lowest class of the Fungi is that of the
PHYCOMYCETES, which have an unicellular mycelium, sexual and asexual
reproduction, and have doubtless sprung from sporangia-bearing, lower
Green Algæ. From the Phycomycetes (and certainly from the Zygomycetes)
spring two well defined branches, each with numerous distinct species;
to the one branch belong the HEMIASCI and the ASCOMYCETES, to the other
the HEMIBASIDII and the BASIDIOMYCETES. Ascomycetes and Basidiomycetes
may be united under the title of MYCOMYCETES or HIGHER FUNGI. The
Hemiasci and the Hemibasidii constitute the class of MESOMYCETES.
The Hemiasci are an intermediate form between Zygomycetes and
Ascomycetes; the Hemibasidii a similar group between the Zygomycetes
and Basidiomycetes. Mesomycetes and Mycomycetes have only asexual
reproduction; sexual reproduction is wanting. Their mycelium is
multicellular.

Up to the present time about 39,000 species have been described.

Review of the divisions of the Fungi:--

    Class I.--=Phycomycetes (Algal-Fungi).=

        Sub-Class 1. =Zygomycetes.=
        Sub-Class 2. =Oomycetes.=
           Family 1. ENTOMOPHTHORALES.
           Family 2. CHYTRIDIALES.
           Family 3. MYCOSIPHONALES.

    Class II. =Mesomycetes.=

        Sub-Class 1. =Hemiasci.=
        Sub-Class 2. =Hemibasidii (Brand-Fungi).=

    Class III.--=Mycomycetes (Higher Fungi).=

        Sub-Class 1. =Ascomycetes.=
          Series 1. =Exoasci.=
          Series 2. =Carpoasci.=
            Family 1. GYMNOASCALES.  }
            Family 2. PERISPORIALES. } Angiocarpic Exoasci.
            Family 3. PYRENOMYCETES. }
            Family 4. HYSTERIALES. }  Hemiangiocarpic Exoasci.
            Family 5. DISCOMYCETES.}
            Family 6. HELVELLALES. Gymnocarpic (?) Exoasci.

    Additional: ASCOLICHENES. Lichen-forming Ascomycetes.

        Sub-Class 2. =Basidiomycetes.=
          Series 1.--Protobasidiomycetes. Partly gymnocarpic, partly
                angiocarpic.
          Series 2. Autobasidiomycetes.
            Family 1. DACRYOMYCETES. Gymnocarpic.
            Family 2. HYMENOMYCETES. Partly gymnocarpic, partly
                        hemiangiocarpic.
            Family 3. PHALLOIDEÆ. Hemiangiocarpic.
            Family 4. GASTEROMYCETES. Angiocarpic.

    Additional: BASIDIOLICHENES. Lichen-forming Basidiomycetes.

    Additional to the Fungi: FUNGI IMPERFECTI. Incompletely known
    (_Saccharomyces_, _Oidium_-forms, etc.).


              Class 1. =Phycomycetes (Algal-Fungi).=[12]

This group resembles _Vaucheria_ and the other Siphoneæ among the
Algæ.

ORGANS OF NUTRITION. The mycelium is formed of a single cell, often
thread-like and abundantly branched (Fig. 78). Vegetative propagation
by chlamydospores and oidia. Asexual reproduction by endospores
(sometimes _swarmspores_) and conidia. Sexual reproduction by
conjugation of two hyphæ as in the Conjugatæ, or by fertilisation of an
egg-cell in an oogonium. On this account the class of the Phycomycetes
is divided into two sub-classes: ZYGOMYCETES and OOMYCETES.


                      Sub-Class I. =Zygomycetes.=

Sexual reproduction takes place by zygospores, which function as
resting-spores, and arise in consequence of _conjugation_ (Fig. 81); in
the majority of species these are rarely found, and only under special
conditions. The most common method of reproduction is by endospores, by
acrogenous conidia, by chlamydospores, or by oidia. _Swarmspores are
wanting._ Parasites and saprophytes (order 6 and 7). The zygospores are
generally produced when the formation of sporangia has ceased; _e.g._
by the suppression of the sporangial-hyphæ (_Mucor mucedo_), or by
the diminution of oxygen; _Pilobolus crystallinus_ forms zygospores,
when the sporangia are infected with saprophytic _Piptocephalis_ or
_Pleotrachelus_.

=A.= Asexual reproduction only by sporangia.

Order 1. =Mucoraceæ.= The spherical sporangia contain many spores.
The zygospore is formed between two unicellular branches (gametes).

The unicellular mycelium (Fig. 78) of the Mucoraceæ branches
abundantly, and lives, generally, as a saprophyte on all sorts of
dead organic remains. Some of these Fungi are known to be capable of
producing _alcoholic fermentation_, in common with the Saccharomyces.
This applies especially to _Chlamydomucor racemosus_ (_Mucor
racemosus_), when grown in a saccharine solution, and deprived of
oxygen; the mycelium, under such conditions, becomes divided by
transverse walls into a large number of small cells. Many of these
swell out into spherical or club-shaped cells, and when detached from
one another become chlamydospores, which abstrict new cells of similar
nature (Fig. 79). These chlamydospores were formerly erroneously
termed “mucor-yeast,” but they must not be confounded with the
yeast-conidia (page 94). They are shortened hyphæ, and are not conidia
of definite size, shape, and point of budding. Oidia are also found in
_Chlamydomucor_.

   [Illustration: FIG. 78.--_Mucor mucedo._ A mycelium which has
  sprung from one spore, whose position is marked by the *: _a_,
  _b_, _c_ are three sporangia in different stages of development;
  _a_ is the youngest one, as yet only a short, thick, erect
  branch; _b_ is commencing to form a sporangium which is larger in
  _c_, but not yet separated from its stalk.]

The Mucoraceæ, in addition to the chlamydospores and oidia, have a more
normal and ordinary method of reproduction; viz., by _spores_ which
are formed without any sexual act. _Mucor_ has round sporangia; from
the mycelium one or more long branches, sometimes several centimetres
in length, grow vertically into the air; the apex swells (Figs. 78,
80) into a sphere which soon becomes separated from its stalk by a
transverse wall; in the interior of this sphere (sporangium) a number
of spores are formed which eventually are set free by the rupture of
the wall. The transverse wall protrudes into the sporangium and forms
the well-known columella (Fig. 80 _d_, _e_). The formation of spores
takes place in various ways among the different genera.

  [Illustration: FIG. 79.--Chlamydospores of _Chlamydomucor
  racemosus_ (× 375 times.)]

  [Illustration: FIG. 80.--_Mucor mucedo_: _a_ a spore commencing
  to germinate (× 300 times); _b_ a germinating spore which has
  formed a germ-tube from each end (× 300 times); _c_ the apex of
  a young sporangium before the formation of spores has commenced;
  the stalk is protruded in the sporangium in the form of a column:
  on the wall of the sporangium is found a very fine incrustation
  of lime in the form of thorn-like projections; _d_ a sporangium
  in which the formation of spores has commenced; _e_ a sporangium,
  the wall of which is ruptured, leaving a remnant attached to the
  base of the columella as a small collar. A few spores are seen
  still adhering to the columella.]

SEXUAL REPRODUCTION by conjugation takes place in the following
manner. The ends of two hyphæ meet (Fig. 81) and become more or less
club-shaped; the ends of each of these are cut off by a cell-wall, and
two new small cells (Fig. 81 _A_) are thus formed, these coalesce and
give rise to a new cell which becomes the very thick-walled zygote
(zygospore), and germinates after period of rest, producing a new
hypha, which bears a sporangium (Fig. 81 _E_).

_Mucor mucedo_, Pin-mould, resembles somewhat in appearance
_Penicillium crustaceum_ and is found growing upon various organic
materials (bread, jam, dung, etc.).

_Pilobolus_ (Figs. 83, 84) grows on manure. Its sporangium (Fig. 84
_a″_) is formed during the night and by a peculiar mechanism (page 92)
is shot away from the plant in the course of the day. This generally
takes place in the summer, between eight and ten a.m. The sporangium is
shot away to a height which may be 300 times greater than that of the
plant itself, and by its stickiness it becomes attached to portions of
plants, etc., which are in the vicinity. If these are eaten by animals,
the spores pass into the alimentary canal and are later on, sometimes
even in a germinating condition, passed out with the excrement, in
which they form new mycelia.

_Phycomyces nitens_ (“Oil-mould”) is the largest of the Mould Fungi;
its sporangiophores may attain the height of 10–30 c.m.

Order 2. =Rhizopaceæ.= _Rhizopus nigricans_ (_Mucor stolonifer_) which
lives on decaying fruits containing sugar, on bread, etc., has, at the
base of the sporangiophores, tufts of rhizoids, _i.e._ hyphæ, which
function as organs of attachment. From these, “runners” are produced
which in a similar manner develope sporangiophores and rhizoids.

  [Illustration: FIGS. 81, 82.--_Mucor mucedo_: _A-C_ stages in the
  formation of the zygote; D zygote; E germination of zygote: the
  exospore has burst, and the endospore grown into a hypha bearing
  a sporangium.]

Order 3. =Thamnidiaceæ.= On the same sporangiophore, in addition to
a large, terminal, many-spored sporangium, many smaller, lateral
sporangia are formed with a few spores. Thamnidium.

=B.= Asexual reproduction by sporangia and conidia.

Order 4. =Choanephoraceæ.= _Choanephora_ with creeping endophytic
mycelium, and perpendicular sporangiophores.

Order 5. =Mortierellaceæ.= _Mortierella polycephala_ produces on the
same mycelium conidia and sporangiophores. _M. rostafinskii_ has a long
stalked sporangiophore, which is surrounded at its base by a covering
of numerous felted hyphæ.

  [Illustration: FIG. 83.--_Pilobolus._ Mycelium (_a_, _a_), with a
  sporangiophore (_A_) and the fundament of another (_B_).]

  [Illustration: FIG. 84.--_Pilobolus._ Sporangium (_a″_) with
  stalk (_a-c_), which is covered by many small drops of water
  pressed out by turgescence.]

=C.= Asexual reproduction only by conidia.

Order 6. =Chætocladiaceæ.= The conidia are abstricted singly and
acrogenously. _Chætocladium_ is a parasite on the larger Mucoraceæ.

Order 7. =Piptocephalidaceæ.= The conidia are formed acrogenously and
in a series, by transverse divisions. The zygospore arises at the
summit of the conjugating hyphæ, which are curved so as to resemble a
pair of tongs. _Piptocephalis_ and _Syncephalis_ live parasitically on
the larger Mucoraceæ.


                       Sub-Class 2. =Oomycetes.=

Sexual reproduction is oogamous with the formation of brown,
thick-walled _oospores_ which germinate after a period of rest.
Asexual reproduction by conidia and _swarmspores_. Parasites, seldom
saprophytes.

The oospores are large spores which are formed from the egg-cell
(oosphere) of the _oogonium_ (oosporangium, Fig. 89, 95). A branch of
the mycelium attaches itself to the oogonium and forms at its apex
the so-called “_antheridium_” (pollinodium[13]): this sends one or
more slender prolongations (fertilising tubes) through the wall of the
oogonium to the egg-cell.

  [Illustration: FIG. 85.--_Empusa muscæ_ (Fly-mould). I. A fly
  killed by the fungus, surrounded by a white layer of conidia. II.
  The conidiophores (_t_) projecting from the body of the fly. Some
  of the conidia, a few of which have developed secondary conidia,
  are attached to the hairs (mag. 80 times). III. A perfect hypha.
  IV. A hypha in the act of ejecting a conidium (_c_), enveloped
  in a sticky slime (_g_). V. A conidium which has developed a
  secondary conidium (_sc_). VI. A branched hypha produced by
  cultivation. VII. A secondary conidium which has produced a small
  mycelium (_m_). VIII. A conidium germinating on the fly’s body.
  IX. Mycelium. X. Conidia germinating like yeast in the fatty
  tissue of the fly. (III.-VII. and IX. magnified 300 times; VIII.
  and X. magnified 500 times.)]

   A fertilisation, a passage of the contents of the antheridium
   to the egg-cell, has as yet only been observed in _Pythium_;
   in _Phytophthora_ only one small mass of protoplasm passes
   through the fertilising tube to the egg-cell; in _Peronospora_
   and the Saprolegniaceæ no protoplasm can be observed to pass
   through the fertilising tube, so that in these instances
   _parthenogenesis_ takes place; _Saprolegnia thuretii_, etc.,
   have generally even no antheridia, but nevertheless form normal
   oospores. Fertilisation of the egg-cell by means of self-motile
   _spermatozoids_ is only found in _Monoblepharis sphærica_.

=A.= Asexual reproduction by conidia only.


                     Family 1. =Entomophthorales.=

The mycelium is richly branched. The family is a transitional step to
the conidia-bearing Zygomycetes, since the oospores of many members of
this family arise, and are formed, like zygospores.

Order 1. =Entomophthoraceæ.= Mycelium abundantly developed. This
most frequently lives parasitically in living insects, causing their
death. The conidiophores forming the conidial-layer project from the
skin, and abstrict a proportionately large conidium which is ejected
with considerable force, and by this means transferred to other
insects. These become infected by the entrance of the germ-tube into
their bodies. The spherical, brown resting-spores develope inside the
bodies of insects and germinate by emitting a germ-tube.

   GENERA: _Empusa_ has a good many species which are parasitic
   on flies, moths, grasshoppers, plant-lice. The conidia emit a
   germ-tube which pierces the skin of the insect; a number of
   secondary conidia are then produced inside its body, by division
   or by gemmation similar to that taking place in yeast, each
   of which grows and becomes a long unbranched hypha, and these
   eventually fill up the body of the animal, causing distension
   and death. Each of these hyphæ projects through the skin,
   and abstricts a conidium, which is ejected by a squirting
   contrivance. The best known species is _E. muscæ_ (Fig. 85),
   which makes its appearance epidemically towards autumn on the
   common house-fly, and shows itself by the dead flies which are
   found on the windows and walls attached by their probosces,
   distended wings, and legs. They have swollen abdomen, broad
   white belts of hyphæ between the abdominal rings, and are
   surrounded by a circle of whitish dust formed by the ejected
   conidia.--_Entomophthora_ sends out, at definite places, from
   the mycelium hidden in the insect’s body, bundles of hyphæ,
   which serve the purpose of holding fast the dead insects, the
   ramifications attaching themselves to the substratum: the
   conidiophores are branched, the conidia are ejected by the
   divisional walls between the hyphæ and the conidia dividing into
   two layers, those which terminate the hyphæ suddenly expanding
   and throwing the conidia into the air. _E. radicans_ makes its
   appearance epidemically on caterpillars.

=B.= Asexual reproduction by zoospores or conidia.


                       Family 2. =Chytridiales.=

In this family the mycelium is very sparsely developed or is
wanting. The entire plant consists principally or entirely of a
single zoosporangium whose zoospores have generally one cilium. The
resting-spores arise either directly from the zoosporangium, which,
instead of forming zoospores, surrounds itself by a thick cell-wall; or
they are formed by the conjugation of two cells (in which case they are
spoken of as oospores). Microscopic Fungi, parasitic on water plants
(especially Algæ) or small aquatic animals, seldom on land plants.

Order 1. =Olpidiaceæ.= Without mycelium. Swarmspores and
resting-spores.

   In the _Olpidieæ_, the swarmspores, probably, most frequently
   form themselves into a plasmodium (naked mass of protoplasm)
   which may become a single zoosporangium or a resting sporangium.
   _Olpidium trifolii_ occurs in _Trifolium repens_.--In the
   _Synchytrieæ_ the plasmodium emerging from the swarmspores
   breaks up either at once, or after a period of rest, into
   smaller plasmodia, each of which will become a zoosporangium.
   _Synchytrium anemones_ is found on _Anemone nemorosa_; _S.
   mercurialis_ on _Mercurialis perennis_; _S. aureum_ on many
   plants, particularly _Lysimachia nummularia_.

  [Illustration: FIG. 86.--_Chytridium lagenula._ Zoosporangium _a_
  before, _b_ after the liberation of the swarmspores.]

  [Illustration: FIG. 87.--_Obelidium mucronatum_: _m_ mycelium;
  _s_ swarmspores.]

Order 2. =Rhizidiaceæ.= Mycelium present. Zoospores and
resting-spores.

   _Chytridium_ (Fig. 86). _Obelidium_ (Fig. 87) is bicellular; the
   one cell is the mycelium, the other the zoosporangium; found
   on insects. The species of _Cladochytrium_ are intercellular
   parasites on marsh plants. _Physoderma._

Order 3. =Zygochytriaceæ.= Mycelium present. Zoospores and oospores.
The latter are the product of the conjugation of two cells (Fig. 88).

   _Polyphagus euglenæ_ on _Euglena viridis_. _Urophlyctis pulposa_
   on species of _Chenopodium_.


                      Family 3. =Mycosiphonales.=

The mycelium is bladder-like or branched. Zoospores. Sexual
reproduction by oospores, which are produced in oogonia. The latter are
fertilised, in some forms, by the antheridium.

   Order 1. =Ancylistaceæ.= The entire bladder-like mycelium
   is used for the construction of zoosporangia, oogonia, or
   antheridia. _Lagenedium_ is parasitic on _Spirogyra_, etc.

Order 2. =Peronosporaceæ.= Almost entirely _parasites_. The
unicellular, often very long and abundantly branched mycelium lives
in the intercellular spaces of living plants, especially in the
green portions, and these are more or less destroyed and deformed in
consequence. Special small branches (_suction-organs_, “_haustoria_”)
are pushed into the cells in order to abstract nourishment from them.
Both oospores and conidia germinate either immediately, or they
develope into sporangia with swarmspores, having always two cilia. Only
one oospore is formed in each oogonium; its contents (Fig. 89) divide
into a centrally placed egg-cell and the “periplasm” surrounding it;
this is of a paler colour and on the maturity of the oospore forms its
thick, brown, external covering.

  [Illustration: FIG. 88.--_Polyphagus euglenæ. A_ with smooth,
  _B_ with thorny oospores; _m_ and _f_ the two conjugating cells.]

  [Illustration: FIG. 89.--_Peronospora alsinearum._ Mycelium with
  egg-cell and antheridium.]

  [Illustration: FIG. 90.--_Phytophthora infestans_ (strongly
  magnified). Cross section through a small portion of a
  Potato-leaf (the under side turned upwards): _a_ the mycelium; _b
  b_ two conidiophores projecting through a stoma; _c_ conidia; _e_
  the spongy tissue of the leaf; _g_ the epidermis.]

_The Potato-fungus_ (_Phytophthora infestans_) is of great interest.
Its thallus winters in the Potato-tuber; other organs for passing the
winter, such as oospores, are not known. When the tuber germinates, the
Fungus-hyphæ penetrate the young shoot and keep pace with the aerial
growth and development of the plant. The conidiophores emerge through
the stomata, especially on the under side of the leaves; they branch
like a tree (Fig. 90), and appear to the naked eye as a fine mould on
the surface of the plant. The disease soon makes itself known by the
brown colouring of those parts of the plant which are attacked, and by
their withering. An ovoid conidium arises at first by the formation of
a dividing wall at the apex of each branch of the conidiophore (Fig. 90
_c c_), and immediately underneath it another is formed, which pushes
the first to one side, and so on. These conidia sometimes germinate
directly, and form a mycelium, but most frequently their protoplasm
divides into many small masses, each of which becomes a pear-shaped
zoospore provided with two cilia (Fig. 91). Water is required for
their germination, and when the ripe conidia are placed in a drop of
water the swarm-cells are formed in the course of about five hours.
They swarm about in rain and dewdrops in the Potato-fields, and are
carried with the water to the Potato-plants and to the tubers in
the soil. The wind also very easily conveys the conidia to healthy
Potato-fields and infects them. The enormous quantity of conidia and
swarm-cells that may be formed in the course of a summer explains the
rapid spreading of the disease; and the preceding makes it clear why
wet summers are favourable to its existence. When the swarm-cells
germinate, they round off, and then surround themselves with a
cell-wall which grows out into the germ-tube, and _pierces through the
epidermis_ of the host-plant (Fig. 92). Having entered the host, a new
mycelium is formed. The potato disease, since 1845, has been rampant in
Europe; it has, no doubt, been introduced from America, which, it must
be remembered, is the home of the Potato-plant.

  [Illustration: FIG. 91.--_Phytophthora infestans_: _a-c_ conidia
  detached; in _c_ the swarm-cells are leaving the mother-cell; _d_
  two free-swimming swarm-cells.]

  [Illustration: FIG. 92.--_Phytophthora infestans._ Cross section
  through a portion of a Potato-stalk. Two germinating conidia
  (_a_, _b_) piercing the epidermis, and the mycelium penetrating
  the cells.]

   The conidia exhibit various characters which are employed for
   the separation of the genera. _Pythium_ is the most simple
   form. The contents of the terminally-formed conidia emerge as
   a spherical mass and divide into swarmspores. _P. de Baryanum_
   lives in the seedlings of many different Flowering-plants,
   which it completely destroys.--_Phytophthora_ is distinguished
   by the circumstance that the sparsely-branched conidiophores
   bear, sympodially, chains of conidia. Besides the Potato-fungus
   (see above), _Ph. fagi_ belongs to this group; it developes
   oospores very abundantly, and does great harm to seedlings of
   the Beech, Sycamore, and Pine trees.--_Peronospora_ generally
   has conidiophores which are repeatedly forked, and bear a
   conidium on each of the most extreme ramifications. Many do
   great harm to their host-plants. _P. viticola_, on Vines, and
   _P. nivea_, on umbelliferous plants, have swarmspores, which are
   absent in the following species of this genus: _P. sparsa_, on
   Roses; _P. gangliformis_, on composites; _P. alsinearum_, on
   Stitchwort; _P. parasitica_, on cruciferous plants; _P. viciæ_,
   on Vetches and Peas; _P. schachtii_, on Beets; _P. violacea_,
   on the flowers of _Scabiosa_; _P. radii_, on the ray-florets of
   _Matricaria_.--_Cystopus_ (_Albugo_) has the conidia developed
   in chains, which form a cohesive white layer underneath the
   epidermis of the host-plant. _Cystopus candidus_, on cruciferous
   plants, especially Shepherd’s Purse and _Brassica_; the
   germination commences on the cotyledons, and from this point the
   mycelium developes together with the host-plant; _C. cubicus_,
   on the leaves of Compositæ.

  [Illustration: FIG. 93.--A fly overgrown with _Saprolegnia_.]

  [Illustration: FIG. 94.--Formation of swarmspores in a
  _Saprolegnia_: a germinating swarmspores.]

Order 3. =Saprolegniaceæ=, _Water-Fungi_ which live as saprophytes on
organic remains lying in water, for instance, on dead flies (Fig. 93),
worms, remains of plants; but they may also make their appearance on
living animals, being frequently found, for example, on the young trout
in rearing establishments.

  [Illustration: FIG. 95.--Oogonium with two antheridia, _Achlya
  racemosa_.]

The thallus is a single, long and branched cell. It has one portion
which serves as root, and lives in the substratum, where it ramifies
abundantly for the purpose of absorbing nourishment; and another
portion projecting freely in the water, and sending out hyphæ on all
sides (Fig. 93). The asexual reproduction takes place by swarmspores
(Fig. 94), which are developed in large sporangia; these swarmspores
generally possess two cilia, and on germination grow into new plants.
The entire protoplasm in the oogonium is formed into one or more
oospheres, without any surrounding “periplasm.” The oospheres may not
be fertilised (p. 100), and then develope parthenogenetically.

   Genera: _Saprolegnia_, whose swarmspores disperse immediately
   after having left the sporangium. _S. ferax_ is the
   cause of a disease in fish (“Salmon disease”) and in the
   crayfish.--_Achlya_, whose swarmspores accumulate in a hollow
   ball before the mouth of the sporangium.--_Leptomitus_ has
   strongly indented hyphæ, causing a “linked” appearance.
   _L. lacteus_ is frequent in the waste matter from sugar
   factories.--_Monoblepharis_ deviates from the others by the
   greater development of its fertilising process; the oosphere,
   situated in an open oogonium, becoming fertilised by self-motile
   spermatozoids, which are provided with a cilium at the posterior
   end.


                        Class 2. =Mesomycetes.=

The Mesomycetes are intermediate forms between the Phycomycetes and
the Higher Fungi. In the vegetative organs, and in the multicellular
hyphæ, they resemble the Higher Fungi; the methods of reproduction,
however, show the characters of the Phycomycetes, namely sporangia
and conidiophores of varying size and with varying number of spores;
definite and typically formed asci and basidia are not present. Sexual
reproduction is wanting. The HEMIASCI are transitional between the
Phycomycetes and the Ascomycetes, the HEMIBASIDII (Brand-Fungi) form
the transition to the Basidiomycetes.


                       Sub-Class 1. =Hemiasci.=

The Hemiasci are Fungi with _sporangia_ which, _although resembling
asci_, yet have _not_, however, _a definite form and a definite number
of spores_. Besides endospores, conidia, chlamydospores and oidia are
found.

   Order 1. =Ascoideaceæ.= _Ascoidea rubescens_ forms irregular,
   reddish-brown masses in the sap issuing from felled Beeches. It
   has _free sporangia_, which resemble asci in their structure, in
   the development and ejection, and in the definite shape and size
   of the spores. The formation of the sporangia takes place when
   the nutriment is nearly exhausted, and resembles that of the
   conidia, since they are developed from the end of a hypha which
   enlarges, and the swelling becomes separated by a transverse
   wall. Within the sporangia numerous spores of a cap-like form
   are developed, which are set free through an opening at the
   apex. Sporangia are formed successively at the apex of the
   same hypha, the second commencing to develope as the first is
   dehiscing. Conidia and sporangia are not formed simultaneously;
   the former may be considered as closed sporangia.

   Order 2. =Protomycetaceæ.= _Protomyces pachydermus_ causes
   hard swellings on the stems and leaf-stalks of the Cichorieæ
   (_Taraxacum_, etc.). These swellings consist of _chlamydospores_
   (resting-spores), which germinate and become free, ascus-like
   sporangia, with numerous small spores. In nutritive solutions
   the chlamydospores form conidia with yeast-like buddings. _P.
   macrosporus_ on _Ægopodium_, and other Umbelliferæ.

   Order 3. =Thelebolaceæ.= _Thelebolus stercoreus_, is found
   on the dung of deer, hares, and rabbits, and has _closed
   sporangia_, which resemble asci in their shape and regular
   construction, and in the ejection of spores. The covering
   encloses only one sporangium, even where the sporangia arise
   close together.

This order, by reason of the covering of the sporangia, forms the
transition from the Hemiasci to the Carpoasci, while the two first
supply an intermediate step to the Exoasci.


               Sub-Class 2. =Hemibasidii, Brand-Fungi.=

The Brand-Fungi (also known as USTILAGINEÆ) are Fungi with
_basidia-like conidiophores_, which, however, have not yet advanced
to a definite form or number of conidia. They are true parasites,
whose mycelium spreads itself in the intercellular spaces of Flowering
plants. The mycelium is colourless, quickly perishable, has transverse
walls at some distance from each other (Fig. 96), and sends out
haustoria into the cells of the host-plant.

  [Illustration: FIG. 96.--_Entyloma ranunculi._ 1. Cross section
  of a portion of a leaf of _Ficaria_ permeated by the mycelium; a
  bundle of hyphæ with conidia emerging from a stoma; in one of the
  cells are found four brand-spores. 2. A brand-spore developed in
  the middle of a hypha.]

It most frequently happens that the germ-tube enters the host-plant at
its most tender age, that is, during the germination of the seed; the
mycelium then wanders about in the tissues of the shoot during its
growth, until it reaches that part of the plant where the spores are to
be formed. The spore-formation takes place in the same way in all those
species whose brand-spores are developed in the floral parts of the
host-plant. Many Brand-Fungi have, however, a more local occurrence,
and the mycelium is restricted to a smaller area of the leaf or stem.
Those organs of the host-plant in which the brand-spores are developed
often become strongly hypertrophied. In perennial plants the mycelium
winters very often in the rhizome.

  [Illustration: FIG. 97.--_Doassansia alismatis._ 1. A fruit-body,
  formed by a covering of oblong hyphæ, which encloses a mass
  of brand-spores, and is embedded in the leaf-tissue of the
  host-plant; 20 times natural size. 2. A germinating brand-spore,
  500 times natural size. 3. Three connected resting-spores, 400
  times natural size. 4. Two conidia grown together, 600 times
  natural size.]

The brand-spores are the winter resting-spores of the Brand-Fungi.
They arise in the tissues of the host-plant, which is often destroyed,
and become free through the rupture of the epidermis; they are
thick-walled, generally brown or violet, and very often possess warts,
spines, or reticulate markings. Fruit-bodies, that is enclosed organs
of reproduction, are found in few genera (_Sphacelotheca_, _Graphiola_;
_Doassansia_, Fig. 97). In _Tolyposporium_, _Tuburcinia_, _Thecaphora_
(Fig. 102), etc., the brand-spores are united into a _ball of spores_.
On germination the brand-spores behave as _chlamydospores_, namely,
as the fundament of conidiophores, by emitting a short germ-tube,
_i.e._ a conidiophore (“promycelium”). The USTILAGINACEÆ (Fig. 99, 2)
have a short _transversely divided_ conidiophore, with _laterally_
developed conidia (comp. the basidia of the Protobasidiomycetes).
The conidiophores of the TILLETIACEÆ are undivided (unicellular
promycelia), and bear the conidia terminally, and so resemble the
basidia of the Autobasidiomycetes.

  [Illustration: FIG. 98.--_Tuburcinia._ 1. _T. trientalis._ Hyphæ,
  some of which bear conidia at the apex, forcing themselves out
  between the epidermal cells on the under side of the leaf; 320
  times natural size. 2. _T. trientalis._ A ball of spores in which
  some of the individual brand-spores are about to germinate; 520
  times natural size. 3. _T. primulicola_: various forms of conidia
  (500 times natural size).]

   In _Tilletia_, _Entyloma_, _Neovossia_, _Tuburcinia_, the
   brand-spores germinate and form basidia-like conidiophores with
   spindle-shaped conidia; their mycelium, on the other hand,
   produces later only single, sickle-shaped conidia, so that
   two kinds of conidia are found, as in a few Basidiomycetes.
   In some species, _e.g. Ustilago hordei_, the brand-spores
   only germinate vegetatively and form a mycelium. In nutritive
   solutions (solutions of dung, etc.) where they live as
   _saprophytes_, the brand-spores of many species emit germ-tubes,
   and on these, _yeast-like conidia_ are produced by repeated
   budding, which grow into mycelia only when the nutritive
   solution is exhausted. These conidia have not the power of
   producing alcoholic fermentation. The very numerous conidia,
   which are found in the dung of herbivorous animals, are probably
   the yeast-conidia of Brand-Fungi. The brand-spores, which are
   eaten by animals with the grain and hay, pass into the dung
   and without doubt give rise to a very rich multiplication of
   yeast-conidia.

  [Illustration: FIG. 99.--_Ustilago._ 1. Formation of
  brand-spores. 2. Germinating brand-spore of _U. perennans_.
  3. Germinating brand-spore of _U. cardui_ (after Brefeld). 4.
  _U. filiformis. a_ A brand-spore with developed basidium;
  _b_ another, with a conidium; _c_ with two conidia; _d_ with
  two conidia placed diametrically opposite to each other; _e_,
  detached conidia which are growing into hyphæ.]

  [Illustration: FIG. 100.--_Tilletia tritici_: _a_ an ear of
  Wheat in which all the grains are attacked by Stinkbrand;
  _b_ a blighted corn surrounded by the chaff; _c_ a blighted
  corn grown together with a stamen; _d_ the same cut across;
  _e_ a brand-spore; _f_, _g_, _h_ germinating brand-spores;
  _i_ germinating conidia; _j_ the mycelium; _k_-_k_
  brand-spore-forming mycelium-threads. (_c-h_ magnified 400 times;
  _i-k_ 300 times.)]

   The conidia (also called “sporidia”) of many species unite
   generally into an H-form (Figs. 97, 4; 100 h; 101, 4). This
   union in pairs does not, however, take place with a view to
   germination, there is no fusion of nuclei, and therefore in this
   “fusion” there is no sexual act.

   Order 1. =Ustilaginaceæ.= Conidiophores with transverse walls
   and lateral conidia.--_Ustilago_ (Fig. 99) generally developes
   its spores in the floral organs of its host-plant, the ovary or
   anthers, where they arise from hyphæ, and form a slimy mass
   which when mature becomes a black dust.

   To this order belong _U. avenæ_, parasitic on Oats, _U. hordei_
   and _U. nuda_ (_U. jenseni_), on Barley; these are the usual
   cause of “Smut” on cereals. _U. hypodytes_ on straw of _Elymus_
   and _Agropyrum_. _U. filiformis_ in the leaves of _Glyceria_.
   _U. caricis_ transforms the fruits of various species of
   _Carex_ into black, dusty balls. _U. violacea_ developes its
   violet spore-powder in the anthers of the Caryophyllaceæ.
   _U. tragopogonis_, transforms entire inflorescences of
   _Tragopogon_ into a black-violet mass. Among the largest are _U.
   grandis_, which causes the large swollen nodes in the stem of
   _Phragmites_, and the Maize Blight, _U. maydis_, which produces
   outgrowths about the size of a hand on the spadix of the Maize.

   Order 2. =Tilletiaceæ.= Conidiophores undivided, generally
   several conidia arise at their apices.--_Tilletia tritici_,
   the _Stinkbrand on Wheat_ (Fig. 100). The mycelium lives in
   Wheat-plants, producing its spores in the ovary after the whole
   interior of this body has been destroyed by the mycelium, with
   the exception of the external layer of the wall of the ovary,
   which remains essentially unaltered and encloses the closely
   packed, firm mass of spores (Fig. 100 _d_). The grains of Wheat
   thus attacked are shorter and thicker than the sound ones,
   and the ears show the presence of this Fungus by their erect
   position, and the wide separation of the chaff (Fig. 100 _a_).
   The unpleasant odour of the ovary prior to the ripening of the
   spores, has given the name “Stinkbrand,” and, in like manner,
   its hardness when it encloses the ripe spores, is the reason
   of its being also called “Stonebrand.” On account of this
   hardness, the diseased grains are readily harvested together
   with the healthy ones, which become infected by the spores at
   the threshing. _T. lævis_ (_T. fœtens_) also occurs on Wheat and
   has smooth brand-spores.

  [Illustration: FIG. 101.--_Urocystis._ 1, _U. covalloides_.
  A spore-ball, magnified 450 times. 2–4, _U. anemones_: 2–3,
  brand-spores which are about to germinate (magnified 450 times).
  4, Conidia, the two in a state of fusion, a third with vacuoles
  and division-wall, magnified 500 times.]

   _Entyloma_ (Fig. 96), a genus with numerous species, which
   appear in spots on the leaves of the host-plant, and
   _Tuburcinia_ (Fig. 98), which makes its appearance on the
   Primulaceæ, produce white conidia-spots on the surface of the
   host-plant. The first-named has single spores, the latter has
   its spores closely massed together.--_Urocystis_ (Fig. 101)
   has its spores surrounded by a number of small and lighter
   coloured barren spores. _U. occulta_, Rye-stem Blight, forms
   its spores in long streaks in the stems and leaves of the Rye,
   and does considerable damage. _U. cepulæ_ on Onions. _U. violæ_
   forms large dark-violet swellings in the leaf-stalk and stems
   of Violets.--_Thecaphora_ (Fig. 102) appears in seedlings of
   _Convolvulus_ and _Astragalus_.

   As a means of protection against the Smut-Fungi which make their
   appearance on the different cereals, a submersion of the grains
   in a solution of blue vitriol (½%) for twelve hours, or better
   still, submerging for five minutes in water heated to 53–55° _C_
   (Jensen’s method) is employed.

  [Illustration: FIG. 102.--_Thecaphora._ 1, _T. convolvuli_, a
  ball of spores, one of the brand-spores has emitted a septate
  branched conidiophore (× 520). 2, _T. affinis_, a ball of spores
  (× 520).]


                 Class 3. =Mycomycetes, Higher Fungi.=

The MYCOMYCETES are not entirely aquatic in habit; they have hyphæ with
_transverse walls_, but _no sexual reproductive organs_. The asexual
reproduction takes place in very different ways; by endospores (in
asci), conidia, basidiospores, chlamydospores, and oidia. Swarmspores
are never found.

Two chief methods of reproduction may be distinguished, and hence the
class may be divided into two large sub-classes:--the ASCOMYCETES (with
asci), and the BASIDIOMYCETES (with basidia).


                      Sub-Class 1. =Ascomycetes.=

The main characteristic which distinguishes the Ascomycetes is the
_ascus_; a name given to a sporangium of a definite shape and size,
and containing a definite number of spores. The shape is generally
club-like or spherical, the number of spores 8 (in some 2, 4, 16 or
more), see Figs. 103, 105, 108, 110, 113, 116, 120, 121, 123, 129.

In the lowest forms, the EXOASCI, the ascus springs directly from the
mycelium without the formation of a fruit-body (_i.e._ ascocarp).
In the higher forms, which contain many species, the CARPOASCI, the
asci are united and form ascocarps which may be more or less enclosed
(angiocarpic, hemiangiocarpic, and probably gymnocarpic).

  [Illustration: FIG. 103.--Endogenous formation of spores in
  _Peziza confluens_. In the youngest asci there is only one
  nucleus (_b_, _e_); this divides into two (_f_); and the division
  is repeated so that there are 4 nuclei in _c_ and 8 in _g_. These
  surround themselves with protoplasm and a cell-wall (_h_, _i_).
  The protoplasm of the mother-cell is not entirely used up.]

The hyphæ of the _Mycelium_ in some remain free, in others they are
felted together and form thick strands or flat, cushion-like bodies
(compare in particular the stromata of the Pyrenomycetes). Some species
form _sclerotia_ (Figs. 116, 128).

Asexual reproduction by means of _conidia_ is known in many species
as the principal means of reproduction, and the one which affords
the most rapid means of distribution. The conidia may be produced on
conidiophores (Fig. 109), in conidial-layers (Fig. 122), and often in
conidiocarps (pycnidia, Figs. 120 _d_, _e_; 123 _a_; 124 _b._). These
last occur partly as the so-called “spermogonia” (that is, pycnidia
with microconidia). The conidiophores never approach the basidia.

   In many species the ascospores germinate and form conidia
   immediately (_Nectria cinnabarina_, _Sclerotinia_, _Taphrina_,
   etc.), sometimes while they are still in the ascus and before
   their ejection (_Taphrina_, Fig. 105 _a_). In many instances
   the conidia by means of continued budding can, for a longer
   or shorter time, produce yeast-conidia, _e.g. Taphrina_. In
   many other cases the conidia arise from the germ-tubes of the
   ascospores, or at any part of the mycelium. The unripe asci
   of _Taphrina_, when placed in water, develop conidia at their
   apices. The _Sclerotinia_-species produce numerous conidia
   whose germination has never been observed. The formation of
   conidia and asci sometimes takes place on the same fruit-body.
   In _Heterosphæria patella_ the conidia and asci are developed
   successively in the same fruit-body; in the ascocarps of
   _Dermatea frangula_ and _Sclerotinia sclerotiorum_ the formation
   of conidia may take place. The ascocarps frequently arise
   from the conidial-layers (_Nectria cinnabarina_, etc.). This
   relationship of the two forms of reproduction to each other
   may be explained by considering that both have descended
   phylogenetically from sporangia.

Sometimes _chlamydospores_ and _oidia_ also appear in the Ascomycetes;
on germination, however, they do not, as in _Protomyces_, form
sporangia, and on this account cannot be distinctly distinguished from
conidia.

The asci are morphologically the highest form of reproduction and
are always found at the close of the development of these Fungi; the
accessory forms of reproduction are first developed, but a well-defined
alternation of generations does not occur.

   In the Ascomycetes there are more than 11,000 described species,
   which can be classed as follows:--

    Series 1. EXOASCI. Only one order.
       „   2. CARPOASCI.
                Family 1. _Gymnoascales_,  }
                   „   2. _Perisporiales_, } Angiocarpic Carpoasci.
                   „   3. _Pyrenomycetes_, }
                   „   4. _Hysteriales_, } Hemiangiocarpic Carpoasci.
                   „   5. _Discomycetes_,}
                   „   6. _Helvellales_, Gymnocarpic (?) Carpoasci.
    Additional _Ascolichenes_: Lichen-forming Ascomycetes.


                         Series 1. =Exoasci.=

Ascomycetes with FREE ASCI; sometimes also conidia, chlamydospores and
oidia. One order.

Order. =Taphrinaceæ.= Of the genera belonging to this order,
_Taphrina_, _Endomyces_, and _Ascocorticium_, the first is most
important.

   _Endomyces decipiens_ is a parasite in the fruit-body of
   _Armillaria mellea_; _E. magnusii_ lives in the gelatinous,
   fermenting exudations of Oak-trees; _Ascocorticium albidum_
   is found under the bark of the Fir-tree. _Endomyces_ has
   chlamydospores and oidia.

The species of _Taphrina_ are parasites, whose free asci may be found
in great numbers, generally closely pressed together, on the parts of
plants which they have attacked. The asci are developed directly from
the ascogenous cells of a fertile, generally sub-cuticular, hypha,
which arises from the sterile mycelium. The latter arises from the
germinating ascospore, and may hibernate in the tissues of its host,
particularly in the winter buds, and then with the commencement of
the next period of vegetation it continues its growth side by side
with that of its host. The hyphæ ramify in the intercellular spaces or
beneath the cuticle, but have no haustoria. The ascospores (Fig. 105
_A_) and unripe asci may produce conidia.

  [Illustration: FIG. 104.--_Taphrina_ (_Exoascus_) _pruni_.
  Yeast-like budding of a germinating spore (× 600).]

  [Illustration: FIG. 105.--_Taphrina betulina_: _a_ ascus filled
  with conidia; _b_ germinating spores (× 600).]

   Very remarkable appearances, and swellings of the attacked
   tissues, are produced when the mycelium is perennial; for
   example, the “Witches’-brooms” and “Pockets.” The hard, hollow,
   stoneless plums, known as “Pocket” or “Bladder” Plums, are
   produced by considerable changes in the tissues of the fruit;
   these are caused particularly by _T. pruni_ on several species
   of _Prunus_. The “Witches’-brooms,” on the contrary, are
   deformations of entire twigs or branches, and often attain
   a very large size. They occur on _Alnus incana_, caused by
   _T. epiphylla_; on _Carpinus betulus_, by _T. carpini_; on
   Cherry-trees, by _T. cerasi_; on Plum-trees, by _T. insititiæ_;
   on Birches, by _T. turgida_ and _T. betulina_. _T. deformans_
   attacks the leaves of the Peach, and causes them to curl.

   When a perennial mycelium is wanting, the infection is confined
   as a rule to white or yellow spots on the leaves, _e.g._ the
   commonest, _T. sadebeckii_, on _Alnus glutinosa_, and _T. aurea_
   on species of _Populus_. _T. alni incanæ_ (Fig. 106) causes
   considerable hypertrophies on the pistillate catkins of the
   Alder, which may be compared to the “pockets” of _Prunus_.

  [Illustration: FIG. 106.--_Taphrina alni incanæ_ on the Alder
  (nat. size).]


                        Series 2. =Carpoasci.=

The Carpoasci are Ascomycetes, whose asci are enclosed in fruit-bodies,
_i.e. ascocarps_. The accessory means of reproduction are free
conidiophores (Fig. 109), conidial-layers (Fig. 122), conidiocarps
(Fig. 120 _D_, _E_, etc.), chlamydospores and oidia.

For the different methods of distributing the ascospores, see p. 92.

Of the six families of the Carpoasci, the first three--_Gymnoascales_,
_Perisporiales_, and _Pyrenomycetes_--are ANGIOCARPIC (that is,
the ascocarp remains closed throughout its existence, and does not
dehisce when ripe); the fourth and fifth families (_Hysteriales_ and
_Discomycetes_), on the other hand, are HEMIANGIOCARPIC (the ascocarp,
here also called an _apothecium_, is closed in the early stages,
but opens at the commencement of ripening and exposes a hymenium of
crowded asci); the family of _Helvellales_ has probably GYMNOCARPIC (or
hemiangiocarpic) fruit-bodies.


                       Family 1. =Gymnoascales.=

The ascocarps are surrounded by a _spongy and incomplete envelope_. One
order, poor in species.

   Order =Gymnoascaceæ=.--The ascocarps are borne sometimes
   solitarily, or sometimes coiled together. _Gymnoascus reessii_
   forms small bodies about 1 mm. in diameter on old horse-dung,
   which at first are white and afterwards orange-red.--_Ctenomyces
   serratus_ lives on the old feathers in birds’ nests.


                      Family 2. =Perisporiales.=

The ascocarps are surrounded by a _complete envelope_ without any
opening: the fruit-bodies are cleistocarpic; the spores are only
liberated after the disintegration of the fruit-bodies. Paraphyses
are wanting. The two first orders have in addition the means of
reproduction by conidia.

Order 1. =Erysiphaceæ, Mildews.= The Fungi belonging to this order are
epiphytic parasites, whose mycelium, somewhat resembling a cobweb, may
be seen on the leaves and other green portions of plants (see Figs.
107, 108). The hyphæ ramify in all directions upon the surface of their
host, and emit haustoria which penetrate the epidermal cells, and
thus derive the necessary nutriment. The Mildew-Fungi thus belong to
the obligate parasites, and during their growth dwarf and destroy the
portions of their host on which they live. The reproduction takes place
in the first instance by abstriction of conidio-chains from the end of
special branches (Fig. 108 _c_, a hypha is seen in the act of detaching
a conidium). The conidia may germinate immediately, and thus quickly
reproduce their species. When present in large numbers they appear as
a white meal covering the surface of the plant on which the fungus is
found. Later on appear the dark brown, spheroid ascocarps (Fig. 108
_a_) which, although small, are generally just visible to the naked eye
as black specks.

  [Illustration: FIG. 107.--_Erysiphe cichoracearum_: _a_
  mycelium-threads; _b_ sterile hypha (“pollinodium”); _c_ fertile
  hypha (ascogone or archicarp); _d_ and _e_ young ascocarps.]

A characteristic feature of the Mildew-Fungi is the thin,
pseudo-parenchymatous covering of the ascocarp, enclosing _one_
(_Podosphæra_ and _Sphærotheca_; compare _Thelebolus_ among the
Hemiasci) or _a few_ asci (Fig. 108 _c_), which do not form
any hymenium, but are irregularly placed. The cells of the
ascocarp-envelope are often prolonged into hair-like appendages.
The ascocarps are developed from the mycelium at places where two
hyphæ cross each other (Fig. 107). At these places two short and
erect hyphæ are produced side by side. The one from the lower hypha
(Fig. 107 _c_) assumes an ellipsoidal shape, and is known as the
_archicarp_ or _ascogone_, while the other (“_pollinodium_”) arches
over the ascogone. From the latter one ascus may be at once developed
(_Sphærotheca_, etc.), or after its division several asci may be
produced, each developed from one division. The sterile hypha (termed
“pollinodium,” since it was formerly, but erroneously, supposed to
fertilise the ascogone) produces a number of branches, and forms the
pseudo-parenchymatous envelope of one cell in thickness, enclosing the
asci.

  [Illustration: FIG. 108.--_Erysiphe communis._ A small portion
  of a leaf with this Fungus growing upon it (considerably
  magnified). The hyphæ b and d do not belong to this Fungus, but
  are reproductive organs of a pyrenomycetous Fungus parasitic upon
  it (_Cicinnobolus_).]

Many plants, both cultivated and wild, are attacked by various species
of Mildew. A common means of prevention against their attacks is to
dust the diseased parts with sulphur.

  [Illustration: FIG. 109.--_Eurotium glaucum_: α portion of
  mycelium lying horizontally; β vertically-placed conidiophore;
  the mycelium gives rise to another branch near α; the conidia are
  abstricted from short flask-shaped cells; _b_ a ripe conidium;
  _c_, _d_ germinating conidia; _e_ spirally-twisted hypha,
  commencement of an ascocarp; _f_ a stage later; _g_ still later,
  the hypha at the base of the coil has given off branches which
  are applied to it; _h_, _i_ sections of young ascocarps.]

   _Sphærotheca pannosa_ occurs on the leaves of Roses, and on the
   fruit of Peaches and Apricots. _S. castagnei_ on _Humulus_,
   _Cucumis_, etc.--_Erysiphe tuckeri_ grows on the leaves and
   fruit of the Vine; it spins its hyphæ over the bunches of
   grapes, curtails their growth, and causes them to burst, and
   to become decayed and rotten (Grape-disease). The Fungus was
   first noticed in England in 1845, and later was found in
   all countries where grapes are grown. It is only known in
   the conidial form (“Oidium tuckeri”). Many other species of
   _Erysiphe_ are found on herbaceous plants.--_Microsphæra_ has
   appendages which are repeatedly forked at their extremities.
   _M. grossulariæ_ on _Ribes grossularia_.--_Uncinula_ has
   appendages with spirally-coiled extremities; on _Salix_ and
   _Acer_.--_Phyllactinia_ has a circle of bristle-like appendages
   with dilated bases. _P. guttata_ on _Corylus_, _Fraxinus_,
   _Fagus_, etc.

Order 2. =Perisporiaceæ=, Moulds and Mildews. A group of Fungi
widely distributed and found in all situations. Usually they have a
well-developed surface mycelium, and small, round, seldom conspicuous
ascocarps, containing ovoid, pulley-like spores. They are partly
saprophytic, partly parasitic, in the latter condition having a brown
mycelium.

  [Illustration: FIG. 110.--_Eurotium glaucum_: _a_ longitudinal
  section of a half-ripe ascocarp, bounded externally by a
  well-defined layer of cells, enclosing asci in various stages of
  development; _b_ a semi-ripe, _c_ an almost ripe ascus; _d_ and
  _e_ spores seen from the edge and side; _f_ germinating spore
  twenty-two hours after been sown in plum juice.]

_Eurotium glaucum_ (= _E. herbariorum_, Figs. 109, 110) and _E. repens_
live on dead organic matter, preserved fruits, etc. The conidial forms
of both species are known as “Moulds” (Fig. 109), and formerly were
described under the name “_Aspergillus glaucus_.” The conidia for some
time remain attached to each other in chains (Fig. 109 _a_); they are
abstricted from sterigmata arranged radially on the spherical, swollen
end of the conidiophore. The small yellow or brownish ascocarps are
frequently found in herbaria, especially when the specimens have
been insufficiently dried. _Aspergillus fumigatus_ and others are
pathogenic, causing mycosis in warm-blooded animals.

  [Illustration: FIG. 111.--_Penicillium crustaceum_: _a_ conidia
  (× 300); _b_ germination of conidia; _c_ small portion of
  mycelium, produced from a conidium at *, with five conidiophores;
  _d_ young conidiophore (× 630), a flask-shaped cell is
  abstricting a conidium; _e_ the same conidiophore after 9–10
  hours.]

  [Illustration: FIG. 112.--_Penicillium crustaceum_: _a_ two
  spirally-coiled hyphæ arise from the mycelium, from one of
  which (archicarp) the asci are produced; _b_ a further step in
  the development of the ascocarp; the branching archicarp is
  surrounded by sterile hyphæ; _c_ section of young ascocarp;
  the larger hyphæ in the centre are the ascogenous hyphæ; these
  are enclosed by a pseudo-parenchyma of sterile hyphæ (× 300);
  _d_ series of ripe asci with spores; _e_ four ascopores seen
  laterally; _f_ germinating ascospores (× 800).]

_Penicillium crustaceum_ (_P. glaucum_, Figs. 111, 112) is an
exceedingly common “Mould.” Its mycelium appears very frequently on
any organic matter which is permitted to remain untouched, and soon
covers it with a dense mass of blue-green conidiophores. These branch
at their summits and bear flask-shaped cells from which the conidia
are abstricted. The ascocarps which, both in size and colour, resemble
grains of sand, have only been obtained in luxuriant cultivation with a
limited supply of oxygen.

   _Capnodium salicinum_ (_Fumago salicina_, _Cladosporium
   fumago_), a common Mildew, forms dark overgrowths on the leaves
   and branches of various shrubs (Poplars, Elms, Willows) and on
   Hops. The conidia appear in various forms, as on conidiophores,
   in conidiocarps with large multicellular conidia, and in
   conidiocarps with small unicellular conidia; in nutritive
   solutions yeast-like conidia are also developed.--_Apiosporium
   pinophilum_ produces mildew on the leaves of _Abies alba_ and
   _Picea excelsa_. (The conidial-forms were formerly described as
   “_Antennaria pinophila_”).

Order 3. =Tuberaceæ, Truffles.= The Fungi belonging to this order
are entirely subterranean. The mycelium is filamentous, and partly
parasitic upon the roots of plants, especially trees, in its
neighbourhood; it is then known as _Mycorhiza_. The fruit-body is
relatively large, in some cases about the size of a hen’s egg.
Internally it is traversed by a number of winding passages (Fig. 113
_a_), the walls of which are coated with the asci. The asci (_b_)
contain only a small number of spores, and these are set free by the
putrefaction of the fruit-body. Conidia are unknown.

  [Illustration: FIG. 113.--_Tuber melanosporum_: _a_ fruit-body
  (nat. size), a portion having been removed to show the internal
  structure; _b_ an ascus with ascospores.]

   _Tuber melanosporum_, _T. brumale_, _T. æstivum_, and other
   species are edible. _Terfezia leonis_ and _Choiromyces
   mæandriformis_ are also edible. The Truffles are always found in
   woods and under trees, and disappear when these are destroyed.
   France and Italy produce the best and the largest number of
   Truffles, which are hunted by specially trained dogs and pigs.

   In _Elaphomyces_ (Stag-Truffle) the fruit-body has a corky
   external layer, and is inedible. Some of the species are found
   in this country. _E. granulatus_ is parasitic on the roots of
   the Fir.


                      Family 3. =Pyrenomycetes.=

In this family the hymenium is enclosed in small fruit-bodies,
_perithecia_ (Fig. 120 _b_), which appear to the naked eye as small
dots. In shape they resemble a globe or a flask with a narrow mouth,
through which the spores are ejected (peronocarpic ascocarps).
Different kinds of reproduction--conidia, pycnidia (chiefly with
microconidia), chlamydospores, and perithecia--are found in the same
species. The various stages in the life-history of these Fungi are so
dissimilar, that formally they were considered to be different genera.
Ergot furnishes a very good example.

  [Illustration: FIG. 114.--A small portion of an ovary attacked
  with _Claviceps purpurea_ (_Sphacelia_).]

  [Illustration: FIG. 115.--An ovary with the conidial stage of
  _Claviceps purpurea_ (_Sphacelia_).]

This family may be subdivided into 3 sub-families.


                     Sub-Family 1. =Hypocreales.=

The perithecia are _pale, fleshy, brightly coloured_, and generally
aggregated on a stroma. Conidia and chlamydospores occur very
frequently. Only one order.

Order. =Hypocreaceæ.= In this order the majority are parasites upon
Flowering-plants (_Nectria_, _Polystigma_, _Epichloë_, _Claviceps_);
but some are parasites upon Fungi (_Hypomyces_, _Melanospora_), or upon
insects (_Cordyceps_).

  [Illustration: FIG. 116.--_Claviceps purpurea. A_ Sclerotium
  with stromata (_cl_) (× by 2). _B_ Stroma divided longitudinally
  to show the perithecia (_cp_). _C_ A perithecium with the
  surrounding hyphæ (_hy_). _D_ An ascus ruptured, with the eight
  filamentous ascospores emerging.]

The most important member of this order is the ERGOT (_Claviceps
purpurea_, Figs. 114, 115, 116). This Fungus is found in the flowers of
many species of Grasses, especially the Rye, attacking and destroying
the ovaries. In the FIRST or CONIDIAL STAGE of the attack, the ovaries
are found covered with a white, irregularly folded mycelium (Fig. 114
_m_, Fig. 115), formed of numerous hyphæ woven together and penetrating
the wall of the ovary. From these a number of hyphæ (Fig. 114 _a_)
project into the air and abstrict from their apices the conidia (_b_)
which serve as reproductive organs. The mycelium also secretes a
sticky, stinking fluid (honey-dew) in which the conidia are embedded
in great numbers. The honey-dew exudes from the bases of the glumes,
and is greedily sought by flies, which thus carry the conidia to
other ovaries. In this manner fresh ears are infected, which might
escape were the conidia only distributed by the wind. This stage
formerly was regarded as an independent Fungus, known as _Sphacelia
segetum_ (Fig. 115). On germination, the conidia produce either a new
mycelium (Fig. 114 _d_, _c_), or new conidia. The SECOND or SCLEROTIUM
STAGE is the one in which the Fungus passes the winter. The mycelium
penetrates deeper and deeper into the attacked ovaries, their tissues
are destroyed and replaced by the hyphæ, which gradually become more
and more felted together. A firm, pseudo-parenchymatous mass of hyphæ
is thus formed at the base of the loosely-woven _Sphacelia_, which is
in part transformed into the hard sclerotium, and the remainder thrown
off. A dark, hard, poisonous body, longer than the natural grain,
is thus formed; these bodies are known as Ergots, and were formerly
considered to be a distinct species,--_Sclerotium clavus_ (“Secale
cornutum,” Ergot, Fig. 116 _A_, _c_). The THIRD STAGE, described as
_Claviceps purpurea_, is developed in the following spring from the
germinating sclerotium, which produces dark-red stromata with short
stalks. In the stroma numerous perithecia with asci and ascospores are
produced. The latter may infect young flowers of the cereals, in which
the disease is then developed as before.

  [Illustration: FIG. 117.--_Nectria cinnabarina_: _a_ branch of
  _Acer pseudoplatanus_, with conidial-layers and perithecia (nat.
  size); _b_ a conidial-layer (_Tuberculoria vulgaris_); _c_, a
  mass of perithecia. (_b_ and _c_ × 8.)]

   Several species of the genus _Nectria_, with blood-red
   perithecia, are found as dangerous parasites, especially _N.
   ditissima_, which causes “Canker” in the Beech, Ash, and Apple,
   etc.; _N. cucurbitula_, which appears on Pine-trees, and _N.
   cinnabarina_ (Fig. 117), whose conidial form was formerly named
   _Tubercularia vulgaris_.--_Polystigma rubrum_ forms shining
   red spots on the green leaves of _Prunus_-species.--_Epichloë
   typhina_ is parasitic on the sheaths of Grasses, on which it
   first forms a white conidial-layer, later on a yellow layer of
   perithecia.--_Cordyceps_ (Chrysalis Fungus, Figs. 118, 119)
   lives in and destroys insects, and after compassing their death
   produces the club-formed, generally yellow, stromata, one part
   of which bears conidia (_Isaria_) and another perithecia. _C.
   militaris_ (Fig. 118) on the chrysalides and caterpillars of
   moths, is the most common.

   The so-called _Botrytis bassiana_, which produces the disease
   known by the name of “Muscardine,” in silkworms, is probably a
   conidial form belonging to _Cordyceps_.

  [Illustration: FIG. 118.--_Cordyceps militaris._ I Stromata with
  conidiophores (_Isaria farinosa_). II A larva, with stromata,
  bearing perithecia. III A spore.]

   [Illustration: FIG. 119.--_Cordyceps robertii_ on the larva of
  _Hepialus virescens_: _a_ stalk of stroma; _b_ perithecia.]


                      Sub-Family 2. =Sphæriales.=

To this sub-family belong the majority of the Pyrenomycetes. The
perithecia are of a _firm consistence_ (tough, leathery, woody or
carbonaceous), and of a _dark_ colour. Their _covering_ is _quite
distinct from the stroma_ when this structure is present. The
stromata are sometimes very large, and may be either cushion-like,
crustaceous, upright and club-like, or branched bodies. In general,
small, inconspicuous Fungi, living on dead vegetable matter, sometimes
parasites. Free conidiophores and conidiocarps are known in many
species, and in several, chlamydospore-like forms of reproduction.
Orders 3–18 constitute the Sphæriaceæ of older systematists.

  [Illustration: FIG. 120.--_Strickeria obducens_: _a_ a portion
  of an Ash-branch with the bark partly thrown off; on the wood
  are numerous black perithecia (× 20); _b_ longitudinal section
  through a perithecium; _c_ a spore; _d_ longitudinal section
  through a pycnidium whose ascospores are being ejected; _e_
  portion of the same, with hyphæ and spores.]

Order 1. =Sordariaceæ.=--Fungi living on dung with fragile perithecia,
either aerial or buried in the substratum. The dark brown or black
spores have either a mucilaginous envelope (_Sordaria_, etc.) or
mucilaginous appendages (_Podospora_), by means of which their
expulsion and distribution are promoted.

Order 2. =Chætomiaceæ.= Perithecia fragile, free, bearing on the summit
a tuft of hairs. _Chætomium_, on decaying vegetable matter.

Orders 3–7. _Perithecia scattered or aggregated, situated from the
commencement on the surface of the substratum. Stroma wanting._

Order 3. =Trichosphæriaceæ.= _Trichosphæria parasitica_ (Fig. 121),
on _Abies alba_; _Herpotrichia nigra_ on _Picea excelsa_ and _Pinus
montana_.

  [Illustration: FIG. 121.--_Trichosphæria parasitica_: _a_ a
  twig of _Abies alba_, with epiphytic mycelium; _b_ a leaf with
  mycelium and sporangia (magnified); _c_ a sporangium (× 60); _d_
  an ascus with spores (× 550).]

Order 4. =Melanommaceæ.= _Rosellinia quercina_ lives in the roots of
1–3-year-old Oaks, and destroys the plants.

Order 5. =Ceratostomaceæ.=

Order 6. =Amphisphæriaceæ.= _Strickeria obducens_ (Fig. 120) has
brick-like spores, and lives aggregated on the hard branches of
_Fraxinus_.

Order 7. =Lophiostomaceæ.=

Order 8. =Cucurbitariaceæ.= Perithecia tufted, _at first embedded, then
breaking through_, often situated upon an indistinct _stroma_.

Orders 9–13. _The perithecia remain embedded, and are only liberated
by the casting off of the covering layers of the substratum. Stroma
wanting._

Order 9. =Sphærellaceæ.= The species of _Sphærella_ have colourless,
bicellular spores. They live upon the leaves of many plants, and
develope spherical perithecia upon the fallen leaves.

Order 10. =Pleosporaceæ.= The conidial-forms of _Pleospora herbarum_
and _P. vulgaris_ form a black covering on various plants, known as
“smuts.”--_Venturia ditricha_ occurs on the underside of dry Birch
leaves, and perhaps to this belongs the conidial-form, _Fusicladium
pirinum_, which causes the “Rust spots” on Apples and Pears.

Order 11. =Massariaceæ.=

Order 12. =Clypeosphæriaceæ.=

Order 13. =Gnomoniaceæ.= Perithecia, with peak-like aperture. _Gnomonia
erythrostoma_ in the leaves of _Prunus avium_, which turn brown and do
not fall in autumn.

Orders 14–18. _Stroma generally well developed. The perithecia
are embedded in the stroma, but when this is rudimentary, in the
substratum._

Order 14. =Valsaceæ.= _Valsa._

Order 15. =Diatrypaceæ.= _Diatrype._

Order 16. =Melanconidaceæ.=

Order 17. =Melogrammataceæ.=

Order 18. =Xylariaceæ.= This order is the most highly developed of the
Sphæriales. The _stroma_ arises on the _surface of the substratum_,
which is generally dead or decorticated wood; it is well-developed,
crustaceous, hemispherical or upright. In the younger conditions
it is covered with a layer of conidia, and later on it bears the
_perithecia_, arranged in a layer immediately _beneath its surface_.
The ascospores are of a dark colour. Often also there are free
conidiophores.

  [Illustration: FIG. 122.--_Xylaria hypoxylon_ (nat. size) on a
  tree stump: _a_ younger, _b_ an older stroma, both of which, with
  the exception of the black lower portion, are covered with white
  conidia; _n_, spot where the perithecia are developed; _c_ an
  old stroma with upper part fallen off; _d_, _e_ large branched
  stromata; _k_ conidia.]

   _Hypoxylon_ and _Ustulina_ have a cushion-like
   or crustaceous stroma.--_Xylaria_ has a club-shaped
   or branched stroma, often several centimetres high. _X.
   hypoxylon_ (Fig. 122) and _X. polymorpha_ occur on old
   tree stumps.--_Poronia_ grows on old horse dung, and has a
   conical stroma.


                     Sub-Family 3. =Dothideales.=

The _perithecia_ are always embedded in a _black stroma_, and are _not
distinctly separated_ from it. The accessory forms of reproduction are:
conidiophores, conidiocarps, and yeast-like conidia. The majority are
parasites. One order.

   Order =Dothideaceæ=. _Phyllachora graminis_ produces scab-like
   patches on the leaves of the Grasses.--_Scirrhia rimosa_ grows
   on the leaf-sheathes of _Phragmites_.--_Rhopographus pteridis_
   on _Pteridium aquilinum_.


                       Family 4. =Hysteriales.=

This family, like the following, has hemiangiocarpic ascocarps
(_apothecia_). These are closed in the early stages, but when ripe
_open_ in a _valvular manner_ by a _longitudinal fissure_; they
are black, oblong, and often twisted. Some species are parasites,
especially upon the Coniferæ.

  [Illustration: FIG. 123.--_Lophodermium (Hypoderma)
  nervisequium_: _a_ two leaves of _Abies alba_ seen from above
  with pycnidia; _b_ a leaf seen from the underside with apothecia;
  _c_ an ascus with ascospores. (× 500.)]

  [Illustration: FIG. 124.--Three leaves of the Red-pine with
  _Lophodermium macrosporum_: _a_ under side of the leaves with
  apothecia; _b_ a leaf from upper side with pycnidia. (× about 2.)]

  [Illustration: FIG. 125.--_Lophodermium pinastri_: _a_ leaves of
  _Pinus sylvestris_ with apothecia (nat. size); _b_ two paraphyses
  and an ascus with filamentous spores.]

Order 1. =Hysteriaceæ.= _Hysterium pulicare_ upon the ruptured bark of
many trees.

Order 2. =Hypodermaceæ.= The species of _Lophodermium_ live upon the
leaves of Conifers, and are the cause of their falling off (_blight_).
_L. pinastri_ (Fig. 125), on the leaves of _Pinus_ and _Picea_; the
leaves become red-brown and fall off; at first conidiocarps are formed,
and later apothecia; _L. nervisequium_ (Fig. 123), on _Abies alba_;
_L. macrosporum_ (Fig. 124), on _Picea excelsa_; _L. brachysporum_, on
_Pinus strobus_.

Order 3. =Dichænaceæ.=

Order 4. =Acrospermaceæ.=


                       Family 5. =Discomycetes.=

The ascocarps (_apothecia_) are at first closed, and _only open_ at
the time of their ripening, not valvularly, but more or less like a
_saucer_ or _cup_, so that the hymenium lies exposed on their upper
surface. In the first three sub-families, and generally also in the
fourth, the apothecia are formed inside the substratum. The apothecia
are, in contrast to the Pyrenomycetes, light and brightly coloured,
and their size varies very much, and may be several centimetres in
diameter. Paraphyses are often present between the asci; they often
contain colouring matter, and give to the disc its characteristic
colour. The tissue on which the asci are borne is known as the
_hypothecium_. The shape and colour of the spores is not so varied as
in the Pyrenomycetes. The accessory forms of reproduction are conidia
(sometimes of two forms), chlamydospores, and oidia. The family is
divided into 5 sub-families.


                     Sub-Family 1. =Phacidiales.=

The apothecia are developed in the interior of the substratum, which
they break through, and in general dehisce apically. The envelope is
tough and black. Hypothecium inconspicuous; hymenium flat.

   Order 1. =Euphacidiaceæ.= _Phacidium abietinum_, on the leaves
   of _Abies alba_.--_Rhytisma_; the pycnidia are found in the
   summer on the green leaves, while the apothecia are developed
   on the fallen leaves and dehisce in the following spring. _R.
   acerinum_ causes black spots on the leaves of the Sycamore, and
   _R. salicinum_ on Willows.

   Order 2. =Pseudophacidiaceæ.=


                     Sub-Family 2. =Stictidales.=

The apothecia when ripe break through the substratum which forms a
border round them. Hymenium generally saucer-shaped.

   Order 1. =Stictidaceæ.= _Stictis._

   Order 2. =Ostropaceæ.= _Ostropa._


                     Sub-Family 3. =Tryblidiales.=

The apothecia are embedded in the substratum in the early stages, and
then are raised high above it. Hypothecium thick. Hymenium cup-shaped.

   Order 1. =Tryblidiaceæ.= _Tryblidium._

   Order 2. =Heterosphæriaceæ.= _Heterosphæria patella_
   on the dead stalks of Umbellifers.


                     Sub-Family 4. =Dermateales.=

The apothecia in the early stages are embedded in the substratum and
then break through it, or are from the first situated on the surface of
the substratum. Hypothecium thick.

   Order 1. =Cenangiaceæ.= _Cenangium._

   Order 2. =Dermateaceæ.= _Dermatea._

   Order 3. =Patellariaceæ.= _Patellea_,
   _Biatorella_, _Patellaria_.

   Order 4. =Caliciaceæ.= _Calicium_, _Coniocybe_, etc., on the
   bark of trees.

   Order 5. =Arthoniaceæ.= _Arthonia_ on the bark of several trees.
   _Celidium stictarum_ on the apothecia of _Sticta pulmonaria_.

   Order 6. =Bulgariaceæ.= Apothecia gelatinous under moist
   conditions, and horny when dried.--_Calloria fusarioides_; the
   red apothecia break out in the spring on the dried stalks of
   _Urtica dioica_; a gelatinous reproductive form of the Fungus is
   found before the apothecia, which consists of oidia (formerly
   described as “_Dacryomyces urticæ_”).--_Bulgaria inquinans_ on
   the living or fallen trucks of Oaks and Beeches.

  [Illustration: FIG. 126.--_Botrytis cinerea_: _a_ slightly
  magnified; _b_ more highly magnified; _c_ germinating conidium.]

  [Illustration: FIG. 127.--_Sclerotinia fuckeliania_: _a_
  sclerotium with conidiophores; _b_ with apothecia; _c_ section
  through sclerotium and apothecium; _d_ ascus with eight
  ascospores. (× 390.)]


                      Sub-Family 5. =Pezizales.=

_The apothecia are developed on the surface of the substratum and
are waxy or fleshy_; at the commencement closed, and covered with a
saucer- or cup-shaped, seldom flat, hymenium. The _hypothecium_ is
generally well developed. This sub-family is the richest in species of
the Discomycetes and contains forms of very different habit. They grow
upon dead wood, upon the ground, and upon dung. A few are parasites.

Order 1. =Helotiaceæ.= Apothecia with waxy envelope of colourless,
or yellowish prosenchymatous cells.--~_Chlorosplenium æruginosum_
is found on decaying wood (particularly Oak and Birch), to which it
gives a green colour. _Sclerotinia_ has sclerotia which are developed
upon the host-plant and from which, after a period of rest, the long,
brown-stalked apothecia arise. _S. ciborioides_ (_S. trifoliorum_,
Fig. 128) is parasitic on Clover; _S. sclerotiorum_, on _Daucus_-roots,
_Phaseolus_, etc.; _S. baccarum_, on the berries of _Vaccinium
myrtillus_; “_Botrytis cinerea_” is a common parasite and is probably
the conidial form of _S. fuckeliania_ (Fig. 127).--_Helotium herbarum_
lives on dry plant stems.--_Dasyscypha willkommii_ (Fig. 129) produces
Larch-canker on the bark of the Larch.~

  [Illustration: FIG. 128.--_Sclerotinia ciborioides_: _a_
  sclerotium with three apothecia slightly magnified; _b_ ascus
  with eight ascospores; _c_ germinating ascospore.]

  [Illustration: FIG. 129.--_Dasyscypha willkommii_: _a_ portion of
  bark of _Larix decidua_ with sessile, cup-shaped apothecia (nat.
  size); _b_ two paraphyses on either side of an ascus with eight
  ascospores.]

  Order 2. =Mollisiaceæ.= _Mollisia cinerea_, principally on
  decaying wood.

Order 3. =Pezizaceæ.= This order contains the largest and
morphologically the highest forms of the _Discomycetes_. Apothecia
fleshy, and in the later conditions generally saucer-shaped.

   _Peziza_, with sessile apothecia, growing on the ground;
   _P. cochleata_ is brown, and coiled like a snail-shell; _P.
   coccinea_ is scarlet; _P. aurantia_ occurs as an orange-coloured
   expansion on the ground.

   Order 4. =Ascobolaceæ.= Apothecia fleshy; in the later stages
   flat or convex. The asci are, comparatively speaking, large,
   and often contain a great number of spores which escape by the
   casting off of a lid on the summit of the ascus. Generally
   living on dung.--_Ascobolus furfuraceus_, etc.


                       Family 6. =Helvellales.=

These Fungi have the appearance of clubs, bells, or mushrooms,
consisting of an upright _stalk_ bearing a _large and fleshy_ head, on
the _exterior surface_ of which the _hymenium_ is spread. The ascocarps
are probably gymnocarpic from the beginning, and on this account
these plants are placed in a separate family. The development of the
ascocarps is unknown. The _Morchella_ (Morell) grows on the ground;
some species are edible. 1 order.

   Order. =Helvellaceæ.= _Spathulea_ is yellow and club-shaped,
   and forms “fairy rings” in woods.--_Geoglossum_ (Earth-tongue)
   projects above the ground as a black tongue, or as a
   club-shaped body. Several species are found in meadows and
   on heaths.--_Helvella_ has a stalk, bearing an irregularly
   folded head, on the external surface of which is the
   hypothecium.--_Morchella_ (Morell, Fig. 130), the stalk bears on
   its summit the conical or spherical head, the external surface
   of which is reticulate and bears the asci.--_Mitrula. Verpa._

  [Illustration: FIG. 130.--_Morchella esculenta_: _a_ an entire
  specimen, about one half natural size; _b_ longitudinal section
  through the head.]


                     APPENDIX TO THE ASCOMYCETES:


        Family 7. =Ascolichenes (Lichen-forming Ascomycetes).=

The Lichens were formerly classed among the Thallophyta as a group
quite distinct from the Algæ and Fungi. Investigations during the last
twenty-five years, however, have conclusively proved that the Lichens
are Fungi which reproduce in the same manner as the Ascomycetes, or,
more rarely, the Basidiomycetes, and have entered into a peculiar
_symbiotic relation with Algæ_, especially the Cyanophyceæ and
Protococcoideæ, with which they associate, and without which they
would be unable to exist. The Fungus forms the largest portion of the
Lichen, enclosing the Alga with which it may be said to be commensal.
The Fungus especially produces reproductive bodies and absorbs the
inorganic nourishment through the rhizoids, whilst the Alga supplies
it with the organic materials. In consequence of this the Lichens, in
contradistinction to other Fungi, need light for the development of
their nutritive organs, and are therefore, in any case internally, of
a more or less greenish colour. The form and condition of the thallus
is unusual among the Fungi, and they can grow upon rocks and in other
places where no dead organic matter, such as would be required by other
Fungi, is obtainable.

  [Illustration: FIG. 131.--Transverse section through the thallus
  of _Sticta fuliginosa_ (× 500): _r-r_ rhizoid-strands, which
  arise from the under side; _g-g_ gonidial layer; _m_ medullary
  layer; _o_ upper, _u_ lower cortex.]

Two cellular forms are therefore to be found in each Lichen:

1. The cells which belong to the Fungus. These are generally septate,
branched _hyphæ_ without any trace of chlorophyll. In the thallus of
the majority of Lichens there may be found a medullary layer (Fig.
131 _m_) of loosely-woven hyphæ, between which there are large air
chambers; and an _external layer_ (cortex) (Fig. 131 _o_, _u_) formed
of closely-woven hyphæ without any intercellular spaces. In some
Lichens (Collemaceæ) the hyphæ wind about in the thallus, being equally
distributed throughout, without forming any decided strata. These
Lichens moreover become gelatinous when exposed to moisture (Fig. 132),
on account of the swelling of the walls of the Algæ. The hyphæ contain
protoplasm with drops of oil, but never starch; their walls easily
swell when exposed to damp after having been dried, and in some (_e.g._
_Cetraria islandica_) they become gelatinous when cooked. Certain
strata of hyphæ become blue on treatment with iodine alone, from which
it is inferred that the wall is allied, in its chemical nature, to
starch.

2. The enclosed Algæ, termed “gonidia.” Some belonging to the
Cyanophyceæ, Protococcoideæ, (especially _Pleurococcus_) and
Chroococcaceæ, are spherical and are found isolated, or in irregular
_groups_ of cells (Fig. 131 _g_); some belonging to _Nostoc_ (Fig. 132
_g_), Lyngbyaceæ, etc., are placed in cell-rows. Each Lichen, as a
rule, has only one definite Algal-form for its gonidium.

The gonidia either lie together in a certain stratum between the
cortex and the medullary layer (Fig. 131 _g_), or are scattered
irregularly throughout the entire thallus (Fig. 132). The thallus is
in the first instance termed “heteromerous,” in the second instance,
“homoiomerous.” The Fungal-hyphæ embrace the gonidia and apply
themselves closely to, or even penetrate them, and hence it has been
difficult to decide whether the one cellular form does or does not
develop from the other (Figs. 134, 135).

   This theory regarding the symbiosis of Fungi and Algæ to form
   a Lichen is termed the Schwendenerian theory, after the first
   scientist who advanced it with any weight. It had been already
   indicated by De Bary, and further arguments in its support have
   at a later time been adduced by Bornet, Stahl, Treub, Frank,
   Bonnier, Alfr. Möller and others.

  [Illustration: FIG. 132.--_Collema microphyllum._ Transverse
  section through the thallus; _g Nostoc_-chains; _h_ hyphæ.]

  [Illustration: FIG. 133.--_Ephebe pubescens._ The apex of a
  branch of the thallus with two lateral branches (_s_): _h_ its
  hyphæ; _g_ the apical gonidium of the main branch.]

  [Illustration: FIG. 134.--_Nostoc lichenoides_, which is attached
  by a germinating thread (_h_) of _Collema glaucescens_.]

  [Illustration: FIG. 135.--_A_ Germinating spore of _Physcia
  parietina_ with _Protococcus viridis_. _B Synalissa symphorea_
  with _Glæocapsa_. _C Cladonia furcata_ with _Protococcus_.]

The thallus of the Lichen appears mainly under three forms:--

1. The CRUSTACEOUS, which adheres firmly to the substratum (bark,
stone) throughout its entire surface, without being raised into any
free patches or lobes. It has, in many instances, no definite outline,
and hyphal-branches from it often penetrate deeply into the substratum.
It grows at the circumference and sometimes dies away in the centre
(Figs. 138, 139, 140).

2. The FOLIACEOUS. This also lies flat upon the substratum, but is not
firmly attached to and has a definite outline. It grows at the margin,
and raises itself a little by free outgrowths and lobes (Fig. 141). The
rhizoid-strands spring out from its whitish under surface (Fig. 131,
_r_).

  [Illustration: FIG. 136.--Portion of a hymenium: _d_ a thin
  stratum on which the asci (_s_) are situated.]

  [Illustration: FIG. 137.--Spores of, _a Cladonia_, _Lecanora_
  and _Pertusaria_; _b Bæomyces_; _c Sphinctrina_; _d_, _e_,
  _f_ various species of _Parmelia_; _g_, _h Verrucaria_ in its
  younger and older condition; _i_, _k_ species of _Leptogium_.]

3. The FRUTICOSE, which is attached to its substratum at a small point
from which it projects freely, either erect or pendulous. It is more
or less tufted, in the form of a bush (Figs. 142, 143). These three
thallus-forms gradually pass over by many intermediate forms into one
another.

  [Illustration: FIG. 138.--_Lecanora subfusca_: _a_ the bark on
  which it is situated; _l_ the thallus; _s_ the ascocarp; _s’_ an
  ascocarp.]

  [Illustration: FIG. 139.--_Graphis_ (two species).]

  [Illustration: FIG. 140.--_Pertusaria communis._]

The Lichens, like other Ascomycetes, have very variously constructed
ascospores (Fig. 137), which are enclosed in asci (Fig. 136), usually
surrounded by paraphyses attached together. Furthermore they possess
pycnidia (Fig. 141) containing numerous microconidia. These were
formerly considered as organs of fructification, and were termed
“spermatia,” and the pycnidia, “spermogonia.” Alfr. Möller proved,
in 1887, that the microconidia are able to germinate and produce a
mycelium with new conidia, just as in other Ascomycetes.

VEGETATIVE REPRODUCTION takes place by _soredia_, which to the naked
eye appear as whitish powder on the surface of the thallus. They are
small round bodies, formed by one or a group of gonidia, which are
surrounded by a mass of felted hyphæ. After the rupture of the cortex
they are set free, and readily carried by the wind to other places,
where under favourable circumstances they establish a new thallus.

  [Illustration: FIG. 141.--_A_ A portion of the thallus of
  _Parmelia parietina_ with ascocarps (_a_) and pycnidia (_b_). _B_
  A portion of the thallus of _Cetraria islandica_ with pycnidia
  at the end of small lobes. _C_ A lobe with pycnidia and ejected
  microconidia. (Magnified).]

GEOGRAPHICAL DISTRIBUTION. The Lichens are the most hardy plants, and
are the first to appear on hitherto bare rocks which they gradually
disintegrate, and hence prepare the way for the growth of other plants.
They are to be found from the Polar regions to the Equator; from the
highest snow-free mountain-peaks down to the level of the sea; on the
stems of trees; on rocks, soil, some even on inundated places; on
stones in woodland streams, and on beaches; but they are never found
upon rotten organic remains. Some grow gregariously in enormous masses,
and form wide-stretching carpets, _e.g._ Reindeer Moss (_Cladonia
rangiferina_), species of _Cetraria_ and other fruticose Lichens.

USES. On account of the cell-wall being composed of Lichenstarch
(Lichenin), the Iceland-Lichen and Manna-Lichen (_Lecanora esculenta_)
are used as food; the latter grows on stones, in the deserts of Asia
and North Africa, and is often torn loose in large masses and carried
away by the wind. The Reindeer-Lichen is not only the principal food of
the reindeer, but it is also used in the manufacture of Danish brandy.
_Cetraria islandica_ (Lichen islandicus) is OFFICINAL. Colouring
materials (lacmus, orseille, persio) are made from several species,
especially from _Roccella tinctoria_ (from the rocky coasts of the
Mediterranean). _Parmelia saxatilis_ and particularly _Lecanora
tartarea_ are used for colouring purposes in the Northern countries.

About 2,000 species of Lichens have been described. If we disregard the
Basidiolichenes, which will be considered on page 176, the remaining
Lichens (Ascolichenes) may be divided into the two following orders
according to the structure of the fruit-bodies:--

Order 1. =Pyrenolichenes.= The ascocarps (apothecia) are spherical or
flask-shaped, as in the Pyrenomycetes, more rarely linear (_Graphis_).

   According to the nature of the thallus, these Lichens may be
   divided into:--

   _a._ Thallus homoiomerous, but not gelatinous, branching
   according to the mode of growth of the Algæ: _Ephebe_ (Fig.
   133), with Algæ of the genus _Stigonema_.

   _b._ Thallus homoiomerous, gelatinous: _Lichina_.

   _c._ Thallus heteromerous, crustaceous: _Verrucaria_,
   _Pyrenula_; _Graphis_ (Fig. 139), which may be considered as
   Hysteriaceæ with gonidia; several species of _Graphis_ are
   common on bark.

   _d._ Thallus heteromerous, foliaceous: _Endocarpon_.

   _e._ Thallus heteromerous, fruticose: _Sphærophorus_.

Order 2. =Discolichenes.= These, as in the Discomycetes, have open
apothecia, which, as a rule, are cupular, more rarely hemispherical
(_Cladonia_).

   According to the nature of the thallus, these Lichens may be
   divided into:--

   _a._ Thallus homoiomerous, but not gelatinous, branching
   according to the mode of growth of the Algæ: _Cœnogonium_.

   _b._ Thallus homoiomerous, gelatinous: _Collema_ (Fig. 132),
   with Algæ of the genus _Nostoc_; _Leptogium_.

   _c._ Thallus heteromerous, crustaceous: _Pertusaria_ (Fig.
   140), _Lecidea_, with apothecia open from the beginning;
   _Lecanora_, with apothecia, which in the beginning are closed,
   later on open, but with a rim formed by the thallus (Fig. 138);
   _Bæomyces_, whose apothecia are borne on a stem formed by the
   thallus.

   _d._ Thallus heteromerous, foliaceous: _Parmelia_ (_P.
   saxatilis_; _P. parietina_, Wall-Lichen, Fig. 141, is yellow,
   very frequent on tree-stems, stone-walls, tiles); _Physcia_ (_P.
   ciliaris_, frequent on tree-stems); _Sticta_ (_S. pulmonacea_,
   Lung-Lichen, on tree-stems); _Peltigera_, especially on the Moss
   among trees; _Umbilicaria_, on rocks.

   _e._ Thallus heteromerous, fruticose: _Cetraria_ (_C.
   islandica_), “Iceland Moss,” with an olive-brown, flat,
   furrowed, fringed thallus, on heaths; _C. nivalis_, white, in
   the Polar regions; _Evernia_, _Ramalina_, _Usnea_ (_U. barbata_,
   Beard-Lichen, Fig. 143); _Roccella_, _Stereocaulon_, _Cladonia_,
   of which the genus _C. rangiferina_, Reindeer-Moss (Fig. 142) is
   important; _Cladonia_ has two kinds of thallus, one scaly and
   leaf-like, the other erect, which bears the apothecia and may be
   fruticose (Fig. 142), or cupular (Fig. 144); they grow in soil
   in forests and on heaths.

  [Illustration: FIG. 142.--_Cladonia rangiferina_: _s_ ascocarp.]

  [Illustration: FIG. 143.--_Usnea barbata_: _s_ ascocarp.
  (Slightly magnified.)]

  [Illustration: FIG. 144.--_Cladonia pyxidata._]


                    Sub-Class 2. =Basidiomycetes.=

This sub-class embraces the most highly developed Fungi, with large
“fruit-bodies,” which in ordinary language we shortly term Funguses,
Toadstools, or Mushrooms.

They have no sporangia, but reproduce only by means of basidiospores,
conidia, chlamydospores and oidia. The chief characteristic of this
sub-class is the _basidium_ (Fig. 145), _i.e._ the conidiophore, which
has a distinctive form, and bears a definite number (generally 4) of
characteristically shaped conidia (basidiospores, Fig. 145 _c_, _d_,
_e_).

  [Illustration: FIG. 145.--Development of spores in _Corticium_.]

The summit of each basidium is produced generally into four conical
points (_sterigmata_, Fig. 145 _b_), from each of which a basidiospore
is abstricted. The basidia may be classified into three principal
groups, each of which accompanies a distinctive conidiophore: 1,
the long, filamentous, _transversely divided_ basidia, with lateral
sterigmata and spores, found in the Uredinaceæ (Figs. 146 _D_, 153),
Auriculariaceæ (Fig. 160 _B_), and Pilacraceæ; 2, the spherical,
_longitudinally divided_ basidia of the Tremellaceæ (Figs. 160 _C d_;
161 iii. iv.); and 3, the ovoid, or cylindrical, _undivided_ basidia of
the Autobasidiomycetes (Figs. 145, 163, etc.); the two last have apical
sterigmata and spores.

   The first two groups are the septate basidia (_protobasidia_),
   of the _Protobasidiomycetes_; while the unseptate basidia
   (autobasidia) of the _Autobasidiomycetes_ are the third group.
   On the formation of the basidiospores, the nucleus of the
   basidium divides into four nuclei, each of which is transferred
   to a spore.

In addition to the basidia, _simple conidiophores_ are also found.
In the Protobasidiomycetes, the simple conidia are very generally
found as accessory methods of reproduction in conjunction with the
basidiospores; but less frequently in the Autobasidiomycetes, _e.g._
among the Dacryomycetes, Tomentellaceæ, _Heterobasidion annosum_.

   The simple conidiophores vary in size, and in the number and
   shape of the conidia; they, however, resemble the basidia,
   and are doubtless an early stage in the development of the
   definitely formed basidia.

Finally, well-defined _chlamydospores_, formed in various ways, appear
in the Basidiomycetes as supplementary reproductive bodies (compare p.
90). Among the Protobasidiomycetes, chlamydospores are at present only
found among the Uredinaceæ, but in various forms; in the majority of
families of the Autobasidiomycetes _oidia_ frequently occur (Fig. 162),
but genuine chlamydospores seldom.

In the same species several of the known forms of reproduction may be
distinguished.

The _mycelium_ is generally composed of white, branched strands,
consisting of numerous felted hyphæ; in some, sclerotia are found.--The
great majority are saprophytes; some (particularly all the Uredinaceæ),
are parasites.


   DIVISIONS OF THE BASIDIOMYCETES.

    Series 1. PROTOBASIDIOMYCETES: partly gymnocarpic, partly
                angiocarpic.
      „    2. AUTOBASIDIOMYCETES.
                Family 1. DACRYOMYCETES: gymnocarpic.
                  „    2. HYMENOMYCETES: partly gymnocarpic, partly
                            hemiangiocarpic.
                  „    3. PHALLOIDEÆ: hemiangiocarpic.
                  „    4. GASTEROMYCETES: angiocarpic.
      Appended. BASIDIOLICHENES: Lichen-forming basidiomycetes.


                   Series I. =Protobasidiomycetes.=

To this series belong the lowest of the Basidiomycetes. The _basidia_
appear in two principal forms (1 and 2 on page 144) and are _divided_
into four cells, either transversely or longitudinally, each division
forming a sterigma which abstricts a basidiospore. The first three
orders, Uredinaceæ, Auriculariaceæ, and Tremellaceæ have _gymnocarpic_
fruit-bodies, while those of the Pilacraceæ, on the contrary, are
_angiocarpic_.

Order 1. =Uredinaceæ (Rusts).= All the Rust-Fungi are parasites, their
mycelium living in the interior of the stems and leaves of their
hosts, causing red, brown, or black spots--hence their name--and
malformations, sometimes of considerable size.

The Rust-Fungi are gymnocarpic and destitute of a hymenium; for these
reasons they are regarded as the simplest order of the Basidiomycetes.
They are entirely parasitic, and their filamentous, branched mycelium
ramifies in the intercellular spaces of its host, and often protrudes
haustoria into the cells. The mycelium is perennial should it enter a
woody tissue; it may also hibernate in the rhizomes of perennial herbs
and permeate the shoots springing from them, but in the majority of
the Rust-Fungi the mycelium has a very limited growth. The chief means
of reproduction of the Rust-Fungi are the _chlamydospores_, which in
the more highly developed species occur in three forms, namely, the
teleuto-, æcidio-, and uredo-spores. The spores, in the host, are
formed immediately beneath its epidermis, which is ruptured on the
ripening of the spores, with the production of “rust,” brown, red, or
black spots. Those chlamydospores which produce basidia are termed
_teleutospores_. The spore on germination produces a _transversely
divided basidium_, “promycelium,” on which basidiospores, “sporidia,”
generally four in number, are produced on lateral sterigmata. This
basidio-fructification is _gymnocarpic_; the basidia neither form a
hymenium nor a fruit-body (only _Cronartium_ and _Gymnosporangium_ have
a slight indication of a basidio-fructification).

Many Rust-Fungi, in addition to basidiospores, have small, _unicellular
conidia_, “spermatia,” which are borne in conidiocarps, “_spermogonia_.”

The ~TELEUTOSPORES~ (_Winter-spores_) may be either unicellular or
multicellular; in the majority of cases they are enclosed in a hard
outer cell-wall, the exospore, which in some cases is very strongly
developed; they have also a long or short stalk, the remains of the
spore-bearing hypha. Each cell of the teleutospore has _one germ-pore_
(a thin portion of the wall, for the protrusion of the germ-tube;
in _Phragmidium_ and _Gymnosporangium_ there are, however, several
germ-pores). The colour of the teleutospores is generally much darker
than that of the uredospores, and it is by these that the majority of
the Rust-Fungi _hibernate_.

   In _Gymnosporangium_, two kinds of teleutospores are found
   (distinguished by their size and thickness of exospore). In many
   species of _Puccinia_, the form of the teleutospores varies
   very much, so that in the same layer spores have been observed
   with the characteristic form of other, allied genera.--The
   teleutospores of _Endophyllum_ resemble æcidiospores, since they
   are united in chains, whose cells are easily separated, and are
   produced in the interior of a “peridium.” The multicellular
   teleutospores of _Coleosporium_ function as basidia, and from
   each cell immediately produce basidiospores.--The teleutospores
   of _Coleosporium_ and _Chrysomyxa_, differ from other
   teleutospores in the absence of exospore and germ-pore.

The ÆCIDOSPORES (_Spring-spores_) are produced in chains which are
generally enclosed in an _envelope_ of hyphæ, the _peridium_; the
_peridium_ enclosing the spores being termed the _æcidium_. The
æcidiospores are unicellular, and generally of an orange colour; they
are often separated by intermediate cells which wither and so assist
in the distribution of the spores. The exospore is made up of minute,
radially arranged rods. _Generally germination_ proceeds _immediately_,
the æcidiospore producing a germ-tube, which developes into a mycelium
bearing either uredo- or teleutospores.

   The æcidia of many Rust-Fungi were formerly considered as
   distinct genera. The æcidia of _Phragmidium_, _Triphragmium_,
   and _Melampsora_, in which the _peridium is wanting_, were in
   part considered as _Cæoma_. The æcidia with fimbriate edge,
   or those of _Gymnosporangium_ with longitudinal lattice-like
   splits, were considered as “_Rœstelia_” (Lattice-Rust); large,
   sac-shaped æcidia on the Coniferæ were known as _Peridermium_.

The ~UREDOSPORES~ (_Summer-spores_) are unicellular and arise singly,
seldom in chains (_Coleosporium_). Their colourless, warty exospore
bears, _in the equatorial plane_, 2–8 _germ-pores_. In the majority,
_germination_ proceeds _immediately_, and a mycelium is produced which
at first gives rise to uredospores and afterwards to teleutospores.

   The uredospore-formations of _Melampsorella_ and _Cronartium_
   are enclosed in an _envelope_, and hence resemble
   æcidia.--Between the uredospores sterile, unicellular hyphæ
   (paraphyses) may be found.

The _spermogonia_ are spherical or pear-shaped _conidiocarps_,
generally embedded in the substratum, and are produced before the
æcidia, before or simultaneously with the uredospores, or before the
teleutospores. The conidia, as far as observations go, do not generally
germinate under ordinary conditions.

Among the Rust-Fungi some species are found which only form
basidiospores and teleutospores (_Puccinia malvacearum_, _Chrysomyxa
abietis_). Other species have in addition uredospores; others
spermogonia and uredospores; others spermogonia and æcidia; others
spermogonia, uredospores and æcidia. Those species in which all the
methods of reproduction are not developed must not be considered as
incomplete forms.

As a rule the mycelium, which is produced from the basidiospores,
developes æcidia; in the species, however, without æcidia, it
developes the uredo-form, and when the uredospores are also absent,
the teleutospore-form. It has been established in some species
of _Puccinia_ and _Uromyces_ that the formation of æcidia can be
suppressed, and it is not a necessary part of the cycle of development
of the species.

   The majority of Rust-Fungi hibernate in the teleutospore-form.
   Many species are able to hibernate in the uredospore-form
   (_Coleosporium senecionis_). Others pass the winter in the
   æcidio-form, and develope æcidia on new hosts (_Uromyces pisi_,
   on _Euphorbia cyparissias_; _Phragmidium subcorticium_, on
   _Rosa_; _Æcidium elatinum_, on _Abies alba_). In _Chrysomyxa
   abietis_, the mycelium, developed from the basidiospores,
   survives the winter.

Among the Rust-Fungi, with several forms of reproduction, there are
about sixty whose development can only be completed by an _alternation
of hosts_, that is, on one host only uredo-and teleutospores
are produced, while the further development of the germinating
basidiospores, and the formation of the æcidia and spermogonia from its
mycelium, can only take place on a second quite distinct and definite
host (_heterœcious_ or _metoxenous_ Fungi). Those Fungi which have all
their forms of reproduction on the same host are termed _autœcious_ or
_autoxenous_. It is not, however, always necessary that the heterœcious
Rust-Fungi should regularly change their hosts; for example, _Puccinia
graminis_ can hibernate in the uredo-form on the wild Grasses, and in
the spring can distribute itself again in the same form.

   As a consequence of the alternation of hosts the various forms
   of development were considered as independent genera (_Uredo_,
   _Æcidium_, _Rœstelia_, _Cæoma_, _Peridermium_), until De Bary
   and Oersted established, about the same time (1865), the mutual
   connection of some forms, and paved the way for the right
   conception of these Fungi.

  [Illustration: FIG. 146.--_Puccinia graminis_.]

As an example of one of the most highly developed species, _Puccinia
graminis_, the “Rust of Wheat,” holds a prominent position. Its
uredospores and teleutospores are produced (Fig. 146) on Grasses
(on cereals, especially Wheat, Rye, Oats, and many wild Grasses),
while the æcidia and spermogonia are confined to the Berberidaceæ.
The teleutospores, developed on the Grasses, hibernate on the dried
portions of their host, and in the succeeding year each of the
two cells of the teleutospore may develop a _basidium_ with four
basidiospores (Fig. 146 _D_, _c_). The basidiospores are distributed by
the wind, germinate quickly, and only proceed to further development on
_Berberis_ or _Mahonia_. The germ-tube _bores through the epidermis_ of
the Barberry-leaf, and forms a mycelium in its interior, its presence
being indicated by reddish-yellow spots on the leaf. After 6–10 days
the flask-shaped _spermogonia_ appear (Fig. 147 _B_; _C_, _a_; conidia
in Fig. 147 _D_) and a few days later the cup-shaped _æcidia_ (Fig.
147 _A_; _C_, _c_, _d_, _e_). The former are generally on the _upper_,
and the latter on the _under side_ of the leaf. The orange-coloured
æcidiospores scatter like dust, and germinate only on Grasses; the
germination takes place in about two days when placed on any green
part of a Grass. The germ-tube enters the Grass-leaf through a stoma;
a mycelium is developed in the leaf, giving rise to a small, oval,
rust-coloured spot (Fig. 146 _A_); in about 6–9 days the epidermis is
ruptured over the red spot, and numerous reddish-yellow _uredospores_,
formed on the mycelium, are set free. The uredospores (Fig. 146 _B_)
are scattered by the wind, and can germinate should they fall on the
green portions of other Grasses: they then emit 2–4 germ-tubes through
the equatorially-placed germ-pores. The germ-tubes enter a leaf through
a stoma, a new mycelium is then developed, and in about eight days
a fresh production of uredospores takes place, which germinate as
before. The uredospore-mycelium very soon produces, in addition, the
brown _teleutospores_, which give a brown colour to the rust-coloured
spots, the familiar uredospores on the cereals being quite suppressed
towards the close of the summer (Fig. 146 _C, D_). The “Rust of Wheat”
hibernates on some wild Grasses in the uredospore-form.

  [Illustration: FIG. 147.--_Æcidium berberidis_. _A_ Portion of
  lower surface of leaf of Barberry, with cluster-cups (æcidia).
  _B_ A small portion of leaf, with spermogonia, from above. _C_
  Transverse section of leaf on the upper side, in the palisade
  parenchyma are three spermogonia (_a b_); on the lower side an
  unripe æcidium (_c d_) and two ripe æcidia (_d, e, f_); _f_ chain
  of æcidiospores. _D_ Hyphæ, forming conidia.]

   GENERA. _Puccinia_ (Fig. 146, 147) has bicellular teleutospores,
   each having a germ-pore, and the æcidia when present have an
   indented peridium; some species, as exceptions, have 1–3-celled
   teleutospores. Many species are HETERŒCIOUS, for example, _P.
   graminis_, described above; _P. rubigo_, which also infests
   various Grasses, but whose æcidia appear on _Anchusa_; the
   masses of teleutospores are small; they contain paraphyses, and
   are for a long time covered by the epidermis. _P. coronata_, on
   Oats and Rye Grass; its æcidia on _Rhamnus_; the teleutospores
   are surmounted by a crown--“coronate processes.” _P.
   phragmitis_, on Reeds; æcidia on species of _Rumex_ and _Rheum_.
   _P. moliniæ_, on _Molinia cœrulea_; the æcidia on Orchids.
   _P. poarum_, on Meadow-Grass; æcidia on _Tussilago_. Various
   Puccinias growing on species of _Carex_ have their æcidia on
   _Urtica_, _Lysimachia_, _Cirsium_, _Pedicularis_, etc.--Of
   those AUTŒCIOUS species, which have all their generations on the
   same host, may be noted:--_P. galii_, _P. menthæ_, _P. violæ_,
   _P. epilobii_, _P. asparagi_, which grow on the hosts from
   which they have taken their specific names.--As representative
   of a group which have spermogonia, uredo-and teleutospores on
   the same host, but on different individuals, _P. suaveolens_,
   on the Field-Thistle, may be mentioned. The spermogonia have
   a strong odour.--A peculiar group (_Leptopuccinia_) has only
   teleutospores, which germinate immediately, and whilst still
   attached to their living host. To this group belong _P.
   arenariæ_, on a number of Caryophyllaceæ; and _P. malvacearum_,
   on various Malvaceæ, introduced in 1873 from South America to
   Europe, where it soon proved very destructive to Hollyhocks.

   _Uromyces_ (Fig. 149) differs only from _Puccinia_ in always
   having unicellular teleutospores. Among this genus both
   heterœcious and autœcious species are found. To the first
   group belong _U. pisi_, whose æcidia are found on _Euphorbia
   cyparissias_, and _U. dactylidis_, whose æcidia appear on
   _Ranunculus_; to the second group belong _U. betæ_, _U.
   phaseoli_, _U. trifolii_.

   _Triphragmium_ has teleutospores with three cells (one below and
   two above), on _Spiræa ulmaria_.

   _Phragmidium_ (Fig. 150) has teleutospores consisting of a
   row of cells (3–10) arranged in a straight line; the upper
   cell has one germ-pore and the others four germ-pores placed
   equatorially. Both this and the preceding genus have large,
   irregular æcidia without peridia, but often with bent, club-like
   paraphyses (150 _b_ and _c_); they are all autœcious, and are
   only found on the Rosaceæ.

  [Illustration: FIG. 148.--_Gymnosporangium sabinæ_. A small
  portion of the epidermis of a Pear-leaf (_a_) pierced at _b_ by
  the germinating basidiospore (_c_).]

  [Illustration: FIG. 149.--_Uromyces genisteæ_; _a_ uredospore;
  _b_ teleutospore.]

   _Endophyllum_ (see above, under teleutospores, p. 147) on
   species of _Sempervivum_.

   _Gymnosporangium_ (Figs. 152, 154) has bicellular teleutospores
   collected in large, gelatinous masses formed by the swelling of
   the long spore-stalks; in each cell 2–4 germ-pores are found.
   Uredospores are wanting. All the species are heterœcious; the
   teleutospores appear on _Juniperus_, the æcidia (_Rœstelia_)
   on the Pomaceæ. _G. sabinæ_, on _Juniperus sabina_, _J.
   virginiana_, etc., has the æcidia (“_Rœstelia cancellata_”)
   on _Pyrus communis_ (Figs. 152, 148); _G. juniperinum_, on
   _Juniperus communis_ with “_Rœstelia cornuta_” (Fig. 154 _a_)
   on _Sorbus aucuparia_, _Aria nivea_ (_S. aria_) and _Malus
   communis_; _G. clavariæforme_ on _Juniperus communis_, the
   æcidium belonging to it (“_Rœstelia lacerata_”) on _Cratægus
   oxyacantha_.

   _Melampsora_ has prismatic teleutospores placed parallel to each
   other and forming a crustaceous layer; in many species they
   are divided longitudinally into several cells (Fig. 151). The
   æcidia, without peridium, belonged to the old genus _Cæoma_.
   _M. caprearum_, on Willows, has the æcidia (_Cæoma euonymi_) on
   _Euonymus_. _M. hartigii_, on Osiers; the æcidium on _Ribes_.
   _M. mixta_, on _Salix repens_ and Orchids. _M. pinitorqua_,
   on leaves of the Aspen, æcidia on Pine branches (Pine shoot
   fungus); _M. populina_ on _Populus monilifera_ and _nigra_; _M.
   betulina_ (Fig. 153), on Birch leaves; _M. padi_ (Fig. 151),
   on leaves of _Prunus padus_, developes teleutospores in the
   epidermal cells; _M. lini_ is the cause of injury to the Flax;
   _M. agrimoniæ_.

  [Illustration: FIG. 150.--_Phragmidium gracile_: _a_ an
  uredospore; _b_ and _c_ two paraphyses; _d_ a young teleutospore;
  _e_ a teleutospore with a basidium and two basidiospores (_s_);
  _f_ two series of æcidiospores (_Ph. rosæ_).]

   _Calyptospora gœppertiana_; teleutospores on _Vaccinium vitis
   idæa_; spermogonia and æcidia on _Abies alba_ (Firneedle-Rust).

   _Coleosporium_ (Fig. 155) forms its uredospores in
   reddish-yellow chains; for the teleutospores, see page 147.
   _C. senecionis_, on the Groundsel; its æcidium (_Peridermium
   wolffii_) on Pine-leaves (Fig. 155 a). Other species on
   _Sonchus_, _Petasites_, _Campanula_, _Rhinanthaceæ_.

   _Chrysomyxa_ (Fig. 156) has bright red, branched
   teleutospore-chains; each spore developes a 4-celled basidium.
   _C. ledi_, on _Ledum palustre_; its æcidia on the leaves of the
   Fir. _C. abietis_ (Fig. 156), without uredo-and æcidiospores;
   teleutospores on the leaves of the Fir. In the first summer,
   yellow bands are formed on the leaves, and in the following
   spring the red cushions of spores.

  [Illustration: FIG. 151.--_Melampsora padi_: _a_ and _b_
  uredospores; _c-f_ teleutospores, seen from different sides.]

  [Illustration: FIG. 152.--Pear-leaf, seen from the under side,
  with “_Rœstelia cancellata_”: in different ages (_a_ youngest,
  _d_ oldest).]

  [Illustration: FIG. 153.--_Melampsora betulina_: _a_ uredospores;
  _b_ three contiguous teleutospores, one of which has developed a
  basidium with three basidiospores. (× 400.)]

  [Illustration: FIG. 154.--_Gymnosporanginum juniperinum_: _a_
  a small leaf with three clusters of æcidia (nat. size); _b_
  three conidia; _c_ two æcidiospores on one of which are seen the
  germ-pores; _d_ a portion of the wall of an æcidium; _e_, _f_ two
  teleutospores.]

  [Illustration: FIG. 155.--_Coleosporium senecionis_: _a_
  Pine-leaves with æcidia (_Peridermium wolffii_) nat. size; _b_
  an æcidiospore; _c_ a germinating æcidiospore; _d_ a chain of
  uredospores; _e_ a chain of teleutospores of which the terminal
  one has germinated and produced a basidiospore (_s_).]

   _Cronartium_ (Figs. 157, 159) has unicellular teleutospores
   united in numbers to form erect threads or columns; the
   uredospores are enclosed in a “peridium”; _C. ribicola_ (Fig.
   157), on leaves of Ribes (especially Black Currants); its
   æcidia (_Peridermium strobi_, or _P. klebahni_) on the stems
   and branches of _Pinus strobus_ (Fig. 159), on which it causes
   great damage; _C. asclepiadeum_, on _Vincetoxicum officinale_;
   its æcidia (_Peridermium cornui_) on the stems and branches of
   _Pinus silvestris_.

  [Illustration: FIG. 156.--_Chrysomyxa abietis_: _a_ leaf of the
  Fir, with 5 clusters of basidiospores (× 4); _b_ branched rows of
  teleutospores springing from the mycelium (_m_).]

  [Illustration: FIG. 157.--_Cronartium ribicola_: _a_ mass
  of uredospores (× 50); _b_ an uredospore; _c_ a column of
  teleutospores (× 60); _d_ a small portion of the same more highly
  magnified, with a basidium and two basidiospores (_s_).]

   To the Fungi of which the æcidium is known, whilst the remaining
   forms are still undetermined, but which are without doubt
   heterœcious, belong _Æcidium elatinum_, which produces the
   enormous “witches’ brooms” and barrel-shaped swellings on stems
   and branches of _Abies alba_; and _Æcidium strobilinum_ (Fig.
   158), which attacks Fir-cones, causing all the scales to become
   covered with clusters of æcidia opening by a lid. _Hemileia
   vastatrix_ destroyed the coffee plantations in Asia.

  [Illustration: FIG. 158.--_Æcidium strobilinum_: _a_ scale of
  cone of _Picea excelsa_, with numerous æcidia; _b_ æcidiospores
  arranged in a series; _c_ a cell of the peridium.]

Order 2. =Auriculariaceæ.= The _long, transversely divided_ basidia
bear laterally 4 _long sterigmata_ with basidiospores (Fig. 160 _B_)
and are united to form an _hymenium_ on the surface of the fruit-body.
Parasites or saprophytes.

   _Auricularia sambucina_ (_Auricula judæ_), Judas’-ear, has large
   fruit-bodies, which may attain the size of several inches,
   resembling an ear or a mussel shell. In the moist condition they
   are flesh-coloured, tough and gelatinous, but when dried, become
   hard, grey and wrinkled; the exterior is covered with short
   hairs; while the internal surface bears the hymenium. Habitat:
   stems and branches of old Elder-trees (_Sambucus_).

Order 3. =Tremellaceæ.= The _round, pear-shaped, longitudinally divided
basidia_ bear 4 _elongated sterigmata_, situated apically, and 4
basidiospores (Fig. 160 _C_, _D_), and are united into the _hymenium_
on the surface of the fruit-body. The fruit-bodies are frequently
gelatinous and quivering; similar fruit-bodies are also found in the
Dacryomycetaceæ and Hydnaceæ. Simple conidiophores, which appear not
infrequently in the basidiocarps, before the basidia, are known in many
species. Saprophytes.

  [Illustration: FIG. 159.--_Peridermium strobi_: æcidia of
  _Cronartium ribicola_ (nat. size).]

  [Illustration: FIG. 160.--_B Auricularia sambucina_: _a-d_
  basidia in various stages of development; _e_ a sterigma
  bearing a spore.--_C Tremella lutescens_: _a-d_ basidia seen
  from various sides (_b_ from above) and in various stages of
  development; _e_ sterigma with basidiospore (× 400). _D Exidia
  glandulosa_: _a-c_ various stages in the development of a
  basidium; _d_ sterigma with basidiospore (× 350).]

   _Exidia_ has kidney-shaped, oblong basidiospores, and small,
   hook-like conidia; _E. glandulosa_, _E. albida_, etc., on
   wood.--_Craterocolla_ has conidiocarps; _C. cerasi_ on
   Cherry-wood.--_Sebacina incrustans_; the yellow, fleshy, or
   cartilaginous fruit-bodies are found in autumn covering the
   ground in moist woods.--_Tremella_ has round basidiospores;
   _T. mesenterica_ has irregularly-folded, quivering, orange
   fruit-bodies, about one inch in breadth; _T. lutescens_ (Fig.
   161) has orange-yellow conidial-and yellow basidial-layers; _T.
   frondosa_ has fruit-bodies upwards of a foot in breadth.

Order 4. =Pilacraceæ.= The _transversely divided basidia_ have _no
sterigmata_, but sessile basidiospores, and fill up the cavity of a
_closed_ (_angiocarpic_) _fruit-body_ as a gleba without a regular
arrangement (hymenium wanting).

   _Pilacre fagi_ on the old stems of the Copper-Beech; _P.
   petersii_, on dried branches of the Hornbeam, has stalked,
   capitate fruit-bodies.

  [Illustration: FIG. 161.--_Tremella lutescens_: I and II
  fruit-bodies (nat. size); III vertical section through a
  fruit-body; _b_ basidia; _c_ conidia; IV-VI basidia; VII
  basidiospore with a second spore; VIII a basidiospore with
  yeast-like budding (cultivated); IX a conidiophore. (III-IX about
  400.)]


                    Series 2. =Autobasidiomycetes.=

This second and larger part of the Basidiomycetes is characterised
by its more highly differentiated, _undivided_, club-shaped, or
cylindrical basidia, which generally bear 4 (seldom 2, 6, 8)
apically-placed sterigmata and basidiospores (Fig. 145). The
fruit-bodies are partly _gymnocarpic_ (in the first 3 orders and in
some Agaricaceæ), partly _hemiangiocarpic_ (in orders 3–6 of the
Hymenomycetes and in the Phalloideæ, the fruit-bodies in these orders
are in the young conditions more or less angiocarpic, but later on
generally open below and bear the hymenium on the under surface of the
fruit-body), partly also _angiocarpic_ (in the Gasteromycetes).

  [Illustration: FIG. 162.--_Dacryomyces deliquescens_: I
  fruit-body (nat. size); II vertical section through the hymenium;
  III germinating basidiospore; IV a portion of mycelium with
  conidia; V a germinating conidium; VI and VII chains of oidia
  more or less strongly magnified; VIII basidiospore of _D.
  longisporus_; IX germinating basidiospore of _D. ovisporus_;
  X and XI _Calocera viscosa_; X fruit-body (nat. size); XI
  basidia with basidiospores (highly magnified); XII _Dacryomitra
  glossoides_ (nat. size).]


                      Family 1. =Dacryomycetes.=

The _long, club-shaped basidia_ bear _two tapering sterigmata_, which
develope remarkably large basidiospores (Fig. 162 II, XI) and form
_gymnocarpic_ fruit-bodies with hymenium. 1 order:

Order 1. =Dacryomycetaceæ.= This order comprises 4 genera of which the
first two develope the hymenium on the whole surface of the fruit-body,
but the two last only on its apex.

   _Dacryomyces_: the folded, gelatinous, _Tremella_-like
   fruit-bodies break out in winter on dried wood (hedges) in
   the form of red or yellow drops. _D. deliquescens_ is very
   common (Fig. 121). The following genera have cartilaginous
   fruit-bodies.--_Calocera_ (Fig. 162), with club-like, simple,
   or branched, _Clavaria_-like, fruit-bodies; the orange coloured
   fruit-bodies of _C. viscosa_ grow aggregated together on the
   wood of Conifers.--_Guepinia_ resembles a _Peziza_, and has
   the hymenium only on the hollow upper surface.--_Dacryomitra_
   resembles a _Mitrula_ (Fig. 162).


                      Family 2. =Hymenomycetes.=

This family is very rich in species (more than 8000 have been
described), and to it belong all the “Mushrooms” and “Toadstools.”
The _fruit-bodies_ present very various forms; they are generally
fleshy, very perishable, seldom leathery or corky, in the last case
often perennial. The _basidia_ are more or less _cylindrical_ and bear
_generally_ 4 (seldom 2, 6 or 8) _sterigmata and basidiospores_. The
hymenium in the fully-formed fruit-bodies lies free on the surface: in
orders 1 and 2 and a portion of order 6 it is from the commencement
exposed, fruit-bodies _gymnocarpic_; orders 3–6 have _hemiangiocarpic_
fruit-bodies (p. 157). In the first order the basidia (or the
hymenium) are developed immediately from the mycelium (Fig. 163); the
fruit-bodies of orders 2 and 3 present a higher grade of development,
and have between the mycelium and hymenium a special hyphal-tissue,
a _stroma_, which is crustaceous, club-like, or coralloid, etc.,
and in general bears the hymenium on the largest part of the free,
smooth surface. In the forms most highly developed (orders 4–6) a
new tissue--the _hymenophore_--is introduced between the stroma and
hymenium, which appears on the under side of the fruit-body in the
form of warts, projections, tubes, folds or lamellæ (Figs. 166, 167,
174 _bc_). _Paraphyses_ are frequently found in the hymenium, among
the basidia. In the Hymenomycetes few examples of _conidia_ can be
recognised at first. More frequently _chlamydospores_ are found,
particularly _oidia_. The _mycelium_ is richly branched, generally
colourless, often perennial; it lives in humus or decaying wood, and is
seldom parasitic. The hyphæ generally have clamp-connections and unite,
sometimes, to form a rhizomorpha (Fig. 177) or sclerotia with coloured,
pseudo-parenchymatous covering.

   [Illustration: FIG. 163.--_Exobasidium vaccinii._ I
  Hypertrophied stem of _Vaccinium vitis idæa_; II leaf with
  gall-like swelling; III section of II; IV transverse section: _m_
  mycelium between the parenchymatous cells; _p_ hypodermal cells;
  _e_ epidermis with basidia in various stages of development; V
  epidermis with germinating spores; VI and VII spores germinating
  in water (IV-VII × 620).]

Order 1. =Tomentellaceæ.= To this order belong the simplest of the
Hymenomycetes. The basidia (Fig. 145) arise free and irregularly
from the mycelium; a _hymenium_ is _entirely absent_ or _very
slightly formed_ (in _Corticium_ it attains its highest development);
_fruit-bodies_ are _also wanting_.--In general they form flaky,
membranous or leathery coverings on bark and wood. Some are parasites.

   _Hypochnus_ without conidia.--_Tomentella_ with conidiophores;
   growing on wood or earth.--_Exobasidium vaccinii_ (Fig. 163),
   a parasite on _Vaccinium_, _Andromeda_, _Arctostaphylos_, and
   _Rhododendron_, forms flaky-powdery, white or red coverings and
   may cause hypertrophy of the parts attacked. _E. warmingii_ is
   parasitic on _Saxifraga_; _E. lauri_ causes outgrowths on the
   stem of _Laurus canariensis_ as long as a finger, which formerly
   were regarded as aerial roots.--_Corticium_ forms membranous
   to leathery layers or crusts; _C. quercinum_ on wood and bark,
   particularly Oak, is flesh-coloured; _C. cæruleum_ has a blue
   hymenium; _C. giganteum_ on the bark of fallen Pine-trees.

Order 2. =Clavariaceæ.= The hymenium is situated on a stroma, and
either completely _covers the smooth surface_ of the more or less
fleshy _gymnocarpic fruit-body_, or is confined to a tolerably well
defined _upper portion_ of it (_Typhula_). Paraphyses absent. The
vertical, white, yellow, or red fruit-bodies are roundish or club-like,
undivided or richly branched (Fig. 125). Generally on the ground in
woods, seldom on tree-stems, etc.

  [Illustration: FIG. 164.--_Clavaria coralloides_ (nat. size).]

   GENERA: _Clavaria_, generally large Fungi with thick, round
   branches. _C. botrytis_ has a very thick, tubercular stem with
   numerous short, flesh-coloured branches: it has an agreeable
   taste. _C. coralloides_ has a brittle, richly-branched
   fruit-body (Fig. 164); basidia with two large spores. _C.
   pistillaris_ consists of a single, undivided club of a
   yellowish-white colour.--_Sparassis_ has compressed, leaf-like,
   curled branches; _S. crispa_ has fruit-bodies as large as
   a white cabbage-head, with an agreeable taste.--_Typhula_
   and _Pistillaria_ are small Fungi with filamentous stalks,
   terminating in a small club. The fruit-bodies of the former
   often arise from a small, spheroid sclerotium; the latter is
   distinguished by the basidia bearing only two spores.

Order 3. =Thelephoraceæ.= The hymenium is placed on a stroma and
_covers the smooth surface_ of the leathery _hemiangiocarpic
fruit-body_, generally _on its under side_. The edge of the stroma,
which bounds the hymenium, is sometimes especially developed
(_Stereum_). Saprophytes.

   GENERA: _Thelephora_. The fruit-bodies in this genus are brown,
   very irregularly shaped, and often lobed. The spores too are
   brown, but in the other genera colourless. The species are found
   growing on barren soil. _T. laciniata_ (Fig. 165) has imbricate,
   semicircular, dark-brown pileus, which is jagged at the edge
   and upper surface. The fruit-bodies are very often raised above
   the ground, and although this species is not a parasite, yet
   it destroys young seedlings by growing above and smothering
   them.--_Stereum_ has a stiffer fruit-body, with a distinct,
   fibrous, intermediate layer. It grows on bark and wood,
   projecting like a series of imbricate brackets. _S. hirsutum_
   is yellow; its free edge is provided with a number of stiff
   hairs, the upper surface being divided into a number of zones.
   _S. purpureum_ has a red-violet hymenium which distinguishes
   it from the previous species.--_Cyphella_ has a membranous
   cup- or bell-shaped fruit-body, often borne on a stalk, the
   concave surface being covered with the hymenium. They are small,
   white Fungi, growing on Moss and dead stems.--_Solenia_ is
   closely related to _Cyphella_; its fruit-bodies are smaller and
   hairy; they are found clustered together forming a crust-like
   covering on dead wood.--_Craterellus_ has a large, funnel-shaped
   fruit-body, the hymenium covering the external surface.
   _C. cornucopioides_ is shaped like a trumpet or a “horn of
   plenty.” It is dark-grey, several inches in height, and grows
   gregariously on the ground in forests. It is distinguished by
   the basidia bearing only two sterigmata.

  [Illustration: FIG. 165.--_Thelephora laciniata_ (nat. size).]

Order 4. =Hydnaceæ.= The fruit-body is most frequently fleshy, and
varies considerably in shape, the simplest forms being resupinate,[14]
the higher ones umbrella-like. The _hymenophore_ is found on the
free or downward-turned surface, and always takes the _form of soft
emergences_ hanging vertically downwards. The emergencies may be
thorn-, awl-, or wart-like. The species are found growing on the soil
and on dead wood.

   GENERA: _Hydnum_ has subulate, distinct emergences. _H.
   repandum_ is yellow, the stalk being placed in the centre of the
   pileus. It is an edible species, and often forms “fairy rings”
   in woods. _H. auriscalpium_ (Fig. 166) is dark-brown, with stalk
   placed at the edge of the pileus. It grows on old Fir-cones. _H.
   erinaceus_ grows on old tree-trunks. The fruit-body is yellow
   and very large--as big as a human head--with emergences as much
   as an inch in length.--_Irpex_ has a leathery fruit-body, partly
   resupinate, partly with free, projecting edge; the under side
   bears tooth-like emergences which are arranged in rows, and
   _Irpex_ thus forms a transition to the Agaricaceæ.--_Phlebia_
   is entirely resupinate, with radially-arranged folds on the free
   side, and pectinate border.

  [Illustration: FIG. 166.--_Hydnum auriscalpium_, upon a Fir-cone,
  in different stages of development.]

Order 5. =Polyporaceæ (Pore-Fungi).= An order very rich in species
(about 2000 species are described). The fruit-body is of very
different forms--resupinate, projecting like a bracket, hoof-like, or
umbrella-shaped. In some it is fleshy and edible, in others leathery or
corky, persisting for several years. The hymenophore is situated on the
under side of the fruit-body, and consists of wide or narrow _tubes_ or
_pores_, whose inner surface is clothed with the hymenium (Fig. 167).
In some fruit-bodies large cavities are to be found, which have arisen
as interstices between the labyrinthine curved and reticulate folds.
Chlamydospores are known in some species. Conidia occur very rarely.
Many species work considerable damage: some as parasites on trees,
others by destroying timber.

  [Illustration: FIG. 167.--_Polyporus igniarius._ Section through
  the under side of the Fungus: _h-h_ is hyphal-tissue between the
  tubes, formed by irregularly felted hyphæ, many of which are seen
  cut across; _s_ is the hymenium which covers the walls of the
  tubes, and from which the basidia with the spores protrude.]

   GENERA. _Polyporus_ (Pore-Fungus). The tubes are narrow,
   accurately fitted together, and forming a thick layer on the
   under side of the fruit-body, appearing as a number of fine
   holes. The fruit-body most frequently resembles a bracket, or
   is hoof-shaped, with one side growing from a tree-trunk; it
   is very often perennial, and a new layer of tubes arises in
   each succeeding period of vegetation. Strata, corresponding
   to the periodically interrupted growth, are thus formed in
   storeys one above the other, and are visible on the upper
   surface of the fruit-body, as well as in the interior, as a
   series of concentric belts, sometimes as many as half a score
   or more in number. _P. fomentarius_ (Touchwood) attacks
   trees, especially the Beech. The spores germinate on wounds
   from broken branches, and the hyphæ, following the course of
   the medullary rays, find their way into the interior of the
   tree, from whence the mycelium spreads upwards, downwards, and
   peripherally, so that the wood becomes rotten (“white-rot”) and
   thick felts of mycelium are formed in radial and tangential
   directions. A dark line, caused by the youngest parts of the
   hyphæ containing a brown juice, marks the boundary between
   the rotten and the unattacked parts of the stem (Fig. 168);
   at places where the mycelium extends to the bark, the cambium
   becomes destroyed and further growth is arrested, so that
   longitudinal furrows arise on the stem. It is at these places,
   too, that the hoof-shaped, ash-coloured fruit-bodies are
   developed, which may attain a circumference of upwards of 7
   feet. The interior of the fruit-body consists of a dried-up,
   loosely felted, red-brown mass of hyphæ, which has been used for
   tinder and as a styptic (“Fungus chirurgorum”). _P. igniarius_
   has a harder, dark-brown, more rounded fruit-body; it grows in
   a similar manner, but especially attacks Oaks, Poplars, and
   Plum-trees, the wood of which becomes rotten, and is called
   touchwood. _P. pini_ (_Trametes pini_), (Fig. 170), a parasite
   on the stems of _Pinus_, causes a kind of “red-rot” in the
   stem. _P. sulphureus_ has a soft, cheesy, yellow fruit-body;
   it produces “rot” in Oaks and Apple-trees. _P. officinalis_,
   Larch-fungus (“Fungus Laricis” in Pharmocopœia), grows on
   Larch-trees in the south-east of Europe. _P. versicolor_ has
   thin, semicircular fruit-bodies, with zones of various colours
   on the upper side; it is one of the most frequent species on
   tree-stems. _P. frondosus_ grows on soil in woods, and consists
   of numerous aggregated fruit-bodies, which become very large
   and fleshy. This species is edible. _P. perennis_ also grows on
   the soil in woods; it is very leathery, with central stalk, and
   has concentric zones on the upper surface of the fruit-body.
   _P. vaporarius_ destroys the wood of living Pines (_Pinus
   silvestris_) and Firs (_Picea excelsa_), causing it to become
   red-brown; in timber this Fungus causes “red-strip” followed by
   a “dry-rot.” _P. squamosus_ destroys many Walnut-trees, and is
   also very destructive to Limes and Elms. _P. fulvus_ causes a
   “white-rot” in _Abies alba_.

  [Illustration: FIG. 168.--Section of stem of a Beech attacked by
  _P. fomentarius_: _a_ non-attacked parts of the stem; _b_ the
  furrows where the mycelium has reached the bark, and where the
  thick mycelium-strands reach the exterior (⅙th of the nat. size).]

  [Illustration: FIG. 169.--Base of a Fir-tree, with a number of
  fruit-bodies of _Heterobasidion annosum_ just beneath the surface
  of the soil, indicated by the dotted line (¼th nat. size).]

  [Illustration: FIG. 170.--A fully developed fruit-body of
  _Polyporus pini_ (_Trametes pini_), lateral view (nat. size).]

   _Heterobasidion annosum_ (_Polyporus annosus_, _Trametes
   radiciperda_, Fig. 169) is characterized by its
   _Aspergillus_-like conidiophores. It is a parasite on the
   Pine, Fir, Birch, Beech, etc., and is the chief cause of a
   root-disease (red-rot) in Pines and Firs; the fruit-bodies
   develope a large number of basidiospores; they may be very large
   and are found just beneath the surface of the soil (on living or
   dead roots), and exposed to the air (on felled stems and roots,
   in Scandinavia).

   _Ptychogaster_ has cushion-like fruit-bodies, which consist
   chiefly of chlamydospore-chains, formed of ellipsoidal spores,
   which alternate with short hyphæ having transverse septa and
   clamp-connections. The hymenial portion is limited to a small
   group of tubes. _Pt. albus_ (_Oligorus ustilaginoides_) grows
   on stumps of Conifers and forms irregular cushions, at first
   white and later on brown, which consist almost entirely of
   chlamydospores.

   _Boletus_ (Fig. 171) has a fleshy fruit-body resembling a common
   Mushroom, with central stalk. The layer of tubes is easily
   detached from the pileus, and the tubes are easily separable
   from one another. They grow on the ground in woods. Edible
   species are: _B. edulis_, with thick, reticulate stalk; _B.
   scaber_, with thin stalk and rough pileus; _B. luteus_, with a
   ring on the stalk. _B. luridus_ is poisonous, its tubes have
   red openings, and the flesh turns quickly blue when broken and
   exposed to the air.

   _Fistulina hepatica_ (Beef-steak Fungus), has a red, fleshy,
   edible fruit-body, with red juice. The tubes are individually
   distinct; conidia are also developed. Grows on old Oaks.

   _Merulius lacrymans_ (“Dry-rot”) has a resupinate fruit-body
   with white, cotton-like border, and the remaining portions
   covered by reticulate, ramified veins of a rust-brown colour.
   In favourable vegetative conditions it is fleshy and exudes
   large drops of water--hence its specific name and also the name
   “Tear Fungus.” The mycelium is at first colourless, and then
   yellow-brown; when dry it is tough and leathery. It destroys
   the timber in damp houses, extends far and wide over boards and
   beams and even over the masonry, giving rise to a disagreeable
   smell in the rooms in which it lodges. In woods the Fungus lives
   on Pine-stems. It is brought from the forest on the logs of
   timber, and is distributed from log to log by the mycelium and
   the basidiospores. The living mycelium can be recognised by the
   clamp-connections shooting out branches. The basidiospores are
   often ejected a distance of a metre; they are elliptical (10–11µ
   long and 5–6µ broad), and germinate easily on damp wood, or in
   fruit-juice which has been neutralized with urine or alkaline
   carbonates.

   _Dædalea_ (Labyrinth Fungus), has bracket-like, corky
   fruit-bodies with irregularly-folded plates or discs on the
   under side. It forms a transition to the Agaricaceæ. _D.
   quercina_ is frequent on Oak-stumps.

  [Illustration: FIG. 171.--_Boletus edulis_ (about ¼th): _b_
  longitudinal section of a portion of the pileus.]

Order 6. =Agaricaceæ= (=Mushrooms=, =Toadstools=). _The hymenophore
consists_ of knife-like plates (_lamellæ_, _gills_), which are situated
on the under side of the umbrella-like pileus of the fruit-body, and
radiate from the central stalk. Those which are first formed extend
from the edge of the pileus to the stalk; those formed later reach only
a longer or shorter portion of this distance, according to their age.
In structure the lamellæ (Fig. 174) consist of a central mass of hyphæ,
the _trama_, continuous with the hyphæ of the pileus; these terminate
in a layer of shorter cells, the _subhymenial layer_, immediately
beneath the hymenium which is composed of basidia and paraphyses. In a
few species, but not in the majority, the lamellæ are branched, and in
some they are decurrent. A few have the stalk placed excentrically, or
it may be entirely absent.

  [Illustration: FIG. 172.--Development of _Psalliota campestris_:
  _a_, _b_, _c_, _d_ show the various stages of the development
  of the fruit-bodies and the mycelium (_m_) (nat. size); _e_ the
  fruit-body in a somewhat later stage, slightly magnified; _f_
  longitudinal section of _e_; _n_ first formation of the hymenium;
  _g_ longitudinal section of a more advanced fruit-body (nat.
  size); _n_ the hymenium; _o_ velum partiale (see Fig. 133.)]

In the early stages of its development the fruit-body is more or
less enclosed in a hyphal tissue--the “veil” (_velum universale_, or
_volva_). The veil at first completely encloses the young fruit-body,
but is afterwards ruptured as the latter grows, part remaining at the
base of the stalk as the “sheath” (_annulus inferus_), and part on the
pileus as scales or warts. In the “Fly Mushroom” (_Amanita muscaria_)
the remains of the veil are especially conspicuous as white patches
on the bright red ground of the upper surface of the pileus, and as
a sheath at the base of the stalk (Fig. 178 _v._). Another veil--the
_velum partiale_--a hyphal tissue (Figs. 178 _a_; 173) stretches from
the edge of the pileus to the stalk, and encloses the lamellæ. This
veil is ruptured as the pileus expands, a portion attached to the stalk
remaining as the “upper ring” (_annulus superus_) (Figs. 173, 178 _a_),
or a part attached to the pileus hanging down as a fringe round its
edge.--Some genera have no veil, the under side of the pileus being
exposed from the first (_gymnocarpic_ Agaricaceæ). Those which have
a veil (_hemiangiocarpic_ A.) afford a transition to the angiocarpic
Gasteromycetes.

  [Illustration: FIG. 173.--The cultivated Mushroom (_Psalliota
  campestris_).]

The mycelium mostly grows in soils rich in humus or dung, on decaying
trees and similar objects. Many species, _e.g. Tricholoma personatum_
and _Marasmius oreades_, form the so-called “fairy rings.” The
fruit-bodies in these species are confined to a larger or smaller
surface on which they are very regularly arranged in a ring. The reason
for this is found in the radial growth of the mycelium, so that the
oldest portion, or the starting point, is found at the centre of the
ring, and the younger ones, on which the fruit-bodies are formed, at
the circumference. The older hyphæ gradually die, and at the same time,
the radial growth continuing, the ring of fruit-bodies becomes larger
and larger. The “fairy-rings” are marked not only by the fruit-bodies,
but also by the more vigorous growth and darker colour of the grass
upon these spots.

Some species are _parasites_. An example is presented by _Armillaria
mellea_, a remarkable and very destructive Fungus in woods and forests
(Figs. 176, 177). ~In addition to the filamentous, white mycelium,
it has also black, or black-brown, horny, root-like mycelium-strands
(rhizomorpha) which were formerly considered to belong to a special
genus of Fungi described under the name “_Rhizomorpha_.” The mycelium
lives parasitically on the Conifers and other trees, forcing its hyphæ
into the bark and between the bark and wood, and thence penetrating
into the wood so that the tree is very severely attacked. It may also
live saprophytically, and clusters of fruit-bodies are often found on
old stumps and stems, on old timber, and in the rich soil of woods. The
rhizomorpha, living underground, can extend for considerable distances
and infect the roots of neighbouring trees, and spreads in this way
the diseases known as “Harzsticken” and “Bark-Canker,” which are very
destructive to young trees.~

  [Illustration: FIG. 174.--_Psalliota campestris. A_ Tangential
  section of pileus showing lamellæ (_l_). _B_ Portion of gill
  more highly magnified; _t_ trama; _hy_ hymenium with basidia and
  basidiospores; _sh_, subhymenial layer. _C_ A portion of the same
  more highly magnified; _s′ s′′ s′′′ s′′′′_ various stages
  in the development of basidiospores; _q_ paraphyses.]

The chief characteristics by which the numerous genera are separated
are the presence or the absence of the two kinds of veils, the nature
of the fruit-body, the form, branching of the lamellæ, and their
position and relation with respect to the stem, the shape of the
pileus, the colour of the spores, etc., etc. A knowledge of the colour
may be obtained by placing the pileus with the lamellæ turned downwards
on a piece of white or coloured paper, so that the spores, as they fall
off, are collected on the paper, and the arrangement of the lamellæ can
then be clearly seen.

  [Illustration: FIG. 175.--_Cantharellus cibarius_ (reduced).]

  [Illustration: FIG. 176.--_Armillaria mellea._ (½ nat. size): _a_
  root of a Fir; _b_ rhizomorpha-strands; _c-f_ fruit-bodies in
  four different stages of development.]

   [Illustration: FIG. 177.--The mycelium of _Armillaria mellea_
  (“_Rhizomorpha_”) (nat. size).]

About 4,600 species belonging to this order have been described.

   On account of the large number of species the order is divided
   into several sections:

   1. =Agaricinei=; fruit-body fleshy; lamellæ membranous,
   knife-like, with sharp edge; basidia crowded together. The
   FOLLOWING HAVE WHITE SPORES:--_Amanita_ (Fly Mushroom), with
   volva, and generally also the upper ring on the stalk; many are
   poisonous, such as _A. muscaria_ (Fig. 178) which has bright red
   pileus with white spots, _A. pantherina_ and _A. phalloides_;
   _A. cæsarea_ is edible.--_Lepiota procera_ (Parasol Fungus)
   is one of the largest Mushrooms; it has a scaly pileus and
   moveable ring (edible).--_Armillaria mellea_ has been mentioned
   above (Figs. 176, 177).--_Tricholoma_, lamellæ indented near
   the stalk; _T. gambosum_ (Pomona Fungus) belongs to the best
   of edible Fungi; _T. personatum_ often forms fairy rings (see
   above).--_Clitocybe_, lamella decurrent; _C. nebularis_ is
   edible.--_Pleurotus_, stalk eccentric; _P. ostreatus_ (Oyster
   Mushroom) grows in clusters on tree-stems (edible).--_Collybia_
   and _Mycena_, species numerous, small.--SPORES ROSE-RED:
   _Volvaria_ and _Hyporhodius_.--SPORES BROWN: _Cortinarius_,
   with cobweb-like veil; _Pholiota_, membranous veil and ring;
   _P. squarrosa_ in clusters on tree-stems; _P. mutabilis_, on
   tree-stumps (edible).--SPORES VIOLET-PURPLE: _Hypholoma_,
   _Psalliota_; to this section the common edible Mushroom (Fig.
   172–174) belongs, with annulus and chocolate-coloured lamellæ;
   it is cultivated for the sake of the fine flavour.--SPORES
   BLACK: _Coprinarius_.

  [Illustration: FIG. 178.--Fly Mushroom (_Amanita muscaria_).]

   2. =Marasmiei.= Fruit-body tough, almost leathery, and
   persistent; spores white. _Marasmius oreades_ forms large,
   regular fairy-rings on pastures and commons; it is used as
   seasoning in food.--_Panus stipticus_ with eccentrically-placed
   stalk, in clusters on tree-stumps.--_Schizophyllum_ has the edge
   of the lamellæ divided longitudinally, and the split portions
   revolute.--_Lentinus_ affords a transition to _Dædalea_ among
   the Polyporaceæ.

   3. =Russulei.= Fruit-body fleshy and fragile, in which two
   different systems of hyphæ may be distinguished; spores thorny,
   white, or pale-yellow. Many are poisonous.--_Russula_ has
   generally fragile and thick lamellæ reaching from stalk to edge
   of pileus; pileus frequently red.--_Lactarius_ has white or
   yellow milky juice, which often is very acid. _L. deliciosus_
   has red-yellow milky juice, and is of a pleasant flavour. _L.
   torminosus_ is poisonous.

   4. =Hygrophorei.= Lamellæ thick and waxy, widely separated;
   spores white. Many species of _Hygrophorus_ have
   brightly-coloured pileus and grow among the grass on moors and
   commons.--_Nyctalis_ is parasitic on larger Toadstools. It is
   remarkable for its abundant formation of chlamydospores, whilst
   the basidiospores are little developed.

   5. =Coprinei.= Fruit-bodies very soft, quickly perishable;
   lamellæ membranous and deliquescent. The basidia are separated
   from each other by paraphyses. _Coprinus_ has coal-black spores,
   grows on manure, and sometimes developes sclerotia.

   6. =Paxillei.= Fruit-body fleshy; lamellæ easily detached from
   the pileus and reticulately-joined near the stalk. They form a
   connecting link between the Agaricaceæ and _Boletus_.

   7. =Cantharellei.= Lamellæ reduced to dichotomously-divided
   folds, decurrent on the stalk. _Cantharellus cibarius_ (Fig.
   175) is yolk-yellow, and grows on the ground in woods (edible).
   It is allied to _Craterellus_.


                        Family 3. =Phalloideæ.=

The fruit-bodies before they are ripe are spherical or ovoid, and
enclosed by a _fleshy covering_, the peridium, which is _perforated
at maturity_ and remains as a sheath (Fig. 179); the fruit-bodies are
_hemiangiocarpic_.

Order 1. =Phallaceæ= (=Stink-horns=). The peridium has a complicated
structure and is composed of three layers, the intermediate one being
thick and gelatinous. The gleba (the tissue which bears the hymenium)
is situated upon a peculiar receptacle which expands into a porous
stalk and by its sudden distension, rupturing the peridium, elevates
the gleba and hymenium above the peridium, which remains as a sheath.
_The gleba becomes gelatinous and dissolves away as drops._ To this
order belong many peculiar and often brightly coloured forms, which are
natives of the Southern Hemisphere.

   _Phallus impudicus_ (Stink-horn) (Fig. 179), has a fruit-body
   which at first is white, heavy, and soft, and resembles a hen’s
   egg in shape and size. The peridium is divided into three layers
   (Fig. 179 _e_, _g_, _f_) of which the external and internal
   are membranous, and the middle one very thick and gelatinous;
   each of these has again a laminated structure. The peridium
   when ruptured remains as a sheath (_k_) at the base of the
   stalk. The receptacle at first is strongly compressed (_h_)
   but afterwards expands into a long stalk (_l_) which bears the
   conical gleba (_m_). Prior to the rupture of the peridium the
   gleba consists of a greenish mass (_i_) which, when exposed,
   emits a carrion-like stench serving to attract flies, by whose
   agency the spores are distributed. It is found commonly in
   hedgerows and in woods, growing on the ground. The much smaller
   and less common _P. caninus_ is found on rotten tree-stumps.--In
   _Clathrus cancellatus_ the receptacle expands into a bright red,
   reticulate structure. A native of the South of Europe. _Colus_,
   _Aseroë_, _Mitromyces_.

   Order 2. =Sphærobolaceæ.= An intermediate layer of the
   _peridium_ swells when ripe, becomes convex, and _ejects the
   remaining_ spherical _portion of the fruit-body_ which contains
   the spores. _Sphærobolus carpobolus_ has small, spherical
   fruit-bodies which open in the form of a star.

  [Illustration: FIG. 179.--_Phallus impudicus_ (Stink-horn),
  somewhat diminished. Fruit-bodies in all stages of development
  (_b_, _c_, _d_ and _k-m_) are seen arising from a root-like
  mycelium (_a_); _d_ longitudinal sections through a fruit-body
  before the covering has ruptured.]


                      Family 4. =Gasteromycetes.=

The fruit-body is _angiocarpic_, fleshy at first, and later generally
more or less _hard_ and _continues closed after the_ spores _are
ripe_. The tissue lying immediately inside the _peridium_ is termed
the _gleba_; it is porous, containing a larger or smaller number of
chambers lined with the hymenium, which is either a continuous layer of
basidia or else it fills up the entire cavity. The basidia as a rule
bear four spores, sometimes eight (_Geaster_), or two (_Hymenogaster_).
The tissue of the walls (_trama_) consists often (_Lycoperdaceæ_)
of two kinds of hyphæ, some thin and rich in protoplasm, divided
by transverse septa and bearing the basidia; others thicker and
thick-walled which do not dissolve like the former on the ripening of
the spores, but continue to grow and form a woolly, elastic mass, the
_capillitium_, which may be regarded as highly developed paraphyses.
The peridium may be either single or double, and presents many
variations in its structure and dehiscence. The mycelium is generally a
number of string-like strands, living in soils rich in humus.

   Order 1. =Tylostomaceæ.= Capillitium present. After the rupture
   of the peridium the remaining part of the fruit-body is elevated
   on a long _stalk_. _Tylostoma mammosum_, on heaths.

Order 2. =Lycoperdaceæ.= The fruit-body has a double peridium; the
external one at length breaks into fragments (_Lycoperdon_, _Bovista_),
or it has a compound structure of several layers (_Geaster_) and
detaches itself as a continuous envelope from the inner layer, which
is membranous and opens at its apex. The interior of the fruit-body
consists either solely of the fertile gleba (_Bovista_, _Geaster_),
or, in addition, of a sterile tissue at the base (_Lycoperdon_). A
capillitium is also present.

  [Illustration: FIG. 180.--_Lycoperdon gemmatum_ (½ nat. size).]

   _Lycoperdon_ (Puff-ball) has a sterile part at the base of the
   fruit-body which often forms a thick stalk. The surface of the
   peridium is generally covered with warts or projections. When
   young this Fungus is edible, but when ripe it is dry, and used
   for stopping the flow of blood. _L. giganteum_, which is often
   found growing in meadows, attains a considerable size, its
   diameter reaching as much as eighteen inches. _L. gemmatum_
   (Fig. 180) is covered with pyramidal warts; in woods.--_Bovista_
   has no sterile basal part; the external peridium is smooth, and
   falls away in irregular patches. _B. plumbea_, on links near the
   sea.--_Geaster_ (Earth-star) has an external peridium composed
   of several layers, which when the fruit-body opens, split into
   several stellate segments. These segments are very hygroscopic,
   and in dry weather bend backwards and so raise the inner
   peridium into the air. The inner peridium contains the spores
   and capillitia. _G. coliformis_ has several apertures in the
   inner peridium. The other species have only one regular aperture
   at the apex. _G. striatus_ has a pedicellate inner peridium,
   with conical, striped peristome. _G. fornicatus_ has an external
   peridium split into four segments. This last and several other
   species produce “mycorhiza” on the roots of Conifers.

  [Illustration: FIG. 181.--I _Hymenogaster citrinus_ (nat. size);
  II longitudinal section through _H. tener_ (× 5); III portion of
  a section of _H. calosporus_; _g_ a chamber; _h_ hymenium; _sp._
  spores; _t_ trama (× 178); IV _Rhizopogon luteolus_ (nat. size);
  V _Scleroderma vulgare_, VI section of V; VII basidia with spores
  belonging to the same Fungus.]

Order 3. =Sclerodermataceæ.= _Capillitium_ wanting. The peridium is
simple and thick, gleba with round, closed chambers, which are filled
with basidia.

   _Scleroderma_ has a corky peridium. The fruit-bodies commence
   their development under ground. _S. vulgare_ (Fig. 181 V-VII),
   has a hard, slaty-black gleba.

Order 4. =Nidulariaceæ= (=Nest-Fungi=). Small Fungi of which the
fruit-body at first is spherical or cylindrical but upon maturity
it becomes cupular or vase-like, and contains several lenticular
“peridiola” lying like eggs in a nest. The peridiola are the chambers
which contain the hymenium, covered by a thin layer of the gleba, all
the remaining portion of the gleba becoming dissolved. On decaying wood.

   _Nidularia_ has spherical fruit-bodies containing a
   large number of lenticular peridiola, embedded in a slimy
   mass.--_Crucibulum_ has fruit-bodies resembling crucibles
   with discoid peridiola, each with a spirally-twisted
   stalk.--_Cyathus_ has a fruit-body, which when open is
   campanulate, with stratified peridium, and long-stalked,
   lense-shaped peridiola.

Order 5. =Hymenogastraceæ.= Fruit-bodies tubercular, globose and
subterranean, resembling very closely the Truffles, from which they
can only be distinguished with certainty by microscopic means. The
peridium is simple, capillitium wanting, and the gleba encloses a
system of labyrinthine passages covered with a continuous hymenium.
The fruit-bodies persist for some time, and form a fleshy mass, the
spores being only set free by the decay of the fruit-body, or when it
is eaten by animals. The majority are South European. _Hymenogaster_,
_Melanogaster_, _Rhizopogon_ (Fig. 181 I-IV).


                    APPENDIX TO THE BASIDIOMYCETES:

           Basidiolichenes (Lichen-forming Basidiomycetes).

Several Fungi belonging to the Basidiomycetes have a symbiotic
relationship with Algæ exactly similar to that enjoyed by certain
Ascomycetes, and these are therefore included under the term Lichens
(p. 136). They are chiefly tropical.

Order 1. =Hymenolichenes.= To this order belong some gymnocarpic
forms: _Cora_, _Dictyonema_, _Laudatea_.[15]

Order 2. =Gasterolichenes.= To this belong some angiocarpic forms:
_Emericella_, _Trichocoma_.


                        APPENDIX TO THE FUNGI.

             Fungi imperfecti (Incompletely known Fungi).

1. The =Saccharomyces-forms= are Fungi which are only known in their
yeast-conidial form. They are _conidia of higher Fungi_ which can
multiply to an unlimited extent by budding in nutritive solutions, and
in this way maintain their _definite_ size and shape. The budding takes
place _only at the ends_ of the conidia. The wall of the conidium forms
at one or at both ends a small wart-like outgrowth, which gradually
becomes larger, and is finally separated from its mother-cell as an
independent cell, surrounded by a closed cell-wall (Fig. 182 _a_, _b_).

  [Illustration: FIG. 182.--Beer-yeast (_Saccharomyces cerevisiæ_):
  _a-b_ (× 400); _c-f_ (× 750); _c_ a cell in the process of
  forming spores; _d_ a cell with four ripe spores; _e_ the
  spores liberated by the dissolution of the cell-wall; _f_ three
  germinating spores; _g_ mycelium-like cell-chains. (× 1000: after
  Em. Chr. Hansen.)]

Under very favourable conditions multiplication occurs so rapidly that
the daughter-cells themselves commence to form buds, before they have
separated from their mother-cell, with the result that pearl-like
chains of cells are produced. When the yeast-cells have only limited
nutriment, with an abundant supply of air, at a suitable temperature,
an endogenous formation of _spores_ takes place. The protoplasm of the
cells divides into 1–4 (rarely a greater number) masses (Fig. 182 _c_,
_d_, _e_) which surround themselves with a thick cell-wall, and in this
state can withstand adverse conditions and periods of dryness lasting
for several months.

The _sporangia are not asci_ since they have no definite form, and
a definite number, form and size of spores is not found. The spores
in the different species and kinds occupy varying periods for their
development, although exposed to the same temperature, a fact of
importance in determining one from another. On germination the wall of
the mother-cell is destroyed, and each spore gives rise to a new cell,
multiplication taking place by budding (Fig. 182 _f_). The majority of
Yeast-Fungi are able to produce alcoholic fermentation in saccharine
fluids.

The most important of these Fungi is the Beer-yeast (_Saccharomyces
cerevisiæ_) with ovate, ellipsoidal or spherical cells (Fig. 182). It
is a plant which has been cultivated from time immemorial, on account
of its property of producing alcoholic fermentation in sugar-containing
extracts (wort), derived from germinating barley (malt). Carbonic
acid is also set free during this process. The “surface-yeast” (Fig.
182 _a_), which produces ordinary beer when the brewing takes place
at higher temperatures, has cell-chains; “sedimentary yeast” (Fig.
182 _b_), used in the brewing of Bavarian beer, has spherical cells,
solitary, or united in pairs. Both these and the following Yeast-Fungi
include, according to Hansen, several species and kinds.

  [Illustration: FIG. 183.--_Saccharomyces mycoderma._]

The “Ferment of Wine” (_Saccharomyces ellipsoideus_) produces wine in
the juice of grapes. Uncultivated yeast-cells are always present on
grapes; an addition of this species to the “must” is not necessary to
secure fermentation. A large number of other “uncultivated” yeast-cells
appear in breweries mixed with the cultivated ones, and cause different
tastes to the beer (_S. pastorianus_, etc.). _S. ludwigii_, found,
for instance, on the slimy discharge from Oaks, produces abundant
cell-chains on cultivation. _S. apiculatus_ is very frequently met with
on all kinds of sweet fruits, it has orange-like cells. _S. mycoderma_
has cylindrical cells, often united together in chains (Fig. 183): it
forms a whitish-gray mass (“fleur de vin”) on wine, beer, fruit-juice,
etc., standing in bottles uncorked or not entirely filled. It is
thought that this Fungus causes decomposition and oxydises the fluid
in which it is found, but it cannot produce alcoholic fermentation
in saccharine liquids, and it does not form endospores; hence it is
uncertain whether it is true _Saccharomyces_.

  [Illustration: FIG. 184.--_Oidium lactis_: _a_ branched hypha
  commonly met with; _b_ a hypha lying in milk and producing aerial
  hyphæ which give rise to oidia; _c_ a branch giving rise to
  oidia, the oldest (outermost) oidia are becoming detached from
  one another; _d_ a chain of divided cells; _e_ germinating oidia
  in different stages (slightly more magnified than the other
  figures).]

The “Dry-yeast” used in baking white bread is “surface-yeast.” In
_leaven_, a kneaded mixture of meal, barm and water, which is used for
the manufacture of black bread, _Saccharomyces minor_ is present, and
a species allied to this produces alcoholic fermentation in dough with
the evolution of carbonic acid, which causes the dough to “rise.”

2. =Oidium-forms.= Of many Fungi only the Oidium-forms are known,
which multiply in endless series without employing any higher form of
reproduction. _Oidium lactis_ (Fig. 184) is an imperfectly developed
form which frequently appears on sour milk and cheese. It can produce a
feeble alcoholic fermentation in saccharine liquids. Thrush or aphthæ
(_O. albicans_) appears as white spots in the mouths of children.
Several similar _Oidium-forms_ are parasites on the skin and hair
of human beings, and produce skin diseases, such as scurvy (_O.
schoenleinii_) and ringworm (_O. tonsurans_).

3. =Mycorhiza.= These Fungi, which have been found on the roots of many
trees and heath-plants, particularly Cupuliferæ and Ericaceæ, consist
of septate hyphæ, and belong partly to the Hymenomycetes, partly to
the Gasteromycetes. It has been shown that the Mycorhiza enters into a
symbiotic relationship with the roots of higher plants.



                             DIVISION II.

                          MUSCINEÆ (MOSSES).


In this Division a well-marked alternation of generations is
to be found. The development of the first or sexual generation
(_gametophyte_),[16] which bears the sexual organs, antheridia
and archegonia, commences with the germination of the spore, and
consists, in the Liverworts, of a thallus, but in the true Mosses of a
filamentous protonema, from which the Moss-plant arises as a lateral
bud. The second or asexual generation (_sporophyte_), developed from
the fertilised oosphere, consists of a sporangium and stalk.

=The sexual generation, the gametophyte.= The protonema in the
Liverworts is very insignificant, and not always very sharply
demarcated from the more highly developed parts of the nutritive
system. In the true Mosses the protonema is well-developed, and
consists of a branched, alga-like filament of cells, the dividing
cell-walls being always placed obliquely. In the parts exposed to the
light it is green, but colourless or brownish in those parts which are
underground (Fig. 186). The protonema is considered to be a lower form
of the stem, and grows in the same manner by means of an apical cell;
at its apex it may directly develope into a leaf-bearing stem, or these
arise from it as lateral branches (Fig. 186 _k_).

The more highly differentiated part of the vegetative system, the
“Moss-plant,” which is thus developed from the protonema, is in the
“thalloid” Liverworts generally a dichotomously-branched thallus
without any trace of leaf-structures (Fig. 194); in _Marchantia_
(Fig. 197) and others, scale-like leaves (_amphigastria_) are found
on the under surface. The higher Liverworts and the Leafy-Mosses are
differentiated into a filamentous, ramified stem with distinct leaves
arranged in a definite manner, resembling the stem and leaves of the
higher plants (Figs. 186, 195, 200).

_True roots are wanting_, but are biologically replaced by _rhizoids_.
These are developed on the stems or thallus: in the Liverworts they
are unicellular, but in the Leafy-Mosses generally multicellular and
branched. In the latter group they are considered identical with
the protonema, and may become true protonema, and new plants may be
developed from them (Fig. 186 _b_).

  [Illustration: FIG. 186.--_A_ Lower portion of a Moss-plant with
  rhizoids (_r_), one of which bears a reproductive bud (_b_). The
  dotted line indicates the surface of the ground; the portions
  projecting above this become green protonema (_p_); _k_ is a
  young Moss-plant formed on one of these. _B_ Germinating spore of
  _Funaria hygrometrica_, with exospore still attached. _C_, _D_
  Older stages of the protonema.]

The internal structure of the sexual generation is very simple. The
leaves in nearly all cases are formed of a single-layered plate of
cells; in the Leafy-Mosses, however, a midrib is very often formed, and
sometimes, also, marginal veins; and along these lines the leaves are
several layers of cells in thickness. The stem is constructed of cells
longitudinally elongated, the external ones of which are narrower and
sometimes have thicker walls than the more central ones. _Vessels are
not found_, but in several Mosses there is in the centre of the stem
a conducting strand of narrow, longitudinal cells, which represents
the vascular bundle in its first stage of development. This strand
contains elements for conveying water as well as sieve-tubes. Stomata
are entirely wanting in the sexual generation of the Leafy-Mosses; they
are found in a few Liverworts (_Marchantia_), but their structure is
not the same as in the higher plants.

VEGETATIVE REPRODUCTION takes place by gemmæ or buds which arise on
the protenema, the rhizoids, the thallus, or the shoots, and become
detached from the mother-plant; or else the protonema and the older
parts of the plant simply die off, and their branches thus become
independent plants. This well-developed vegetative reproduction
explains why so many Mosses grow gregariously. In certain Marchantiaceæ
special cupules, in which gemmæ are developed, are found on the surface
of the thallus (Fig. 197 _A_, _s-s_). Again, protonema may also arise
from the leaves, and thus the leaves may act as reproductive bodies.
Certain Mosses nearly always reproduce vegetatively, and in these
species the oospheres are seldom fertilised.

  [Illustration: FIG. 187.--_Marchantia polymorpha_: _a_ mature
  antheridium.]

  [Illustration: FIG. 188.--Spermatozoids.]

The first generation bears the SEXUAL ORGANS; both kinds are found
either on the same plant (monœcious), or on separate plants (diœcious).
In the thalloid Liverworts they are often situated on the apex of small
stems (_gametophores_), springing from the surface of the thallus.
In the Leafy-Liverworts and true Mosses the leaves which enclose the
sexual organs often assume a peculiar shape, and are arranged more
closely than the other leaves to form the so-called “Moss-flower.” The
male sexual organs are called _antheridia_. They are stalked, spheroid,
club- or egg-shaped bodies whose walls are formed of one layer of cells
(Fig. 187), enclosing a mass of minute cubical cells, each one of which
is a mother-cell of a spermatozoid. The spermatozoids are self-motile;
they are slightly twisted, with two cilia placed anteriorly (Fig. 188),
while posteriorly they are generally a trifle club-shaped, and often
bear at that part the remains of the cytoplasm, the spermatozoid itself
being _formed from the nucleus_. In the presence of water the ripe
antheridium bursts, and its contents are ejected; the spermatozoids,
being liberated from their mother-cells, swarm about in the water in
order to effect fertilisation.

  [Illustration: FIG. 189.--_Marchantia polymorpha. A_ A young,
  and _B_ a ripe archegonium with open neck. _C_ An unripe
  sporangium enclosed by the archegonium _a_: _st_ the stalk; _f_
  the wall of the sporangium. Elaters are seen between the rows of
  spores.]

The female sexual organs are termed _archegonia_. They are flask-shaped
bodies (Fig. 189), the lower, swollen portion (_venter_) having a wall,
in most cases from 1–2 cells thick, enclosing the oosphere (Fig. 189
_B_, _k_): the long neck is formed of tiers of 4–6 cells, enclosing
a central row of cells--_the neck-canal-cells_ (Fig. 189 _A_). When
the archegonium is fully developed, the walls of the neck-canal-cells
become mucilaginous and force open the neck of the archegonium. The
mucilage thus escapes, and, remaining at the mouth of the archegonium,
acts in a somewhat similar manner to the stigma and conducting tissue
of a carpel, by catching and conducting the spermatozoids to the
oosphere (Fig. 189 _B_, _m_), with whose cell-nucleus they coalesce.
With regard to the formation of the oosphere, it may further be
remarked that the lower part of the archegonium originally encloses the
so-called “central cell”; but shortly before the archegonium is ripe,
this cuts off a small portion, _the ventral-canal-cell_, which lies
immediately beneath the neck, and the larger, lower portion becomes the
oosphere.

   The organs mentioned here, antheridia and archegonia, are
   present in the Cryptogams (Pteridophyta) and the Gymnosperms.
   They have always the same fundamental structure, but with slight
   modifications of detail. These plants are therefore known as the
   ARCHEGONIATA.

The fertilisation of the Mosses cannot be effected without water. Rain
and dew therefore play a very important part in this process, and for
this end various modifications of structure are found.

  [Illustration: FIG. 190.--_Andreæa rupestris._ Longitudinal
  section through a sporangium at the time when the mother-cells
  of the spores are dividing: _p_ pseudopodium; _f_ foot; _v_
  vaginula; _h_ neck; _c_ columella; _w_ wall of the sporangium;
  _e_ external row of cells; _s_ the spore-sac; _t_ the
  spore-mother-cells; _r_ the calyptra with the neck of archegonium
  (_z_).]

  [Illustration: FIG. 191.--_Andreæa rupestris._ Transverse
  section through a ripe sporangium. In the middle is seen the
  four-sided columella, surrounded by the numerous spores,
  drawn diagrammatically. Surrounding them is seen the wall of
  the sporangium, whose outer layer of cells is thickened and
  coloured. The layer of cells is unthickened in four places (_x_),
  indicating the position of the clefts (see Fig. 193).]

Among the sexual organs, paraphyses--filamentous or club-shaped
bodies--are to be found.

=The asexual generation, the sporophyte= (Moss-fruit or sporogonium).
As the result of fertilisation the oosphere surrounds itself with a
cell-wall, and then commences to divide in accordance with definite
laws.[17] The embryo (Fig. 189 _C_) produced by these divisions
remains inside the wall _a-a_ of the archegonium (Figs. 190, 199 _D_,
_E_), and developes into the _sporogonium_, which remains attached
to the mother-plant, often nourished by it, as if the two were one
organism. The lower extremity of the sporogonium, _the foot_ (Figs.
190 _f_; 199 _D_), very often forces its way deep down into the
tissue of the mother-plant, but without an actual union taking place.
The central portion of the sporogonium becomes a shorter or longer
_stalk_ (_seta_), while the sporangium itself is developed at the
summit. At a later stage, during the formation of the spores, the
sporangium very often assumes the form of a _capsule_, and dehisces
in several ways characteristic of the various genera (Figs. 192, 193,
194, 195, 200). The basal portion of the archegonium grows for a
longer or shorter period, forming a sheath, the _calyptra_, in which
the capsule is developed, but eventually it ceases to enlarge, and
is then ruptured in different ways, but quite characteristically, in
each group. Anatomically, the asexual generation is often more highly
differentiated than the sexual; thus, for instance, stomata are present
on the sporangia of the true Mosses, but are absent in the sexual
generation.

As the capsule developes, an external layer of cells--the
_amphithecium_--and an internal mass--the _endothecium_--are
differentiated. As a rule the former becomes the wall of the capsule
while the latter gives rise to the spores. In this Division, as in
the Pteridophyta, the name _archesporium_ (Fig. 190 _t_) is given
to the group of cells inside the sporangium which gives rise to
the mother-cells of the spores. The archesporium is in general a
unicellular layer; in _Sphagnum_ and _Anthoceros_ it is derived from
the most internal layer of the amphithecium, but with these exceptions
it arises from the endothecium, usually from its most external layer.
In the true Mosses and in _Riccia_ only spore-mother-cells are produced
from the archesporium, but in the majority of the Liverworts some
of these cells are sterile and become elaters (cells with spirally
thickened walls, Figs. 196, 189), or serve as “nurse-cells” for the
spore-mother-cells, which gradually absorb the nutriment which has been
accumulated in them. In _Anthoceros_, and almost all the Leafy-Mosses,
a certain mass of cells in the centre of the sporangium (derived
from the endothecium) does not take part in the formation of the
archesporium, but forms the so called “column” or “columella” (Figs.
190, 191).

The _spores_ arise in _tetrads_, _i.e._ four in each mother-cell, and
are arranged at the corners of a tetrahedron, each tetrahedron assuming
the form of a sphere or a triangular pyramid. The mature spore is a
nucleated mass of protoplasm, with starch or oil as reserve material.
The wall is divided into two layers: the external coat (exospore) which
is cuticularized and in most cases coloured (brown, yellowish), and the
internal coat (endospore), which is colourless and not cuticularized.
On germination the exospore is thrown off, the endospore protrudes, and
cell-division commences and continues with the growth of the protonema
(Fig. 186, _B-D_).

  [Illustration: FIG. 192.--_Andreæa petrophila._ A ripe
  sporogonium: _a_ an archegonium which has been raised with the
  pseudopodium; _p_ the foot; _b_ the neck; _d-e_ the dark-coloured
  portion of the sporangium, whose outer cell-walls are
  considerably thickened; _c_-_c_ the thin-walled portions where
  the dehiscence occurs; _o_ the lower extremity of the spore-sac;
  _f_ calyptra; _g_ the apex of the sporangium. (Mag. 25 times.)]

  [Illustration: FIG. 193.--_Andreæa petrophila._ An empty capsule;
  the calyptra has fallen off. (Mag. 25 times.)]

   The morphological explanation which Celakovsky has given of
   the sporogonium, and which is not at all improbable, is, that
   it is homologous with an embryo consisting of a very small
   stem-portion and a terminal spore-producing leaf. This will be
   further explained in the introduction to the Flowering-plants
   (p. 236).

In the Liverworts the young sporogonium lives like a parasite, being
nourished by the sexual generation (only in _Anthoceros_ has it a
slight power of assimilation). In the Leafy-Mosses, on the other
hand, with regard to the power of assimilation, all transitions are
found from abundant assimilation (_Funaria_, _Physcomitrium_) to
almost complete “parasitism” (_Sphagnum_, _Andreæa_). In the majority
of the operculate Mosses the sporogonium has a more or less perfect
system of assimilation, and is able itself to form a large portion of
the material necessary for the development of the spores, so that it
chiefly receives from the sexual generation the inorganic substances
which must be obtained from the soil. The more highly developed the
assimilative system of the sporogonium, the more stomata are present.

   APOSPORY. In some operculate Mosses it has been possible to
   obtain a protonema with small Moss-plants from the seta, when
   severed from its Moss-plant, and grown on damp sand.

The Mosses are the lowest plants which are provided with stem and
leaf. They are assigned a lower place when compared with the higher
Cryptogams, partly because there are still found within the Division
so many forms with a mere thallus, partly because typical roots are
wanting and the anatomical structure is so extremely simple, and partly
also because of the relation between the two generations. The highest
Mosses terminate the Division, the Muscineæ and Pteridophyta having had
a common origin in the Algæ-like Thallophyta.

They are divided into two classes:--

HEPATICÆ, or Liverworts.

MUSCI FRONDOSI. True Mosses or Leafy-Mosses.


                  Class 1. =Hepaticæ= (=Liverworts=).

The protonema is only slightly developed. The remaining part of the
vegetative body is either a prostrate, often dichotomously-branched
thallus, pressed to the substratum (thalloid Liverworts), with
or without scales on the under side (Figs. 194, 197); or a thin,
prostrate, creeping stem, with distinctly-developed leaves, which are
borne in two or three rows (Figs. 195, 198), viz., two on the upper
and, in most cases, one on the under side. The leaves situated on the
ventral side (amphigastria) are differently shaped from the others
(Fig. 198 _a_), and are sometimes entirely absent. In contradistinction
to the Leafy-Mosses, stress must be laid on the _well-marked
dorsiventrality_ of the vegetative organs; _i.e._ the very distinct
contrast between the dorsal side exposed to the light and the ventral
side turned to the ground. Veins are never found in the leaves.

The _ventral part of the archegonium_ (calyptra) continues to grow for
some time, and encloses the growing embryo, but when the spores are
ripe it is finally ruptured by the sporangium, and remains situated
like a sheath (_vaginula_) around its base. The sporangium opens,
longitudinally, by _valves_ or _teeth_ (Fig. 194, 195, 197 _b_), very
rarely by a lid, or sometimes not at all. _A columella is wanting_
(except in _Anthoceros_, Fig. 194); but on the other hand, a few of the
cells lying between the spores are developed into _elaters_ (Fig. 196),
_i.e._ spindle-shaped cells with spirally-twisted thickenings, which
are hygroscopic, and thus serve to distribute the spores. (They are
seen in Fig. 189 _C_, not yet fully developed, as long cells radiating
from the base of the sporangium. They are wanting in _Riccia_).

  [Illustration: FIG. 194.--_Anthoceros lævis_ (nat. size): _K_-_K_
  capsules.]

  [Illustration: FIG. 195.--_Plagiochila asplenioides_: _a_ unripe,
  and _b_ an open capsule; _p_ involucre. The ventral edge of each
  leaf is higher than its dorsal edge, and covered by the dorsal
  edge of the next one.]

  [Illustration: FIG. 196.--An elater with two spores.]

   Round the entire archegonium, (or group of archegonia, when
   several are developed on the same receptacle) a sheath--the
   _involucre_--is often formed, which persists, and encloses the
   base of the stalk of the sporangium, together with the sheath
   of the archegonium (Fig. 195 _p_). In the Marchantiaceæ each
   archegonium is enclosed in a loose investment, the perigynium,
   which is developed as an outgrowth from the cells of its stalk.

The majority of the Liverworts are found in damp and shady places,
pressed to the substratum; a few are found floating in fresh water.


                       Family 1. =Marchantieæ.=

This embraces only forms with a thallus, which is more or less
distinctly dichotomously branched, in some, one or two rows of thin
leaves are situated on its under surface. On the upper surface of the
thallus are found large air-chambers.

Order 1. =Ricciaceæ.= The sporogonia are, with the exception of a few
genera, situated singly on the surface of the thallus, and consist only
of a capsule without foot or stalk. They always remain enclosed by the
wall of the archegonium (calyptra), and open only by its dissolution.
Elaters are not developed. Some genera are found floating like
Duckweed.--_Riccia glauca_ grows on damp clay soil. _R. fluitans_ and
_R. natans_ float in stagnant waters.

  [Illustration: FIG. 197.--_Marchantia polymorpha. A_ Female
  plant (nat. size): _a_ and _b_ are archegoniophores in various
  stages of development; _s_ cupules with gemmæ (see page 183). _B_
  An archegoniophore seen from below, the short-stalked sporangia
  are seen placed in 8–10 double rows. _C_ Male plant, with a
  young and an older antheridiophore. _D_ Antheridiophore halved
  vertically to show the antheridia (_h_); _m_ the aperture of the
  pits in which they are sunk--the older ones to the left, the
  younger to the right.]

Order 2. =Corsiniaceæ.= (Not native). Intermediate forms between the
preceding and the following order. In internal and external structure
mainly resembling the Marchantiaceæ. _Corsinia_; _Boschia_.

Order 3. =Marchantiaceæ=, are large, fleshy forms. The surface of the
thallus is divided into small rhombic areas, in the centre of each of
which is found a large, peculiarly constructed stoma (Fig. 197 _A_);
beneath each of these a large air-cavity is to be found. From the floor
of the air-cavity a number of alga-like cells project into it; these
contain chlorophyll and are therefore the assimilating cells. The
antheridia and archegonia are each found aggregated on specially formed
branches (somewhat resembling Mushrooms) projecting from the surface of
the thallus. The antheridia are developed on the upper surface (Fig.
197 _C_, _D_) and the archegonia on the lower (Fig. 197 _A_, _B_),
near the centrally-placed stalk.

_Marchantia polymorpha_ is diœcious (Fig. 197), and very common on damp
places. _Lunularia_ (South Europe), frequently found on flower-pots in
conservatories; _Preissia_, _Fegatella_, _Reboulia_, _Targionia_.


                       Family 2. =Anthoceroteæ.=

   These have an entirely leafless, fleshy, flat, and
   irregularly-shaped thallus. In its intercellular chambers
   Nostoc-colonies are often found, which have forced their way
   through the stomata situated on the under side. The antheridia
   and archegonia arise from the cells lying inside the thallus.
   The capsule resembles a long, thin pod; it has two valves and a
   columella. _Anthoceros_ (_A. lævis_, Fig. 194, and _punctatus_).


                      Family 3. =Jungermannieæ.=

Some forms in this family have a thallus in which leaf-like structures
are found (_Blasia_), while in others (_e.g. Metzgeria_, _Pellia_,
_Aneura_) they are entirely absent. The majority, however, have
round, thick stems, bearing dorsally two rows of leaves, and one row
ventrally. Some of these have the leaves “underlying” (Fig. 195), while
in others (Fig. 198) they are “overlying.” (See Figs. 195, 198, with
explanation).

The sporangia are spherical, stalked, and situated singly on the apex
of the branches, and open by four valves (in _Sphærocarpus_ they
are indehiscent).

  [Illustration: FIG. 198.--_Frullania dilatata._ Portion of a
  branch seen from the under side: _r_ and _b_ are the anterior
  and posterior edges of the same dorsal leaf; _a_ ventral leaves
  (amphigastria). The dorsal leaves are “overlying,” _i.e._ the
  anterior edge of the leaf overlaps the posterior edge of the
  preceding one.]

All the species in this family were formerly reckoned as belonging to
one genus, _Jungermannia_, but now they are divided into several,
arranged as follows:--

I. ANACROGYNÆ. The archegonia are situated on the upper side of the
thallus or stem, _placed laterally_, and covered by an “involucre,”
formed by the calyptra together with the tissue of the stem or thallus.

a. ANELATEREÆ. Without any elaters: _Sphærocarpus_, _Riella_.

b. ELATEREÆ. α. Thalloid: _Aneura pinguis_, in damp situations;
_Metzgeria furcata_, on trees; _Pellia epiphylla_, in damp situations;
_Blasia pusilla_, on damp clay soil, in the shade (scales are present
on the thallus). β. Foliose and not dorsiventral: _Haplomitrium
hookeri_.

II. ACROGYNÆ. The apex of the stem or of certain branches is adapted
for the formation of female shoots. The archegonia are most frequently
aggregated on the apex of the shoots, and are encircled by their leaves
(perichætium). Between these and the archegonia, enclosing the latter,
a peculiar cup-shaped organ (the involucre) is formed. This group only
includes leaf-bearing genera: _Frullania_, _Radula_, _Madotheca_,
_Ptilidium_, _Calypogeia_, _Lepidozia_, _Mastigobryum_, _Lophocolea_,
_Jungermannia_, _Scapania_, _Plagiochila_.


           Class 2. =Musci frondosi or veri (True Mosses).=

In this class the protonema is well developed, and resembles a
branched filamentous Alga, from which it can be easily distinguished
by its oblique septa (in _Sphagnum_ it is a cellular expansion). The
Moss-plant, which is developed directly from the protonema, generally
has an erect, thick, cylindrical stem similarly constructed on all
sides. The leaves are arranged spirally, the most frequent divergence
being 2/5 or 3/8 (Fig. 200 _A_). A midrib is often present and also
marginal veins formed by longitudinally elongated cells; at these veins
the leaf is more than one layer in thickness. In _Leucobryum_ the
leaves are generally constructed of more than one layer.

The stem grows by means of a three-sided, pyramidal, apical cell which
gives rise to three rows of segments, each segment forming a leaf. The
lateral branches arise from the lower portions of the segments, the
upper portion of which does not take any part in the construction of
the leaf. From their mode of origin the branches are not axillary, and
differ in this respect from the Flowering-plants.

The ventral portion of the archegonium is very early ruptured _at its
base_ by the growing sporogonium, upon which it remains, and it is thus
raised into the air, forming a “hood,” the calyptra (Figs. 192; 200
_B_). In the Sphagnaceæ the hood is not present; in this order, as in
the Liverworts, the archegonium remains at the base of the sporogonium.
The sporangium opens by circumsessile dehiscence, the upper portion
(_operculum_) being separated along a specially constructed ring of
cells, and falls off like a “lid” (Fig. 200). Only in a few forms
(families 2 and 3) does any variation of this take place. Elaters are
never found, but (with the exception of _Archidium_) there is always
present in the sporangium a central mass of cells, the _columella_,
which take no part in the formation of the spores. The columella, in
some, does not reach quite to the operculum and in these cases the
spore-sac is bell-shaped and covers the columella (_Andreæa_, Fig. 190;
_Sphagnum_, Fig. 199 _D_); but in the majority of Mosses the columella
extends to the lid, so that the space containing the spores becomes a
hollow cylinder.

The _sporangium_ is generally raised on a long stalk; in the great
majority this stalk is formed from the lower half of the oospore and
belongs to the asexual generation--it is then known as the _seta_. In
_Andreæa_ and _Sphagnum_ the seta is very short, and the sporangia are
raised upon a long stalk (_pseudopodium_) developed from the summit
of the sexual generation (Figs. 190, 192). In the latter figure an
archegonium (_a_) is seen attached to the pseudopodium, having been
carried up with this during the course of its development. The summit
of the pseudopodium is enlarged to embrace the foot of the sporogonium
(Figs. 192, 199 _D_).

   A. The sporangium is supported on a pseudopodium; the columella
   does not extend to the operculum.

  [Illustration: FIG. 199.--_Sphagnum acutifolium._--_A_ The
  upper portion of a plant: _a_ branches with antheridia; _ch_
  branches with terminal archegonia and perichætia; _b_ the
  upper stemleaves. _B_ A male branch whose leaves are partly
  taken off in order to show the antheridia. _C_ Group of three
  archegonia: the central one (_a_) is formed from the apical
  cell. _D_ Sporogonium in longitudinal section: the broad foot
  (_sg’_) is sunk in the vaginula, _v_; _c_ calyptra; _ar_ neck
  of the archegonium; _ps_ pseudopodium. _E_ ripe sporangium with
  operculum, and the remains of the archegonium situated on the
  pseudopodium which is still surrounded by the perichætium; to the
  left is a barren branch. _F_ Portion of a foliage-leaf seen from
  above: _l_ perforations; _b_ chlorophyll-containing cells; _s_
  spiral thickenings.]


                  Family 1. =Sphagneæ (Bog-Mosses).=

The protonema has been already described. The stem is regularly
branched owing to the fact that a branch, or collection of branches,
arises at every fourth leaf. These branches are closely covered with
leaves, some are erect, while others hang down and surround the stem.
No rhizoids are developed. These Mosses are of a whitish-green colour,
and when water is present are always saturated with it like a sponge,
the reason for this being found in the construction of the stem and
leaves. The stems are covered by an external layer of large clear
cells, without chlorophyll, but with annular or spiral thickenings
on the walls, which are also perforated by large holes. By means of
capillary attraction, water is thus raised to the summit of the stem.
Similarly constructed cells are also found in the leaves, but they
are surrounded by a net of very narrow, chlorophyll-containing cells
(Fig. 199 _F_), whose colour is thus to a great extent lost amongst
those which are colourless. This anatomical structure is an essential
condition for the formation of peat. The Bog-Mosses grow by preference
on moors, which they cover with a thick carpet saturated with water.
The lower extremities of the plants perish very rapidly, and gradually
become converted into peat, and the branches thus separated from each
other become independent plants. The sporangia (Fig. 199 _D_, _E_) are
spherical, but with a very short stalk. They open by a _lid_, but have
no _annulus_. The _archegonium_ (Fig. 199 _C_) persists at the _base of
the sporogonium_ as in the Liverworts. Only one genus, _Sphagnum_.


                       Family 2. =Schizocarpeæ.=

   The Mosses which constitute this family are of a brownish-black
   colour and are found living on rocks. The sporangium resembles
   that of the Liverworts inasmuch as it opens by four valves, but
   these continue attached to each other at the apex as well as at
   the base (Fig. 193).--There is only one genus: _Andreæa_.

   =B.= The stalk is formed from the lower portion of the
   sporogonium. The columella is continued to the summit of the
   sporangium and united with it (_Archidium_ has no columella.)


                      Family 3. =Cleistocarpeæ.=

   The fruit does not dehisce in the regular way, but the spores
   are liberated by decay. They are small Mosses which remain
   in connection with their protonema until the sporangium is
   mature. The archegonium remains sessile at the base of the
   short capsule-stalk, and is not raised into the air (compare
   Hepaticæ).--_Phascum, Ephemerum, Archidium, Pleuridium._


                       Family 4. =Stegocarpeæ.=

To this belong the majority of the Mosses, about 3,000 species.

The capsule opens as in _Sphagnum_ by means of a _lid_ (_operculum_),
which is often prolonged into a beak. Round the mouth of the opened
capsule, a number of peculiar yellow or red teeth are to be found.
These constitute the _peristome_; their number is four, or a multiple
of four (8, 16, 32 or 64). The form and thickenings of these teeth are
widely different, and on this account are used by Systematists for
the purposes of classification. In some Mosses (Fig. 200 _C_, _D_)
there is a double row of teeth. Except in _Tetraphis_ they are not
formed from entire cells, but from the strongly thickened portions of
the wall of certain layers of cells belonging to the lid, and persist
when this falls off. They are strongly hygroscopic, and assist greatly
in the ejection of the lid, in which operation they are considerably
aided by a ring of elastic cells with thickened walls, situated in the
wall of the lid near the base of the teeth. This ring is known as the
_annulus_. The archegonium is raised into the air like a hood, the
calyptra, which either covers the sporangium on all sides (having the
shape of a bell), or is split on one side (Fig. 200 _B_, _h_).

   Among peculiar forms may be mentioned: _Splachnum_, which is
   especially remarkable for the collar-like expansion at the base
   of the capsule. _Fissidens_ deviates in having a flat stem and
   leaves arranged in two rows. The leaves are boat-shaped and
   half embrace the stem.--_Schistostega_ has two kinds of stems.
   The barren ones resemble Fern-leaves; they have two rows of
   leaves, which are attached together vertically, are decurrent
   and coalesce at their bases. The fertile ones have an ordinary
   appearance.--_Tetraphis_: the peristome is composed of four
   teeth, which are formed from entire cells. _T. pellucida_ has
   peculiar gemmæ.

The family is divided into two groups: the Musci acrocarpi, the growth
of whose main axis is limited and terminated by the formation of the
sexual organs; and the Musci pleurocarpi, whose sporogonia are situated
on special lateral shoots, while the growth of the main axis is
unlimited.

  [Illustration: FIG. 200.--_A Hypnum populeum_. _B_ and _C_
  Sporangia, with hood (_h_), and operculum (_l’_), and without
  these (_C_), showing the peristome (_p_). _D_ The mouth of the
  capsule of _Fontinalis antipyretica_.]


                            A. =Acrocarpi.=

   Order 1. =Weisiaceæ.= Peristome, with 16 teeth arranged in
   one series, rarely wanting. Leaf with midrib. _Campylopus_,
   _Dicranum_ (_D. scoparium_, common in forests), _Dicranella_,
   _Cynodontium_.--_Weisia_, _Gymnostomum_ (no peristome),
   _Systegium_.

   Order 2. =Leucobryaceæ.= Peristome with 16 teeth. Leaves with
   three or more layers of cells, of which the external ones are
   air-conducting and perforated (as in the Sphagneæ), the middle
   one containing chlorophyll. _Leucobryum._

   Order 3. =Fissidentaceæ.= Peristome as in the preceding ones.
   The leaves are arranged in two rows on the plagiotropic shoots;
   in _Fissidens_ the midrib of the leaf bears wing-shaped
   outgrowths. _Conomitrium, Fissidens._

   Order 4. =Seligeriaceæ.= Peristome with 16 undivided teeth. Very
   small Rock-mosses. _Seligeria.--Blindia._

   Order 5. =Pottiaceæ.= Peristome with 16 teeth, which are
   divided almost to the base, or with 32 teeth. Calyptra
   hood-like.--_Barbula (B. muralis, B. ruralis), Trichostomum,
   Leptotrichum.--Ceratodon purpureus.--Distichium.--Pottia._

   Order 6. =Grimmiaceæ.= The leaf-cells are often papillose;
   in the upper portion of the leaf, small, and of roundish
   shape. The calyptra is most frequently hood-like or conical.
   _Eucalypta._--_Orthotrichum_, often with short-stalked capsule,
   is found on trees.--_Coscinodon._--_Hedwigia._--_Grimmia_,
   _Racomitrium_.--_Cinclidotus._

   Order 7. =Schistostegaceæ.= The stems are of two kinds (see
   above); _Schistostega osmundacea_, in caves, has a bright
   emerald protonema.

   Order 8. =Splachnaceæ.= The capsule has a large, collar-like
   neck (see above). _Splachnum_ (especially on manure).

   Order 9. =Funariaceæ.= Capsule pear-shaped. _Funaria_ (_F.
   hygrometrica_ has a very hygroscopic seta, becoming twisted
   when dry, and straightening with moisture); _Physcomitrium_;
   _Discelium_.

   Order 10. =Bryaceæ.= The capsule is thicker towards
   the apex; most frequently pendulous. _Philonotis_,
   _Bartramia_.--_Aulacomnium._--_Paludella
   Meesea._--_Mnium._--_Bryum_, _Webera_, _Leptobryum_.

   Order 11. =Polytrichaceæ.= Single peristome, formed by 16,
   32, or 64 teeth. Leaves with longitudinal lamellæ on upper
   surface.--_Polytrichum_ has long, hairy calyptra. _Catharinea_
   (_C. undulata_, in forests).

   Order 12. =Georgiaceæ.= Peristome with 4 teeth (see above).
   _Tetraphis_ (_T. pellucida_ has gemmæ).

   Order 13. =Buxbaumiaceæ.= Capsule asymmetrical; double
   peristome: the interior one conical, with 16 or 32 longitudinal
   folds.--_Buxbaumia_ (_B. aphylla_); _Diphyscium_.


                           B. =Pleurocarpi.=

   Order 14. =Fontinalaceæ.= Long, floating Water-Mosses.
   _Fontinalis_ (_F. antipyretica_ is found in streams).
   _Dichelyma._

   Order 15. =Hookeriaceæ.= _Pterygophyllum._

   Order 16. =Leskeaceæ.= Dull-looking Mosses, with papillose or
   warted leaves.--_Thuidium_, _Thuja_-like with regularly arranged
   1–3 doubly pinnate stems; _Anomodon_, _Leskea_.

   Order 17. =Pterogoniaceæ.= _Pterigynandrum filiforme_, etc.

   Order 18. =Fabroniaceæ.= _Anacamptodon._

   Order 19. =Neckeraceæ.= Stems most frequently with flat, leafy
   branches. The leaves are smooth, never with longitudinal
   folds.--_Neckera._

   Order 20. =Hypnaceæ.= The leaves are smooth with square,
   often bladder-like, cells at the edge. _Hylocomium_ (_H.
   splendens_, _H. triquetrum_); _Hypnum_; _Brachythecium_;
   _Plagiothecium_.--_Eurhynchium._--_Homalothecium_, _Isothecium_,
   _Orthothiecium_, _Homalia_.--_Climacium_, _Lescuræa_, _Leucodon_.

   The Mosses occur all over the globe. Many are found in great
   numbers, and growing thickly massed together, they form an
   important feature in landscapes (for example _Sphagnum_ and
   _Polytrichum_ in the Arctic Tundra). In the Northern and
   Arctic regions the Mosses are very plentiful, and often form a
   considerable part of the vegetation, while in the Tropics they
   are insignificant.

   Species of _Hypnum_ and _Polytrichum_, like _Sphagnum_, play an
   important part in the formation of peat.



                             DIVISION III.

                  PTERIDOPHYTA (VASCULAR CRYPTOGAMS).


The alternation of generations is as distinct in this Division as in
the Mosses, but the sexual generation consists of only a small thallus,
the prothallium, which bears directly the sexual organs, _antheridia_
and _archegonia_; and the asexual generation, which arises from the
fertilisation of the oosphere, is no longer a single short-lived
sporangium, but a highly developed, generally perennial, plant provided
with stem, leaves and _true roots_ (Ferns, Horsetails, etc.), the
sporangia being borne on the leaves. In this latter generation the
tissues are differentiated into epidermis, ground tissue and vascular
tissue; in the last named the bundles are closed, and in the majority
of cases concentric.

The =sexual generation=, =gametophyte=, or =prothallium=, is _always
a thallus_, although not always green and leaf-like (Figs. 205, 215,
222, 229, 235, etc.) It is very small, even in cases where it attains
the greatest development, and consists only of parenchymatous cells.
The prothallium is nourished by hair-like roots (rhizoids) and has
only a transitory existence, dying soon after the fertilisation of its
oosphere.

The ANTHERIDIA exhibit great variations in structure which, however,
must be considered as modifications of the fundamental type which is
found in the Mosses. These modifications will be mentioned under the
various families. The _spermatozoids_ are always spirally-coiled,
self-motile, protoplasmic bodies, with most frequently a large number
of fine cilia on the anterior end (Figs. 206, 223, 234). They are
formed principally from the nucleus of the mother-cell, and portions of
the cytoplasm often remain for a time attached to their posterior end.

The ARCHEGONIA are more uniform throughout the entire Division,
and more closely resemble those of the Mosses. They are, as in the
previous Division, principally flask-shaped; but the central portion,
which encloses the oosphere, is always embedded in the tissue of the
prothallium, so that the neck, which is formed of 4 rows of cells,
projects above the surface (Figs. 201 ^3, 222 _h_). The development
of the archegonium in a Fern is seen in the accompanying figure (Fig.
201). The archegonium is developed from a surface cell, which divides
into three cells by two walls in a direction parallel to the surface
of the prothallium (Fig. 201). The most internal cell becomes the
ventral portion of the archegonium. The external one (_b_) divides
perpendicularly to the surface of the prothallium into four cells,
which again divide parallel to the surface and form the neck (_b_,
in 2 and 3). The intermediate cell projects upwards into the neck
and divides into two, the lower one, after the separation of the
ventral canal-cell, becoming the _oosphere_, and the upper one the
_neck-canal-cell_ (_c_, in 2 and 3).

  [Illustration: FIG. 201.--_Pteris serrulata._ Development of
  archegonia.]

As in the Mosses, the divisional walls of the neck-canal-cells become
mucilaginous, causing the rupture of the neck of the archegonium.
Fertilisation takes place as in the Mosses, and the passage of the
spermatozoids, along the neck, to the oosphere, has been observed.
Water (rain or dew) is similarly necessary for the movements of the
spermatozoids, and hence for fertilisation. The other classes of the
Division chiefly deviate from the Ferns in having the archegonium sunk
deeper into the prothallium, and the neck reduced in length (compare
Fig. 201 with Figs. 216, 222, 235, 236).

According to the nature of the spores, the three classes of the
Vascular Cryptogams are each divided into isosporous and heterosporous
groups.

I. The =isosporous= Vascular Cryptogams have _only one kind of spore_.
The prothallium developed from this is in some cases monœcious, bearing
both antheridia and archegonia; but in others there is a distinct
tendency for each prothallium to bear only antheridia or archegonia
(diœcious)--true Ferns and _Lycopodium_.

In _Equisetum_ there is only one kind of spore, but two kinds of
prothallia are developed, one of which bears only antheridia (male),
the other only archegonia (female); but the one that bears antheridia
may be transformed into the one that bears archegonia and vice versa.

II. In the higher group, =heterosporous= Vascular Cryptogams
(_Selaginella_ and _Isoëtes_, etc.), there are two distinct kinds
of spores, the _small_, microspores, and the _large_, macrospores.
The _microspores_ are male, and produce prothallia which bear only
antheridia. The _macrospores_ are female, and produce prothallia which
bear only archegonia.

Corresponding to this difference in the spores, there is also found
a difference in the development of the prothallium. In the Isosporeæ
the prothallium is large, and either green, leaf-like, and provided
with rhizoids (most of the Ferns, Horsetails, etc.), or subterranean,
pale-coloured, and globular (_Ophioglossum_, _Lycopodium_). It lives
vegetatively for a fairly long time, and generally produces a large
and varying number of archegonia and antheridia. The prothallium in
the Heterosporeæ is gradually more and more reduced, its independent
and vegetative life becomes of less and less importance, it becomes
more dependent on the mother-plant, and projects from the spore very
slightly, or not at all. The antheridia and archegonia become reduced
in number to one, and also degenerate in point of development.

It may here be remarked that the gradual development of the asexual
generation, the development of the two kinds of spores, and the
progressive reduction of the prothallium and sexual organs which
is found in this Division, is continued to the Gymnosperms and
Angiosperms. The microspores are in these called pollen-grains, and
the male prothallium is very rudimentary. The macrospores are termed
embryo-sacs, and the female prothallium, the endosperm.

The =asexual generation=, =sporophyte=. When the oosphere, which in
this case as in all others is a primordial cell, is fertilised, it
surrounds itself with a cell-wall and commences to divide into a number
of cells, to form the embryo.

   The first dividing wall (basal wall) is nearly horizontal, and
   in the direction of the longitudinal axis of the archegonium.
   The next wall is vertical, and the next perpendicular to the
   other two. The oosphere, therefore, is now divided into eight
   octants by these three walls. The basal wall divides the
   embryo into a hypobasal and an epibasal half. From the first
   one, by continued divisions, the first root is developed; from
   the latter, the stem and leaves. After the formation of the
   octants the development proceeds in somewhat different ways in
   the various classes. In addition to the stem, leaf, and root,
   a “foot” is developed from the hypobasal half which remains
   enclosed in the prothallium, and conveys nourishment from the
   prothallium to the young plant until it is able to sustain
   itself (Fig. 202). The formation of these members in the embryo
   depends on the position of the oosphere in the archegonium and
   prothallium, and is independent of gravity.

  [Illustration: FIG. 202.--_Adiantum capillus veneris._ Vertical
  section through a prothallium (_f f_), with a young plant
  attached on its under side (mag. about 10 times); _r_ the first
  root, and _b_ the first leaf of the young Fern-plant; _m_ the
  foot. In the angle between _m_ and _b_ lies the apex of the
  stem: _h_ the rhizoids of the prothallium; _æ æ_ unfertilised
  archegonia.]

In the Mosses the asexual generation is the sporogonium, which is
limited in its development and in a great measure dependent upon the
sexual generation, upon which it is situated; but in the Pteridophyta
this generation is an independent and highly developed plant,
provided with stem, leaf, and true roots, and has in many instances
an unlimited development. The Pteridophyta are the lowest Division
with _true roots_. The root which is first formed is very similar in
nature to the primary root of the Monocotyledons; it very soon dies
and is replaced by others which are more permanent, and developed
upon the stem (adventitious roots); roots are wanting in _Salvinia_,
_Psilotum_, and some Hymenophyllaceæ. The differentiation is, however,
not so complete as in the Flowering-plants, and so many leafy forms are
not found. The various members of these plants are anatomically much
higher than in the Mosses, having an epidermis, a ground tissue with
variously differentiated cells, and a highly developed vascular system.
The vascular bundles, like those in the Monocotyledons, are without
cambium, and closed; they are therefore incapable of any increase in
thickness. In general the bundles are concentric, with the bast round
the wood (Fig. 203). The wood is almost entirely made up of scalariform
tracheides.

   In _Isoëtes_ a secondary thickening takes place by a cambium,
   which is formed inside the cortex, constructing secondary
   cortex to the exterior, and secondary wood towards the
   interior.--_Botrychium_ has also a thickening growth. Collateral
   vascular bundles occur in _Osmundaceæ_, _Equisetaceæ_, and the
   leaves of many _Polypodiaceæ_, etc.

  [Illustration: FIG. 203.--Portion of the stem of a Fern. Above is
  seen the transverse section, with vascular bundles of different
  form and size. The rhombic figures on the side of the stem are
  leaf-scars.]

It is a point of special interest, that the gigantic forms of Ferns,
Equisetums, and Club-Mosses (which flourished in earlier geological
periods, when these classes attained their highest development)
possessed some means of increasing in thickness.

The _sporangia_ are in all cases _capsule-like_, and burst open when
ripe to eject the spores. They are nearly always situated on the leaves
(in _Lycopodiaceæ_, in the axils of the leaves, or above these, on the
stems themselves). In some forms (LEPTOSPORANGIATÆ), the sporangia are
developed from a single epidermal cell; in others (EUSPORANGIATÆ),
from a group of epidermal cells, or from cells which lie beneath the
epidermis. In the first group a primitive mother-cell (archesporium)
is formed, which divides commonly into sixteen special mother-cells.
In the latter group, on the other hand, a number of primitive
spore-mother-cells are developed. In each sporangium three different
tissues are generally developed; an innermost _sporogenous_ one (_s_ in
Fig. 204 _A_), which arises from the archesporangium; an outermost one,
which forms the _wall_ (_a_), and may be one or, more rarely, several
layers in thickness; and an intermediate one, the _tapetum_ (Fig. 204
_A_, _B_, _b t_), which is rich in protoplasm, and whose cells are
dissolved so that the spores float freely in the fluid thus provided.
The spores arise as in the Mosses (in tetrads), by the cross-division
of the special mother-cells, and according to the manner in which they
are arranged in the mother-cell have either a tetrahedral form, with
a large base resembling a segment of a ball, or are oblong (bilateral
spores). Their construction is the same as in the Mosses (p. 187).

  [Illustration: FIG. 204.--_Selaginella inæqualifolia. A_ A
  young sporangium, which may develope either into a macro-, or a
  microsporangium. _B_ A microsporangium.]

The spore-formation in its earliest commencement takes place in the
same way in the Isosporous and the Heterosporous Vascular Cryptogams;
but from a certain point, after the tetrahedral division, a difference
occurs with regard to the macrosporangia. All the spores formed in the
microsporangium may complete their development; but those which are
formed in the macrosporangium are generally aborted, with the exception
of one or four, and these consequently attain a much larger size (see
Fig. 239.--The series to the left are microsporangia; those to the
right, macrosporangia).

   APOGAMY. In some Ferns (_Pteris cretica_; _Aspidium filix mas_,
   var. _cristatum_; _A. falcatum_; _Todea africana_) the young
   plant is not developed as a consequence of fertilisation, but as
   a bud from the prothallium. This is known as apogamy, or loss of
   the power of sexual reproduction. The antheridia are generally
   more or less developed; archegonia are entirely wanting in _Asp.
   filix mas_, var. _cristatum_. This variety has probably only
   become apogamous through cultivation. Many specimens of _Isoëtes
   lacustris_, in a lake in the Vosges mountains, produce in the
   place where the sporangia are usually found, a vegetative shoot
   which grows into a new plant, so that the sexual generation is
   wanting in this case. Some specimens have sporangia on some
   leaves, and shoots on others.

   Apospory, or the formation of prothallia instead of sporangia
   and spores on the leaves, is found in _Athyrium filix
   femina_, var. _clarissimum_. In this case the development
   of the sporangia proceeds only to a certain point, and from
   these arrested sporangia the prothallia are produced. Normal
   sporangia are entirely wanting in this variety, and in _Aspidium
   angulare_, var. _pulcherrimum_, sporangia are completely
   wanting. Compare the Mosses (page 188).

The Vascular Cryptogams are divided into _three large classes_,
in each of which a progressive development can be traced from the
isosporous to the heterosporous forms, but some of these are now only
known as fossils.

Class 1. =Filicinæ= (=Ferns=).--The stem is small in comparison with
the leaves, and branches only seldom, and then by lateral shoots. The
leaves are scattered, large, often deeply divided, and of various
highly developed forms. The undeveloped leaves are rolled up in the
bud, having what is termed circinate venation. The sporangia are
situated on the edge or on the lower side of the leaves, those on
which the sporangia are borne (_sporophylls_) being often the ordinary
foliage-leaves; but in a few cases the fertile differ from the barren
ones (a higher stage in development). The fertile leaves are not
confined to definite parts of the shoot, and do not limit its growth.
The archesporium is most frequently unicellular.

_A_. =Isosporous=: Sub-Class 1. Filices (True Ferns).

_B_. =Heterosporous=: Sub-Class 2. Hydropterideæ (Water Ferns).

Class 2. =Equisetinæ= (=Horsetails=), in its widest meaning.--The
leaves in this class are small in comparison with the stem. They are
arranged in whorls, and unite to form a sheath. The sporangia are
situated on specially modified, shield-like leaves, which are closely
packed together and form a “cone.” The cone is borne terminally, and
limits the growth of the shoot. The sporangia are developed from a
large group of epidermal cells, the archesporium being unicellular. The
branches are arranged in whorls, and develope acropetally.

_A_. =Isosporous=: Sub-Class 1. Equisetaceæ. Existing forms.

_B_. =Heterosporous=: Sub-Class 2. Extinct forms.

Class 3. =Lycopodinæ= (=Club-Mosses=).--Roots generally branching
dichotomously. The leaves are scattered or opposite, and in proportion
to the stem very small, undivided, and simple. They are scale-like and
triangular, tapering from a broad base to a point. The sporangia are
situated singly (except in _Psilotaceæ_), and almost in every case on
the upper side of the leaf or in the axil of a leaf; but in some cases
they are borne on the stem, just above the leaf-axil. The sporangia
arise from groups of epidermal cells. The sporophylls are often
modified, and differ from the foliage-leaves; they are then arranged in
cones placed terminally on branches, thus limiting their growth.

_A_. =Isosporous=: Sub-Class 1. Lycopodieæ.

_B._ =Heterosporous=: Sub-Class 2. Selaginelleæ.


                    Class 1. =Filicinæ= (=Ferns=).

The characteristics of this class have already been given on page 204.

The class is divided into two sub-classes:--

1. The TRUE FERNS, FILICES, have one kind of spore which generally
developes monœcious prothallia, relatively large and green. The
sporangia are most frequently situated in groups (_sori_), which are
often covered but not enclosed by an _indusium_.

2. WATER FERNS, HYDROPTERIDÆ, have microsporangia with many (4 × 16)
microspores, and _macrosporangia, each with one macrospore_. The
prothallium is small, and projects but slightly from the germinating
spore. The sporangia are situated in groups (_sori_), which are either
enclosed by an indusium, or enveloped in a portion of a leaf, to form
“fruits” termed _sporocarps_.

   The old name for the Hydropterideæ, “Rhizocarpeæ,” _i.e._ the
   “root-fruited,” originated from the erroneous supposition that
   the sporocarps were borne on the roots.


              Sub-Class 1. =Filices= (=the True Ferns=).

Of the eight orders (with about 4,000 species) comprised in this
sub-class, the Polypodiaceæ is the largest (having about 2,800 species)
and the most familiar; for this reason it will be taken as typical.

=The sexual generation.= When the spore germinates, the external
covering (exospore) is ruptured, as in the Mosses. The internal
cell-wall (endospore) grows out as a filament, which soon divides and
gives rise to the prothallium, a flat, cellular expansion resembling
the thallus of a Liverwort. In its fully developed state the
prothallium is generally heart-shaped, dark green, and provided with
root-hairs, and it attains a diameter of about one centimetre (Fig.
205). It is formed of one layer of cells, except along the central
line near the anterior depression, where it becomes several layers
of cells in thickness, forming the “cushion,” on the lower side of
which the archegonia are developed. The antheridia are first formed;
they are thus found on the oldest parts of the prothallium, on its
edge, or among the root-hairs. The archegonia are developed later,
and are therefore found near the apex. Several tropical Ferns have
prothallia[18] deviating from this typical form; _Trichomanes_
(Order _Hymenophyllaceæ_) has filamentous, branched prothallia,
which resemble the protonema of a Moss. Others, again, have
strap-shaped prothallia, which resemble the thallus of certain
Liverworts.

  [Illustration: FIG. 205.--Prothallium (_p p_) of Maiden hair
  (_Adiantum capillus veneris_) with a young plant attached: _b_
  first leaf; _w′_ primary root; _w″_ adventitious roots; _h h_
  root-hairs of the prothallium (× abt. 30).]

  [Illustration: FIG. 206.--Antheridia of Maiden-hair (× 550).
  _A_ Unripe; _B_ ripe, but unopened; _C_ open and ejecting the
  spermatozoids (_s_). Those which have been last ejected are still
  lying enclosed in their mother-cells, the others are coiled up
  and drag with them the cytoplasmic remains (_b_); _f_ cells of
  the prothallium.]

The ARCHEGONIA have been already mentioned (p. 199, Fig. 201). The
ANTHERIDIA are hemispherical or slightly conical bodies (Fig. 206).
They consist, as in the Mosses, of a wall formed by one layer of
cells, which encloses a number of spermatozoid-mother-cells (_A_
and _B_). The antheridia when ripe absorb water, and are ruptured,
and the spirally-coiled spermatozoids liberated (Fig. 206 _S_).
The spermatozoids have been observed to pass down the neck of the
archegonium, and to fuse with the oosphere.

=The asexual generation.= The first leaf, the “cotyledon,” of the
embryo developed from the oospore (Figs. 202, 205) is always small,
and has a very simple shape. The leaves which occur later become more
perfect, stage by stage, until the permanent form of leaf has been
attained.--The STEM is most frequently a subterranean or a semi-aerial
rhizome; it is only in the tropical, palm-like Tree-Ferns, that the
stem raises itself high in the air and resembles that of a tree,
with leaf-scars or with the remains of leaves attached (Figs. 207,
203); in certain species the stem is encased in a thick mat of aerial
roots (_Dicksonia antarctica_). When the rhizome is horizontal the
internodes are frequently elongated, and the leaves are arranged in two
rows, as in _Polypodium vulgare_ and in the Bracken-Fern (_Pteridium
aquilinum_), etc.; it is also generally _dorsiventral_, having a dorsal
side on which the leaves are situated, and a ventral side, different
from the former, on which the roots are borne. When the stem ascends
in an oblique direction, or is nearly vertical, its internodes are
extremely short, and the leaves are arranged in a spiral line with a
complicated phyllotaxis, _e.g._ in _Athyrium filix-fœmina_, _Aspidium
filix-mas_, etc. The BRANCHING upon the whole is extremely slight, and
is generally confined to the petiole (_e.g. Aspid. filix-mas_), or
to the stem near the insertion of the leaves. Several species normally
form buds on different parts of the lamina. The buds which are formed
on the stem are not confined to the leaf-axil as in the higher plants.
The Tree-Ferns, generally, do not branch at all.

The VASCULAR BUNDLES are _concentric_, with the wood surrounded by
the soft bast. In transverse section they are seen as circles or
irregularly-shaped figures (Fig. 203), the name of “King Charles and
the Oak” (Bracken-Fern) having originated from the appearance which the
bundles present in oblique section. In _Osmunda_ they are collateral
and resemble those of the Flowering-plants. Round each individual
bundle is often a sheath of thick-walled, hard, brown, sclerenchymatous
cells, which act as a mechanical tissue; similar strands are also found
in other parts of the stem.

  [Illustration: FIG. 207.--Various Ferns (1, 2, 3, 4).]

The LEAVES in nearly all species are only foliage-leaves, borne in a
spiral. They have an apical growth which continues for a long time,
and some require several years for their complete development. In the
buds they are rolled up (_circinate_); not only the midrib, but also
all the lateral veins, and even the terminal portions of a leaf are
sometimes rolled up together, the tissues of the leaf being already
fully developed and only waiting to expand. The leaves are often
excessively divided and compound, with pinnate branches, and have
an epidermis with stomata and a well-developed system of venation.
Stipules are only found in _Marattiaceæ_ and _Ophioglossaceæ_.

Very often peculiar hairs or scales (_paleæ_, _ramenta_), dry, brown,
flat and broad, are found on stem and leaf.

The SPORANGIA are small, round capsules, which, in a very large number
of Ferns, are formed on the back, but more rarely on the edge of the
ordinary foliage-leaves. It is very seldom that there is any difference
in form between the barren foliage-leaves and the fertile leaves, as is
found for example in _Blechnum spicant_ or _Struthiopteris_; or that
the fertile part of the leaf is differently constructed from the barren
portion of the same leaf, as in the Royal-Fern (_Osmunda_). In such
instances the mesophyll of the fertile parts is poorly developed.

The sporangia in the _Polypodiaceæ_ are lens-shaped, with long stalk
(Fig. 211 _D_): their wall consists of one cell-layer on which a single
row of cells, passing vertically over the top (that is along the edge
of the sporangium), is developed into the “ring” (annulus). The cells
of the annulus are very much thickened on the inner and side walls,
and are yellowish-brown. The thickened cells, however, do not entirely
encircle the sporangium, and on one side, near the stalk, they pass
over into large, flat, thin-walled cells. These form a weak point in
the wall, and it is here that the sporangium is opened diagonally by
the elongation of the annulus. The sporangium of the Polypodiaceæ
opens as it dries. The cells of the annulus are very hygroscopic, and
in straightening, the annulus bends back with a jerk, thus ejecting
the spores to considerable distances. The cells of the annulus absorb
water with great readiness. [The sporangium arises as a single
epidermal cell, from which a basal stalk-cell is cut off. Three oblique
cell-walls, intersecting near the base, are next formed in the upper
cell, and a fourth between these and parallel to the free surface; an
inner tetrahedral cell enclosed by four others is thus formed, the
outer cells become the wall of the sporangium, while the inner cell,
by a series of walls, parallel to its sides, cuts off a layer of
cells which eventually form the tapetum, the remaining central cell
constituting the archesporium.]

The SPORES are either oblong and bilateral, or they are tetrahedric
with curved sides, depending upon the way in which the tetrad division
has taken place.

The sporangia are almost always situated on the nerves and gathered
into groups, _sori_, which differ in form in the various genera. The
sori, in many genera, may be covered by a scale-like structure, the
_indusium_ (Figs. 211 _B_, 212).

In the majority of cases, each sorus is situated on a small papilla
(_placenta_, or _receptacle_), which is supplied by a small vascular
bundle. Between the sporangia, hairs (_paraphyses_) are often situated,
which spring either from the placenta or from the stalks of the
sporangia.

=Systematic Division.= The Ferns may be divided into two groups,
characterized by the structure and development of the sporangia.
The sporangia in the EUSPORANGIATÆ take their origin from a group
of epidermal cells, and their walls are formed by several layers of
cells. The archesporium is the (not tetrahedric) hypodermal terminal
cell of the axial row of cells which give rise to the sporangium.
In the LEPTOSPORANGIATÆ the sporangia are developed from single
epidermal cells, and their walls are uni-layered. The archesporium is a
central, often tetrahedric cell, from which sixteen spore-mother-cells
are developed.[19] It is difficult to say which form is the oldest
(according to Prantl, those which have the sori on the nerve-endings);
however, the Eusporangiatæ would seem to have made their appearance
long before the others, and also well defined Marattiaceæ and
Ophioglossaceæ occur in the Kulm and Coal period, before the true
Polypodiaceæ.

About 4,000 species of Ferns are now existing, and they are found
especially in tropical and sub-tropical forests.


                      Family 1. =Eusporangiatæ.=

Order 1. =Ophioglossaceæ.= The prothallium differs from that of all
other Ferns in being _subterranean_, _free from chlorophyll_, _pale_
and _tuberous_. The stem is extremely short, with short internodes,
most frequently unbranched, vertical, and entirely buried in the ground
(Fig. 208 _st_). In several species (among which are the native ones)
one leaf is produced every year, which has taken three to four years
for its development. In _Botrychium_ a closed, sheath-like basal part
of each leaf covers the subsequent leaves during their development. In
_Ophioglossum_ and others each leaf has at its base an intrapetiolar,
cap-like sheath, which protects the succeeding leaf. The leaves are
of two kinds: (_a_) foliage, which in _Ophioglossum vulgatum_ are
lanceolate and entire, but in _Botrychium_ however, are pinnate (_b_
in Fig. 208 _A_, _B_); and (_b_) fertile, which are found facing the
upper side of the foliage-leaves. These latter in _Ophioglossum_ are
undivided and spike-like (Fig. 209 _A_), but pinnate in _Botrychium_
(Fig. 208 _B_). Each foliage and fertile leaf are branches from the
same petiole. The large sporangia are placed laterally, and open by
two valves. No annulus is formed (Fig. 209).--_Ophioglossum_ reproduces
vegetatively by adventitious buds on the roots.

  [Illustration: FIG. 208.--_A Ophioglossum vulgatum_
  (Adder’s-tongue); _B Botrychium lunaria_ (Moonwort), both
  natural size; _r-r_ roots; _bs_ leaf-stalk; _st_ stem; _b_
  foliage-leaf; _f_ fertile leaf.]

  [Illustration: FIG. 209.--Fertile leaf of _Ophioglossum_.]

Three genera with about twelve species.

Order 2. =Marattiaceæ= are tropical Ferns, whose gigantic leaves
resemble those of the Polypodiaceæ, but have stipules in addition.
The sporangia are grouped in sori, situated on the lower side of the
leaves, the sporangia in each sorus being arranged either in two rows
or in a ring. In _Angiopteris_ they are isolated (Fig. 210 _A_),
but in the other species (_Kaulfussia_, _Danæa_, _Marattia_), they
are united, and form “synangia” divided into a number of chambers
corresponding to the sporangia. These open by clefts or pores.
_Marattia_ presents the highest development, as its sporangia are
completely united in a capsule-like synangium, which is closed until
maturity, and then opens by two valves. In each valve there is a row
of three to eleven sporangia, each opening by a slit towards the
inside (Fig. 210 _B_, _C_). An indusium encloses the sorus, except in
_Kaulfussia_; it is formed of flat and lobed hairs, which resemble
the hairs of the other portions of the leaves. In _Angiopteris_ and
_Marattia_ the indusium is very rudimentary; in _Danæa_ it forms a kind
of cupule.

   The numerous fossil Marattiaceæ (15 genera, with 98 species)
   present similar differences to those now living, but more
   various forms are found, for example, with solitary free
   sporangia. Those now living are the last small remnant (4 genera
   with only 23 species) of a once dominant family, which existed
   from very early times, and whose culminating point was reached
   in the Kulm and Coal periods.

   The Ophioglossaceæ appear also in the Kulm and Coal periods,
   and were about as numerous as at the present time (presumably 2
   genera, with 19 species). Leptosporangiate Ferns appear however
   to have occurred first of all in the Trias-formation.

  [Illustration: FIG. 210.--Sporangia of the Marattiaceæ: _A_
  _Angiopteris_; _B_ and _C Marattia_; _C_ is a half sorus with
  nine sporangia, each of which has opened by a longitudinal cleft.]


                     Family 2. =Leptosporangiatæ.=

Order 1. =Polypodiaceæ.= Sporangia on the lower side of the leaves,
_stalked_ and provided with a _vertical_, incomplete annulus; dehiscing
by a transverse cleft (Fig. 211 _D_).--The genera are distinguished by
the form of the indusium and the position of the sori, etc.

1. The sporangia cover the entire lower surface of the leaf (Tropical
America and Asia). _Acrostichum_, _Platycerium._

2. Sori without indusia, circular or oval. _Polypodium_ (Fig. 211 _A_).
The leaves are most frequently situated in two rows on the dorsal
side of the creeping rhizome, and fall off leaving a smooth scar
behind.--_P. vulgare_, common in woods, on stones. (_Phegopteris_ also
has no indusium; see page 214).

3. The sporangia are situated in continuous lines just inside the
margin of the leaf.--_Pteris_[20]: the sporangia form a continuous
line along the entire margin of the leaf (Fig. 211 _C_), which bends
over and covers the sporangia, forming a “false-indusium.” _Pteridium_
has linear sori situated on a marginal vascular bundle, covered by two
linear basal indusia, of which the outer is bent over like the edge of
a leaf.--_P. aquilinum_ (Bracken) has a wide-spreading rhizome with
large alternate leaves, placed on opposite sides, at some distance
apart. Only one leaf is developed from each branch every year.

  [Illustration: FIG. 211.--Portions of leaves with sori. _A_
  _Polypodium_. _B Aspidium_. _C Pteridium_. _D_ A sporangium
  of one of the Polypodiaceæ: _r_ the annulus; _s_ spores.]

   _Adiantum_ (Maiden-hair): sori on the underside of small
   portions of the edge of the leaf, which are bent over (false
   indusium). _Cryptogramme_ (_Allosorus_), _Cheilanthes_.

4. The sori are oval or linear, situated on one side of the vascular
bundle.--_Asplenium_ (Fig. 212 _A_): sori linear; indusium with one of
its edges attached at the external side. _A. ruta muraria_ (Wall-Rue);
_A. septentrionale_; _A. trichomanes_.--_Athyrium_: sori linear or
curved; _A. filix-fœmina_ (Lady-Fern).--_Scolopendrium_ (Fig. 212 _B_):
sori as in _Asplenium_, but situated in pairs across the lanceolate,
entire leaves. Each sorus is covered on the external side by an
indusium, whose free edges are parallel and approach each other. _S.
vulgare_ (Hart’s-tongue).--~_Blechnum_ (_B. spicant_, Hard Fern; the
fertile leaves differ from the barren, the pinnæ being narrower, while
the underside is almost entirely covered with sori, and hence they
are of a much darker brownish hue than the barren ones).--_Ceterach_:
indusium rudimentary or absent.~

5. Sori circular and covered by a shield-like, or reniform
indusium.--_Aspidium_ (Fig. 211 _B_); the leaves wither away and
leave no scar upon the root-stock. _A. filix-mas_ (Male-Fern); _A.
spinulosum_.--_Phegopteris_ has no indusium, the withered bases of the
leaf-stalks are persistent; _P. dryopteris_ and _P. polypodioides_.

6. The indusium is situated below the sori, and has the shape of a
one-sided scale (_Cystopteris_, _Struthiopteris_), or of a cup or
cupule, which in _Woodsia_ is sometimes fimbriate (Fig. 212 _C_, _D_).

  [Illustration: FIG. 212.--_A Asplenium_.
  _B Scolopendrium_. _C Woodsia_; _D_
  single sorus of the same. _E Cyathea_: the sporangia
  have fallen off in the upper sori. (All magnified.)]

7. The sori are situated on the margin of the leaf, and at the end of a
vascular bundle. Indusium, semi-cupular. _Davallia._ Principally
tropical species. 1 in S. Europe.

This order is the greatest, comprising about 2,800 species, the
majority being perennial plants. A few are large, and known as
Tree-Ferns.

   As plants in conservatories and rooms the following are
   cultivated: species of _Gymnogramme_ (tropical America),
   _Lomaria_, _Nephrolepis_, _Pteris_ (_P. serrulata_, _cretica_).

   Officinal. _Aspidium filix-mas_, rhizome and the withered
   petioles.--Species of _Alsophila_ and _Cibotium_ give Penghawar
   Djambi. The rhizome of _Pteridium aquilinum_, var. _esculentum_,
   contains so much starch that it is used as food.

   The other orders of true Ferns deviate from the Polypodiaceæ,
   especially in the formation of the annulus, the bursting of the
   sporangium and its mode of attachment and development, and in
   the differences in the formation of the prothallium, etc. The
   principal are:--

Order 2. =Hymenophyllaceæ.= To this order belong the lowest and most
Moss-like Ferns; the leaves, with the exception of the veins, are
most frequently formed of _only one layer of cells_, and consequently
stomata are wanting; the formation of the prothallium also somewhat
resembles the Mosses. Sori marginal, on the _extremities of the
vascular bundles_, and surrounded by a _cupular indusium_. The
sporangia are sessile, with equatorial annulus. _Hymenophyllum_ (_H.
tunbridgense_, European). _Trichomanes_ (_T. speciosum_, European).
Species about 200, which live especially on rocks and trees in damp and
shady tropical forests. Some have no roots.

Order 3. =Cyatheaceæ.= Annulus _complete_ and oblique. To this order
belong, principally, the tree-like Ferns with palm-like habit. The
number of species is about 200, they are all tropical and form forests
in some regions of Australia. _Cibotium_ and _Dicksonia_ have marginal
sori, with cupular, basal indusium. (The stem of _D. antarctica_ is
covered with aerial roots.) _Alsophila_ (without indusium); _Cyathea_
with cupular, inferior indusium (Fig. 212 _E_).

  [Illustration: FIG. 213.--_Gleichenia_: _A_ part of a leaf with
  sori; _B_ a single sorus.]

Order 4. =Gleicheniaceæ.= Sporangia with equatorial annulus, and
longitudinal dehiscence, most frequently groups of 3–4 in sori without
indusium (Fig. 213). _Gleichenia_: the apical growth of the leaves
continues for a long time.

Order 5. =Schizæaceæ.= Annulus apical. To this order belongs _Aneimia_,
which is so commonly cultivated in conservatories. The two lowest pinnæ
are metamorphosed, having no leaf parenchyma and being covered with
sporangia. _Schizæa. Mohria. Lygodium_, a climber, whose leaves
have unlimited growth and attain a length of several metres. About 70
species. Tropical.

Order 6. =Osmundaceæ.= The sporangia have at the apex a lateral group
of strongly thickened cells, which gradually pass over into the
ordinary cells. The sporangia open by a longitudinal cleft. Indusium
wanting. _Osmunda_ bears the sporangia upon peculiar, branched
pinnæ, without parenchyma (the uppermost in the leaf). _O. regalis_
(Royal-Fern): European.

  [Illustration: FIG. 214.--_Salvinia natans_: _A_ microsporangium
  with germinating microspores and protruding prothallia (_s_);
  _B_ a prothallium with the bicellular antheridium (_s_) growing
  out of the microsporangium; _C_ the two cells of the antheridium
  have opened by transverse clefts; beneath is seen the microspores
  enclosed by the hardened mucilage; _D_ spermatozoids still
  enclosed in the mother-cells.]

  [Illustration: FIG. 215.--_Salvinia natans. A_, _B_ Female
  prothallia, _f-f_, protruding from the macrospore which is still
  enclosed in the macrosporangium; _œ_ archegonia. _C_ An embryo (×
  16) still in connection with the spore (_s_): _a_ the scutiform
  leaf; _b-e_ the subsequent foliage-leaves, of which _b_ and _c_
  stand singly, _d-e-v_ in a whorl; _v_ the submerged-leaf; _f-f_
  wing-like lobes of the prothallium: _m_ the foot.]


  Sub-Class 2. =Hydropterideæ= (formerly Rhizocarpeæ), =Water Ferns=.

The following further characteristics must be added to those given on
page 205:--

=Sexual generation.= The MICROSPORES produce an extremely rudimentary
prothallium, formed of only a single cell, and having also a very much
reduced bicellular antheridium with a small number of spermatozoid
mother-cells in each cell (in _Salvinia_ 4, in _Marsilia_ and
_Pilularia_ 16). In _Salvinia_ the microspores remain embedded in a
hard mucilaginous mass (at first frothy) which fills up the cavity of
the sporangium. The prothallium must therefore grow out through this
slime and also through the wall of the sporangium (Fig. 214), and it
thus terminates in a relatively long cell.

In _Marsilia_ the microspores are set free from the microsporangium,
and the prothallia, with the antheridia, remain in them until the
spermatozoids are liberated. The latter are spirally-twisted threads.

The MACROSPORES, on germination, give rise to a very reduced
prothallium, which in _Salvinia_ bears 3 archegonia; but, if these
are not fertilised, the prothallium may continue to grow and become a
fairly large, green body with several archegonia (Fig. 215 _A_, _B_).
In _Marsilia_ the prothallium is still more reduced, it is enclosed
in the macrospore, and only bears one archegonium. The archegonia are
similar in structure to those of the Ferns, but are smaller, and sunk
more deeply in the tissue of the prothallium.

  [Illustration: FIG. 216.--_Salvinia natans. A_ An archegonium,
  unripe, seen in longitudinal section: _h_ the neck-cells; _k_ the
  neck-canal-cells; _c_ the central cell. _B_ An open archegonium
  of which the neck-cells have separated off. _C_ An open, old
  archegonium seen from the top.]

=The asexual generation= is developed from the fertilised egg-cell.
It is a dorsiventral, horizontal shoot. In _Salvinia_ it bears at
first a shield-like leaf, the scutiform leaf (Fig. 215 _C_, _a_),
which is succeeded by the ordinary foliage-leaves. The young plants of
_Marsilia_, likewise, have less perfect leaves in the very early stage.

The formation of the sporangium is the same as in the Leptosporangiate
Ferns. (The 16 spore-mother-cells originate from one central,
tetrahedric archesporium.)

The Hydropterideæ are divided into 2 orders, the chief differences
between them being found in the asexual generation.

  [Illustration: FIG. 217.--_Salvinia natans_ (natural size): _A_
  seen from above, floating on the water; _B_ a portion seen from
  the side in its natural position in the water.]

  [Illustration: FIG. 218.--Sori of _Salvinia_ in longitudinal
  section: _h_ microsporangia; _m_ macrosporangia. (× 10.)]

Order 1. =Salviniaceæ.= This order more nearly approaches the true
Ferns, especially so on account of the form of the indusium. Only one
species is found in Europe, _Salvinia natans_ (Fig. 217). This is a
small, floating, annual, aquatic plant, entirely _destitute of roots_.
The dorsiventral, horizontal stem bears two kinds of leaves, which
are arranged in whorls of three. Two of these which turn upwards are
oval, entire, “_aerial foliage-leaves_” (Fig. 217 B, _b^2_-_b^3_);
the third, the “_water-leaf_” (_b^1_) is submerged and divided into a
number of hair-like segments, similar to the submerged leaves in many
aquatic plants, for instance, Water-buttercup (see also Fig. 215 _C_).
The whorls of leaves alternate with each other; there are thus 4 rows
of dorsally-placed aerial leaves, and two rows of ventrally-placed
submerged leaves. The sporangia are situated in sori, each sorus
being borne on a small column (receptacle or placenta) and enveloped
by a _cupular_, but _entirely closed indusium_ (Fig. 218). _The sori
are situated on the submerged leaves_ (Fig. 217 _B_, _s-s_) _and
are unisexual_, _i.e._ each sorus contains microsporangia only, or
macrosporangia.

   _Azolla_ belongs to this order. It is a very small, floating,
   tropical water-plant (America and East India), with horizontal,
   root-bearing stem. The stem branches profusely by lateral buds,
   and bears the two rows of leaves on its dorsal side, the roots
   on the ventral side. Each leaf is bifid, and  divided into an
   upper dorsal, and a lower ventral portion. The upper segments
   float on the surface of the water and are arranged like tiles
   on a roof, each one overlapping its neighbour. In each floating
   segment a large cavity is found, in which _Anabæna_ is always
   present. The lower segments are submerged.

Order 2. =Marsiliaceæ.= The characteristic feature of this order,
and one not possessed by other Fern-like plants, is that the sori
(2–many) are enveloped _in leaf-segments_ which _close round them_
and form a “sporocarp,” just in the same manner as the carpels, in
the Angiospermous Flowering-plants, close round the ovules and form
ovaries. The sori contain both micro-and macrosporangia. When the
spores are ripe, the sporocarp opens in order to disperse the spores
(Fig. 220).

  [Illustration: FIG. 219.--_Marsilia salvatrix_ (natural size):
  _K_ terminal bud; _b_ leaves; _f_ sporocarps; _x_ point of
  branching of petiole.]

The two genera (with 57 species, Temperate, Tropics) are land-and
marsh-plants, whose dorsiventral, creeping stem bears roots on the
under surface, and the leaves in two rows on the upper side (Figs.
219, 221). The leaves of _Marsilia_ are compound, and divided into
four small leaflets springing from the apex of the petiole (Fig.
219), and resemble the leaves of _Oxalis_. In the bud the leaves are
circinate (Fig. 219 _b_), and at night they exhibit the well-known
sleep-movements. The sporocarps are borne on the petioles of the
fertile leaves, near their bases (Fig. 219 _f_); they are oblong and
resemble small beans, the outer cells being hard and sclerenchymatous,
while the inner ones are divided into a number of loculi arranged in
two rows. On germination, water is absorbed, the two sides separate
slightly, as valves (Fig. 220 _A_), and a long vermiform mass of
gelatinous, parenchymatous cells (Fig. 220), swollen by the water,
emerges, bearing a large number of sori arranged pinnately. Each
sorus (_sr_) is covered by a thin indusium. (The thin covering may be
considered an indusium physiologically, though not morphologically).

  [Illustration: FIG. 220.--_Marsilia salvatrix_: _A_ the
  sporocarp commencing to germinate; _B_ a more advanced stage of
  germination.]

  [Illustration: FIG. 221.--_Pilularia globulifera_ (natural size):
  _s_ sporocarps; _b_ leaves; _k_ the growing point; _r_ roots.]

   _Marsilia quadrifolia_, in Europe. Many species are found in
   Australia. The nutritious sporocarps of _M. salvatrix_ were
   the means of saving the Burke expedition in the interior of
   Australia, and hence this species has earned its specific name.

_Pilularia_ has linear leaves, without lamina. The sporocarps are
spheroid (Fig. 221), brown and hard, and situated near the base of the
leaves. They are 2–4 chambered and open by a corresponding number of
valves.


                  Class 2. =Equisetinæ (Horsetails.)=

The characteristics of this class have been described on page 204.

It is divided into two sub-classes:--

1. THE ISOSPOROUS EQUISETINÆ. To this sub-class belong, with
certainty, only the EQUISETACEÆ now existent, which are
represented by only one genus, _Equisetum_.

2. THE HETEROSPOROUS EQUISETINÆ. Forms which are now extinct.

  [Illustration: FIG. 222.--_Equisetum arvense._ The prothallium
  highly magnified. _A_ Male; _s, s_ antheridia. _B_ Portion of a
  female, cut through vertically; _œ œ_ archegonia, the central one
  is fertilised; _h h_ root-hairs.]

  [Illustration: FIG. 223.--_Equisetum maximum._ Spermatozoids: _a_
  shows them still enveloped by the mother-cell.]


                 Sub-Class 1. =Isosporous Equisetinæ.=

Order. =Equisetaceæ (Horsetails).=

=The sexual generation.= The prothallium is green and leaf-like, as in
the majority of Ferns, but irregularly branched and curled. It is often
unisexual. The male prothallia bear antheridia only, and are smaller
and less branched (Fig. 222 _A_) than the female; the latter may attain
a diameter of ½ an inch, and bear archegonia only (Fig. 222 _B_). The
antheridia and the archegonia resemble those of the Ferns, but the
spermatozoids (Fig. 223) are larger and less twisted. On the last curve
is situated a more or less elongated appendage of cytoplasm (Fig. 223
_c_).

=The asexual generation.= The embryo is similar to that of the Ferns.
The fully developed _Equisetum_ is a perennial herb, with widely
creeping (in some species tuberous) rhizome, from which extend erect,
aerial, most frequently annual shoots.

  [Illustration: FIG. 224.--_Equisetum arvense_: _a_ fertile branch
  with cone; _b_ vegetative shoot; _c_ cone; _d_ sporophylls.]

The vegetative aerial STEMS are divided into a number of
internodes by the whorls of leaves (Fig. 224). The internodes are
hollow, the cavities being separated from each other by the transverse
partitions of the solid nodes. The lower portion of the internode,
which is encased by the leaves, has much thinner and softer cell-walls,
so that the stem is easily separated into segments just above the
nodes. Each internode has a large number of ridges and furrows,
and bears at its apex a whorl of leaves whose number and position
correspond to the ridges of the internode. As in the case of other
verticillate plants, the whorls are placed alternately, one above
the other; the same arrangement is also found in the ridges on two
successive internodes. In addition to the large air-cavity in the
centre of each internode (the central cavity), a whorl of tubular
air-passages is found in the cortex of the stems, opposite the furrows
(vallecular canals). There is also a similar air-passage (carinal
canals) in each of the vascular bundles, which are placed in a ring,
one opposite each ridge, and therefore alternating with the vallecular
canals. The vascular bundles are _collateral_ as in the majority
of Flowering-plants, but poorly developed. The xylem of each bundle
consists of two groups of annular or spiral vessels, close to the outer
border of the carinal canal, and two groups of scalariform tracheides,
each placed on a radius passing through a group of spiral vessels.
The phloëm is placed between these four groups, each of which has
only a few vessels. The stiffness of the stems is mainly due to the
large amount of silica in the cell-walls of the epidermis, and to the
sclerenchymatous cells of the ridges.

All LEAVES are situated in _whorls_. The VEGETATIVE are simple,
undivided, 1-nerved, and are united into toothed sheaths (Fig. 224 _a_,
_b_). The branching of the stems in some species (_E. arvense_) is very
abundant. The branches break through the base of the leaf-sheaths (Fig.
224 _b_), and generally _alternate with the teeth_ (leaves).

The FERTILE LEAVES (_sporophylls_) are different from the barren ones.
They are _free, shield-like_, each one having a short stalk bearing
usually an hexagonal plate (Fig. 224 _d_), and closely compressed into
an ear or cone (Fig. 224 _a_, _c_). The _Equisetums_ thus present an
advance in development distinctly beyond that of the Ferns, which is
further emphasized by the circumstance that a transition from the
sheath-leaves to the fertile-leaves is found in the involucre or
annulus, a “collar” of specially modified leaves situated at the base
of the cone (Fig. 224 _a_ and _c_). The cone may be considered as a
very rudimentary flower, and the annulus may be regarded as a very
early stage in the formation of a flower (perianth). See page 235.

The SPORANGIA are situated on the underside of the sporophylls, one
at each angle; they are sac-like, and open inwardly by a longitudinal
cleft (Fig. 224 _d_). An annulus is wanting; but in the wall of the
sporangium, as in the pollen-sacs of the Flowering-plants, a layer of
cells, with annular or spiral thickenings, is developed, which assists
in the dehiscence of the sporangium.

The SPORES are green; the walls composed of four distinct layers,
of which the outer is gradually separated, except at one point, and
becomes split into four long bands (_elaters_) (Fig. 225). The elaters
are extremely hygroscopic, coiling round the spore when moistened, and
expanding as soon as dry, presenting a most lively object under the
microscope when breathed upon and allowed to dry. The second layer,
when germination commences, becomes detached from the inner wall, which
is formed of the exospore and endospore.

The order has become much reduced, and at the present time includes
only one genus, _Equisetum_, with about twenty-five species, which are
distributed over the entire globe, particularly in damp situations. In
SOME SPECIES the barren shoots are green and very much branched, but
the fertile ones are unbranched, pale brown, and possess no chlorophyll
(_E. arvense_, Field-Horsetail, Fig. 224, and _E. maximum_). IN
OTHERS the fertile and barren shoots are alike green, and either both
unbranched (_E. hiemale_), or branched (_E. palustre_, _E. limosum_,
etc). The fertile shoots of _E. silvaticum_, up to maturity, resemble
those without chylorophyll of _E. arvense_, but after that period they
produce green branches, and thus resemble the barren ones.

  [Illustration: FIG. 225.--Spores of _Equisetum_: _A_ damp, with
  elaters (_e_) coiled round the spore; _B_ dry, with elaters
  expanded.]

   EXTINCT ISOSPOROUS EQUISETINÆ. In addition to several true
   species of fossilized _Equisetums_, the order of the CALAMITES,
   which no doubt is closely allied to the Equisetinæ, is also
   found in the fossil state. These were gigantic forms, attaining
   about twenty times the size of those of the present day, and
   stems of nearly 10–12 metres in height are known. They reached
   the culminating point of their development in the Carboniferous
   period, and died out towards the close of the Palæozoic. The
   stems had hollow internodes and alternating grooves, similar
   to their relatives of the present day. The leaves must either
   have been absent or very perishable, since they have not been
   identified with certainty. If the determinations of certain
   remains of cones which of late have been discovered are correct,
   they were heterosporous and had two kinds of sporangia as in
   the following sub-class. A cambium formation and an increase in
   thickness has been found in the stems.

   Their USES are very limited. A few species, such as _E. hiemale_
   are used for polishing on account of the hard siliceous
   cell-walls of the epidermis, found in all species of _Equisetum_.


               Sub-Class 2. =Heterosporous Equisetinæ.=

   The two orders which come under this head are united by the
   characteristics, that the verticillate leaves are not united
   into sheaths (Fig. 226), and that between each whorl of fertile
   leaves there is also a whorl of barren ones. The fertile whorls
   in ANNULARIÆ are situated about midway between the barren ones
   (Fig. 227), but in ASTEROPHYLLITEÆ they occur immediately above
   a barren whorl (Fig. 228) and contain only half as many members
   as the latter. The lower whorls bear macrosporangia with one
   macrospore, the upper, microsporangia with many microspores.

  [Illustration: FIG. 226.--A. fragment of _Annularia_.]

  [Illustration: FIG. 227.--Fragment of _Annularia longifolia_,
  with sporangia; the leaves have partly fallen off: a barren
  whorls; _s_ fertile whorls.]

  [Illustration: FIG. 228.--Fragment of cone of _Asterophyllites_
  (_Volkmannia elongata_): _a_ and _s_ as in Fig. 227.]

   The ANNULARIÆ were distichous (Fig. 226), and presumably
   floating plants. The ASTEROPHYLLITEÆ had verticellate branches.
   These also died out after the Carboniferous period, at the close
   of the Palæozoic.


                Class 3. =Lycopodinæ= (=Club-Mosses=).

The characteristics of this class have been given on page 205. It
consists of two sub-classes, one embracing isosporous, the other
heterosporous forms.


          Sub-Class 1. =Lycopodieæ= (ISOSPOROUS Lycopodinæ).

One kind of spore. Prothallium large, partly green. Leaves without
ligule.

  [Illustration: FIG. 229.--_Lycopodium annotinum_: _A_ embryo
  (nat. size), with prothallium (_pr_), one embryo is broken off;
  _B_ the prothallium (slightly magnified); _C_ section through
  the prothallium and embryo in the direction _a-b_ of _A_, and
  vertically in the plane of the paper.]

  [Illustration: FIG. 230.--_Lycopodium clavatum_: portion of a
  stem, bearing cones (_a_); _s_ a spore; _h_ sporangium in the
  axil of a leaf, _s_.]

Order 1. =Lycopodiaceæ.= The PROTHALLIUM is only known in a few species
at present, but in these it is more or less tubercular, and bears both
antheridia and archegonia.

   In _L. annotinum_ the prothallium is a relatively large mass
   of cells, without chlorophyll, and subterranean, in which
   the antheridia and archegonia are embedded (Fig. 229). In
   the widely distributed tropical species, _L. cernuum_, and
   in _L. inundatum_, it is a small tubercular body which has a
   subterranean portion, with either little or no chlorophyll;
   and an aerial green portion. The prothallia of _L. phlegmaria_
   and others live saprophytically in the crevices of the bark of
   trees; they are partly filamentous, branched, and possess no
   chlorophyll.

The =asexual generation=. PERENNIAL PLANTS. The stem branches
monopodially (often apparently dichotomously), and is thickly covered
by small, simple, triangular or scale-like leaves. The leaves are
spirally arranged in some species (Figs. 229, 230), and in others,
whose stem is compressed with unequal sides, opposite (Fig. 231). The
roots of _Lycopodium_ are dichotomously branched.

The SPORANGIA in _Lycopodium_ are situated singly at the base of the
leaves, almost in their axils; they are reniform, unilocular and open
like a mussel-shell by two valves (Fig. 230 _h_). The sporangia are
developed from a group of surface cells. The archesporium is formed
from one hypodermal cell (or perhaps a cell-row).

  [Illustration: FIG. 231.--_Lycopodium complanatum_: _a_ leaves on
  the edges of the stem; _d_ leaves on the sides.]

  [Illustration: FIG. 232.--_Lycopodium clavatum._ A tetrahedral
  spore seen from above, where the three borders join; and a tetrad
  of bilateral spores, still lying in the mother-cell.]

The fertile leaves are collected upon definite regions of the stem.
They are either similar to the barren ones, and then the fertile
portions of the stem pass gradually, without any break, into the barren
portion (_L. selago_); or they differ from the barren leaves, and are
then collected into special apical cones (Fig. 230 _a_). The SPORES are
tetrahedral or bilateral (Fig. 232).

About 100 species, chiefly tropical.

   Five species of _Lycopodium_ are found in Great Britain. _L.
   clavatum_ and _L. selago_ are common in mountainous districts.
   _L. annotinum_ is common in the Highlands of Scotland. The other
   genus of the order is _Phylloglossum_, with one species, _P.
   drummondi_ (Australia, Tasmania, and New Zealand), a small plant
   only a few centimetres high, with two tubers, and about eleven
   linear leaves at the base of the stem which is terminated by a
   cone of sporophylls.--FOSSIL Lycopodiaceæ in the Carboniferous
   period.

   OFFICINAL: “Lycopodium,” the spores of _L. clavatum_.

   Family 2. =Psilotaceæ=. The sporangia are placed on the apex of
   short, two-leaved stems, as 2–3, seldom four, small capsules.
   Small herbs, with angular stems; leaves small, simple, and one
   nerved. Only four species.--_Psilotum_ (Madagascar, Moluccas,
   Sandwich Islands, etc.) is destitute of roots, their place being
   supplied by special underground stems which bear a few modified
   leaves, very much reduced, especially when buried deeply in the
   soil. Three species.--_Tmesipteris_ (Australia), one species.


        Sub-Class 2. =Selaginelleæ= (HETEROSPOROUS Lycopodinæ).

Micro-and macrospores. The prothallia are very much reduced, especially
the male; the female does not leave the spore. The leaves are ligulate.

  [Illustration: FIG. 233.--Germination of the microspores of
  _Selaginella_: _A_ the spore rendered transparent, seen from
  above. In the interior is seen the prothallium (_f_), and the
  first divisions of the antheridium (_a_, _b_, _c_, _d_); in _B_
  the spore-wall is removed and all the spermatozoid-mother-cells
  formed; in _C_, the microspore has opened and the spermatozoids
  and the mother-cells are escaping together.]

=The sexual generation.= In the ~MICROSPORES~ are formed: (1) a very
small “vegetative” cell, representing the vegetative part of the
prothallium (_f_ in Fig. 233 _A, B_), and (2) a cell many times larger
and which divides into a number (4–8) of primordial cells, each of
which divides into four spermatozoid-mother-cells, though all of these
may not develope spermatozoids. On germination, when the spore-wall is
ruptured, the spermatozoids and spermatozoid-mother-cells are ejected
into the water.

The ~SPERMATOZOIDS~ in _Selaginella_ are elongated and club-shaped,
with two cilia (Fig. 234); but in _Isoëtes lacustris_ they are
spirally-twisted threads which differ from all other spermatozoids by
having a bunch of cilia _at each end_; the other species of _Isoëtes_
have cilia only at the anterior end.

The MACROSPORES. Shortly after the macrospores have been set free,
or in _Selaginella_, while still enclosed in the sporangium of the
mother-plant, they germinate and soon become filled with the cellular
tissue of the prothallium, and even in _Selaginella_ the archegonium
begins to be formed before the rupture of the spore-cell-wall has
commenced (Fig. 235 _A_).

  [Illustration: FIG. 234.--Spermatozoids of _Selaginella_: _b_
  with a remnant of cytoplasm.]

  [Illustration: FIG. 235.--Macrospore of _Selaginella_: _A_
  longitudinal section, before the rupture of the wall, six
  weeks after being sown. The endosperm (_e_) has not yet filled
  the entire chamber. Cell-formation is still proceeding in the
  lower part of the spore. The endosperm and prothallium (_f f_)
  are separated by a distinct line (diaphragm). _B_ Germinating
  macrospore seen from outside: _s_ wall of the spore; _æ_
  archegonia.]

  [Illustration: FIG. 236.--Archegonia of _Selaginella_: _A_
  unripe, in longitudinal section; _c_ the central cell; _k_
  neck-canal-cell, which is wedged in between the two-storied
  neck-cells; _B_ ripe; _u_ ventral canal-cell; _C_ seen from
  above, open. It will be noticed that the neck is formed of two
  tiers of four cells each.]

The ARCHEGONIA are constructed on the same plan as those of the other
Archegoniatæ, but are quite embedded in the prothallium (Figs. 235 _æ_,
236).

=The asexual generation= varies very much in the different orders.

  [Illustration: FIG. 237.--_Isoëtes lacustris_ (slightly
  diminished): _st_ the stem; _r_ roots; _b_ leaves.]

  [Illustration: FIG. 238.--_Isoëtes lacustris_. Longitudinal
  section through the base of the leaf with a microsporangium. The
  edge of the groove, in which the microspangium is placed, is
  continued as a thin covering which envelopes the sporangium. The
  inferior edge of the ligular groove (_L_) forms a lip (_J_); _t_
  sterile cell-rows (trabeculæ) which divide the sporangium into
  compartments; _l_ vascular bundle.]

  [Illustration: FIG. 239.--_Selaginella inæqualifolia_. Cone in
  longitudinal section; microsporangia are seen on the left side,
  macrosporangia on the right (most frequently each with four
  macrospores).]

Order 1. =Isoëtaceæ (Quill-worts).= The only known genus, _Isoëtes_
(Quill-wort), has an extremely short, tuberous, _unbranched_ stem
with very short internodes (Fig. 237). The STEM is remarkable as
being the only one among the Vascular Cryptogams which increases in
thickness (see page 202). The meristematic cells are situated round
the axial cylinder, and form, especially, parenchymatous tissue in
two or three directions, giving rise to 2–3 grooves in which the
dichotomously-branched ROOTS are produced. The LEAVES are arranged
spirally in a close rosette. They are awl-shaped and have at the
base a semi-amplexicaul sheath, with a groove (_fovea_), in which a
sporangium is situated (Fig. 238). The ligule is a foliar outgrowth
from the upper edge of the groove.--The MACROSPORANGIA (each with
a number of macrospores), are situated on the outer leaves, the
MICROSPORANGIA (Fig. 238), on the inner ones. Between each cycle of
fertile leaves there are a number of imperfect or barren ones as in
the case of the female plant of _Cycas_. The spores are liberated by
the decay of the sporangium. The two kinds of sporangia develope at
the commencement in the same way. The archesporium is, at first, a
hypodermal layer of cells which grow out in the direction perpendicular
to the surface of the leaf, and divide by a number of walls parallel
to this direction, forming a sporogenous mass of cells. Some of the
cell-rows of this sporogenous mass lose their rich protoplasmic
contents, and are arrested in their growth; thus incomplete divisional
walls of sterile cells, “_trabeculæ_” arise in the sporangium,
dividing it into a number of compartments one above the other (Fig.
238 _t_). (The trabeculæ, according to Goebel, play the same part as
the nutritive cells of the sporangium of _Riella_; the tapetal cells,
as in the Ferns, are in a great measure dissolved at a later period.)
The sporogenous cell-rows, in the microsporangia, give rise to a
large number of spore-mother-cells, but in the macrosporangia only
one spore-mother-cell, with tapetum, is developed from each fertile
archesporial cell.

The two native species, and several others, are aquatic plants, the
remaining species are land plants, or are amphibious. About 50 species.
In temperate and tropical regions.--FOSSIL species in the Tertiary
period.

Order 2. =Selaginellaceæ.= This order contains only one genus,
_Selaginella_. The STEM, in the majority of species, is dorsiventral,
long and slender, and apparently branches dichotomously, but in reality
_monopodially_, with well developed lateral shoots. The LEAVES are
small, round, or ovate, in the majority of species arranged in whorls
of two leaves each; these whorls, however, are not decussate, but are
considerably inclined towards each other, an arrangement by which four
rows of leaves are produced, each whorl having one large and one small
leaf. The two leaves in each whorl are of unequal size, the smaller one
being placed on the upper surface and the larger on the lower surface
of the stem (Fig. 240). Some species have spirally-arranged leaves,
more resembling the arrangement in the _Lycopodiums_.

The ~FERTILE LEAVES~ most frequently differ from the barren ones,
and are collected into spike-like cones (a kind of flower; Fig.
239). Micro-and macrosporangia are found in the same cone (Fig.
239). Each sporangium arises from a group of superficial cells of
the stem, directly over the leaf on which it will be situated later
on. Each sporangium has a hypodermal, unicellular archesporium, and
contains a layer of tapetal cells; these are dissolved later, when
the spores are ripe, and not before as in the Ferns. In the very
early stages of their development, the micro-and macrosporangia are
precisely similar, and the differences between them arise later on.
In the microsporangium all the spore-mother-cells divide, and each
forms four tetrahedrically-arranged microspores (Fig. 204); but in
the macrosporangium only four macrospores are formed, by the division
of a _single mother-cell_, while the remaining spore-mother-cells
are aborted. It is rarely that the macrosporangia contain 2 or 8
macrospores.

  [Illustration: FIG. 240.--_Selaginella martensii_: _s_ lower
  leaves; _r_ upper leaves.]

   For the ~GERMINATION OF THE SPORES~, see pages 228, 229. The
   prothallium arises in the macrospore (_f-f_, in Fig. 235 _A_),
   probably by division of the meniscus-shaped protoplasmic mass,
   which is marked off at the apex of the spore; primordial cells
   are thus formed which later on are surrounded by a cell-wall. In
   six to seven weeks after sowing, the spore-wall is ruptured by
   the growing prothallium, which already has developed archegonia
   (Fig. 235 _œ-œ_). The prothallium so formed does not occupy
   the entire cavity of the spore, but four to five weeks after
   sowing, the large-celled parenchyma is developed in the lower
   portion of the spore by free cell-formation; this has been
   termed by Pfeffer, “endosperm,” since it is similar to the
   endosperm of Flowering-plants. Goebel, however, has termed it
   “secondary prothallium,” as the homology with the endosperm of
   the Angiosperms is very doubtful.

The ~FERTILISED OOSPHERE~ divides into an upper (hypobasal) and a lower
(epibasal) cell; from the latter alone the embryo is developed with
its root, stem, foot, and two _cotyledons_, and the former gives rise
to an organ which appears in this instance for the first time, but
which occurs in all Flowering-plants, viz. the _suspensor_. This forces
the embryo down into the “endosperm,” which is entirely or partially
absorbed by the embryo. In the case of the Flowering-plants the embryo
is developed with its longitudinal axis in the elongation of the
suspensor, but in _Selaginella_ the embryo is situated _transversely_
to it.

_Selaginella_ (300–400 species), is essentially tropical, only one
species living in the North (_S. spinulosa_), but others grow in
Central and South Europe.

   Order 3. =Lepidodendraceæ= are extinct, tree-like Lycopods,
   which are found especially in the Lower and Middle
   Carboniferous. Vegetatively they are most nearly related to
   _Lycopodium_, but the stem attained much larger proportions
   (about eleven metres in height and one metre in thickness),
   and had a cambium by which it increased in thickness. It was
   regularly dichotomous, and closely studded with spirally-placed
   leaves, which left behind them peculiar rhombic scars. The large
   cones resemble Pine-cones, and bore sporangia much larger than
   any which are now produced (the male ones as much as 2 cm.’s in
   length). The macrosporangia were situated at the base, and the
   microsporangia at the apex.

   Order 4. =Sigillariaceæ.= These are, presumably, another
   group of extinct tree-like Lycopods (especially in the Middle
   Carboniferous). The name has been derived from the seal-like
   scars, which the fallen leaves have left behind in longitudinal
   rows on the grooved stem. The rhizomes of these plants were
   formerly termed _Stigmaria_, and placed in a separate genus.

   Order 5. =Sphenophyllaceæ= form an entirely extinct group.
   They do not definitely belong to any of the three large
   classes of Vascular Cryptogams, but it is perhaps best to
   place them in juxtaposition to these. They were herbaceous
   plants with verticillate, wedge-shaped leaves, with nerves
   branching dichotomously into equally strong branches. Micro-and
   macrosporangia were formed in the same cone; and were situated
   in the axils of the leaves, as in the Lycopods.



The Transition from the Cryptogams to the Phanerogams.


All the plants considered in the preceding chapters are included
in the term CRYPTOGAMS; all in the following chapters under the
head of PHANEROGAMS (see page 3). Hofmeister’s pioneer works
(1851, _Vergleichende Untersuchungen der höheren Kryptogamen_,
etc.) and the numerous researches published later by other
investigators, have closed the gap which was formerly thought
to exist between these plants; so that we now, in the series:
Bryophyta--Pteridophyta--Gymnospermæ--Angiospermæ see the expression of
a single line of development in accordance with a definite plan. The
forms through which this gradual development has taken place have in
course of time, however, to a great extent died out, and only single
links of the chain connecting the lowest to the highest still remain.

THE ALTERNATION OF GENERATIONS, which we found indicated in certain
Thallophytes, can be proved with the greatest clearness in all the
higher Cryptogams, from the Mosses upwards; it is also found in the
Phanerogams, but not in such a pronounced degree, because one of
the generations is so far reduced that it has almost given up its
independence. For the sake of greater clearness, we will begin with the
comparison of the sporophyte, asexual (second) generation.


           =The asexual (2nd) generation of the Cormophytes.=

The asexual generation which follows from the further development of
the fertilised oosphere, is, in the _Mosses_, only the sporogonium
(according to one theory it is perhaps homologous with a spore-bearing
leaf, situated upon a short stem, see p. 187); in _Filicinæ_,
_Equisetinæ_, and _Lycopodinæ_, on the other hand, it is a highly
developed plant differentiated into stem, leaf, and true root, and
bearing the sporangia on its leaves. The ~MODIFICATION OF THE SHOOT~
is very slight in _Filicinæ_. The first leaves of the embryo are very
simple in form (Fig. 205), but after a certain age all the leaves
which arise are essentially alike. The fertile leaves do not differ
from the barren ones, and are found associated with them, and their
formation does not limit the growth in length of the stem. It is only
in a few of the true Ferns, and in the Hydropterideæ, that the fertile
leaves differ considerably from the barren ones. A division of labour
in which certain leaves are set apart for nutrition, and others for
reproduction, is found more pronouncedly in the _Equisetinæ_ and
_Lycopodinæ_, for in these groups, with a few exceptions, the fertile
and barren leaves are very dissimilar; the former are collected in
special ear-like _cones_, which _terminate the further growth_ of
the short stems on which they are borne. In connection with the cone,
leaves are sometimes developed which form a transition from the barren
to the fertile ones (the “annulus” in Equisetaceæ), and in these cases
the first indication of a flower with perianth or floral-leaves is to
be traced. Among the Cryptogams the highest division of labour is found
in _Selaginella_ and _Isoëtes_, which have the two kinds of sporangia
borne on _different_ leaves. The division of labour (modification) is,
however, still more pronounced in the _Phanerogams_: the leaves which
bear the microsporangia (“pollen-sacs”) have quite different forms
from those which bear macrosporangia (the “nucellus” in the ovule),
the former are termed _stamens_, the latter _carpels_; in certain
instances, too, there is even a contrast between the “male plants” and
the “female plants.” Moreover, a division of labour, in a much greater
degree, takes place in the leaves which do not directly take part in
reproduction, and it is thus possible in many plants to draw a sharp
line not only between stamens and carpels, but also between four or
five distinct kinds of leaves, which differ in _form_, _structure_, and
corresponding _functions_, and which appear in regular sequence on the
shoot: namely, between “scale-leaves” and “foliage-leaves,”[21] both
of which occur in the Cryptogams, and the “floral-leaves,” including
the bracts and leaves of the “perianth,” which latter often differ from
each other in form and colour, and are then separated into _sepals_ and
_petals_. The _leaves_--stamens and carpels--_which bear the sporangia_
are termed sporophylls, and the shoot, or extremity of a shoot, whose
leaves are modified into sporophylls, is _terminated in its further
growth by their production, and is known as a flower_. The flower
which is most completely furnished has calyx, corolla, stamens, and
carpels arranged in this order. If the only sporophylls present are
stamens, then it is said to be a _male_ (_staminate_) flower, and if
only carpels, then a _female_ (_pistillate_) flower, and in both these
cases the flowers are _unisexual_, or diclinous. If stamens and carpels
are both present in the same flower, it is termed _hermaphrodite_.
Diclinous plants in which the female flowers are situated on one plant,
and the male flowers on another, are termed _diœcious_; and those
in which the same plant bears the two kinds of flowers are termed
_monœcious_. When the male, female, and hermaphrodite flowers are found
in the same species, the plant is said to be _polygamous_.

=The sporangia-bearing leaves--Sporophylls.= In the Mosses the
asexual generation is only represented by the sporogonium, and if the
theory is correct which considers the sporogonium to be an embryo
consisting of a rudimentary stem and terminal leaf, then the spores are
produced on the leaves in these plants. The sporangia in the Filicinæ
are situated in groups (sori) on the back or on the edge of the leaves.
The number of sporangia in the sorus diminishes very greatly in the
Marattiaceæ and Gleicheniaceæ (three to four in the latter, Fig. 213).
In the Equisetinæ the sporangia are situated in a small number on the
underside of shield-like leaves, and in Lycopodinæ, singly, in the
axils of the fertile leaves, which are alike and bear either micro- or
macrosporangia. In the Phanerogams there is a great difference between
the stamens and carpels.

  [Illustration: FIG. 241.--_Cycas_: _a_ stamen (nat. size) seen
  from the under side; _b_ four pollen-sacs, not yet open, forming
  a “sorus”; _c_ three open pollen-sacs; _d_ a pollen-grain.]

  [Illustration: FIG. 242.--Stamens of _Araucaria_ (pollen-sacs
  long and pendulous).]

  [Illustration: FIG. 243.--Male flower of _Taxus_.]

  [Illustration: FIG. 244.--_A_ Cross section through a
  quadrilocular anther in different stages of development: _s_ the
  seam where it bursts open; _vf_ vascular bundle; _k_ connective.
  _B_ A stamen. _C_ Another stamen seen from the front (_f_) and
  from the back (_b_).]

=Stamens.= In the lowest Phanerogams (_Cycadeæ_) there are many
indications of relationship to the Ferns. The stamens are flat and
broad, and have _on the back many pollen-sacs_ (_microsporangia_)
arranged in small groups (true _sori_), which even have a small
“placenta,” similar to the one possessed by the Ferns, and open towards
the inside by a longitudinal cleft (Fig. 241, compare Fig. 213). A
section of the _Coniferæ_ agree more closely with the Equisetaceæ, in
having a few (three to eight) pollen-sacs arranged on the underside of
more or less shield-like leaves (Figs. 242, 243, compare with Fig. 224
_a_, _c_, _d_). In the Abietaceæ the number of sporangia is diminished
to two, which are placed also on the lower side (Fig. 267) of a stamen.
The number of _pollen-sacs_ (microsporangia) in the _Angiosperms_ is
nearly always four to each stamen; they are longitudinal projections
which are placed in pairs on each side of the central line of the
stamen, two on the edge, and the other two generally on the side which
is turned inwards; the pollen-sacs generally dehisce longitudinally
(quadrilocular anthers, Fig. 244). A few, for instance Orchidaceæ and
Asclepiadaceæ, have only two pollen-sacs (bilocular anthers); and in
others, such as _Solanum_ and the Ericaceæ, they open by pores; in
Lauraceæ and Berberidaceæ, by valves. The part of the stamen which
bears the pollen-sacs is termed the _anther_. Most frequently this is
supported by a stalk known as the _filament_.

  [Illustration: FIG. 245.--A carpel of _Cycas revoluta_ with 5
  ovules (_s_), at half to one-third nat. size.]

  [Illustration: FIG. 246.--Carpel with 2 ovules of _Ceratozamia
  robusta_ (1/1).]

=Carpels.= The simplest forms of carpels are found in _Cycas_. In
this genus both the foliage and fertile leaves are pinnate, and hence
present great similarity; the ovules (macrosporangia) are situated on
the margin of the central portion, just as the sporangia are placed
on the edge of the fertile leaf of _Ophioglossum_ (Fig. 245, compare
with Fig. 209). The carpels of the other Cycadeæ present greater
divergence from the foliage-leaves, being peltate, for instance, in
_Zamia_ and _Ceratozamia_ (Fig. 246). The ovules in the Coniferæ are
situated on the upper side and near the base of the ovuliferous scales,
almost in the same position as the sporangia in the Lycopodinæ (Figs.
269, 272, 273 _H_, compare Figs. 230, 239). In _Taxus_ the uninclosed
ovule is placed on the apex of a shoot (Fig. 264). In all these plants
the ovules are _not enclosed_ by the carpels, that is, they are not
enclosed in chambers formed by the turning in of the walls of the
carpel, and hence the name _Gymnospermæ_ is given to them. In the
higher Flowering-plants, the _Angiospermæ_, the ovules are distinctly
situated on the edge, the upper surface, or base of the carpel; but
the carpel closes round the ovules which are therefore enclosed in a
chamber--the _ovary_. In a few cases, for example in the Polygonaceæ,
an ovule is situated apparently on the apex of the stem itself, as
in the Yew; in other cases, as in the Primulaceæ, many ovules are
apparently developed on the apex of the stem, which seems to have been
specially adapted as a placenta, but it is also possible and correct
in these cases to suppose that the ovules are in reality developed
on the carpels.[22] A single fully-developed carpel or a collection
of carpels joined together is termed the _pistil_. The extremity of
the carpel, which is specially developed to catch the pollen-grains
and form a suitable nidus on which they may germinate, is called the
_stigma_. The united edges of a carpel which bear the ovules are termed
the _ventral suture_. The back of the carpel forms the _dorsal suture_.
The Marsiliaceæ take a position among the Hydropterideæ analogous to
that occupied by the Angiosperms; the sporangia are in a corresponding
manner enveloped in a closed leaf.

The collection of stamens in a flower is termed the _andrœcium_,
and all the carpels, whether individually free or united into one
pistil, the _gynœceum_.

The =Sporangia=. The asexual generation of the _Mosses_ is the
sporogonium, in which the spores arise in tetrads from the
mother-cells. The sporangia in the _Filicinæ_ take their origin either
from a single cell (Leptosporangiatæ) or, what probably may be regarded
as an older stand-point, from a group of cells (Eusporangiatæ). In both
cases there may be distinguished in a mature sporangium three tissues,
which have different significance (Fig. 204): (1) an external layer,
the _sporangium-wall_, most frequently composed of one layer of cells
made up of cells of dissimilar structure, so that on desiccation the
wall is ruptured and the sporangium opens in a definite manner; (2)
an internal group of cells, consisting of the _spore-mother-cells_,
developed from an archesporium, and which by division into four gives
rise to the _spores_; (3) a layer of cells lying between the two
already mentioned, which is dissolved before maturity. The intermediate
cellular layer, which directly surrounds the spore-forming cells, is in
form and contents more worthy of note than the others, and is termed
the _tapetum_. The construction of the sporangium in the _Equisetinæ_
and _Lycopodinæ_ is in the main the same.

  [Illustration: FIG. 247.--Development of an anther. _A_
  Transverse section of a young anther of _Doronicum macrophyllum_.
  The formation of the 4 pollen-sacs commences by divisions of
  the hypodermal cells (at _m_, for instance). These cells divide
  by periclinal walls into external cells which only take part in
  forming the anther-wall; and internal cells, which correspond to
  the Archesporium, and from which the spores are derived. These
  spore-forming cells are drawn with thicker walls in _B-E_. The
  commencement of the vascular bundle is seen in the centre. _B_ An
  older stage; the pollen-sacs already project considerably. It is
  the cells in the hypodermal layer which are active and in which
  tangential divisions particularly occur; _fv_ vascular bundle.
  _C_ A corresponding longitudinal section. _D_ Transverse section
  through an older anther, the thickness of the wall outside the
  mother-cells of the pollen-grains is already increased, and it
  becomes still thicker by the division of the hypodermal cells:
  its most external layer of cells but one, becomes transformed
  into the “fibrous cells.” _E_ Transverse section of a still
  older pollen-sac of _Menyanthes_; _sm_ are the mother-cells of
  the pollen-grains surrounded by the tapetum (_t_), external to
  the tapetum is the anther-wall, which is still far from being
  fully developed. The sub-epidermal layer becomes “fibrous,” and
  the cells lying inside it become dissolved, together with the
  tapetum.]

In the PHANEROGAMS the =Microsporangia= are termed =Pollen-sacs=.
They take their origin from a large group of cells, which, in the
Angiosperms, lie immediately beneath the epidermal cells of the anther.
In the developed, but not yet mature, sporangium (pollen-sac) there are
to be found: (as in the Vascular Cryptogams) (1) an internal group of
mother-cells which give rise to the _pollen-grains_ (_microspores_),
in this case also formed in tetrads; (2) a group of cells surrounding
these, of which the internal ones form a _tapetal layer_, similar to
that in the Vascular Cryptogams; the tapetum and some of the cells
surrounding it in this group, become dissolved before maturity; the
more external ones, on the other hand, are provided with peculiar
thickenings, and form the “fibrous” layer by the aid of which the
dehiscence of the anther takes place; (3) an external layer, the
epidermis, enclosing all the other layers (Fig. 247).

   In some Coniferæ (_Cupressus_, _Thuja_, and several species
   of _Juniperus_) the microsporangia (pollen-sacs), which are
   situated on the under side of the stamen, are covered by a
   thin structure which seems to be a continuation of the lamina
   and which is supposed to be homologous with the indusium of the
   Ferns.

  [Illustration: FIG. 248.--Development of the ovule in the Red
  Currant, _Ribes rubrum_, arranged alphabetically in the order
  of development. _A_ Is the youngest stage, _E_ the oldest. _ii_
  Inner integument; _ie_ outer integument; _nc_ nucellus; _m_
  archespore (mother-cell of the embryo-sac).]

=The Ovule= in the Phanerogams arises most frequently on a projecting
portion of the carpel, termed the _placenta_. The ovules (compare the
sporangium of the Eusporangiatæ and especially the pollen-sac) take
their origin from a _group of cells which lies beneath the epidermis_
(Fig. 248 _A_, _B_). First of all a small papilla is formed, which is
later on provided with a _vascular bundle_ and becomes the _funicle_;
this probably has the same value as the projections (“placenta”) on
which the sori in the Ferns are attached. Only _one_ =macrosporangium=
(_nucellus_; Fig. 248 _nc_) is developed at the apex of the funicle.
This arises by a process of cell-division exactly corresponding to
that by which the pollen-sacs are formed (Fig. 248 _C-E_), with this
difference only, that while a great _many_ cells may be distinguished
in each pollen-sac, which forms pollen-grains by tetrad-division, only
a few are found in the ovule, and all these moreover are _suppressed,
with one single exception_ which developes into the =macrospore=
(=embryo-sac=) without undergoing a division into tetrads. The wall of
the embryo-sac, in the Gymnosperms, may be thick and divided into two
layers and partly cuticularized, as in the spores of the Cryptogams
which are to be set free. In the Angiosperms, on the other hand, the
wall is extremely thin.

The pollen-sac thus stands in the same relation to the nucellus as the
microsporangium does to the macrosporangium: in the pollen-sacs and
microsporangia a _number_ of spores arise by the tetrad-division of
several mother-cells; in the nucellus and macrosporangium, a reduction
of the cells already formed takes place to such an extent that the
number of macrospores becomes one (_Salvinia_, _Marsilia_, Phanerogams)
or four (_Selaginella_), or rarely a large number as in _Isoëtes_.

In the Ferns, as stated on page 210, etc., _indusia_ covering the
sori very often occur. Horsetails and Club-Mosses have no indusium;
but in all Phanerogams cupular or sac-like structures (_integuments_)
are found which envelop the nucellus. These develope from the upper
end of the funicle (_ii_ and _ie_, in Fig. 248; _y_ and _i_, in Fig.
249) and enclose the nucellus on all sides as a sac, leaving only a
small channel at the apex of the nucellus--the _micropyle_--(Fig. 249)
through which the pollen-tube proceeds to the embryo-sac. The ovules
of the Gymnosperms have only one integument (Figs. 251, 264, 269, 274)
and the same is the case with the majority of the Sympetalæ and a few
Choripetalæ; but the Monocotyledons and most of the Choripetalæ have
two integuments (Fig. 249).

  [Illustration: FIG. 249.--Various forms of ovules: _A_ an erect
  ovule (_orthotropous_); _B_ reversed (_anatropous_); _C_ curved
  (_campylotropous_): _k_ the nucellus (shaded in all the figures);
  _s_ the embryo-sac; _ch_ the base of the ovule (chalaza); _y_
  and _i_ the external and internal integuments, the dotted line
  denotes the place where the scar (_hilum_) will form when the
  seed is detached from the funicle.]

In shape the integuments resemble very closely the cupular indusium of
the Hymenophyllaceæ, certain Cyatheaceæ (Fig. 212 _E_), and _Salvinia_
(Fig. 218); that they are really homologous with these is probable, but
is not proven. Some authorities regard them as structures found only in
the Phanerogams.

The ovule is thus a “_monangic_” (_i.e._ reduced to 1 sporangium, the
_nucellus_) _sorus_, situated on a funicle, and enclosed by one or two
cupular _indusia_, the integuments. Some of the ovules are _erect_
(_orthotropous_), others _curved_ (_campylotropous_), the majority
_reversed_ (_anatropous_) (Fig. 249).

   [Goebel (1884 and earlier) with Strasburger considered the
   entire ovule of the Phanerogams as homologous with the
   macrosporangium, the integuments however as new structures in
   contradistinction to the Ferns: the funicle then corresponds
   to the stalk of the sporangium. The integuments of the ovule
   (according to Goebel, 1882) differ from the indusium of the
   Fern-like plants in being developed from the basal portion of
   the nucellus and are not, as in the Ferns and _Isoëtes_,
   a portion (outgrowth) of the leaf which bears the sporangia
   (_K_).]

The nucellus is the only macrosporangium which never opens; _the
macrospore remains enclosed in it_, and _the macrosporangium remains
attached to the mother-plant_. It is therefore essential that the
_method of fertilisation_ which is employed should be very different
from that of the Cryptogams. _The pollen-grains must be transferred
to the ovule_, and retained either by a drop of mucilage at the
micropyle (Gymnosperms) or by the stigma on the carpels (Angiosperms).
Fertilisation by spermatozoids, which are freely motile in water, is
abandoned in the Phanerogams.

Many other modifications, unknown in plants of more simple structure,
take place, for instance, in the shoots which bear the fertile
leaves; especially in the form of the stem or _thalamus_ (hypogynous,
perigynous, epigynous); in the development of the perianth which stands
in intimate connection with the special means employed to effect
fertilisation; with respect to the different grades of union found
in the leaves; in the union of the flowers into aggregations of a
higher order (inflorescences), and at the same time the production of
“floral-leaves” (page 235).


               =The sexual generation. The Fertilisation.=

The sexual generation in the _Mosses_ is relatively well developed,
because not only the protonema, but all the other vegetative parts
of the Moss-plant, in addition to the archegonia and antheridia,
belong to it. In the groups which follow, a gradual but increasing
reduction of the sexual generation takes place, and at the same
time an indication of sex is found in the prothallia, which finds
expression in the forms of the spores themselves. In the majority
of cases among the _isosporous_ Vascular Cryptogams, the sexual
generation--prothallium--is a green, leafy expansion which can sustain
itself by the assimilation of carbonic acid, and by the absorption
of nutriment from the soil by means of root-hairs. In some plants
(_Ophioglossaceæ_, _Lycopodium annotinum_) the prothallium is a
subterranean, pale, tubercular body, but in these instances it is
relatively large. In the _heterosporous_ Vascular Cryptogams and
in the _Phanerogams_, the prothallium is much more reduced, both as
regards its size, and also with respect to the number and structure of
the antheridia and archegonia.

1. =The Microspores.= The PROTHALLIUM in all Vascular Cryptogams which
have unequal spores, consists of a single, vegetative (barren) cell,
which plays a very unimportant part in the life of the prothallium
(Fig. 233 _A_). In _Salvinia_ it is somewhat elongated and tubular,
because it must break through the sporangium (Fig. 214); but in other
cases it is very small and lenticular. In all these plants only one
antheridium is formed. In _Salvinia_ it consists of 2 cells whose walls
are ruptured in order that the spermatozoids may be liberated (Fig. 214
_B_, _C_). In _Marsilia_, _Isoëtes_, and _Selaginella_ the prothallium
does not leave the spore, and consists for the most part of primordial
spermatozoid-mother-cells _without cell-wall_, which on germination are
ejected so that the spermatozoids are set free.

In the Phanerogams, the microspores have from olden times been termed
_pollen-grains_.

In the GYMNOSPERMS the prothallium is reduced to 1, 2 or 3 small cells,
placed on one side of the mature pollen-grain (at the top in Fig. 250
_I_, _II_, and in Fig. 267 _N_) and which do not play any part in
the germination of the pollen-grain. The antheridium is represented
by the remaining portions of the interior of the pollen-grain, that
is, it consists of a large cell with a nucleus which does not even go
so far as the antheridium of _Selaginella_ and become divided into
spermatozoid-mother-cells without cell-wall, for even these cells are
not formed. The unicellular antheridium grows, on the germination of
the pollen-grain, into a tubular body known as the _pollen-tube_,
formed from the inner wall of the pollen-grain (Fig. 250), which works
its way down the micropyle to the oosphere. The fertilisation takes
place by diosmosis through the cell-wall, and consists here also of the
coalescence of the nucleus of the pollen-tube (the sperm-nucleus, male
pronucleus) with that of the oosphere.

In the ANGIOSPERMS the reductions proceed still further. The barren
cell, which represents the prothallium, was in the last group separated
from the antheridium by a true cell-wall, but in the Angiosperms a
membrane at most, but no firm cell-wall, is formed. The pollen-grain
contains two cells, a vegetative and a free generative cell. Both these
pass into the pollen-tube, but the vegetative cell disappears about
the time the pollen-tube reaches the ovule; while the generative cell
divides into two: one, the sperm-nucleus coalescing with the nucleus of
the oosphere, the other being absorbed (_Lilium_, after Guinard).

The Gymnosperms prove in yet another point that they are more
closely related to the Cryptogams than are the Angiosperms. When the
pollen-grain begins to germinate the external wall ruptures as in the
Cryptogams (Fig. 250), but in the Angiosperms special germ-pores are
formed in the cell-wall for the emergence of the pollen-tube.

  [Illustration: FIG. 250.--_I_ Pollen-grains of _Cupressus_; at
  the top is seen one prothallium-cell. _II_ Germinating; _c_
  pollen-tube; _a_ the extine; _b_ the intine.]

2. =The Macrospores.= The prothallium in _Salvinia_ and _Marsilia_ is
still rather large, green, and capable of the independent assimilation
of carbon. It projects more or less from the macrospore and bears
(in _Marsilia_ only one, in _Salvinia_ several) archegonia, which
however are embedded to a greater degree in the prothallium, and are
more reduced than the archegonia of the true Ferns and Horsetails
(Figs. 215, 216). The prothallium is still more reduced in _Isoëtes_
and _Selaginella_; _partly_ because it is smaller and is in a higher
degree enclosed in the spore, it also contains less chlorophyll, or
is entirely without chlorophyll, and in consequence incapable of
independent existence, whilst the number of archegonia is less; and
_partly_ because the archegonia are themselves reduced, the cells of
the neck are fewer and embedded to the level of the surface of the
prothallium without any, or with only a very slight projection (Figs.
235, 236).--Finally, the prothallium with its archegonia begins to
develope in _Selaginella_ while the macrospore is still within its
sporangium, and before it is set free from the mother-plant. After
the spores are set free and germination has commenced, the spore-wall
ruptures and the prothallium is exposed.

  [Illustration: FIG. 251.--Longitudinal section of ovule of _Abies
  canadensis_. Inside the integument (_i_) is seen the nucellus,
  _n_; _m_ the micropyle. In the interior of the nucellus is
  seen an oval mass of cells, the endosperm, and at its top two
  archegonia, _c_. The ovule is turned in such a way that the
  micropyle points upwards, but usually it turns downward in the
  _Abietineæ_.]

  [Illustration: FIG. 252.--The apex of the nucellus (_n_) of
  an ovule of _Abies_: _l_ long-shaped cells which guide the
  pollen-tube; _s_ the wall of the macrospore (embryo-sac); _h_ the
  neck-cells of the archegonium; _k_ the ventral canal-cell; and
  _c_ the central cell (oosphere). The archegonia of the Cryptogams
  should be compared with this (see pages 181, 208, 216).]

The GYMNOSPERMS go still further. The macrospore (embryo-sac)
germinates and forms internally a cellular tissue, designated in former
times by the name of _albumen_ (endosperm), which is _homologous with
the prothallium_. It always _remains enclosed in the embryo-sac_, and
is a parenchymatous mass containing a large supply of nourishment. In
the upper part of the endosperm a number of archegonia are developed
which are in the main constructed in the same manner as those in the
Cryptogams, but are still more reduced, the neck consisting only of 4,
2, or 1 cell (Figs. 251, 252). The ventral canal-cell is also formed,
in the majority, as a small portion cut off from the large central
cell just beneath the neck; the larger remaining portion becomes the
oosphere. When the pollen-tube has passed down to the oosphere (Fig.
253) and fertilisation has been effected, the oospore commences a
cell-formation, the final result of which is the formation of _an
embryo_ (_the asexual generation_) which is provided with a thinner,
lower end, termed the suspensor. The embryo is forced more or less
into the endosperm in which it may rest for a longer or shorter
time, and generally is developed to such an extent that it has a
distinct primary-root (radicle) and stem (plumule) with one or more
embryo-leaves (cotyledons).

   When the oosphere has been fertilised its nucleus sinks down
   to its lower end, and by repeated division into two, forms
   four cells lying in one plane (Fig. 253, see base of the left
   archegonium). Three tiers of cells are now formed by transverse
   division of these four. It is the intermediate one of these
   which elongates and forms the suspensor, or four suspensors, if
   they separate from each other, which push the lowermost four
   cells deep down into the endosperm. It is from these four lower
   cells that the embryo (or four embryos when the suspensors
   separate) is developed, but never more than one embryo attains
   full development. As several archegonia are contained in one and
   the same ovule, all of which are capable of forming embryos,
   there is the possibility that several embryos may be developed
   in a seed (polyembryony), but usually only one embryo attains
   perfect development.

  [Illustration: FIG. 253.--The apex of the nucellus (_n_) of
  _Abies_ in longitudinal section: _c_, _c_ the oospheres of
  the two archegonia; the embryo-formation has commenced at the
  bottom of the left archegonium; _s_ wall of the macrospore; _p_
  pollen-grains; _r_ pollen-tubes.]

  [Illustration: FIG. 254.--Embryo-sac of _Carex præcox_: _syn_
  synergidæ; _kb_ the oosphere; _c_ the central nucleus; _ant_ the
  antipodal cells.]

At the same time that the embryo is being developed, other changes
are taking place in the ovule, especially in the integument which
becomes the shell of the seed (_testa_). The endosperm grows, and the
embryo-sac supplants the cells of the nucellus. The _seed_ is now
formed, and it consists in its most complete development, as in this
instance, of three parts:

(1) The _testa of the seed_, formed by the enveloping integuments,
with the remainder of the tissue of the nucellus lying outside the
embryo-sac (the macrosporangium).

(2) The _endosperm_ or prothallium.

(3) The _embryo_.

  [Illustration: FIG. 255.--Diagrammatic longitudinal section
  through an anatropous ovule shortly after fertilisation; _a_
  and _i_ are the two integuments; _f_ the funicle; _k_ the
  nucellus; _S_ the embryo-sac, with the incipient formation of
  nutritive-tissue; _E_ the embryo; _P_ the pollen-tube passing
  through the micropyle (_n_) to the oosphere.]

The reduction in the ANGIOSPERMS is carried to the extreme limit. In
the embryo-sac (the macrospore) the nucleus by continued division
produces a prothallium consisting of primordial cells (Fig. 254).
In the upper end of the embryo-sac (which is nearest the micropyle)
are three cells, two of which are termed the “co-operating cells”
(_synergidæ_) and the third is the _oosphere_. Three others are
placed at the opposite end of the embryo-sac and are therefore termed
the “antipodal cells.” Finally, a large cell is also formed, which
occupies the space between the two groups and whose cell-nucleus, the
central definitive nucleus, lies in the centre of the embryo-sac.
These primordial cells are the slight remnant of the prothallium. The
entire structure of the archegonium, with its neck and canal-cells,
has disappeared, and nothing is left but the indispensable _oosphere_.
When the oosphere has been fertilised, and has commenced the cellular
divisions which lead to the formation of the embryo (Fig. 255), the
synergidæ and antipodal cells are absorbed, and a cell-formation
begins by a new process which emanates from the definitive nucleus and
by which a parenchymatous cell-tissue, the nutritive-tissue, arises
which may perhaps be considered as homologous with the endosperm of
the Gymnosperms. The difference is that the nutritive-tissue of the
Angiosperms is formed in two parts with an intervening interruption;
the primary nutritive-tissue is first formed, and after fertilisation
is absorbed, with the exception of one cell, which continues the
development and gives rise to the nutritive-tissue proper, which is
formed in the first instance of primordial cells, and later on of a
cellular tissue; this nutritive-tissue formed in the embryo-sac is
termed “endosperm”; in a few instances[23] a tissue which is derived
from the nucellus functions as nutritive-tissue, and is termed
“perisperm.” In many plants the seeds, when ripe, contain a very
rich nutritive-tissue, in addition to the embryo, for the purpose
of its nourishment during germination. These are termed albuminous
(endospermous) seeds, in distinction to the ex-albuminous, or those in
which the nutritive-tissue is stored in the embryo itself, before it is
completely developed, and used for its sustenance.

In addition to the changes which fertilisation produces in the ovule
itself, it also gives the impetus to a series of changes in the
entire shoot which bears the ovule. The perianth, stamens, and style,
generally wither, because the part they play is at an end; the wall
of the ovary grows and becomes the wall of the fruit (pericarp).
The entire gynœcium of a flower, transformed as a consequence of
fertilisation, is termed a _fruit_. It consists of two parts, the
_pericarp_ and the _seeds_, and according to the nature of the
pericarp, the fruit is termed a capsule, nut, berry, or drupe.

The chief characteristic of the Phanerogams does not lie in the
formation of the flower (although they may quite properly be termed
“Flowering-plants”), because Equisetums and Lycopods have reproductive
shoots as highly differentiated as those of certain Gymnosperms and
other Phanerogams. As regards the SEXUAL GENERATION the characteristics
are found:--(1) in its great reduction; (2) in the transmission of the
microspore (pollen-grain) to the macrosporangium, and its germination,
with the formation of a _pollen-tube_ (antheridium), the protoplasm of
which is not differentiated into spermatozoids; (3) in the fact that
the macrospore (embryo-sac) never leaves its sporangium (nucellus);
and further in the Angiosperms, (4) in the peculiar development of the
nutritive-tissue in two parts; and (5) in the great reduction of the
archegonium.

As regards the ASEXUAL GENERATION the characteristic feature is that
this generation is formed whilst the sporangium is still attached to
the mother-plant, and for a long time is nourished by it; and that
after the sporangium has become detached from the mother-plant, it
spends a longer or shorter resting period as the embryo in the seed
(enveloped by the testa), and does not make its appearance until
the “germination” of the seed. In addition the shoot which bears
sporangia undergoes greater modification than in the case of the
Flowerless-plants.

The Phanerogams are separated into two Divisions as follows:--

Division 4. =Gymnospermæ.= The ovules, as well as the seeds, are borne
_naked_ on the surface of _open carpels_, or on the apex of a stem
(ovary wanting). The pollen-grains are conveyed by the wind to the
ovules, and caught by drops of mucilage, secreted by the micropyle.
A “stigma” is _wanting_. The entire _female prothallium_ (_the
endosperm_), which serves for the nourishment of the embryo, is _formed
before fertilisation_. The archegonia are _embedded in the upper part
of the prothallium. The pollen-grains are “multicellular,” i.e._ there
is always in their interior a distinct prothallium, formed by 1–3
cells, and a larger cell which gives rise to the pollen-tube.

Division 5. =Angiospermæ.= The carpels surround the ovules and form
an entirely closed chamber (_ovary_), in which the ovules mature and
ripen into seeds. The surface of a portion of the apex of the carpel
is transformed into the “stigma,” which, by a sticky fluid and also by
hair-structures, is capable of retaining the pollen-grains conveyed to
it by the wind, or more frequently by insects. The pollen-tube grows
from the stigma, through the “conducting cellular tissue” (_style_),
to the ovules. The pollen-grains contain two cells, a vegetative and
a free generative cell. The latter passes into the pollen-tube and
there divides into two, one of which is the sperm-nucleus. The female
prothallium, which is intended to serve as nutritive-tissue, is formed
_after fertilisation_. Archegonia are wanting.



                             DIVISION IV.

                             GYMNOSPERMÆ.


The following characters should be added to those already given on page
2:--

The Gymnosperms comprise only trees or shrubs. The flowers are always
_unisexual_ and destitute of perianth (except _Gnetaceæ_); the female
plant of _Cycas_ is the only one which has no flower. The MALE FLOWERS
are constructed on the same type as the cones of the Horsetails and
Club-Mosses, and are _most frequently long shoots_ (Figs. 243, 258, 260
_A_, 267 _J_) bearing a number of spiral or verticillate stamens. The
FEMALE FLOWERS are of a more varied structure (see the orders). The
OVULE _is orthotropous_ (except _Podocarpus_ which is anatropous) and
projects from the carpel uprightly, inverted, or horizontally; it has
usually _only one integument_ (compare however Taxaceæ) which proceeds
from the upper part of the nucellus, so that the embryo-sac in part is
placed below the integuments (Figs. 251, 264). The drop of mucilage
which catches the pollen-grains dries up and draws the pollen-grain
through the micropyle to a space just above the nucellus--_the
pollen-chamber_--in which the germination of the pollen-grain commences.

In each seed, only one of the many embryos which are formed proceeds to
its full development. The seed is always _endospermous_, and the embryo
has one, two, or a whorl of several cotyledons. A vigorous primary
root is developed on germination. THE VASCULAR BUNDLES in the stem are
arranged in a ring, and _increase in thickness_ takes place by a closed
cambium-ring which forms bast (_phlœem_) externally, and wood (_xylem_)
internally with distinct annual rings, _as in the Dicotyledons_. Only
certain of the Cycadeæ deviate from this arrangement. The _secondary
wood_ is very uniform, as it is almost exclusively _formed of
tracheides_ with bordered pits, but _true vessels are wanting_; this
also indicates a relationship with the Pteridophyta (see page 202).

The Gymnosperms are biologically lower than the Angiosperms; they are
wind-fertilised, and without extra floral-nectaries.

This Division embraces three classes: CYCADEÆ, CONIFERÆ, And GNETEÆ. It
is no doubt monophyletic, and has taken its origin from heterosporous
Ferns, now extinct, most nearly related to the Ophioglossaceæ and
Marattiaceæ. The Cycadeæ appear to be the oldest class. The Coniferæ
are related to these through Ginkgo. The Gnetaceæ are more isolated.
The Division is not continued into the higher Flowering-plants; it has
evidently attained its highest development, and is now in a retrograde
condition. The similarity which has often been pointed out between
certain Coniferæ and Lycopodinæ is only in analogous resemblances, and
does not entitle one to suppose that there is a nearer relationship, or
that the former take their origin from the latter.


                          Class 1. =Cycadeæ.=

The stem is very _rarely ramified_. The leaves are _large_, _pinnate_,
and arranged spirally. The flowers are _diœcious, without perianth_.

  [Illustration: FIG. 256.--_Cycas circinalis_ (female plant). The
  carpels are seen hanging from the top of the stem. Three leaves
  with the leaflets still rolled up project almost vertically into
  the air, from the centre of the crown.]

There is only one order, the =Cycadaceæ=.--In habit they resemble the
Ferns, especially the Tree-Ferns (compare Figs. 207 and 256). The stem
is tubercular (Fig. 258), or cylindrical (Fig. 256), but not very tall
(as much as about 12 metres), and very rarely ramified. [In Ceylon,
unbranched specimens of _Cycas_ are rarely met with in the wild state.
The stems of _C. circinalis_ occasionally branch in greenhouses.]

The LEAVES are arranged spirally, and so closely together that no
free stem-surface is left between them, and have only a slight sheath
(which is not amplexicaul, as in the Palms). They are compound (most
frequently pinnate; in _Bowenia_, bipinnate); in some genera the leaves
are rolled up in various ways, resembling the vernation in Ferns (Fig.
257); they are leathery and perennial. In some, stipules are present,
as in the Marattiaceæ. Groups of scale-leaves alternate in the majority
with groups of foliage-leaves.

  [Illustration: FIG. 257.--_Cycas circinalis._ Part of a young
  leaf with circinate leaflets.]

  [Illustration: FIG. 258.--A male plant of _Stangeria paradoxa_
  (about 1/15 nat. size).]

  [Illustration: FIG. 259.--Female cone of _Zamia integrifolia_
  (½-⅓ nat. size). The male cone is very similar externally.]

The FLOWERS are without perianth. The MALE FLOWER is sometimes an
enormous collection of stamens (Fig. 258), which are flat in some
(_Cycas_, Fig. 241), shield-like in others (_Zamia_, _Ceratozamia_)
like the sporophylls in Horsetail (Fig. 259); but in all, the
pollen-sacs are situated in large and varying numbers on the back of
the stamens, and arranged in groups of 2–5, like the sporangia in the
sori of the Ferns (Fig. 241 _b_, _c_). FEMALE FLOWERS _are wanting_ in
_Cycas_, because the carpels do not terminate the apical growth of the
stem. After a group of foliage-and of scale-leaves, a group of carpels
is developed, which are pinnate and resemble the foliage-leaves,
bearing on their edges a number of ovules (most frequently 5–6)
(Figs. 245, 256); the same stem produces successively scale-leaves,
foliage-leaves, and carpels. The differentiation is not much more
advanced than in certain Ferns (_Struthiopteris_, _Blechnum_), where
barren and fertile leaves of different form regularly alternate. _The
other genera have female flowers_; the carpels are shield-like in
_Zamia_ and _Ceratozamia_ (Fig. 246), and collected into cone-like
flowers, which terminate the growth of the stem (Fig. 259). The number
of ovules in these instances is two to each carpel.

The SEEDS are large (most frequently 2–6 centimetres long) and
plum-like; the external layer of the testa is fleshy, while the
internal one is hard and horny. There are two systems of vascular
bundles in the testa, one outside, the other inside the stone. The
embryo is straight, attached to the end of the suspensor, which is
often long, filamentous, and rolled up; it has one or two cotyledons.

   The embryo in _Ceratozamia_ and others is very slightly
   developed, at the time when the ripe seed is detached from
   the carpel; and it is not until after sowing that its further
   development and germination proceed. This calls to mind the
   Cryptogams, especially _Selaginella_, whose macrospores are
   thrown off filled with endosperm; but the oosphere is not
   fertilised till after the separation of the macrospore from the
   parent-plant, while in the Cycadeæ fertilisation is effected
   before the separation. In _Cycas_ the testa may rupture, and
   the endosperm grow and become green in the light, even though
   no embryo has been formed. This also is an indication of its
   prothalloid nature.

   Gum-passages are present in all organs. Collateral vascular
   bundles, with spiral and scalariform tracheides, are found;
   and normal thickening takes place by means of a cambium.
   An exceptional mode of growth is found in _Cycas_ and
   _Encephalartos_, the cambium ceases to divide after a time
   and is replaced by a new cambium which arises in the cortical
   parenchyma just outside the bast, and which forms a new ring
   of xylem and phlœem. This may be repeated so that a number of
   concentric rings are produced. In _Ceratozamia_, structures
   resembling corals extend from the roots in a vertical direction
   and appear on the surface of the soil; these are peculiar roots,
   in which a symbiotic Alga (_Anabæna_) is found.

   The Cycadeæ were formerly (from the Coal period to the Later
   Cretaceous) far more numerous than at the present day. They
   appear to have been most numerous in the Trias and Jurassic.
   The remnant (75 species) which have persisted to the present
   time are found in all tropical countries. _Cycas_ (Trop. and
   Sub-trop., Eastern Hemisphere); _Dioon_ (Mexico); _Macrozamia_
   (Australia); _Encephalartos_ (Trop. and S. Africa); _Stangeria_
   (Fig. 258, Sub-trop. South and East Africa); _Bowenia_ (Trop.
   Australia); _Ceratozamia_ (Mexico, New Granada, Western Brazil);
   _Microcycas_ (Cuba); _Zamia_ (Trop. and Sub-trop. N. America.)

   USES. Sago is made from the starch-containing pith of _Cycas
   revoluta_ and _circinalis_. The leaves are often used at
   funerals and church festivals, under the name of “palm-branches.”


                  Class 2. =Coniferæ= (=Pine-trees=).

The stem _branches freely_. The leaves are _entire_, relatively small,
linear or reduced to scales. The flowers are without perianth. The
ovules naked. It is seldom that the female flower is reduced to only
one carpel.

Whilst the Cycadeæ principally resemble the Ferns, the Conifers partly
resemble the Lycopods, and partly the Equisetums--the former especially
in the _needle- or scale-like_, leathery, simple, and often perennial
leaves (“evergreen plants”), which _never possess stipules_ (Figs. 263,
270, 272). _Ginkgo_ deviates from this, being no doubt the oldest,
and the Conifer which stands nearest to the Cycadeæ (Fig. 260). The
resemblance to the Equisetums is especially owing to the fact that
the stem ramifies abundantly, and often very regularly, forming a
pyramid with verticillate branches. In addition to the foliage-leaves,
scale-leaves (bud-scales) are present in the majority of species.

The FLOWERS are monœcious or more rarely diœcious. _Perianth is
wanting._ The stamens of the _catkin-like male flowers_ (Fig. 267,
_J_) are of different forms, but as a rule more or less shield-like.
As in the Cycadeæ, the pollen-sacs are in all cases situated _on the
underside_. There are, as a rule, two pollen-sacs (the Abietaceæ, Fig.
267), or 3–5, (the Cupressaceæ and Taxaceæ, Fig. 243); a few have more,
_e.g. Araucaria_ (Fig. 242); they dehisce by clefts.

If, in commencing our consideration of the _female flower_, we begin
with that of _Ginkgo_, we shall observe in the corner of a scale-
or foliage-leaf a small flower, which consists of two carpels, each
bearing one ovule, and reduced almost to the ovule itself (Fig. 260
_C_, _D_). The flower in _Podocarpus_ is still further reduced, viz.
to a single carpel with one ovule, which is anatropous and has two
integuments. This ovule is situated in the axil of a cover-scale (_c_,
in Fig. 262 _D_), and several female flowers of this description are
collected in a small cone, the stalk and bracts of which become fleshy
(Fig. 262 _C_). The external integument also becomes fleshy (an aril).
_Dacrydium_, which is clearly related to _Podocarpus_, has an external
integument which developes more independently as a fleshy aril (Fig.
262 _B_, _B’_). _Microcachrys_ also is clearly allied to these: the
bracts are more fleshy, and the ovule (_i.e._ the female flower) is
protruded beyond the bract (Fig. 262 _A_, _A’_). _Taxus_ stands in a
more isolated position: a flower which has been reduced to an ovule is
situated, in this instance, on the apex of a secondary branch which is
studded with floral-leaves (Figs. 263, 264); an external integument
is developed on all sides and surrounds the seed as a scarlet aril.
According to this conception _the aril corresponds to an external
integument_, and the Taxoideæ thus possess a partly dichlamydeous
ovule. Only _Ginkgo_ and _Cephalotaxus_ appear to deviate from this,
as in these there is only one integument (unless the small outgrowth
indicated by _ar_, in Fig. 260 _D_, really is a rudimentary, external
integument); in CYCADEÆ, to which _Ginkgo_ is most closely related,
there is likewise only one integument. But in these genera the testa
is differentiated into two layers, and the seed resembles a drupe; like
the Cycadeæ there is an external fleshy covering and an internal hard
one, and these two layers may probably be considered homologous with
the two integuments. This theory is also borne out by the arrangement
of the vascular bundles in _Cephalotaxus_ and _Podocarpus_, which
present the xylem in the fleshy external layer to the _outside_ of the
testa, which is therefore the upper side of the integument (Celakovsky).

The coalescence of the integuments into one is only slight in
_Torreya_, more pronounced in _Podocarpus_ and strongest in
_Cephalotaxus_ and _Ginkgo_. Celakovsky terms these ovules
“holochlamydeous.”

If we pass from these to the order PINOIDEÆ, we find the female flowers
collected into catkin-like cones, which have been considered from
various points of view to be sometimes single flowers, at other times
compound inflorescences. The structure in ABIETACEÆ is as follows: a
number of spirally arranged, scale-like leaves, _cover-scales_ (Figs.
267, 268), are situated on a long axis. In the axil of each cover-scale
a larger leaf-like projection, _the ovuliferous scale_, is borne,
which turns the upper side towards its cover-scale (which is shown by
the fact that the wood of its vascular bundles is turned downwards
and towards the wood in the bundles of the cover-scale: Fig. 269).
Two ovules, with micropyles turned towards the central axis, and with
apparently only one integument (Fig. 268), are situated on the dorsal
side of each ovuliferous scale, _i.e._ the side turned away from the
cover-scale. The ovuliferous scales grow after fertilisation, into the
woody or leathery “cone-scales,” which are usually much larger than the
cover-scales. This ovuliferous scale with its axis may, according to
Celakovsky, be considered as a dwarf-branch which is situated in the
axil of the cover-scale, and bears two ovules (in the same way as in
_Ginkgo_, one long-stalked flower, reduced to two ovules, is situated
in the axil of a leaf), and _in this case the external integument of
the ovules_ is expanded into leaf-like bodies, which have united to
form one “_symphyllodium_” (_ovuliferous scale_) which is inverted
so that its dorsal side is turned upwards and bears the nucellus and
the other integument (“hemichlamydeous” ovules). The carpel itself
is therefore in this instance extremely reduced. The keel, or (in
_Pinus_) “mucro” (Fig. 268 _B_), which is found in several genera,
represents then a third carpel, which is sterile. In the other orders
of the Pinoideæ the cover-scales and ovuliferous scales grow more and
more together and finally form one structure, which also is termed a
“cone-scale,” although from its development it cannot be homologous
with the cone-scales of the Abietaceæ. This connation is least in the
TAXODIACEÆ and ARAUCARIACEÆ and may be traced on the upper surface
of the “cone-scale” by the presence of a stronger or slighter ridge
or pad, the free portion of the ovuliferous scale (Figs. 256, 266,
269). It is most strongly pronounced in the CUPRESSACEÆ, in which the
two scales form one single structure, the cone-scale (Fig. 274). The
vascular bundles in the under portion corresponding to the cover-scale,
have the xylem towards the upper side as usual in leaves, whilst
the bundles present in the upper side of the cone-scale, which thus
represents the ovuliferous scale, turn their xylem downwards. The
hemichlamydeous ovules are then situated on the upper side of this
cone-scale. According to this theory the CUPRESSACEÆ appear to be
the youngest type, a view which corresponds with their vegetative
structure. If there is only one ovule in these orders as in _Agathis_
(Fig. 265) and _Araucaria_, then the flower is reduced to a single
carpel and one ovule, as in the case of _Dacrydium_ and _Microcachrys_.
If two or more ovules are present, then the same number of carpels may
be supposed to exist, the external integuments of their ovules being
developed into leaf-like structures which collaterally coalesce to form
a “symphyllodium,” or are suppressed.

According to this theory, which is based on the researches of
Celakovsky, the female flowers of the Coniferæ may be classed thus:--

1. In all cases situated in the axil of a bract and collected into
cones, with numerous flowers or with few or one flower. In _Ginkgo_
only, are they situated in the axil of foliage- or scale-leaves.

2. It is only in _Taxus_ that bracteoles are present.

3. They are formed only from rudimentary carpels, in which the stem
takes no part.

4. The number of carpels in each flower varies from one to many, most
frequently three, of which the central one remains sterile.

5. Each carpel bears only one ovule. The flower which is formed of only
one carpel appears to consist of only one ovule.

6. The ovule has in Taxaceæ either a double integument (Podocarpeæ,
Taxeæ), of which the external is the “aril,” or, as in the Cycadeæ, a
single one, which is homologous with the two united together.

7. The external integument in the Pinoideæ is expanded to form a
leaf-like structure--the ovuliferous scale--and bears on its dorsal
side the ovules, which are thus only provided with one, and that the
inner, integument.

   This later interpretation of the female cones in the Coniferæ is
   more probably correct than the older ones; that, however, which
   appeared in the former issues of this book, may also be stated.
   It was to the effect that each catkin-like female cone is in
   reality a single flower; the cone-scales in the Cupressaceæ
   were single leaves, namely carpels, which bore the ovules on
   the side which is turned upwards; the division into two parts
   which makes its appearance in the other orders, and becomes
   most prominent in the Abietaceæ, was compared with the division
   of a leaf into a barren and a fertile portion, which is found
   especially in Ophioglossaceæ and Marsiliaceæ, or with the ligule
   in _Isoëtes_.

POLLINATION is accomplished by means of the wind. At the period
of pollination the leaves are always so widely separated from one
another, that the ovules can catch the pollen-grains carried to
them by the wind; this is often effected by the mucilaginous drops
which appear at the micropyle, and by the evaporation of which the
pollen-grains are brought in contact with the nucellus. The entire cone
grows considerably as soon as fertilisation has taken place, and the
cone-scales in Pinoideæ close together so that the seeds while maturing
are enclosed, and it is not until the seeds are ready for distribution
that the cone-scales again become separated. In the Pinoideæ, the fully
developed ovuliferous scales are hard and woody; and in this condition
the collection of female flowers is termed a _cone_. In the Taxoideæ,
true cones are the exception. 2–15 cotyledons are present, arranged in
a whorl.

The characteristic feature of this class is the abundance of _resin_,
which is to be found in isolated cells (especially in the cortex),
partly in intercellular glands or passages (both in the cortex and
wood). _Taxus_ is the only genus which has no resin.

   There are about 350 species, mostly from the Northern Temperate
   zone (especially North America and Siberia), where they grow
   gregariously and form the most northern forests. The Juniper,
   Scotch Fir, and Yew are natives of Great Britain.

This class may be divided into two families:--

1. =Taxoideæ.= The ovules have either one integument, the external
part of which is fleshy, and the internal hard and stone-like; or two
integuments, of which the external is the fleshy and coloured “aril.”
“Ovuliferous scales” are wanting. The cones are never woody, but are
generally succulent, the bracts become fleshy, or cones usually are not
developed. The seeds project more or less freely beyond the bracts.

2. =Pinoideæ.= The ovules have two integuments, the external one of
which is leaf-like and becomes developed as the “ovuliferous scale”;
if there are several of these in each flower they unite and form a
“symphyllodium.” This may remain free or unite with the bract. The
cones are most frequently woody, rarely succulent. The seeds are hidden
among the cone-scales.


                         Family 1. =Taxoideæ.=

This family, considered to be most nearly related to the Cycadeæ, also
made its appearance at a very early period. There is only one order.

Order. =Taxaceæ.= The characters have been given above.

_A._ CEPHALOTAXEÆ is the oldest group, presumably the connecting
link between the Cycadeæ and the other Coniferæ. The flower consists
normally of two ovules. Aril wanting. One integument. Seeds
drupaceous.--The flowers in _Ginkgo biloba_ (_Salisburia_) are situated
in the axil of foliage- or scale-leaves. The stamens bear only two
pollen-sacs (Fig. 260 _A_). The female flower has two ovules, placed
together at the end of a long, bare axis (Fig. 260 _C_). Round the base
of the ovule a small collar (_ar_, in Fig. 260 _D_) is found, which
may probably be considered homologous with the collar-like outgrowth
which surrounds the base of the _Cycas_-ovule. The seed resembles a
Plum, and has a fleshy external coat, surrounding a hard internal
layer. The embryo is developed after the seed has fallen off. The
Ginkgo-tree has long-stalked, fan-shaped leaves, more or less indented,
with dichotomous veins resembling certain Ferns--the Adiantums. It is a
native of East Asia, and the only surviving species of a genus which in
earlier times was very rich in species, and distributed over the entire
Northern Hemisphere. _Cephalotaxus_ (Eastern Asia) is related to it.

  [Illustration: FIG. 260.--_Ginkgo_ (nat. size): _A_ a branch with
  a small flowering dwarf-branch (male flower); _B_ a leaf; _C_ a
  flower with two ovules; _D_ a ripe seed; _ar_ collar.]

  [Illustration: FIG. 261.--_Phyllocladus glaucus_: a branch with
  female flowers (nat. size).]

_B._ PODOCARPEÆ. The female flower is reduced to one ovule, placed in
the axil of a bract, or a little forward upon it. The ovule has an
aril (2 integuments).--_Phyllocladus_ (Fig. 261), from New Zealand and
Tasmania, has obtained its name from its flat, _leaf-like branches_,
the leaves proper being scale-like (_f_). The ovules stand _erect_ in
the axil of the scale-like leaves (_c_), and several are collected at
the end of short branches.--_Microcachrys tetragona_ (Tasmania) has
a small female catkin with several spirally-placed, fleshy bracts,
at the end of which the inward and downward turned ovule is attached
(Fig. 262 _A_, _A’_). The ripe cones are red, succulent, and resemble
Strawberries.--In _Dacrydium_ (Tasmania, New Zealand, Malaysia) the
female cone has most frequently only 1–2 (–6) bracts, which resemble
the vegetative leaves; they have also a fleshy aril (Fig. 262 _B_,
_B’_).--_Podocarpus_ (40 species, East Asia, S. Temp.); the bracts of
the female flowers become fleshy, and unite together; only 1 or 2 are
of use in supporting the flowers. The ovules project high above the
apex of the bract, and are _anatropous_, the micropyle being turned
downwards (Fig. 262 _C_, _D_). An aril commences to develope in the
flowering period as an external coating, and later on it becomes fleshy
and coloured.

  [Illustration: FIG. 262.--_A Microcachrys_: female cone (2/1).
  _A’_ A single carpel with its ovule. _B Dacrydium_: branch with
  female flower (3/1). _B’_ The flower; _cp_ the bract; _ar_ the
  aril; _ov_ ovule. _C Podocarpus_: female flower with 2 ovules.
  _D_ Another female flower with 1 ovule, in longitudinal section.]

  [Illustration: FIG. 263.--_Taxus baccata_: branch with two ripe
  seeds (nat. size).]

_C._ TAXEÆ. The female flower is reduced to one ovule, which is
situated _terminally_ on an axis which bears 2–3 pairs of opposite,
scale-like bracteoles; on this account the Taxeæ form a very isolated
group among the Coniferæ.--_Taxus_ (_T. baccata_, the Yew-tree).
_Diœcious_. _The female flower consists of only one ovule_, placed _at
the end_ of a short secondary branch (Fig. 264), which is studded with
scale-like leaves. The aril when ripe is thick, fleshy, and scarlet
(sometimes yellow), and only loosely envelopes the seed (Fig. 263).
The leaves are scattered, flat, linear, and pointed (Fig. 263, 264).
The short male flowers have 5–8 pollen-sacs, pendent from the stamens,
and are surrounded at their bases by scale-like bracteoles (Fig. 243).
_Torreya_ (4 species, N. America and Japan) is closely allied to
_Taxus_. The aril ultimately fuses with the woody inner integument, and
hence the ovule becomes drupaceous, as in Cephalotaxaceæ.

  [Illustration: FIG. 264.--_Taxus baccata_: _A_ shoot of _Taxus_
  with female flowers at the time when the ovules are ready for
  pollination. _B_ Leaf with flower in its axil (nat. size). _C_
  Longitudinal median section through a female shoot; _v_ growing
  point of primary shoot; _a_ commencement of aril; _i_ integument;
  _n_ nucellus; _m_ micropyle.]

   USES. _Taxus baccata_ is usually planted in gardens, especially
   in hedges. Its wood is very hard and is used for wood-carving.
   The shoots are poisonous, but not the aril, which is often eaten
   by children and by birds.


                         Family 2. =Pinoideæ.=

The four orders differ from one another partly in the arrangement of
the leaves (_Cupressaceæ_ have opposite or verticillately placed
leaves, flowers, and inflorescences; in the others they are placed
spirally), but chiefly in the greater or less degree of union which
takes place between the female flower (the leaf-like “symphyllodium”)
and its supporting cover-scale, and in the position of the ovules (the
micropyle being turned upwards or downwards). The “cone-scales” in
_Abietaceæ_ are formed by “symphyllodia” alone, in the others by
their union with the cover-scale.

Order 1. =Araucariaceæ.= This order most frequently has _solitary_
ovules, _turned downwards_ and attached _to the centre_ of the
cone-scales. In _Agathis_ (_Dammara_) the arrangement is the most
simple, a winged seed (Fig. 265), which hangs _freely_ downwards, being
borne in the centre of the undivided cone-scale. In _Araucaria_, the
stamens with the _free, pendulous_ pollen-sacs have been represented
in Fig. 242; the ovuliferous scale is united for nearly its whole
length with the bract, and projects from its apex in the shape of a
sheath-like, dentate scale, resembling the ligule in _Isoëtes_, and may
therefore be termed a “ligule.” _Araucaria_ (S. America, Australia) has
often rather broad leaves (_A. brasiliensis_). The ovuliferous scale in
_Cunninghamia_ is more distinct, and stretches transversely over the
entire cover-scale; it bears three inverted ovules (Fig. 266) (Eastern
Asia).

  [Illustration: FIG. 265.--_Agathis (Dammara) australis._
  Cone-scale with the seed. _A_ Longitudinal section; _A’_ from
  within; _fv_, _fv’_ vascular bundles; _v_ wing.]

  [Illustration: FIG. 266.--_Cunninghamia sinensis._ Cone-scale
  with three ovules, interior view: _d_ cover-scale; _f_
  ovuliferous scale.]

  [Illustration: FIG. 267.--_A-G Pseudotsuga douglasii_: _A_
  cone, _B_ cone-scale, with the inner side turned forward; the
  points of the cover-scale are seen behind it; _C-G_ transitions
  from the acicular leaf to the cover scale, from the base of a
  ♀ cone. _H Pinus montana._ Young ovuliferous scale, with the
  inner side turned forward; the ovules are now in the stage for
  pollination. _J-M Abies alba_: _J_ male cone; _b_ bud-scale;
  _a_ anthers; _K L M_ individual anthers.--_Pinus montana_: _N_
  pollen-grain; the two lateral expansions are the air-bladders; in
  the upper part of the interior of the grain a vegetative cell may
  be seen, and in the centre the large cell-nucleus.]

   Dammara-resin, which is used for varnish, is obtained from
   _Agathis_ (_Dammara_) species (New Zealand, Philippine
   Islands).

Order 2. =Abietaceæ (Pine and Fir Trees).= The leaves are spirally
arranged and needle-like. The flowers are _monœcious_. The male flowers
are long, and catkin-like, with numerous stamens, each bearing two
_oblong pollen-sacs_. The pollen-grains are most frequently tri-lobed,
having two bladder-like appendages, formed as outgrowths of the
exospore, to assist in their distribution by the wind (Fig. 267 _N_).
The bracts are arranged spirally. The union between the bract and the
ovuliferous scale, which is found in the preceding order, is not in
this instance so complete; these scales make their appearance as two
free parts, and are attached only at their bases (Fig. 268); the lower
portion, that is the cover-scale, in most instances remains quite
small (Fir, Red Pine, and others), it is only in the “Noble Pine”
(_Abies_) and _Pseudotsuga douglasii_, that it attains a greater length
than the ovuliferous scale (Fig. 267, _B-G_). On the other hand the
upper part, _the ovuliferous scale_ (the vascular bundles of which have
the bast turned upwards), grows strongly and elongates, especially
after fertilisation, becoming woody or leathery; it is commonly termed
the “_cone-scale_,” but is in reality only homologous with a part of
the “cone-scale” in the other order of Pinoideæ. On the side of the
ovuliferous scale, turned towards the axis, are situated _two ovules_
with micropyles _directed inwards_. The seeds are most frequently
provided with _a false wing_ (a tissue-like part of the surface of
the ovuliferous scale). Cotyledons, _more than_ 2, _verticillate_.
_Fertilisation does not take place until some time after pollination._
In _Pinus_, for instance, the pollen-tube only penetrates the nucellus
for a short distance during the year of pollination, and then ceases
its further growth, fertilisation not taking place until after the
middle of the next year; whilst the seeds ripen about a year and a half
after pollination. In the Larch and others, the seeds are mature in the
autumn succeeding pollination.

  [Illustration: FIG. 268.--_A Abies_: _c_ the cover-scale;
  _s_ ovuliferous scale, or “cone-scale”; _sk_ ovules in a young
  condition. _B Pinus_: ovuliferous scale with two ovules (_s_);
  _m_ the two-lobed micropyle; _c_ “mucro”; _b_ the cover-scale
  behind. _C Abies_: ripe “cone-scale” with two seeds (_sa_); _f_
  wing of seed.]

_Abies_ (Fir). The leaves are often (_e.g. Ab. pectinata_) displaced
into 2 rows, flat and indented at the apex, with 2 white (wax-covered)
lines on the under surface, in which the stomata are situated. The
leaf-scars are nearly circular and do not project. The cones are erect.
_The cover-scales and the ovuliferous scales separate from the axis_,
to which they remain attached in other genera.--~_Tsuga_ has leaves
like _Abies_, but by the slightly projecting leaf-scars, and cones with
persistent scales, it forms the transition to _Picea_.--_Pseudotsuga_
has leaves similar to those of _Abies_ and persistent carpels as in
_Picea_, but the cover-scales grow as in _Abies_ and project beyond
the ovuliferous scales (_P. douglasii_, Fig. 267). These two genera
are considered as sub-genera of _Abies_.~--_Picea_. The leaves project
on all sides, square and pointed; the leaf-scars are rhombic, on
projecting leaf-cushions. The cones are pendulous. The cover-scales are
much shorter than the leathery, persisting ovuliferous scales.--The
genus _Larix_ (Larch) differs from all the others in having deciduous
leaves (the three preceding have leaves which persist for eleven to
twelve years). It has _long-branches_ with linear foliage-leaves and
short, thick, _perennial dwarf-branches_, which each year form a new
rosette of foliage-leaves, similar to those on the long-branches. The
male flowers and the erect cones resemble those of _Picea_, and are
borne on dwarf-branches.--_Cedrus_ (Cedar) resembles _Larix_ to some
extent, but has persistent leaves (_C. libani_, _C. deodara_).--_Pinus_
(Pine) has long-branches and dwarf-branches. The leaves of the
long-branches are scale-like and not green; the dwarf-branches have
very limited growth, and persist for three years; they arise in the
axils of the scales borne on the long-branches of the self-same year,
and each bears 2–5 foliage-leaves, they are also surrounded at the base
by a number of membranous bud-scales. The cone-scales have a _thick,
rhomboid extremity_ (the “shield”).

   The buds which develope into long-branches arise at the apex of
   other long-branches, and being very close together, form false
   whorls. The female cones occupy the position of long-branches,
   and take about two years for their development. The male flowers
   arise close together, and form a spike-like inflorescence at
   the base of a long-branch of the same year. The male flowers
   occupy the position of dwarf-branches, so that a female cone
   may be considered to be a modified long-branch, and a male cone
   a modified dwarf-branch. The main axis of the seedling has
   needle-like leaves, similar to those found on the older parts,
   and on dwarf-branches; it is not until some time later that
   the dwarf-branches are developed and the permanent arrangement
   attained.

   USES. Several species are commonly cultivated in this country,
   partly on heaths and moors, and partly in plantations and as
   ornamental trees, such as Mountain Pine (_Pinus montana_, Cen.
   Eur.); Austrian Pine (_P. laricio_, Eur.); Scotch Fir (_P.
   silvestris_, Eur.); Weymouth Pine (_P. strobus_, N. Am.); common
   Red Pine (_Picea excelsa_, Cen. and N. Eur.); White Pine (_P.
   alba_, N. Am.); _Abies pectinata_ (Common Fir, S. and Cen. Eur);
   _A. nordmanniana_ (Crimea, Caucasus); _A. balsamea_ (N. Am.);
   _Tsuga canadensis_ (N. Am.); _Pseudotsuga douglasii_ (N.W. Am.);
   Larch (_Larix europæa_, Alps, Carpathians); _L. sibirica_ (N.E.
   Russia, Siberia).--The wood of many species, especially Pine,
   on account of its lightness and because it is so easily worked,
   is very well adapted for many useful purposes. The wood of the
   Yew-tree is very hard and is used for ornamental turning. Resin
   and Turpentine (_i.e._ Resin with essential oils, the name being
   derived from the Terebinth-tree, from which formerly a similar
   material was obtained) are extracted from _Pinus laricio_ and
   _P. pinaster_. Oil of Turpentine is obtained by distillation of
   turpentine with water; Tar by dry distillation of Pine-wood.
   Canada-balsam is from North American _Abies_-species (_A.
   balsamea_ and _Fraseri_). The officinal Turpentine is mainly
   obtained from _Pinus pinaster_ (South of France), _P. tæda_,
   _australis_, _strobus_ (Weymouth Pine) and other North American
   species; more recently also from _P. silvestris_ (Scotch Fir),
   _maritima_, _laricio_, _Picea excelsa_, and others; Venetian
   Turpentine, from Larch (S. Eur.) Amber is resin from a Tertiary
   plant (_Pityoxylon succiniferum_), closely related to the Pine,
   which grew especially in the countries round the South-East
   coast of the Baltic. _Pinus pinea_ (the Pine, S. Eur.) has
   edible seeds and also _P. cembra_ (in Cen. Eur. and Siberia).

Order 3. =Taxodiaceæ.= The vegetative leaves and cone-scales are
arranged spirally. The ovules (2–9) are situated either at the base
of the ovuliferous scales, in which case they are erect; or at their
centre, when they are generally more or less inverted. The ovuliferous
scale is more or less united with the cover-scale, and projects
beyond the surface of the cone-scale, like a comb (Fig. 269). The
vascular bundles, which extend into the cover-scale, have the usual
leaf-arrangement, viz. the wood placed above the bast; while those
bundles which enter the ovuliferous scale have this arrangement of the
bundles reversed.

  [Illustration: FIG. 269.--_Cryptomeria japonica._ Portion of
  longitudinal section through female flower. _d_ cover-scale;
  _f_ ovuliferous scale; _ov_ ovules; _fv_ and _fv’_ vascular
  bundles; the xylem is indicated by a wavy line, and the phlœm by
  a straight line.]

   _Taxodium distichum_ (the North American “Swamp Cypress”) has
   annual dwarf-branches, with distichous leaves, and cone-like
   “pneumathodia.” In the Tertiary period it was very common in
   the Polar regions. _Sequoia (Wellingtonia) gigantea_ is the
   famous Californian Giant-Fir, or Mammoth-Tree, which attains
   a height of 300 feet, a diameter of 36 feet, and is said to
   live for 1,500 years. _Cryptomeria japonica_ (Japan, China) has
   the least adnate ovuliferous scales; _Glyptostrobus_ (China);
   _Arthrotaxis_ (Tasmania); _Sciadopitys verticillata_ (the only
   species in Japan) has, like _Pinus_, scale-like leaves on
   the long-branches, of which those which are situated at the
   apex of the annual shoots support “double needles,” _i.e._
   _dwarf-branches_ similar to the two-leaved dwarf-branches in
   _Pinus_, but without bud-scales, and with the two leaves fused
   together at the edges into one needle, which turns its upper
   surface away from the long-branch.

Order 4. =Cupressaceæ= (=Cypresses=). _The leaves are opposite or
verticillate_, sometimes acicular, but most frequently scale-like
(Fig. 270). In the species with scale-like leaves, the seedlings
often commence with acicular leaves (Fig. 272), and branches are
sometimes found on the older plants which revert to this form, seeming
to indicate that the acicular leaf was the original form (atavism).
The so-called “_Retinospora_” species are seedling-forms of _Biota_,
_Thuja_, _Chamæcyparis_, which have been propagated by cuttings, and
retain the seedling-form. The flowers are monœcious or diœcious. The
male flowers are short, and have shield-like stamens, bearing most
frequently several pollen-sacs. The cover-scales and ovuliferous scales
are entirely fused together and form _undivided_ cone-scales, _opposite
or whorled_; _the ovuliferous scales_ have slight projections near _the
base_ on which 1–2–several _erect ovules_ are developed (Fig. 274).
Most frequently 2 cotyledons.--_Evergreen_ trees and shrubs.

  [Illustration: FIG. 270.--_Cupressus goveniana._]

  [Illustration: FIG. 271.--Portion of a branch of _Thuja
  orientalis_ (magnified). The leaf at the base on the right has a
  branch in its axil.]

  [Illustration: FIG. 272.--Seedling of _Thuja occidentalis_. The
  branch (_g_) is borne in the axil of the leaf _s_.]

_Juniperus_ (Juniper). _Diœcious._ The cone-scales become fleshy and
fuse together to form most frequently a 1–3 seeded “berry-cone.”
~_J. communis_ (Common Juniper) has acicular leaves, borne in whorls
of three, and the “berry-cone” is formed by a trimerous whorl
of cone-scales (Fig. 273). _J. sabina_ and _J. virginiana_ have
“berry-cones” formed from several dimerous whorls of cone-scales; the
leaves are connate and opposite, needle-and scale-like leaves are found
on the same plant.~

_Cupressus_ (Cypress). _Monœcious._ The cones are spherical; the
cone-scales shield-like, generally five-cornered and woody (Fig. 270),
each having many seeds. The leaves are scale-like.--_Thuja. Monœcious._
Cones oblong. The cone-scales are dry, as in the Cypress, but leathery
and imbricate, and not shield-like; each cone-scale bears 2–3 seeds.
The leaves are most frequently dimorphic; those leaves which are
situated on the edges of the flat branches are compressed, and only
these bear buds, which are developed with great regularity, generally
alternately, on both sides of the branch; those which are situated
on the flattened surfaces are pressed flat and broad, and never bear
branches (Fig. 271). Along the central line of each leaf there is a
resin-canal (Fig. 271).--~_Chamæcyparis_, _Callitris_, _Libocedrus_,
_Thujopsis_ (1 species: _T. dolabrata_; in Japan).~

  [Illustration: FIG. 273.--Branch of Juniper with “berry-cones.”]

  [Illustration: FIG. 274.--_Cupressus lawsoniana._ Longitudinal
  section through female cone. Two ovules (_ov_) are bisected; _f_
  ovuliferous scales.]

   OFFICINAL. _Juniperus sabina_ from Central and South of Europe
   (the young branches yield an essential oil). The wood of _J.
   communis_ is used in the production of an essential oil, and
   _J. oxycedrus_ in the production of empyreumatic oil. The
   “berry-cone” of _J. communis_ is officinal, and is also used
   for gin.--The wood of _J. virginiana_ (N. Am.) is known as red
   cedar, and is used for lead-pencils. Sandarack resin is obtained
   from _Callitris quadrivalvis_ (N.W. Africa).

   THE FOLLOWING ARE CULTIVATED IN GARDENS:--_Thuja occidentalis_
   (Arbor vitæ) (N. Am.), and _orientalis_ (China, Japan);
   _Juniperus sabina_ and _virginiana_; _Thujopsis dolabrata_
   (Japan); _Cupressus lawsoniana_ (California), _C. sempervirens_
   (S. Eur., W. Asia), and other species, are grown especially
   in conservatories, and in Southern Europe particularly in
   cemeteries.--The _Retinospora_ species which are so often
   planted, do not belong to an independent genus, but are obtained
   from cuttings, taken from seedling-plants with acicular leaves
   (see page 267).


                         Class III. =Gneteæ.=

This class, independent of extinct forms, comprises the most highly
developed of the Gymnosperms, partly from the circumstance that a
perianth of 2–4 members encloses the _terminally placed ovule_, which
is provided with one, or (in _Gnetum_) two, integuments, and partly
owing to the fact that the wood has true vessels. There is only one
order.

  [Illustration: FIG. 275.--_Welwitschia mirabilis_ (considerably
  reduced). The horizontal lines indicate the surface of the soil.]

   Order. =Gnetaceæ.= The three known genera differ very much in
   appearance. _Welwitschia mirabilis_ (from the deserts of South
   Western Africa) is the oldest (?) genus now living. It resembles
   a giant radish, in that the hypocotyl is the only part of the
   main axis of the stem which becomes developed. It attains a
   circumference of upwards of four metres with a length of 1/2½-⅔
   of a metre. It bears _only_ two oblong, leathery leaves (Fig.
   275) which are torn into segments at the apex and lie on the
   surface of the soil; these are the two first foliage-leaves
   which succeed the cotyledons, and they are remarkable for
   their enormous length (upwards of two metres) as well as for
   their long duration, living as long as the plant itself. In
   their axils are situated the 4-rowed, spike-like male and
   scarlet-coloured female cones, upon dichotomous branches. The
   perianth consists in the ♂ of 2 alternating pairs of leaves,
   the inner ones of which are slightly united. The andrœcium
   likewise consists of 2 whorls: the external (transverse) with
   2, the internal with 4 stamens; the lower halves of the 6
   filaments uniting to form a cup. Each of the terminal anthers
   corresponds to a sorus of 3 sporangia, the sporangia being fused
   together, and opening at the top by _one_ three-rayed cleft.
   In the centre of the ♂-flower there is a sterile ovule. In the
   ♀-flower a perianth of two connate leaves is present.--_Ephedra_
   (desert plants, especially in the Mediterranean and W. Asia)
   at first sight resembles an _Equisetum_; the stems are thin,
   long-jointed, and the leaves opposite, small, and united into
   a bidentate sheath; ♂-perianth of two connate leaves (median
   leaves); 2–8 stamens united into a column. Each anther is formed
   of 2 sporangia (is bilocular). ♀ mainly, as in _Welwitschia_.
   The seeds are surrounded by the perianth which finally becomes
   red and fleshy. There are 30 species.--_Gnetum_ has opposite,
   lanceolate, pinnately-veined, leathery leaves. They are mostly
   climbers (Lianas) from Tropical Asia and America. The ♂-flowers
   have a tubular perianth, (formed from two median leaves) which
   surrounds a centrally-placed filament, bearing 2 anthers. In
   the ♀-flower there is a similar perianth, surrounding an ovule
   provided with 2 integuments. The perianth becomes fleshy and
   envelops the hard seed. 20 species.

   From the circumstance of _Welwitschia_ having ♂ flowers
   which, besides stamens, possess also a rudiment of an ovule,
   Celakovsky draws the inference that the earliest Gymnosperms
   had hermaphrodite flowers which from this structure became
   differentiated entirely into ♂-and ♀-flowers, with the exception
   of _Welwitschia_ only, in which this differentiation was only
   carried out in the ♀-flower. This theory has so far been
   scarcely proved.


                          =Fossil Gymnosperms.=

   The earliest continental plants which are known belong to the
   CORDAITACEÆ, a group of plants which existed as early as the
   Silurian period; they were Gymnosperms, but it has not yet been
   determined whether they were Cycads or Conifers. The CYCADS,
   even in the Coal period, were scarce; they attained their
   fullest development in Jurassic and Cretaceous periods, during
   which they were rich in species and genera, and extended as far
   as the Polar regions. In addition to these, Taxaceæ, Abietaceæ,
   and Taxodiaceæ appeared in the Carboniferous period. The TAXACEÆ
   appear to have attained their culmination in the Jurassic and
   Cretaceous periods; _Ginkgo_ appears in the Rhætic; _Torreya_,
   in the Cretaceous; _Taxus_ and _Podocarpus_ in the Tertiary
   periods. The ABIETACEÆ also appear in the Carboniferous;
   _Pinus_ was first known with certainty in the English Weald
   and in the Cretaceous; almost all other contemporary genera
   are represented in this latter period. The ARAUCARIACEÆ first
   appear, with certainty, in the Jurassic. The TAXODIACEÆ may
   be traced back as far as the Carboniferous (?); _Sequoia_ is
   first found in the lowest Cretaceous, at that period it spread
   throughout the entire Arctic zone, and being represented by a
   large number of species, formed an essential part of the forest
   vegetation. _Sequoia_ played a similar part in the Tertiary
   period. The CUPRESSACEÆ are first known with certainty in the
   Jurassic, but they appeared more frequently and numerously in
   the Tertiary period, in which most of the present living genera
   were to be found. The GNETACEÆ, according to a theory advanced
   by Renault were represented in the Coal period by the genus
   _Stephanospermum_, which had four ovules enclosed by an envelope.



                              DIVISION V.

                             ANGIOSPERMÆ.


See pages 3 and 224. To this Division belong the majority of the
Flowering-plants. They are divided into two parallel classes, the
Monocotyledons and the Dicotyledons, which differ from each other not
only in the number of cotyledons, which, with a few exceptions, is one
in the former, two in the latter, but also in the internal structure
of the stem, the venation of the leaves, the number of the parts of
the flower, etc. ~Assuming that these two classes have sprang from a
common origin, it is amongst the Helobieæ in the first, and amongst the
Polycarpicæ in the second class that we might expect to find closely
allied forms, which might reasonably be supposed to have varied less
from this original type. As for the rest, they seem to stand quite
parallel, without exhibiting any close relationship. It is scarcely
proved that the Monocotyledons are the older class.~

[Our knowledge of the forms included under the Angiosperms has
recently been considerably increased by Treub (_Ann. d. Jar. Bot. d.
Buitenzorg_, 1891), who has shown that the Casuarinas differ in many
important points from the typical Angiosperms. Among other characters
the pollen-tube is found to enter the ovule near the chalaza and
therefore at the opposite end to the micropyle, and Treub therefore
suggests that these plants should be placed in a subdivision termed
Chalazogams.

According to this view the principal divisions of the Angiosperms would
be represented thus:--

                =Angiospermæ.=

    Sub-division.             Sub-division.
    CHALAZOGAMES.             POROGAMES.

      Class.                    Classes.
    Chalazogames.       Monocotyledones, Dicotyledones.

More recently Nawaschin (_Bull. Acad. Imp. Sci. St. Petersb._, ser.
iii., xxxv.) has shown that _Betula_, and Miss Benson (_Trans. Linn.
Soc._, 1894) that _Alnus_, _Corylus_, and _Carpinus_ also belong to the
Chalazogams.

Our knowledge, however, is still so incomplete that one would hesitate
to accord the full systematic value which Dr. Treub attaches to his
discovery until the limits of the Chalazogamic group are better
defined; and it would hardly be justifiable to include the Casuarinas
and the above-noted genera in one family.]


                      Class 1. =Monocotyledones.=

_The embryo has only one cotyledon; the leaves are as a rule scattered,
with parallel venation; the vascular bundles of the stem are closed,
there is no increase of thickness. The flower is typically constructed
of five 3-merous whorls, placed alternately._

THE EMBRYO is generally small in proportion to the abundant endosperm
(exceptions, see _Helobieæ_), and its single cotyledon is often
sheath-like, and very large. On the germination of the seed either the
entire cotyledon, or its apex only, most generally remains in the seed
and absorbs the nutritive-tissue, while the lower portion elongates
and pushes out the plumule and radicle, which then proceed with their
further growth. The primary root in most cases soon ceases to grow,
but at the same time, however, numerous lateral roots break out from
the stem, and become as vigorous as the primary root, or even more so.
Increase in thickness does not take place in these roots; they branch
very little or not at all, and generally die after a longer or shorter
time.

THE STEM is frequently a corm, bulb, or other variety of underground
stem, as the majority of the Monocotyledons are perennial, herbaceous
plants; it has scattered, closed vascular bundles (Fig. 276), and no
cambium by which a continuous thickening may take place. The stem of
the Palms, however, attains a very considerable thickness, which is due
to the meristem of its growing-point continually increasing in diameter
for a lengthened period (often for many years), until it has reached a
certain size. In this condition the growing-point has the form of an
inverted cone, and it is only when this cone has attained its requisite
size that the formation of a vertical cylindrical stem commences.
Certain tree-like Liliaceæ, as _Dracæna_, _Aloe_, etc., have a
continuous increase in thickness; this is due to a meristematic layer,
which arises in the cortex, outside the original vascular bundles,
which were formed at the growing-point of the stem. This meristem
continues to form thick-walled parenchyma and new, scattered vascular
bundles. The primary vascular bundles, in the Palms and others, run
in a curved line from their entrance into the stem at the base of
the leaf, towards the centre of the stem, and then bend outwards and
proceed downwards in a direction more parallel to the sides of the stem
(Fig. 277). The bundles formed later, in those stems which increase in
thickness, are not continued into the leaves.

THE BRANCHING as a rule is very slight, the axillary buds of the
majority of the leaves never attaining development, _e.g._ in the
Palms, bulbous plants and others. As the cotyledon arises singly,
the succeeding leaves also must be scattered, but they are frequently
arranged in two rows (Grasses, Iris, etc). _The first leaf borne on a
branch_ (the “Fore-leaf,”[24]--the bracteole, if on a floral shoot)
has generally, in the Monocotyledons, a characteristic form and
position, being situated on the posterior side of its own shoot, and
hence turned towards the main axis; it is sometimes provided with two
laterally-placed keels (Figs. 279 _f_, 290 _øi_), but the midrib is
often absent. It arises in some cases from two primordia, which at the
beginning are quite distinct, and thus has been regarded as formed by
two leaves. It is, however, only one leaf, a fact which is evident from
several circumstances, one being that it never supports more than one
shoot, and this stands in the median plane (Fig. 279).

  [Illustration: FIG. 276.--Transverse section of the stem of a
  Palm: _v v_ is the wood portion, _b b_ the bast portion of
  the vascular bundled.]

  [Illustration: FIG. 277.--Diagrammatic representation of the
  course of the vascular bundles, from the stem into the leaves in
  a Monocotyledon.]

THE LEAVES are _amplexicaul_, and have a large sheath but no stipules;
the blade is most frequently long, ligulate, or linear, entire, with
parallel venation, the veins being straight or curved (Figs. 300, 309).
Connecting the large number of veins which run longitudinally, there
are as a rule only weak transverse ones. It is very rarely that other
forms of leaves are found, such as cordate (Figs. 302, 312), or that
the blade is branched, or the venation is, for example, pinnate or
palmate (Figs. 225, 298); these deviations are especially found in the
Araceæ, the Palms, the Scitamineæ (Fig. 308), the Dioscoreaceæ, and in
several aquatic plants. The incisions in the Palm-leaf are derived by
the splitting of an originally entire leaf.

THE STRUCTURE OF THE FLOWER is generally as follows: Pr3 + 3, A3 + 3,
G3, rarely S3 + P3 with the other members unchanged.[25] Instead of 3,
the numbers 2 and 4 may occur; rarely others. In all these instances
there are 5 whorls, which regularly alternate with one another, most
frequently in the 3-merous flower, as in the diagram (Fig. 278). This
diagram is found in the following orders: Liliaceæ, Convallariaceæ,
Juncaceæ, Bromeliaceæ, Amaryllidaceæ, Dioscoreaceæ, Palmæ, some
Araceæ, and in some small orders, and may be considered as the typical
structure and also the starting point for the exceptional orders. The
ovary in many Monocotyledons has many ovules, and the fruit becomes
a many-seeded berry or capsule; this form is no doubt the oldest. In
others the number of seeds becomes reduced to 1, and the fruit then
becomes a cypsela, or a drupe (_e.g. Gramineæ_, _Cyperaceæ_, _Palmæ_,
etc).

  [Illustration: FIG. 278.--Diagram of the ordinary, regular flower
  in the Monocotyledons: _s_ is the bract.]

  [Illustration: FIG. 279.--Diagram of _Iris_: _f_ the bracteole;
  in its axil is a shoot with its bracteole.]

  [Illustration: FIG. 280.--Diagram of _Orchis_: _l_ the lip; σ σ
  the two staminodes.]

Deviations from this typical floral structure in some instances may
be traced to _suppression_, very rarely to a _splitting_ of certain
members, the typical relative positions not being changed. Thus,
the Iridaceæ, the Cyperaceæ, most of the Gramineæ and some Juncaceæ
deviate in having only 3 stamens (Fig. 279), the inner whorl (indicated
by *) not becoming developed. The Musaceæ differ in the posterior
stamen not being developed; _Zingiberaceæ_ (Fig. 314), _Marantaceæ_,
and _Cannaceæ_, in the fact that only 1 of all the stamens bears an
anther, and the others are either suppressed or developed into petaloid
staminodes, with some perhaps cleft in addition. The Orchideæ deviate
in having, generally, only the anterior stamen of all the 6 developed
(Fig. 280). In this, as in other instances, the suppression of certain
parts of the flower is often connected with _zygomorphy_ (_i.e._
symmetry in _one_ plane), chiefly in the inner perianth-whorl, but also
in the other whorls. In the Orchids, the perianth-leaf (the labellum,
Fig. 280 _l_) which is directly opposite the fertile stamen, is larger
and altogether different from the others. The perianth-leaves may also
be suppressed; see, for example, the two diagrams of the Cyperaceæ
(Fig. 284). In some orders the suppression of these leaves, which form
the basis of the diagram, is so complete that it is hard to reduce the
actual structure of the flower to the theoretical type, _e.g._ the
Grasses (Fig. 290) and _Lemna_ (Fig. 303). In the first family, which
especially comprises water-plants, a somewhat different structure is
found; thus Fig. 282 differs somewhat from the ordinary type, and other
flowers much more so; but the floral diagrams which occur in this
family may perhaps be considered as the most probable representatives
of an older type, from which the ordinary pentacyclic forms have taken
their origin. In favour of this theory we have the larger number of
whorls, the spiral arrangement of some of these in the flower, with
a large and indefinite number of stamens and carpels, the perfectly
apocarpous gynœceum which sometimes occurs, etc., etc.

   The Monocotyledons are divided into 7 Families:--

   1. HELOBIEÆ. This family forms a group complete in itself. It
   commences with hypogynous, perfect flowers, whose gynœcium is
   apocarpous and terminates in epigynous and more or less reduced
   forms.

   2. GLUMIFLORÆ. These have as a starting point the same diagram
   as the following families, but otherwise develope independently.

   3. SPADICIFLORÆ. Also an independent branch, or perhaps two
   different ones which terminate in much reduced forms.

   4. ENANTIOBLASTÆ. These ought perhaps to be amalgamated with the
   following family.

   5. LILIIFLORÆ. These advance from forms with the typical diagram
   and hypogynous flower, to epigynous and reduced forms.

   6. SCITAMINEÆ and

   7. GYNANDRÆ. Two isolated families, which probably have taken
   their origin from Liliifloræ, and have epigynous, mostly
   zygomorphic, and much reduced forms.


                         Family 1. =Helobieæ.=

To this family belong _only water- or marsh-plants_; _the endosperm is
wanting_, and they possess an embryo with a very _large hypocotyl_
prolonged downwards and often club-like. The perianth is often
differentiated into calyx and corolla; the flower is regular, and in
the first orders to be considered, may be reduced to the ordinary
Monocotyledonous type; there are, however, _usually found two_
3-_merous whorls of carpels_ (Fig. 282), and thus in all 6 whorls, or
again, the _number of carpels may be indefinite_; the number of stamens
also may be increased, either by the division of the members of a
whorl, or by the development of additional whorls. _Syncarps_,[26] with
nut or follicular fruitlets, are _very common_, for example, in the
first orders; in the last (Hydrocharitaceæ) the carpels are not only
united, but the ovary is even inferior.

   The primitive type appears to be a hypogynous flower, similar
   to that of the Juncaginaceæ or Alismaceæ, with several 3-merous
   whorls, and free carpels, each with many ovules; the green
   perianth in this instance being no doubt older than the coloured
   ones. If we take a flower with this structure as the starting
   point, then the family developes partly into epigynous forms,
   partly into others which are so strongly reduced and exceptional
   that it is scarcely possible to refer them to the ordinary
   type. The family, through the peculiar _Zostereæ_, appears to
   approach the Araceæ, in which _Potamogetonaceæ_ and _Najadaceæ_
   are included by some authorities. However, the inclusion of
   _Potamogeton_, and with it _Ruppia_ and _Zannichellia_, in the
   Juncaginaceæ appears quite correct. It would scarcely be right
   to separate _Zostereæ_ from these. Great stress has often been
   laid upon the similarity with the Ranunculaceæ which is found
   in the Alismaceæ, but it is scarcely more than an analogous
   resemblance.

Order 1. =Juncaginaceæ.= The ☿, regular, _hypogynous_ flowers have
the _perianth_ 3 + 3, _sepaloid_, stamens 3 + 3 (with extrorse
anthers), and carpels 3 + 3 (free or united), of which last, however,
one whorl may be suppressed (in _Triglochin maritima_ all 6 carpels
are developed, in _T. palustris_ the inner whorl is unfertile).
Inflorescence long spikes. Embryo _straight_.--Marsh-plants with
radical, rush-like leaves, arranged in two rows, and often sheathing
and ligulate (“squamulæ intravaginales”); the inflorescence is a spike
or raceme.--_Scheuchzeria._ Carpels almost free; in each at least two
ovules. Follicles.--_Triglochin_ has long, fine racemes without bracts
or bracteoles; one ovule in each carpel. The carpels in the two native
species are united, but separate when ripe as a schizocarp, loosening
from below; they open along the ventral suture or remain closed; a
linear central column remains. ~The most reduced is Lilæa (1–2 sp.
Am.)--Protogynous. About 10 species. Temp. Fossils in Tertiary.~

Order 2. =Potamogetonaceæ.= The aquatic plants belonging to this order
are perennial, living entirely submerged, or with floating leaves, and
preferring still water. The leaves are alternate, in some linear and
grass-like, in others there is an elliptical floating blade, supported
by a linear submerged petiole. Axillary scales. The fruit is generally
a syncarp with _nuts_ or _drupes_; the _embryo is curved_, of very
various forms.

_Potamogeton_ (Pond-weed). The rhizome is creeping, sympodial (with two
internodes in each shoot-generation); the inflorescence is a terminal,
many-flowered spike, without floral-leaves; below it are found 2
foliage-leaves placed nearly at the same height, from whose axils
the branching is continued cymosely. The flowers are ☿, 4-_merous_,
naked, and consist only of 4 _stamens_, with the _connectives, broadly
developed_ at the back of the anthers, _resembling a perianth_,
and of 4 _free, sessile carpels_. They are common plants in fresh
water. ~The spike, during the flowering, is raised above the water.
Wind-pollinated and protogynous.--Closely allied is _Ruppia_ (Tassel
Pond-weed), in salt or brackish water. The spike has only two naked
flowers, each consisting of 2 stamens and 4 carpels. The stalks of the
individual carpels are considerably prolonged.--_Zannichellia_ (Horned
Pond-weed) is monœcious; the ♀-flower consists of 4 (2–9) carpels, with
membranous, bell-shaped perianth; long styles; the ♂-flower has 1 (-2)
stamens. _Althenia._~

_Zostera_ (Grass-wrack) is an entirely submerged, marine plant
with creeping rhizome (with displacement of buds) and strap-shaped
leaves. The flowering shoots are sympodia with displacement of the
axes (Fig. 281). The inflorescence is a peculiar, flatly-compressed
spike, on _one_ side of which the flowers are borne (Fig. 281). ~This
inflorescence may be considered, no doubt correctly, to be derived
from the symmetrical spike of _Potamogeton_ by strongly dorsiventral
development, and by a strong suppression of the floral parts taking
place simultaneously. Two rows of flowers are developed, but of these
one is so pressed into the other that apparently only one is present.~
Each flower consists of only 1 stamen and 1 carpel situated at the same
height (Fig. 281); the unilocular ovary encloses 1 pendulous ovule
and bears a bifid style. As regards the perianth (?) one leaf may be
present (_Z. nana_, Fig. 281 _D_). The pollen-grains are filamentous.
Pollination takes place under water. ~_Posidonia_ and _Cymodocea_ are
allied to these. About 70 species.~

   [Illustration: FIG. 281.--_Zostera._ A Diagram of the
  branching of the floral shoots: _I_, _II_ ... are the successive
  shoot-generations, every other one being shaded; _g_{1}_
  _g_{2}_ ... fore-leaves; _sp_{1} sp_{2}_ ... spathes for the
  successive spikes. Each shoot is united for some distance with
  the parent axis (indicated by the half-shaded internodes). Each
  shoot commences with a fore-leaf turning towards the parent
  axis, _g_; succeeding this is the spathe, _sp_; and then the
  inflorescence. The fore-leaf supports a new lateral shoot.
  _B_ Diagram of a shoot, _II_, which is borne laterally in the
  axil of the fore-leaf _g_{1}_, on the shoot _I_, _g_{2}_ its
  fore-leaf; _sp_{2}_ its spathe; _sti_ squamulæ intravaginales.
  _II_ Is the spadix with stamens and carpels; _b_ a perianth-leaf
  (or connective expansion, similar to those which occur in
  _Potamogeton_). _C_ The upper portion of a young spadix with
  development of flowers. _D_ Part of a spadix with 2 flowers; the
  parts which theoretically belong to one another are connected by
  a dotted line.]

Order 3. =Aponogetonaceæ.= Aquatic plants with tuberous stem. They
have a single, petaloid perianth (3–2–1–leaved), most frequently 6
stamens and 3(-6) carpels. Straight embryo.--About 15 species (Africa,
Madagascar, Tropical Asia and Australia).--_Aponogeton distachyos_ and
_A._ (_Ouvirandra_) _fenestralis_ are grown in conservatories; the
latter has lattice-like, perforated leaves.

Order 4. =Najadaceæ.= Only one genus _Najas_ (about 10 species);
annual fresh water plants with leaves in pairs and solitary, unisexual
flowers. The ♂ flower is remarkable in having a terminal stamen, which
has either 4 longitudinal loculi or 1 central one; on this account the
stamen of _Najas_ is considered by some authorities to be a stem and
not a leaf-structure. The unilocular gynœceum and the single, erect,
anatropous ovule are also terminal. Pollination takes place under the
water.

Order 5. =Alismaceæ.= The regular, _hypogynous_ flowers are in some
species unisexual by the suppression of either andrœcium or gynœceum;
they have a 6-merous perianth, _generally_ differentiated into 3
sepals and 3 petals; generally 6 _stamens in the outer whorl_ (by the
division of the 3; Fig. 282) and often several 3-merous whorls inside
these, and 6–∞ _free_ carpels arranged cyclically or spirally. Fruit a
syncarp.--Marsh- or water-plants with radical leaves and long-stalked
inflorescences.

=A.= _Butomeæ. Follicles with many seeds, which are borne on
nearly the whole of the inner surface of the cyclic carpels_ (as in
Nymphæaceæ). Embryo _straight_.--_Butomus_ (Flowering Rush, Fig.
282), has an umbel (generally composed of 3 helicoid cymes). _S_
3, _P_ 3, stamens 9 (6 + 3, _i.e._ the outer whorl doubled), _G_ 3
+ 3. ~_B. umbellatus_; creeping rhizome with triangular Iris-like
leaves.--_Hydrocleis. Limnocharis._~

  [Illustration: FIG. 282.--Diagram of _Butomus_: _f_ bracteole.]

=B.= _Alismeæ._ Fruit achenes. Latex common (in the intercellular
spaces). The flowers are arranged most frequently in single or
compound whorls. Embryo _curved_, horse-shoe shaped.--_Alisma_ has
_S_ 3, _P_ 3, _A_ 6 (in 1 whorl, grouped in pairs, _i.e._ doubled in
front of the sepals), and 1 _whorl_ of 1-seeded achenes on a flat
receptacle. The leaves are most frequently radicle, long-stalked;
the lamina have curved longitudinal veins, and a richly branched
venation. _A. plantago._--_Elisma_ (_E. natans_) has epitropous
(turned inwards) ovules, whilst the ovules of _Alisma_, _Sagittaria_
and others are apotropous (turned outwards).--_Echinodorus_ (_E.
ranunculoides_) has a convex receptacle, carpels many, united and
capitate. _Damasonium_.--_Sagittaria_ (Arrow-head) has _monœcious_
flowers, several whorls of stamens and _spirally-arranged achenes_ on
a very convex receptacle. ~_S. sagittifolia_ reproduces by tuberous
buds formed at the end of long, submerged branches. The leaves, in deep
and rapidly running water, are long and strap-shaped, but in the air
arrow-shaped.~

   Honey is secreted in the flower and pollination effected
   by insects. _Alisma plantago_ has 12 nectaries. The
   submerged flowers of _Elisma natans_ remain closed and are
   self-pollinated. _Butomus_ has protandrous flowers. There are
   about 50 species, which mostly grow outside the Tropics.--Uses
   insignificant. The rhizome of some is farinaceous.

Order 6. =Hydrocharitaceæ.= This order differs chiefly from the
preceding in its _epigynous_ flowers. These are in general unisexual
(_diœcious_), and surrounded by a 2-leaved or bipartite _spathe_; they
are 3-merous in all whorls, but the number of whorls is generally
greater than 5, sometimes even indefinite. The perianth is divided
into _calyx_ and _corolla_. The ovary is _unilocular_ with parietal
placentation, or more or less incompletely plurilocular. The fruit
is berry-like, but usually ruptures irregularly when ripe. Embryo
straight.--Most often submerged water-plants, leaves seldom floating on
the surface. Axillary scales (_squamulæ intravaginales_).

_Hydrocharis._ Floating water-plants with round cordate leaves; S3, P3
(folded in the bud); ♂-flowers: 3 (-more) flowers inside each spathe;
stamens 9–15, the most internal sterile. ♀-flowers solitary; three
staminodes; ovary 6-locular, with many ovules attached to the septa;
styles 6, short, bifid. [The petals of the ♀-flowers bear nectaries at
the base. In this and the following genus the pollination is without
doubt effected by insects.] ~_H. morsus ranæ_ (Frog-bit) has runners;
it hibernates by means of special winter-buds.~--_Stratiotes_; floating
plants with a rosette of linear, thick, stiff leaves with spiny margin,
springing from a short stem, from which numerous roots descend into
the mud. Inflorescence, perianth, and ovary nearly the same as in
_Hydrocharis_, but the ♂-flower has 12 stamens in 3 whorls, of which
the outer 6 are in 1 whorl (dédoublement), and inside the perianth in
both flowers there are numerous (15–30) nectaries (staminodes?). _S.
aloides_ (Water-soldier); in N. Eur. only ♀-plants.--~_Vallisneria
spiralis_ is a tropical or sub-tropical plant, growing gregariously
on the mud in fresh water. The leaves are grass-like, and the plants
diœcious; the ♂-flowers are detached from the plant, and rise to
the surface of the water, where they pollinate the ♀-flowers. These
are borne on long, spirally-twisted peduncles which contract after
pollination, so that the ♀-flower is again drawn under the water,
and the fruits ripen deeply submerged.--_Elodea canadensis_ is also
an entirely submerged plant. The leaves are arranged in whorls on a
well-developed stem. Only ♀-plants in Europe (introduced about 1836
from N. Am). This plant spreads with great rapidity throughout the
country, the reproduction being entirely vegetative. _Hydrilla_,
_Halophila_, _Thalassia_, _Enhalus_.--In many of these genera the
number of whorls in the flower is remarkably reduced; for example, in
_Vallisneria_, in the ♂-flowers to 2: Pr 3, A (1-) 3, in the ♀ to 3: Pr
3, Staminodes 3, G 3.--About 40 species; Temp. and Trop.~


                        Family 2. =Glumifloræ.=

The _hypogynous_ flowers in the Juncaceæ are completely developed on
the _pentacyclic, trimerous_ type, with _dry, scarious perianth_.
Even in these the interior whorl of stamens becomes suppressed, and
the ovary, which in _Juncus_ is trilocular with many ovules, becomes
in _Luzula_ almost unilocular, but still with 3 ovules. The perianth
in the Cyperaceæ and Gramineæ is reduced from hairs, in the first of
these, to nothing, the flowers at the same time collecting more closely
on the inflorescence (spike) supported by _dry_ bracts (_chaff_); the
number of stamens is almost constantly 3; stigmas linear; the ovary
has only 1 loculus with 1 ovule, and the fruit, which is a capsule in
the Juncaceæ, becomes a nut or caryopsis.--The endosperm is large and
floury, the embryo being placed at its lower extremity (Figs. 286 _B_,
291).--The plants belonging to this order, with the exception of a few
tropical species, are annual or perennial herbs. The stems above ground
are thin, and for the most part have long internodes, with linear,
parallel-veined leaves which have long _sheaths_, and often a _ligule_,
_i.e._ a membranous projection, arising transversely from the leaf at
the junction of the sheath and blade. The underground stems are short
or creeping rhizomes. The flowers are small and insignificant. Wind- or
self-pollination.

Order 1. =Juncaceæ= (=Rushes=). The regular, hermaphrodite, hypogynous
flowers have 3 + 3 brown, dry, free perianth-leaves projecting like
a star during the opening of the flower; stamens 3 + 3 (seldom 3 +
0) and 3 carpels united into one gynœceum (Fig. 283); the ovary is
3- or 1-locular; there is as a rule 1 style, which becomes divided
at the summit into 3 stigmas, often bearing branches twisted to the
right (Fig. 283). _Fruit a capsule_ with loculicidal dehiscence. The
embryo is an extremely small, ellipsoidal, cellular mass, without
differentiation into the external organs.

  [Illustration: FIG. 283.--Flower of _Luzula_.]

_Juncus_ (Rush) has glabrous foliage-leaves, generally cylindrical,
rarely flat; the edges of the leaf-sheath are free (“_open_”
leaf-sheaths) and cover one another. The capsule, 1- or 3-locular, with
_many_ seeds--_Luzula_ (Wood-Rush) has flat, grass-like leaves with
ciliated edges; the edges of the leaf-sheath are united (“_closed_”
leaf-sheath). The capsule unilocular and _3-seeded_.--_Prionium_: S.
Africa; resembling a _Tacona_.

   The _interior_ whorl of stamens, in some species, disappears
   partially or entirely (_J. supinus_, _capitatus_,
   _conglomerates_, etc.)

   Some of the numerous _Juncus_-species (_e.g. J. effusus_,
   _glaucus_, _conglomeratus_, etc.), have false, lateral
   inflorescences, the axis of the inflorescence being pushed
   to one side by its subtending leaf, which apparently forms
   a direct continuation of the stem, and resembles it both
   in external and internal structure. The foliage-leaves of
   this genus were formerly described as “unfertile stems,”
   because they are cylindrical, erect, and resemble stems, and
   consequently the stem was said to be “leafless”: _J. effusus_,
   _glaucus_, _conglomeratus_. Stellate parenchynatous cells are
   found in the pith of these stems and in the leaves. Other
   species have distinct terminal inflorescences and grooved
   leaves; _J. bufonius_ (Toad-rush), _compressus_, and others.
   The _inflorescences_ most often present the peculiarity of
   having the lateral axes protruding above the main axis.
   Their composition is as follows:--The flowers have either no
   bracteoles, and the inflorescences are then capitulate; or
   they have 1–several bracteoles. Each branch has then, first,
   a 2-keeled fore-leaf placed posteriorly (“basal-leaf”), and
   succeeding this are generally several leaves borne alternately
   and in the same plane as the basal-leaf, the two uppermost
   (the “spathe-leaves”) being always barren; those which lie
   between the basal-leaves and the spathe-leaves are termed
   “intermediate-leaves.” If only branches occur in the axils
   of the basal-leaves, then the succeeding branches are always
   borne on the posterior side of the axis, and form a fan[27];
   if the basal-leaf is barren, and if there is only one fertile
   intermediate-leaf, then the lateral axes are always on the upper
   side, and a sickle[27]-like inflorescence occurs; if there are 2
   fertile intermediate-leaves, then a dichasium is formed, and in
   the case of there being several, then a raceme, or spike.

   _Juncaceæ_ are, by several authors, classed among the
   Liliifloræ, but there are so many morphological and partly
   anatomical features agreeing with the two following orders, that
   they may, no doubt, most properly be regarded as the starting
   point of these, especially of the _Cyperaceæ_, which they
   resemble in the type of flowers, the inflorescence, the type of
   mechanical system, and the stomata.

   POLLINATION by means of the wind. Cross-pollination is
   often established by protogyny. _J. bufonius_ has partly
   triandrous and cleistogamic, partly hexandrous, open
   flowers.--DISTRIBUTION. The 200 species are spread over the
   entire globe, but especially in cold and temperate countries;
   they are seldom found in the Tropics.--USES. Very slight;
   plaiting, for instance.

Order 2. =Cyperaceæ.= The majority are _perennial_ (seldom annual)
_herbs_ living in damp situations, with a sympodial rhizome and
grass-like appearance. The stems are seldom hollow, or have swollen
nodes, but generally _triangular_, with the upper internode just below
the inflorescence generally very long. The leaves are often arranged
in 3 _rows_, the leaf-sheath is _closed_ (very seldom split), and the
ligule is absent or insignificant. The flowers are arranged in _spikes_
(_spikelets_) which may be united into other forms of inflorescences
(chiefly spikes or racemes). The flowers are supported by a bract,
but have _no bracteoles_. In some genera the perianth is distinctly
represented by six bristles corresponding to six leaves (Figs. 284
_A_, 286 _A_); in others it is represented by an indefinite number of
hairs (Fig. 284 _B_), and very frequently it is altogether wanting.
_The inner whorl of stamens is absent_, and the flower has therefore
3 stamens (rarely more or less than 3), the anthers _are attached by
their bases to the filament_ (innate) and are not bifid (Figs. 286).
Gynœceum simple, formed of 3 or 2 carpels; 1 style, which is divided
at the extremity, as in the Juncaceæ, into 3 or 2 arms; the single
loculus of the ovary contains one basal, erect, anatropous ovule; the
stigmas are not feather-like. _Fruit a nut_, whose seed is generally
not united with the pericarp. The embryo is small, and lies at the
_base of the seed in the central line_, surrounded on the inner side by
the endosperm (Fig. 286 _B_). On germination the cotyledon _does not
remain_ in the seed.

  [Illustration: FIG. 284.--Diagram of structure of: _A Scirpus
  silvaticus_; _B Eriophorum angustifolium_.]

   A regular perianth, with 6 scale-like perianth-leaves in 2
   whorls, is found in _Oreobolus_. In _Scirpus littoralis_ the
   perianth-leaves are spreading at the apex, and divided pinnately.

   The branching of the inflorescence is often the same as in the
   Juncaceæ, and supports the theory that these two orders are
   related. In _Rhynchospora_ and others, the “spikelets” are
   really only “spike-like” and to some extent compound.

=A.= SCIRPEÆ. HERMAPHRODITE FLOWERS.

1. Spikelets cylindrical, the bracts arranged spirally (in many
rows). The lower ones are often barren, each of the others supports
a flower.--_Scirpus_ (Club-rush). The spikelets are many-flowered;
the perianth is bristle-like or absent, and does not continue to grow
during the ripening of the fruit (Fig. 286 _A_). Closely allied to this
is _Heleocharis_, with terminal spikes.--_Eriophorum_ (Cotton-grass)
differs chiefly in having the perianth-hairs prolonged, and forming a
bunch of white, woolly hairs (Fig. 284 _B_).

   _Cladium_ and _Rhynchospora_ (Beak-rush) differs especially in
   the _few_-flowered, compound spikelets which are collected into
   small bunches; the latter has received its name from the fact
   that the lowermost portion of the style remains attached to the
   fruit as a beak.

2. Spikelets compressed, the bracts arranged only in _two rows_; the
other characters as in the first-mentioned. _Cyperus_ (spikelets
many-flowered); _Schœnus_ (Bog-rush); spikelets few-flowered; _S.
nigricans_ has an open sheath.

  [Illustration: FIG. 285.--_Carex_: _A_ diagram of a male flower;
  _B_ of a female flower with 3 stigmas; _C_ of a female flower
  with 2 stigmas; _D_ diagrammatic figure of a female flower; _E_
  similar one of the androgynous (false) spikelet of _Elyna_. The ♂
  is here represented placed laterally; it is terminal, according
  to Pax.]

  [Illustration: FIG. 286.--_A_ Flower of _Scirpus lacustris_. _B_
  Seed of _Carex_ in longitudinal section.]

=B.= CARICEÆ. UNISEXUAL FLOWERS.

In the ♂-flowers there is no trace of a carpel, and in the ♀ no trace
of a stamen. Floral-leaves in many rows. In some (_Scleria_, certain
_Carex_-species), ♂-and ♀-flowers are borne in the same spikelet, the
latter at the base or the reverse; in the majority each spikelet is
unisexual.

_Carex_ (Fig. 285) has _naked_, most frequently monœcious flowers.
The ♂-_spikes_, which are generally placed at the summit of the whole
compound inflorescence, are _not compound_; in the axil of each
floral-leaf (bract) _a flower is borne, consisting only_ of a short
axis with three stamens (Fig. 285 _A_). The ♀-_spikes are compound_;
in the axil of each floral-leaf is borne a very small branch (Fig. 285
_D_, _a_) which _bears only one leaf_, namely, a _2-keeled fore-leaf_
(_utriculus_, _utr._ in the figures) which is turned posteriorly (as
the fore-leaves of the other Monocotyledons), and being obliquely
sheath-like, envelopes the branch (in the same manner as the sheath
of the vegetative leaves), and forms a pitcher-like body. In the axil
of _this_ leaf the ♀-flower is situated as a branch of the 3rd order,
bearing only the 2–3 carpels, which are united into one gynœceum.
The style protrudes through the mouth of the utriculus. ~The axis
of the 2nd order (_a_ in Fig. 285 _D_) may sometimes elongate as a
bristle-like projection (normally in _Uncinia_, in which it ends as a
hook, hence the name); this projection is in most cases barren, but it
sometimes bears 1–several bracts which support male-flowers; this is
normal in _Elyna_ (or _Kobresia_) and _Schœnoxiphium_; the axis (_a_ in
285 _E_) bears at its base a female-flower supported by the utriculus,
and above it a male-flower supported by its bract.~

   POLLINATION by means of the wind. Protogynous. Sometimes
   self-pollinated. The order embraces nearly 3,000 species, found
   all over the world. _Carex_ and _Scirpus_ are most numerous in
   cold and temperate climates, and become less numerous towards
   the equator. The reverse is the case with _Cyperus_ and other
   tropical genera. They generally confine themselves to sour,
   swampy districts; some, on the other hand, are characteristic
   of sand-dunes, such as Sand-star (_Carex arenaria_). There are
   about 70 native species of _Carex_.

   USES. In spite of their large number, the Cyperaceæ are of
   no importance as fodder-grasses, as they are dry and contain
   a large amount of silica; hence the edges of many of the
   triangular stems or leaves are exceedingly sharp and cutting.
   _Cyperus esculentus_ has tuberous rhizomes, which contain a
   large amount of fatty oil and are edible (earth-almonds); it
   has its home in the countries of the Mediterranean, where it is
   cultivated.

   _Cyperus papyrus_ (W. Asia, Egypt, Sicily) attains a height of
   several metres, and has stems of the thickness of an arm which
   were used by the ancient Egyptians for making paper (papyrus).
   Some serve for plaiting, mats, etc. (_Scirpus lacustris_, etc.).
   _Isolepis_ is an ornamental plant.

  [Illustration: FIG. 287.--_Triticum_: _A_ axis (rachis) of ear
  showing the notches where the spikelets were inserted; _B_ an
  entire spikelet; _C_ a flower with the pales; _D_ a flower
  without the pales, showing the lodicules at the base; _E_ glume;
  _F_ outer pale; _G_ inner pale; _H_ fruit; _I_ longitudinal
  section of fruit.]

Order 3. =Gramineæ= (=Grasses=). The stems are cylindrical, generally
_hollow_ with _swollen nodes_, that is, a swelling is found at the base
of each leaf which apparently belongs to the stem, but in reality it
is the swollen base of the leaf. The leaves are _exactly alternate_;
the sheath is _split_ (excep. _Bromus_-species, _Poa pratensis_, _P.
trivialis_, _Melica_, _Dactylis_, etc., in which the sheath is not
split), and the edges overlap alternately, the right over the left,
and _vice versâ_; the _ligule_ is nearly always well developed. In
general, the flowers are hermaphrodite; they are borne in _spikelets_
with _alternate floral-leaves_, and the spikelets themselves are
borne in either _spikes_ or _panicles_. The two (seldom more) _lowest
floral-leaves_ in each spikelet (Fig. 289 _øY_, _nY_) are _barren_ (as
the covering-leaves in many umbels and capitula); these are termed
the _glumes_. The succeeding floral-leaves, each of which supports
one flower as its bract, are called the _outer pales_ (_nI_); these
sometimes each bear an “awn” (a bristle-like body which projects in
the median line either from the apex or the back); sometimes the
upper ones are barren. Each flower has a _bracteole_, which is placed
on the inside opposite the main axis; it is thin, _binerved_ or
_two-keeled_, and never has an awn; it is known as the _inner pale_
(_øI_). Immediately succeeding the bracteole are: (_a_) some _small,
delicate scales_ (_lodicules_, Figs. 287 _D_, 288 _C_, 290 _L_); (_b_)
_three stamens_ with anthers _versatile_, so as to be easily moved,
and usually notched at each end (Fig. 287 _C_); and (_c_) a simple
gynœceum formed of _one carpel_ with _two styles_ having generally
_spirally-branched stigmas_ (Figs. 287 _D_, 288 _C_). The ovary is
_unilocular_, and contains one ascending or pendulous, anatropous
ovule. _Fruit a nut_, whose seed is always _firmly united with the thin
pericarp_ (“caryopsis”). The embryo is larger than in the Cyperaceæ and
is placed at the base of the seed, but on the _outer convex surface_
of the pericarp (Figs. 287 _I_, 288 288 _D_, 291), _outside the
endosperm_; plumule large with several leaf-primordia. On germination
the cotyledon remains in the seed.

The majority of Grasses are annual or perennial herbs; tree-like forms
being only found in the Tropics, for example, the Bamboos; they branch
(in tufts), especially from the axils of the basal-leaves, while those
which are borne higher on the stem are separated by longer internodes
and have no vegetative branches in their axils, though a few forms,
like _Bambusa_ and _Calamagrostis lanceolata_, produce branches in
these axils.

  [Illustration: FIG. 288.--_Bromus mollis_: _A_ inflorescence; _B_
  the uppermost flower of a spikelet, with its axis turned forward;
  in front is seen the two-keeled inner pale (bracteole) and the
  stamens protrude between this and the outer pale (bract); _C_ an
  ovary with the 2 stigmas on its anterior side, the 2 lodicules,
  and the 3 stamens; _D_ the fruit seen from the dorsal side; _E_
  the same from the ventral side.]

  [Illustration: FIG. 289.--Diagrammatic outline of a spikelet: _n
  Y_ lower glume; _ø Y_ upper glume; _n I_ upper pale; _ø I_ the
  inner pale; _l_-_l_ lodicules; _st_ stamens; _I_-_I_ main axes;
  _II_ lateral axes.]

  [Illustration: FIG. 290.--Diagram of the Grass-flower: _ni_ outer
  pale; _øi_ inner pale; _l_-_l_ lodicules.]

  [Illustration: FIG. 291.--Longitudinal section of an Oat-grain:
  _a_ the skin (pericarp and testa); _b_ the endosperm; _c_ the
  cotyledon; _d_ the plumule.]

   Only a few Grasses have a _solid stem_, such as Maize,
   Sugar-cane, and _Andropogon_. The _blade_ is flat in the
   meadow-grasses, but the Grasses which live on dry places
   (“prairie-grass”) exposed to the sun, often have the blade
   tightly rolled up and almost filiform or bristle-like, with
   anomalous anatomical structure. A _closed_ tubular _sheath_ is
   found in _Melica uniflora_, _Bromus_-species, _Poa pratensis_
   and _trivialis_, _Briza_ and some _Glyceria_-species. The
   sheath is developed for the purpose of supporting the young
   internodes while their growth is proceeding at the base. The
   “nodes” (the swollen joints which are seen on stems of Grasses)
   are not really part of the stem but are formed by the base of
   the leaf-sheath. They play a part in assisting the haulms
   to regain a vertical position when laid prostrate by wind
   or rain. The _awn_ on the pale is homologous with the blade
   of the Grass-leaf, and the pale itself is the sheath. The
   arrangement of the leaves in the _spikelet_ is similar to that
   in _Cyperus_ and other Cyperaceæ, their floral-leaves being
   borne in several rows in _Streptochæta_. More than two barren
   “glumes” are found in _Streptochæta_, several Phalarideæ and
   others. The spikelets, too, are again arranged in two rows in
   the axils of suppressed floral-leaves. The inflorescence becomes
   a “compound spike” (ear) when the spikelets are sessile. In the
   majority of instances the spikelets are borne on long stalks;
   when these branch, then the secondary branches, and similarly
   all branches of higher order, are placed so far down upon the
   mother-axis that they all appear to be of equal value and to
   arise in a semicircle from the mother-axis itself, though in
   reality they arise from each other (_Panicle_, Fig. 288 _A_).
   Sometimes the main axis and branches of different orders unite
   together as in _Alopecurus_, _Phleum_, and some other Grasses,
   and hence the single (short-stalked) spikelets appear to arise
   singly and spirally, or without any definite order, directly
   from the main axis, with the production of a _cylindrical_
   inflorescence bearing “spikes” _on all sides_, that is, a
   “_spike-like panicle_.”--Many inflorescences are somewhat
   dorsiventral. The _flower_ is rarely unisexual (_Zea mais_) or
   barren. Considerable difficulty is experienced in reducing the
   Grass-flower to the ordinary 3-merous Monocotyledonous type.
   Some authorities consider the _lodicules_, which are present
   in all Grasses but absent in the Cyperaceæ, to be homologous
   with a perianth. According to a more recent theory they are
   bracteoles, and hence the Gramineæ, like many of the Juncaceæ,
   have 2–3 bracteoles placed in two rows in the median plane. If
   this theory be correct, the _flower is naked_. The lodicules
   expand quickly and cause the opening of the flower (_i.e._ the
   two pales become separated from each other). Generally only 3
   _stamens_ belonging to the outer whorl are present (Fig. 290),
   as in _Iris_ (Fig. 279), certain Juncaceæ and Cyperaceæ (Fig.
   284), but in some, such as the Rice and certain species of
   Bamboos, all 6 are found. _Pariana_ has more than 6. Only 1 of
   the _carpels_ is present, namely, the anterior (of those in Fig.
   284), so that the ventral suture and the place of attachment
   of the ovule are situated at the back of the ovary. The number
   of styles does not correspond with the number of carpels, and
   the styles may therefore be supposed to arise from the edges
   of the leaf to the right and left--a position which is not
   without analogy. In addition, a stylar projection is sometimes
   found on the anterior side and in the median line (_e.g._ in
   _Phragmites_), and the solitary style in _Nardus_ has exactly
   this position; a similar arrangement is found in some species of
   _Bambusa_ which have only one style; other species of _Bambusa_
   have three styles. A tripartite style is found in _Pharus_.

   [The Grass-flower may be reduced to the ordinary
   Monocotyledonous type thus:--The outer pale is the bract of the
   flower since it bears in its axil the floral shoot; the inner
   pale occupies the customary position of the bracteole. The fact
   that it is binerved can be explained by its having been pressed
   against the main-axis during development. Similar binerved
   bracteoles are found in _Iris_ (Fig. 279). These bracteoles in
   both Grass and Iris arise from single primordia, and are not
   produced by the coalescence of two leaves. The lodicules are the
   only parts of the perianth remaining, the outer whorl having
   been suppressed, and also the posterior leaf of the inner whorl;
   a posterior lodicule, however, is found in the Rice and some
   species of Bamboo. The outer whorl of stamens is usually absent,
   though this again is present in the Rice and Bamboo. The three
   carpels are reduced to one with two or sometimes three stigmas.]

   THE FLOWERING. In the panicles the flowers open in basipetal
   order; the flowers in the spikes situated somewhat above the
   middle, commence to open first, and the flowering proceeds
   upwards and downwards. A few Grass-flowers never open
   (cleistogamic); _Leersia oryzoides_, _Stipa_-species, and _e.g._
   Wheat and Rye in cold damp weather; some open their pales so
   wide that the anthers and stigmas may protrude at the top; most
   frequently the lodicules expand and force the pales suddenly
   and widely apart. The filaments elongate considerably, so that
   the anthers are pendulous and the stigmas unfold. In some
   Grasses _e.g._ Wheat, the blooming of each flower only lasts
   a short time. POLLINATION is generally effected by the wind.
   The _Rye_ separates the pales very widely in the morning, and
   allows the anthers and stigmas to appear; it is almost entirely
   sterile when self-pollinated. The _Wheat_ flowers at any time
   of the day, each flower lasting only a quarter of an hour. The
   pales open suddenly, but only half way, and the anthers scatter
   one-third of the pollen in their own flower and two-thirds
   outside. Self-pollination is effectual, but crossing gives
   better results. In _Hordeum vulgare_ (all flowers ☿) the flowers
   of the 4 outer rows behave as in the Wheat, but those in the
   two central rows always remain closed. The ☿-flowers in the
   two central rows of _H. distichum_ remain closed and fertilise
   themselves; they open exceptionally, and may be pollinated
   by the ♂-flowers in the 4 lateral rows. _H. hexastichum_ is
   cleistogamic. _Oats_ pollinate themselves.

  [Illustration: FIG. 292.--Barley grain: _A_ section through the
  skin (_a-d_) and the most external part of the endosperm; _Gl_
  the “aleurone layer”; _st_ starch-containing cells; _B_ starch
  grains.]

  [Illustration: FIG. 293.--Wheat-grain germinating: _g_ the
  plumule; _b_ the first leaf succeeding the cotyledon; _r^1_ the
  primary root; _r^2_ lateral root.]

  [Illustration: FIG. 294.--Older seedling of the Wheat: _s_ the
  second sheathing-leaf; _l_ first foliage-leaf.]

   _The ripe Grass-fruit_, in some species of Bamboo, is a berry;
   in some other Grasses a nut with _loosely_ lying seed, in some
   even a capsule, but otherwise a “caryopsis.” In some instances
   it is loosely enveloped by the pales (Oat), in others firmly
   attached to these (Barley), and finally, in others, “naked,”
   _i.e._ it is entirely free from the pales (Wheat and Rye).
   On the ventral side there is a groove (Fig. 288 _E_); on the
   anterior side (dorsal suture), which is turned towards the
   inner pale, it is convex, and at the base on this side, inside
   the testa, lies the embryo (Fig. 288 _D_). The apex of the
   fruit is often hairy (Fig. 293). The _skin_ (Fig. 291, _a_) is
   formed by the pericarp and testa, and in some cases (Barley)
   the pales also form the outer portion. The endosperm (_b_) is
   large, and formed of parenchymatous, starch-containing cells:
   aleurone (proteid) grains may also be found among them. When
   the starch-grains and the aleurone-grains adhere together
   the endosperm becomes “horny,” but is “floury” when the
   starch-grains lie loosely with air between them. In the most
   external region, just beneath the skin, 1–several layers of
   nearly cubical cells (filled principally with aleurone-grains
   and fat) are found, the _aleurone_-layer (Fig. 292). The embryo
   (Fig. 291 _c-d_) contains large quantities of fatty oil;
   the large shield-like structure, attached to the embryo and
   turned inwards towards the endosperm (_c_), is the cotyledon
   (scutellum); it remains enclosed in the seed during germination,
   and dissolves the endosperm by means of the peculiar epithelial
   cells developed on the dorsal surface. The radicle, on
   germination, is obliged to perforate a mass of cells derived
   from the suspensor and which form the “root-sheath” (coleorhiza,
   Fig. 293) round its base. In addition to the tap-root, lateral
   roots are frequently developed before germination; these quickly
   break through, and later on are followed by others which appear
   at the base of the leaf (Figs. 293, 294).

   The DISTRIBUTION OF THE FRUIT is most frequently effected by the
   wind. The spirally-twisted and hygroscopic awn which persists on
   the fruits of some species (_Avena_, _Stipa_, etc.) assists in
   their dissemination, and even helps to bury them in the ground.

   The two preceding orders are more closely related to each other
   than they are to the Gramineæ.

   The generic differences are chiefly founded on the form of
   the inflorescence, the number and sex of the flowers in the
   spikelets, the shape and relative length of the pales, awns,
   etc. In addition to these the structure of the fruit and
   seed presents a great many differences; some have compound
   starch-grains, while in others they are single; some have 1
   layer of aleurone-cells, others have several (Fig. 292), etc.

=1.= BAMBUSEÆ. Tall Grasses with woody, very siliceous stems which bear
many branches in the axils of the leaves. 6 stamens. _Bambusa_ (Bamboo).

=2.= ORYZEÆ. _Oryza sativa_ (Rice) is a herbaceous marsh-plant, with
panicle and small, 1-flowered spikelets, with two small glumes and two
large, boat-shaped, strongly siliceous pales. 6 stamens.--_Leersia._
_Lygeum. Pharus. Zizania aquatica._

=3.= MAYDEÆ. _Zea mais_ (Indian-corn, Maize); the spikelets are
unisexual; the ♂-spikelets in a terminal panicle; the ♀-spikelets
closely crowded and arranged in many rows in a thick, axillary spike,
enclosed by large sheathing-leaves. The ♀-spikelets are 1-(2-)
flowered; the ovary bears one, long, filamentous style, with bifid
stigma.--_Euchlæna_; _Coix_.

=4.= ANDROPOGONEÆ. _Saccharum_ (Sugar-cane); the spikelets
are exceptionally small, 1-flowered, and borne in pairs in
many-flowered, long-haired panicles. Tall grasses with solid, sappy
stem.--_Andropogon._

=5.= FESTUCEÆ. Grasses with panicle (or spike-like panicle) and
2–several-flowered spikelets. Glumes small, in each case shorter than
the spikelet.--_Festuca_ (Fescue) and _Bromus_ (Brome, Fig. 288)
have the awn placed at the _apex_ of the pale, or slightly below
it. _Festuca_ has perennial species, with only a sparsely-branched
panicle with branches solitary or in pairs, and round spikelets; the
leaf-sheath is widely open. _Bromus_ has the branches borne in half
whorls, and the leaf-sheath scarcely half open. _Brachypodium_ has very
short-stalked spikelets in a raceme.--_Poa_ (Meadow-grass), _Briza_
(Quaking-grass) and _Glyceria_ have awnless spikelets; these in _Poa_
are ovoid, compressed, and with sharply-keeled glumes; in _Briza_ they
are broad, cordate and drooping, with boat-shaped glumes; in _Glyceria_
round, long, many-flowered, linear or lanceolate; some species of
_Glyceria_ have closed leaf-sheaths.--_Dactylis_ (Cock’s-foot) differs
from all others in the somewhat crowded and unilateral (subsecund)
spikelets, which are compressed and oblique (_i.e._ one side more
convex than the other).--_Phragmites_ (_P. communis_, Reed); the
lowermost flowers of the spikelet are ♂; its axis is covered with
long, silky hairs; pales without awns, but acuminate. Perennial
marsh-plants.--_Melica_; panicle small, sparsely-branched with
round, awnless, few-flowered, usually drooping spikelets. The upper
pales, with arrested flowers, are generally united into a club-like
mass.--_Molinia_, _Eragrostis_, _Koeleria_, _Catabrosa_.--_Cynosurus_
(Dog’s-tail) has a small, spicate panicle with unilateral spikelets,
some of which are fertile, some barren, each supported by a pectinate
scale. _Arundo. Sesleria. Gynerium. Triodia._

=6.= AVENEÆ. Panicles with 2–many-flowered spikelets; at least one
of the glumes is quite as long as the entire spikelet.--_Avena_
(Oat). The pale is boat-shaped, often bifid, and at about the middle
of the back has a twisted, bent awn.--_Aira_ (Hair-grass) has a
long-branched panicle with small, 2-flowered spikelets; the pale has
a dentate apex and bears an awn on the posterior side close to the
base.--_Weingærtneria._--_Holcus_ (Yorkshire-fog); a soft, hairy Grass
with an open panicle, keeled glumes; 2 flowers in the spikelet, of
which the lower one is ☿, the upper ♂; the pale which supports the
☿-flower has no awn, but that which supports the ♂-flower, on the
contrary, is awned.

=7.= AGROSTIDEÆ. Panicles or spike-like panicles with 1-flowered
spikelets. Generally 2 glumes and only 1 pale.--The following have
PANICLES: _Milium_ with square panicle-branches and round spikelets;
_Agrostis_ (Fiorin), with compressed, glabrous spikelets, whose glumes
are longer than the pales. _Calamagrostis_ differs in having a chaplet
of long hairs at the base of the pale.--_Stipa_ (Feather-grass) has a
long, twisted awn.--The following have SPIKELIKE PANICLES: _Phleum_
(Cat’s-tail, Timothy-grass) has sharply pointed, entirely free glumes,
which are much longer than the awnless pales. _Alopecurus_ (Fox-tail);
glumes united below; pale with awn. _Ammophila_ (_Psamma_). _A.
arundinacea_; pales hairy at base; perennial, stiff-leaved, glaucous
sand-grass with creeping rhizome. _Aristida. Sporobolus._

=8.= PHALARIDEÆ. Panicles and spike-like panicles. The spikelet has
in the upper part a single fertile flower; below it are placed 4
pales, of which the upper 1–2 sometimes support ♂-flowers. On the
whole, 6 floral-leaves of the first order are present.--_Phalaris_
(_P. canariensis_, Canary-grass) has an ovate, spike-like panicle,
the spikelets are compressed, convex on the outer side, concave on
the inner. The large glumes are winged on the back.--_Digraphis_ (_D.
arundinacea_) is closely allied to _Phalaris_, but the keel of the
glumes is not winged.--_Anthoxanthum_ (_A. odoratum_, Sweet-vernal) has
a small, lanceolate, open, spike-like panicle; the spikelets have below
2 barren flowers, and above these an ☿-flower with 2 stamens. The upper
glume is longer than the flower.--_Hierochloa._

   =9.= CHLORIDEÆ. The spikelets are arranged in the form of a
   spike in two rows on one side of an often flatly-compressed
   axis; they are mostly 1-flowered.--_Chloris_; _Ctenium_;
   _Cynodon_; _Eleusine_; _Microchloa_.

   =10.= PANICEÆ. The spikelets are borne in panicles or spikes,
   which may be arranged like fingers or in a raceme. There
   is a centrally-placed ☿-flower; below it is sometimes a
   ♂-flower.--_Panicum_; _Paspalum_; _Oplismenus_; _Setaria_ has
   an almost cylindrical spike-like panicle with several barren
   branchlets, which project as stiff, rough bristles.--_Cenchrus_;
   _Pennisetum_.

=11.= HORDEÆ. Spikes compound; spikelets sessile in the
notches of a toothed axis.

=A.= Spikelets solitary.--_Triticum_ (Wheat, Fig. 287) has in each
tooth of the main axis, a several-flowered spikelet which turns its
_flat side_ towards the central axis. The cultivated species (true
Wheat) are 1-2-annual, the wild ones (_T. repens_, Couch, also as an
independent genus, _Agropyrum_) are perennial, with creeping rhizome
and lanceolate glumes.--_Lolium_ (Rye-grass) has in each tooth of
the main axis a many-flowered, compressed spikelet, which is placed
_edgewise_ towards it and (with the exception of _L. perenne_) has
only one outwardly-turned glume (_L. temulentum_ has a rudiment of
the inwardly-turned lower glume); the terminal spikelet has two
glumes.--_Secale_ (Rye). A two-flowered spikelet in each tooth; small,
lanceolate, acuminate glumes. _Nardus_ and _Lepturus_ have very narrow
spikes, the former with unilateral spikelets.

=B.= In each notch of the axis 2 or more spikelets are placed close
together.--_Hordeum_ (Barley). In each tooth three 1-flowered
spikelets. _H. hexastichum_ (6-rowed Barley), has 6 rows of fruits,
since all the spikelets are fertile, and _H. distichum_ (2-rowed
Barley) 2 rows, since the lateral spikelets are (♂, and barren (p.
292).--_Elymus_ has 2–6 many-flowered spikelets in each joint of the
main axis. _Ægilops_ has awns upon the glumes.

   DISTRIBUTION. 315 genera with 3,500 species. The order is
   distributed over the whole world, and as regards number of
   individuals is perhaps the richest. In the Tropics, large,
   broad-leaved, tree-like forms are found (_Bambuseæ_, _Olyreæ_,
   _Andropogoneæ_, etc.; in S. Europe, _Arundo donax_); in England,
   next to the Compositæ, it is the order most rich in species
   (about 134).--The origin of some of the cultivated Grasses
   is lost in obscurity. The Maize, no doubt, was indigenous to
   America, where its nearest relatives are found, and where it
   has also been discovered in ancient Indian graves; Durra or
   Guinea-corn, Millet and Sugar-cane are South Asiatic plants, and
   our own cereals no doubt have sprung primarily from Western Asia
   and South-Eastern Europe (Barley from Armenia and Persia, where
   a very closely related wild species is found; Wheat from the
   same districts; Rye from the perennial species _S. montanum_).
   _Panicum altissimum_ and Rice have come from Africa.

   USES. The Grasses play a very important part as cereals and
   fodder plants. The following are the most important of the
   cultivated ones: _Triticum vulgare_ (common Wheat), _turgidum_,
   _amyleum_, _polonicum_, _spelta_, _durum_, etc.; _Secale
   cereale_ (Rye); Barley (_Hordeum_-species, see under the genus);
   Maize; Oats (_Avena sativa_, _orientalis_, _nuda_); Millet
   (_Panicum miliaceum_); Durra (Turkish Millet, or Guinea-corn,
   _Sorghum vulgare_, _cernuum_ and _saccharatum_); Manna-grass
   (_Glyceria fluitans_). As fodder-plants especially: Rye-grass
   (_Lolium perenne_); Oat-grass (_Avena elatior_); Timothy
   (_Phleum pratense_); Fox-tail (_Alopecurus pratensis_);
   Cock’s foot (_Dactylis glomerata_); Dog’s tail (_Cynosurus
   cristatus_); Sweet-vernal (_Anthoxanthum odoratum_); Soft grass,
   or Yorkshire-fog (_Holcus lanatus_ and _mollis_); Quaking-grass
   (_Briza media_); species of Meadow-grass (_Poa_); Fescue
   (_Festuca_) and Brome (_Bromus_).--Several cultivated species of
   Grass are also used in the preparation of _fermented liquors_,
   the starch in the seeds being transformed to _sugar_ (beer
   from “Malt,” _i.e._ the germinated Barley; arrack from Rice);
   or the stem becomes specially saccharine before flowering: the
   Sugar-cane, _Sorghum saccharatum_.

   OFFICINAL. The rhizome of _Triticum repens_, Oat-grain, flour of
   Barley, and the starch of Wheat, also sugar.

   The seeds of _Lolium temulentum_ are considered
   _poisonous_.--The stems of many species (including our common
   grains) are used in the manufacture of paper, especially
   “Esparto grass” (_Stipa tenacissima_) from Spain and N.
   Africa, and the sheathing-leaves of the ♀-spike of _Maize_.
   Sand Lyme-grass (_Elymus arenarius_), and especially _Psamma
   arenaria_, are important.--But few Grass-species are
   _sweet-scented_: _Anthoxanthum odoratum_ and _Hierochloa
   odorata_ contain coumarin; _Andropogon_-species have essential
   oils (“Citronella oil”).--ORNAMENTAL PLANTS are: the
   “Ribbon-grass” (a variety of _Digraphis arundinacea_), _Stipa
   pennata_ (whose awn is exceedingly long and feathery), _Gynerium
   argenteum_ (Pampas-grass), _Lagurus ovatus_, _Hordeum jubatum_,
   _Bromus briziformis_.


                       Family 3. =Spadicifloræ.=

The primitive form resembles that of the preceding family. In it
we find the typical, perfectly developed, Monocotyledonous flower,
sometimes even with free carpels and with a dry or somewhat fleshy, but
never petaloid perianth; and this passes over into very different forms
by the suppression of the floral-leaves, perianth and sporophylls
(unisexual flowers are common), and by the close aggregation of the
flowers in the inflorescence. The flower is _hypogynous_ in every case.
The inflorescence is a _spike_ which may be either single or branched,
and has often a thick and fleshy axis (a _spadix_). In Palms and Araceæ
it is enveloped, at any rate prior to the opening of the flowers, by a
very large floral-leaf, _the spathe_, which may be petaloid (Figs. 297,
301).

The fruit is most frequently fleshy (_berry_, _drupe_) or a _nut_,
never a capsule. The embryo is small, with large, fleshy endosperm
(Fig. 299 _C_); very rarely the endosperm is wanting.

  [Illustration: FIG. 295.--Piassava (_Attalea funifera_).]

  [Illustration: FIG. 296.--A portion of the stem of _Attalea
  funifera_ with persistent leaf-bases.]

The numerous plants belonging to this family are large, herbaceous or
tree-like, and the leaves seldom have the usual Monocotyledonous form,
_i.e._ linear with parallel venation, but most frequently have pinnate
or palmate venation.

Order 1. =Palmæ (Palms).= The majority are trees with an _unbranched_,
cylindrical _stem_, having short internodes and covered with leaf-scars
or the bases of the leaf-stalks (Fig. 296), and at the summit a rosette
of large leaves closely packed together (Fig. 295). An exception to
this is found in _Calamus_ (Cane, “Rotang”), whose thin, creeping or
climbing stems have long internodes; sparsely[28] branched is, _e.g._
the African Doum-palm (_Hyphæne_). Notwithstanding their often enormous
stems the Palms have fibrous roots, like the bulbous Monocotyledons.
The leaves are pinnate (Feather-palms, Fig. 298) or palmate (Fan-palms,
Fig. 295) and often very large; they have a well-developed petiole
with an _amplexicaul sheath_, which is often more or less separated
into a large number of fibres. _In the bud the blade is entire but
folded_, as the leaf expands the lines of folding are torn, either
those which are turned upwards (thus ∨ ∨ ∨ ∨, _e.g. Pritchardia_,
_Livistona_, _Phœnix_, _Chamærops_) or those turned downwards (thus
∧ ∧ ∧ ∧, _e.g. Cocos_, _Chamædorea_, _Calamus_). The inflorescence
is usually lateral; when, as in Sago-palm (_Metroxylon rumphii_)
or Talipot (_Corypha umbraculifera_) it is terminal, the plant is
monocarpic, and dies after flowering; it is often a very _large_
and _branched spadix_ with numerous flowers either borne externally
or embedded in it, and enclosed either in one woody, boat-shaped
_spathe_ (Fig. 297) or several spathes, in the latter case one for each
branch. The flowers are sessile or even embedded, regular, generally
_unisexual_ (monœcious or diœcious) with the usual diagram (Fig.
278); the perianth is inconspicuous, green or yellow, persistent, and
more or less leathery or fleshy. 6, rarely 3 or many stamens. The 3
carpels remain either _distinct_ or form one, generally 3-locular,
ovary. The style is short. There is _one ovule in each carpel_. Often
during ripening 2 carpels with their ovules are aborted. The fruit is
a _berry_, _drupe_ or _nut_, generally one-seeded, with a large horny
or bony endosperm with hard thick-walled cells (_e.g._ Date-palm). In
some (_e.g._ Cocoanut) it is thin-walled, soft, and oily; in several
“ruminate.”

   When _germination_ commences in the Cocoanut, Date, etc., the
   apex of the cotyledon remains in the seed and developes into
   a spongy mass to withdraw the endosperm; in the Cocoanut it
   attains a considerable size (Fig. 299 _C_) and assumes the
   form of the fruit. The endosperm in the Cocoanut is hollow and
   the interior is filled with “milk.” In the Date-palm and the
   Vegetable-ivory (_Phytelephas_) the cell-walls of the hard
   endosperm serve as reserve material.

=1.= PHŒNICEÆ. _Phœnix_ (Date-palm) has pinnate leaves with channeled
leaflets and diœcious flowers with 8 free carpels, of which usually
only one developes into a berry with membranous endocarp; the large
seed has a deep furrow on the inner side, and horny endosperm.

  [Illustration: FIG. 297.--Inflorescence of a Palm with spathe. At
  the top ♂-, at the base ♀-flowers.]

  [Illustration: FIG. 298.--_Livistona australis._]

=2.= SABALEÆ. These have fan-like leaves with channeled segments;
flowers ☿ or polygamous, rarely diœcious, with 3 separate or only
slightly united carpels, all of which are sometimes developed
into fruits (berry or drupe, with thin stone).--_Chamærops_, the
Dwarf-palm. The pericarp is externally fleshy, internally more
fibrous, and provided with a membranous inner layer. The endosperm is
ruminate (that is, the testa is several times deeply folded into the
endosperm).--_Sabal_, _Copernicia_, _Livistona_ (Fig. 298), _Thrinax_,
_Corypha_, _Brahea_, and others.

  [Illustration: FIG. 299.--_A_ Longitudinal section of a Cocoanut
  (diminished), the inner layer only (the stone) not being divided
  _B_ End view of the stone, showing the sutures for the 3 carpels
  (_a_), and the 3 germ-pores; the embryo emerges from the lowest
  one when germination begins. _C_ Germinating; inside the stone is
  seen the hollow endosperm and the enlarging cotyledon.]

=3.= COCOINEÆ. With pinnate leaves. Monœcious inflorescence. The
carpels are united into a 3-locular ovary. The fruit is most frequently
1-locular, only 1 of the loculi becoming developed, rarely 3-locular;
it is a drupe with a large, fibrous, external layer (_mesocarp_) and
most frequently a very hard inner layer (_endocarp_, stone) which
has 3 germ-pores, the 2 of these, however, which correspond to the
suppressed loculi are closed; internal to the third lies the small
embryo (Fig. 299). Endosperm containing abundance of oil. _Cocos_ (the
Cocoanut-palm), _Attalea_, _Elæis_, _Acrocomia_, _Bactris_.

=4.= LEPIDOCARYINÆ. The floral-leaves and flowers are borne in 2
rows on the spadix. The carpels are united into one 3-locular ovary;
the fruit is coated by a layer of hard, shining, imbricate scales.
The majority of the species are thorny, and climb by means of the
thorny leaves. Some have fan-like (_Mauritia_), others pinnate leaves
(_Raphia_, _Calamus_, _Eugeissonia_, _Metroxylon_; the stems of the
latter die after the first flowering).

   =5.= BORASSINÆ. Large Fan-palms without thorns, with 3-locular
   ovary. Drupe with separate stones. _Latania_ and _Lodoicea_ have
   many stamens; _Hyphæne_; _Borassus_ (Palmyra-palm).

   =6.= ARECINEÆ. The most numerous group. Feather-palms. Berry.
   _Areca_, _Euterpe_, _Oreodoxa_, _Ceroxylon_, _Chamædorea_,
   _Geonoma_, _Caryota_ with bipinnate leaves.

   =7.= PHYTELEPHANTINÆ. Flowers with rudimentary perianth united
   in close capitula. _Phytelephas_ (Vegetable-ivory). _Nipa._

   DISTRIBUTION. About 1,100 species are known. In Europe
   only the Dwarf-palm (_Chamærops humilis_) is wild (Western
   Mediterranean). The Date palm (_Phœnix dactylifera_) belongs
   to North Africa and West Asia. Other African genera are
   _Hyphæne_ (Doum-palm) and _Elæis_ (_E. guineensis_, Oil-palm).
   A large majority of the genera are found in South America and
   in the East Indies. The following are AMERICAN:--_Mauritia_,
   _Acrocomia_, _Bactris_, _Chamædorea_, _Oreodoxa_, _Euterpe_,
   _Attalea_, etc. ASIATIC:--_Metroxylon_, _Calamus_, _Areca_,
   _Borassus_, _Lodoicea_ (“Double-cocoanuts,” Seychelles) and
   others. The Cocoanut-palm has perhaps an American origin; all
   the other species of the same genus being endemic in America;
   it is the only Palm found on the coral islands of the Pacific
   Ocean, and is also the only one which is common to both
   hemispheres.

   USES. Palms belong to the most useful plants; they contain no
   poison, and are of little medicinal interest, but are largely
   employed in the arts and manufactures, the hard timber being
   adapted for many purposes on account of the hard tissue in
   which the vascular bundles are embedded. “Cane” is the stem
   of _Calamus_-species (from India). SAGO is obtained from the
   pith of _Metroxylon rumphii_ (Sago-palm, Sunda-Is., Moluccas),
   _Mauritia flexuosa_, etc. Sugar-containing sap (“palm wine”) is
   obtained from the American _Mauritia vinifera_ and _flexuosa_,
   _Borassus flabelliformis_ (Asiatic Palmyra-palm), _Arenga
   saccharifera_, etc., by cutting off the young inflorescences,
   or by perforating the stem before the flowering (_arrack_ is
   distilled from this). _Vascular strands_ for the manufacture of
   mats and brushes, etc., are obtained from the outer covering
   (mesocarp) of the Cocoanut, and from the detached leaf-sheaths
   of _Attalea funifera_ (Brazil) (Fig. 296). WAX is yielded by the
   leaves of _Copernicia cerifera_ (carnaueba-wax, Amazon region),
   and by the stem of _Ceroxylon andicola_ (palm-wax, Andes);
   East Indian _Dragon’s blood_ is from the fruit of _Calamus
   draco_; the young buds of many species, especially _Euterpe_,
   _Cocos_, _Attalea_, etc., are used as “cabbage.” Palm-oil is
   obtained from the oily mesocarp of the plum-like fruits of
   _Elæis guineensis_ (W. Africa), and from the seeds, when it is
   largely used in the manufacture of soap. EDIBLE FRUITS from the
   Date-palm (_Phœnix dactylifera_, Arabia, Egypt, W. Africa), and
   the endosperm of the Cocoanut (_Cocos nucifera_). The seeds
   and the unripe fruits of the Areca-palm (_Areca catechu_)
   are chewed with the leaves of the Betelpeper, principally in
   Asia. VEGETABLE IVORY from the hard endosperm of _Phytelephas
   macrocarpa_ (S. America.)--Many species are cultivated in
   the tropics as ornamental plants, but in this country only
   _Chamærops humilis_, _Livistona australis_ and _chinensis_ are
   generally grown. In addition to the few just mentioned, many
   others are of importance, but these are much the most useful.

   Order 2. =Cyclanthaceæ.= This is a small order related to the
   Palms (44 species from Tropical America), with fan-like, folded
   leaves. The flowers are unisexual and arranged in whorls or
   close spirals on an unbranched spadix. Ovary unilocular, ovules
   numerous. To this belongs _Carludovica palmata_, whose leaves
   are used for Panama hats.

   Order 3. =Pandanaceæ= (Screw-pines) is another small order,
   forming a transition to the Araceæ. The woody, (apparently)
   dichotomous stem is supported by a large number of aerial roots,
   which sometimes entirely support it when the lower portion of
   the stem has decayed. The leaves are closely crowded together,
   and arranged on the branches in three rows, which are often
   obliquely displaced, with the formation of three spiral lines;
   they are, as in the Bromeliaceæ, amplexicaul, long, linear,
   the edge and lower midrib often provided with thorns. The
   ♂-flowers are borne in branched, the ♀ in unbranched spadices
   or capitula, which resemble those of _Sparganium_, but have no
   floral-leaves. Perianth absent. The drupes or berries unite into
   multiple fruits.--About 80 species in the islands of the Indian
   Ocean.--_Pandanus_, _Freycinetia_.--Fossils perhaps in the chalk
   of the Harz.

Order 4. =Typhaceæ.= The flowers are unisexual, monœcious, and borne
on a cylindrical spike or globose capitulum; ♂ inflorescences above,
the ♀ below. The perianth consists of a definite number of scales
(_Sparganium_), or in its place numerous irregularly-arranged hairs are
found (_Typha_); in the ♂-flower there are generally three stamens; the
gynœceum is formed of 1–2 carpels with 1 prolonged style; 1 pendulous
ovule. The seeds are furnished with a seed-cover, which is cast off on
germination.--The few species (about 20) which belong to this order are
marsh plants with creeping rhizome (and hence grow in clusters); the
leaves on the aerial shoots are borne in two rows, entire, very long
and linear.

_Sparganium_ (Bur-reed). The flowers are borne in globose capitula;
the perianth distinct, generally consisting of 3 small scales; pistil
bicarpellate. Drupe, dry and woody. ~The stalk of the lower ♀ capitula
is sometimes united with the main axis, and consequently the capitula
are situated high above their subtending-leaf.~

_Typha_ (Bulrush, Reed-mace) has a long, cylindrical, brown spike,
the lower portion bearing ♀-flowers, and the upper ♂-flowers, which
is divided into joints by alternate leaves. The ♀-flowers have 1
carpel. The perianth is wanting, represented by a number of fine,
irregularly-placed hairs; pistil unicarpellate. Fruit a nut.

   The two genera, according to some, are related to the 2nd order.
   In both genera native species are found. The pollination is
   effected by the wind, and consequently the anthers project
   considerably, and the stigma is large and hairy. _Typha_ is
   protandrous, _Sparganium_ protogynous. The small, fine hairs
   surrounding the nut of _Typha_ assist in its distribution by the
   wind.--Fossil _Typhas_ in the Tertiary.

Order 5. =Araceæ= (=Arums=). The flowers are small, and always borne
_without bracts or bracteoles_ on _an unbranched_, often very fleshy
spike, which is enclosed by a spathe, often petaloid and coloured (Fig.
301). The fruit is a _berry_. Outer integument of the seed fleshy.--The
leaves have generally sheath, stalk, and blade with distinctly
_reticulate_ venation; they are chiefly cordate or sagittate (Fig.
302), seldom long with parallel venation as in the other Monocotyledons
(_Acorus_, Fig. 300). The Araceæ are quite _glabrous_, generally
_perennial herbs_ with tubers or rhizomes. Many have latex.--For the
rest the structure of these plants varies; for example, while some
have a perianth, in others it is wanting; in some the perianth-leaves
are free, in others united; some have hermaphrodite flowers, but the
majority unisexual (monœcious); some have free, others united stamens;
the ovules are orthotropous, anatropous, or campylotropous, erect or
pendulous; the ovary is 1–many-locular; some have seeds with endosperm,
others without. ~_In habit_ there are great differences. While some,
_e.g. Colocasia_ (Fig. 302), have a thick, more or less upright stem,
with leaf-scars, but not woody, others are climbers, epiphytic, and
maintain themselves firmly by means of adventitious roots, on the stems
and branches of trees, or even on steep rocks, _e.g. Philodendron_;
the cordate, penninerved leaf is the most common (Fig. 302), but
various branched forms appear; the pedate leaves of _Helicophyllum_,
_Dracunculus_, etc., are cymosely branched; the leaves of _Monstera
deliciosa_, perforated by tearing, should be noticed (the vascular
bundles while in the bud grow faster than the tissue between them,
causing the latter to be torn, and the leaf perforated). With regard to
the anatomical structure, the presence or absence of latex, raphides,
resin-passages, groups of mucilage-cells should be noted. Engler makes
use of these anatomical peculiarities for a scientific arrangement of
the order.~

=A.= ORONTIEÆ, CALAMUS-GROUP. ☿, hypogynous flowers of a completely
formed monocotyledonous type (number in the whorls 2, 3, or
4).--_Acorus_ (_A. calamus_, Sweet-flag) has a regular, 3-merous,
pentacyclic flower (Fig. 300 _C_, _D_). They are marsh-plants, with
creeping rhizome, triangular stem, and long, sword-like leaves (Fig.
300 _A_); the inflorescence is terminal, apparently lateral, being
pushed to one side by the upright, sword-like spathe (Fig. 300
_B_).--~_Anthurium_ (Pr2+2, A2+2, G2); _Pothos_; _Orontium_ (unilocular
ovary with one ovule), etc.~

  [Illustration: FIG. 300.--_Acorus calamus_: _A_ habit (much
  reduced); _B_ inflorescence; _C_ a flower; _D_ diagram; _E_
  longitudinal section of an ovary; _F_ an ovule.]

  [Illustration: FIG. 301.--_Arum maculatum._ The spathe (_h_) in
  _B_ is longitudinally divided.]

  [Illustration: FIG. 302.--_Colocasia Boryi._]

=B.= CALLEÆ. Flowers hypogynous, naked, ☿.--_Calla_ (_C. palustris_).
All flowers in the spike are fertile, or the upper ones are ♂; 6–9
stamens; ovary unilocular with many basal ovules. Marsh-plants with
creeping rhizome and cordate leaves.--_Monstera_, _Rhaphidophora_, etc.

=C.= ARINEÆ. Flowers monœcious, naked, ♂-flowers on the upper, ♀ on the
lower part of the spadix.--_Arum_ (Fig. 301). The spadix terminates in
a naked, club-like portion (_k_); below this is a number of sessile
bodies (rudimentary flowers), with broad bases and prolonged, pointed
tips (_b_); underneath these are the ♂-flowers (_m_), each consisting
only of 3–4 short stamens, which eject vermiform pollen-masses through
the terminal pores; then follow, last of all, ♀-flowers (_f_), each of
which consists of one unilocular ovary, with several ovules. Perennial
herbs, tuberous, with cordate leaves.--~_Dracunculus_; _Biarum_;
_Arisarum_; _Pinellia (Atherurus) ternata_ with leaves bearing 1–2
buds. _Zantedeschia æthiopica_ (_Richardia_, Nile-lily); ♂, 2–3
stamens; ♀ with 3 staminodes, 1–5-locular ovary (S. Africa.)--In some
genera sterile flowers are present between the ♂ and ♀ portions of
the spadix (_e.g._ in _Philodendron_); in _Ambrosinia_ a lateral,
wing-like broadening of the axis of the spadix divides the cavity
of the spathe into two chambers, the anterior containing one ♀, and
the posterior 8–10 ♂-flowers in two series; in some the stamens in
the single ♂-flowers unite and form a columnar “synandrium” (_e.g._
in _Dieffenbachia_, _Colocasia_, _Alocasia_, _Caladium_, _Taccarum_,
_Syngonium_). A remarkable spadix is found in _Spathicarpa_; it is
united for its entire length, on one side, with the spathe, and the
flowers are arranged upon it in rows, the ♀ to the outside, and the
♂ in the middle (_Zostera_ has a similar one).--_Pistia_ similarly
deviates considerably, it is a floating water-plant, with hairy, round
rosettes of leaves; in it also the spathe and spadix are united; at the
base a ♀-flower is borne, which consists of one unilocular ovary, and
above several ♂-flowers, each composed of two united stamens.~

   BIOLOGY. The inflorescences are adapted for
   _insect-pollination_; they are protogynous, since the viscous,
   almost sessile stigmas come to maturity and wither before the
   pollen, which is generally dehisced by apical pores, is shed;
   some pollinate themselves freely by the pollen from the higher
   ♂-flowers falling upon the ♀-flowers below them, and in some
   it is conjectured that the pollination is effected by snails.
   The coloured spathe, and the naked end of the spadix (often
   coloured) of certain genera function as the coloured perianth in
   other orders; during flowering a very powerful smell is often
   emitted. _Arum maculatum_ is worthy of notice; small flies
   and midges creep down into the spathe, between the sterile
   flowers (Fig. 301 _b_), which are situated where the spathe is
   constricted, and pointing obliquely downwards prevent the escape
   of the insects; in the meantime, the stigmas are in a condition
   to receive any pollen they may have brought with them; after
   pollination the stigmas wither, and exude small drops of honey
   as a compensation to the flies for their imprisonment; after
   this the anthers (_m_) open and shed their pollen, the sterile
   flowers wither, and the insects are then able to escape, and
   enter and pollinate other inflorescences.--In many, a _rise
   of temperature_ and evolution of carbonic acid takes place
   during flowering; a spadix may be raised as much as 30°C. above
   the temperature of the surrounding air.--Again, under certain
   conditions, many species absorb such large quantities of water
   by their roots that water is forced out in drops from the tip of
   the leaf; this may often be observed in _Zantedeschia_.

   About 900 species in 100 genera. Home, the Tropics, especially
   S. America, India, and the Indian Islands, preferably in shady,
   damp forests growing as epiphytes upon trees, and on the banks
   of streams. Outside the Tropics few are found. _Acorus calamus_
   was introduced into Europe from Asia about 300 years ago; it,
   however, never sets any fruit, as the pollen is unfertile. In
   England _Arum maculatum_ is a very common plant; this and _A.
   italicum_ are the only native species. _Colocasia antiquorum_
   comes from Polynesia and the Indian Islands, and also _Alocasia
   macrorrhiza_. Fossils in Cretaceous and Tertiary.

   USES. Many species have pungent, and even _poisonous properties_
   (_e.g. Dieffenbachia_, _Lagenandra_, _Arum_), which are easily
   removed by boiling or roasting; the _rhizomes_ of many species
   of _Caladium_, _Colocasia_ (_C. antiquorum_, _esculenta_, etc.),
   are very rich in starch, and in the Tropics form an important
   source of food. An uncommon occurrence in the order is the
   highly aromatic rhizome of _Acorus calamus_; this contains
   calamus-oil and acorin which are used in perfumery. Many are
   ornamental plants, _e.g. Zantedeschia æthiopica_ (South Africa),
   generally known as “Calla,” and _Monstera deliciosa_; many other
   species are grown in greenhouses.

Order 6. =Lemnaceæ (Duck-weeds).= These are the most reduced form of
the Spadicifloræ. They are very small, free-swimming water-plants.
The vegetative system resembles a small, leaf-like body (Fig. 303
_f-f_), from which roots hang downwards; this branches by producing a
new, similar leaf-like body, which springs from a pocket-like hollow
(indicated by a dotted line in the figure) on each side of the
older one, at its base (or only on one side). ~The branching is thus
dichasial or helicoid (Fig. 303 _A_, where _f, f′, f″, f″′_ indicate
shoots of 1st, 2nd, 3rd, 4th generations respectively). The leaf-like
bodies are, according to Hegelmaier, leaf-like stems, and thus _Lemna_
has no other leaves than the spathe and the sporophylls; according
to the investigations of Engler they are stems whose upper portion
(above the “pocket”) is a leaf, which is not sharply separated from
the underlying stem-portion. The inflorescence is a very much reduced
Araceous-spadix, consisting in _Lemna_ of 1 or 2 stamens of unequal
length (1-stamened ♂-flowers), 1 unilocular carpel (♀-flower), and
1 thin spathe (_B_). [The same is found in _Spirodela polyrrhiza_,
etc., whose daughter-shoots begin in addition with 1 basal-leaf.
_Wolffia arrhiza_, etc., have no roots, no spathe, and only 1 ♂-flower
in the inflorescence (Engler).]--On the germination of the seed a
portion of the testa is thrown off as a lid, so that an exit is opened
for the radicle.--19 species. In stagnant fresh water, both Temp.
and Tropical.--In Europe the species are _Lemna minor, trisulca,
gibba; Spirodela polyrrhiza_, and _Wolffia arrhiza_, the smallest
Flowering-plant.~

  [Illustration: FIG. 303.--_Lemna_: _A_ vegetative system; _B_
  portion of a plant with flowers; one stamen and tip of the carpel
  project; the remaining portions being indicated by the dotted
  line.]


                      Family 4. =Enantioblastæ.=

The flowers in this family are _hypogynous_ and have in part the
general monocotyledonous type with 5 trimerous whorls completely
developed in a regular hermaphrodite flower, and in part the flowers
so much reduced that the type is very difficult to trace. On the one
hand the family is well developed and has capitate inflorescences
(_Eriocaulaceæ_) and on the other hand it is distinctly reduced
(_Centrolepidaceceæ_). This family has taken its name from the fact
that the ovule is not, as in the Liliifloræ and nearly all other
Monocotyledons, anatropous, but _orthotropous_, so that the embryo
(βλάστη) becomes placed _at the end of the seed opposite_ (ἐναντίος)
_to the hilum_. Large, mealy endosperm.--The orders belonging to this
family are by certain authors grouped with the _Bromeliaceæ_ and
_Pontederiaceæ_, etc., into one family, FARINOSEÆ, so named on account
of the mealy endosperm, the distinguishing character of the Liliifloræ
then being that the endosperm is fleshy and horny.

   Order 1. =Commelinaceæ.= The complete Liliaceous structure
   without great reductions in the number of whorls, but with
   generally few ovules in each loculus of the ovary, is found in
   the Commelinaceæ, an almost exclusively tropical order with
   about 317 species; herbs, some of which are introduced into
   our gardens and greenhouses. The stems are nodose; the leaves
   often _clasping_; the flowers are arranged in unipared scorpioid
   cymes, often so that they form a zig-zag series falling in
   the median line of the bracts, and after flowering they bend
   regularly to the right or left, outwards or inwards. They
   are more or less _zygomorphic_, particularly in the stamens,
   which in the same flower are of different forms or partially
   suppressed. The outer series of the _perianth_ is sepaloid,
   the inner petaloid, generally violet or blue; the filaments
   are sometimes clothed with hairs formed of rows of bead-like
   cells (well known for showing protoplasmic movements). Fruit
   a trilocular _capsule_ with loculicidal dehiscence (generally
   few-seeded); in some a nut. The radicle is covered by an
   external, warty, projecting covering which is cast off on
   germination.--The abundant raphides lie in elongated cells whose
   transverse walls they perforate.--_Commelina, Tradescantia,
   Tinantia, Cyanotis, Dichorisandra_.

   Order 2. =Mayacaceæ.= This order is closely allied to the
   Commelinaceæ. 7 species. American marsh- or water-plants.

   In many of the following orders of this family the flowers are
   united into compound inflorescences, with which is accompanied a
   reduction in the flower.

   Order 3. =Xyridaceæ= (50 species). Marsh-plants with radical,
   often equitant leaves arranged in 2 rows, and short spikes on
   long (twisted) stalks. The flowers, as in the Commelinaceæ, have
   sepals (which however are more chaffy) and petals, but the outer
   series of stamens is wanting. Capsule (generally many-seeded).

   Order 4. =Rapateaceæ.= Marsh-plants with radical leaves, usually
   in two rows, and several spikelets on the summit of the main
   axis, clustered into a capitulum or unilateral spike. Each
   spikelet has numerous imbricate floral-leaves and one flower. 24
   species. South America.

   Order 5. =Eriocaulaceæ.= The “Compositæ among Monocotyledons,”
   a tropical order. The flowers are borne in a _capitulum_
   surrounded by an _involucre_, very similar to that of the
   Compositæ. The flowers are very small, unisexual, ♂ and ♀
   often mixed indiscriminately in the same capitulum; they have
   the usual pentacyclic structure; the leaves of the inner
   perianth are often connate and more membranous than the outer;
   in some the outer series of stamens are suppressed; in each of
   the 3 loculi is one pendulous ovule. Capsule. The leaves are
   generally radical and grass-like.--335 species; _Eriocaulon_,
   _Paepalanthus_, etc., _E. septangulare_ on the west coast of
   Scotland, and Ireland, and in North America.

   Order 6. =Restiaceæ.= A small, especially S. African and S.
   Australian, xerophilous order (about 235 species), which is
   quite similar in habit to the Juncaceæ and Cyperaceæ. The
   leaves are often reduced to sheaths. The flowers are diœcious,
   the perianth as in _Juncus_, but the outer series of stamens
   suppressed. The ovary and fruit as in Eriocaulaceæ; the ovary,
   however, may be unilocular, and the fruit a nut. _Restio_, etc.

   Order 7. =Centrolepidaceæ.= These are the most reduced plants
   in the family; small grass- or rush-like herbs. The flowers
   are very small, naked. Stamens 1–2, carpels 1–∞. 32 species.
   Australia.--_Centrolepis_ (flowers generally ☿ with 1 stamen and
   2–∞ carpels).


                        Family 5. =Liliifloræ.=

The flower is constructed on the general monocotyledonous type, with 5
alternating, 3-merous whorls (Fig. 278), but exceptions are found as
in the Iridaceæ (Fig. 279) by the suppression of the _inner_ whorl of
stamens; in a few the position in relation to the bract differs from
that represented in Fig. 278, and in some instead of the trimerous,
di- or tetramerous flowers are found (_e.g. Majanthemum_, _Paris_).
Flowers generally _regular, hermaphrodite_, with simple, _petaloid_,
coloured perianth (except, for example, Bromeliaceæ); ovary trilocular,
generally with 2 ovules or 2 rows of ovules in the inner angle of
each loculus (Fig. 304 _C_, _D_). _Endosperm_ always present.--A very
natural family, of which some divisions in part overlap each other.
The habit varies; the leaves are however long, entire, with parallel
venation, except in Dioscoreaceæ (Fig. 313).

   In the first orders of this family the flowers are hypogynous,
   and in the first of all the styles are free, and the capsule
   dehisces septicidally; in the following the flowers are
   epigynous and in some reduced in number or unisexual; capsule
   with loculicidal dehiscence, or a berry.

   HYPOGYNOUS flowers: Colchicaceæ, Liliaceæ, Convallariaceæ,
   Bromeliaceæ (in part).

   EPIGYNOUS flowers: Amaryllidaceæ, Iridaceæ, Bromeliaceæ (in
   part), Dioscoreaceæ.

Order 1. =Colchicaceæ.= The flower (Fig. 304 _A_) is ☿, regular,
_hypogynous_, trimerous in all five whorls (6 _stamens_); anthers
usually _extrorse_. Gynœceum with 3 _free styles_ (_A, D_); fruit a
_capsule with septicidal dehiscence_ (_E_); embryo very small (_F_).
The underground stem is generally a corm or rhizome, seldom a bulb.

=A.= VERATREÆ.--_Veratrum_; perennial herbs, stem tall with long
internodes and broad, folded leaves; the flowers andromonœcious,
with free, widely opening perianth-leaves (Fig. 304 _A_), and
globular anthers; inflorescence a panicle.--_Zygadenus, Melanthium,
Schœnocaulon, Uvularia, Tricyrtis_.

=B.= TOFIELDIEÆ.--_Narthecium_ and _Tofieldia_ have leaves alternate
(arranged in two rows), sword-like and borne in rosettes; racemes
or spikes. _Narthecium_ forms an exception to the order by having
a simple style and fruit with loculicidal dehiscence; _Tofieldia_
by the introrse anthers. In this they are related to the Liliaceæ.
_Narthecium_ has poisonous properties, like many other Colchicaceæ.

  [Illustration: FIG. 304.--_Veratrum_: _A_ flower; _B_ stamen;
  _C_ transverse section of ovary; _D_ gynœceum, with one carpel
  bisected longitudinally, and the third removed; _E_ fruit after
  dehiscence; _F_ longitudinal section of a seed.]

=C.= COLCHICEÆ.--_Colchicum_ (Autumn Crocus); perennial herbs, with a
long, _funnel-shaped, gamophyllous perianth_, and introrse anthers. The
flowers of _C. autumnale_ spring up immediately from the underground
stem, which is in reality a _corm_ formed of one internode. ~_Colchicum
autumnale_ flowers in autumn without leaves; in spring the radical
foliage-leaves appear simultaneously with the fruit. The flower is
protogynous, and is pollinated by insects (humble-bees, etc.) which
seek the honey secreted by the free part of the stamen a little way
down the tube. The length of the tube protects the fruit, and not,
as in other cases, the nectary.--_Bulbocodium_ and _Merendera_ have
unguiculate perianth-leaves, free, but closing together like a tube.~

   175 species; chiefly in North America and South Africa.
   _Tofieldia_ is an Arctic plant. The order is rich in pungent,
   poisonous alkaloids (veratrin, colchicin, etc.). OFFICINAL;
   the seeds of _Colchicum autumnale_ (Europe) and _Schœnocaulon
   officinale_ (Mexico), and the rhizome of _Veratrum album_
   (mountains of Central Europe).

  [Illustration: FIG. 305.--_Colchicum autumnale. A_ Corm
  seen from the front: _k_ corm; _s′ s″_ scale-leaves embracing
  the flower-stalk; _wh_ base of flower-stalk with roots (_w_).
  _B_ Longitudinal section of corm and flower-stalk: _hh_ brown
  membrane surrounding the underground portion of the plant;
  _st_ flower-and leaf-stalk of previous year, the swollen basal
  portion forming the reservoir of reserve material. The new plant
  is a lateral shoot from the base of the corm (_k_) and has the
  following parts: the base bearing the roots (_w_), the central
  part (_k’_) which becomes the corm in the next year, the axis
  bearing the scale-leaves (_s’, s″_), the foliage-leaves (_l,
  l′″_), and the flowers (_b, b’_) which are borne in the axils of
  the uppermost foliage-leaves.]

Order 2. =Liliaceæ (Lilies).= Flowers as in the Colchicaceæ but with
_introrse_ anthers; _ovary free, 3-locular, with single style; capsule_
3-locular with _loculicidal_ dehiscence.--The majority are herbs with
_bulbs_; the inflorescence is _terminal_. In many species reproduction
takes place by means of bulbils (small bulbs) formed in the axils of
the foliage-leaves (_e.g. Lilium bulbiferum_, _lancifolium_, etc.,
_Gagea lancifolia_, etc.), or in the bracts of the inflorescence (many
species of _Allium_); in many species several buds are developed as
bulbs in the axils of the bulb-scales themselves (accessory buds
arising close together), and in some the formation of buds is common on
the leaves.

=A.= TULIPEÆ, TULIP GROUP. Bulbs. The aerial, elongated stem bears
the foliage-leaves. Flowers few but generally large, with free
perianth-leaves. _Tulipa_; style absent, no honey; flowers generally
solitary, erect.--_Fritillaria_ perianth campanulate with a round or
oblong nectary at the base of each perianth-leaf.--_Lilium_; perianth
widely open, generally turned back with a covered nectary-groove in the
centre of each segment. Anthers versatile.--_Lloydia; Erythronium._

=B.= HYACINTHEÆ, HYACINTH GROUP. Bulbs. Leaves radical; aerial stem
leafless with raceme or spike. In some the perianth-segments are free,
in others united. Honey is produced often in glands or in the septa of
the ovary (septal glands).--_Ornithogalum_ has a leafy stem; _Scilla_;
_Eucomis_ has a tuft of floral-leaves above the raceme; _Agraphis_;
_Hyacinthus_; _Puschkinia_; _Chionodoxa_; _Muscari_; _Veltheimia_;
_Urginea_.

=C.= ALLIEÆ, ONION GROUP. Generally bulbs. Leaves radical. Stem
leafless with a compound umbellate or capitate inflorescence of
unipared helicoid cymes, which before flowering are surrounded
by two broad involucral leaves.--~_Allium._ Filaments often
petaloid and bidentate; in many species bulbils are found in the
inflorescence.--Some species have flat leaves: _A. sativum_, Garlic;
_A. porrum_, Leek; _A. ursinum_; others have round, hollow leaves:
_A. cepa_, Onion; _A. fistulosum_, Winter Onion; _A. ascalonicum_,
Eschalot; _A. schænoprasum_, Chive.~--_Gagea_; honey is secreted
at the base of the perianth, no special nectary; inflorescence
few-flowered.--_Agapanthus; Triteleia._

   =D.= ANTHERICEÆ. Rhizome; raceme; the leaves not fleshy and
   thick.--_Anthericum_; _Asphodelus_; _Bulbine_; _Chlorophytum_;
   _Bowiea_ has an almost leafless stem with curved, climbing
   branches.

   =E.= ALOINEÆ, ALOES. Stem generally aerial and tree-like,
   bearing on its summit thick, fleshy leaves, often with a thorny
   edge (Fig. 306). Raceme branched or unbranched.--_Aloë_;
   _Gasteria_; _Yucca_ (has secondary thickening, p. 274).

   =F.= HEMEROCALLIDEÆ. _Phormium_, (_Ph. tenax._ New Zealand
   Flax); _Funckia_ (_Hosta_); _Hemerocallis_.

   At this point the following are best placed: _Aphyllanthes_
   (_A. monspeliensis_); _Xanthorrhæa_ (Black-boy); _Xerotes_;
   _Lomandra_; _Kingia_; the very membranous, dry perianth of the
   last resembles that of the Juncaceæ, and also there are only
   1–few ovules in the loculi.

   POLLINATION by insects. Honey in some is produced on the
   perianth (see Tulipeæ), in others by glands on the carpels (in
   the septa and parietal placentæ, septal glands): _Hyacinthus_,
   _Allium_, _Anthericum_, _Asphodelus_, _Yucca_, _Funckia_,
   _Hemerocallis_, etc. Some _Allium_-species are protandrous.
   _Fritillaria_ is visited by bees, _Lilium martagon_ by moths,
   _L. bulbiferum_ by butterflies, _Phormium_ (New Zealand) by
   honey-birds.

  [Illustration: FIG. 306.--Aloë.]

   About 1,580 species; rare in cold climates; their home is in
   sunny plains with firm, hard soil, and warm or mild climate,
   particularly in the Old World (S. Africa; As. Steppes;
   Mediterranean); at the commencement of spring the flowers
   appear in great profusion, and after the course of a few weeks
   disappear; during the hot season their life lies dormant in the
   bulb, hidden underground. The woody species are tropical.--The
   majority of the _introduced_ Liliaceæ (_Fritillaria imperialis_,
   Crown-imperial; _Lilium candidum_; _Tulipa gesneriana_;
   Hyacinth; _Muscari_-species; _Scilla_-species; _Ornithogalum
   nutans_; _Hemerocallis fulva_ and _flava_; _Asphodelus luteus_
   and _albus_) come from the Mediterranean and W. Asia; _Funckia_
   from China and Japan; several Lilies from Japan and the
   Himalayas; _Agapanthus_ from the Cape; _Allium sativum_ is a
   native of the Kerghis-Steppes; _A. cepa_ from Persia (?); _A.
   ascalonicum_ is not known wild (according to others a native of
   Asia Minor), perhaps a form of _A. cepa_; _A. schænoprasum_ from
   the N. temp. region.

   Many bulbs have pungent properties; many Onions are used as
   culinary plants. The bast fibres of _Phormium tenax_ (New
   Zealand Flax) are used technically. Dyes are obtained from the
   _Aloe_; gum for varnish from the stem of _Xanthorrhæa hostile_
   and _australe_. OFFICINAL; “Aloes,” the dried sap of S. African
   species of _Aloe_ (_A. Africana_, _A. ferox_, etc.); the
   bulb known as “Squills” from _Urginea_ (_Scilla_) _maritima_
   (Mediterranean).

Order 3. =Convallariaceæ.= This order differs from the Liliaceæ in
having the _fruit a berry_ (Fig. 308) and _in never being bulbous_; the
seeds are less numerous.

=A.= CONVALLARIEÆ, LILY OF THE VALLEY GROUP. Rhizome (Fig. 307) and
normal foliage-leaves.--_Polygonatum_: rhizome creeping; aerial
shoot leafy, bearing the flowers in racemes in the axils of the
foliage-leaves; perianth tubular. _P. multiflorum_ (Solomon’s seal),
_P. officinale_, etc.--_Majanthemum_: flower 2-merous; perianth
almost polyphyllous, spreading. _Smilacina. Streptopus_ (_S.
amplexifolius_; the flowers or inflorescence unite with the entire
succeeding internode).--_Convallaria_ (1 species _C. majalis_, Lily
of the valley); flowers in terminal racemes; 2 basal foliage-leaves;
perianth globose, bell-shaped. _Reineckea carnea_ (Japan, China) in
gardens.--_Paris_ (_P. quadrifolia_, Herb-Paris); flowers solitary,
terminal, 4-merous, polyphyllous; styles 4, free (approaching the
Colchicaceæ; it is also poisonous); a whorl of 4 (-more) 3-nerved,
reticulate leaves on each shoot.--Ornamental plants: species of
_Trillium_, _Aspidistra elatior_ (Japan).

  [Illustration: FIG. 307.--Rhizome of _Polygonatum multiflorum_:
  _a_ bud; _b_ shoot; _c d_ scars left by shoots of previous
  years.]

  [Illustration: FIG. 308.--_Smilax pseudosyphilitica_: _A_ shoot
  of male plant; _C_ ♂-flower; _D_ berry, almost ripe; _E_ the same
  in longitudinal section. _B Smilax syphilitica_: portion of
  branch with base of leaf and tendrils.]

=B.= ASPARAGEÆ, ASPARAGUS GROUP. Scale-like leaves and green
assimilating branches.--_Asparagus_: horizontal rhizome. The aerial
shoots are very richly branched; the numerous needle-like bodies upon
the plant are _leafless shoots_, which are crowded together in double
scorpioid cymes in the axils of the scale-leaves; the two first lateral
axes, placed outside to the left and right, generally bear flowers.
Polygamous.--~_Ruscus_ (Butcher’s broom) is a S. European _shrub_ with
_leaf-like_, ovoid or elliptical shoots (phylloclades) which are borne
in the axils of scale-like leaves, and bear flowers on the central
line. Diœcious. Stamens 3, united, anthers extrorse. _Semele androgyna_
bears its flowers on the edge of the flat shoot.~

=C.= SMILACEÆ. _Smilax_ (Sarsaparilla) (Fig. 308); _climbing_
shrubs with the leaf-sheath produced into tendrils. The leaves have
3–5 strong nerves proceeding from the base, and are reticulate.
Orthotropous or semi-anatropous ovules. Diœcious (Fig. 308 _C_, _E_).

   =D.= DRACÆNEÆ. Fruit in some a berry, in others a capsule.
   The stem of DRACÆNA, when old, has the appearance of being
   dichotomously branched; it has the power of increase in
   thickness, and may become enormously thick. The Dragon-tree of
   Teneriffe, measured by Humboldt, attained a circumference of
   14 m. and a height of 22 m.; the leaves are large, linear or
   linear-lanceolate.--_Cordyline_ (East Asia), various species in
   gardens and greenhouses (_Yucca_ is closely allied). _Astelia._

   POLLINATION. _Paris quadrifolia_ and _Convallaria majalis_
   have no honey, and are chiefly visited by pollen-collecting
   bees (in the absence of insect visits self-pollination takes
   place); _Polygonatum multiflorum_ has honey secreted by septal
   glands and protected by the base of the tubular perianth; it
   is pollinated by humble-bees, etc. _Asparagus officinalis_ has
   small, polygamous, greenish, honey-bearing flowers; the ♂-flower
   is almost twice as large as the ♀; both have rudiments of the
   opposite sex.

   About 555 species; especially from N. America, Europe, and
   Central Asia.

   OFFICINAL: “Dragons’-blood,” a red resinous juice from the stem
   of _Dracæna_ and the roots of some Central American species of
   _Smilax_. The tuberous stems of the Eastern Asiatic _Smilax
   glabra_ are officinal. The flowers of _Convallaria majalis_
   have been lately used as a substitute for _Digitalis_. Pungent,
   poisonous properties are possessed by _Paris_. None of the
   species are used as food, except the young annual shoots of
   _Asparagus officinalis_, a shore-plant which is used as a
   vegetable.

   Order 4. =Pontederiaceæ.= Flowers generally zygomorphic,
   hypogynous, ☿, with handsome, white or violet, petaloid perianth
   which forms a tube at its base. The stamens are inserted at
   different heights in the perianth-tube, and are reduced to
   three (in _Heteranthera_ seldom to one). In some the ovary is
   trilocular with ∞ ovules (_Eichhornia_), in others reduced to
   one loculus with one ovule (_Pontederia_). Fruit a capsule or
   nut. Embryo as long as the abundant, mealy endosperm.--Tropical
   water-plants (22 species) with peculiar sympodial branching,
   nearly the same as in _Zostera_. Spikes without floral-leaves.
   Many intercellular spaces in the stem and leaf.--In greenhouses:
   _Eichhornia azurea_, _E. crassipes_ (both from tropical and
   sub-tropical S. America); the latter has swollen petioles which
   serve as floats and enable it to float freely on the water,
   sending down its roots into the mud. _Heteranthera reniformis,
   H. zosterifolia. Pontederia cordata._

Order 5. =Amaryllidaceæ (Narcissi).= The flower is _epigynous_,
otherwise exactly the same as in the Liliaceæ (6 stamens). The
majority, like these, are also _perennial_ herbs with bulbs and scapes.
The fruit and the other characters as in the Liliaceæ. The external
appearance is, however, very different.

=A.= AMARYLLEÆ have bulbs and the leaves generally arranged in two
rows; the flowers are borne singly or in umbel-like inflorescences
on lateral scapes, while the main axis of the bulb is unlimited.
Beneath the inflorescence is an _involucre_ (Fig. 309).--_Galanthus_,
Snowdrop, has a polyphyllous perianth without corona; the three inner
perianth-leaves are emarginate and shorter than the outer; the anthers
dehisce apically. ~_Leucojum_ differs in having the perianth-leaves
equal in length.--_Amaryllis_ has a funnel-shaped perianth, entirely
or nearly polyphyllous, but somewhat zygomorphic. _Crinum; Hæmanthus;
Clivia._~--_Narcissus_ has a tubular _corona_, a ligular structure
arising from the perianth-tube exterior to the outer stamens. ~In
_Pancratium_ (Fig. 309) the corona is united with the filaments which
appear to spring from its edge. _Eucharis amazonica._~

  [Illustration: FIG. 309.--_Pancratium caribæum._]

   =B.= HYPOXIDEÆ. The leaves, which are grass-like, dry, folded,
   and in some hairy, spring from a rhizome, generally with a
   divergence of 1/3. Flowers small, perianth polyphyllous,
   persistent, on which account perhaps the Hypoxideæ may be
   considered as the least altered type. The chief characteristic
   is that the embryo is separated from the hilum. _Hypoxis_;
   _Curculigo_ (_C. recurvata_, a favourite ornamental plant; S.E.
   Asia).

   =C.= ALSTRŒMERIEÆ. (_Alstrœmeria_, _Bomarea_); stems long,
   leafy, often climbing.

   =D.= VELLOSIEÆ (_Vellosia_, _Barbacenia_); stem woody, usually
   dichotomously branched, with terminal, single flowers; it bears
   numerous aerial roots which pierce the leaves and surround the
   stem. Stamens often (by splitting) 6–18. High table-lands of S.
   America and S. Africa.

   =E.= AGAVEÆ. Very similar to the Bromeliaceæ both in their
   distribution (nearly all American) and in external appearance.
   They appear as gigantic bulbous plants with perennial, aerial,
   generally short stem, and perennial, large, lanceolate or
   linear, stiff, thick, and often thorny leaves, which form a
   large rosette; after the course of several (8–20) years the
   terminal inflorescence is developed, which is 10–12 m. high,
   paniculate, and freely branched. Before the inflorescence
   expands, a large quantity of sugar-containing sap is collected
   from _A. americana_ by removing the terminal bud; this on
   distillation yields “pulque,” the national drink of Mexico.
   After flowering the entire shoot dies, but the subterranean
   lateral shoots survive and reproduce the plant.--_Agave
   americana_, etc.; _Fourcroya_; _Polianthes tuberosa_ (Tuberose;
   Central America).

   DISTRIBUTION. The 650 species are chiefly natives of S. Africa
   and S. America. _Clivia_, _Hæmanthus_, _Amaryllis_ are from the
   Cape; _Narcissus_ from S. Europe, whence many species have been
   introduced; _Galanthus_ and _Leucojum_ are especially from S.
   and Central Europe, and from the Caucasus.

   USES, few, except as ornamental plants: _Galanthus nivalis_;
   _Leucojum_; _Narcissus pseudonarcissus_, _N. poeticus_, _N.
   jonquilla_, _N. tazetta_, etc.; _Amaryllis_, _Alstrœmeria_,
   _Eucharis_, _Crinum_, _Vallota_, etc. The vascular bundles of
   the various species of _Agave_ (_Agave rigida_, var. _sisalana_,
   sisal hemp,) are used for cordage, etc.

Order 6. =Bromeliaceæ.= The flowers are hypogynous, epigynous or
semi-epigynous; the perianth is divided into _calyx_ and _corolla_;
stamens 6. The fruit is a capsule or berry with many seeds. Endosperm
_mealy_, embryo small, at the edge of the endosperm, but not enclosed
by it.

  [Illustration: FIG. 310.--_Aechmea miniata._]

  [Illustration: FIG. 311.--Multiple-fruit of _Ananassa sativa_.]

Perennial herbs with a very _characteristic appearance_ (Fig. 310);
the stem is most often short, thick, and crowned by a _rosette_ of
many leaves, which are long, often very narrow, _leathery_, stiff, and
with a _spiny_ edge; they are usually channeled, completely closing
round each other, with their edges forming a tightly closed hollow, in
which generally water is collected (this among other things insulates
the inflorescence and thus prevents the access of creeping insects,
such as ants). The presence of numerous stellate, water-containing
hairs often gives the leaves a grey appearance, and the layers of
cells beneath the upper epidermis of the lamina form an “aqueous
tissue,” which serves as a protection against the rays of the sun and
regulates the evaporation. The stomata are often situated in furrows
on the underside of the leaf, and hence cause a striped appearance.
They _are all American_ (525 species), especially from S. America,
where they live partly as epiphytes _on trees_, partly in the _clefts
of rocks_, often on the steepest slopes, to which they firmly attach
themselves by aerial roots; some are terrestrial. The stem is seldom
tree-like or many metres in height (_Puya_, in Chili; _Hechtia_, in
Mexico). _The inflorescence_ is a terminal spike, raceme, or panicle,
often with large and brightly-coloured floral-leaves. The flowers are
without scent. The seeds, in the species whose fruit is a capsule,
are often provided with wings (hairs, expansions, etc).--_Ananassa
sativa_, Pine-apple (W. Indies, Central America) is cultivated for the
sake of its juicy, aromatic fruits, which coalesce with their fleshy
bracts and form a large spike-like fruit-cluster (multiple-fruits,[29]
Fig. 311) bearing on its apex a leafy shoot, which may be used as a
cutting. Seeds very rarely developed.--_Tillandsia_ (_T. usneoides_ is
a filamentous, richly branched, rootless epiphyte hanging in masses
from trees; Trop. Am.), _Aechmea_, _Billbergia_, _Pitcairnia_, etc.

   USES. The leaves of the Pine-apple, in its native country, are
   used for the manufacture of cloth.

   Order 7. =Hæmodoraceæ.= 120 species; in all parts of the world
   except Europe; perennial, often tomentose and resembling
   the Bromeliaceæ, Iridaceæ and Amaryllidaceæ. _Hæmodorum_
   (Australia).--To this order belong _Ophiopogon_, _Peliosanthes_,
   _Sanseviera_, and others.

Order 8. The =Iridaceæ= have _epigynous_, hermaphrodite flowers with
petaloid perianth as in the Amaryllidaceæ, but the _interior whorl of
stamens is entirely suppressed_, and the 3 developed _outer_ stamens
have _extrorse_ anthers (Fig. 279); there is 1 style with 3 large,
generally _more or less leaf-like branches bearing the stigmas_.
Ovary and capsule as in the Amaryllidaceæ and Liliaceæ.--Perennial
herbs; _bulbs are rarely found_, but horizontal rhizomes, corms, etc.,
take their place. The leaves are (except _Crocus_) as in the _Iris_,
_two-rowed_, _equitant_ and _sword-like_. Flowers or inflorescences
terminal.

The _Iris_ (Flag) has a horizontal rhizome. The flowers are borne in
the leaf-axils in fan-like inflorescences (rhipidium). The branches of
the style are large and _petaloid_; on their under surface may be seen
a small projecting shelf (Fig. 312 _a_) having on its upper surface the
stigmatic hairs. Beneath the branches of the style are 3 well protected
stamens, and immediately outside these the external perianth-leaves.
~The honey is secreted in the perianth-tube, and the insects,
endeavouring to obtain it through the narrow passages at the base of
the stamens, settle upon the outer perianth-leaves, which are bent
backwards and often very hairy along their central line. The insects
then rub their backs on the anthers just above them, beneath the
branches of the style; they readily deposit the pollen on the stigma
of another flower as they enter it, but cannot do so in withdrawing,
since the stigma is pushed back, and self-fertilisation is thus
avoided. The stylar branches lie close to the outer perianth-leaves,
which are just beneath them, or separated by a distance of only 6–10
mm.; the first form of flower is adapted for _Rhingia rostrata_, the
latter for bees~.--_Crocus_ has vertical, _tuberous_, underground stems
surrounded by the leaf-sheaths (corms), and terminal flowers; the
linear leaves _are not equitant_, but have two longitudinal furrows
on the under side. The perianth is gamophyllous and funnel-shaped.
The stylar branches (stigmas) are fleshy, _rolled together in the
shape of a horn_, and split along the edge.--_Gladiolus_ has corms
like the _Crocus_; spikes with slightly zygomorphic, almost bilabiate
flowers, most frequently turning to one side. Position of the leaves
as in the Iris.--~_Diplarrhena_ has 2 fertile and 1 barren stamen;
_Hermodactylus_ has a unilocular ovary with 3 parietal placentæ.
_Cypella_ and _Tigridia_ have bulbs.~

  [Illustration: FIG. 312.--_Iris pseudacorus._ One external and
  two internal perianth-leaves, and one of the stylar-branches
  have been removed, _y_ The outer, _i_ the inner perianth-leaves;
  _g_ stylar-branch; _a_ stigma; _s_ anther. The ovary is seen in
  longitudinal section.]

   770 species; chiefly in the countries round the Mediterranean,
   and in Africa, especially the Cape (_Gladiolus_, _Ferraria_,
   _Moræa_, _Galaxia_, _Sparaxis_, _Antholyza_, _Tritonia_,
   _Ixia_, etc.), Australia and Tropical America (_Sisyrinchium_,
   _Tigridia_, _Cipura_, _Cypella_, etc). A great number are
   ornamental plants: the cultivated _Crocus_-species are from the
   South of Europe and Asia; _Gladiolus communis_ from S. Europe;
   the other species principally from S. Africa. The native species
   of _Iris_ are _I. pseudacorus_ (yellow) and _I. fœtidissima_.

   OFFICINAL: the stigmas of _Crocus sativus_ (Oriental, cultivated
   in France, Spain, Italy, and Austria), used as a colouring
   matter, saffron; the rhizomes of the S. European _Iris
   florentina_, _pallida_, and _germanica_ (“Orris-root”).

  [Illustration: FIG. 313.--_Dioscorea batatas_: _A_ ♂-plant; _B_
  ♂-flower; _C_ ♀-plant (nat. size); _D_, _E_ ♀-flowers (mag.); _F_
  seed; _G_ embryo.]

Order 9. =Dioscoreaceæ.= Perennial herbs with fleshy, often very large
_tuberous rhizomes_ (or roots); _twining_ stems; leaves stalked, often
arrow- or heart-shaped, lobed, _palminerved_ and _finely reticulate_
as in the Dicotyledons (Fig. 313). The flower is _diclinous_ (most
frequently _diœcious_), regular, _epigynous_, _small_, and of a
_greenish colour_, but otherwise typical (Pr3 + 3, and A3 + 3, or G3);
in most instances 2 ovules are placed one above the other in each
loculus. The inflorescence is a _spike_ or _raceme_, sometimes richly
branched and paniculate.--The order approaches most nearly to the
Amaryllidaceæ.

_Tamus_ (Bryony) has a berry, _Dioscorea_ (Yam) a thin-walled, 3-edged
or 3-winged capsule (Fig. 313). Both have subterranean or aerial
tubers; the Yam very often also developes tubers in the axils of the
foliage-leaves; tuberous roots are said to occur in _D. batatas_.
The tubers of many species of Yams (_D. batatas_ from China and
Japan, _D. alata_, South Sea Islands and India, _D. bulbifera_) are
a very important source of food in the Tropics, especially the
first-named.--_Testudinaria_; _Rajania_.--~The tuberous stem of
_Tamus communis_ and _Testudinaria elephantipes_, and some species
of _Dioscorea_ is formed from one single internode (epicotyl), and
the aerial shoots are developed from adventitious buds; in _T.
elephantipes_ the stem is aerial, and covered with thick scales of
cork, regularly arranged, and separated by grooves.~

   Tropical order (167 species); 2 species (_Tamus communis_ and
   _Borderea pyrenaica_) in Europe.


                        Family 6. =Scitamineæ.=

The flowers belong to the ordinary monocotyledonous type. They are
hermaphrodite, _epigynous_, and have either a petaloid perianth, or
calyx and corolla; they are, however, _zygomorphic_ or _unsymmetrical_,
and of the stamens most frequently only one is _completely developed_,
the others being generally represented by petaloid staminodes. The
ovary has 3 loculi, more rarely it is unilocular with the suppression
of 2 loculi. Endosperm is absent (except _Zingiberaceæ_); but, on the
other hand, there is a _large perisperm_. To this family belong large,
glabrous, especially _perennial herbs_ with rhizomes; leaves large,
distinctly divided into sheath, stalk, and blade, the latter being more
or less elliptical or lanceolate, entire, with pinnate venation, and
always with a very _well-pronounced midrib_, gradually tapering towards
the apex, and giving off numerous branches, which run outwards, towards
the margin, at a larger or smaller angle; these _lateral veins_ are
closely packed, and parallel, but with only weak, connecting branches
between them; the leaves, therefore, are easily torn pinnately (Figs.
314, 317). The leaf-sheaths close tightly round each other and form a
false stem.

This very natural family comprises orders closely connected with each
other, but is not itself nearly allied to any other family. First in
the series stands:--

Order 1. =Musaceæ.= The _petaloid_ perianth is strongly zygomorphic,
the anterior leaf being very large (a kind of “labellum”), the
posterior one small; only the posterior stamen is wanting, or is
rudimentary, the other five are developed, and have quadrilocular
anthers; ovary, 3-locular. Seed with straight embryo in mealy perisperm.

  [Illustration: FIG. 314.--Two _Musa_-species.]

The best-known genus is _Musa_, the Banana (Fig. 314). From the
short rhizome arise enormously large, spirally-placed leaves, whose
sheaths envelope one another, and form an apparently aerial stem,
several metres in height. The inflorescence is a terminal _spike_
with floral-leaves placed spirally, and sometimes magnificently
coloured; in the axils of each of these several flowers are situated
in two transverse rows (accessory buds); the lowest flowers in the
inflorescence are ♀, the central ones ☿, the upper ones ♂, so that
fruits are only found in the lower region of the inflorescence, the
remaining portion persisting as a naked axis after the floral-leaves
and flowers have fallen off; the inflorescence terminates in an ovoid
bud formed by the flowers which have not yet opened (Fig. 314, the
left-hand figure). The perianth-leaves are united (except the posterior
one). The fruit (known as a “Banana”) is a _berry_, having the form of
a smooth, short, three-cornered Cucumber (as much as 30 cm. in length);
inside the tough skin is found a farinaceous, aromatic pulp. No seed
is developed in the cultivated species.--~Several _Musa_-species are
cultivated in the Tropics for the sake of the fruit (_M. paradisiaca_,
_M. sapientum_); for the fibrovascular bundles, _M. textilis_ (Manilla
Hemp).--Their home is, no doubt, the Tropics of the Old World; they
were introduced into America before the arrival of Europeans. _Musa
ensete_ has dry, leathery fruits; an ornamental plant.~

   In _Musa_ the barren, posterior stamen belongs to the inner
   whorl; and also in _Strelitzia_ and _Ravenala_; the latter
   may have all 6 stamens developed. In _Heliconia_, on the
   contrary, it belongs to the outer whorl; in _Heliconia_ the
   perianth-leaves are differently arranged, and there is only
   one ovule in each loculus. The three latter genera have dry
   fruits and leaves arranged in two rows. In the “Travellers’
   Palm” (_Ravenala madagascariensis_) the foliage-leaves form an
   enormous fan.--Tropical; about 50 species.

The order may be divided as follows:--1. Museæ: _Musa_, _Ravenala_,
_Strelitzia_ in the Old World. 2. Heliconiæ: _Heliconia_ in the New
World.

  [Illustration: FIG. 315.--Diagram of a _Zingiberaceous_ flower
  (_Kæmpferia ovalifolia_): _b_ bract; _v_ bracteole; _k_ calyx;
  _p^1_, _p^2_, _p^3_ the petals; _sst_, lateral staminodes
  (“wings”); _lab_ labellum (formed of two staminodes); _st_ the
  fertile stamen; * position of suppressed stamen. The ovary is in
  the centre of the diagram.]

Order 2. =Zingiberaceæ.= Perianth most frequently divided into _calyx_
and _corolla_. Calyx gamosepalous. Only 1 _fertile stamen_ (the
posterior, Fig. 315, belonging to the inner whorl) with quadrilocular
anther, which encloses the style in a furrow; the 2 stamens in the
outer whorl are staminodes, the median one (the anterior) is wanting.
The 2 lateral staminodes of the inner whorl form the “labellum” (Fig.
315 _lab_), which usually is the largest segment of the flower, and
is often bilobed. Ovules many. The fruit in some is a leathery,
3-valved capsule, with loculicidal dehiscence; in others it is more or
less berry-like and indehiscent, or irregularly dehiscent. Straight
embryo.--The aerial stem is seldom developed to any extent, and the
inflorescences, which are (compound) spikes or racemes, often with
coloured floral-leaves, spring in some (_e.g. Zingiber officinale_)
directly from the rhizome. The leaves are arranged in two rows.--The
ovary in a few instances (_Globba_ and others) is unilocular, with 3
parietal placentæ.

   They are perennial herbs with fleshy and tuberous rhizomes,
   which are used as condiments and in medicine on account of their
   pungent and aromatic properties and also for starch, dyes, etc.
   OFFICINAL: _rhizomes_ of _Zingiber officinale_ (Ginger, unknown
   wild, but cultivated generally in the Tropics), of _Curcuma
   longa_ (Turmeric, a dye, E. India) and _C. zedoaria_, of _C.
   angustifolia_ and others (as E. India Arrowroot), of _Alpinia
   officinarum_, China (galangal). “Preserved Ginger” from _Alpinia
   galanga_. Similar aromatic materials (volatile oils) are present
   also, for example, in _the fruits_; Cardamom fruits and seeds
   (from _Elettaria cardamomum_, China, seldom from _E. major_).

   315 species; Tropics, preponderating in the Eastern Hemisphere,
   India, and especially S. Asia, whence all the aromatic
   species originate; they are now commonly cultivated in the
   Tropics. Some are ornamental plants in greenhouses, _e.g._
   _Hedychium_, _Costus_, etc. _Globba_ (with axillary buds in the
   inflorescence, as in _Ficaria_), _Renealmia_, _Kæmpferia_.

  [Illustration: FIG. 316.--Flower of _Canna_: _f_ ovary; _pa_
  calyx; _pi_ corolla; _l_ labellum; _st_ stamens; _an_ anther; _g_
  stigma; α and β staminodes.]

Order 3. =Cannaceæ.= American herbs without aromatic properties.
Flowers asymmetric (Fig. 316). Calyx polysepalous. The stamens are
_petaloid_ (Fig. 316 _st_) and barren with the exception of one (the
posterior), which bears on one of its _edges_ a bilocular anther;
another, which is especially large and coloured, is termed the
_labellum_. The style is compressed and leaf-like, with a small stigma
at the apex. Ovules numerous in the 3 loculi. The capsule is furnished
with warts or soft prickles. _Embryo straight._

_Canna_ (30 species; Trop. Am.). The inflorescence is a terminal
spike with 2-flowered unipared scorpioid cymes in the axils of the
floral-leaves. Ornamental plants: _Canna indica_, etc.

The diagram of the andrœcium of the Cannaceæ and Marantaceæ may be
represented in the following manner (calyx, corolla and gynœceum being
omitted):--

        CANNACEÆ.                 MARANTACEÆ.

    _w_            _w_        _w_             _w_
           _st_                       _st_
      _w_       _lab_           _wi_        _c_
            *                          *

   _w_ The lateral staminodes, “wings;” _st_ fertile stamen; * the
   suppressed stamen; _lab_ labellum; _c_ hood; _wi_ inner-wing.

   The labellum of the Cannaceæ corresponds with the hood of the
   Marantaceæ and not with the labellum of the Zingiberaceæ.

  [Illustration: FIG. 317.--_Calathea zebrina._]

Order 4. =Marantaceæ.= The flower is asymmetrical. Only 1 or 2 of the
3 stamens in the outer whorl are present as staminodes; in the inner
whorl 2 are petaloid and of the sixth stamen one-half is developed as a
staminode and the other half bears a bilocular anther. One ovule only
in each loculus. The style is strongly curved and at first enclosed
in one of the staminodes (hood) of the inner whorl; later on it
springs elastically forward towards the other staminode (inner-wing)
of the same whorl. The stigma is very oblique or 2-lipped. Two of the
three loculi of the ovary, in some (_Maranta_, _Thalia_) become small
and empty. Embryo _curved_. Leaves in two rows, with sheath, stalk,
and blade (Fig. 317); at the base of the last is a _characteristic
swelling_ (_articulus_).--~_Phrynium_, _Calathea_, _Stromanthe_,
_Ctenanthe_, _Saranthe_, etc. About 150 species; tropical, especially
America. The starch of the rhizome of _Maranta arundinacea_ is
OFFICINAL, “West Indian Arrowroot.”~


                         Family 7. =Gynandræ.=

The flowers are hermaphrodite and constructed on the ordinary 3-merous,
pentacyclic type with petaloid, _epigynous, strongly zygomorphic_
perianth, and generally _one-stamened_ by the suppression of the
other 5 stamens. The family has derived its name from the fact that
the stamen is united with the style into a “_stylar column_” (except
_Burmanniaceæ_). All are herbs; many grow as epiphytes on other plants.

   This family and the Scitamineæ occupy correspondingly high
   positions among the Monocotyledons; these two families may
   therefore be placed close together, although one cannot be
   derived from the other. The first of the two orders is very
   small, but the second is very rich in species. The Apostasieæ
   are best classed with the Orchidaceæ and have no independent
   place.

Order 1. =Burmanniaceæ.= This order forms a transitional link between
the Gynandræ and the epigynous Liliifloræ (_Amaryllidaceæ_), in having
a 6-leaved perianth, and 6–8 stamens; but some have a labiate perianth
(the median perianth-leaf of the _outer_ whorl being very large). The
ovary is most frequently unilocular with three parietal placentæ; but
in some it is 3-locular with axile placentation. Capsule. Seeds ∞,
small, with _endosperm_. The relationship to the Orchidaceæ is shown
especially in the very imperfectly developed embryo and in the ovary.
Small, tropical herbs (59 species); some are saprophytes.

  [Illustration: FIG. 318.--_A_ Diagram of an Orchid-flower. _B_,
  _Cephalanthera_. Stylar-column: _a_ anther; _s_ stigma; at the
  foot are seen scars indicating the position of the parts which
  have been removed.]

Order 2. =Orchidaceæ.= The epigynous, petaloid perianth is strongly
zygomorphic in having the _posterior_ leaf of the interior whorl, the
_lip_ (labellum), differing from all the other leaves in form, size,
and colour (except _Apostasieæ_); the position of the labellum is very
frequently reversed, being turned _forwards and downwards_ by the
twisting of the ovary (Fig. 318 _A_). _Only_ 1 of the stamens--the
anterior of the external whorl--is developed and bears an anther (by
the twisting of the ovary it is turned posteriorly and upwards);
the others are entirely wanting (indicated by * in Fig. 318 _A_)
or present as staminodes (Fig. 318 _A_, δ δ) (except _Apostasieæ_,
_Cypripedileæ_); the filaments are united with the style to form a
column (Fig. 318 _B_), the _stylar-column_[30] (_gynostemium_), and
the anther (_a_) is thus placed on its apex and exactly behind or over
the stigma (_s_). The anther is 4-locular; the pollen-grains do not
separate (except _Apostasieæ_, _Cypripedileæ_) but remain united either
in tetrads or in masses, which correspond to a pollen-mother-cell
(Fig. 320 _C_, _D_, _E_); or the pollen-grains, formed in each of
the two anther-halves, remain united and form one or a few wax-like
masses (pollen-masses, pollinia). The 3 carpels form a _unilocular
ovary_ with 3 parietal, deeply bifid placentæ (except _Apostasieæ_,
_Selenipedilum_). Only the two lateral carpels are prolonged and
developed into the stigma (Fig. 318 _B_, _s_), while the one lying in
the median line, which is situated just within the anther (Fig. 318
_A_), becomes either rudimentary or developed into the “_rostellum_”
(“a small beak”), on which the sticky bodies (_glandulæ_) arise; by
aid of these the heavy, connected pollen-masses may be glued to the
insects which visit the flower, and pollination is thus secured (in
_Apostasieæ_ and _Cypripedileæ_ the 3 carpels each contribute to the
formation of the stigma). The fruit is a _capsule_ which most often
dehisces _by 6 valves_, 3 of which are broader and bear the placentæ,
and 3 alternating with them are narrower and barren (except _Vanilla_).
The very numerous and exceedingly small seeds have _no endosperm_,
and have a somewhat _spherical embryo without any trace of external
organs_. The testa is membranous and loose.

The Orchids are _all perennial herbs_ with diverse habits and varying
morphological structure (see the genera); the leaves are scattered,
of the usual Liliaceous form, and the inflorescences in all cases are
_racemes or spikes_ (sometimes branched), with subtending bracts, but
without bracteoles.

The forms which are the least modified are described first.

=1.= APOSTASIEÆ. The perianth-leaves are almost alike and free. The
column is straight, with 3 equally-developed stigmas. _Neuwiedia_ has
3 perfect stamens (1 median of the outer whorl, and 2 lateral of the
inner whorl); _Apostasia_ has only 2 perfect (inner lateral) and one
barren (the median of the outer whorl), which however may be entirely
wanting. The 3 _posterior_ stamens are entirely suppressed. The pollen
is powdery. The ovary is 3-locular with axile placenta. 7 species
(Tropical East India, Australia).

  [Illustration: FIG. 319.--_Cypripedilum calceolus_: 1 front view
  of the flower; 2 lateral view, after the removal of all the
  perianth-leaves with the exception of the labellum, which has
  been divided longitudinally; 3 the stylar-column; _ov_ ovary;
  _s_-_s_ exterior, _p_ interior perianth; _p’_ the labellum; _a_
  the two fertile stamens; _a’_ the staminode; _st_ the stigma; _i_
  entrance for the insects; _ex_ exit.]

=2.= CYPRIPEDILEÆ.[31] The flower is strongly zygomorphic with a large
boat-shaped labellum. There are two perfect stamens belonging to the
_inner_ whorl, and the median anterior (later on the posterior) stamen
of the outer whorl is transformed into a large, barren, shield-shaped
body (Fig. 319). _Selenipedilum_ has a 3-locular ovary, but
_Cypripedilum_ (Ladies’-slipper) has a unilocular ovary with 3 parietal
placentæ--the typical structure for the Orchids. The pollen-grains
are _separate_ (not in tetrads) and all the 3 lobes of the stigma are
constructed to receive them. This group is therefore, next to the
Apostasieæ, the least modified among the Orchids; in all the following
groups, one of the lobes of the stigma is differently developed from
the others, and there is only one stamen.--Terrestial Orchids.--~The
pollination of _C. calceolus_ is effected by the forcible entrance of
insects into the boat-shaped labellum (Fig. 319 _p’_) at _i_, and their
escape at _ex_ (in 2) where the anthers are situated; in this way the
stigmas will first be touched and then the anthers. The pollen-grains
are surrounded by a sticky mass in order that they may adhere to the
insects.~

=3.= NEOTTIEÆ. The majority are terrestrial Orchids with creeping,
sympodial rhizomes; the blades of the leaves are not detached from the
stem at joints, and have convolute vernation. The anthers do not drop
off, but persist in the withered condition; their _apex_ is brought
in contact with the rostellum (acrotonous Orchids). The pollen-grains
are united in _tetrads_, which, however, often hang loosely together
in pollinia, attached to a sticky part of the rostellum (“adhesive
disc”), so that they adhere to the insects, and are by them transferred
to the stigmas. _Spiranthes. Listera_; _Neottia_. ~_N. nidus-avis_
(Bird’s-nest) is brown (it has little chlorophyll) in colour, has
no foliage-leaves, and lives mainly as a saprophyte; the rhizome
is studded with unbranched, fleshy roots which may form buds at
their extremities.~--_Vanilla_ climbs by aerial roots. The fruit
is fleshy and hardly opens, or does so irregularly.--_Epipactis_,
_Cephalanthera_.--_Epipogon_ and _Limodorum_ are saprophytes without
chlorophyll.

  [Illustration: FIG. 320.--A Flower of _Orchis maculata_ (front
  view): a stamen; _b_ the cup; _n_ the stigmas; _x_ staminodes;
  _sp_ the spur; _spe_ the entrance to it; _sm_-_sl_-_sl_ exterior
  perianth-leaves; _pm_ the labellum, and _pl_-_pl_ the other 2
  interior perianth-leaves. _B-E Orchis mascula_: _B_ lateral
  view of the column; _C_ a pollinium with massulæ (_p_), caudicle
  (_c_) and adhesive disc (_d_); _D_ caudicles with the cup (_r_),
  front view; the latter is depressed so that the adhesive disc is
  seen lying inside it; _E_ a pollinium, more highly magnified;
  some massulæ are removed. _F Ophrys aranifera_: rostellum and
  the base of the anther-loculus; an adhesive disc is seen on the
  right.]

=4.= OPHRYDEÆ. Anthers 2-locular, not falling off, on a very short
column. The anther is united at _its base_ with the rostellum
(_basitonous_ Orchids, Fig. 320 _A_, _B_), while in all other Orchids
it is connected at the apex (acrotonous Orchids). The pollen-grains
in each loculus are united into small “masses” (massulæ), each of
which corresponds to a pollen-mother-cell in the anther, and which
hang together by elastic threads (Fig. 320 _C_, _E_). Each pollinium
is attached at the base by a stalk (caudicle) to an adhesive disc,
formed by the modified stigma (rostellum), and is easily liberated
from it (Fig. 320 _C_, _D_, _F_). The pollinium, which is formed in
an anther-loculus, together with its caudicle and adhesive disc, is
termed “pollinarium” (Fig. 320 _C_).--All Ophrydeæ are terrestrial with
_tuberous roots_, two of which are present in the flowering period, an
older one (from the preceding year) containing the nourishment for
the flowering-shoot of the year, and a young one which is intended to
contain the reserve material for the following year. Inflorescence
terminal.

_Orchis._ The lip has a spur; each of the club-like pollinia is
attached to its own adhesive disc, the discs being enclosed in a common
pouch formed by the rostellum (Fig. 320 _C_, _D_). ~Tubers ovate,
undivided: _O. morio_, _mascula_; tubers palmate: _O. incarnata_,
_maculata_, _majalis_.~--_Ophrys_; no spur, the two adhesive discs
are each enclosed in a separate pouch (Fig. 320 _F_).--_Anacamptis_
and _Serapias_ have one adhesive disc.--_Habenaria_, _Gymnadenia_,
_Platanthera_, _Herminium_, _Nigritella_, _Cœloglossum_, etc., have
naked adhesive discs (no rostellum).

   =5.= EPIDENDREÆ. Acrotonous Orchids with deciduous anthers
   (except _Malaxis_); 2-8 wax-like pollinia, with or without
   caudicles; generally no adhesive discs. _Malaxis_ (the flower is
   twisted through a complete circle, causing the labellum to be
   turned upwards), _Sturmia_ and _Corallorhiza_[32] (Coral-root);
   the latter has a creeping, coral-like rhizome _without roots,
   and is destitute of chlorophyll_ except in the ovary. The
   other two somewhat resemble the tropical Orchids in having the
   lower internodes of the axis of the inflorescence tuberous.
   _Liparis_; _Calypso_. Most of the genera are tropical epiphytes
   and many have aerial, green tubers formed from one or more
   stem-internodes; _Dendrobium_, _Eria_, _Phaius_, _Bletia_,
   _Epidendrum_, _Cattleya_, _Lælia_, _Pleurothallis_, _Restrepia_,
   _Masdevallia_, _Bulbophyllum_, etc.

   =6.= VANDEÆ. These resemble the preceding but have only 2
   wax-like pollinia in each anther, which are attached by a
   caudicle to the adhesive disc of the rostellum. Nearly all are
   tropical epiphytes. _Stanhopea_, _Catasetum_, _Maxillaria_,
   _Oncidium_, _Vanda_, _Polystachya_, etc.

   6,000 (10,000?) species. The majority live in the Tropics and
   occur, especially, as epiphytes on trees or in the crevices of
   rocks, to which they are attached by aerial roots. These _aerial
   roots_, like those of Araceæ, are covered by several layers of
   spirally-thickened cells (tracheides) which contain air and form
   the velamen--an apparatus to absorb moisture from the air. The
   roots have a white appearance when the cells are filled with
   air, which changes to a greenish hue when they are filled with
   water, the chlorophyll then shining through. They generally
   have horizontal rhizomes; the ascending shoots, which bear the
   foliage-leaves, may vary, but they very often swell and assume
   the form of a tuber, which persists for several years fresh and
   green after the leaves have fallen off (Fig. 321). _Vanilla_
   is an exception (see above). Our Orchids are all terrestrial
   (or marsh-plants); the largest number of species is found in
   calcareous soils.

   POLLINATION takes place principally by means of insects,
   but self-pollination occurs in some. The lip serves as a
   landing-stage for the insect visitors, which, on sucking the
   honey, cause the adhesive discs, with the pollinia attached to
   them, to adhere to their bodies (generally to the probosces)
   and so carry them away to other flowers. In some species parts
   of the flower are sensitive or irritable, which has some
   connection with the pollination. Without doubt there are a great
   many biological differences which are closely connected with
   the infinite multiplicity of forms; Darwin (1862) has already
   shown an enormous variety, never even dreamt of before, in the
   European species. The genus _Catasetum_ has ♂-♀-and ☿-plants
   with flowers of such different appearances that they have
   been classed in various genera (_Myanthus_, _Monacanthus_).
   _Platanthera_ is pollinated by hawk-moths; _Ophrys_, by flies;
   _Epipactis latifolia_, by wasps; _Orchis_, by bees, especially
   humble-bees, etc.

  [Illustration: FIG. 321.--_Chysis bractescens._]

   The DISTRIBUTION OF SEEDS is effected by the wind, the seeds
   being so exceedingly small and light. Many species moreover have
   peculiar, elater-like, fine, hygroscopic hairs in the ovary,
   which eject the seeds in a manner similar to the elaters of the
   Liverworts.

   The USES are few, mostly as ornamental plants in conservatories.
   The tubers of several _Orchis_-species are OFFICINAL; they
   contain starch and mucilage and are used us “salep.” The fruits
   of _Vanilla planifolia_ are used as condiments and differ from
   other _Orchid_-fruits in being rather fleshy and in dehiscing
   irregularly; the seeds are very small, shining and black.


                      Class II. =Dicotyledones.=

In this class THE EMBRYO has 2 seed-leaves, a rule from which there are
few exceptions (_e.g. Ficaria_, _Cyclamen_, _Pinguicula_, certain
species of _Corydalis_, with only 1; and a few, mostly parasitic
forms, _e.g. Monotropa_, _Orobanche_, _Pyrola_, entirely without
cotyledons). On germination the cotyledons nearly always raise
themselves above the ground as green, assimilating leaves and are then
termed aerial or epigean, in contradistinction to the underground or
hypogean which are always buried. The structure of the seed varies
(endospermous or exendospermous); the embryo may be straight or curved.
In many instances the primary root grows as a vigorous tap-root,
with weaker branches arising acropetally (in annuals, biennials,
many perennials, especially woody plants); but in a large number of
herbaceous perennials, which have rhizomes, the root behaves very much
as in the Monocotyledons. The roots generally increase in thickness by
means of a cambium.

THE STEM, when seen in transverse section, has its vascular bundles
arranged in a ring; in reality, however, they form a kind of
cylindrical network in the stem; the bundles are open, and thickening
takes place by means of a cambium; annual rings are formed in the
perennial stems. There is a rich and very varied form of _branching_.
The two first leaves of a shoot (fore-leaves) are placed nearly always
to the right and to the left; the same arrangement is found in the two
first leaves developed on the flower-stalk, and these are, as a rule,
the only two; they are found below the calyx and are usually termed the
“_bracteoles_.” It has become customary to indicate the bracteoles by
the letters α and β, according to their sequence of growth, and in that
sense these letters will be employed in the following diagrams.

THE ARRANGEMENT OF THE LEAVES varies very much; there is also a great
variety of shapes in the leaves and their venation, but the linear
leaves, with parallel venation, so frequent in the Monocotyledons,
are seldom met with, as also the large sheaths (though the sheath is
well developed in the Umbelliferous plants); stipules occur much more
frequently.

THE FLOWER is most commonly cyclic, but acyclic or hemicyclic forms
also occur. The type which may be taken as a basis consists in the
majority of instances, as in the Monocotyledons, of 5 whorls, of which
the 4 outer ones (calyx, corolla, and the 2 whorls of stamens) are
most frequently 4 or 5 in number and placed in regular alternation,
whilst the innermost one (the carpels) has generally fewer members,
probably on account of space (Figs. 360, 361, 421, 429, 487, etc.).
Trimerous (Figs. 384, 387, etc.) flowers, or those in which the members
of the flower are in threes or a multiple of three, also occur, as well
as dimerous flowers; other numbers are rare. It is of the greatest
importance in connection with the relative position of the members of
the flower to the axis and bract (orientation), whether the bracteoles
are typically present (even though they may not be developed), or
are typically absent. If there are 2 bracteoles present, then their
position in a pentamerous flower is often as follows: the first sepal
turns obliquely forward, the second is posterior and median, the
third obliquely forward, the fourth and fifth obliquely backward;
quincuncial æstivation is often found in these buds (Figs. 360, 429,
471, 475, 584). The first and third leaves, in the following chapters,
are most frequently alluded to as the “anterior,” the fourth and
fifth as the “lateral” leaves. The _reversed_ arrangement, with the
median sepal in the front, occurs for instance in _Papilionaceæ_ (Fig.
511), _Lobeliaceæ_ (Fig. 594), _Rhodoracecæ_. If any bracteoles are
present below a tetramerous flower, the relation is generally that
2 sepals (the first ones) stand in the median plane, the two next
ones transversely (Fig. 393), and the corolla then adopts a diagonal
position (Fig. 397); but a diagonal position of the calyx generally
shows that the flower is not, strictly speaking, tetramerous, as in
_Plantago_ (Fig. 567), _Veronica_ (Fig. 559 _C_) and others.

If the bracteoles are _not_ typically present, then the position of the
sepals is changed accordingly, and the two outer sepals endeavour to
assume the position which the bracteoles would otherwise have occupied,
_e.g._ in _Primula_ (Fig. 547). Other positions are also found when the
number of bracteoles is more or less than two.

The leaves which follow the sepals occupy definite positions with
regard to them, which we may consider later. An arrangement must,
however, be mentioned here; when the flower is “_diplostemonous_” that
is, has two whorls of stamens (thus, Sn, Pn, An + n), these may be
arranged in two ways. _Either_ the first-formed whorl of stamens, which
are termed the “calyx-stamens,” stands directly in front of the sepals
(that is “episepalous”), and is the _outermost_ whorl, and in this case
a regular alternation takes place between sepals, petals and the two
whorls of stamens, which is also continued into the carpels if their
number is the same as that of the other whorls: the carpels are then
placed opposite the sepals (Fig. 278) and the flower is _isomerous_
and Gn should be added to the formula above. _Or_, the calyx-stamens
form the _innermost_ whorl, and the corolla-stamens, which are
subsequently formed (“epipetalous” stamens), stand _outside_ these
(Figs. 360, 429); if the number of carpels is the same as that of the
preceding whorls, they are often placed _right in front_ of the petals
and the corolla-stamens. The first-mentioned arrangement is termed
_Diplostemonous_, and the second _Obdiplostemonous_. ~Both arrangements
may be found in one and the same order, _e.g._ Caryophyllaceæ. The
size and relation of the members of the flowers, and also the contact
with other members in the early stages of their development, play an
important part in determining the arrangement.~

The great number of structural arrangements found in this enormously
large class, may, as is the case in the Monocotyledons, be further
varied by _suppression and division_ of certain leaves (especially the
stamens). Instances of this will occur in the following (Figs. 559,
568.--426, 441, 445, etc.).

The Dicotyledons were formerly divided into 3 sub-classes: Apetalæ
(those without corolla), Sympetalæ or Gamopetalæ (those with the petals
united), and Choripetalæ or Polypetalæ (the petals not united). This
division has now been abandoned because it has been proved that the
Apetalæ were merely reduced or incomplete forms of the Choripetalæ, and
they have therefore been distributed among the various families of the
latter sub-class.

With regard to the Sympetalæ (or Gamopetalæ) it may be stated that
they form to a very great extent a closely connected and natural
group, having in common not only the character that the corolla is
gamopetalous and the stamens united with it (this being also found in
the Choripetalæ), but also a great many others (such as persistent
calyx, cyclic flowers with the formula S5, P5, A5 and as a rule G2,
the two carpels being united to form the ovary; seeds with a thick
integument and a very small nucellus). They are therefore considered
as an independent sub-class, and must be placed at the close of the
system of classification as the forms which presumably have arisen the
latest. In the future systems of classification this arrangement will
very probably be changed, and the first families of the Sympetalæ, the
Bicornes and others will for instance be to a certain extent united
with the families or orders of the Choripetalæ. The Sympetalæ may
certainly be considered as the youngest types, the strongly pronounced
metamorphosis supporting this theory, as also the formation of the
integument of the ovule, the one thick integument being undoubtedly
derived from the coalescence of two--a holochlamydeous ovule, etc.

The Apetalæ and Choripetalæ are united into one sub-class. The leaves
of the perianth in this case are, as a rule, free from each other, the
structure of the flowers presents many differences, and the ovules have
as a rule 2 integuments and a large nucellus. Considerable uncertainty
still prevails regarding the arrangement and the relationship of the
individual families of the Choripetalæ, and some of the following
families are hardly quite natural; but the best arrangement arrived at
so far has been adopted here.

At the beginning of the book a review of the orders of the Dicotyledons
will be found.


               Sub-Class 1. =Choripetalæ. Petals free.=


                       Family 1. =Salicifloræ.=

Trees and shrubs, which, in the structure of the vegetative shoot and
the catkin-like inflorescences, resemble the Quercifloræ, but the
structure of the flower differs so much from them, that the only order
brought under this heading--_Salicaceæ_--well deserves to be separated
and to form a family of its own, the nearest relatives of which are
still doubtful. ~As Juglandaceæ and Myricaceæ also deserve to be placed
in a special family, the name _Amentaceæ_ (_Catkin-bearers_), hitherto
applied to all of these plants, cannot be retained as the name of a
family.~

  [Illustration: FIG. 322.--Male and female catkins of _Salix
  caprea_.]

There is only one order.

Order. =Salicaceæ= (=Willows=). Trees with simple, scattered,
_stipulate leaves_. _Diœcious_. The flowers are arranged in _simple
inflorescences_ (spikes or racemes) which are termed catkins, and which
fall off as a whole after flowering (♂) or after the ripening of the
fruit (♀) (Fig. 322). The perianth is very imperfect[33] or wanting,
particularly in _Salix_ (Fig. 323 _o_); the ♂-flower with 2–several
stamens and without any trace of a carpel (_a_, _b_, _c_): the
♀-flower has a free bicarpellate ovary, _unilocular_, and formed from 2
lateral carpels with 2 _parietal_ (_median_) _placentæ_ and generally ∞
ovules; the style divides into two stigmas (_d_, _e_, _f_). The fruit
is a two-valved _capsule_ and the very small seeds bear a _tuft of
hairs_ at the base. _Endosperm absent._--~The catkins are situated on
dwarf-branches, which in some species often develop before the leaves
and bear at their base only scale-leaves; in others foliage-leaves
are borne beneath the catkins. The vegetative bud commences with 2
bud-scales which are united on the anterior side into a scale. The
capsule opens by the dorsal suture. The seed-hairs spring from the
funicle.~

  [Illustration: FIG. 323.--_Salix_: male flowers of _S. pentandra_
  (_a_), _S. aurita_ (_b_), _S. rubra_ (_c_), female flowers of _S.
  aurita_ (_d_), _S. nigricans_ (_e_), _S. mollissima_ (_f_).]

_Salix_ (Willow) has short-stalked, most frequently lanceolate leaves
and erect catkins with undivided bracts (Fig. 322). The flowers are
naked; 1 (_o_ in _a-f_) or 2 yellowish glands situated in the median
line. In the ♂-flower generally two stamens, situated laterally like
the carpels in the ♀-flower. ~Various forms are seen in Fig. 323.--The
terminal bud of the branches often aborts regularly, the uppermost
lateral bud taking its place.~

_Populus_ (Aspen, Poplar) has long-stalked, more or less round or
cordate leaves with drawn-out apex; catkin pendulous; lobed bracts;
perianth cup-like with oblique edge; stamens usually numerous; stigmas
often divided.--~_P. tremula_ (Aspen) has received its name from the
tremor of the leaves: _cf._ “to shake like an aspen leaf.”~

   POLLINATION. The Poplars are wind-pollinated. The Willows have
   sticky pollen and are pollinated by insects. The catkins of
   the Willows, especially the ♂, are more conspicuous, from the
   numerous, closely-packed, yellow flowers, rich in honey and
   pollen. The catkins often appear before the foliage and so
   are much more easily seen, whilst at this time of the year the
   number of competing honey-flowers is smaller, and the insect
   visits consequently more numerous. On many catkins of the Willow
   the flowers open earliest on the side which is turned towards
   the sun and in descending order, _i.e._ the upper flowers
   develop before the lower ones. Hybrids frequently appear.

   There are about 180 species existing in the northern, cold and
   temperate latitudes. Some in the Polar regions are scarcely more
   than an inch in height, and have a creeping rhizome (_Salix
   herbacea_, _polaris_, _reticulata_). Fossil forms are found in
   the Tertiary and perhaps also in the Upper Cretaceous.

   USES. Principally for ornamental trees, as they grow very
   quickly and are easily propagated by cuttings, _S. babylonica_,
   Weeping Willow; _S. purpurea_; _Populus alba_, Silver Poplar;
   _P. pyramidalis_, Pyramid Poplar--a form of _P. nigra_; _P.
   monilifera_, Canadian Poplar. The wood is very poor and
   little used; the branches of many Willows are cultivated for
   basket-making, etc. The wood of the Aspen is used for matches.
   The bark contains tannin and, in many Willows, a very bitter
   extract, _Salicin_ (_S. pentandra_, _fragilis_). Salicylic
   acid (officinal) is obtained from _Salix_. Balsam is extracted
   from the buds of many Poplars, especially when the leaves are
   shooting.


                      Family 2. =Casuarinifloræ.=

Trees with verticillate, scale-like leaves forming sheaths at the
nodes. Monœcious. Flowers unisexual. ♂-flowers in catkins; ♀ in short
spikes. _Pollen-tube entering the ovule at the chalaza_, and not
through the micropyle. Ovary 1-seeded, unilocular. Carpels uniting into
a multiple fruit. Only one order.

Order. =Casuarinaceæ.= Trees (30 species), from Australia and certain
parts of S.E. Asia, with peculiar, equisetum-like appearance. The
leaves are verticillate, scale-like and united into sheaths. The
internodes are furrowed. Branching verticillate. The unisexual flowers
are situated in catkins or short spikes. The ♂-flower has a central
stamen, surrounded by 2 median, scale-like perianth-leaves and 2
lateral bracteoles. The ♀-flower has a 1-chambered ovary (2 ascending,
orthotropous ovules), no perianth, but 2 large, lateral bracteoles
which finally become woody and form two valves, between which the
nut-like fruit is situated. The multiple-fruits therefore resemble
small cones.--_Casuarina equisetifolia_, cultivated, gives “iron-wood.”

   [The Casuarinas differ from the ordinary Dicotyledons in many
   important respects which may be briefly summarised thus:--The
   bicarpellate ♀-flower has a well-pronounced stylar-cylinder
   terminated by two stigmas, but the cavity of the ovary closes
   very soon after its formation, and in it are developed two
   parietal ovules; these are united by a bridge of cellulose to
   the stylar-cylinder or summit of the ovary, and hence the ovules
   are connected with the walls of the ovary by the bridge (above),
   as well as by the funicle (below). The archespore is developed
   from the hypodermal cells at the summit of the nucellus,
   two primordial mother-cells are first formed and from these
   by tangential divisions a central cylindrical mass of cells
   (sporogenous-tissue) is produced which is surrounded by tapetal
   cells. The cells of the sporogenous tissue correspond to the
   mother-cells of the embryo-sac of other Angiosperms; they divide
   transversely and from 16–20 macrospores are formed together with
   inactive cells which are not crushed together as in the case
   of other Phanerogams. The sexual apparatus is developed from a
   single cell, but the number of cells composing this apparatus
   is subject to variation, the oosphere being accompanied by one
   or two neighbouring cells which resemble canal-cells rather
   than synergidæ. The sexual apparatus is found in the majority
   of the macrospores, but in most of these it remains as a number
   of naked cells; while in the fertile macrospores the cells
   are invested by walls of cellulose (usually only one fertile
   macrospore is found in each ovule). Antipodal cells are never
   developed. The macrospores elongate considerably towards the
   chalaza, into which some penetrate. The pollen-tube traverses
   the stylar-cylinder and enters the ovules at the chalaza, its
   passage through the tissue of the nucellus being assisted by
   the prolongation of the macrospores. About the centre of the
   nucellus the pollen-tube is ruptured; the apical portion which
   alone takes part in the fertilisation being firmly attached to
   the macrospore. Although the actual impregnation has not been
   observed, Treub considers that the endosperm begins to be formed
   before fertilisation.]


                       Family 3. =Quercifloræ.=

_Trees_ and _shrubs_ with small, unisexual, _monœcious_ flowers, having
no perianth or a simple inconspicuous one. The ♂ and ♀ flowers are
very different and generally placed in separate inflorescences. The
♂-flowers are most often adnate to the bracts. The stamens are placed
_opposite the perianth-leaves_, when they are present in equal numbers.
The ♀-flower is _naked_, or has a _superior_ perianth. The ovary at
the base is 2- or 3-(-6) locular with 1 or 2 pendulous ovules in each
loculus, only one of which is developed; the fruit is a one-seeded
_nut_; _endosperm absent_; embryo straight. The inflorescences, which
are either compound and mixed (small dichasia in spikes) or simple,
are here also termed _catkins_; but, strictly speaking, this term is
applied to the ♂-inflorescences only. In all Quercifloræ the leaves are
_scattered_ (usually in 2 rows) _simple_, and _penninerved_, and with
_deciduous stipules_.

   It is worthy of remark that in _Betulaceæ_, _Corylaceæ_ and
   _Quercus_ the ovules, and to some extent the loculi of the
   ovary are not developed till after pollination, so that the
   development of the pollen-tube proceeds very slowly. The
   smallness of the flowers, the absence of honey, the dryness
   and lightness of the pollen, the size of the stigma and the
   abundance of hairs found on many stigmas are all adaptations for
   wind-pollination. It is also an advantage that the flowers are
   generally pollinated before the foliage-leaves are developed,
   thus preventing the pollen being entangled by the leaves.

   The two orders _Betulaceæ_ and _Corylaceæ_ mentioned here are
   by other authors united into one order. [It is doubtful whether
   these two should be retained in the family Quercifloræ, as
   recent researches (p. 273) have shown that they differ from
   the Cupuliferæ in many important points, and agree with the
   Casuarinas in the fact that the pollen-tube enters the ovule
   through the chalaza.]

Order 1. =Betulaceæ= (=Birches=). Monœcious, with thick, cylindrical,
_compound_ ♂ and ♀ inflorescences (2- or 3-flowered dichasia in a spike
with spirally-placed floral-leaves) (Figs. 324, 326, 328). When the
perianth in the ♂-flower is completely developed, it is composed of 4
somewhat united leaves, which are placed opposite the 4 stamens (Figs.
325, 326 _A_). The female flowers are _naked_; the ovary is bilocular,
with two styles and one _pendulous_ ovule in each loculus. The
subtending floral-leaves unite with the bracteoles and form a 3–5-lobed
cover-scale, which is not attached to the fruit (Figs. 325 _D_, 326
_B_). Fruit a _nut without cupule_ (see _Corylaceæ_ and _Cupuliferæ_).
~In the bud the leaves are flat. The stipules are deciduous. On
germination the cotyledons are raised above the ground. Terminal buds
are only found on old Alder trees; the Birch has sympodial branches.~

  [Illustration: FIG. 324.--_Alnus glutinosus._ Branch of Alder
  with ♂-(_n_) and ♀-(_m_) catkins: _k_ bud; _b_ fruit-bearing
  catkin (“cone.”)]

_Alnus_ (Alder) (Figs. 324–326). In the majority of species the ♂-and
♀-catkins are both developed in the year previous to their flowering,
and pass the winter naked and bloom before the leaves expand. ♂-flower:
4 stamens. ♀-flower: the 5-lobed cover-scales of the ♀-catkin are woody
and remain attached to the axis, so that the entire catkin when ripe
resembles a small cone (Fig. 324 _b_). Each cover-scale supports two
winged or wingless nuts. ~In the native species of Alder the buds are
stalked (Fig. 324 _k_). The bud-scales are formed by the stipules of
the lowest leaves.~

_Betula_ (Birch). The ♂-catkins, in the native species, appear
in autumn, the ♀-catkins in the flowering year on leaf-bearing,
short-lived shoots. ♂-flowers: 2 stamens, divided (Fig. 328 _A_). The
3-lobed cover-scales (Fig. 327 _a_) of the ♀-catkin are detached from
the axis; each cover-scale supports 3 broadly winged nuts (_b_).
~The stem has cork with annual rings. The young twigs and leaves have
aromatic resin glands.~

  [Illustration: FIG. 325.--_Alnus glutinosa_: _A_ dichasium
  of ♂-flowers seen from the front; _B_ the same from inside;
  _C_ the same from the back; _D_ dichasium of ♀-flowers with
  subtending-leaf and four bracteoles. The letters _b_, α, β, β′, β
  are the same as in Fig. 326 _A_.]

  [Illustration: FIG. 326.--_Alnus glutinosa_: diagram of dichasia
  of ♂ (_A_) and ♀ (_C_) catkins; _B_ a cone-scale. All the
  bracteoles in _A_ and _C_ are slightly pressed from their normal
  position.]

   THE INFLORESCENCES OF THE ALDER.--In the axil of each
   cover-scale [_b_ in the Figs] is situated, in the ♂-catkins
   (Figs. 326 _A_, 325 _A-C_) a 3-flowered dichasium, the
   flowers of which have a 4-partite perianth, the posterior
   perianth-segments being sometimes almost suppressed, and 4
   stamens with undivided filaments. In the ♀-catkin (Figs. 325
   _D_, 326 _C_) a 2-flowered dichasium is found, the middle
   flower being suppressed (indicated by a star in _C_). In both
   instances the inflorescences have two bracteoles (α-β) and the
   flowers borne in their axils have each one bracteole (β′), the
   other one (α′) being suppressed and therefore in 326 _A_ and _C_
   only represented by a dotted line; these four bracteoles unite
   with the cover-scale (_b_) which supports the entire dichasium,
   to form the 5-lobed “cone-scale” (Fig. 326 _B_) which in the
   ♀-catkin eventually becomes woody.

   THE INFLORESCENCES OF THE BIRCH.--A 3-flowered dichasium is
   situated in the axil of the cover-scale in both ♂-and ♀-catkins
   (Fig. 328 _A_, _B_); only the central flower has bracteoles
   (α-β) (the lateral flowers having no bracteoles), and these
   bracteoles unite, as in the Alder, with the supporting
   cover-scale (_b_), and form a three-lobed cone-scale (Fig. 327
   _a_).

   While the ♀-flower exactly resembles that of the Alder, the
   reduction of the ♂-flower, already described in the Alder, is
   carried further, so that often only the 2 median perianth-leaves
   are developed (Fig. 328 _A_); there are also _only_ 2 stamens,
   these being deeply cleft, while the other 2 are suppressed.

   About 50 species; N. Temp.--Fossil-forms certainly occur in
   the Oligocene. During the Glacial period the Dwarf-birch (_B.
   nana_) extended over Europe; at the present time it is confined
   to the moors and mountains of N. Europe and N. America and Asia.
   Wind-pollinated.

   USES.--Important forest trees. The bark contains tannic acid.
   The tar of the Birch is used in the preparation of Russia
   leather; whilst its spring sap is very saccharine, and is used
   in some places for making a fermented drink. Its external bark
   is used for roofing, for baskets, etc.

  [Illustration: FIG. 327.--_Betula verrucosa_: _a_ cone-scale; _b_
  fruit.]

  [Illustration: FIG. 328.--Diagrams of dichasia in the ♂-(_A_) and
  ♀-(_B_) catkins of Birch.]

Order 2. =Corylaceæ= (=Hazel-nuts=). Monœcious. The ♂-catkins are long
and cylindrical; the ♂-flowers are placed singly in the axil of the
subtending-leaf (cover-scale); they are _naked_ and formed of a number
of _divided_ stamens, which are partly united with the cover-scale,
4 in the Hazel, apparently 8 (Figs. 330 _A_, 329 _B_, _C_), more on
the Hornbeam. The ♀-flowers have a very small, _superior_ perianth;
in the axil of each cover-scale a 2-flowered dichasium (Fig. 329
_D_) is present, of which the central flower (* in Fig. 330 _B_)
is suppressed. The gynœceum is bicarpellary as in the Birches; the
ovary is bilocular, with two long styles (Fig. 329 _D-F_); the loculi
have 1 (-2) ovules (Fig. 330 _B_). Each single ♀-flower and fruit is
surrounded by a _leaf-like covering_, the _cupule_ (husk), which is
_formed of three floral-leaves_ (namely, the bract of a lateral flower,
and its own bracteoles; thus in Fig. 330 _B_, α, α′, β’ form the cupule
for the left-hand flower, and β, α_[1}, β_[1}, the cupule for the
right-hand).

_Corylus_ (Hazel-nut, Fig. 329). The long, cylindrical ♂-catkins pass
the winter naked, 2–3 together, on short branches. The very small
♀-catkins are enclosed in buds, in which they pass the winter; these
buds are situated in the axils of the fallen foliage-leaves, and it
is only by their larger size that they may be distinguished from the
ordinary foliage-buds. In spring the ♀-catkins are easily recognised
by their red, projecting stigmas (Fig. 329 _A_). The cupule--the
“husk”--is tubular, fringed, and envelopes the nut. ~The leaves are
alternate and unsymmetrical, the external side being larger than
the internal; this is connected with the vernation, the blade being
conduplicate in the bud; the stipules are deciduous. The bud-scales
are formed of stipules, the most internal having a leaf-blade attached
to them which is suppressed in the external ones. The cotyledons remain
underground on germination.~

  [Illustration: FIG. 329.--_Corylus avellana_: _A_ branch at
  the time of flowering with ♂-and ♀-catkins; _B_ ♂-flower with
  subtending-leaf (bract) and two bracteoles; _C_ the same without
  the anthers; _D_ view of interior of ♀-dichasium shortly after
  fertilisation; _E_ young fruit with cupule; _F_ similar one with
  the cupule opened; _G_ mature ♀-fruits; _H_ nut.]

_Carpinus_ (_C. betulus_, Hornbeam). The ♂-and ♀-catkins do not appear
till the leaves are shooting. The ♀-catkin in this instance is also
long and cylindrical. The cupule in _C. betulus_ is 3-lobed, and
to a slight extent only embraces the base of the ribbed nut (Fig.
331); each lobe corresponds to a floral-leaf. ~Whilst the carpels
are placed medianly in _Corylus_, in _Carpinus_, on the other hand,
they are situated transversely, as in the case of the _Betulaceæ_.
The lamina of the leaf is not conduplicate in the bud, but flat,
and folded only along the lateral veins, which are also indicated
in the form of the fully-developed leaf; otherwise the vegetative
characters are essentially the same as in the Hazel. The cotyledons
are aerial.--_Ostrya_ resembles the Hornbeam, but the cupule completely
envelopes the nut, as a sac open at the apex (Eur., N. Am., Japan).~

   N. Am., Asia, and Europe; 25 species.--Fossil forms in the
   Oligocene. Wind-pollinated. USES. As timber (_Carpinus betulus_)
   and firewood. The fruits of _C. avellana_ (ordinary Hazel-nut),
   _C. tubulosa_ (Lambert’s nut) and _C. colurna_ (Turkish Filbert)
   are edible.

  [Illustration: FIG. 330.--Diagrams of the ♂-flower (_A_) of
  _Corylus_ and the dichasium of the ♀-flowers (_B_).]

  [Illustration: FIG. 331.--Nut of the Hornbeam with cupule.]

Order 3. =Cupuliferæ.= Monœcious. The inflorescences make their
appearance with the leaves, arising in the axils of the leaves of
the same year. _A woody cupule_ furnished externally with scales or
spines is _common_, and surrounds 1-several flowers (the cupule in
the Corylaceæ never encloses more than a _single_ flower or fruit).
The ♂-flower has a united perianth, which is, however, 4–6 partite,
and encloses an indefinite number of undivided stamens. The ♀-flower
has a _superior, 6-merous_ perianth (3 + 3, compare Figs. 332 _D_,
334); the gynœceum is formed of 3 (or in _Castanea_ 4–6) carpels with
a corresponding number of stigmas (Figs. 332 _D_, _H_; 334, 335); and
the ovary has at the base 3 (-6) loculi (Fig. 333), each of which has 2
pendulous anatropous ovules; the fruit is a one-seeded nut (Figs. 332
_H_, 336).

The cupule of the Cupuliferæ, according to the opinion of Eichler, is
formed by united bracteoles, (compare Fig. 333, where the four valves
in the cupule of Castanea are considered as bracteoles of the lateral
flowers of the dichasium); according to another view (see Prantl, in
Engler’s _Bot. Jahrb._, viii., 1889), it is a ring-like axial outgrowth
independent of the bracteoles of the flower, whose scales and spines
are floral-leaves. The cupule in the Oak only encloses the base of the
fruit, but in the Eating-chestnut and Beech the fruit is completely
enclosed, and consequently the cupule must divide into a number of
valves (generally 4) to allow the fruit to escape. In the 3-flowered
dichasia of _Pasania_, Sect. Eupasania (Trop. Ind.), each individual
flower has its own cupule of the same structure and development as in
_Quercus_; and, moreover, each group of flowers has externally the
typical six bracteoles.

  [Illustration: FIG. 332.--_Castanea vesca_: _A_ branch with
  inflorescences; _B_ ♂-flower; _C_ young cupule with three
  ♀-flowers; _D_ ♀-flower; _E_ the same in longitudinal section;
  _F_ cupule with 3 nuts (diminished); _G_, _H_ nuts (_G_ in
  longitudinal section to show embryo).]

_Castanea_ (Eating-chestnut, Fig. 332). The catkins are erect (_A_),
cylindrical, with the ♀ at the base and the ♂ at the top, or some
are entirely ♂ and _composed of small dichasia_. The _cupule_ (_C_,
_F_) is 4-_valved_, provided with spines, and entirely envelops the 3
_nuts_; it is already developed at the time of flowering.--~♂-flowers
are most frequently borne in 7-flowered dichasia, and have a well
developed perianth, most frequently consisting of 6 leaves in two
whorls (Fig. 332 _B_), and a large number of stamens. ♀-flowers are
most frequently borne in 3-flowered dichasia (Figs. 332 _C_, 333); the
letters in Fig. 333 indicate the older theory, according to which the
4 bracteoles (α′-β′) of the two lateral flowers are thick and united
into a single 4-valved, _woody cupule_, which surrounds the 3 nuts,
and is furnished externally with spines; the spines are well developed
hair-structures.--6 carpels in two whorls.--The leaves in the vertical
shoots have a divergence of 2/5, 3/8, 5/13; on the horizontal shoots
they are alternate. The cotyledons remain underground on germination.~

  [Illustration: FIG. 333.--Diagram of the cupule of _Castanea_.]

  [Illustration: FIG. 334.--Female flower of _Fagus_ (mag.)]

_Fagus_ (Beech). The ♂-catkins are pendulous, capitate; the ♂-flowers
have an obliquely bell-shaped, fringed perianth, with 6–20 stamens.
♀-catkins erect, 2-flowered, borne singly in the axil of foliage-leaves
of the same year; the ♀-flower has a gynœceum formed of 3 carpels,
bearing an epigynous, 6-leaved perianth (Fig. 334). In this genus
_the dichasium has only 2 flowers_, the central one being suppressed.
_The cupule contains_, therefore, only 2 triangular nuts (“mast”).
~All the shoots have the leaves arranged in two rows; the rows are
on the underside, being only about 90° distant from each other; the
buds on the other hand approach each other towards the upper side. The
bud-scales are stipules without laminæ; in vernation the laminæ are
folded along the lateral ribs, the upper lateral portion being the
largest (as in Hornbeam and Chestnut). The cotyledons are folded, and
at germination are aerial, large, and reniform. 4 species (Europe,
Japan, N. Am.)--_Nothofagus_ (S. Am., New Zealand, S. Austr.)~

_Quercus_ (Oak, Fig. 335). Catkins simple. ♂-catkins long,
thin, _pendulous_, few-flowered. ♀-catkins erect; the cupule is
_cup-like_, _entire_, and encloses only the base of the solitary nut
(“acorn”).--~The ♂-flower has a similar construction to that of the
Chestnut. The ♀-catkin has not more than 5 flowers (single-flowered
dichasia, in which _only the central flower is developed_). The
scales on the cupules are no doubt leaf-structures in this case also.
According to another theory, the scales are hair-structures; they arise
on the internal face of the young cupule apparently in descending, but
really in ascending order. The rim of the cupule gradually expands.
In the ♀-flower (Fig. 335) the loculi of the gynœceum, together with
the ovules, are not developed until _after_ pollination.--The leaves
in all cases have a divergence of 2/5; the lowermost leaves on the
shoots are reduced to stipules which serve as the bud-scales (5 rows).
The laminæ are conduplicate, as in _Corylus_, and the external side is
the broadest. The cotyledons are fleshy and remain underground. 200
species.--_Pasania_ (100 species).~

  [Illustration: FIG. 335.--_Quercus_: _A_ ♀-flower in its cupule
  (mag.); _B_ longitudinal section through _A_, showing cupule,
  perianth, and inferior ovary.]

  [Illustration: FIG. 336.--Fruit of _Quercus_.]

   368 species, in temperate climates, especially in Europe and
   N. America. Authenticated forests have been found in the
   Oligocene. The Beech has one species, _Fagus sylvatica_, in
   Europe; it is a most important forest tree (in Denmark the most
   important) and reaches its most northern limit near Alvesund
   in Norway (60° N.L.), its northern boundary line passing
   from Alvesund in a zig-zag line through Ludwigsort, south
   of Königsberg, in Prussia, towards the Crimea. According to
   Steenstrup and Vaupell, the Beech did not make its appearance
   in Denmark until a comparatively recent time, the Oak then
   being partially supplanted. Other species of Beech are found
   in N. America and Japan. Several species of _Nothofagus_
   occur in the South West of S. America, and in the colder
   regions of the southern hemisphere. The Oaks grow especially
   in temperate regions, _e.g._ in Western Asia, N. America,
   and the mountains of Mexico. Evergreen species are found in
   Tropical Asia, Himalaya, Japan and the Mediterranean region.
   In this country there is one species of Oak (_Q. robur_), of
   which there are three varieties (_Q. pedunculata, intermedia,
   sessiliflora_). The Eating-chestnut is found in the South of
   Europe, but is cultivated in the midland and southern counties
   of England.--USES. The wood of these trees is very useful as
   timber. The wood of _Q. tinctoria_ has a yellow colouring
   matter (Quercitron-wood). The bark of the Oak contains a large
   quantity of tannic acid, and is used for tanning; for this
   purpose also the cupules of _Q. vallonea_, _ægilops_, _græca_,
   and others from the Eastern Mediterranean, are used under the
   name of “Valloons.” The Cork-oak (_Q. suber_; S.W. Europe) is
   the most important tree from which cork is obtained, its bark
   being very largely developed and stripped for cork. Gall-nuts
   are found on many species; those of _Q. lusitanica_, var.
   _infectoria_ (Eastern Mediterranean) are officinal, and likewise
   the fruits (acorns) and the bark of _Quercus pedunculata_ and
   _sessiliflora_. Oil is obtained from the Beech “mast.” The nuts
   of the Chestnut tree are edible.


                      Family 4. =Juglandifloræ.=

This family resembles the Quercifloræ in the catkin-like
inflorescences, the imperfect, _unisexual_ flowers, the epigynous
perianth and the woody shoots with scattered leaves, etc., though it
is in other respects very dissimilar; one point of difference is the
presence of _aromatic_ compounds, but a more important divergence is
found in the structure of the gynœceum, which is formed of two carpels
with _one loculus_ and has one _basal_, _orthotropous and erect_
ovule, which, as in the Quercifloræ, does not become developed until
after pollination; the fruit too is very different, being generally a
_drupe_. _Endosperm absent._

  [Illustration: FIG. 337.--_Juglans regia_: _A_ ♂-flower seen
  from below with bract (cover-scale) (_b_), bracteoles (α and β),
  perianth-leaves (_p_); _B_ the same from the front; _C_ lateral
  view of the same; _D_ diagram of _A_; _E_ ♀-flower with bract,
  the bracteoles are united with the ovary, their edge being
  visible as an indented line below the perianth; _F_ 2 ♀-flowers
  at the end of a foliage-shoot; _G_ fruit (without the fleshy
  covering) in longitudinal section; _H_ transverse section of the
  same.]

Order 1. =Juglandaceæ (Walnuts).= Leaves _scattered_, _imparipinnate_,
rich in _aromatic_ compounds. _Stipules absent._ Flowers unisexual.
_Monœcious._ The ♂-catkins are lateral, generally on naked branches
of the previous year, cylindrical, pendulous, many-flowered; the two
bracteoles and the 2–4-leaved perianth of the ♂-flower unite with
the subtending bract; the ♂-flower has indefinite stamens (6–20 in
_Juglans_, Fig. 337 _A-D_). The ♀-catkins are terminal, generally on
branches of the same year, few-flowered (Fig. 337 _F_); the ♀-flowers
have a _superior_, 4-leaved perianth, a bicarpellate gynœceum, two
styles with stigmas on the internal surface. The ovary, bracteoles
and bract all unite together (Fig. 337 _E_). The fruit is generally a
green or black _drupe_,[34] whose flesh (outer soft portion) in _Carya_
and _Juglans_ ruptures more or less irregularly, and frees the stone
(“Walnut”).--~The stone in _Juglans_ is divided internally by one true
(Fig. 337 _H_) and by several false, low partition walls into several
_incomplete_ compartments, so that the two large _cotyledons_ become
lobed and incised to fit like a cast into the irregularities of the
inner surface of the stone; the embryo is exendospermous and covered
with a thin testa.--THE LEAF SCARS are large and cordate with 3 groups
of vascular bundles. The PITH in _Juglans_ and _Pterocarya_ is divided
into chambers. The stone ruptures, on germination, along the dorsal
suture into 2 valves; the cotyledons remain underground. In _Juglans
regia_ a long row of accessory buds is found on the lowest internode
(epicotyl) above the axils of the cotyledons. _Pollination by the
wind._ Both protogynous and protandrous examples of _Juglans regia_
occur.--33 species, mostly in temperate North America.--USES. Walnuts
are obtained from _J. nigra_ and _regia_; Hickory from North American
species of _Carya_. The oil-containing seeds of several species are
edible. _Pterocarya_ and others are cultivated as ornamental plants.~

  [Illustration: FIG. 338.--_Myrica gale_: _a_ young fruit; × the
  bracteoles with numerous glands; _b_ longitudinal section of
  fruit.]

Order 2. =Myricaceæ=. To this order belong shrubs or trees which
have penninerved, simple, at most lobed or pinnatifid leaves, with
or without stipules, and with yellow, aromatic, resin glands (Fig.
338 _a_). The flowers, situated in catkin-like spikes, are unisexual
and _naked_, and supported by scale-like floral-leaves. ♂-flower: 4–6
(–16) stamens with short filaments; ♀: generally situated singly. The
gynœceum has a short style with 2 long stigmas, and unites with the
bracteoles, which form wing-like outgrowths on the ripe drupe as in
_Pterocarya_ in the Juglandaceæ (Fig. 338). Cotyledons fleshy (Fig. 338
_b_).--_Myrica_; _Comptonia_.

   40 species; Temperate.--_Myrica gale_ (Sweet-gale, Bog-myrtle)
   has been used in the preparation of beer (Sweet-willow beer)
   on account of its resinous essential oil. _M. cerifera_ (N.
   America) and species from the Cape, _M. quercifolia_ and others,
   form wax on the fruit which is used in the preparation of
   candles.


                       Family 5. =Urticifloræ.=

The flowers are regular, _hypogynous_, nearly always unisexual, _small_
and insignificant, with _single_, green perianth of 4–5 leaves. Stamens
4–5, _placed opposite_ the leaves of the perianth. Ovary formed of 1
or 2 carpels, most frequently _unilocular_, with one ovule (Fig. 340).
The fruit is a _nut_, more rarely a drupe, with one seed, _generally
endospermous_. ~The Nettles are the sole order in the family which has
only one carpel (1 stigma); this turns the posterior side to the front
(Fig. 340). The others have two carpels (2 stigmas) but the anterior
only is fertile (Fig. 346) except in a few Ulmaceæ and Moraceæ.~

The majority are trees or shrubs with petiolated leaves, _stipulate_;
_rough hairs_ are very frequently developed upon the leaves. The
flowers are very often crowded together in the inflorescence, which is
rarely catkin-like. Peculiar aggregations of fruits are found in some
orders. _Latex_ and tough _bast_, which is used technically, are also
frequently found. Cystoliths are found in the epidermis of many species
of _Ficus_, _Urtica_, and others. ~_Wind-_ or _self-pollination_
is most common, as in the Quercifloræ and Juglandifloræ.~ In ~the
Urticaceæ, _Morus_ and some others, the stamens lie incurved in the
bud, and when ripe straighten themselves suddenly and elastically,
and thus small clouds of pollen-grains are ejected with considerable
violence on to the stigmas, which are often provided with brush-like
hairs (Fig. 341). The formation of honey does not take place.~

Order 1. =Ulmaceæ= (=Elms=).--Trees or shrubs without latex. Leaves
simple, arranged in two rows (divergence 1/2), oblique (the inner side,
nearer the axis, being the larger), strongly penninerved, dentate,
hispid; stipules deciduous. In opposition to the other Nettle-like
plants the flowers are often ☿ with a united cup- or saucer-like,
generally 4–(5)–6-divided perianth, and a corresponding or larger
number of opposite _erect_ stamens. The gynœceum has two carpels
(2 stigmas), generally one loculus with one pendulous, anatropous
or amphitropous ovule,[35] seldom two loculi and 2 ovules. Fruit
one-seeded (nut or drupe). Embryo without endosperm.

=A.= ULMEÆ. The fruit is a _winged nut_ (Fig. 339), the embryo
straight, without endosperm. Anthers extrorse.--_Ulmus_ (Elm). The
flowers are situated in inflorescences which develop from the lower
buds of the shoot of the preceding year. ~The lowermost bud-scales
are empty, the uppermost support either solitary flowers, or small,
dichasial or unipared scorpioid inflorescences. The terminal bud on the
vegetative shoot quickly falls off, and the upper lateral bud continues
the growth sympodially. Flowering takes place before the leaf-buds
open. The flowers are wind-pollinated and have no honey. Fossil species
have been found in the Oligocene.~

   20 species; North Temp. (2 species in this country). Important
   as timber. The Cork-elm (_U. suberosa_) has a rather thick cork,
   which, however, is of no technical use. The bast is used as
   Lime-bast.

   =B.= CELTIDEÆ. The fruit is a drupe, the embryo curved, with
   folded or rolled up cotyledons, with or without endosperm.
   The anthers are introrse. The flowers are borne on a shoot of
   the same year. _Planera_ (N. America); _Zelkova_.--About 114
   species; especially N. Temp., Trop.

  [Illustration: FIG. 339.--_A Ulmus campestris_, flower with
  exceptionally aborted gynœceum; _B_, _U. effusa_, flower with
  8 stamens; _C_, _U. campestris_, fruit opened in front to show
  the seed pendulous from the apex of the loculus; one loculus is
  aborted.]

Order 2. =Urticaceæ= (=Nettles=).--The majority of species are herbs
with simple, stipulate leaves; they have _no latex_; _stinging
hairs_ abundant. The flowers (Fig. 340) are _unisexual_, generally
2-merous and arranged _in clusters_, which are united into catkin-like
inflorescences. The perianth is composed very often of 4 (2 + 2)
free, or in the ♀-flowers generally united, green leaves; the 4 (2
+ 2) stamens are opposite the perianth-leaves, the filaments are
_bent inwards_ in the bud and throw themselves elastically towards
the outside. The gynœceum has _one style_ and _one stigma_ (capitate
or brush-like, Fig. 341); the ovary is unilocular, with _one
orthotropous_, _erect_ ovule (all other orders of this family have
inverted or curved ovules). Fruit, a nut or drupe. _Endosperm present_
(in _Urtica_ very little), oily. Embryo straight. ~The STINGING HAIRS
are club-shaped, very turgid, and provided with a siliceous, brittle
apex, which breaks off in an oblique direction and allows the poisonous
cell-sap to be forced out. In many tropical Nettles this is so strong
that it may produce partial paralysis. There is no rudiment of an ovary
in the ♂-flowers (Fig. 340 A). The PERIANTH in the ♀-flower differs
from that of the ♂ in having the two internal leaves generally much
larger and enveloping the fruit (Fig. 340 _B_); it often happens that
all the perianth-leaves are united to form a gamophyllous envelope.
☿-flowers may occur among the others.--THE INFLORESCENCES among our
native species are dichasia, which become transformed into unilateral
scorpioid cymes by the development of the bud of the 2nd bracteole. In
_Parietaria_ they are more pressed together, and the floral-leaves at
the same time are also raised on their axillary shoots to just beneath
the flower. As a rule, not only in this order but also in those related
to it, a small vegetative branch is situated in the axil of the
foliage-leaf, and this bears an inflorescence on each side at its base.~

_Urtica_ (Nettle) has opposite leaves with distinct stipules and
stinging hairs. The perianth-leaves of the ♀-flower are free (Fig.
340).--_Parietaria_ (Pellitory) has scattered leaves without large
stipules, and stinging hairs are absent. The ♀-perianth is 4-toothed,
flask- or bell-shaped.--~_Pilea_ is a tropical genus with trimerous,
zygomorphic ♀-flowers, the posterior perianth-leaf being much larger
than the two others, and more or less hood shaped.--The flower of
_Forskohlea_ is the most reduced; the ♂-flower has only one stamen, and
the ♀-as well as the ♂-flowers have a one-sided, tongue like perianth
(?). _Pouzolzia._~

  [Illustration: FIG. 340.--Diagram of ♂-and ♀-flowers of _Urtica
  dioica_.]

  [Illustration: FIG. 341.--_Parietaria diffusa_; hermaphrodite
  flower: _a_ in the female, _b_ at the commencement of the male
  stage; the stigma has fallen off, but the anthers have not yet
  dehisced.]

   WIND-POLLINATED. The pollen is shot out of the anthers, when
   they spring forward, and is caught by long stigmatic hairs.
   _Parietaria diffusa_ is protogynous (Fig. 341).

   500 species; chiefly in the Tropics, although the few species
   which occur in Europe are represented by a much larger number
   of individuals.--USES. The bast of the native species _Urtica
   dioica_ and _urens_, of _U. cannabina_ (Siberia), etc.; of
   _Boehmeria nivea_ “Ramié” and “China-grass” (from Sunda Is.,
   China), and others, is used in the manufacture of muslin.

Order 3. =Moraceæ= (=Mulberries=). Nearly all trees or shrubs, seldom
herbs, generally with latex. The leaves are scattered, and not
infrequently lobed. The flowers are _unisexual_ (monœcious or diœcious)
and arranged in catkin- or capitulum-like, compound inflorescences.
Perianth-leaves 2–6, generally 4, with an equal number of stamens
opposite to them, as in the Nettles. The ovary is 1–seldom 2-locular,
and has 2 stigmas (it is thus formed from 2 carpels) seldom only one
style with one stigma. One ovule in each loculus, more or less curved,
and _pendulous_; micropyle directed upwards. Fruit usually a drupe.
The embryo is generally curved inside the _fleshy endosperm_, or it is
exendospermous.

  [Illustration: FIG. 342.--_Morus alba_ ♂ flower (6/1).]

  [Illustration: FIG. 343.-_Morus alba_ ♀ inflorescence.]

  [Illustration: FIG. 344.--_Morus nigra_ fruits.]

=A.= MOREÆ. The filaments are incurved in the bud. Leaves folded in the
bud--_Morus_ (Mulberry) (Figs. 342–344). Monœcious. The inflorescences
are catkin-like in appearance, but in reality composed of many small
dichasia. The flowers are similar to those of the Nettle, but with 2
carpels: in the ♂ with perianth 2 + 2, and stamens 2 + 2 (Fig. 342),
in the ♀, perianth 2 + 2, and 2 carpels in regular alternation. The
small drupes are enveloped by _the perianth, which eventually becomes
fleshy_, and as all the flowers on the axis very accurately fit
together, the collection of fruits is formed, which we call a Mulberry
(Fig. 344). The leaves are folded in the buds, and have small stipules.
~The following are allied to _Morus_:--_Maclura_, _Broussonetia_ (the
Paper-mulberry tree) which has spheroid ♀ inflorescences (made up of
dichasia), etc.~

   _Dorstenia_ presents an interesting transitional form to the Fig
   in its flat, open, and, in some instances, lobed inflorescence
   on which the ♂ and ♀ flowers are sunk in grooves. Indications
   of a somewhat similar structure are found in certain Nettles,
   the sympodial axes of the dichasia becoming flatly expanded. The
   fruits are 1-seeded, but, nevertheless, spring open and eject
   their seeds.

=B.= ARTOCARPEÆ. Filaments straight in the bud; foliage-leaves with
convolute vernation. An interpetiolar leaf-sheath (ocrea) formed in the
axil of each leaf by the connate stipules, covers the younger leaves
as a hood. It falls off as the leaf expands, and leaves a ring-like
scar on the stem.--_Ficus_ (the Fig). The inflorescence (the so-called
syconus) has a pear-shaped, fleshy, but hollow axis, on the interior
surface of which the flowers are situated (Fig. 345). It is a kind
of capitulum, with a hollow receptacle, whose “involucral” leaves
close over the entrance to the interior; it is not, however, a simple
capitulum, but a coalescence of cymose inflorescences. The edible parts
are the fleshy stem-portion and perianth-leaves. The ♂-flower has a
2–6 divided perianth, 1–2 (–6) stamens; the ♀-flower has an oblique
ovary. The fruits are drupes, with thin flesh.--~Many species have
aerial roots, and some live as epiphytes on trees. POLLINATION, in the
edible Fig, is effected by a small Gall-wasp (_Cynips psenes_ L.),
which lays its eggs in the Fig, and hence carries the pollen away. Even
in very ancient times it was customary to hang infected wild Figs on
the branches of cultivated ones, so that the young Gall-wasps, as they
emerged, could immediately effect the pollination (caprification).
_Ficus carica_, and other species, have two kinds of ♀-flowers, besides
the ♂-flowers. One kind has a short style and no stigmatic hairs,
and it is only in the ovaries of these that the wasps lay their eggs
(gall-flowers); the other kind has a long style and well-developed
stigmatic-hairs, but the wasps cannot reach their ovaries--these are
“seed-flowers.” There are, moreover, two kinds of plants of _Ficus
carica_; ♀-plants, which have only seed-flowers, and bear the edible
Figs, and ♂-plants (called “Caprificus”), which bear inedible fruits,
and have ♂-flowers at the upper part of the Fig, but gall-flowers at
the base. [The Caprificus, at Naples, bears three crops of inedible
Figs each year, viz. _Mamme_ (April), _Profichi_ (June), _Mamnoni_
(August). The ♂-flowers are produced especially in June, the first
Figs being almost entirely ♀, and the last having but few ♂-flowers.
Each crop produces a new generation of Fig-wasps. The female wasp
enters the Figs on the Caprificus, and lays one egg in each flower,
with the result that the flower developes into a kind of gall. The
mother-wasp dies within the Fig. The male wasp is wingless; it bites
a small passage into the ovaries containing the female wasps, and
impregnates them; the female wasps then escape from the Fig, those in
the _Profichi_ carrying pollen away with them as they pass out. They
then enter another Fig, lay their eggs, and die. The edible Fig-tree
similarly has three crops in the year, _Fiori di fico_, _Pedagnuoli_,
_Cimaruoli_. The wasps, entering these Figs, are unable to lay their
eggs in the ovary, but, nevertheless, they effect cross-pollination on
entering the _Pedagnuoli_, which bear fertile seeds.]~

  [Illustration: FIG. 345.--A Fig in longitudinal section.]

   The flowers of _Brosimum_ are the most reduced. The perianth
   is wanting, and the ♂-flower has only 1 stamen. _Cecropia_
   (Trumpet-tree), in S. Am., has its pith divided into chambers;
   these are inhabited by ants, which feed upon small food-bodies
   formed on the swollen base of the petioles. The leaves are
   petiolated, often shield-like, fringed or lobed, and sometimes
   with white felted hairs. They serve as food for  _Bradypus_
   (the Sloth). _Sorocea_; _Castilloa_.

   About 300 species exclusively in the warmer climates. The white
   Mulberry (_M. alba_, from China, India, Mongolia) is cultivated
   for the sake of its leaves, which are the indispensable food
   for silkworms. The black Mulberry (_M. nigra_, W. Asia) is
   cultivated for its fruits, which are used for the officinal
   Mulberry juice. The ordinary Fig-tree (_Ficus carica_) is from
   the Mediterranean. The fruit of the well-known Oriental Sycamore
   (_F. sycomorus_) is edible. The Bread-fruit tree (_Artocarpus
   incisa_) and the Jack (_A. integrifolia_) have their home in the
   South Sea Islands, and are cultivated in tropical countries.
   The Bread-fruit is morphologically the same as the Mulberry. It
   has a very large, spheroid inflorescence, whose floral-leaves
   and perianth become fleshy and united into one nutritious mass,
   together with the axis, which is also fleshy. The milky juice
   of the India-rubber tree (_Ficus elastica_, East Indies, a
   common house-plant), and of _Castilloa elastica_ (Am.) is the
   raw material of India-rubber. The milky juice of _Galactodendron
   utile_ (Cow-tree, S. Am.) is saccharine and nutritious, but in
   _Antiaris toxicaria_ (the Upas-tree, of Java) it is a strong
   poison. The bast of the Paper-Mulberry tree (_Br. papyrifera_,
   Eastern Asia); is used in Japan for paper. Shellac is obtained
   from a small, hemipterous insect (_Coccus lacca_), which lives
   upon _Ficus laccifera_ and _F. religiosa_ (the Bo-tree, sacred
   to Buddha), E. India. The wood of _Maclura aurantica_ (Am.) has
   a yellow colour, and is known as yellow Brazilian wood.

Order 4. =Cannabaceæ.= The plants which belong to this order are
_aromatic herbs_, either annuals or perennials, _without latex_.
Leaves _palminerved_, and more or less divided, hispid, and with free,
persistent stipules. Flowers always _diœcious_; ♂-flowers in panicles,
formed of dichasia, passing over into uniparous scorpioid cymes. They
differ from the Nettles, particularly in the 5-leaved perianth of the
♂-flower, the 5 stamens (Fig. 346–351) with filaments _erect_ in the
bud, and in the ♀-flower by the small, entire, cup-like perianth, which
surrounds the base of the ovary (Fig. 346, p. 352). The ovary has two
styles, or one divided into two, with two stigmas and a pendulous,
curved ovule (Fig. 346 _B_, 352 _B_); the fruit is a nut; the _embryo_
is _curved_ (Hemp, Fig. 353), or rolled (Hop, Fig. 349), _without
endosperm_.

  [Illustration: FIG. 346.--Diagram of male and female flowers of
  the Hop and Hemp: _b_ the bract, _p_ the perianth. The position
  of the embryo is indicated.]

Only 2 genera with 3 species (Asiatic), of which two are
cultivated.--_Humulus lupulus_ (Hop, Figs. 347–349) is a twining,
perennial plant, twisting to the right, with opposite, palmilobed,
rough leaves, and large, interpetiolar stipules. The ♀-flowers are
situated in closely-flowered, cone-like, compound inflorescences, with
ultimately large, thin, imbricate floral-leaves (Fig. 348) which bear
the yellow, glandular hairs, containing lupulin. ~This inflorescence is
made up as follows:--The most external floral-leaves are situated in
pairs, and are the persistent stipules of a leaf, the blade of which
has become suppressed, or in any case is rudimentary. Such a pair of
stipules supports 4 (2–6) flowers in a double uniparous cyme, whose
central axis does not develope into a flower. The bracts of these
flowers (bracteoles of the partial inflorescence) become, at maturity,
very large, spathe-like, and, together with the stipules, produce a
cone-like appearance.~

  [Illustration: FIG. 347–348.--_Humulus lupulus_: 347, twining
  stem; 348, branch with strobiles.]

_Cannabis sativa_ (Hemp, Figs. 350–353) is an East Indian herb, with
palmilobed leaves, and differs from the Hop in being annual, erect,
and in having its leaves opposite at the base and scattered above.
The ♀-inflorescence is not cone-like as in the Hop, but the flowers
are similar in construction. ~The main difference is to be found in
the axillary shoot, which was suppressed in the Hop, and is in the
Hemp developed into a leaf-bearing shoot which on each side bears only
one ♀-flower, and in the fact that the bracts are not so strongly
developed.~

   The “Hops” (the female inflorescences) are used in brewing,
   and medicinally on account of the yellow glands which contain
   lupulin. The Indian variety of _Cannabis sativa_ contains
   an abundance of glandular hairs and resin. The withered
   inflorescences are used in medicine and are officinal. The bast
   of the stems of the Hemp is also used and the fat oil of the
   seeds. In Oriental countries the entire plant is used in the
   preparation of an intoxicating drink (haschisch), the narcotic
   material being found in the glandular hairs.

  [Illustration: FIG. 349.--_Humulus lupulus_: fruit in
  longitudinal section.]

  [Illustration: FIGS. 350–353.--_Cannabis sativa_:

  Fig. 350, ♂-plant;

  Fig. 351, ♂-flower;

  Fig. 352, ♀-flower, entire and in longitudinal section;

  Fig. 353, fruit in longitudinal section.]


                      Family 6. =Polygonifloræ.=

This family is on one side closely allied to the _Urticaceæ_ by its
solitary, _basal_, _vertical_, and _straight_ ovule, and by the conical
ocrea which envelopes the younger leaves in the bud, similar characters
being present in the Urticaceæ. On the other side it is related to
the Curvembryæ. The flowers are small, often _trimerous_, regular and
slightly perigynous (~in _Chloranthaceæ_, if they properly belong to
this family, and _Houttuynia_, more or less epigynous~). Syncarps are
present in some Piperaceæ, but the fruit is generally a single fruit,
one-seeded berry, nut or drupe. The leaves are generally scattered.

Order 1. =Polygonaceæ.= The majority are herbaceous plants with
round, often jointed stems, scattered leaves and _ocrea_, that is a
membranous, tubular, ligular or stipular structure _inside_ the base
of the leaf, which clasps the stem and axillary bud; the edges of the
lamina are rolled backwards in the bud. The flowers are regular, small,
generally ☿, slightly perigynous, with inconspicuous, simple, green or
white perianth of 5–6 free segments; stamens 5–9 (Fig. 354) sometimes
arranged in two series; gynœceum 2–3 carpels, ovary _unilocular_ with
_one basal_, _straight_ (orthotropous) _ovule_, 2–3 _free styles_.
The fruit is a 2–3-angular nut; the embryo, with mealy endosperm,
is straight or curved (Fig. 355 _H_), often unsymmetrical.--~The
inflorescences are compound, and generally branch from the axils of
the bracteoles, so that the last partial-inflorescences become coiled,
uniparous scorpioid cymes; in _Polygonum_ the two bracteoles unite into
a membranous tube; in _Rheum_ and _Rumex_ there is only one bracteole.~

  [Illustration: FIG. 354.--_A_ Diagram of _Rheum_; _B_ of _Rumex_;
  _C_ of _Polygonum fagopyrum_; _D_ of _P. lapathifolium_. The
  ovules are indicated inside the ovaries; bracts and bracteoles
  are not shown.]

_Rheum_ (Rhubarb, Fig. 354 _A_) has a 6-leaved, _petaloid_ perianth (Pn
3 + 3) and 9 stamens (A 3^2 + 3). The _3-winged_ nut is _not_ enclosed
by the perianth.

_Rumex_ (Dock, Fig. 354 _B_) has 6 stamens (A 3^2 + 0); the perianth is
6-leaved (Pr 3 + 3), green or red, and the triangular nut is enveloped
by the 3 interior perianth-leaves, which point upwards and continue to
grow after flowering. These perianth-leaves often have warts on their
outer surface. ~The following are monœcious: _R. acetosa_ and _R.
acetosella_.~

_Polygonum_ (Knot-grass, Figs. 354 _C_, _D_; 355). The _petaloid_
perianth is most frequently 5-merous (2/5 spiral); 5–8 stamens. The nut
is triangular (Fig. 354 _C_, 355), or lenticular (Fig. 354 _D_). ~There
are two whorls of stamens, the external with introrse, and the internal
with extrorse anthers. The gynœceum is often bicarpellate (Fig. 354
_D_).~

   The flowers may be considered as constructed upon the
   monocotyledonous type. _Pterostegia_ has a perfectly
   monocotyledonous flower with 5 trimerous whorls. _Rheum_
   likewise, but here the external staminal whorl is doubled (Fig.
   254 _A_). _Oxyria_ has a dimerous _Rheum_-flower (4-leaved
   perianth, 6 stamens, 2 stigmas). _Rumex_ has a _Rheum_-flower
   with the suppression of the internal whorl of stamens (Fig.
   354 _B_); _Emex_ is a dimerous _Rumex_. _Polygonum_, to which
   _Coccoloba_, _Muehlenbeckia_ and others are related, differs
   from _Rheum_ chiefly in having one of the leaves, which in the
   latter takes part in the formation of the perianth, developed
   in this case into a bracteole (so that the perianth is reduced
   to five members), and several or all the stamens in the inner
   whorl become suppressed.--The perianth in _Coccoloba_ and
   _Muehlenbeckia_ is more or less perigynous and becomes fleshy,
   enclosing the fruit. _Muehlenbeckia platyclada_ has flat branches
   with rudimentary leaves; sometimes branches with normal,
   arrow-shaped leaves are found. _Atraphaxis._

  [Illustration: FIG. 355.--_Polygonum fagopyrum_: _A_ branch
  with flower and fruits (nat. size); _B_ flower; _C_ the same
  in longitudinal section; _D_ anterior and posterior view of
  stamen; _E_ gynœceum; _F_ fruit (mag.); _G_ fruit in longitudinal
  section; _H_ transverse section, showing the curved cotyledons
  embedded in the endosperm; _I_ the embryo.]

   POLLINATION. _Rumex_ is wind-pollinated, the stigmas are
   therefore large and brush-like (indicated in  Fig. 354 _B_).
   _Rheum_ and _Polygonum_ are insect-pollinated and have therefore
   capitate stigmas, etc.; honey-glands are situated at the base
   of the stamens (_d_, in Fig. 354 _C_, and _n_ in Fig. 356); a
   few small-flowered _Polygonum_ species are self-pollinated;
   Buckwheat (_P. fagopyrum_) is dimorphic and has long-styled and
   short-styled flowers (Fig. 356). _Pol. bistorta_ is protandrous
   and homostyled.

   About 750 species, most of which are found in the temperate
   regions of the Northern Hemisphere, some reaching as far as the
   snow line or into the Arctic regions (_Oxyria_, _Kœnigia_).
   Trees and shrubs are found in the Tropics: _Coccoloba_,
   _Triplaris_. _Rheum_ is Central Asiatic.--The thick rhizomes of
   _R. officinale_ (_Rhubarb_) are _officinal_. The rhizomes of the
   ordinarily cultivated species, _R. undulatum_ and _rhaponticum_,
   are used in veterinary medicine. The following are cultivated as
   culinary plants for the sake of their leaves:--_Rumex acetosa_
   (Sorrel), _R. patientia_, _R. scutatus_, and _Rheum undulatum_
   (petioles). Several species of _Polygonum_ (_P. hydropiper_ and
   others) have a sharp, pungent taste. “Buckwheat” is the mealy
   fruit of _Polygonum fagopyrum_ (Central Asia) and is of value as
   a farinaceous food. _P. cuspidatum_ (_P. sieboldi_, Japan) is an
   ornamental plant.--_Calligonum_ in sandy and stony deserts.

  [Illustration: FIG. 356.--Flower of _Polygonum fagopyrum_ in
  longitudinal section: 1, long-styled; 2, short-styled; _a_ the
  anthers; _st_ the stigmas; _n_ nectary.]

Order 2. =Piperaceæ (Peppers).= Shrubs or herbs, often with nodose,
jointed stem; leaves simple, entire, often with curved veins; stipules
wanting (_Peperomia_) or intrapetiolar and cap-like, often enclosing
the terminal buds (_Piper_). The flowers in the group _Pipereæ_
(_Piper_, Fig. 357, and _Peperomia_) are borne in spikes with fleshy
axes (_club-like_), seldom in racemes, the outer ones are crowded and
are ☿ or unisexual, always small, _naked_ and without bracteoles;
~generally stamens 3 + 3, and gynœceum 3, but the number of the
stamens may be reduced by suppression to 2, and the carpels to 1~. The
flowers are situated in the axils of the small, generally shield-like
floral-leaves. The ovary is always _unilocular_ and has _one upright,
orthotropous_ ovule. Fruit a berry or drupe. Both endosperm and
_perisperm_ are present, the latter being especially well developed
(Fig. 359).

_Piper_; generally shrubs with scattered leaves, and terminal
inflorescences which are crowded to one side by the development of the
highest lateral bud, so that they are situated opposite the leaves
(Fig. 357). Many species have stems with an abnormal anatomical
structure.--_Peperomia_; chiefly succulent herbs, often epiphytes, with
opposite or verticillate leaves having aqueous tissue on the upper side.

  [Illustration: FIG. 357.--_Piper nigrum_: branch with fruit (½)]

   The group _Saurureæ_ (considered by some as an order, and
   perhaps representing a more original type) has 3–4 carpels
   with many ovules. _Lactoris_ stands the highest with regular
   3-merous perianth, 3 + 3 stamens and 3 carpels, which are
   united at the base. Fruit a capsule with several seeds. (It
   has one species from the island of Juan Fernandez, and is also
   placed in an order of its own, Lactoridaceæ, allied to the
   Magnoliaceæ, through _Drimys_).--_Saururus_ has naked flowers;
   most frequently 6 stamens, and 4 carpels, free or united at
   the base, each with 2-4 orthotropous ovules. Fruit, small
   berries.--_Houttuynia_; stamens situated a little upward on the
   ovaries; placentation parietal; capsule many-seeded.

   About 1,000 species; entirely tropical, especially from
   South America and East India. They are found chiefly among
   the underwood in damp, shady places; some, which are fleshy
   (_Peperomia_), live as epiphytes on trees; a few climb by
   roots.--USES. Several Piperaceæ are used medicinally and
   for spices on account of their pungent properties and the
   essential oils found in nearly all parts of the plant. The
   following are _officinal_: “Black-pepper” (the unripe, dried
   fruits) and “White-pepper” (the seeds of the ripe fruits) of
   _Piper nigrum_ (climbing shrub, East Indian); “Cubeb” berries
   of _P. cubeba_ (climbing shrub, Java). “Long-pepper” is the
   unripe inflorescence of _P. longum_, East India. The leaves of
   _P. angustifolia_ (Matico) are officinal. The leaves of the
   Betelpepper (East India) are used together with the nuts of
   the Areca-palm to form the well-known East Indian intoxicating
   compound “Betel.” A good many others are also used.

  [Illustration: FIG. 358.--_Piper nigrum_ (Diagram). In addition
  to the bract there are two structures resembling bracteoles.]

  [Illustration: FIG. 359.--_Piper nigrum_: Fruit in longitudinal
  section, showing the endosperm, perisperm, and pericarp.]

   Order 3. =Chloranthaceæ.= (_Chloranthus_, _Hedyosmum_) have
   opposite leaves, with stipules more or less united at the base,
   and inferior “drupes.” Ovules pendulous. Only endosperm. About
   33 species, Tropical.


                        Family 7. =Curvembryæ.=

The plants in this family have a _curved ovule_, and most frequently
a _kidney-shaped seed_ (generally provided with fine, cuticular,
projecting warts, Fig. 362 _B_), with a _curved, peripheral embryo
enclosing the endosperm which is most frequently floury_ (Figs. 362
_C_, 365 _H_; for exceptions, see Fig. 366); the seeds in all cases
are borne on a _centrally-placed_, and in most cases _free_, placenta
(they are “basal” when there is only 1 ovule in the ovary, Fig. 364).
The flower is regular, hypogynous or perigynous (Fig. 364) (only
rarely epigynous) and usually 5-_merous_. The flower which is most
complete has 5 whorls (S5, P5, A5+5, G2-3–5), as in some genera of
the Caryophyllaceæ (Figs. 360, 361); but from this type it becomes
reduced, the petals and stamens being suppressed, so that finally
5 perianth-leaves, 5 stamens (opposite the perianth-leaves), and 2
carpels (Fig. 361 _F_) only are present; for example, in certain genera
of the _Caryophyllaceæ_, in the _Chenopodiaceæ_, _Amarantaceæ_, and
others. When the number of stamens is increased to more than 5 in the
whorl, it is always possible to show that some of the stamens have been
divided. The number of the carpels and ovules also becomes reduced; in
the highest there is a central placenta, not free in its early stages,
with a large number of ovules; in those which are most reduced there is
only a single ovule, which is placed centrally at the base of the ovary
[Fig. 364]. Somewhat corresponding changes are found in the fruit,
which is a many-seeded _capsule_ in those which have many ovules, but
a one-seeded _nut_ where there is one ovule. In the most reduced forms
the flowers are generally unisexual.--Similar features are also present
in the vegetative parts. Almost all the species are herbaceous, the
leaves are simple and most frequently without stipules. ~The structure
of the stem, especially in Chenopodiaceæ, Amarantaceæ, Nyctaginiaceæ
and others, often differs from that of the ordinary Dicotyledon. In the
woody portion of the stem and root several rings are sometimes formed
which resemble annual rings but which are formed by new cambium-rings
arising outside the old ones which then cease to divide.~

Order 1. =Caryophyllaceæ.= Herbaceous plants, with round, nodose
stem; leaves _opposite_, slightly amplexicaul, simple, with sessile,
undivided, entire lamina; stipules nearly always absent; the
inflorescences are _dichasia_ passing over into unipared scorpioid
cymes. The flowers are regular, ☿ or unisexual, hypogynous or
perigynous, 5-(or 4-) merous with 2–3–4–5 carpels; calyx persistent;
corolla polypetalous. The ovary is unilocular (or originally, and
sometimes also in the later stages, plurilocular below, _e.g._
_Viscaria_), with _free styles_ and 1–several curved ovules on a
_central_, free placenta. The fruit is a nut or a capsule opening
apically with long or short valves (teeth, Fig. 362), equal to or
double the carpels. For the seeds refer to the family. ~In _Dianthus_
the embryo is straight.~

   The flowers which are most complete have _Sn_, _Pn_, _An_ + _n_
   (obdiplostemonous), _Gn_ where _n_ = 5 (Figs. 360, 361 _A_) or
   4 (Fig. 361 _B_); the carpels may be placed opposite to the
   sepals (Fig. 360) or opposite to the petals (Fig. 361 _A_, _B_).
   Without any change taking place in the position of the other
   whorls, the carpels are next found reduced to 2–3–4 (see the
   genera); their number may easily be recognised by that of the
   styles. This is the construction in the majority of the genera
   in the two first groups. _Stellaria media_ differs considerably.
   It may have (_a_) the flower as described above, with _G3_;
   (_b_), the corolla only absent, or (_c_) only the petal-stamens
   (A5 + 0, Fig. 361 _C_), or (_d_) all these as well as some of
   the sepal-stamens. The same applies to _Sagina_, _Alsine_,
   _Cerastium_, and others, and, finally, a series of genera are
   formed, with certain conditions of reduction which have become
   constant, and by a gradual series of steps lead to the most
   reduced form, which has only 5 sepals and 5 (or even as far as
   only 1) sepal-stamens (Fig. 361 _D_, _E_, _F_).--The PETALS in
   the _Alsineæ_ are often deeply bifid. The sepal-stamens are most
   frequently the longest, and bear nectaries at the base (Fig. 363
   _st_). In the most complete forms the ovary has partition-walls
   in the lower portion (Fig. 360); these do not, however, reach
   to the top, and generally soon disappear. The ovules, when
   numerous, are situated on the placenta in as many double rows as
   there are carpels. In the number of ovules a reduction from many
   to 1 takes place (Fig. 361). A comparison proves that the “free,
   centrally placed” placenta is formed by the ventral portion of
   the carpels. The single basal ovule in _Herniaria_ (Fig. 364),
   _Scleranthus_, and others, is also borne on the carpels.

   The vegetative _branching_ is characteristic. One of the leaves
   in a pair is formed before the other, and has a more vigorous
   axillary bud; these stronger leaves stand in a ¼-spiral, the
   fifth above the first one, and the branches are consequently
   arranged in the same manner. In the inflorescence, however, it
   is the upper or second bracteole (β) whose axillary bud (_w_ in
   Fig. 361) is most advanced. The bud of the first bracteole (α)
   becomes sometimes entirely suppressed, or in some this bracteole
   itself is suppressed.

  [Illustration: FIG. 360.--Diagram of _Lychnis_: α, β bracteoles.]

  [Illustration: FIG. 361.--_A-F_ Diagrams of flowers of the
  Caryophyllaceæ: _A Agrostemma_; _B Sagina_; _C Stellaria_;
  _D Corrigiola_; _E Paronychia_; _F Herniaria_.]

   The most original type appears to be represented by the Alsineæ.
   From this form on one side the Sileneæ, adapted in a higher
   degree for insect-pollination, are developed, and on the other
   side the Paronychieæ, with various reductions.

=1.= ALSINEÆ, STITCHWORT GROUP. Sepals free, and connected with them
stellately expanded, slightly unguiculate (white or inodorous) petals;
these, however, often become suppressed (Fig. 363). The fruit is a
capsule.

  [Illustration: FIG. 362.--_Cerastium arvense_: _A_ fruit; _B_
  seed; _C_ section of seed.]

=a.= As many carpels as sepals (4 or 5). _Cerastium_ (Chickweed). The
petals are bifid. Capsule cylindrical, frequently _curved_ at the top,
and opening by 10 teeth (Fig. 362).--~_Malachium_ differs only in the
5-toothed capsule with bifid teeth.~--_Spergula_ (Spurry). The petals
are not bifid, capsule 5-valved; seeds winged. The leaves are linear,
and appear as if placed in large numbers in a whorl, a branch being
situated in the axil of each with leaves placed very close together at
its base; _stipules membranous_.--~Sagina has Sn, Pn, An + n, or An,
Gn, where n = 4 or 5. The corolla is often wanting.~

=b.= 3 (rarely 2) carpels (Fig. 361 _C_). _Stellaria_ (Stitchwort)
has deeply cleft petals. The number of stamens varies (see
above).--_Arenaria_ has entire petals. ~(To this group belong _Alsine_,
_Moehringia_, _Halianthus_, or _Honckenya_ (Fig. 363), which differ
from each other, especially in the form of the seed and number of
the capsular valves.) _Spergularia_ has membranous stipules, as in
_Spergula_.--_Holosteum._~

  [Illustration: FIG. 363.--_Arenaria_ (_Halianthus_) _peploides_:
  ♀-(_A_) and ♂-flower (_B_, _C_).]

=2.= PARONYCHIEÆ (Figs. 361 _D_, _E_, _F_; 364). Small, greenish
plants. The leaves, in the majority, are opposite, with _membranous
stipules_. The flowers are most frequently arranged in small
_dichasia_; they are small and insignificant, perigynous (Fig. 364)
or hypogynous. The corolla is in most cases wanting, and when present
is very small; in general the calyx-stamens are developed, but the
corolla-stamens may be represented by small scales (Fig. 364). Ovary
most frequently with 1 ovule. Fruit, a _nut_, rarely a capsule; it is
enclosed by the strongly perigynous floral axis (torus).

_Scleranthus_ (Knapwell) is perigynous with bell-shaped torus; no
corolla; corolla-stamens are wanting or rudimentary; some calyx-stamens
may also be absent.--_Corrigiola_ (Fig. 361 _D_); _Illecebrum_;
_Paronychia_ (Fig. 361 _E_); _Herniaria_ (Figs. 361 _F_, 364).

=3.= SILENEÆ, PINK OR CARNATION GROUP. This has a _gamosepalous_ calyx
and unguiculate, white or red, petals, with _outgrowths_ (_ligule_,
_corona_, _paracorolla_) at the throat of the corolla. These structures
are not found in the other groups, and are merely outgrowths at
the junction of the limb and claw. The corolla, stamens and ovary
are frequently raised above the calyx, upon a lengthened internode
(_gynophore_). The flower has S5, P5, A5 + 5; fruit a capsule with many
seeds.

=a.= 5-(rarely 3–4) carpellate ovary.--_Lychnis_ (Campion, Fig. 360).
The corolla is longer than the calyx; corona present. The capsule
is 10- or 5-toothed, completely 1-chambered or 5-chambered at the
base,--the genus has been divided accordingly into several genera:
_Melandrium_, _Lychnis_, _Viscaria_. ~Some species are unisexual by
the abortion of stamens or carpels (_L. vespertina_, _diurna_).~
_Agrostemma_ (_A. githago_, Corn-cockle, Fig. 361 _A_) has a
long-toothed calyx, the teeth exceeding the corolla; corona absent;
5-toothed capsule.

  [Illustration: FIG. 364.--_Herniaria glabra_: _a^1_ flower; _b^1_
  longitudinal section through the flower; _c^1_ stigma with two
  pollen-grains.]

=b.= Tricarpellate.--_Silene_ (Catch-fly). Six-toothed capsule; corona
present in the majority.--~_Cucubalus_ has berry-like fruits which
finally become dry but do not dehisce.~

=c.= Bicarpellate (2 styles, 4-toothed capsule).--_Dianthus_
(Pink); at the base of the calyx 1–several pairs of floral-leaves
are situated; corona absent. The _straight embryo_ is a peculiar
exception.--_Gypsophila_ has a campanulate, open calyx, 5-nerved,
membranous between the nerves; corona absent; the flowers are generally
small and numerous, in a large, paniculate dichasia.--_Saponaria_
(Soapwort) has corona.

   POLLINATION. _Alsineæ_ has ordinary nectaries at the base of
   the calyx-stamens (Fig. 336): they are frequently protandrous
   but may often, in the absence of cross-pollination (in the
   less conspicuous species) pollinate themselves. Their open
   flowers are accessible to many kinds of insects (particularly
   flies and bees). _Gynodiœcious_ flowers are found in several
   species, and the ☿-flowers are then generally more conspicuous
   than the ♀-flowers. That the ♀-flowers have descended from
   ☿-flowers is seen by the large staminodes found in them (Fig.
   363). _Arenaria peploides_ is diœcious (Fig. 363). The _Sileneæ_
   are as a rule adapted for pollination by insects with long
   probosces--especially butterflies,--and they are frequently
   protandrous, so that at first the calyx-stamens open, later
   on the corolla-stamens, then the stigmas expand. The honey is
   secreted by a ring-like nectary round the base of the ovary or
   by nectaries at the base of the stamens. Some only blossom and
   emit scent at night or in the evening (_Lychnis vespertina_,
   _Silene nutans_, _Saponaria officinalis_) and, like other
   night-flowers, are of a white or pale colour.

   DISTRIBUTION. 1,100 species, especially in temperate climates,
   fewer in the colder zone, less still in the Tropics. The
   Paronychieæ are especially found in dry, sandy fields.

   USES. “Soap-root” (with _Saponin_, forming a lather in water)
   from _Saponaria officinalis_ was formerly officinal, and
   _Gypsophila struthium_. The seeds of _Agrostemma githago_ are
   said to be poisonous.--The following are ornamental plants:
   species of Pinks (_D. caryophyllus_, garden Pink, often
   with double flowers; _D. barbatus_, _plumarius_, _etc._).
   _Lychnis_, _Gypsophila_, _Silene_, _Cerastium_ (_C. tomentosum_
   as edging for borders), _Saponaria officinalis_ (often
   coronate).--_Spergula arvensis_ is sometimes cultivated.

   Order 2. =Amarantaceæ.= The flowers are essentially the same as
   in the _Chenopodiaceæ_ and the extremely reduced Caryophyllaceæ
   (Fig. 361 _F_); they are regular, hypogynous, generally ☿,
   have 5 free (rarely slightly united) perianth-leaves; in front
   of these 5 stamens, which _are often united_ at their base
   into a shorter or longer tube and have stipule-like teeth
   between them (the division _Gomphreneæ_ has 2-locular anthers,
   each of which opens longitudinally); and a 2–3 carpellate
   gynœceum with one loculus and most frequently one, more rarely
   several ovules; the fruit is a nut, more rarely (in _Celosia_,
   _Amarantus_, _Gomphrena_) a capsule, dehiscing irregularly,
   or like a pyxidium. The characters which especially separate
   them from the allied orders are found in the perianth. The
   perianth-leaves are not green and herbaceous, but _membranous,
   dry, and often coloured_; they are frequently produced into a
   bristle or awn; they have also both subtending floral-leaves
   and _2 large bracteoles similar to the perianth_; all these dry
   leaves persist without alteration after the withering of the
   flower.--The flowers are without scent. They are arranged in
   spike- or capitulum-like inflorescences; sometimes placed singly,
   sometimes aggregated in the panicle-like inflorescences; in
   others, on the contrary, in dichasia. The majority are herbs,
   some are shrubs. The leaves are scattered, or opposite, but
   always simple and without stipules; some are smooth, others
   hairy.

   450 species; especially in the Tropics, principally S. Am. and
   E. Ind.: few are found outside these countries.--Only a few
   are used; some, chiefly E. Indian species, are cultivated as
   ornamental plants: _Amaranthus_ (Fox-tail); _Gomphrena globosa_;
   _Celosia cristata_ (Cock’s-comb) remarkable for its fasciated
   inflorescence; _Alternanthera_. Some are employed as culinary
   plants in the Tropics, and in a few of the E. Indian species the
   seeds are farinaceous, and used for food.

Order 3. =Chenopodiaceæ.= Generally herbaceous plants like the
Caryophyllaceæ, but the leaves are arranged spirally (except
_Salicornia_), and are simple, exstipulate; they are generally fleshy
and like the stem “mealy,” that is, covered with small hairs, whose
large spherical terminal cell readily falls away; otherwise they are
seldom hairy. The inflorescences are generally flower-clusters borne in
panicles. Bracteoles generally absent. Flowers generally _unisexual_:
with the single exception of _Beta_ the flowers are hypogynous; they
are regular, small and inconspicuous, with _single, green_, 5-leaved,
but _more or less united_ perianth; 5 stamens opposite the perianth,
and a _2–5-carpellate, unilocular_ ovary with 1 basal, curved ovule;
but in some genera the number of the perianth-leaves and stamens is
reduced to 3–2–1–0. The fruit is generally a _nut_,--thus this flower
and fruit are the same as in the reduced Caryophyllaceæ (Fig. 361
_F_). The seed is similar to that generally found in the family (for
exceptions see the genera).

   The floral diagram most frequently present is the same as
   in Fig. 361 _F_. There is no indication of corolla or of
   corolla-stamens, which may be supposed to have belonged
   to the plant, but which are now entirely and completely
   suppressed. This order appears to have been an offshoot from
   the Caryophyllaceæ.--The perianth persists after the withering
   of the flower, and envelopes the nut; it is very variable, and,
   together with the position of the seed, the form of the embryo,
   the sex of the flowers, etc., gives the characters of the genera.

=1.= CHENOPODIEÆ, GOOSEFOOT GROUP (Fig. 365), has ☿ (or polygamous)
flowers, with regular 5-parted perianth (_C_); the embryo is ring-like
(_H_). The leaves have the ordinary flat forms.--_Chenopodium_
(Goosefoot). The flower is hypogynous, and the fruit (which is
compressed) perfectly free; Mulberry-like collections of fruits are
formed in some species (sub-genus _Blitum_) by the perianth becoming
finally fleshy and coloured.--_Beta_ (Beet, Mangold, Fig. 365) differs
from all genera in the perianth, which finally becomes cartilaginous,
being epigynous (_D_). Small, most frequently 2–3-flowered clusters
without bracteoles, situated in a long, interrupted axis (_A_, _B_);
the flowers and fruits in each cluster are more or less united
individually, and fall off together--they are commonly known as seeds
(_E_, _F_). The seed lies horizontally.--_Hablitzia_ (_H. tamnoides_).

  [Illustration: FIG. 365.--_Beta vulgaris._]

  [Illustration: FIG. 366.--_Salsola soda_: embryo.]

=2.= SALSOLEÆ, SALTWORT GROUP, has cylindrical or semi-cylindrical
leaves. Perianth as in the preceding group; the fruit is most
frequently compressed. The two first mentioned genera differ from
most of the others in the order in having a spirally-coiled, and not
a ring-like embryo, so that the endosperm is slight or wanting (Fig.
366). These plants are sometimes placed as a group by themselves,
SPIROLOBEÆ--in contradistinction to which the others are termed
CYCLOLOBEÆ.--_Salsola_ (Saltwort); leaves subulate, with spiny tips;
the flowers have 2 spinous bracteoles: during the ripening of the
fruit a tough leathery wing is developed transversely to the back of
the perianth.--~_Chenopodina_ deviates from _Chenopodium_ chiefly in
the embryo and want of endosperm.--_Kochia_ has a somewhat similar
perianth to _Salsola_, but a ring-like embryo; it differs from the
others in being hairy.~

=3.= SALICORNIEÆ, GLASSWORT GROUP. _Salicornia_ (Glasswort) has a very
different appearance. The stems are succulent, jointed, and almost
leafless; the leaves opposite, very small, sheath-like and connate;
there is a depression in the axil of each leaf, in which a small
3-flowered dichasium without bracteoles is sunk; the flowers have
a trimerous perianth, 1–2 stamens and 1 carpel. No endosperm. _S.
herbacea_ on clayey beaches.

=4.= ATRIPLICEÆ. This group has most frequently unisexual flowers;
the ♂-flower has a 4–5 partite perianth, but the ♀-flower differs
from it. _Atriplex_ is monœcious or polygamous, the ♀-flower is
naked, but has 2 large, herbaceous bracteoles which expand during the
ripening of the fruit, and often become warted and fringed, enveloping
the _compressed nut_. ~The section _Dichospermum_ has two kinds of
♀-flowers, one like those just described, the other similar to the
_Chenopodium_-flowers, which have been deprived of their stamens, and
the fruits of which are _depressed_, not pressed together from the
sides; some (_e.g. A. hortensis_) have even three kinds of nuts.
All the flowers of _Atriplex_, which present vertical fruits, are
accessory shoots, which stand beneath the ordinary flower-clusters, a
rather singular relation.~--_Spinacia_ (Spinach) is diœcious; ♂-flower:
perianth, 4 (-5); stamens, 4 (-5); ♀-flower: tubular, 2–4-partite
perianth, hardening during the ripening of the fruit, and uniting with
the compressed nut; in _S. oleracea_, it also forms _thorns_; 4 long
stigmas.--_Halimus_ has the 2 long bracteoles almost entirely united
and ultimately adhering firmly to the fruit.

   =5.= BASELLEÆ. A somewhat exceptional group with more
   or less perigynous flowers and 2 bracteoles. _Basella_,
   _Boussingaultia_, _Ullucus_. The perianth is sepaloid; ovary
   1-ovuled. In _Basella_ the perianth is fleshy, enveloping the
   nut, and the cotyledons are so rolled together that a tranverse
   cut divides them in two places (as in Spirolobeæ). Herbaceous
   climbing plants.

   POLLINATION. Wind-and self-pollination, as far as is known;
   the insignificant flowers, devoid of honey, appear to exclude
   insect-pollination.--520 species. Most of them are annual
   (out of 26 native species only 5 are perennial); inhabiting
   salt-marshes and salt-steppes, and growing as weeds (most
   frequently on garden or field soil containing manure) in this
   country, especially species of _Chenopodium_ and _Atriplex_.
   The majority are found outside the Tropics, and play a very
   important part, for example, in the Asiatic salt-steppes. They
   grow gregariously in large masses.

   USES. Comparatively few. The only important one is _Beta
   vulgaris_ (from the Mediterranean basin), with its different
   varieties, viz. Beet-root, Cattle-beet or Red-beet, Sugar-beet,
   and others. These are biennial, making in the first year a root
   which acts as a reservoir of reserve material, with a rosette
   of leaves, and in the second year using this material in the
   production of a long stem, leaves and flowers. The primary
   root has been developed by cultivation into a very thick and
   fleshy tap-root; its mode of increase in thickness deviates
   from that of other roots, concentric rings of vascular bundles
   being formed from a cambial ring developed outside the previous
   ring. In this way several rings of vascular bundles separated
   by medullary rays, alternating with rings of parenchyma, may
   be found in the root of a Beet. Besides _Beta vulgaris_, var.
   _hortensis_ (Beet-root), the following are also cultivated: var.
   _cicla_ (Leaf-beet, “Mangold,” or “Roman Spinach ”), _Spinacia
   oleracea_ and _Atriplex hortensis_ as Spinach; a form of the
   latter and of Spinach are grown as ornamental plants. The tubers
   of _Ullucus tuberosus_ are used as potatoes; _Chenopodium
   quinoa_, in Chili and Peru, is an important farinaceous plant.
   Soda is made from some (_Salsola kali_, _Chenopodina maritima_
   and others). Aromatic properties are rare: _Chenopodium
   ambrosioides_ and _botrys_.

   Order 4. =Batidaceæ.= _Batis maritima_, a bushy West Indian
   maritime plant.

   Order 5. =Phytolaccaceæ.= The ☿ (sometimes unisexual), regular,
   sometimes slightly perigynous flowers are inconspicuous
   and have a single sepaloid or coloured 4–5-leaved perianth
   (generally united at the base); stamens either in 1 whorl in the
   spaces between the perianth-leaves or in 1 whorl opposite the
   perianth-leaves, or in 2, one of which alternates with these;
   but the number may be increased by the splitting of one or of
   both the whorls to as many as 10–15–20–25. _Carpels_ sometimes
   only one, sometimes _many_ (4–10) placed in a whorl, either free
   or united into a gynœceum with a corresponding number of loculi
   in the ovary; but in all cases _each carpel bears only its own
   style and 1 ovule_. The fruit is a _berry_ (or nut, capsule, or
   schizocarp).--Mostly herbs or herbaceous shrubs, with scattered,
   simple leaves without stipules (_Petiverieæ_; have stipules).
   Inflorescences, most frequently _racemes_ or spikes, which in
   some instances are apparently placed opposite to a leaf, being
   displaced by a more vigorous growth of the axillary bud. Embryo
   always bent.--_Petiveria_ has a straight embryo with rolled
   cotyledons.--_Phytolacca_, _Pircunia_, _Microtea_, _Seguieria_,
   _Rivina_ (Pr4, A4, G1; berry), and others.

   The following plant is, with some doubt, placed near this
   order: _Thelygonum cynocrambe_; monœcious. ♂-flowers: perianth,
   2-leaved; stamens indefinite. ♀-flowers: perianth-leaves united,
   3-toothed; G1, style gynobasic. Fruit a drupe. An annual plant;
   Mediterranean. Branching anomalous.

   About 90 species; in tropical and temperate countries,
   principally America and Africa.--The red juice in the fruits,
   especially of _Phytol. decandra_, is used for colouring wine.

Order 6. =Portulacaceæ= (=Portulacas=). The flowers are regular
(except _Montia_), hypogynous (except _Portulaca_) and ☿. The diagram
which applies to the majority of genera is that in Fig. 367, but with
all the 5 stamens completely developed: it may be considered as the
Chenopodiaceous diagram with the addition of 2 _bracteoles_ in the
median line (_m-n_, these by some are considered as sepals), and with
a petaloid perianth (usually designated “corolla”). The “petals” fall
off very quickly, and are sometimes wanting. Most frequently 5 stamens,
situated opposite the “petals,” but in other genera the number varies;
_Montia_ has only 3 stamens (by suppression of the two anterior and
lateral, Fig. 367), others again have more than 5, some a large and
indefinite number. This may be explained partly by the appearance of
a second whorl of stamens alternating with the first, and partly by
the splitting (dédoublement) of the stamens. Gynœceum most frequently
tricarpellate, ovary unilocular with 1–several basal ovules (sometimes
on a branched placenta, as in certain _Caryophyllaceæ_). The fruit is
a _capsule_, more rarely a nut.--The majority are annual herbaceous
plants with scattered, entire leaves, often fleshy and smooth, with or
without rudimentary stipules (dry, membranous, modified into hairs).
Inflorescence cymose.

  [Illustration: FIG. 367.--_Montia._

  Diagram of flower.]

_Portulaca_ (Portulaca): flower, epigynous or semi-epigynous; fruit, a
pyxidium. The stamens vary in number, and are most frequently placed in
groups (in consequence of splitting) opposite the petals.--_Montia_:
the corolla is slightly gamopetalous, but cleft on the posterior side
(Fig. 367), and as a consequence of the larger size of the lateral
petals, slightly zygomorphic; 3 stamens.--_Calandrinia_; _Talinum_;
_Anacampseros_; _Claytonia_.

   125 species; mostly in warm and temperate countries, especially
   the arid parts of S. Am. and the Cape. _Montia fontana_ (Blinks)
   is a native plant. _Portulaca oleracea_ is cultivated as a
   pot-herb in the south of Europe. A few species of _Portulaca_
   and _Calandrinia_ are ornamental plants.

Order 7. =Nyctaginiaceæ.= The characteristic feature of this order
is the _single_, regular, _united_, and often petaloid perianth, the
lower part of which generally persists after flowering and embraces
the fruit as a false pericarp. The upper portion is most frequently
_valvate and folded_, or simply valvate in æstivation. The number of
stamens varies. The free gynœceum is _unicarpellate_ and has 1 ovule.
The fruit is a _nut_, but becomes a _false drupe_, since the lower
persistent portion of the perianth becomes fleshy (as in _Neea_, where
this fleshy part is almost always crowned by the upper persistent
part of the perianth. In the majority of the Mirabileæ the lower part
becomes the dry _anthocarp_, while the upper petaloid part falls away
after flowering). Finally, a peculiar involucre is formed around the
flowers by free or united floral-leaves.--The majority are herbs, some
are trees (_Pisonia_, etc.); _Bougainvillea_ is a liane. The stems
are often nodose and swollen at the nodes; the leaves are simple,
penninerved, scattered, or opposite, without stipules. ~In some, the
vascular bundles are scattered; stem anomalous.~

_Mirabilis_; the structure of the stem is abnormal. Dichasial branching
with continuation from the second bracteole, thus forming unipared
scorpioid cymes. The perianth is petaloid, funnel-shaped, and has
a folded and twisted æstivation resembling that of the corolla of
the _Convolvulaceæ_; the upper coloured portion falls off after
the flowering. Outside, and alternating with it, is a 5-partite,
sepaloid involucre of 5 spirally-placed floral-leaves.--_Oxybaphus_;
the involucre envelops 1–3 dichasial flowers.--_Bougainvillea_; the
involucre is rose-coloured, 3-leaved, and envelops 3 flowers (placed
laterally; the terminal flower wanting). The leaves of the involucre
in _Boerhaavia_, _Pisonia_, _Neea_, and others are reduced to teeth or
scales.

   157 species; mostly in tropical countries, and especially S. Am.
   Species of _Mirabilis_ (Am.) are ornamental plants. Theïn is
   found in _Neea theïfera_ Oersted (discovered by Lund in Lagoa
   Santa, Brazil), which may be used as a tea-plant.

   Order 8. =Aizoaceæ.= Only 3 _whorls_ are found in the flower,
   which _alternate_ with one another when their leaves are equal
   in number. The first is sepaloid, the third one the carpels,
   and the intervening one is either uncleft, in which case it is
   developed as stamens, or it is divided into a large number of
   members which then all become stamens (arranged in groups), or
   the outermost ones become developed as petals. The fruit is most
   frequently a capsule with several loculi. Most of the species
   are herbs with thick, fleshy stems, and exstipulate leaves. The
   structure of the stem is usually anomalous.

   =1.= AIZOIDEÆ have hypogynous or perigynous flowers with (4–)
   5 perianth-leaves; stamens single, or (by splitting) in groups
   of 2–3, alternating with the perianth-leaves. The gynœceum
   (with 3–5 carpels) has 3–5 loculi in the ovary, and most
   frequently numerous ovules in each loculus, borne on the central
   placenta formed by the edges of the carpels. The fruit is a
   capsule. The inflorescences are dichasia and unipared scorpioid
   cymes.--_Aizoon_, _Mollugo_, _Sesuvium_, and others are herbs or
   bushes, most frequently hairy.

   =2.= MESEMBRIANTHEMEÆ have semi- or wholly-epigynous
   flowers.--_Tetragonia._ The perianth is 4 (more rarely
   3–5–6)-merous. Stamens single, or (by splitting) in groups
   alternating with the perianth-leaves. There is an indefinite
   number of carpels, and each loculus of the ovary contains
   _only_ 1 pendulous ovule. Fruit a nut or drupe. The flowers
   arise singly in the leaf-axils, with an accessory foliage-bud
   below them; in some instances there is also an accessory
   flower between this bud and the flower. Southern hemisphere,
   especially at the Cape; _T. expansa_, New Zealand Spinach, is a
   fleshy plant which is cultivated as a pot-herb (Japan, Austr.,
   S. Am.).--_Mesembrianthemum_: the flowers are 5-merous; the
   numerous linear petals and the still more numerous stamens all
   arise by the splitting of 5 or 4 protuberances (primordia)
   alternating with the sepals. The ovary presents another
   characteristic peculiarity: the carpels alternating with the
   5–4 stamens form an ovary (with several loculi) with the ovules
   at first borne, as in other cases, on the _inner_ corner of the
   inwardly-turned carpels; but during the subsequent development
   the whole ovary is so turned round that the placentæ become
   parietal and the ovules assume, apparently, a position very
   rarely met with in the vegetable kingdom: on the dorsal suture
   of the carpels. Shrubs or under-shrubs, more rarely herbs
   with fleshy stems and simple, entire, more frequently thick
   or triangular leaves, containing a quantity of water. The
   flowers open about noon, and are brightly coloured, generally
   red or red-violet, but odourless. The capsules dehisce in
   rainy weather. 300 species, mostly found at the Cape. Some are
   ornamental plants. _M. crystallinum_ (the Ice-plant) and others
   are covered with peculiar, bladder-like, sparkling hairs, the
   cell-sap of which contains salt--these serve as reservoirs of
   water.


                        Family 8. =Cactifloræ.=

The position of this family is very doubtful; but it seems in many
respects to approach _Mesembrianthemum_. Some botanists place it near
to the Ribesiaceæ; others, again, to the Passifloraceæ. Only 1 order.

  [Illustration: FIG. 368.--_A Echinocactus_: _a_ position of a
  leaf-lamina; _b_ a lateral shoot on the displaced axillary bud.
  _B_ Pereskia: _b_ a foliage-leaf on a small thorny branch which
  is subtended by a foliage-leaf which has fallen off and left a
  scar(_a_).]

  [Illustration: FIG. 369.--_Echinopsis._]

Order =Cactaceæ= (=The Cacti=). The flower is epigynous, ☿, regular,
and remarkable for its _acyclic_ structure; there are, for instance, a
large number of spirally-placed sepals and petals, which gradually pass
over into one another, and which in some species, to a certain extent,
arise from the walls of the ovary as in _Nymphæa_ (Fig. 383 _A_, _B_).
The petals are free; rotate, opening widely in _Opuntia_, _Pereskia_,
and _Rhipsalis_; erect and united at their base into a shorter or
longer tube in _Cereus_, _Epiphyllum_, _Mammillaria_, _Echinocactus_,
_Melocactus_, and others (Fig. 369). _Stamens numerous_, attached to
the base of the corolla; gynœceum formed of _many carpels_, with one
style, dividing into a number of branches corresponding to the number
of carpels; the ovary has _one loculus_ with _many parietal_ placentæ;
the ovules are anatropous, on long and curved funicles. Fruit a berry
with exendospermous seeds. The fruit-pulp is mainly derived from the
funicles.--The external appearance of the Cactaceæ is very peculiar;
_Pereskia_, which has thick and fleshy leaves (Fig. 368), deviates
the least; foliage-leaves of the usual form are wanting in the other
genera, or are usually very small, and quickly fall off and disappear
(_Opuntia_), or are modified into thorns; the stem, without normal
foliage-leaves,--so characteristic a feature in this order,--makes its
appearance after the two normally developed cotyledons. The stems
are fleshy, perennial, and may finally become woody. In some they are
elongated, globose, pointed, and more or less dichotomously branched,
_e.g._ in several of the _Rhipsalis_ species, which live mostly as
epiphytes on trees; in others, elongated, branched, globose, or, most
frequently, more or less angular (prismatic) or grooved and provided
with wings, and either columnar and erect (as much as about 20 metres
in height and 1 metre in circumference, as in _C. giganteus_ in New
Mexico) or climbing by roots (_Cereus_ and _Rhipsalis_-species);
in others again, compressed, more or less leaf-like, often with a
ridge in the centre (winged), branched and jointed: _Epiphyllum_,
_Phyllocactus_, _Opuntia_, some species of _Rhipsalis_; others are
thick, short, spherical or ovoid, unbranched or only slightly branched,
and either studded with prominent warts (_mammillæ_) each of which
supports a tuft of thorns (Fig. 368 _A_; _Mammillaria_ and others) or
with vertical ridges, separated by furrows (rows of mammillæ which
have coalesced) in _Melocactus_, _Echinocactus_, _Echinopsis_ (Fig.
369); at the same time the ovary in some is embedded in the stem so
that leaves or leaf-scars, with tufts of thorns in their axils, may be
observed on the ovary just as on the stem.--The flattened shoots of
the Cactaceæ are formed in various ways, either by the compression of
cylindrical axes (_Opuntia_) or, as in _Melocactus_, etc., from winged
stems in which all the wings are suppressed except two.

   The thorns are produced directly from the growing points of
   the axillary buds, and are modified leaves. The axillary bud
   is united at its base with its subtending leaf, which as a
   rule is extremely rudimentary; and these together form a kind
   of leaf-cushion, larger in some genera than in others. This
   leaf-cushion attains its highest development in _Mammillaria_,
   in which it is a large, conical wart (see Fig. 368 _A_), bearing
   on its apex the tuft of thorns and rudimentary lamina.--The
   _seedlings_ have normal cotyledons and a fleshy hypocotyl.

   All the species (1,000?) are American (one epiphytic species of
   _Rhipsalis_ is indigenous in S. Africa, Mauritius and Ceylon),
   especially from the tropical table-lands (Mexico, etc.). Some
   species, especially those without thorns, as _Rhipsalis_, are
   epiphytes. _Opuntia vulgaris_, the fruits of which are edible,
   is naturalized in the Mediterranean. The cochineal insect
   (_Coccus cacti_) lives on this and some closely allied species
   (_O. coccinellifera_, etc.), particularly in Mexico and the
   Canary Islands. Several are ornamental plants.


                       Family 9. =Polycarpicæ.=

The flowers _as a rule are_ ☿, _regular_ and _hypogynous_; however
in some orders they are unisexual, _e.g._ in the Myristicaceæ, or
zygomorphic (in Monkshood and Larkspur in the Ranunculaceæ); in the
Lauraceæ, (Fig. 386) for example, perigynous, and in _Nymphæa_ (Fig.
383) even partially epigynous flowers are typical.--The flowers are
acyclic in very many of the genera of the two first orders, if not
completely so, at any rate in the numerous stamens and carpels, thus
denoting an old type. It is a remarkable characteristic that in the
majority of the orders the number 3 prevails in the calyx and corolla;
the number 5 also occurs, but the number 2 is seldom met with. Most
orders have a double perianth; chorisis does not occur, suppression
is rare, and the parts of the flower are developed in acropetal
succession. The most characteristic feature in the order is the _free,
one-leaved_, as a rule _numerous carpels_ (apocarpous gynœceum). The
number of carpels in some of the last mentioned orders dwindles down
to 1 (_e.g._ the _Berberideæ_ and _Myristicaceæ_). The carpels in
_Nymphæaceæ_ become united into _one pistil_ (syncarpous), a condition
which we also find distributed among the other orders.

_Endosperm occurs in almost all_ the orders (except _e.g. Lauraceæ_).
The nutritive tissue in _Cabombeæ_ and _Nymphæeæ_ is chiefly
_perisperm_.

  [Illustration: FIG. 370.--Diagram of _Aquilegia vulgaris_: _sp_
  spur. A cyclic flower.]

  [Illustration: FIG. 371.--Diagram of a dichasium of _Ranunculus
  acer_: α_{1}, α^1, and β_{1}, β^1, bracteoles (the buds
  in the axils of the bracteoles, α and α^1, are continued
  antidromously). The flower has cyclic calyx and corolla, bub
  acyclic (8/21) stamens.]

  [Illustration: FIG. 372.--Diagram of an acyclic Ranunculaceous
  flower (only 3 stamens are indicated). The spiral of the sepals
  has a divergence of 3/5; that of the corolla and subsequent
  leaves 3/8.]

Order 1. =Ranunculaceæ.= Nearly all are _herbs_ (except _Clematis_).
The leaves are scattered (except _Clematideæ_), they have a large
sheath with broad base (no stipules), and are most frequently
palminerved with palmate lobes. The flowers are hypogynous, with most
frequently a well pronounced convex receptacle (Figs. 374 _B_, 380), ☿,
regular (except _Delphinium_ and _Aconitum_); their structure varies
very much; in some the leaves are verticillate, in others arranged
spirally; in others, again, both modes of arrangement are found. It is
a characteristic feature that the various series of leaves (especially
calyx and corolla) are not so distinct or so sharply divided as
is usual. The leaves of the perianth are free, imbricate (except
_Clematideæ_); stamens _numerous_, with most frequently extrorse
anthers; gynœceum _free_, _apocarpous_ (except _Nigella_ and partly
_Helleborus_), with 1 or several ovules (Figs. 373, 378, 379) borne on
the ventral suture. The fruit is either a nut or a follicle (_Actæa_
has berries). The seed has a _large, oil-containing_ endosperm and a
small embryo (Fig. 374).

   The main axis generally terminates in a flower, and the
   lateral axes branch in a cymose manner (Fig. 371). The flowers
   show the following differences in construction: VERTICILLATE
   (EUCYCLIC), _i.e._ constructed all through of alternating
   whorls: _Aquilegia_ (Fig. 370), _Xanthorhiza_, and sometimes
   _Eranthis_. SEMIVERTICILLATE (HEMICYCLIC) _i.e._ with sepals and
   petals in alternate whorls, and the others arranged spirally:
   _Ranunculus_ (Fig. 371), _Myosurus_, _Pæonia_ and several other
   genera entirely, or in certain species only. SPIRAL-FLOWERED
   (ACYCLIC) _i.e._ all the leaves are arranged spirally, so
   that sepals and petals do not alternate the one with the
   other, even though they are the same in number: _Adonis_ (Fig.
   372), _Aconitum_, _Delphinium_-species, _Nigella_-species,
   _Helleborus_. The leaves of the calyx are in this instance
   arranged on a spiral of 2/5; those of the corolla on 2/5,
   3/8, 5/13 or 8/21, and stamens and carpels likewise on higher
   fractions of the same series.

   The genera _Caltha_, _Anemone_, _Thalictrum_ and _Clematis_
   have a _single perianth_, which is most frequently petaloid;
   it is thus apparent that the sepals are petaloid, and the
   leaves, which in other genera have developed as petals, are in
   these instances stamens. The calyx is similarly petaloid in
   the genera _Helleborus_, _Eranthis_, _Nigella_, _Delphinium_
   and _Aconitum_; but the petals are present in these instances
   in unusual (horn-like) forms, and almost entirely given
   up to the function of nectaries, a function they already
   possess in _Ranunculus_. According to a more recent theory
   the “honey-leaves” are transformed stamens, which have lost
   the function of reproduction; the perianth is then single,
   and most frequently petaloid. [Those leaves in the flowers of
   many Ranunculaceæ which bear nectaries are termed by Prantl
   honey-leaves, and comprise those leaf-structures of the flower
   whose essential function lies in the production of nectar,
   and which, independent of the differentiation of the perianth
   into calyx and corolla, are derived from the stamens by the
   loss of their reproductive functions. Clear transitional
   forms are found between the two series of the perianth
   (_e.g._ between the sepaloid and petaloid perianth-leaves
   of _Anemone japonica_, _A. decapetala_, _Trollius_-species)
   while transitional forms are never found between perianth-and
   honey-leaves (with the exception of _Aquilegia vulgaris_, var.
   _stellata_). In _Anemone_ and _Clematis_ the honey-leaves
   pass gradually into the stamens, and agree with the stamens
   in the other Ranunculaceæ in their arrangement, development,
   and scant system of veins (except _Nigella_). In _Delphinium_,
   sect. _Consolida_, the two honey-leaves placed in front of
   the unpaired perianth-leaf are united into one, as shown by
   the veins (twice three veins arranged symmetrically). The
   honey-leaves of _Aquilegia_, _Callianthemum_, and the majority
   of the _Ranunculus_-species serve by reason of their large
   circumference, as organs of attraction, and on this account
   are considered as petals by other authors.--The same position
   in the flower which the honey-leaves assume is found occupied
   by staminodes, without nectar, in some _Coptis_-species, in
   _Anemonopsis_, _Actæa_ sect. _Euactæa_, (_e.g. A. racemosa_),
   _Clematis_ sect. _Atragene_; in the last-named they closely
   surround the stamens, in _Actæa_ they are petaloid.--A perianth,
   sharply differentiated into calyx and corolla, and destitute of
   honey-leaves, is found in _Anemone_, sect. _Knowltonia_ (Cape),

   _Adonis_, _Pæonia_.--The perianth of the Ranunculaceæ is
   considered by Prantl to be usually petaloid.--The nectaries
   arise in the Ranunculaceæ (1) on normal stamens (_Clematis_
   sect. _Viorna_), (2) on the honey-leaves (this is generally the
   case), and (3) on the carpels (_Caltha_ and the majority of
   _Trollius_-species).--As the result of his researches upon the
   Ranunculaceæ, Prantl does not agree with the view advanced by
   Drude (Schenk, _Hand. d. Bot._ iii.) that the petals in general
   have proceeded from the metamorphosis of the stamens (_K_)].

  [Illustration: FIG. 373.--Ovaries in longitudinal section: _v_
  the ventral suture; _d_ the dorsal suture: _A_, _B Clematis_;
  _C Ranunculus_; _D Myosurus_.]

   The most primitive form of fruit is undoubtedly the pod formed
   by one carpel, on the edges of which (along the ventral suture)
   two rows of ovules are situated: Pæonieæ, Helleboreæ, Delphinieæ
   (Fig. 379). In a great many genera the number of ovules has been
   limited to _one_ perfect one, which is placed in the central
   plane under the united leaf-edges, and sometimes also some
   barren ovules above it (Fig. 373). The fruitlets in this case
   become achenes, and are present in much larger numbers than when
   there are follicles.

  [Illustration: FIG. 374.--_Helleborus niger_: _A_ flower; _B_
  receptacle; _pet_ petals (honey-leaves); _pi_ stamens and
  carpels; _C_ seed; _D_ anther (cross section); _alb_ endosperm.]

  [Illustration: FIG. 375.--_Caltha palustris_: fruit.]

The following have FOLLICLES: _Pæonieæ_, _Helleboreæ_ (except _Actæa_)
and _Delphinieæ_; ACHENES: _Ranunculeæ_, _Anemoneæ_ and _Clematideæ_.

=A. Follicles= (Figs. 375, 379), with many ovules, situated in two rows
along the ventral suture. ~_Actæa_ has berries, _Nigella_ has capsules
of several loculi.~

=1.= PÆONIEÆ, PEONY GROUP. This has regular, acyclic flowers with a
normal, most frequently 5-leaved, imbricate calyx; large, coloured
petals, and introrse anthers. Slightly perigynous. Surrounding the
base of the carpels a ring-like swelling of the receptacle (“disc”) is
present, which is largest in _P. moutan_. The follicles are more or
less fleshy or leathery. Mostly herbs, with pinnatisect or decompound
leaves and large, solitary flowers; a gradual transition may be traced
from the foliage-leaves to the petals. _Pæonia; Hydrastis._

  [Illustration: FIG. 376.--_Aquilegia vulgaris._]

  [Illustration: FIG. 377.--_Caltha palustris_ (nat. size).]

  [Illustration: FIG. 378.--_Nigella_: _A_, _B_ fruit of _N.
  damascena_, entire, and cut transversely. _C_ Petal (honey-leaf)
  of _N. arvensis_. _D_ Petal of _N. damascena_.]

=2.= HELLEBOREÆ, HELLEBORE GROUP. This has regular flowers with most
frequently a coloured calyx. The petals (honey-leaves) are modified
into nectaries; they may be horn-like, provided with a spur, or of a
similarly unusual form, or they may be entirely absent. Anthers often
extrorse.--_Trollius_ (Globe-flower[36]). The flower is acyclic: many
petaloid sepals, succeeding these, most frequently, several _linear_,
dark yellow petals, which bear a naked nectary at the base; finally,
many stamens and carpels arranged in a spiral (3/8, 8/21).--_Caltha_
(Marsh-marigold, Figs. 375, 377); 5 (-7) yellow sepals, no petals.
The foliage-leaves have a large amplexicaul sheath.--_Helleborous_
(Hellebore) has pedate leaves. The flower is acyclic, with 5 large,
regular, _persistent_, often petaloid sepals (2/5); small, _horn-like_
petals (honey-leaves; most frequently 13, divergence 8/13) and
generally few carpels (Fig. 374).--_Coptis._--_Isopyrum._--_Eranthis_
(Winter Aconite), like _Anemone_, has a 3-leaved involucre and most
frequently trimerous flowers, ~6 large petaloid sepals, 6 petals
(tubular honey-leaves), 6 oblique rows of stamens, 3–6 carpels~.
_Aquilegia_ (Columbine, Fig. 376); the flower is entirely cyclic and
has large spurs on all the 5 petals (funnel-shaped honey-leaves); S5
coloured, P5, A5 × (8–12), G5 in regular alternation (Figs. 376, 370);
the innermost stamens are often staminodes (Fig. 370).--_Nigella_
(Love-in-the-mist, Fig. 378) has 5 sepals and 8 small, _two-lipped_
petals cleft at the apex (the nectary is covered by the under-lip;
Fig. 378 _C_, _D_). The 5 carpels are more or less completely united;
and a many-carpellate ovary with free styles is formed in some. Large
air-chambers in the external wall of the ovary are formed in _N.
damascena_ (Fig. 378).--_Actæa_ (Baneberry) has coloured sepals, either
no petals or an indefinite number, and only 1 carpel. The fruit is a
berry (or follicle).--~_Cimicifuga_, _Garidella_, _Xanthorhiza_ (S5,
P5, A5 + 5, G5).~


=3.= DELPHINIEÆ, LARKSPUR GROUP. Zygomorphic flowers with coloured
calyx; the 2 posterior petals (honey-leaves) are transformed into
nectaries, the others are small or absent altogether.--_Aconitum_
(Monkshood); 5 sepals, of which the _posterior one_ (Fig. 379 _A_)
_is helmet-shaped_; most frequently 8 petals (as in Fig. 372), of
which the two posterior ones (honey-leaves) are developed into
long-clawed nectaries (Fig. 379 _A_, _k_) enveloped by the helmet-like
sepal; the others are small, or are to some extent suppressed.
~Stamens on a spiral of 3/8–5/13; generally 3 carpels.~ Perennial
herbs.--_Delphinium_ (Larkspur); very closely allied to _Aconitum_, but
the anterior 4 petals are most frequently wanting, and the 2 posterior
ones have each a spur, which is enclosed by the _posterior sepal_,
the latter being also provided with _a membranous spur_. ~Stamens and
carpels arranged on a spiral of 3/8, 5/13, 8/21. In _D. ajacis_ and
_consolida_ there is apparently only 1 petal (by the fusion of 4) and 1
carpel.~

  [Illustration: FIG. 379.--_Aconitum napellus. A_ Flower in
  longitudinal section, below are the 2 bracteoles; _a_ half
  of helmet-like sepal; _b_ and _c_ other sepals; _k_ nectary;
  _f_ carpels. _B_ Ovary in longitudinal section; _C_ the same
  transversely; _d_ dorsal suture; _v_ ventral suture.]

=B. Fruit achenes.= Many carpels, each with only 1 ascending (Fig.
373 _C_), or pendulous (Fig. 373 _D_), perfect ovule; often also
rudimentary ovules above it (Fig. 373 _A_, _B_). Fruit achenes.

=4.= RANUNCULEÆ, BUTTERCUP GROUP, has double perianth. _Myosurus_
and _Adonis_ have pendulous ovules as in Anemoneæ (Fig. 373 _D_);
~_Ranunculus_, with _Batrachium_ and _Ficaria_, erect ovules (Fig. 373
_C_) and downwardly-turned radicle.~--_Ranunculus._ Most frequently
S5, P5, many spirally-placed stamens and carpels (Figs. 371, 380). The
petals (honey-leaves) have a nectary at the base, covered by a small
scale. ~_Batrachium_, Water Ranunculus, deviates by the achenes being
transversely wrinkled; dimorphic leaves. _Ficaria_ has 3 sepals and 7–8
petals arranged in 2/5–3/8. _F. ranunculoides_ (the only species) has
tuberous roots, which spring from the base of the axillary buds, and
together with these, serve as organs of reproduction. The embryo has
only 1 cotyledon.~--_Myosurus_ (Mouse-tail) has small prolongations
from the 5 sepals; 5 narrow petals which bear the nectaries near the
apex; sometimes only 5 stamens, and an ultimately very long receptacle,
with numerous spirally-arranged achenes (Fig. 381).--_Adonis_ is
acyclic (Fig. 372); most frequently 5 sepals with a divergence of 2/5,
8 petals of 3/8, indefinite stamens and carpels of 3/8 or 5/13. The
corolla has no nectary.

  [Illustration: FIG. 380.--Flower of _Ranunculus sceleratus_ in
  longitudinal section.]

  [Illustration: FIG. 381.--_Myosurus minimus_: _c_ cotyledons; _m_
  the foliage-leaves; _f_ the floral axis with the carpels, and _g_
  the same without; _y_ insertion of perianth.]

=5.= ANEMONEÆ, ANEMONE GROUP, has a single perianth. ~(Pendulous ovules
(Fig. 373 _D_), radicle turned upward).~--_Anemone_ has a single,
petaloid, most frequently 5–6-leaved perianth, and beneath the flower
most frequently _an involucre of 3 leaves_, placed close together in
the form of a whorl. In _A. nemorosa_, _ranunculoides_, etc., the
involucral leaves resemble foliage-leaves; in _A. hepatica_ they are
situated close under the perianth, and resemble sepals, and in the
sub-genus _Pulsatilla_ they stand between the foliage-leaves and
floral-leaves. The style of _Pulsatilla_ finally grows out in the form
of a feather. ~The main axis of _A. hepatica_ has unlimited growth (it
is biaxial), and the flowers are borne laterally in the axils of the
scale-leaves; in the others (uniaxial) the flower is terminal, and the
rhizome becomes a sympodium after the first flowering.~--_Thalictrum_
(Meadow Rue) has no involucre; 4–5-leaved, greenish perianth. The
receptacle is flat. ~The stamens are brightly-coloured and have long
filaments; 1–5 accessory flowers may occur in the leaf-axils of the
panicle-like inflorescence.~

=6.= CLEMATIDEÆ, CLEMATIS GROUP. This differs from all the others
in the _valvate æstivation_ of the calyx and its opposite leaves.
There are 4 (-several) petaloid sepals; petals are absent, or linear
(_Atragene_). Ovule 1, pendulous. Achenes, often with prolonged,
feathery style. The majority of the genera are shrubs, and climb by
their sensitive, twining leaf-stalks.--_Clematis; Atragene._

   POLLINATION. The flowers are conspicuous either by coloured
   petals (honey-leaves) (_Ranunculus_, _Pæonia_) or coloured
   sepals (_Helleborus_, _Anemone_, _Caltha_, etc.), or by both
   (_Aquilegia_, _Delphinium_), or by the coloured stamens
   (_Thalictrum_). Some have no honey (_Clematis_, _Anemone_,
   _Thalictrum_), and are generally visited by insects for
   the sake of their pollen. Others have nectaries on the
   corolla (_Ranunculus_, _Trollius_, _Helleborus_, _Nigella_,
   _Aconitum_, etc.), more rarely on the stamens (_Pulsatilla_,
   _Clematis_-species), or the carpels (_Caltha_), or the calyx
   (certain species of _Pæonia_). The honey is readily accessible
   in the flat, open flowers, and these flowers also may easily
   pollinate themselves. There is marked protandry where the
   honey lies deeply hidden, as in _Aquilegia_, _Delphinium_, and
   _Aconitum_. _Helleborus_ and some _Ranunculus_-species are
   protogynous.

   About 680 species; especially in northern temperate climates,
   and extending to the Polar and Alpine regions. Only the
   _Clematideæ_ are tropical.

   The order has an abundance of _acrid_, vesicant properties
   (_R. acer_, _sceleratus_, etc.), and _poisonous_ alkaloids
   (_Helleborus niger_ is poisonous). OFFICINAL: _Aconitum
   napellus_ (aconitine; leaves and tuberous roots); the rhizome of
   _Hydrastis canadensis_ from N. Am. (the alkaloid hydrastine).
   The order, however, is best known for its ornamental plants;
   almost all the genera have species which are cultivated for
   their beauty. Sweet-scented flowers are absent.

Order 2. =Nymphæaceæ (Water Lilies).= WATER PLANTS; generally with
large, floating leaves, and large solitary flowers; sepals 3–5, petals
3–∞, stamens 6–∞, carpels 3–∞. The flower is hypogynous, but in the
_Nymphæeæ_ different degrees of epigyny are found, and from this fact,
as well as from the carpels being united into one pistil, the family
forms a lateral offshoot from the Ranunculaceæ, with much greater
modification. The seed often has an aril, and, in the majority, a
farinaceous nutritive tissue, partly endosperm, partly perisperm (Fig.
383 _C_). The embryo has 2 thick cotyledons and a small hypocotyl; the
plumule is well developed, with 2–4 leaves.

   1. CABOMBEÆ. 3–4 species (Tropical S. Am.), resembling the
   Water Ranunculus, with two kinds of leaves, the submerged being
   dissected and the aerial peltate. The flowers are eucyclic,
   trimerous, with 2–3 free, epigynous carpels. The ovules are
   situated _on the central line_ of the carpel--an almost unique
   circumstance. Endosperm and perisperm. _Cabomba; Brasenia._

2. NELUMBONEÆ. The leaves are _peltate_, raised on long stalks high
above the water. Large, _hypogynous_ flowers (Fig. 382); sepals 4–5;
petals numerous; stamens numerous; _carpels several_, _distinct_. The
receptacle is very remarkable, being raised above the stamens, and
developed into an _inverted conical_ body on the apex of which the
nut-like fruits are _embedded in pits_. _Endosperm is wanting_, but
the embryo is large and has well developed cotyledons.--~_Nelumbo_,
2 species. _N. lutea_ (N. Am.); _N. speciosa_ (E. Ind.) was sacred
amongst the ancient Hindoos and Egyptians, (the Lotus flower); its
seeds are used as food.~

3. NYMPHÆEÆ, WATER LILY GROUP. The carpels are united into _one_,
_many-locular ovary_, _whose numerous ovules are situated on the
surface of the partition walls_ (as in the Poppies); the stigma is
sessile and radiating, the number of rays corresponding to the number
of carpels (Fig. 383). The fruit is a spongy _berry_ with many seeds,
which have a large perisperm in addition to the endosperm (Fig. 383
_C_).

  [Illustration: FIG. 382.--_Nelumbo nucifera_: vertical section
  through the receptacle.]

Sepals, petals, and stamens often pass gradually over the one into the
other, the petals becoming narrower by degrees, and bearing anthers
on each side of the apex, which gradually become larger anthers in
proportion to the filament, until the perfect stamen is developed.
The long-stalked leaves are floating, and most frequently cordate,
elliptical, leathery, with a shiny surface, sometimes (as in _Victoria
regia_ and _Euryale ferox_) with strongly projecting thorny ribs on the
lower surface. In the intercellular passages of the leaves are some
peculiar, stellate cells.

_Nuphar_ has 5 sepals, and an _hypogynous_ flower. ~The petals, which
are small, have a nectary on the back; the coloured inner side of the
sepals functions as petals; the ovate gynœceum is quite free.--_N.
luteum_ is a native plant (Yellow Water-Lily), with, most frequently,
13 petals and 10–16 loculi in the ovary. The rhizome is horizontal, as
much as 5–6 cm. in thickness, and bears on its under surface a number
of roots, which on dying-off leave deep scars; the leaves are borne in
spiral lines, and the flowers are solitary in certain leaf-axils. The
construction of the rhizome is very peculiar; the vascular bundles are
scattered and closed as in a monocotyledonous stem.~

  [Illustration: FIG. 383.--_Nymphæa_: _A_ flower in longitudinal
  section, the most external leaves being removed; _B_ fruit; _C_
  seed of _Nuphar_ (longitudinal section); the perisperm at the
  base, the endosperm at the top surrounding the embryo.]

_Nymphæa_ has 4 sepals, and the flower is more or less _epigynous_.
Petals and stamens are inserted at different heights on the ovary to
just beneath the stigma (Fig. 383). _Nymphæa alba_ (White Water-Lily).
_Victoria regia_ from the Amazon, and _Euryale ferox_ from Asia, have
entirely epigynous flowers. ~The shield-like leaves of _Victoria_ are
as much as 2 metres in diameter, and the edge is bent up to a height
of 5–14 cm.; the flowers are 20–40 cm. in diameter, and change in
twenty-four hours from white to rose-red. A development of heat, as
much as 14°C. above the temperature of the air, together with a strong
formation of carbonic acid, has been observed during flowering.~

   POLLINATION. _Nymphæa alba_ and other species of the
   sub-genus _Symphytopleura_ are self-pollinated; the sub-genus
   _Leptopleura_ is insect-pollinated. _Nuphar_ and _Victoria_ can
   effect self-fertilisation; _Euryale_ is self-fertilised, often
   in entirely closed and submerged flowers.--The dissemination
   of the seeds in _Nuphar luteum_ is effected by the fruit,
   which rests on the water, becoming detached from its stalk,
   and dehiscing from the base upwards so that the seeds are
   set free; while in _Nymphæa alba_ the spirally-twisted stalk
   draws the fruit under water, and it dehisces by its upper part
   being thrown off as a hood, and the seeds which are enclosed
   in air-tight sacs rise to the surface of the water. In this
   condition they are able to float and can only sink to the bottom
   when the air has disappeared.

   53 species; in fresh water in all parts of the world, but
   especially in the Tropics.--The rhizomes and seeds of some may
   be used as food; _Euryale ferox_ is even cultivated. _Nymphæa
   cœrulea_ and _Lotus_ were sacred among the Egyptians.

Order 3. =Ceratophyllaceæ.= About 3 species. Aquatic plants, submerged,
rootless; leaves cartilaginous, verticillate, dissected into repeatedly
dichotomous branches which are finely toothed; only one of the leaves
in a whorl supports a vegetative branch. The flowers are _monœcious_,
axillary. Inside the 6–12 perianth-leaves are situated in the ♂-flower
10–20 stamens with thick connective, and in the ♀-flower a gynœceum
formed by one carpel, with one orthotropous and pendulous ovule, which
has only one integument. Fruit a nut, which, in some species, bears on
each side a pointed horn, and at the apex a similar one, formed by the
persistent style.--The embryo has an unusually well developed plumule
with several whorls of leaves. The plant is rootless throughout its
whole life.--_Ceratophyllum_ (Horn-wort).

   Order 4. =Annonaceæ.= Sepals 3; petals 3+3 (most frequently
   _valvate_); succeeding these (as in the _Ranunculaceæ_) are
   _numerous acyclic_ stamens and an _apocarpous gynœceum_; the
   flowers are hypogynous, regular and ☿, generally very large
   (2–3 cm. in diameter), and the leaves of the perianth are
   more or less fleshy or leathery. The majority have syncarps
   with berry-like fruitlets, but in _Annona_ and some others
   the carpels fuse together into a large, head-like fruit--a
   kind of composite berry. The seeds have _ruminate_ endosperm
   as in _Myristica_.--Trees or shrubs with _alternate_, simple,
   entire, penninerved leaves without stipules. 450 (700?) species;
   especially tropical. The best known are _Anona cherimolia_,
   _squamosa_ and _reticulata_ (all from America) cultivated on
   account of their large, delicious fruits. Some have acrid and
   aromatic properties (_Xylopia_, _Cananga_--the flowers of the
   latter yield Ylang-ylang); _Artabotrys odoratissimus_; _Asimina_
   (N. Am.).

   Order 5. =Magnoliaceæ.= Trees or shrubs with scattered, often
   leathery, entire leaves, generally with _stipules_, which (as in
   _Ficus_) are rolled together and form a hood round the younger
   internodes above them, and are cast off by the unfolding of
   the next leaf, leaving a ring-like scar. The endosperm is _not
   ruminate_. Corolla imbricate. Fruit a syncarp.

   =A.= MAGNOLIEÆ. The flowers are borne singly, and before opening
   are enveloped in an ochrea-like spathe which corresponds to
   the stipules of the foliage-leaves. The perianth generally
   consists of 3 trimerous whorls, the external one of which
   is sometimes sepaloid (_Liriodendron_, and the majority of
   _Magnolia_species), sometimes coloured like the others; the
   perianth is sometimes many-seriate. _Numerous spirally-placed_
   stamens and carpels. The latter are situated on the _elongated_,
   cylindrical receptacle, and are individually more or less
   united, except in _Liriodendron_, where they are free. This last
   genus has winged achenes; the fruitlets in _Magnolia_ open along
   the dorsal and ventral sutures, and the seeds then hang out,
   suspended by elastic threads formed from the vascular bundles
   of the funicle and raphe; they are red and drupaceous, the
   external layer of the shell being fleshy--a very rare occurrence.

   =B.= ILLICIEÆ has no stipules. The carpels are situated in a
   whorl on a short receptacle. Follicles, one-seeded. The leaves
   are dotted by glands containing essential oil. _Illicium;
   Drimys._

   70 species; in tropical or temperate climates; none in Europe
   or Africa. They are chiefly used as ornamental plants, _e.g._
   the Tulip-tree (_Liriodendron tulipifera_, N. Am.), _Magnolia
   grandiflora_ (N. Am.), _M. yulan_ and _fuscata_ (China), and
   others. The remains of _Liriodendron_ occur as fossils in the
   Cretaceous and Tertiary periods.--The fruits of _Illicium
   anisatum_ (Star-aniseed from Eastern Asia) are OFFICINAL. The
   bark of _Drimys winteri_ (S. Am.) is also strongly aromatic.

   Order 6. =Calycanthaceæ.= These are very closely related to
   the Magnoliaceæ, but differ in having _perigynous_ flowers
   with many perianth-leaves, stamens and (about 20) carpels in a
   continuous _spiral_, seeds _almost devoid of endosperm_ with
   rolled up, leaf-like cotyledons, and leaves opposite on a square
   stem.--There are some species in N. America (_Calycanthus
   florida_, _occidentalis_, etc.) and 1 in Japan (_Chimonanthus
   præcox_), all strongly aromatic.

   Order 7. =Monimiaceæ.= Aromatic shrubs with opposite leaves.
   Perigynous flowers. The anthers dehisce by valves like those of
   the _Lauraceæ_, and the Monimiaceæ may thus be considered as an
   apocarpous form of this order. They are also closely related to
   _Calycanthaceæ_. 150 species, tropical.--_Hedycarya, Mollinedia,
   Monimia._

  [Illustration: FIG. 384.--Diagram of _Berberis_.]

  [Illustration: FIG. 385.--_Berberis_: carpel with 2 stamens.]

Order 8. =Berberidaceæ (Barberries).=--The regular, ☿, hypogynous
flowers are dimerous or trimerous and have regularly alternating
whorls of free sepals, petals, and stamens and 1 unilocular carpel;
the corolla and stamens have each 2 whorls, the calyx at least 2. The
anthers open, as in Lauraceæ, by (2) _valves_, but are always introrse
(Fig. 384). The pistil has a large, disc-like, almost _sessile_ stigma
(Fig. 385), and in the ovary _several_ erect ovules are placed close to
the base of the ventral suture. The fruit is most frequently a _berry_.
Seeds endospermous.--Shrubs or herbs with scattered, most frequently
compound leaves (without stipules), and racemose inflorescences.--~They
show a relationship to the Lauraceæ in the number of the parts of the
flower and the dehiscence of the anthers.~

_Berberis_ is a shrub; it has sepals 3 + 3, petals 3 + 3, stamens 3
+ 3 (Fig. 384). The petals (honey-leaves) bear internally at the base
2 darkish-yellow nectaries. The filaments are sensitive at the base,
and suddenly bend inwards if touched at that spot (Fig. 385). ~The
racemes often have a terminal, 5-merous flower; they are borne on
dwarf-branches. The leaves on the long-branches develope into thorns,
but the buds in their axils, in the same year as themselves, develope
as the short-branches with simple foliage-leaves, _articulated_ at
the base, from which fact some authorities have considered that the
leaf is compound with a single, terminal leaflet.~--_Mahonia_ has
imparipinnate leaves. The flower has 3 whorls of sepals. Otherwise as
in _Berberis_.--~_Epimedium_; herbs with spurred petals; the flowers
dimerous; 4–5 whorls of sepals, 2 of petals and stamens. Fruit a
capsule. _Leontice_, fruit dry. The anthers of _Podophyllum_ dehisce
longitudinally.--_Nandina. Aceranthus._~

   100 species; North temp., especially Asia: fossils in Tertiary.
   _Berberis vulgaris_ is a native of Europe. This and other
   species, together with _Mahonia aquifolium_ (N. Am.), _Epimedium
   alpinum_, etc., are cultivated as ornamental plants. Several
   have a yellow colouring matter in the root and stem. OFFICINAL:
   the rhizome of _Podophyllum peltatum_ (from N. Am.) yields
   podophyllin.

   Order 9. =Menispermaceæ.= This order has derived its name from
   the more or less crescent-like fruits and seeds. Diœcious.
   The flowers are 2–3-merous, most frequently as in _Berberis_
   (S3 + 3, P3 + 3, A3 + 3), with the difference that there are
   3 _free carpels_, each with 1 ovule; in some genera, however,
   the number is different. Stamens often united into a bundle
   (as in _Myristica_); anthers dehiscing longitudinally; fruit a
   drupe.--The plants (with herbaceous or woody stems) belonging
   to this order are nearly all _twining_ or _climbing_ plants,
   and have scattered, palmate or peltate, sometimes lobed leaves
   without stipules. Structure of stem anomalous. _Cocculus,
   Menispermum, Cissampelos, Anamirta._

   150 species; Tropical; very rich in bitter and poisonous
   properties. OFFICINAL: Calumba-root from _Jateorhiza columba_
   (E. Africa). The following are cultivated as ornamental
   plants:--_Menispermum canadense_ (N. Am.) and _M. dahuricum_
   (Asia). The fruits of _Anamirta cocculus_ (E. Ind.) are very
   poisonous (“Grains-of-Paradise”; the poisonous matter is
   picrotoxine).

   Order 10. =Lardizabalaceæ.= This order, by the free, apocarpous
   carpels, belongs to a more primitive type, and by the united
   stamens to a more developed one. _Akebia_; _Holbœllia_;
   principally climbing or twining shrubs. About 7 species in S.E.
   Asia and S. Am.

Order 11. =Lauraceæ= (=True Laurels=). Trees or shrubs; the leaves,
always without stipules, are simple, most frequently scattered,
lanceolate or elliptical, entire, penninerved, finely reticulate
(except _Cinnamomum_ with 3–5-veined leaf), leathery and evergreen
(except, _e.g. Cinnamomum_); they are frequently studded with clear
glands containing _volatile oil_. The flowers are borne in panicles
and are small and of a greenish or whitish colour. They are _regular,
perigynous_, with most frequently a bowl or cup-shaped receptacle
(Fig. 386), usually ☿, and _trimerous_ (rarely dimerous) through all
(most frequently 6–7) whorls; viz. most frequently, perianth 2 whorls,
stamens 3–4 and carpels 1 (P3 + 3, A3 + 3 + 3 + 3, G3) in regular
alternation (Fig. 387). Each of the 2 or 4 loculi of the anthers _open
by an upwardly directed valve_ (Fig. 386); of the stamens, the 2
outermost whorls are generally introrse, the others extrorse, or 1–3
whorls are developed as staminodes (Fig. 387 _g_). The gynœceum has
1 loculus with 1 style and 1 pendulous ovule (Fig. 386), and may be
considered as formed of 3 carpels. The fruit is a _berry_ (Fig. 388)
or _drupe_, which often is surrounded at its base by the persistent
receptacle (as an acorn by its cupule), which becomes fleshy and
sometimes coloured during the ripening of the fruit. The embryo has 2
thick cotyledons, but _no endosperm_ (Fig. 388).

  [Illustration: FIG. 386.--Flower of the Cinnamon-tree
  (_Cinnamomum zeylanicum_) (longitudinal section).]

  [Illustration: FIG. 387.--Typical diagram of the Lauraceæ: _g_
  staminodes.]

  [Illustration: FIG. 388.--_Laurus nobilis_: longitudinal section
  of fruit.]

   The Lauraceæ present affinities with the Polygonaceæ, in
   which there is found perigyny, as well as a similar number of
   parts in the flower and a similar gynœceum, but with erect
   and orthotropous ovule. From their general characters they
   should be classed among the Polycarpicæ, but stand, however,
   isolated by the _syncarpous_ gynœceum, if it is in reality
   formed by 3 carpels and not by 1 only. _Hernandia_, which has
   epigynous monœcious flowers, deviates most.--_Cassytha_ is
   a _Cuscuta_-like, herbaceous, slightly green parasite with
   twining, almost leafless stems. The flower however agrees with
   the diagram in Fig. 387. Some Lauraceæ have curved veins or
   palminerved and lobed leaves (often together with entire ones)
   _e.g. Sassafras_.

  [Illustration: FIG. 389.--_Myristica_: fruit.]

  [Illustration: FIG. 390.--Seed with aril entire and in
  longitudinal section.]

   There are 1000 species; especially in the forests of tropical
   S. America and Asia, of which they form the principal part.
   Only _Laurus nobilis_ is found in Europe, and there is little
   doubt that its proper home is in Western Asia. They are
   rare in Africa.--On account of _the volatile oil_ found in
   all parts of the plant, they are used as _spices_, _e.g._
   the false Cinnamon-tree (_Dicypellium caryophyllatum_, in
   the Brazils). The OFFICINAL ones are--the Cinnamon-tree
   (_Cinnamomum zeylanicum_ from Ceylon, E. India, Eastern Asia),
   which is also cultivated; the Camphor-tree (_Cinnamomum
   camphora_, Eastern Asia). The Laurel-tree (_Laurus nobilis_,
   Mediterranean), the berries and leaves of which give laurel oil,
   is medicinal.--Scented wood for furniture, etc., is obtained
   from _Sassafras officinalis_ (from N. Am.). The wood from its
   roots is officinal. Pichurim “beans” are the large cotyledons
   of _Nectandra pichury_, whilst the famous “Greenheart” wood
   of Demarara is the wood of _Nectandra rodiæi_. The pulp and
   seeds contain a _fatty oil_. The pear-like fruit of _Persea
   gratissima_ (Mexico, also cultivated) is very delicious.
   _Lindera benzoin_ is a garden shrub; _Laurus nobilis_ likewise.

   Order 12. =Myristicaceæ= (=Nutmegs=). In this order there is
   only 1 genus, _Myristica_. Trees or shrubs. The leaves agree
   closely with those of the Lauraceæ, with which this order has
   many points in common. The majority of the species are aromatic,
   having in their vegetative parts pellucid glands with volatile
   oils. The flowers are regular, diœcious, trimerous, and have a
   single gamophyllous (cupular or campanulate) 3-toothed, fleshy
   perianth. In the ♂-flowers the anthers vary in number (3–15),
   and they are extrorse and borne on a centrally-placed column;
   in the ♀-flower the gynœceum is unilocular, unicarpellary, with
   1 ovule. The FRUIT (Fig. 389) has the form of a pear; it is a
   fleshy, yellow capsule, which opens along the ventral and dorsal
   sutures, exposing the large seed. This seed has a large, red,
   irregularly branched aril--the so-called “mace”; the “nutmeg,”
   on the other hand, is the seed itself with the inner thin
   portion of the testa, which has pushed its way irregularly into
   the endosperm, and causes the marbled appearance of the cut seed
   (Fig. 390); the external, dark brown, hard, and brittle part
   of the seed-shell is however removed. Mace and nutmeg contain
   volatile and fatty oils in abundance.--80 species. Tropical. The
   majority are used on account of their aromatic seeds and aril,
   the most important being _M. fragrans_ (_moschata_), from the
   Moluccas. This is cultivated in special plantations, not only in
   its native home, but in other tropical countries also. Nutmegs
   were known as commodities in Europe in very ancient times
   (_e.g._ by the Romans), but it was not until the year 1500 that
   the tree itself was known. The seed is OFFICINAL.


                        Family 10. =Rhœadinæ.=

The plants belonging to this family are almost exclusively herbaceous,
with scattered, exstipulate leaves. The flowers are eucyclic di- or
tetramerous, with the calyx and corolla deciduous, _hypogynous_,
☿, _regular_, the gynœceum with 2–several carpels (generally 2,
transversely placed) (Figs. 391, 392, 393, 397). The ovary is
_unilocular with parietal placentæ_, but in _Cruciferæ_ and a few
others it becomes bilocular by the development of a _false_, membranous
wall between the placentæ. The stigmas in the majority of cases
are _commissural_, _i.e._ they stand above the placentæ, and not
above the dorsal line of the carpels. The fruit is nearly always a
_capsule_, which opens by the middle portions of the carpels detaching
themselves as valves, bearing no seed, whilst the placentæ persist
as the seed-bearing frame. Endosperm is found in _Papaveraceæ_ and
_Fumariaceæ_, but is absent in _Cruciferæ_ and _Capparidaceæ_.--~This
family through the Papaveraceæ is related to the Polycarpicæ (the
Nymphæaceæ), through the Capparidaceæ to the Resedaceæ in the next
family.~

   Exceptions to the above are: _Eschscholtzia_, _Subularia_ (Fig.
   403) and a few Capparidaceæ, in which perigynous flowers are
   found. A few Papaveraceæ and Fumariaceæ have trimerous flowers.
   In _Fumaria_ and certain Cruciferæ, the fruit is a nut. The
   Fumariaceæ have zygomorphic flowers. Trees and shrubs are almost
   entirely confined to the Capparidaceæ, in which order stipules
   also are found.

Order 1. =Papaveraceæ= (=Poppies=). Herbaceous plants with stiff hairs
and _latex_; flowers _regular_ (Fig. 391) with generally 2 (-3) sepals
(which _fall off_ as the flower opens), 2 + 2 petals (imbricate
and crumpled in the bud) _without spur, numerous stamens in several
alternating whorls_ (generally a multiple of 2); carpels 2–several,
united into a unilocular gynœceum. Trimerous flowers also occur.
Capsule with very numerous seeds on the parietal placentæ; embryo
small, with large, oleaginous _endosperm_ (Fig. 392).--The leaves have
no stipules and are generally pinnately lobed.

  [Illustration: FIG. 391.--A Diagram of the flower of _Glaucium_
  and the dichasium (which becomes transformed into a scorpioid
  cyme). _B Papaver argemone_, transverse section of the ovary
  with indication of the position of the stigmas.]

  [Illustration: FIG. 392.--_Papaver somniferum_: _A_ capsule;
  _st_ the stigma; _v_ valves; _h_ pores; _B_ seed in longitudinal
  section; _alb_ endosperm; _emb_ embryo.]

_Papaver_ (Poppy) has large, solitary, terminal flowers; petals firmly
and irregularly folded in æstivation; gynœceum formed by many (4–15)
carpels; stigmas velvety, _sessile_ and _stellate_ (the rays stand
above the placentæ) (Fig. 391 _B_). The edges of the carpels project
deeply into the ovary, but do not meet in the centre, so that it
remains unilocular. The capsule opens by pores placed close beneath
the stigma, and formed of small valves alternating with the placentæ
and the rays of the stigma (Fig. 391). _P. dubium_, _P. argemone_, _P.
rhœas_.--_Chelidonium_ (Greater Celandine) has _yellow_ latex, flowers
in umbellate cymes (the terminal, central flower opening first) and
only 2 carpels; the fruit resembles the siliqua of the Cruciferæ in
having two _barren valves_, which are detached from the base upwards,
and a _seed-bearing frame_, but there is no partition wall formed
between the placentæ. _Ch. majus._--~The majority of the other genera
have, like _Chelidonium_, 2 carpels (lateral and alternating with the
sepals: Fig. 391 _A_) and siliqua-like fruit, thus: _Eschscholtzia_
(perigynous) with a linear, stigma-bearing prolongation extending as
far above the placentæ as above the dorsal suture of the carpels;
_Glaucium_ (Horn-Poppy); _G. luteum_, whose extremely long, thin
capsule differs from that of _Chelidonium_ by the formation, during
ripening, of a thick, spongy (_false_) replum, which persists when
the valves are detached; _Sanguinaria_ with red latex, the 2 petals
divided into 8–12 small petals (perhaps by dédoublement); _Macleya_ and
_Bocconia_ (1-seeded capsule) with 2 sepals and no petals.--Trimerous
flowers are found in _Argemone_ and _Platystemon_ (with a curious
fruit, carpels free, and transversely divided and constricted into
joints which separate as nut-like portions).--_Meconopsis._--_Hypecoum_
(Fig. 393 _C_) has tri-lobed and three cleft petals, 4 free stamens
with 4-locular anthers and a jointed siliqua; it presents a
transitional form to the Fumariaceæ, with which order it is sometimes
included.~

   POLLINATION. _Papaver_ and _Chelidonium_ have no honey, and
   are without doubt only visited by insects for the sake of
   the pollen. The anthers and stigmas mature about the same
   time.--There are 80 species; especially from warm climates.
   OFFICINAL: _Papaver somniferum_ (Opium-Poppy); the latex
   of its unripe capsules is obtained by incisions, and dried
   (_opium_); it contains many alkaloids: morphine, papaverine,
   narcotine, thebaine, etc. The oleaginous seeds are also used
   in the manufacture of oil. Its home is in the East, where it
   is extensively cultivated. The petals of the Corn-poppy (_P.
   rhœas_) are also officinal. Several species are cultivated as
   ornamental plants.

Order 2. =Fumariacæ= (=Fumitories=). This order differs from the
closely allied Papaveraceæ in the absence of latex, a poorer flower,
generally _transversely zygomorphic_ (Fig. 393 _B_), in which case one
or both of the outer lateral petals are gibbous, or prolonged into
a spur; the stamens are especially anomalous. Sepals =2=, caducous;
petals 2 + 2; stamens 2, _tripartite_; each lateral anther is
_bilocular_ (Figs. 393 _A_, _B_; 395); gynœceum bicarpellate. The fruit
is a nut or siliqua-like capsule. _Endosperm._--_Herbs_ with scattered,
repeatedly pinnately-divided leaves without stipules, generally quite
glabrous and glaucous; the flowers are arranged in racemes with
subtending bracts, but the bracteoles are sometimes suppressed.

_Dicentra_ (syn. _Dielytra_) and _Adlumia_ have a doubly symmetrical
flower, with a spur or gibbous swelling at the base of _each_ of
the laterally-placed petals (Figs. 393 _A_, 394). _Corydalis_ has a
zygomorphic flower, _only one of_ the lateral petals _having a spur_,
and consequently there is only one nectary at the base of the bundle of
stamens, which stands right in front of the spur (Fig. 393 _B_, 395,
396). The fruit is a many-seeded siliqua-like capsule. ~A peculiarity
of the flower is that the plane of symmetry passes _transversely_
through the flowers, whilst in nearly all other zygomorphic flowers
it lies in the median line. Moreover, the flower is turned, so that
the plane of symmetry ultimately becomes nearly vertical, and the spur
is directed backwards.--Many species have subterranean tubers; in
these the embryo germinates with _one cotyledon_, which is lanceolate
and resembles a foliage-leaf. The tuber is in some the swollen
hypocotyl (_C. cava_), in others a swollen root (_C. fabacea_, etc.),
which grows down through the precisely similar swollen root of the
mother-plant. The sub-genus _Ceratocapnos_ has dimorphic fruits (nuts
and capsules) in the same raceme.~ _Fumaria_ differs from _Corydalis_
only by its almost drupaceous, one-seeded nut (Fig. 395).

  [Illustration: FIG. 393.--Diagram of _Dicentra_ (_A_),
  _Corydalis_ (_B_), and _Hypecoum_ (_C_).]

  [Illustration: FIG. 394.--_Dicentra spectabilis_: _A_ flower
  (2/5); _B_ the same, after removal of half of one outer petal;
  the cap, formed by the inner petals, is moved away from the
  anthers and stigma; the insect does this with the lower side of
  its abdomen, and thus rubs the stigma on the hairs of its ventral
  surface; the dotted line at _e_ indicates the direction of the
  proboscis; _C_ andrœcium and gynœceum; _D_ stigma.]

   THE STRUCTURE OF THE FLOWER. _Hypecoum_ among the Papaveraceæ
   is the connecting link with the Fumariaceæ. The diagram (Fig.
   393 _C_) corresponds both in number and in the relative position
   of its members with that of most of the other Papaveraceæ (Fig.
   391), except that there are only four stamens (with extrorse
   anthers). In _Dicentra_ (Fig. 393 _A_), the two central
   (uppermost) stamens are absent, but each of the two lateral ones
   are divided into three filaments, of which the central one bears
   a four-locular anther, and each of the others a two-locular
   (half) anther. _Corydalis_ and _Fumaria_ stand alone in the
   symmetry of the flower, differing from _Dicentra_ in having only
   one of the lateral petals (Fig. 393 _B_, _sp_) prolonged into
   a spur, while in _Dicentra_ both the petals are spurred. This
   structure has been interpreted in various ways. According to Asa
   Gray the median stamens are absent in the last-named genera, and
   the lateral ones are split in a similar manner to the petals of
   _Hypecoum_. Another, and no doubt the most reasonable theory
   (adduced by De Candolle), is: that two median stamens are split,
   the two parts move laterally, each to their respective sides
   and become united with the two lateral stamens; this affords a
   natural explanation of the two half-anthers, and establishes a
   close relationship to the Cruciferæ. A third interpretation,
   held by Eichler and others, is as follows: the median stamens
   are _always_ wanting; when they appear to be present, as in
   _Hypecoum_, it is due to the fact that the side portions of
   the lateral stamens _approach each other_ (as interpetiolar
   stipules) and coalesce into an apparently single stamen.

  [Illustration: FIG. 395.--_Fumaria officinalis_: _A_ the flower
  in longitudinal section; _B_ the andrœcium and gynœceum; nectary
  to the right.]

  [Illustration: FIG. 396.--_Corydalis cava_: _a_ a flower (lateral
  view); _b_ the anthers lying round the stigma; _c_ the anthers
  shortly before the opening of the flower; _d_ the head of the
  stigma; _e_ relative position of the parts of the flower during
  the visit of an insect.]

   130 species; mostly from the northern temperatures.

   POLLINATION. _Fumaria_, with its inconspicuous flowers, has to
   a great extent to resort to self-pollination. _Corydalis_, on
   the other hand, is dependent on cross-pollination; _C. cava_
   is even absolutely sterile with its own pollen. _Corydalis_
   is pollinated by insects with long probosces (humble-bees,
   bees), which are able to reach the honey secreted in the spur;
   as they alight on the flowers they press the exterior petals
   on one side (Fig. 396 _e_), so that the stigma, surrounded by
   the anthers, projects forward; the proboscis is introduced in
   the direction of the arrow in the figure, and during this act
   the under-surface of the insect is covered with pollen, which
   is transferred by similar movements to the stigma of another
   (older) flower.--Ornamental plants; _Dicentra_ (_spectabilis_
   and _eximia_), _Adlumia_, _Corydalis_.

Order 3. =Cruciferæ (Crucifers).= The flowers are _regular_, ☿; sepals
4, free (2 + 2), deciduous; petals 4, free, deciduous, unguiculate,
placed _diagonally_ in one whorl, and alternating with the sepals;
stamens 6; the 2 _outer_ are _short_, the 4 _inner_ (in reality the two
median split to the base) _longer_, placed in pairs (tetradynamia of
Linnæus); gynœceum syncarpous formed by 2 (as in the previous order,
lateral) carpels, with 2 parietal placentæ, but divided into two
loculi by a _spurious_ membranous dissepiment (_replum_) (Fig. 397).
Style single, with a capitate, usually two-lobed stigma, generally
commisural, that is, placed above the parietal placentæ (Fig. 397), but
it may also be placed above the dorsal suture, or remain undivided.
Ovules _curved_. The fruit is generally a bivalvular _siliqua_ (Fig.
398 _B_, _C_), the valves separating from below upwards, and leaving
the placentæ attached to the replum; other forms of fruits are
described below. The oily seeds _have no endosperm_ (endosperm is
present in the two previous orders); the _embryo is curved_ (Figs.
398 _E_, _F_; 399, 400).--In general they are _herbaceous_ plants,
without latex, with scattered, penninerved leaves, without stipules;
the inflorescence is very characteristic, namely, a raceme with the
flowers aggregated together at the time of flowering into a corymb, and
_destitute of both bracts and bracteoles_.

  [Illustration: FIG. 397.--Diagram of a Cruciferous flower.]

  [Illustration: FIG. 398.--_Brassica oleracea_: _A_ raceme; _B_,
  _C_ siliqua; _D_ seed; _E_ embryo; _F_ transverse section of
  seed.]

  [Illustration: FIG. 399.--Transverse section of seed and embryo
  of _Cheiranthus cheiri_.]

  [Illustration: FIG. 400.--Transverse section of seed of
  _Sisymbrium alliaria_.]

   Many are biennial, forming in the first year a close
   leaf-rosette. By cultivation the tap-root can readily be induced
   to swell out into the form of a tuber (Turnips, Swedes, etc.).
   _Stipules_ are found indicated by small glands on the very
   young leaves; in _Cochlearia armoracia_ they are fairly large
   triangular scales. _Stellate hairs_ often occur. _Floral-leaves_
   are occasionally developed. Terminal flowers are never found in
   the inflorescences. _Iberis_ and _Teesdalia_ have _zygomorphic_
   flowers. _Subularia_ (Fig. 403) is perigynous. The 2 external
   sepals (Fig. 397) stand in the median plane; it may therefore
   be supposed that there are two bracteoles outside these which,
   however, are suppressed, and can only in a few instances be
   traced in the young flower; the two lateral sepals are often
   gibbous at the base, and serve as reservoirs for the nectar
   secreted by the glands placed above them; they correspond in
   position to the external petals of the Fumariaceæ. The 4 petals
   which follow next arise simultaneously, and alternate with the
   4 sepals; if it could be shown that these are merely 2 median
   petals, which have been deeply cleft and the two parts separated
   from each other and displaced to the diagonal position, there
   would be a perfect correspondence with the Fumariaceous flower;
   then the petals would be followed in regular alternation by the
   2 lateral small stamens, the 2 median long stamens, which it
   has been proved are split into 4 and placed in couples, and the
   2 laterally-placed carpels,--in all 6 dimerous whorls. But the
   formation of the corolla by the splitting of 2 petals does not
   agree with the development of the flower or bear comparison, and
   hence the only fact in favour of this theory is the otherwise
   prevailing correspondence with the Fumariaceæ. Yet it may
   be observed that in special cases each pair of long stamens
   clearly enough arises from one protuberance and even later
   on may be considerably united or entirely undivided (_e.g._
   _Vella_); in other instances they are quite distinct from the
   beginning, and it is possible that this latter condition has
   become constant in the corolla. _Lepidium ruderale_ and others
   have no corolla. _Senebiera didyma_ has only 2 median stamens.
   _Megacarpæa_ has several stamens, no doubt by dédoublement, as
   in Capparidaceæ.--The _number of carpels_ may also be abnormally
   increased; _Tetrapoma barbareifolium_ has normally 4 carpels
   with an equal number of placentæ and repla. It is supposed to
   be a variety of _Nasturtium palustre_.--The 2–4–8–10 greenish
   _glands_, which are found at the base of the stamens, are
   nectaries, morphologically emergences, and not rudimentary
   stamens. The forms of _fruits_ are of great systematic
   significance, see the genera. In some species dimorphic fruits
   are present, _e.g. Cardamine chenopodiifolia_ which has both
   ordinary _Cardamine_-siliquas and 1-seeded siliculas.

   The _curved embryo_ appears in five forms, which have
   systematic importance: 1. To the PLEURORHIZÆ belong those
   genera whose radicle (with the hypocotyl) lies bent upwards
   along the _edge_ of the _flat_ cotyledons (Fig. 399); to
   this group belong _Cardamine_, _Nasturtium_, _Cheiranthus_,
   _Matthiola_, _Cochlearia_, _Draba_, _Iberis_, _Thlaspi_, etc.;
   diagrammatic transverse section: ◯=.--2. To NOTORHIZÆ belong
   those whose radicle lies in an upward direction along the
   _back_ of one of the _flat_ cotyledons (Figs. 400, 413); _e.g._
   _Hesperis_, _Sisymbrium_, _Lepidium_, _Capsella_, _Camelina_:
   ◯‖.--3. ORTHOPLOCEÆ differ from the Notorhizeæ in having the
   cotyledons folded (not flat) (Fig. 398 _E_, _F_); to this belong
   _Brassica_, _Sinapis_, _Raphanus_, _Crambe_, etc.: ◯>>.--4.
   SPIROLOBEÆ: the radicle lies as in the Notorhizæ, but the
   cotyledons are so rolled together that a transverse section of
   the seed cuts them twice; _Bunias_: ◯‖‖.--5. DIPLECOLOBEÆ: the
   cotyledons are folded forward and backward so that a transverse
   section cuts them several times; _Subularia_, _Senebiera_: ◯‖‖‖.

On _germination_ the cotyledons appear above the ground as green
leaves; in the Orthoploceæ they are bilobed, in the _Lepidium_-species
divided.

1. =Silicula, broad replum= (Siliculosæ latiseptæ), valves flat or
slightly vaulted, and the replum extends through the greatest width of
the silicula (Fig. 404). The seeds are situated in two rows.

◯=: _Cochlearia_ (Horse-radish): the siliqua is nearly spheroid;
glabrous herbs, generally with fleshy, stalked leaves, and white
flowers.--_Draba_ has an oblong, lanceolate, somewhat compressed
silicula; herbs with small rosettes of leaves, most frequently with
stellate and long-stalked racemes.--_Alyssum_ and _Berteroa_ are
whitish, on account of the stellate hairs; they have a more compressed
and round or elliptical silicula. _Vesicaria_; _Aubrietia_. _Lunaria_
(Honesty, Fig. 401): very broad and flat silicula with long stalk (the
receptacle as in Capparidaceæ).

◯‖: _Camelina_ (Gold-of-pleasure) has a spheroid, pear-shaped siliqua
with a small rim passing right round (Fig. 402). _Subularia_ (Awlwort),
an aquatic plant with _perigynous_ flower (Fig. 403) and folded
cotyledons.

2. =Silicula, narrow replum= (Siliculosæ angustiseptæ), _i.e._ the
replum is much shorter than the arched, more or less boat-shaped valves
(Figs. 405, 406, 407).

  [Illustration: FIG. 401.--_Lunaria biennis._ Fruit, the valves of
  which have fallen off.]

  [Illustration: FIG. 402.--_Camelina sativa._ Fruit.]

  [Illustration: FIG. 403.--_Subularia aquatica._ Longitudinal
  section through the flower.]

◯=: _Thlaspi_ (Penny-Cress) has a flat, almost circular silicula,
emarginate or cordate, with a well-developed wing round the edge (Fig.
406). _Iberis_ and _Teesdalia_: the racemes during flowering are
especially corymbose, and the most external petals of the outer flowers
project radially and are much larger than the other two (the flower is
_zygomorphic_).--_Biscutella_, _Megacarpæa_.

◯‖: _Capsella_ (Shepherd’s-Purse) has a wingless, obcordate or
triangular silicula (Fig. 407). _Lepidium_ (Pepperwort) has a few–(2–4)
seeded, slightly winged, oval silicula. _Senebiera_ has a silicula
splitting longitudinally into two nut-like portions; its cotyledons are
folded.--~_Anastatica hierochuntica_ (“Rose of Jericho”) is an annual,
silicula-fruited, desert plant (Arabia, Syria, N. Africa). After the
flowering all its then leafless branches bend together upwards, forming
a kind of ball; this spreads out again on coming in contact with water,
and the fruits then disseminate their seeds, which germinate very
quickly, often in the fruit.~

3. =Siliqua= (Siliquosæ). The fruit is a true siliqua, several times
longer than broad. The seeds in most are borne apparently in one row.

  [Illustration: FIG. 404.--Transverse section of a silicula with
  broad replum: _s_ replum; _k_ the valves.]

  [Illustration: FIG. 405.--Transverse section of a silicula with
  narrow replum.]

◯>>: _Brassica_ (Cabbage). The seeds are placed apparently in one
row in each loculus (Fig. 398 _C_); the style is long and round; the
valves have only 1 strong, longitudinal rib.--_Melanosinapis_ (_M.
nigra_, Black-mustard); the style is compressed, two-edged; the valves
of the siliqua are one ribbed.--_Sinapis_ (Mustard); quadrangular or
flat style (in which in most cases there is a seed) and 3–5 strong,
longitudinal ribs on the valves.--_Eruca_ differs from _Brassica_ by
the shorter siliqua, broad, sword-like “beak” and seeds in two rows.

◯= (Fig. 399): _Cardamine_ (Bitter Cress) has a long, linear siliqua,
with flat, unribbed, _elastic_ valves. The leaves are most frequently
pinnatifid or pinnate. ~_C. pratensis_ reproduces by buds formed
in the axils of the leaves.~--_Arabis_ (Rock Cress); _Matthiola_
(Stock); _Cheiranthus cheiri_ (Wallflower); _Barbarea_ (Winter Cress)
(double-edged, quadrangular siliqua); _Nasturtium_ (_N. officinale_,
Water-cress); the siliqua of the latter genus is in some species short,
in others long.

  [Illustration: FIG. 406.--_Thlaspi arvense._]

  [Illustration: FIG. 407.--Silicula of _Capsella bursa-pastoris_.]

◯‖ (Fig.400): _Sisymbrium_ (Hedge Mustard) the valves of the siliqua
are 3-ribbed.--_Erysimum_; _Hesperis_; _Schizopetalum_ (with fimbriate
petals).

4. =Fruit jointed= (Lomentaceæ). The fruit is divided by transverse
walls into as many spaces as there are seeds, and dehisces at maturity,
generally _transversely_, into a corresponding number of nut-like
joints (“articulate-siliqua.”)

◯=: _Crambe_ (Kale, Fig. 408). The fruit has only 2 joints. The lower
one resembles a short, thick stalk, and is barren, the upper one is
spherical, and has 1 seed.--_Cakile_ (_C. maritima_, Sea-kale); the
lower node is triangular, 1-locular, the upper one more ensiform,
1-locular (Fig. 409).

  [Illustration: FIG. 408.--Fruit of _Crambe maritima_.]

  [Illustration: FIG. 409.--_Cakile maritima._ Fruit (2/1).]

  [Illustration: FIG. 410.--_Raphanus raphanistrum._]

  [Illustration: FIG. 411.--_Raphanus sativus._]

◯>>: _Raphanus_ has a long siliqua, which, in the garden Radish (_R.
sativus_), is spongy and slightly abstricted (Fig. 411), but neither
opens nor divides transversely (a kind of dry berry), and which in the
Wild Radish (_R. raphanistrum_) (Fig. 410) is abstricted in the form
of a string of pearls, and separates into many joints. ~_R. sativus_;
the “Radish” is formed by the hypocotyl, after the bursting of its
external, cortical portions (of which there are generally two patches
at the top of the Radish).~

5. =Siliqua indehiscent= (Nucumentaceæ). The fruit is a short,
_unjointed_, unilocular and 1-seeded nut, and the fruit-stalks are
often long, slender, and drooping. (Sometimes a thin endosperm is
present).--_Isatis_ (Woad) has most frequently an oblong, small-winged
nut; ◯‖ (Figs. 412, 413).--_Bunias_; _Neslia_.

   [The systematic division of this order given above is founded
   upon that of A. P. de Candolle. Prantl (_Engler and Prantl, Nat.
   Fam._), 1891, adopts a somewhat different system, which may
   briefly be summarised as follows:--

   _A._ Hairs unbranched or absent; no glandular hairs.

      1. THELYPODIEÆ. Stigma equally developed on all sides; style
           undivided or prolonged above the middle of the carpels,
           or turned back.--_Stanleyinæ_; _Heliophilinæ_.

      2. SINAPEÆ. Stigma strongly developed above the placenta;
           style beaked or two-lobed.

           _a._ Cotyledons arising behind the bend of the
                  embryo.--_Lepidiinæ._

           _b._ Cotyledons arising at the bend of the embryo.

                α. Only lateral nectaries. Generally a silicula or
                   indehiscent fruit.--_Cochleariinæ._

                β. Generally a siliqua, more rarely a silicula or
                     transversely-divided or indehiscent fruit.
                     Nectaries generally lateral and
                     median.--_Alliariinæ_; _Sisymbriinæ_; _Vellinæ_;
                    _Brassicinæ_; _Cardamininæ_.

   _B._ Hairs collectively or partially branched, very rarely
   entirely absent; glandular hairs are sometimes also present.

      1. SCHIZOPETALEÆ.

      2. HESPERIDEÆ. Stigma strongly developed above the placenta;
           style undivided or prolonged above the placentæ into
           shorter or longer lobes.

             _a._ Surface cells of the replum, not divided
                  diagonally.--_Capsellinæ_; _Turritinæ_;
                  _Erysiminæ_; _Alyssinæ_.

             _b._ Surface cells of the replum divided
                  diagonally.--_Malcolmiinæ_; _Hesperidinæ_;
                  _Moricandiinæ_.]

  [Illustration: FIG. 412.--_Isatis tinctoria._ Fruit (Fig. 412);
  and in longitudinal section (Fig. 413). (Mag.)]

   POLLINATION. Honey is secreted by the nectaries mentioned
   above; but the position of the stamens is not always the most
   favourable for pollination by insects (in these flowers the
   honey-seeking insect must touch the anthers with one of its
   sides and the stigma with the other), and self-fertilisation
   is common. In some species (_Cardamine pratensis_) the long
   stamens turn their anthers outwards towards the small stamens,
   so that 3 anthers surround each of the two large entrances to
   the nectaries.

   1200 species (180 genera), especially in the cold and
   temperate parts of the Old World (Europe, W. Asia). Many
   are _weeds_ in this country, _e.g._ Wild Cabbage (_Brassica
   campestris_), Charlock (_Sinapis arvensis_), Wild Radish
   (_Raphanus raphanistrum_) and others.--The order is acrid and
   oleaginous. Oil is obtained from many of the oil-containing
   seeds, especially of the Rape (_Brassica napus_), Summer-Rape
   (the oil-yielding cultivated form of the Field-Cabbage) and
   _Camelina_. Several are pot-herbs or fodder plants, _e.g._
   Cabbage

   (_Brassica oleracea_) with its numerous varieties: Cauliflower
   (var. _botrytis_; the entire inflorescence is abnormally
   branched and fleshy), Kohlrabi (var. _gongylodes_, with
   swollen, tuberous stem), Kale, Red-Cabbage, White-Cabbage,
   etc.; _B. campestris_, var. _rapifera_ (Turnip); _B. napus_,
   var. _rapifera_ (Swede); _Raphanus sativus_ (Radish from W.
   Asia), _R. caudatus_ (long Radish); _Nasturtium officinale_
   (Water Cress), _Lepidium sativum_ (Garden Cress), and _Barbarea
   præcox_ (Early Cress); _Crambe maritima_ (Sea-Kkale). The
   seeds of the following are especially used as spices: (the
   flour of) _Melanosinapis_ (Black-mustard), and _Sinapis
   alba_ (White-mustard), which are _officinal_ like the root
   of _Cochlearia armoracia_ (Horse-radish, E. Eur.). The
   herbaceous parts of _Cochlearia officinalis_ and _danica_
   are medicinal.--A blue dye (woad) is extracted from
   _Isatis_.--Ornamental plants: _Cheiranthus cheiri_ (Wallflower),
   _Matthiola_ (Stock), _Iberis_, _Hesperis_, _Lunaria_, and others
   (especially from S. Eur.). Sweet-scented flowers are rare.

  [Illustration: FIG. 414.--_Gynandropsis pentaphylla._]

  [Illustration: FIG. 415.--_Capparis spinosa._]

   Order 4. =Capparidaceæ= (=Capers=). The relationship with the
   Cruciferæ is so close that certain forms are with difficulty
   distinguished from them. The diagram of the flower is the same
   in the number and position of its parts, but it differs in the
   modifications which occur in the development of the stamens. In
   some genera all 4 stamens are undivided; in others both the 2
   median ones are divided as in the Cruciferæ (6 stamens, but _not
   tetradynamous_) (Fig. 414); in other genera only 1 of these; in
   other instances again they are divided into more than 2; and
   finally the 2 lateral ones also may be found divided, so that
   _indefinite stamens_ occur (Fig. 415). The bicarpellate gynœceum
   is _unilocular_ (without replum), but more than 2 carpels may
   occur. The ovary is elevated on a _stalk_ (sometimes as much
   as 1 foot in length); also between the stamens and corolla a
   similar stalk may be found (Fig. 414). The fruit is long and
   siliquose (_Cleome_, _Polanisia_, _Gynandropsis_), or a berry
   (_Capparis_). Endosperm absent. Some have zygomorphic flowers.
   Gamosepalous calyx and perigynous flowers also occur.--350
   species; especially in the Tropics. The majority are trees
   and shrubs, and they differ also from the Cruciferæ in having
   distinct stipules present in some species.

   “Capers” are the flower buds of the climbing, thorny shrub,
   _Capparis spinosa_ (Fig. 415), which grows in the Mediterranean.


                       Family 11. =Cistifloræ.=

The flowers in this family are perfect, regular (except _Resedaceæ,
Violaceæ_), hypogynous, the perianth-leaves free (a few have them
slightly united), æstivation most frequently imbricate; they are
eucyclic in the andrœcium, and most frequently in the other parts,
and generally 5-merous with S5, P5, A5 + 5, G3, but other numbers
also occur; several have _indefinite stamens_, but the stamens arise
(where the development is known) in _centrifugal order_ and are
arranged, often very distinctly, _in bundles_; in other words, the
large number of stamens is formed by the splitting of a small number
(most frequently 5); a true spiral arrangement is never found. Gynœceum
syncarpous, multicarpellary (_Dilleniaceæ_ and a few _Resedaceæ_ are
apocarpous), most frequently the number of carpels is 3, forming a
_unilocular ovary_ with _parietal placentæ_, but parallel with this,
multilocular ovaries, with the ovules placed in the inner angle of the
loculi, are also found, and a few genera have a free, centrally-placed
placenta. The fruit is most frequently a capsule. The dehiscence is
never with a “replum,” _i.e._ the persistent frame of the placenta,
as in the family Rhœadinæ. One half of the orders has endosperm
(_Violaceæ_, _Cistaceæ_, _Droseraceæ_, _Bixaceæ_, _Ternstrœmiaceæ_,
etc.), the other has no endosperm (_Resedaceæ_, _Hypericaceæ_,
_Elatinaceæ_, _Tamaricaceæ_, etc.); some have a curved, the majority a
straight embryo. ~The family is scarcely quite natural; in the future
the orders will probably be arranged differently.~

Order 1. =Resedaceæ (Mignonettes).=--Herbs or small shrubs with
spirally-placed leaves and very small, gland-like stipules (as in
Cruciferæ); the ☿, hypogynous flowers are _zygomorphic_, and arranged
in racemes or spikes typically without bracteoles. The zygomorphic
structure is produced by the _greater development of the posterior side
of the flower_, especially the petals and the nectary (“disc,” in Fig.
416 _d_) which is situated between the petals and stamens; in general
there are 5–8 free sepals and petals, the latter consisting of a large
scale-like _sheath_ with a fimbriated blade (see Fig. 416); stamens
numerous; carpels 6–2 united together; ovary unilocular with parietal
placentæ, but _the cavity of the ovary is not closed_ at the top. In
_Astrocarpus_ the gynœceum is apocarpous. The fruit is most frequently
a capsule; the seeds are reniform, without endosperm, and the embryo is
_curved_.

   This order connects the Rhœadinæ with the Cistifloræ. It is
   closely allied to the Rhœadinæ by its external appearance, even
   by the smell and taste, the parietal placentation, structure of
   the seeds, the inflorescences, etc., whilst by the irregular
   flowers and the disc placed at the posterior side of the
   flower, _it is allied to Capparidaceæ_, but differs from this
   order in not having its characteristic number (2–4) and by
   the very different mode of dehiscence of the fruit, etc. It
   differs from the other orders of this family chiefly in the
   fact that the number of the perianth-leaves is not constantly
   5. In _Reseda luteola_ both the calyx and corolla appear to
   be 4-leaved, because the posterior sepal is suppressed, and
   the 2 posterior petals are united. Where there are 10 stamens,
   they stand in 2 whorls, _i.e._ in front of the sepals and
   petals; if there are several, their position depends upon the
   splitting.--_Astrocarpus_ is remarkable for its apocarpous fruit
   and the position of the ovules on the _dorsal_ suture of the
   carpel.

   The yellow, flat disc at the back of the flower serves as a
   nectary, the honey being protected by the lobes of the petals.
   If pollination by insects is not effected, then self-pollination
   may take place, at all events in _R. odorata_.

   45 species; the majority in the Mediterranean and in Persia.
   _Reseda odorata_ (from Egypt) is cultivated on account of its
   sweet scent; _R. luteola_ (“Dyer’s Weed”) yields a yellow dye.

  [Illustration: FIG. 416.--Diagram of _Reseda odorata_.]

Order 2. =Droseraceæ (Sundews).= Herbs, chiefly living on moors or in
water, and whose leaves are adapted to catch and digest small animals.
With regard to the flower, they are closely allied to the Violaceæ,
especially to those with regular flowers. _Drosera_ (Sundew) has a
long-stalked scorpioid cyme with regular, ☿, hypogynous flowers,
5-merous as in _Viola_. S5, P5, A5, G3 (in a syncarpous gynœceum,
with free, bifid styles and basal or parietally-placed ovules in the
unilocular ovaries). The capsule opens also as in _Viola_, but, among
other differences, the styles are free, the seeds very small, and
surrounded by a loosely lying, thin shell. ~_Drosera_ has radical,
long-stalked leaves with the blade (Fig. 417) covered by numerous
strong glandular hairs, placed on the edge and in the middle; when
small animals are caught by these hairs, the latter and the entire
blade close slowly over them dissolving and absorbing all the
digestible matter as nourishment.~

  [Illustration: FIG. 417.--Leaf-rosette of _Drosera rotundifolia_
  (nat. size), and a leaf (magnified).]

   _Dionæa muscipula_ (Fly-trap; N. Am.) has the same appearance
   as _Drosera_, but the leaves are constructed as in Fig. 418.
   The stalk is flat and winged, the blade small, circular, with
   powerful, pointed teeth along the edge, and on its surface are 6
   small bristles (_A_), which are very sensitive. When these are
   touched the blade quickly closes, folding along the midrib (_B_,
   _C_) and imprisoning the irritating object, the teeth round the
   edges fitting like the teeth of a trap. If it happens to be an
   insect or similar body, a digestive fluid is secreted which,
   like the gastric juice, dissolves the digestible portions.
   _Aldrovandia vesiculosa_ (Central and S. Europe) captures small
   aquatic animals in a similar manner; it is a floating, aquatic
   plant, the two halves of its leaves also close together when
   irritated (Fig. 419).--_Drosophyllum._

   About 110 species; most of them in the temperate regions.

  [Illustration: FIG. 418.--_Dionæa muscipula._ Leaves (nat. size).]

   Orders 3 and 4. =Sarraceniaceæ and Nepenthaceæ.= These two
   orders are perhaps most closely allied to the Droseraceæ and
   agree with these, among other things, in the manner of taking
   nourishment. Like the Droseraceæ they absorb nitrogenous food
   from dissolved animal matter by means of their leaves, which are
   specially constructed both to catch, to retain, and to digest
   any small animals which may be caught. The SARRACENIACEÆ are
   North American marsh-plants (10 species) which have pitcher-like
   leaf-stalks, in the cavity of which a fluid (with properties
   approaching those of gastric juice) is secreted, and which bear
   at the apex a small, lid-like blade; these leaf-stalks are the
   catching and digestive organs.--_Sarracenia, Darlingtonia._

  [Illustration: FIG. 419.--_Aldrovandia vesiculosa_: _A_ a plant
  (nat. size). _B_ Leaf (mag.); the blade is closed; the winged
  stalk is prolonged into 4–6 irritable bristles.]

  [Illustration: FIG. 420.--_Nepenthes_ (reduced).]

   NEPENTHACEÆ has only 1 genus, _Nepenthes_ (the Pitcher-plant;
   about 35 species), especially found in tropical E. Asia; the
   majority are climbing shrubs. The leaf-stalks are twining
   organs, and terminate either simply in a tendril, or in addition
   to this, with a pitcher-shaped body (which in some species may
   be as much as a foot in length) on whose upper edge a lid-like
   structure is found (Fig. 420). In this pitcher, as among the
   Sarraceniaceæ, a fluid is secreted which is able to digest the
   animals captured (sometimes rather large) and which corresponds
   in some degree to the gastric juice.

Order 5. =Violaceæ (Violets).= The flowers are ☿, and generally
zygomorphic, hypogynous, with S5, P5, A5, G3 (Fig. 421). The stamens
are closely applied to the ovary, they have a very short filament,
and at their summit generally a membranous appendage formed by the
prolongation of the connective (Fig. 422 _g_). The ovary is unilocular
with 3 parietal placentæ; style undivided (Fig. 422 _B_). The fruit
is usually a 3-valved capsule, opening along the dorsal sutures
(Fig. 423). Embryo straight; endosperm fleshy (Fig. 425).--Many are
herbaceous plants (_e.g. Viola_), but in the Tropics shrubs are also
found (_e.g. Ionidium_); a few are lianes; the leaves are scattered,
with stipules, and involute in the bud.

  [Illustration: FIG. 421.--Diagram of _Viola_.]

  [Illustration: FIG. 422.--The large-flowered form of _Viola
  tricolor_: _A_ the flower in median longitudinal section; _B_ the
  gynœceum.]

_Viola._ The sepals are prolonged backwards beyond the point of
insertion (appendiculate); the corolla is polypetalous, descending
imbricate, and zygomorphic, its anterior petal being larger than the
others and provided with a spur (Fig. 421). The 2 anterior of the 5
almost sessile stamens are provided with a spur-like nectary, which
protrudes a considerable distance into the petaloid spur (Figs. 421,
422 _n_, _sp_). The style is club-like, and bears the stigma in a
groove on the anterior side (Fig. 422 _st_). ~Herbs with rhizomes,
or annuals; flowers solitary. _V. odorata_, _canina_, etc., have
cleistogamic flowers which produce fruit in addition to the large,
coloured (violet) flowers. The Pansy (_V. tricolor_) has large flowers
adapted for insect-pollination, and also smaller, less conspicuous
ones designed for self-pollination. The stigma, as in Fig. 422 _A_,
_st_, and _B_, is situated on the anterior side of the stylar-head,
immediately in front of the channel leading down to the spur (_sp_);
below it is situated a valve, easily covered with pollen when
the proboscis of an insect is introduced into the spur, but which
closes upon its withdrawal; cross-pollination is thus secured.--The
sweet-scented _V. odorata_ is visited by the honey-bee, which insures
cross-pollination, and in the absence of insect visits it effects
self-fertilisation by cleistogamic flowers. The conspicuous but
scentless _V. tricolor_, var. _vulgaris_, is less frequently visited by
insects (humble-bees). In _V. silvatica_ and _V. canina_ the pollen is
carried on the head or proboscis of the honey-sucking bee.--The fruits
of _V. odorata_ bury themselves slightly in the soil. In the others
the fruits are raised above the ground; the 3 boat-shaped valves close
together along the central line, and eject the seeds, one by one, with
much violence, so that they are thrown to a great distance.~

  [Illustration: FIGS. 423–425.--_Viola Tricolor._

  FIG. 423.--Capsule after dehiscence (nat. size).

  FIG. 424.--External view of the seed.

  FIG. 425.--Seed in longitudinal section.]

   The _Alsodeia_-group has regular or almost regular flowers.
   Gamopetalous corollas are found in _Paypayroleæ_. _Sauvagesieæ_
   differs the most by its regular corolla, and 5–∞ free or united
   staminodes.

   250 species; especially in the Tropics.--The _Ionidium_-species
   are used as ipecacuanha. A number of _Viola_-species are
   cultivated as garden plants, especially _V. odorata_
   (sweet-scented Violet) and _V. tricolor_, which have a large
   number of varieties.

   Order 6. =Frankeniaceæ.= A small order with doubtful
   relationships. Perennial herbs or shrubs; beach plants with
   nodose stem. Sepals united, petals free. Unilocular ovary,
   with 3–4 parietal placentæ. Fruit a capsule. Embryo straight,
   endospermous. Especially in S. Europe, Africa, on the shores of
   the Mediterranean and Atlantic.

   Order 7. =Tamaricaceæ (Tamarisks).= To this order belong only
   _Tamarix_ and _Myricaria_. They are shrubs of a cypress- or
   heather-like appearance, as the scattered leaves are very small,
   sessile, scale-like or linear, adpressed, entire, and usually
   glaucous, and the branches are slender and whip-like. The
   flowers are borne in small spikes or racemes, and are small,
   reddish or whitish, regular, ☿, hypogynous and polypetalous;
   formula S5, P5, A5 + 0 (_Tamarix_, which often has stipular
   teeth at the base of the filaments), or A5 + 5 (_Myricaria_,
   in which the stamens are united at the base); the number 4 may
   appear instead of 5, but in either case there is usually a
   tricarpellate gynœceum, which is _unilocular_ and has either
   parietal placentæ (_Myricaria_) or a small basal placenta
   (_Tamarix_); 1 trifid style, or 3 styles. Capsule dehiscing
   along the dorsal suture, and resembling the Willows in having a
   unilocular ovary with numerous _woolly_ seeds; but the seed-wool
   in this case is borne on the chalaza, and may be attached to a
   long stalk.--Some _Tamarix_-species shed part of their branches
   in the winter.--40 species; North Temperate, on the sea-shores
   or steppes, especially in Asia. Ornamental shrubs: _Myricaria
   germanica_, and _Tamarix gallica_.

Order 8. =Cistaceæ.= Shrubs or herbs, natives especially of the
Mediterranean region. Flowers generally in raceme-like scorpioid
cymes, regular, ☿, hypogynous; sepals 5, free, _twisted_ in the bud,
of which the two outer are generally much smaller than the others;
petals 5, free, _twisted_ in the bud (in the direction _opposite_
to the sepals), fugacious; stamens _numerous_; gynœceum syncarpous,
carpels usually 3–5, style simple, ovary unilocular, with parietal
placentation (seldom divided into loculi, with axile placentation). The
ovules are _orthotropous_ in opposition to some of the other orders
of this family. The capsule dehisces along the dorsal sutures; embyro
_curved_. The leaves are simple, undivided, generally opposite and
stipulate.--~They are Violaceæ with regular flowers, numerous stamens,
and curved embryo. The numerous stamens are in reality only one or two
5-merous whorls, divided into a large number of stamens; these are
formed, therefore, in descending order, like the lobes of many compound
foliage-leaves.~

_Helianthemum_ (Rock-Rose), has 3 carpels.--_Cistus_ has 5 (-10)
carpels.

   About 70 species; temperate climates, especially about the
   Mediterranean. The resin of the _Cistus_-species has been used
   medicinally (ladanum).

   Order 9. =Bixaceæ.= This order is closely allied to the Cistaceæ
   and Ternstrœmiaceæ; like these it has regular, 5-merous,
   hypogynous flowers with numerous stamens, unilocular ovary and
   _parietal_ placentæ; sometimes unisexual flowers; it differs in
   having anatropous ovules, in the æstivation of the sepals, etc.
   All species (about 180) are trees or shrubs, with scattered,
   simple leaves, which usually have stipules, and are occasionally
   dotted with pellucid oil-glands.--_Bixa orellana_ (Trop. Am.)
   is the best known species; it has a 2-valved capsule; the seeds
   are enclosed in a shiny _red, fleshy testa_, which contains the
   well-known orange or yellow dye, annatto.

   Order 10. =Dilleniaceæ.= Gynœceum usually apocarpous, seed
   arillate. The flower has most frequently S5, P5, and compound
   stamens (one or more bundles); sometimes irregular. 200 species;
   Tropical; woody plants, many lianes.--_Dillenia_, _Candollea_,
   _Pleurandra_, _Davilla_, etc.

   Order 11. =Elatinaceæ= (=Water-worts=). About 25 species belong
   to this order; especially in temperate climates. They are small,
   creeping, rooted, aquatic plants, with opposite or verticillate
   leaves and _stipules_. The flowers are solitary or situated in
   small dichasia in the leaf-axils, they are small, regular, ☿,
   hypogynous, with free petals, the same number in all 5 whorls
   (Sn, Pn, An + n, Gn), 3-merous (_e.g. Elatine hexandra_),
   4-merous (_e.g. E. hydropiper_), or 5-merous (_Bergia_); the
   corolla-stamens are sometimes suppressed; petals imbricate
   without being twisted; the ovary is 3–4–5-locular, with 3–4–5
   _free styles_; the capsule dehisces septicidally. The seeds are
   orthotropous or curved, often transversely ribbed, endosperm
   wanting. The order is most nearly allied to Hypericaceæ, whose
   primitive form it appears to represent.

  [Illustration: FIG. 426.--Diagram of _Hypericum quadrangulum_:
  _S_ indicates the bud of the helicoid cyme in the axil of the
  bracteole β.]

  [Illustration: FIG. 427.--_Hypericum._ Flower with three bundles
  of stamens.]

Order 12. =Hypericaceæ= (=St. John’s-worts=). This order is recognised
by its always _opposite_ or _verticillate_, _simple_, and entire,
penninerved leaves, without stipules, and usually dotted with
_pellucid_ glands; by the always ☿, regular, hypogynous flowers in a
cymose inflorescence; the generally 5-merous calyx and corolla, with
sepals and petals free; the stamens 3–5, numerously branched (Figs.
426, 427); and the gynœceum, 3–5-carpellate, styles usually _free_. The
ovary is 3–5-locular, or unilocular with 3–5 parietal placentæ. Fruit a
capsule (dehiscing septicidally) or berry. Endosperm absent.

   The inflorescence is a _dichasium_ or _helicoid cyme_. The
   structure of the flowers is the same as that of the foregoing
   orders: S5, P5; succeeding these in some cases are two 5-merous
   whorls of stamens in regular alternation, of which the inner
   is epipetalous; but the outer whorl is only represented by 5
   small scales (Fig. 427), or is altogether absent (_Hypericum
   calycinum_, _H. hircinum_), and the inner divided into numerous
   stamens, that is, these 5 stamens are so deeply divided that
   5 _epipetalous_ groups bearing anthers are found (as in the
   Cistaceæ); in other cases the flower becomes _3-merous after
   the petals_, stamens 3 + 3 following in regular alternation
   (Figs. 426, 427), the outer whorl of stamens in these cases is
   also present as staminodes (Fig. 427), or may be altogether
   suppressed. Carpels 3–5. _The petals are often twisted_ in the
   bud, and are then oblique.

_Hypericum._ Some species have a square stem; in these cases the
leaves are placed opposite the edges. Fruit a capsule.--_Vismia_ has
a berry.--~The flowers of _Hypericum_ have no honey, and supply only
pollen; self-pollination often takes place.~

   About 240 species; the tropical ones being often shrubs or
   trees; the others generally perennial shrubs.--_Hypericum_,
   St. John’s-wort, contains a resinous, red matter, which can be
   extracted with alcohol. The American gamboge is the dried sap of
   species of _Vismia_.

   Order 13. =Guttiferæ=, or =Clusiaceæ=. Closely allied to the
   Hypericaceæ and Ternstrœmiaceæ. Leaves opposite or verticillate.
   The flowers are often unisexual; stamens united; the gynœceum
   has most frequently a sessile, radiating or shield-like stigma.

   370 species; chiefly in the Tropics (Am.). They are principally
   woody plants and their bark contains a yellow gum resin,
   “gamboge,” which is extracted from _Garcinia morella_ (E. Ind.)
   and others. Mangosteen (_Garcinia mangostana_ S.E. Asia), and
   _Mammea americana_ (W. Ind.), have very delicious fruits.
   To this order also belong _Platonia insignis_, _Pentadesma
   butyracea_ (the Butter-tree), _Clusia_, _Calophyllum_, _Cataba_,
   etc.

Order 14. =Ternstrœmiaceæ.= Trees and shrubs with scattered, simple,
and often more or less leathery, evergreen, penninerved leaves, without
stipules (Fig. 428). The two most important genera are: _Camellia_
and the closely allied _Thea_ (by some authorities these are united
into one genus). The flowers are regular, hypogynous, and situated
singly on very short stalks. A number of green floral-leaves are placed
below the calyx and gradually pass over into the sepals, and the
leaves (5–6) of the calyx again gradually pass over into the corolla
(this being especially marked in _Camellia_), of which the number of
leaves varies (5, 6, 7 and upwards); the calyx and the corolla are
_acyclic_ or _eucyclic_; the petals are slightly united at the base;
stamens _numerous_ in many whorls, the external ones are arranged in
bundles and united with the petals as in the Columniferæ; gynœceum
syncarpous; styles often _free_ nearly to the base; ovary 3–5-locular,
ovules numerous in each loculus. The fruit is a woody capsule.--~Other
genera show more distinctly than these the same structure as in the
preceding orders, namely: S5, P5, A5 + 5, of which the calyx-stamens
are often suppressed, and the petal-stamens divided into numerous
stamens.--_Kielmeyera_ (S. Am.)~

   260 species; especially in the Tropics (E. Asia, Am.) The
   leaves of _Thea chinensis_ (or _Camellia thea_), the Tea-tree
   (E. Asia), are cultivated for the well-known “tea,” and contain
   theine: the best are the young, still hairy leaves, of greyish
   colour; there are many varieties. Ornamental plants, _Camellia
   japonica_ and _Actinidia_.

  [Illustration: FIG. 428.--_Thea chinensis_ (reduced).]

   Closely allied to this order are: Order 15. =Rhizoboleæ= (with
   enormously large hypocotyl--hence the name), and Order 16.
   =Marcgraviaceæ= (partly epiphytes, with dimorphic leaves and
   cup- or helmet-like, coloured, honey-secreting floral-leaves,
   which serve to attract insects).

   Order 17. =Dipterocarpaceæ.= This order has taken its name from
   the large wings attached to the fruits in _Dipterocarpus_ (the
   wings being largely developed sepals); trees and shrubs from
   Trop. Asia. 180 species. Camphor ready prepared is found in the
   stem of _Dryobalanops camphora_. _Hopea_; _Vateria_.


                        Family 12. =Gruinales.=

The flowers are hypogynous, ☿, polypetalous, usually regular (except
_Pelargonium_, _Tropæolaceæ_, _Balsaminaceæ_) and _throughout
5-merous_: S5, P5, A5 + 5, or 5 + 0, G5 (_epipetalous_). The stamens
soon fall off and are _obdiplostemonous_, often united at the base
(_monadelphous_); the corolla-stamens are in some completely suppressed
(_e.g. Balsaminaceæ_, Fig. 438), in others reduced to teeth (_Linum_,
Fig. 431; _Erodium_). The _Tropæolaceæ_ have 3 carpels and only 8
stamens (Fig. 437). Ring-like nectaries are not present, but at most
only glandular bodies, borne outside the base of the stamens. Ovaries
many-locular. The ovules as a rule are pendulous, with the micropyle
directed outwards (Fig. 431, B), and the radicle therefore also points
outwards. Usually _herbs_. Related to the Columniferæ.

Order 1. =Oxalidaceæ.= Most of the species are herbs with rhizomes;
the leaves are stalked, _compound_, with entire leaflets which are
folded and bent backwards in the bud (and in the sleep position),
exstipulate; some species have sensitive leaves. The flowers (Fig. 429)
are regular, and have S5, P5, which are _twisted_ to the left or right
in æstivation, A5 + 5, all united at the base (monadelphous), gynœceum
5-carpellate, _styles 5 free_, stigmas capitate, ovary 5-locular,
ovules numerous. The fruit is a _capsule opening_ with clefts _on the
dorsal sutures_ through which the seeds are ejected, while the _fleshy,
external layer of the testa_ springs off elastically. Embryo straight.
Endosperm.

  [Illustration: FIG. 429.--Diagram of _Oxal’s acetosella_.]

   _Oxalis_ (Wood-Sorrel). Leaves digitate. Species also occur
   with phyllodia, _i.e._ leaf-like petioles placed vertically
   without lamina; a few have pinnate leaves. The flowers are
   situated singly or in dichasia, and unipared scorpioid cymes.
   The pollination is effected by insects. Some species are
   trimorphic (long-, short-, medium-styled flowers) and some,
   _e.g. O. acetosella_, have cleistogamic flowers in addition
   to the ordinary ones. Glands are found on the outer side of
   the corolla-stamens or of all the stamens. _O. tetraphylla_
   and others have adventitious edible roots, resembling
   tap-roots.--_Averrhoa_ is a tropical tree, with berries and
   pinnate leaves.

   235 species (205 belong to _Oxalis_); chiefly in S. Africa and
   Trop. America.--Oxalate of potash is contained in the leaves of
   _Oxalis_.

Order 2. =Linaceæ.= Herbs with scattered or opposite, sessile,
_simple_, small, entire leaves, without (rarely with small) stipules.
The flowers (Fig. 430) are regular, 5- or 4-merous. Petals are free,
_twisted_, quickly falling off. Stamens united at the base; the
petal-stamens _are either reduced to teeth_ (Fig. 431 _A_, _m_) _or
entirely suppressed_. _Styles free._ The (5–4) epipetalous loculi
of the ovary are incompletely halved by _false divisional walls_,
each half contains one ovule (Fig. 431 _C_). The fruit is a spherical
_capsule, dehiscing along the divisional wall_ (Fig. 432); the 10 (-8)
seeds have a straight embryo and very slight endosperm (Fig. 433).

  [Illustration: FIGS. 430–433.--_Linum usitatissimum._

  Fig. 430.--The Flax plant.

  Fig. 431.--_A_ Flower after removal of sepals and petals; _m_
  petal-stamens reduced to teeth. _B_ Longitudinal section of
  ovary. _C_ Transverse section of capsule.

  Fig. 432.--Capsule (nat. size).

  Fig. 433.--Transverse and longitudinal section of seed: _bl_ the
  cotyledons; _k_ the plumule; _R_ the radicle; _fr_ the endosperm;
  _sk_ the testa.]

_Linum_ (Flax) has 5-merous flowers. ~The main axis terminates in a
flower; and the succeeding branching is cymose, or unipared scorpioid
branching by unilateral development, and the flowers in consequence of
the vigorous sympodial development of the lateral axis (and also by the
leaves being displaced and pushed aside), assume a position apparently
lateral (_i.e._ racemose) without bracts; each branch of the sympodium
generally has 2 leaves. The testa is shining and smooth when dry, but
its external cellular layer becomes mucilaginous in water.~--_Radiola_
has a 4-merous flower. It is a small herb with opposite leaves, and
regular, dichasial branching.

   The anthers and stigmas in _L. catharticum_ and _usitatissimum_
   develop simultaneously, and cross-pollination as well as
   self-pollination takes place. _L. grandiflorum_, _perenne_,
   and others, are dimorphic (short-and long-styled). There are 5
   nectaries outside the stamens.

   130 species; _Linum_ and _Radiola_ are native genera.--_L.
   usitatissimum_ is extensively cultivated in Europe (especially
   in Russia and Belgium), N. America and elsewhere (its home no
   doubt being Asia), partly on account of the oil (linseed oil)
   which is extracted from the seeds, and partly on account of
   the bast of the stem, which has very thick-walled cells. The
   seeds and oil are OFFICINAL. The species cultivated in ancient
   times was _L. angustifolium_. Several species are cultivated as
   ornamental plants.

Order 3. =Geraniaceæ.= The majority are herbs with dichasial branching,
and scattered or opposite, stalked, _palminerved_ (rarely penninerved)
leaves with small _stipules_. The flowers are regular (except
_Pelargonium_) and 5-merous, with 10 or 5 stamens, which are slightly
united at the base. Nectaries alternate with the corolla-stamens.
The ovary is most frequently 5-locular, deeply 5-grooved, and bears
1 _well developed style_ (“beak”), which towards the apex divides
into 5 branches bearing stigmas; ovules 1 in each loculus, pendulous
or ascending. _The 5 carpels become detached from one another when
ripe_, and bend or _roll back_ (Fig. 434) or become _spirally twisted_
in the upper “beak-like” part (Figs. 435, 436), whilst a _central
column_ (septal column) persists; each carpel, in consequence, remains
either closed, and the fruit is a 5-merous _schizocarp_ whose nut-like
lower portion, containing the seed, is forced into the ground, thus
burying the seed by the movements of the spirally-twisted, hygroscopic
“beak” (Figs. 435, 436); or it opens along the ventral suture, so
that the seeds may fall out, and it is then a 5-valved _capsule_,
with septicidal dehiscence (Fig. 434) and the rolling up often takes
place so suddenly and violently that the seeds are shot out to
considerable distances. The embryo is usually green and _curved_, and
the _cotyledons are folded_; endosperm is wanting.

_Geranium_ (Crane’s-bill) has 5 + 5 stamens,and a septicidal capsule;
the carpels most frequently remain suspended from the apex of the
column (Fig. 434). The leaves are most frequently palminerved. The
flowers are situated solitarily or 2 together (2-flowered scorpioid
cyme).--_Erodium_ (Stork’s-bill); inflorescence a many-flowered
unipared scorpioid cyme, stamens 5 + 0 (petal-stamens are wanting), and
fruit a schizocarp whose carpels become detached; their beaks are hairy
on the internal surface and _twist themselves spirally_ (Fig. 436).
The umbellate inflorescences are composed of multiflowered scorpioid
cymes. The leaves are often penninerved.--~The most primitive type is
represented by _Biebersteinia_: S5, P5, A5 + 5, G5 (ovaries _free_,
and styles united above); fruit 5 small nuts. The most advanced type
is _Pelargonium_, which has _zygomorphic_ flowers, the posterior sepal
being prolonged into a spur which becomes adnate to the peduncle;
the petals are unequal in size; some of the petal-stamens are often
wanting. (_Erodium_ may be slightly zygomorphic).~

  [Illustration: FIG. 434.--_Geranium sanguineum._ Fruit (3/1).]

  [Illustration: FIG. 435.--_Pelargonium._]

  [Illustration: FIG. 436.--_Erodium cicutarium_, detached carpel.]

   POLLINATION. The large-flowered _Geranium_-species are
   protandrous, _e.g. G. pratense_ (one whorl of stamens opens
   first, and then the other, and succeeding these the stigmas,
   after shedding the pollen the stamens bend outwards); the
   small-flowered are also adapted, with various modifications,
   for self-pollination.--470 species; moderately hot climates,
   especially S. Africa.--Several _Pelargonium_-species, with
   numerous varieties, are ornamental plants (from S. Africa).

Order 4. =Tropæolaceæ.= Herbaceous, juicy plants which have scattered,
long-stalked, peltate leaves without stipules, and often climb by their
sensitive petioles. The flowers are situated singly in the axils of the
foliage-leaves on long stalks, and are _zygomorphic_, the receptacle
under the posterior sepal being prolonged _into a spur_; there are also
differences between the posterior and anterior petals, the 2 posterior
petals situated on the border of the spur being _perigynous_, and the
edge of the anterior petals adjoining the claw fringed. After the 5
sepals (which are more or less coloured) and the 5 petals, follow 8
_stamens_ (as the 2 median ones are suppressed, one from each whorl)
and a gynœceum formed of 3 carpels; in each of the 3 loculi of the
3-grooved ovary is 1 ovule. The fruit is a _schizocarp_ and divides
into 3 1-seeded, _drupe-like_ fruitlets, which do not (as in the
Geraniaceæ) leave any pronounced column between them. Endosperm is
wanting. The cotyledons are thick and sometimes slightly coalescent.
~Tubers often occur.~

  [Illustration: FIG. 437.--Diagram of _Tropæolum_: _sp_, spur.]

_Tropæolum._--About 40 species; all from America.

   POLLINATION.--The spur is the receptacle for the nectar; the
   flowers are protandrous; the anthers open first, and one by
   one take up a position in front of the entrance to the spur,
   resuming their original position when the pollen is shed; the
   stigma finally takes their place after the filaments have bent
   backwards.--These plants have an acrid taste (hence the name
   “Nasturtium,” “Indian Cress”), on which account the flower-buds
   and young fruits of _T. majus_ are used as capers. Some species
   are ornamental plants.

Order 5. =Balsaminaceæ.= Herbaceous, chiefly annual plants with
juicy, brittle stems, so transparent that the vascular bundles may be
distinctly seen. The leaves are simple, usually scattered, penninerved
and dentate; stipules are wanting, but sometimes large glands are
present in their place at the base of the petioles. The flowers are
strongly zygomorphic; of their five 5-merous whorls the petal-stamens
are suppressed (S5, P5, A5 + 0, G5); the sepals are _coloured_, the
2 _anterior ones_ (Fig. 438 _3_, _5_) _are very small_ or entirely
suppressed, _the posterior one_ is very large and _elongated into a
spur_, and the 2 lateral ones pushed forward; sometimes the weight
of the spur turns the flower completely round, so that the posterior
leaves assume an anterior position; apparently only 3 petals, since
the lateral and the posterior petals become united in pairs, and
the anterior is larger and differently shaped; the 5 stamens have
very short and thick filaments united at the base, and their anthers
finally adhere together and remain in this condition, covering over
the gynœceum; the filaments ultimately rupture at the base, and the
entire anthers are raised on the apex of the gynœceum as it grows
up. The gynœceum has a _sessile stigma_ and a 5-locular ovary. The
fruit is a capsule which, on maturity, opens suddenly when irritated,
dividing into valves from the base upwards, and as the 5 valves roll
up elastically, the seeds are shot out on all sides to considerable
distances; a central column persists (Fig. 439). The embryo is
straight, and without endosperm.

  [Illustration: FIG. 438.--Diagram of _Impatiens glanduligera_.]

  [Illustration: FIG. 439.--Fruit of _Impatiens_.]

   _Impatiens_; in Europe only _I. noli-me-tangere_. 225 species;
   especially from Asia. Several species have two kinds of flowers:
   small, cleistogamic, but fertile; and large, coloured flowers,
   which in _I. balsamine_ (ornamental plant, E. Ind.) are
   protandrous and pollinated by hive-and humble-bees, as they suck
   the honey from the spur.

   Order 6. =Limnanthaceæ.= The flowers are regular and differ
   from all the other orders in the family by having the carpels
   not in front of the petals, but _in front of the sepals_
   (which are _valvate_), and further, the loculi are nearly
   _free individually_, but with a _common gynobasic_ style;
   the ovules are _ascending_ and _apotropous_ (anatropous with
   ventral raphe). The fruit is a schizocarp, with nut-like
   cocci.--_Limnanthes_ (4 species; N. Am.) perhaps belongs to
   another family.

   Order 7. =Humiriaceæ.= Trees and shrubs; about 20 species; Trop.
   Am.


                       Family 13. =Columniferæ.=

The chief characteristics of the orders belonging to this family are
the ☿, regular, generally 5-merous, _hypogynous_ flowers with 5-merous
_calyx_, sepals united and _valvate_ in the bud; petals 5, free (often
_twisted_ in the bud); stamens ∞ _e.g._: 10, in two whorls, but one of
these is more or less suppressed, often altogether wanting, or replaced
by 5 staminodes, while _the other_ (inner whorl) _is generally divided
more or less deeply_ into a large number of anther-bearing filaments.
The filaments too (except _Tiliaceæ_) are _united into a tube_, which,
especially in the _Malvaceæ_, forms a long column in the centre of
the flower, surrounding the gynœceum (Figs. 445, 448); in this case,
which is the most pronounced, the filaments are united into one bundle
(_monadelphous_), in other instances, _polyadelphous_. The number of
carpels varies greatly (2 to about 50), but they are nearly always
united and form a syncarpous multilocular gynœceum.--The vegetative
characters also closely agree, the leaves _are always scattered and
generally stipulate_; all the green portions very often bear _stellate
hairs_, and the bark in all the 3 orders is _rich in tough bast_.
Mucilage is often present in cells or passages.--This family is
connected with the _Ternstrœmiaceæ_, from which it is very hard to draw
a sharp line of demarcation, and it is also allied to the _Cistaceæ_
and to the _Gruinales_.

Order 1. =Sterculiaceæ= (including Buettneriaceæ). This is, no
doubt, the least modified order, and one in which the stamens occur
undivided. Obdiplostemonous. The 10 stamens in two whorls are most
frequently united at the base into a short tube, and have _4-locular,
extrorse_ anthers. The calyx-stamens are nearly always simple,
tooth-like staminodes, situated on the edge of the tube, or are
entirely suppressed. The same relation is found, for instance, in the
Ampelidaceæ and Rhamnaceæ, namely _5 stamens in front of the 5 petals_;
not infrequently the 5 stamens are doubled (Fig. 441). Unisexual
flowers are found in _Sterculia_, _Cola_, _Heritiera_. The corolla
is often wanting, or developed in an unusual manner. Each loculus of
the ovary (generally 5) always contains more than one ovule. Fruit a
capsule. Androgynophore often present (_Helicteres_; _Sterculia_, etc.).

   _Hermannia_, _Mahernia_, _Melochia_, etc., have flat petals
   with twisted æstivation; 5 undivided stamens, which usually
   are but slightly united at the base, and most frequently,
   without staminodes. _Thomasia_; _Helicteres_; _Sterculia_
   (free follicles).--_Theobroma_, _Rulingia_, _Buettneria_,
   _Commersonia_, _Guazuma_, etc., have petals concave at the
   base, and terminating in a limb abruptly bent back, and at the
   boundary between them most frequently ligular outgrowths, as in
   certain genera of the Caryophyllaceæ; stamens 5–15–∞, anthers
   at the edge of a short tube and 5 linear staminodes (Fig.
   441).--The Cocoa-tree (_Theobroma_), (Fig. 440) bears large,
   reddish-yellow, berry-like fruits, resembling short cucumbers,
   but ultimately becoming leathery to woody; in each of the 5
   loculi are 2 (apparently only 1) rows of horizontal, oily seeds,
   as large as almonds. Cotyledons large, thick, and irregularly
   folded. Endosperm absent (Fig. 442).

   49 genera, with about 750 species; almost entirely confined
   to the Tropics; none in Europe or in N. Asia.--The seeds
   of the Cocoa-tree (_T. cacao_, _bicolor_, _glaucum_, etc.,
   natives of Trop. Am., especially north of the Equator) are
   used for chocolate and are also _officinal_ (“Cocoa-beans,”
   “Cocoa-butter,” “Oil of Theobroma”). Theobromine. _Cola
   acuminata_, Africa.

  [Illustration: FIG. 440.--_Theobroma cacao._ Branch with flowers
  and fruits (⅙).]

  [Illustration: FIGS. 441–442.--_Theobroma cacao._

  FIG. 441.--Diagram of the flower: _st_ barren stamens.

  FIG. 442.--_B_ Seed in transverse section: _n_ hilum. _A_ Embryo
  after the removal of one of the cotyledons.]

Order 2. =Tiliaceæ.= This differs from the other orders of the
Columniferæ chiefly in the stamens being entirely _free_ from each
other, and also _divided_ into many filaments, _as far as the base_,
or at all events very far down, so that the _flower appears to have
numerous stamens_ or to be _slightly_ polyadelphous (Fig. 443); in
addition to this, it may be observed that the anthers are _4-locular_
and _introrse_. In _Luehea_ the groups of stamens alternate with the
petals. In a few genera (_Corchorus_, _Triumfetta_) 10 free and single
stamens are found in 2 whorls; but, in the majority, groups of free
stamens in separate bundles. The stamens are more or less united
in _Apeiba, Luehea_. Style simple. Ovary 2-locular. The ovules are
pendulous; raphe turned inwards. The calyx readily falls off; the
æstivation of the entirely free petals is slightly imbricate (_not
twisted_).

  [Illustration: FIG. 443.--Inflorescence of _Tilia_, with
  its winged bracteole (_h_); _a_, _a_ axis of the shoot; the
  vegetative bud is seen between the inflorescence and the axis of
  the shoot; _b_ petiole of foliage-leaf.]

_Tilia_ (Figs. 443, 444). Calyx and corolla 5-merous; the 5 staminal
leaves (opposite the petals) divided as far as the base into a large
number of stamens which are free or united into groups; gynœceum with
5 loculi in the ovary (opposite the sepals); there are 2 ovules in
each loculus, though the ovary ripens into a 1-seeded nut, which is
not detached from the axis of the inflorescence, but is carried away
by the wind, whirling round and round, its large-winged bracteole
serving as a parachute (Fig. 443).--~Only trees, with alternate,
obliquely heart-shaped and dentate leaves; stellate hairs, as in the
other Columniferæ, are often present. The terminal bud of the branch
always fails to develop, and the growth is then continued sympodially
by the uppermost axillary buds. The INFLORESCENCE (Figs. 443, 444) is
a 3–7-flowered dichasium (Fig. 444 _t_, _d_, _e_), which is developed
in the axil of a foliage-leaf (Fig. 444). The first of its 2 bracteoles
(_a_) is large, thin, leaf-like, and united with the inflorescence,
the lower portion of which forms a broad wing, its so-called “bract”;
the second bracteole (_b_), on the other hand, remains scale-like,
and supports a winter foliage-bud covered with bud-scales which thus
is situated at the base of the inflorescence, and is a bud of the
2nd order, in relation to the vegetative shoot. This bud is always
found beneath the inflorescence on the branch placed horizontally,
and the winged bracteole is always found above it, a relation which
is connected with the fact that the 2 rows of shoots on the sides
of a branch are _antidromous_ with regard to each other.--The
dichasium itself (Fig. 444) terminates with the flower (_t_); it has
3 floral-leaves (_c_, _d_, _e_), which soon fall off; _c_ is barren:
the other two bear flowers, or few-flowered dichasia, or unipared
scorpioid cymes (indicated in the figure).--The foliage-leaves are
folded in the bud upon the median line (1, 2, 3 in Fig. 444 are
foliage-leaves with their 2 stipules), the inner half is broader than
the outer, and after unfolding is turned away from the mother-axis (the
position of the new inflorescences and vegetative buds is indicated in
their axils on the figure).--The cotyledons on germination appear above
the ground as large, _lobed_ leaves.~

   Of the other genera some have a bell-shaped, gamosepalous
   calyx, some have no corolla, the anthers of some open at the
   apex (_Aristotelia_, _Elæocarpus_, etc.), the majority have
   a capsule, some have berries, or drupes, some separate into
   fruitlets, etc.--_Corchorus_, _Triumfetta_ (nut, with hooked
   bristles), _Luehea_, _Apeiba_, etc. _Sparmannia_ is an African
   genus; 4-merous flowers; fruit a warted capsule; filaments
   numerous and sensitive to touch, the external ones are without
   anthers and moniliform above. The plant is covered with numerous
   soft and stellate hairs, and at the apex of the branches bears
   several cymose umbels.

  [Illustration: FIG. 444.--Diagram of the inflorescence of _Tilia_
  and the vegetative bud; the position of the leaves is indicated,
  and also the position of the inflorescences, which develop from
  their axils in the following year.]

   POLLINATION in _Tilia_ is effected by insects, especially
   bees and Diptera, which swarm round the tree tops, allured
   by the numerous strongly-scented flowers and the easily
   accessible honey (formed in the hollow sepals). As the flowers
   are pendulous, the nectar is protected from ruin; and, in
   addition, the inflorescence is more or less concealed beneath
   the foliage-leaf. Self-pollination is impossible, on account of
   protandry.--About 470 species (nearly all trees and shrubs);
   especially in the Tropics, only a few being found in the
   temperate, none in the polar regions, or in high mountainous
   districts.--The inflorescence of the native species of _Tilia_
   is medicinal. The wood is used for charcoal.--The majority are
   used for timber, and for the sake of the bast (“Bast,” “Jute,”
   the bast of _Corchorus textilis_, _Luehea_, and others).

Order 3. =Malvaceæ= (=Mallows=). The plants are easily recognised by
the scattered, simple, _palminerved_, most frequently lobed, stipulate
_leaves_, folded in the bud; the perfect, regular, hypogynous flowers,
with _gamosepalous_, persistent, 5-merous calyx with _valvate_
æstivation; the 5 _petals twisted_ in the bud and united with one
another at the base, and by the 5 _apparently numerous stamens_ (Figs.
445, 448), with the filaments _united into a tube_, with _reniform
bilocular anthers_ opening by a crescentic slit (in 2 valves).
Carpels 3–∞ united into one gynœceum; the _embryo is curved and the
cotyledons are folded_ (Figs. 447, 451); endosperm scanty, often
mucilaginous.--Most of the plants belonging to this order are herbs,
often closely studded with _stellate hairs_. The leaves are most
frequently palmatifid or palmatisect.

  [Illustration: FIG. 445.--Longitudinal section through the flower
  of _Malva silvestris_.]

  [Illustration: FIG. 446.--Diagram of _Althæa rosea_: _i_ the
  epicalyx.]

   An _epicalyx_ is often found formed by _floral-leaves_ placed
   close beneath the calyx, in some 3, in others several. The
   median sepal is posterior in the species without epicalyx,
   often anterior in those which have an epicalyx.--The petals are
   _twisted either to the right or to the left_ in accordance with
   the spiral of the calyx; they are most frequently oblique, as
   in the other plants with twisted corollas, so that the portion
   covered in the æstivation is the most developed. The corolla
   drops off as a whole, united with the staminal tube.--Only
   the 5 petal-stamens are developed, but they are divided into
   a number of stamens, placed in 2 rows, and provided only with
   _half_-anthers (leaf-segments, see Fig. 446; the sepal-stamens
   are completely suppressed); these 5 staminal leaves are then
   united into a tube, frequently 5-dentate at the top, and
   bearing the anthers on its external side. The pollen-grains
   are specially large, spherical and spiny. There are from 3 to
   about 50 carpels united into one gynœceum and placed round the
   summit of the axis which most frequently projects between them.
   There is only 1 style, which is generally divided into as many
   stigma-bearing branches as there are carpels (Figs. 445, 448).
   The fruit is a schizocarp or capsule. Endosperm (Figs. 447 A,
   451) scanty, often mucilaginous round the _embryo_, which is
   rich in oil.

   The order is the most advanced type of Columniferæ; it stands
   especially near to the Sterculiaceæ, but is separated from these
   and from the Tiliaceæ, among other characters, by its 2-locular
   (ultimately 1-chambered) anthers.

The sub-orders may be arranged as follows:--

I. Carpels in one whorl.

=A.= =The fruit a capsule=, ~most frequently with loculicidal
dehiscence, and many seeds in each loculus~.

=1.= GOSSYPIEÆ. The staminal-column is naked at the apex, blunted, or
5-dentate.--_Gossypium_ (the Cotton plant) has an epicalyx of 3 large
ovate-cordate leaves, an almost entire, low and compressed calyx.
Solitary flowers. Large, most frequently yellow, corollas. A 3–5-valved
capsule with many spherical seeds. “Cotton” is the seed-hairs developed
upon the entire surface of the seeds (Fig. 447), and consists of long,
1-cellular hairs, filled with air (and therefore white); these are
thin-walled, with a large lumen, and during drying twist spirally,
and come together more or less in the form of bands. They consist
of cellulose, and have a cuticle.--_Hibiscus_ has several, most
frequently narrow, epicalyx-leaves, a distinct 5-toothed or 5-partite
calyx.--_Abutilon_; _Modiola_.

  [Illustration: FIG. 447.--_A_ Seed of _Gossypium_ with hairs; _B_
  the same in longitudinal section.]

   =2.= BOMBACEÆ. The staminal tube is more or less deeply cleft
   into bundles, sometimes almost to the base; pollen smooth,
   style simple with capitate, lobed stigma. Almost all plants
   belonging to this group are trees, and in many instances have
   large barrel-shaped stems, that is, swollen in the centre, and
   sometimes covered with large warts. The wood is exceptionally
   light and soft. The flowers are often enormously large, and have
   beautiful petals; in some they unfold before the leaves. The
   capsule-wall is sometimes closely covered on its inner service
   with long, silky, woolly hairs, while the seeds themselves
   are generally without hairs. These hairs, however, on account
   of their brittle nature, cannot be used like those of the
   Cotton-plant. Digitate leaves are found in the _Baobab-tree_
   (_Adansonia_) from Africa, noted for its enormously thick, but
   short stem, and in the American _Silk-cotton trees_ (_Bombax_,
   _Eriodendron_, _Chorisia_). _Ochroma_, _Cheirostemon_, _Durio_,
   and others also belong to this group. _Durio_ is noted for its
   delicious fruits, which have a most unpleasant smell.

   [_Bombax malabaricum_ is diplostemonous; the five sepal-stamens
   repeatedly branch, and the filaments bear unilocular anthers;
   the five petal-stamens bear bilocular anthers.]

=B.= =Schizocarps=, with 1-seeded fruitlets, most frequently nut-like
and reniform (Figs. 449, 451).

=3.= MALVEÆ, MALLOW GROUP. The carpels are arranged in one whorl
(Fig. 449); the number of stylar-branches equals that of the
carpels; fruitlets 1-seeded, reniform, indehiscent, but detaching
themselves from one another and from the persistent central column
(Figs. 450, 451).--~_Malva_ has an _epicalyx of 3 free leaves_. ~A
flower with 2 suppressed bracteoles is situated in the axil of the
foliage-leaves; one of these supports a homodromous foliage-shoot
which forms a repetition of the main axis, the other an antidromous
flower which continues the branching as a unipared scorpioid
cyme.~--_Althæa_, Rose Mallow, has an _epicalyx of 6–9 leaves united at
the base_.--~_Lavatera_, _Sida_, _Anoda_, _Bastardia_, etc., have no
epicalyx.~

  [Illustration: FIGS. 448–451.--_Malva silvestris._]

  [Illustration: FIG. 448.--The flower after removal of the
  perianth (5/1).]

  [Illustration: FIG. 449.--The fruit (5/1).]

  [Illustration: FIG. 450.--A fruitlet (5/1).]

  [Illustration: FIG. 451.--The same in longitudinal section.]

   =4.= URENEÆ, have always only 5 carpels arranged in 1 whorl,
   with 1 ovule in each loculus, and the fruit a schizocarp,
   generally with nut-like fruitlets provided with warts and
   hooks; but in some they dehisce by 2 valves (capsule). They
   differ principally from the other groups _in having twice as
   many stylar-branches as carpels_; the staminal tube is naked at
   the point, blunt or 5 toothed.--The genera _Urena_, _Pavonia_,
   _Malachra_, _Malvaviscus_ (with _berry-like fruits_) belong to
   this group.

II. Carpels arranged in a spherical head in five groups opposite to the
petals.

   =5.= MALOPEÆ, differ from all the others in having a large
   number of fruitlets arranged irregularly in a round head, and
   separating considerably from each other even before maturity;
   there is, however, only 1 style, divided into a corresponding
   number of branches (this condition may be considered to have
   arisen from the branching [dédoublement] of 5 _carpels_).
   _Malope_ has 3 large, heart-shaped (_Kitaibelia_ 6–9)
   epicalyx-leaves, united at the base. _Palava_ has no epicalyx.

   POLLINATION. The majority have protandrous flowers, and are
   pollinated by insects. Between the basal portions of the 5
   petals, there are 5 nectaries, protected from the rain by
   hairs, _e.g._ in _Malva silvestris_. When the flower first
   opens the numerous anthers occupy the centre of the flower, and
   the still undeveloped stigmas are concealed in the staminal
   tube; in the next stage the anthers are withered and empty,
   and the stigmas protrude and assume their places (Fig. 452).
   The large-flowered forms, it appears, are pollinated only by
   insects; but self-pollination takes place in small-flowered
   forms, as, for example, in _Malva rotundifolia_, in which the
   stylar-branches, twisting themselves, place the stigmas in
   between the undeveloped anthers.

  [Illustration: FIG. 452.--_Anoda hastata_: _a_ the bud just
  opened, the stigmas are concealed by the anthers; _b_ fully
  opened flower in ♂-stage; the upper stamens are developed first,
  and then the others in descending order; the stylar-branches
  are now visible, and lie bent back on the staminal column; _c_
  all the stamens project upwards, and all the anthers are open,
  but the stylar-branches are still bent back; d the anthers are
  emptied and the filaments shrunk together, but the styles have
  now straightened themselves upwards, and the stigmas are in the
  receptive condition.]

   DISTRIBUTION. 800 species (63 genera), most of which are
   natives of the Tropics, especially America. _Althæa_ and some
   of the species of _Malva_ are natives of the temperate regions
   of the Old World, the latter is also found in North America.
   _Gossypium_ is tropical, no doubt especially Asiatic (_G.
   herbaceum_ from India; _G. arboreum_ from Upper Egypt). Cotton
   was introduced into Greece in the time of Herodotus, and was
   cultivated in America before the arrival of the Europeans.

   USES. Pungent and poisonous properties are entirely wanting;
   _mucilage_, on the other hand, is found in abundance in all
   parts of the plant. Medicinal: the root of _Althæa officinalis_,
   leaves and flowers of _Malva_-species (_M. silvestris vulgaris_
   and _borealis_) and _Gossypium_.--The seeds contain a large
   quantity of _fatty oil_, which is in some cases extracted
   (Cotton-seeds and others). _The seed-hairs of the Cotton
   plant_ are the most important product of the order. The
   cultivated forms of Cotton belong to several species: _G.
   barbadense_, _herbaceum_, _religiosum_, _arboreum_ (Nankin),
   _hirsutum_, and others. According to other botanists, there
   are only 3 species. _Bast_ is obtained from _e.g. Hibiscus
   cannabinus_ (Gambo-hemp, Africa), _Paritium tiliaceum_ and
   _Sida retusa_. The fruits of certain species of _Hibiscus_
   (_e.g. H. esculentus_, from Tropical Africa) are used in
   tropical countries as a vegetable before they are ripe.--_The
   colouring matter_ in the flowers of _Althæa rosea_, var.
   _nigra_, is used for colouring wines, and hence is extensively
   cultivated in certain parts of Europe.--_Ethereal oils and
   sweet-scented flowers_ are rare; but several species possess
   a peculiar musk-like odour (_Malva moschata_, _Hibiscus
   abelmoschus_, and others).--Many are cultivated as _ornamental
   plants_ on account of the large flowers, _e.g._ Hollyhock (_A.
   rosea_, etc.), _Lavatera trimestris_, _Malope grandiflora_ and
   _trifida_, _Malva_-species, _Hibiscus rosa sinensis_, _syriaca_;
   _Sphæralcea_, etc.


                        Family 14. =Tricoccæ.=

The very large order _Euphorbiaceæ_ and three smaller ones belong to
this family. They have in common: _unisexual_, hypogynous, frequently
regular flowers, the perianth most frequently single, rarely double, or
entirely wanting; there is such a great variety in the structure and
parts of the flower that one only can be cited as the _rule_: viz. the
simple gynœceum composed of 3 carpels forming a 3-locular ovary, which
is frequently more or less deeply grooved (hence the name, _Tricoccæ_);
in the inner angles of the loculi are found 1 or 2 (never several)
pendulous (except _Empetraceæ_), anatropous ovules, with upward and
outwardly turned, frequently swollen, micropyle (Fig. 455). The seed
most frequently has a large endosperm and a straight embryo (Figs.
455 _B_, 464).--~The family approaches the nearest to the Gruinales
and Columniferæ; it may perhaps be regarded as an offshoot from the
Sterculiaceæ.~

Order 1. =Euphorbiaceæ.= Flowers unisexual. In each of the loculi of
the ovary, generally 3, there are 1 or 2 pendulous ovules with upward
and outwardly turned micropyle. The placenta protrudes above the ovules
(Figs. 454, 461 _B_). On the ripening of the capsule the 3 carpels
separate septicidally, frequently with great violence, ejecting the
seeds and leaving a central column. Endosperm copious.--For the rest,
the flowers present all stages, from genera with calyx and corolla,
to those which are the most reduced in Nature, namely the naked,
1-stamened flowers of _Euphorbia_.

The same variety which is found in the flower is also present in the
vegetative parts. Some are herbs, as our Spurges, others are shrubs
and trees; some African _Euphorbia_-species even resemble the habit
of a Cactus. Leaf-like branches with rudimentary leaves are found in
_Phyllanthus_ (sub-genus _Xylophylla_) (Fig. 456). The leaves are
scattered or opposite, often stipulate; they are nearly always simple.
Large, highly-branched cells containing a great quantity of pungent
latex are found in many, and watery juice in others. Glands and
glandular hairs are general.--Only a few genera can be considered in
this book.

As an example of the most perfect flowers (which partly reproduce
the Geraniaceous type) may be mentioned, _Croton_, _Manihot_, and
_Jatropha_; 5 sepals, 5 petals, sometimes gamopetalous, andrœcium
diplostemonous, or many-stamened, often monodelphous.

  [Illustration: FIGS. 453–455.--_Ricinus communis._

  FIG. 453.--♂-flower (magnified).

  FIG. 454.--♀-flower in longitudinal section.

  FIG. 455.--_A_ seed entire; _B_ in longitudinal section.]

_Ricinus_ (Castor-oil) (Figs. 453–455); monœcious; the ♂-flowers,
situated in the lower portion of the inflorescence, have 5
perianth-leaves and a large number of branched stamens; the ♀-flower
has 3–5 perianth-leaves; 3 bifid styles. Leaves peltate, palmately
lobed. The seeds (Fig. 455) contain an abundance of fatty oil and
large aleurone grains.--_Mercurialis_ (Mercury): the perianth is most
frequently 3-merous; in the ♂-flowers 9–12 stamens; in the ♀-flowers
most frequently a _2-locular_ gynœceum.--_Phyllanthus_: Pr3 + 3, A3,
united in some and forming a column in the centre of the flower (Figs.
457, 458); _Xylophylla_ is a section of this genus.-- _Hura crepitans_
(Sand-box tree) has a many-carpellate gynœceum, which separates with
great violence when ripe.--A drupe is found in _Hippomane mancinella_
(the Mancinil-tree, W. Ind.)--_Alchornea (Coelebogyne) ilicifolia_ is
well known on account of its “parthenogenesis”; only the ♀-plant has
been introduced into Europe, but it nevertheless produces seeds capable
of germination; these have generally several embryos.

  [Illustration: FIGS. 456–458.--_Phyllanthus (Xylophylla)
  angustifolius._

  FIG. 456.--Leaf-like branch with flowers (nat. size).

  FIG. 457.--♂-flower; and FIG. 458, ♀-flower (mag.).]

_Euphorbia_ (Spurge) has the most reduced flowers, which are borne
in a very complicated inflorescence. Each ♂-flower (Fig. 460 _B_) is
naked, and consists of one stamen only (terminal on the axis). In the
closely allied genus _Anthostema_, a small perianth is situated at
the place where, in _Euphorbia_, there is a joint in the “filament,”
(Fig. 461 _A_). The ♀-flowers (Fig. 460) are naked, with a 3-locular
ovary and 3 bifid styles. (_Anthostema_ has a distinct perianth (Fig.
461 _B_); in a few Euphorbias traces of a perianth are present).
In _Euphorbia_ the ♂-and ♀-flowers are grouped into flower-like
inflorescences termed “cyathia.” Each cyathium consists of a centrally
placed ♀-flower which is first developed, surrounded by 5 groups of
♂-flowers (stamens) placed in a zig-zag, with a centrifugal order
of development (Figs. 459, 460 _B_), that is, in unipared scorpioid
cymes; these flowers are surrounded by an _involucre_ of 5 leaves
united into a _bell-shaped structure_ (Fig. 459, 1–5) (resembling a
calyx); on its edge are placed 4, generally crescent-like, yellow
glands, one in each of the intervals, except one, between the lobes of
the involucre (shaded in Fig. 459; see also Fig. 460 _A_). Scale-like
thin structures (floral-leaves?) are situated between the ♂-flowers.
The ♀-flower has a long stalk, and finally bends down on one side,
namely to the place on the edge of the involucre where the gland is not
developed. These cyathia are again arranged in an inflorescence which
commences as a 3–5-rayed umbellate cyme (pleiochasium), the branches
of which ramify dichasially and finally as scorpioid cymes.--Latex,
with peculiar-shaped starch-grains, is found in laticiferous _cells_
(especially in the Cactus-like, leafless species.)

  [Illustration: FIG. 459.--Diagram of an inflorescence (cyathium)
  of _Euphorbia_ with 3 floral-leaves, _m_, _n_, _o_, supporting
  other cyathia which are subtended by 2 floral-leaves (bracteoles;
  _m_, _n_). 1–5, the involucral leaves in their order of
  development; the shaded portions are the crescentic glands.]

  [Illustration: FIG. 460.--_Euphorbia lathyris_: _A_ an (entire)
  inflorescence (cyathium); _B_ the same after the removal of the
  involucre.]

  [Illustration: FIG. 461.--_Anthostema_: ♂- (_A_) and ♀-(_B_)
  flowers; _p_ the perianth; _ar_ the node; _o_ the ovule.]

   205 genera; more than 3,000 species; especially in the
   Tropics.--Many are used on account of the oil, and of the
   pungent (aperient, poisonous, anthelmintic, etc.) properties in
   the latex or the seeds. OFFICINAL: “Cascarilla-bark” of _Croton
   eluteria_; the fatty oil of the seeds of _Croton tiglium_
   (Trop. Asia); “Castor oil” from _Ricinus communis_ (Africa,
   and cultivated in all warm climates throughout the world);
   the glandular hairs of _Mallotus philippinensis_ (“Kamala”);
   this also yields a red dye. Gum “Euphorbium” is the hardened
   (resinous) latex of the _Cactus_-like _Euphorbia resinifera_
   (Morocco).--NUTRITIVE plants: _Manihot utilissima_ and other
   species (Maniok, Am.). Their large, farinaceous roots form a
   very important article of food in the Tropics (Cassava-flour,
   Tapioca or Brazilian arrowroot). The fresh latex of the root in
   some species is a powerful poison; but the poisonous properties
   are diminished by roasting or cooking. _Caoutchouc_ is obtained
   from _Siphonia elastica_ (Trop. S. Am.). The vegetable
   tallow of the Chinese tallow-tree (_Stillingia sebifera_) is
   used in large quantities in soap factories. An indigo-like
   _dye_ is obtained from _Crozophora tinctoria_, and is also
   found in _Mercurialis perennis_. Shellac is obtained from
   _Aleurites laccifera_. ORNAMENTAL plants: _Acalypha_, _Croton_,
   _Dalechampia_.--_Hippomane_ is poisonous.

   Order 2. =Buxaceæ.= This order differs from the Euphorbiaceæ
   in having the micropyle turned inwards; the ♂-flower has a
   4-partite perianth and 4 stamens; the ♀-flower a 6-partite
   perianth and 3 carpels. Capsule with loculicidal dehiscence,
   the inner layer being detached elastically from the outer.--30
   species. Shrubs without latex and with evergreen leaves.--_Buxus
   sempervirens_ (Box) is an ornamental shrub (poisonous); it has a
   very hard and valuable wood which is used for wood-engraving and
   carving.

  [Illustration: FIGS. 462–464. _Callitriche stagnalis._

  FIG. 462.--♂-flower with the 2 bracteoles and the solitary stamen.

  FIG. 463.--♀-flower.

  FIG. 464.--Longitudinal section of the ripe fruit.]

   Order 3. =Callitrichaceæ.= Aquatic plants, growing at the bottom
   of shallow water, with opposite, simple, undivided, entire,
   exstipulate leaves, which are generally crowded and form a
   rosette in the apex of the branches. The flowers are unisexual
   (monœcious) and borne singly in the leaf-axils; they have no
   perianth, but are provided with two delicate bracteoles; the
   ♂-flowers consist of only _1 terminal stamen_ (Fig. 462);
   the ♀-flowers of a bicarpellate gynœceum (Fig. 463) which is
   originally 2-locular, but later on becomes 4-locular, as in the
   case of the gynœceum of the Labiatæ, by the formation of a false
   partition-wall; in each loculus there is 1 pendulous ovule with
   the micropyle turned outwards. Fruit a _4-partite schizocarp_
   (Fig. 464). 25 species.--_Callitriche._

   Order 4 (?). =Empetraceæ.= 4 species. _Empetrum_; _E. nigrum_
   (Crowberry) is a heather-like, moorland, evergreen undershrub
   with linear leaves, having a deep groove closed with hairs, on
   the under side. The _erect ovules_ show the greatest deviation
   from the Euphorbiaceæ. Diœcious (and ☿); S3, P3; in the
   ♂-flower, 3 stamens; in the ♀-flower, a 6–9-locular ovary. Fruit
   a _drupe_.


                      Family 15. =Terebinthinæ.=

The diagram of the flower (Figs. 465–467) is the same as in the
Gruinales, namely S, P, A2 and G in whorls of 5 (less frequently 3, 4,
6, 8), and the same modifications also occur with the suppression of
the petal-stamens, etc. But a _ring_ or sometimes _cup-like glandular
structure_ (_disc_) is found _between_ the andrœcium and the gynœceum
(Figs. 465, 466). The flowers similarly are regular, _hypogynous_, ☿
and polypetalous, though exceptions are found to all these characters:
thus, for example, united sepals and petals frequently occur, and,
in some orders, unisexual flowers by the suppression of one sex. In
most cases the flowers are small, greenish-yellow, and arranged in
paniculate inflorescences. The carpels (most frequently 5) are free in
a few, but generally united into a multilocular gynœceum; rarely more
than 1 or 2 ovules in each loculus. The gynœceum in the Anacardiaceæ
is so reduced that it has only 1 fertile loculus with 1 ovule.--The
_ovules are epitropous_, _i.e._ anatropous with outward-turned raphe
(except the Anacardiaceæ).--The majority of the species are trees
and shrubs with scattered, often _compound (pinnate) leaves_ without
stipules, and as in addition they frequently contain _aromatic,
especially turpentine-like substances_, they assume a certain
resemblance to the Walnut trees, and were formerly classed with them
mainly on this account. In a series of genera the volatile, scented
oils are found in special glands in the bark of the branches and in the
leaves, in the latter case appearing as _pellucid dots_. This family
includes several orders which are somewhat difficult to distinguish
from each other.

   Order 1. =Connaraceæ.= This order forms the connecting link
   between Terebinthinæ and Rosifloræ (_Spiræa_) as well as
   Leguminosæ, with which they are sometimes classed. The flowers
   have 5 5-merous whorls; 2 ovules in each loculus; micropyle
   turned upwards. Fruit a _follicle_, rarely a collection
   of follicles. Seed with aril. Shrubs with scattered (most
   frequently pinnate) leaves, without stipules. 170 species.
   Tropical.

   Order 2. =Meliaceæ.= Trees and shrubs with scattered, often
   pinnate leaves without pellucid dots and exstipulate; the
   leaflets are nearly always entire. Flowers small in paniculate
   inflorescences. Calyx and corolla 4–5-merous; 2 whorls of
   stamens; 3–5 carpels in the gynœceum. A very characteristic
   feature is the union of the filaments into a tube, on the
   edge of which stipule-like teeth are often found. There are
   most frequently 2 ovules in the loculi; fruit a capsule with
   many winged seeds in _Swietenia_ (Mahogany tree; Trop. Am.),
   _Cedrela_, etc.; berries in others. The wood of _Cedrela_ is
   used for making cigar boxes. 550 species; tropical.

Order 3. =Rutaceæ.= Leaves glandular with pellucid dots. The type
is the same as that of the family. Flowers 4–5-merous. The ovary is
most frequently 4–5-grooved. Disc well pronounced, often appearing as
a “gynophore.” The majority are shrubs with alternate or opposite,
compound, more rarely simple, leaves.

=A.= The ovary is deeply 2–5-cleft with basal styles which are more or
less united; the carpels in some genera are entirely free (groups 1,
2). The fruit is capsular and most frequently dehisces like follicles
along the ventral suture or septicidally, so that a horn-like internal
layer (endocarp) separates elastically from the external layer.

   =1.= ZANTHOXYLEÆ. _Zanthoxylum_; _Choisya_; _Evodia_.

   =2.= BORONIEÆ. Australia.--_Correa._

   =3.= DIOSMEÆ. Heather-like shrubs; Africa.--_Diosma_,
   _Coleonema_, _Empleurum_ and _Barosma_. OFFICINAL: _Barosma
   crenulata_ and _betulina_, “broad Buchu leaves” (_B.
   serratifolia_ and _Empleurum serrulatum_, “narrow Buchu-leaves”).

  [Illustration: FIG. 465.--_Ruta._ Flower (mag.).]

  [Illustration: FIG. 466.--_Ruta._ Longitudinal section of flower.]

  [Illustration: FIG. 467.--_Ruta._ Floral diagram.]

=4.= RUTEÆ. _Ruta_ (Figs. 465–467) _graveolens_ is an herbaceous,
glaucous, strongly smelling plant with bipinnate leaves and yellow
flowers; the terminal flower is 5-merous, the others 4-merous (S.
Eur.).--_Dictamnus_; zygomorphic flower. ~The individual carpels of the
fruit separate from each other, and dehisce like follicles, upon which
the internal layer is detached elastically and springs out, carrying
the seeds with it. Several species are ornamental plants.~

   =5.= CUSPARIEÆ. American. Flowers often zygomorphic with
   gamopetalous corolla; stamens 5.--_Ticorea_; _Galipea_ (_G.
   officinalis_; S. Am.; “Cortex angosturæ”); _Cusparia_;
   _Almeidea_.

=B.= The ovary is entire or only slightly grooved; the style is
terminal, undivided. The fruit is most frequently a drupe or berry.

   =6.= TODDALIEÆ. _Ptelea_; winged fruit. The buds are enclosed in
   the leaf-sheath. _Skimmia_; _Phellodendron_.

  [Illustration: FIGS. 468–470.--_Citrus vulgaris._

  FIG. 468.--Branch with compound leaves.

  FIG. 469.--Transverse section of fruit.

  FIG. 470.--Flowers (after the removal of the petals).]

=7.= AURANTIEÆ, ORANGE GROUP. Fruit a berry with a leathery external
layer.--The most typical flower is found for example in _Limonia_:
S5, P5, A5 + 5, G5 (2–5).--_Citrus_ has 4–5–8-merous flowers, a
gamosepalous, dentate calyx, free petals, one whorl of stamens which
are split irregularly into several bundles (Fig. 470). The fruit is a
_multilocular berry_ provided with a thick, tough, outer layer. The
juicy pulp, which fills up the loculi and envelopes the seeds, is
formed from many large-celled, juicy hair-structures which arise on the
inner side of the walls of the loculi and by degrees entirely fill them
up; the dissepiments remain thin, and form the partitions so easily
separating from each other (Fig. 469). The seeds in many instances are
remarkable for containing several embryos. The blade of the leaf is
separated from the frequently winged stalk by a _node_ (and hence is a
compound leaf with only the terminal leaflet developed?) (Fig. 468);
in other genera, as _Triphasia_, there is a fully developed trifoliate
leaf. Thorns are frequently developed.--~The species of this genus,
which is a native of the warmer parts of S. E. Asia, are very hard to
separate. The differences are found in the forms of the fruit, the
leaves and the leaf-stalks, and in the number of stamens. _Citrus
medica_, “Cedrat” (Ind.); _C. limonum_, “Citron,” “Lemon” (introduced
into Italy in the 3rd to 4th century). OFFICINAL: the fruits and
essential oil of Lemon. _C. aurantium_ from E. Asia, the Orange
(introduced into Italy in the 14th century). _C. vulgaris_ (Fig. 468),
Bitter Orange (introduced into Europe at the time of the Crusades);
the unripe Bitter Oranges, and peel of the Bitter Orange is officinal;
it is from the flowers of this species especially that the essence
of Neroli is made. _C. limetta_, _C. bergamia_, Bergamot; essence of
Bergamot is officinal. _C. decumana_, Pomalo, a native of the Islands
of the Pacific. About 780 species; chiefly tropical.~

   Order 4. =Burseraceæ.= Fruit a drupe; 1–5 stones. The bark,
   as well as the other parts, contain strong aromatic resins
   and balsams, and hence several species are used: the Myrrh
   tree, _Commiphora_ (_Balsamodendron_) from Arabia and Africa;
   OFFICINAL: Myrrha (_Commiphora myrrha_). Mecca-balsam from _C.
   opobalsamum_, Arabia; E. Africa. The Incense-tree (_Boswellia_)
   from the same parts of the globe and E. India. The incense of
   _B. carteri_ is medicinal (Frankincense). The resin (Elemi) of
   _Protium_-species is officinal, and is used technically for
   varnish (S. Am.). Takamahaka-resin from _Elaphrium_ (S. Am.)
   _Protium_ (_Icica_); _Amyris_ (1 carpel). 270 species; tropical.

   Order 5. =Zygophyllaceæ.= The majority have opposite, pinnate
   leaves with stipules. _Leaves without pellucid dots._ The
   filaments have a scale on the inner side. The most important is
   _Guaiacum officinale_ (West India), the wood (Lignum Vitæ) of
   which is very hard and heavy, this wood and Gum-guaiacum are
   officinal. Others have a peculiar repulsive smell and taste: the
   Creosote shrub (_Larrea mexicana_) and _Zygophyllum simplex_.
   _Tribulus terrester_ is a common weed in S. Europe. _Fagonia._
   _Peganum harmala_ (South of Russia) yields a red dye.--110
   species; especially in the Tropics; several species in sandy
   deserts. _Nitraria._

   Order 6. =Simarubaceæ.= This order is distinguished by the
   abundance of _bitter_ substances which it contains (Quassine)
   especially in the bark and the wood. The wood of _Quassia amara_
   (Guiana, Antilles) is officinal; _Picraena excelsa_ yields
   Jamaica Quassia; the bark of _Simaruba_, _Simaba_-species
   and others is used. _Ailanthus glandulosa_ is a garden plant
   (pinnate leaves, winged fruit).--110 species. Tropical.

   Order 7. =Ochnaceæ.= Flowers diplostemonous, 5-merous. The
   unilocular ovaries, which are individually free, project
   considerably into the air around the gynobasic style; 1 ovule
   in each loculus; the fruitlets are drupes. Shrubs; leaves
   alternate, with stipules. _Ochna_; _Ouratea_.--160 species;
   tropical; especially American.

   Order 8. =Anacardiaceæ.= The ovary rarely contains more than 1
   ovule, even though there be several loculi and several carpels;
   in _Anacardium_ all the 10 stamens except one become suppressed.
   Resin passages.--_Anacardium._ The most peculiar feature is the
   development of the flower-stalk into a fleshy body about the
   form and size of a pear (_A. occidentale_ from Trop. Am. and
   _A. orientale_ from E. Ind.) which bears the kidney-shaped nut
   (the so-called “Cashew-nut”) on its apex. _Mangifera indica_
   (the Mango-tree, from E. Ind.) is cultivated in several tropical
   countries on account of its delicious drupe. Similarly, species
   of _Spondias_ (_S. dulcis_, Pacific Islands, _S. lutea_).
   Several species of _Rhus_ are ornamental shrubs in this country,
   for instance, _R. typhina_ (N. Am.), _R. cotinus_ (the Wig-tree,
   the _barren_ flower-stalks of the panicles being feather-like
   and hairy); _R. toxicodendron_ (Poisonous Sumach, from N. Am.)
   is poisonous. Chinese galls are produced by the sting of a
   leaf-louse (_Aphis chinensis_) on _R. semialata_ (China), and
   Japanese wax is from the seeds of _R. succedanea_ (Japan).
   Considerable quantities of Sumach (_R. coriaria_) are used in
   tanning and as a black dye. OFFICINAL: the mastic resin of
   _Pistacia lentiscus_ (the Mastic-tree, from the Mediterranean).
   The fruits of _Pistacia vera_ (Syria) are edible; _P.
   terebinthus_ and others yield turpentine.--450 species; tropical.

   Order 9. =Icacinaceæ.= Flowers 4–5-merous; haplostemonous;
   receptacle convex or cup-like surrounding the gynœceum; in
   the (single) loculus of the ovary, 2 anatropous, pendulous
   ovules.--200 species; tropical.

                        Family 16. =Aesculinæ.=

The essential characters of this family are in the main the same as
those of the Terebinthinæ and Gruinales. The flowers are hypogynous,
perfect, with free petals, 5-merous (S5, P5, typically A5 + 5, all
of which, however, are not generally developed; in our native orders
there are only 7–8 stamens), and most frequently a _3-merous, 3-locular
gynœceum_ (less frequently 2 or 5 carpels with as many loculi). In
each loculus there are usually only 1–2 ovules. A deviation from the
preceding families is the frequent _zygomorphy_ of the flower, with,
as a rule an _oblique_ plane of symmetry (Fig. 471). When a _disc_ is
developed it is placed _outside_ the stamens. The majority have no
endosperm (Fig. 473).--The members of the family are nearly all trees.

   The family is closely allied to the Terebinthinæ, but unlike
   this it never has aromatic properties, and differs also
   in the position of the nectary, in the flowers, which are
   often irregular with a reduction in the number of stamens,
   and in the ovule which is usually ascending with micropyle
   pointing downwards (the Terebinthinæ having the micropyle
   turned upwards), etc. It is also related to Frangulinæ, the
   Staphyleaceæ being the chief connecting link; but the Æsculinæ
   generally have compound leaves.

   Order 1. =Staphyleaceæ.= Leaves opposite, often compound.
   Flowers regular, ☿, 5-merous in calyx and corolla, 5-stamened.
   The stamens are placed _outside_ the nectary. Ovary syncarpous
   or 2–3-partite with free styles. The capsule is thin,
   bladder-like, 2–3-locular, opening at the apex, and has several
   very hard seeds with a shining testa without aril. Endosperm.
   _Staphylea pinnata_ (S. Europe) and _trifoliata_ (N. Am.) are
   cultivated in gardens; they have white flowers in pendulous,
   axillary racemes or panicles.--16 species.--_Staphylea_ is found
   in the Tertiary of N. America.

   Order 2. =Melianthaceæ.= Glaucous shrubs with scattered, pinnate
   leaves, and large stipules. _Melianthus._--8 species; S. Africa.

Order 3. =Sapindaceæ.= Trees or shrubs, often climbing by tendrils
(lianes with anomalous structure of the stem) and with compound leaves.
The flowers, in most cases, are small, insignificant, and without
scent, and in some polygamous and zygomorphic. S4–5, P4–5, A8 (less
frequently 5–10) inside the nectary (disc); ovary generally 3-locular,
with 1–2 ovules in each loculus (raphe ventral, micropyle turned
downwards). Seed without endosperm, often with an aril. The embryo is
often thick and curved (Fig. 473).

  [Illustration: FIGS. 471–473.--_Æsculus hippocastanum._

  FIG. 471.--Diagram of the flower and of a scorpioid cyme.

  FIG. 472.--Flower in longitudinal section.

  FIG. 473.--Seed in longitudinal section.]

_Æsculus_ (Horse-Chestnut). Trees with opposite, digitate, dentate
leaves without stipules; the inflorescence is composed of unipared
scorpioid cymes arranged in a pyramidal panicle (termed a thyrsus). The
flowers are irregular, with an _oblique plane of symmetry_ (through the
4th sepal, Fig. 471); there are 5 sepals, 5 free petals, of which the
one lying between S^3 and S^5 is the smallest (see Fig. 471) and may
be absent; stamens 7 (5 + 2), three being suppressed; gynœceum simple,
3-carpellary and 3-locular, with single style; of the two ovules one is
ascending, the other descending (Fig. 472).--The fruit is a 3-valvate,
sometimes spiny, capsule, with loculicidal dehiscence, the seed having
a large hilum, a curved embryo without endosperm and united cotyledons
(the radicle lies in a fold of the testa, Fig. 473). _Æ. hippocastanum_
(Greece, Asia), introduced into cultivation about 300 years ago;
the majority of the other species, _e.g. Æ. pavia_, etc., several
of which are frequently cultivated in gardens, are from N. America.
~The flower of the Horse-Chestnut is adapted for bees, whose abdomen
touches the anthers or style when visiting the flower. The flowers are
protogynous.~

   The other Sapindaceæ have most frequently 4 sepals, 8 stamens,
   various fruits (septicidal capsule, nuts with or without wings,
   schizocarp), etc. _Serjania_, _Cardiospermum_, _Sapindus_,
   _Koelreuteria_, etc. (about 118 genera, 970 species). The seeds
   of _Paullinia sorbilis_ contain caffeine, and are used as “Pasta
   guaranà,” in the North Western Brazils in the manufacture of a
   common drink. _Nephelium_ (or _Euphoria_) _litchi_ (with edible
   aril), and other species, from Asia.

  [Illustration: FIG. 474.--Samara of _Acer platanoides_.]

Order 4. =Aceraceæ.= This order is so closely allied to the Sapindaceæ,
that some authorities have classed it with them. The main difference
is in the _regularity_ of the flowers, and the =2=-merous gynœceum
(in abnormal cases several carpels occur).--They are trees, and, like
the Horse-Chestnuts, have opposite leaves without stipules; in _Acer_
the leaves are palminerved, but imparipinnate in _Negundo_, a plant
frequently cultivated in gardens. The flowers are often unisexual,
polygamous (some species have ☿-, ♂-and ♀-flowers); sepals 5, petals
5 free, =stamens 8= (that is, 5 + 5, but the two median ones are
absent) inside a large disc. Fruit a samara (schizocarp) with 2
_winged, nut-like_ fruitlets (Fig. 474). In each of the 2 loculi of the
ovary are 2 ovules. Embryo _curved_, with thin, _folded_ cotyledons.
Endosperm absent.--~The inflorescences are racemes with a more or
less elongated main axis and terminal flower (which sometimes has 10
stamens); when the lateral branches are developed they are similar
to the main axis. In some species both corolla and petal-stamens are
suppressed. _Acer_ is pollinated by insects, _Negundo_ by the wind.--88
species; North Temperate zone. _Acer_ in the Tertiary from the
Oligocene. The following are native plants: Maple (_Acer campestre_),
Sycamore (_A. pseudoplatanus_, doubtful native). Important as avenue
trees and timber. Sugar is obtained from the spring sap of the Sugar
Maple (N. Am.).~

   Order 5. =Malpighiaceæ.= A tropical (especially American) order
   closely related to the Aceraceæ, having often the same form of
   fruit (but 3-partite). Some species are lianes with anomalous
   stem-structure. Leaves opposite. The flowers are regular or
   obliquely zygomorphic (the plane of symmetry passing through
   sepal 3), with S5, P5, A5 + 5, G3; 1 pendulous ovule in each
   loculus. Important characteristics for identification are the
   numerous grandular structures on the sepals. Peculiar 2-spined
   hairs are found in some. _Malpighia_, _Bunchosia_, _Galphimia_,
   _Tetrapterys_, _Heteropterys_, etc.--About 600 species.

   Order 6. =Erythroxylaceæ.= Sepals 5, petals 5 (with a ligular
   corona), 10 stamens in one bundle. Gynœceum 3-locular. Fruit
   a drupe. Tropical (especially American) trees and shrubs, the
   _Coca-plant_ (_Erythroxylon coca_) being best known. Its leaves
   are considered by the inhabitants of Chile and Peru to be one
   of the indispensable necessaries of life; they are chewed, and
   possess intoxicating, exhilarating properties, and contain
   the alkaloid cocaine, which is frequently employed as a local
   anæsthetic.--103 species; chiefly in America.

   Order 7. =Vochysiaceæ.= Trees; Trop. Am. 1 stamen.--140 species.

   Order 8. =Trigoniaceæ.= Shrubs; Trop. Am.--30 species.

   Order 9. =Tremandraceæ.= Polygalaceæ with regular flowers.--27
   species. Australia.

  [Illustration: FIG. 475.--Diagram of _Polygala_: _d_ a gland
  in the posterior side of the flower; α and β the two caducous
  bracteoles.]

Order 10. =Polygalaceæ.= Herbs or shrubs (some tropical species are
lianes) with scattered (rarely opposite), simple and most frequently
quite entire leaves, without stipules. The flowers are usually borne in
terminal spikes or racemes, and are strongly zygomorphic (_the plane
of symmetry being median_); they have 5 free sepals, the 2 _lateral
ones_ of which (4 and 5 in Figs. 475, 476) are very large, _petaloid_,
and frequently project on each side like the “wings” of a Pea-flower;
petals 5, of which the two lateral ones are wanting or rudimentary
(dotted on Fig. 475), and the _anterior_ “the _keel_” (Fig. 476 _c_)
is large, hollow and boat-shaped, and frequently with a lobed or
fimbriated edge (Fig. 476 _A_ and _B_, _c_); stamens 8, the two median
ones being absent, all _united_ into a tube split along the back, which
is also slightly united to the keel (the anthers, often 2 locular,
_open by pores_, Fig. 476 _B_, _st_); the 2 median carpels form a
bilocular ovary. 1 pendulous ovule in each loculus (Figs. 476 _C_,
475); capsule compressed with loculicidal dehiscence, rarely a nut.
_Polygala_ (Milk-wort).

   470 species; distributed over the whole globe (none Arctic).
   OFFICINAL: the root of _P. senega_, from N. Am. Some are used as
   ornamental plants.

   POLLINATION. The flowers of _Polygala_ are pollinated by insects
   (chiefly bees). The fimbriated processes of the anterior petal
   support the insect when it alights. The anthers lie on each
   side of the stigma in the pouch of the anterior petal; the apex
   of the style is spoon-shaped, and immediately behind it is a
   viscid stigmatic lobe. In reaching the honey the proboscis of
   the insect must come in contact with the pollen and the viscid
   stigma, by which it is rendered sticky; this ensures the pollen
   adhering to the proboscis and so being carried to other flowers.

  [Illustration: FIG. 476.--_Polygala amara._ Parts of the flower
  (mag.) _A_ Flower from side, 1-5 sepals: _c_ keel; _B_ flower
  from above spread out: _st_ the 8 stamens; _c_ fimbriated edge of
  “keel”; _C_ ovary with style and stigma.]


                       Family 17. =Frangulinæ.=

The plants belonging to this family, with very few exceptions, are
trees or shrubs. The leaves are usually simple; stipules may be
absent or present. The flowers in almost all the orders are _small,
green or whitish_; they are _always regular_, 4-_or_ 5-_merous_ with
2–5 _carpels_, but never have more than 1 _whorl of stamens_, which
in _Rhamnaceæ_ and _Ampelidaceæ_ are placed _opposite_ the petals
(typically 5 + 5 or 4 + 4 stamens, of which however either the
external or internal whorl is always wanting); hypogynous or slightly
perigynous, in _Rhamnaceæ_ only strongly perigynous or epigynous;
generally ☿; the calyx is inconspicuous; petals free or slightly
united. Gynœceum simple; _ovary generally multilocular_; style short or
entirely wanting. A _disc_ is nearly always developed in the flower,
but is found sometimes inside the staminal whorl, sometimes outside
it or between the stamens. The ovules are apotropous (anatropous with
dorsal or ventral raphe).

Order 1. =Celastraceæ.= _Euonymus europæa_ (Spindle-tree) may be
chosen as a type. It is a shrub with simple, opposite leaves and
small caducous stipules. The small, greenish-yellow flowers, borne
in regularly-branched dichasia, are regular, ☿, with 4 whorls, 4-(or
5-) merous in regular alternation. There is a _thick disc_ upon which
the polypetalous corolla (imbricate in the bud) and the stamens are
borne, with a slightly perigynous insertion. The style is short and
thick; the ovary has 2 _erect_ ovules in each loculus. The fruit is
a red, 4-valvate capsule with loculicidal dehiscence; the seeds are
few in number, and have a large, red-yellow _aril_ (developed from
the micropyle). Embryo green, in a large, fleshy, white endosperm.
~The dingy yellow flowers are generally visited only by flies and ants
for the sake of the honey secreted by the disc, and while they run
about on the flowers they touch the anthers and stigmas, now with one
part of the body, now with another. The flower is protandrous. The
stigmas are not developed till several days after the opening of the
anthers.--_Celastrus_, _Cassine_, _Catha_, etc.~

   38 genera; 300 species. Distributed over the entire globe, with
   the exception of the colder districts, and especially in the
   Tropics. Some are ornamental bushes (_Euonymus japonica_). The
   leaves of _Catha edulis_ are used by the Arabs and Abyssinians
   in the same way as those of _Coca_ by the Peruvians.

   Order 2. =Hippocrateaceæ.= 150 species; tropical; chiefly
   lianes. S5, P5, A3, G3. Anthers extrorse.

  [Illustration: FIG. 477.--_Ilex aquifolium_: magnified flower.]

Order 3. =Aquifoliaceæ (Hollies).= The genus _Ilex_ forms almost the
entire order. (175 species out of 180; especially from S. Am.) They
are shrubs or trees with scattered, leathery, simple leaves (in _Ilex
aquifolium_, spiny) with very small stipules. The flowers are small,
white, and borne in few-flowered inflorescences in the axils of the
foliage-leaves; they are most frequently unisexual and diœcious. There
are 4–5 sepals, petals, stamens and carpels in regular alternation;
the calyx and _corolla_ have their leaves _slightly_ connate; stamens
slightly adnate to the corolla; the ovary is generally almost spherical
with a thick, sessile stigma (Fig. 477). This order deviates especially
from _Celastraceæ_ in the _absence of the disc_ and in having only
1 (_pendulous_) ovule in each of the 4 loculi of the ovary, and in
having a _drupe_ with generally 4 stones. Embryo extremely small, at
the apex of the large endosperm, with the radicle directed upwards.--~3
genera.--_I. aquifolium_ (Holly) principally on the coasts of European
countries; from Norway to W. Denmark, and further westward. It is a
common garden shrub with stiff, shining leaves and red fruits. Several
South American species contain so much _caffeine_ that they may be used
as a beverage in the place of tea (_I. paraguayensis_, Paraguay tea, or
Maté). The Holly does not contain caffeine.~

Order 4. =Ampelidaceæ (Vines).= Shrubs with the stem swollen at the
insertion of the petioles and climbing by _tendrils borne opposite
the leaves_ (Figs. 478, 479). The leaves are scattered (generally
1/2), stalked, stipulate, frequently palminerved and lobed, divided or
compound. The small, greenish flowers are generally borne in paniculate
_inflorescences, whose position is the same as that of the tendrils_
(Fig. 478); they are hypogynous or slightly perigynous, ☿, with 4–5
sepals, petals, stamens (which, as in the Rhamneæ, are _opposite the
petals_; Fig. 480 _A_, _B_) and 2 carpels. The calyx is very small,
entire, or slightly dentate; corolla _valvate_, and in some falling off
as a hood, since the individual parts remain united at the summit (Fig.
480 _A_). Between the stamens and gynœceum is situated an hypogynous
_disc_, with 5 lobes alternating with the stamens (Fig. 480 _A_, _B_,
_E_). In each loculus of the 2-locular ovary there are 2 _erect_
ovules (_E_); the style is short or wanting. The fruit is a _berry_.
The embryo is small and lies in a horny, sometimes slightly folded
(ruminate) endosperm (Fig. 480 _C_, _D_).

  [Illustration: FIGS. 478–481.--_Vitis vinifera._

  FIG. 478.--Branch with bunch of grapes.

  FIG. 479.--Diagram of the position of leaf and tendrils. The
  branch is divided into sections on the sympodial theory (the
  successive generations, I, II, III, IV, are alternately white and
  shaded); _k_ buds.

  FIG. 480.--A Flower throwing off the corolla; _B_ flower after
  the removal of the corolla; _C_, _D_ longitudinal and transverse
  section of seed; _E_ longitudinal section of gynœceum; _s_ calyx.

  FIG. 481.--Diagram of branch and position of leaves; _sl_
  tendril; _lt_ the main axis; _ax_ stipules of the foliage-leaf
  shown below; _g_ axillary-bud (the dwarf-branch); _v_ its
  fore-leaf; _l_{1} l_{2}_ its first two foliage-leaves with
  their stipules; _lt_{1}_ long-branch in the axil of _v_
  (everything appertaining to this branch is entirely black);
  _v_{1}_ the first leaf of this branch.]

   _Vitis_ and _Ampelopsis_ (5-merous flowers); _Cissus_ (4-merous
   flower); _Leea_ (without stipules, corolla gamopetalous). The
   inflorescence in _Pterisanthes_ (E. Ind.) has a peculiar, flat,
   leaf-like axis, on the edges of which ♂-flowers are borne, and
   on the surface ♀-flowers.

   The TENDRILS in Ampelidaceæ are modified branches, since they
   bear leaves and may be abnormally developed as branches with
   foliage-leaves, and finally the inflorescences are borne in
   the position of the tendrils, and tendrils are met with which
   are partly inflorescences. The explanation of the position
   of the tendril, namely, right opposite the foliage-leaf but
   without a subtending-leaf, has been much disputed. The relative
   positions are as follows: in _Vitis vinifera_ the following
   two kinds of shoots and relative positions are found (the
   other species deviate in one or other particular), (_a_)
   LONG-BRANCHES, which have 2 scale-leaves and a large number of
   foliage-leaves with a divergence of 1/2; opposite the lowest
   3–5 foliage-leaves no tendrils are found, then follow: 2
   foliage-leaves with tendrils, 1 without a tendril, 2 with and
   1 without, etc., with great regularity. Buds are developed in
   the axils of the foliage-leaves (Fig. 479): these develop into
   (_b_) DWARF-BRANCHES, which commence with 1 laterally-placed
   scale-leaf (fore-leaf; Fig. 481 _v_) succeeded by several
   foliage-leaves with a divergence of 1/2 (in a plane at right
   angles to that of the mother-shoot), but the whole shoot is
   extremely small, and often dries up and drops off in the
   autumn, so that only the scale-leaf, _v_, with the bud (Fig.
   481 _lt_{1}_) in its axil remains. This bud in the following
   year developes into a new long-branch, and since its leaves
   lie in a plane at right angles to that of the dwarf-branch,
   their plane coincides with that of the long-branch from which
   it is developed (the grandmother axis).--The tendrils no doubt
   may most correctly be regarded as the modified main axis which
   has been pushed aside by a lateral branch. The branches are
   then sympodia, whose successive shoots bear alternately 1
   and 2 foliage-leaves: thus, on the figure there are portions
   altogether of 5 shoots (I.-V.), the 1-leaved ones are shaded,
   the 2-leaved ones are white. The following facts however are
   adverse to this theory: (1) the first leaf on an axillary bud
   is then situated 180° from the subtending leaf (_e.g._ the
   lowermost shaded leaf, Fig. 479, 180° from the lowermost white
   leaf), whilst the rule in the Dicotyledons is that it is placed
   only about 90° to one side. (2) The buds (Fig. 479 _K_) from
   which the dwarf-branches develop, must then be accessory and
   sister-buds to the sympodial shoots, but their first leaves have
   a different relative position to this, which is very peculiar,
   and a still more remarkable fact is that the buds, _K_, etc. are
   similar in structure and present in _all the axils_; thus we
   _only_ find accessory buds in the cases where no tendrils are
   opposite to the leaves, and the main bud must then be considered
   to be suppressed. (3) The development proves that the tendrils
   arise on the side of a vigorous growing-point of the stem or by
   its division, and do not develop, as might be expected, from
   the apex of the shoot. But these relations however, find their
   analogues and are all capable of explanation, whereas other less
   natural modes of explanation are opposed to them.

   435 species; especially in the Tropics; they are rarer in
   America. In N. Am. some _Vitis_-species and _Ampelopsis
   quinquefolia_ are found. _Vitis vinifera_ is supposed to have
   originated in the districts East and South of the Caspian Sea.
   Wine is obtained from _Vitis_-species, especially _V. vinifera_,
   and “raisins,”--(the name “currants,” given to a special variety
   with small, seedless fruits, is derived from Corinth).--The
   species of _Ampelopsis_ (Virginian Creeper) are cultivated as
   ornamental plants.

Order 5. =Rhamnaceæ.= _The stamens are placed opposite the petals_
as in the Ampelidaceæ (Fig. 482), but the flowers are _much more
perigynous or entirely epigynous_. The trees and shrubs belonging
to this order have simple, most frequently penninerved leaves with
stipules; frequently thorny (modified branches). The flowers are
inconspicuous, sometimes unisexual (Fig. 482), and have 5 (-4) sepals,
petals, stamens, and generally 3 (2–5) carpels. The calyx has _valvate_
æstivation. The petals are very _small_ (generally less than the
sepals), often spoon-like, hollow, and embracing the stamens; _a disc
covers the inner surface of the thalamus_ or the base of the style in
the epigynous flower; gynœceum simple, with one style and one _erect
ovule in each loculus_. The fruit is most frequently a _drupe_. The
embryo is large, often green or yellow, with endosperm.

_Rhamnus_ (Buckthorn) has a juicy drupe with 3 (2–4) stones, surrounded
at the base by the persistent portion of the receptacle; the disc is
thin. _R. cathartica_ (common Buckthorn): diœcious, with opposite,
serrate leaves. _R. frangula_ (Alder Buckthorn): flowers ☿, with
scattered, entire leaves.--~_Ceanothus_ (N. Am., with richly-flowered
inflorescences and a fruit closely resembling that of the Euphorbias).
_Phylica_, _Pomaderris_ (Austr., fruit a capsule). _Zizyphus_,
_Paliurus_, _Colletia_ (S. Am.) are thorny shrubs; _C. spinosa_ has
thorny shoots with small, caducous leaves; the seedling has normal
foliage-leaves. Others climb by tendrils as in the Ampelidaceæ, _e.g._
_Gouania_.~

  [Illustration: FIG. 482.--_Rhamnus cathartica_: _A_ long-styled
  ♂-flower; _pet_ petals; _B_ short-styled ♂-flower; _C_
  long-styled ♀-flower; _D_ short-styled ♀-flower (after Darwin).]

   475 species, 40 genera; chiefly in temperate and tropical
   climes. Some are medicinal plants, the bark and fruit
   having purgative properties (the bark of _Rhamnus frangula_
   and “Cascara Sagrada” from the bark of _R. purshiana_ are
   officinal). The fruits and seeds of others are edible, for
   example, the fruits of _Zizyphus lotus_, _Z. vulgaris_, _Z.
   spina Christi_, etc. Green and yellow _dyes_ are obtained from
   the fruit of _R. cathartica_, _infectoria_ and others (Avignon
   grain). _Ceanothus-_, _Rhamnus-_ and evergreen _Phylica_-species
   are ornamental shrubs.


                       Family 18. =Thymelæinæ.=

Exclusively trees or shrubs with simple, entire, scattered leaves
without stipules. They have a _strongly perigynous_, regular,
_4-merous_ flower. The receptacle (often coloured) envelopes a simple
gynœceum formed of =1= _carpel_ and with, in most cases, =1= ovule,
bearing on its edge 4 (or 5) petaloid sepals and, but rarely at the
same time, small, scale-like petals. The corolla is most frequently
entirely wanting (and hence these plants were formerly reckoned among
the Monochlamydeæ); frequently only one of the 2 whorls of stamens,
which are situated on the inner side of the edge of the receptacle, is
developed. The fruit is most frequently a _1-seeded_ berry or drupe, or
a nut which may be falsely berry-like, the partly persistent receptacle
being fleshy and enveloping it.

   This family appears the most nearly allied to the Frangulinæ,
   especially the Rhamnaceæ, and may be considered as a further
   development of these in the direction of the petaloid
   development of the receptacle and reduction of the corolla and
   gynœceum, which in this instance only consists of one carpel.
   Another deviation is that both the whorls of stamens are
   present, while one of these is always wanting in Frangulinæ.
   They also appear to be related to the Lauraceæ (see page 391).

Order 1. =Thymelæaceæ.= The flowers are most frequently ☿ (Fig. 483).
The receptacle is high, generally tubular, coloured, and bears on its
edge the 4-(or 5)-merous calyx, with imbricate æstivation. The corolla
is wanting or is represented by small scales. The stamens are situated
on the inside of the receptacle, and number 4 + 4 (or 5 + 5); stigma
capitate. 1 _pendulous ovule_ (Fig. 483 _B_), the _radicle pointing
upwards_. The fruit is most frequently a berry. ~A disc is sometimes
developed. Endosperm wanting or very slight.~

  [Illustration: FIG. 483.--_Daphne mezereum_: _A_ flower; _B_
  longitudinal section of pistil.]

_Daphne_ (Spurge-Laurel, Fig. 483) has a deciduous receptacle, often
coloured; sepals 4; petals absent; stamens 4 + 4. Berry.--_Gnidia_
(corolla); _Pimelea_ (2 stamens); _Thymelæa_; _Passerina_ and others.

   400 species; chiefly in the warm, sub-tropical zone, especially
   the Cape and Australia. Only _Daphne_ and _Thymelæa_ in
   Europe. In the fruit and bark of some, for example _Daphne_,
   pungent, burning and poisonous properties are found. The bark
   of _D. mezereum_ (native and cultivated) and _D. laureola_ is
   officinal. A specially tough bast is found in some species, for
   example _Lagetta lintearia_ (Lace-tree, Jamaica), which is used
   in weaving. Some are cultivated in gardens as ornamental shrubs,
   especially species of _Daphne_.

Order 2. =Elæagnaceæ.= Shrubs or trees, which are easily recognised
by the covering of _peltate hairs_ found upon almost all parts of the
plant, causing them to assume a _silvery_ or rusty-brown appearance.
Stipules are absent; the leaves are simple, most frequently scattered.
Flowers (Figs. 484, 485) frequently unisexual. The sepals are
valvate, 2-4; the _corolla is wanting_; _stamens_ 4 + 4 or 0 + 4.
The ovule is _erect_ and _the radicle turned downwards_ (Fig. 486).
The fruit is a _nut_, but becomes _a false fruit_, being surrounded
by the persistent receptacle or the lower part of it, and thus
assuming a berry- or drupe-like appearance (Fig. 486). Endosperm
insignificant.--_Shepherdia_ (opposite leaves) has 4 sepals, 4+4
stamens, as in _Daphne_. Diœcious.--_Elæagnus_ (Silver-leaf) is ☿,
has 4–6 sepals, and 4–6 stamens alternating with them. _Hippophaë_
is diœcious; it has 2 sepals and 4 stamens in the ♂-flower (perhaps
properly speaking 2+2 stamens); thorny (stem-structures).

   16 species; especially ornamental shrubs, _e.g. Elæagnus
   argentea_, _angustifolia_; _Hippophaë rhamnoides_ and
   _Shepherdia canadensis_. Northern Temp.

  [Illustration: FIGS. 484–486.--_Elæagnus angustifolia._

  FIG. 484.--Floral diagram.

  FIG. 485.--Longitudinal section through the flower.

  FIG. 486.--Longitudinal section through the fruit.]

Order 3 (?). =Proteaceæ.= This order has its chief centre in the dry
regions of Australia (6/10–7/10 of about 1,000 species), a smaller
number in S. Africa (2/10–3/10). a few species in S. Am. Trees or
shrubs, leaves generally scattered, without stipules, and more or
less dry, leathery, evergreen, and often of very different forms on
the same plant (undivided, compound, etc.) The flowers are ☿ (rarely
unisexual), and _4-merous_ in the single, petaloid perianth and in the
staminal whorl; 1 carpel; sometimes zygomorphic. The perianth-leaves
are generally almost free, with _valvate_, æstivation, often leathery.
Small scales alternating with the perianth are often found at the
base of the ovary. The stamens generally have extremely short
filaments, and are situated opposite, sometimes quite on the tip of the
perianth-leaves, in a spoon-like groove. The gynœceum is 1-locular, has
1–several ovules, and is often raised on a stalk-like internode. The
fruit is a follicle or nut. The seeds, most frequently winged, have no
endosperm.--_Protea_, _Manglesia_, _Hakea_, _Banksia_, _Grevillea_,
etc. 50 genera; about 1,000 species. Several species are cultivated in
our conservatories for the sake of the flowers, which are beautifully
coloured and arranged in crowded inflorescences. Protandrous. It is
doubtful whether they were existent in Europe in the Tertiary Period.
The true systematic position of the order is doubtful. They are related
to the Leguminosæ and Rosifloræ, but more closely no doubt to the two
preceding orders.


                       Family 19. =Saxifraginæ.=

The flower is generally perfect, regular and polypetalous, usually
_perigynous_ or _epigynous_, _eucyclic_ and 5-merous; most frequently
S5, P5, A5 + 5 or 5 + 0 and G=2=-5, but other numbers are found,
especially 4; the flowers are very frequently obdiplostemonous. The
calyx is sometimes large and the corolla small; the carpels in some
are entirely free, in others more or less united. Endosperm is found
in the majority. ~The hypogynous forms approach the Cistifloræ, the
others the following families, especially the Rosifloræ. This family
is not, upon the whole, so well defined and natural as most of the
others. The Saxifragaceæ proper, approach very near to the Rosaceæ,
especially _Spiræa_, and form a transition to it. The forms with
opposite leaves, as _Philadelphus_, etc., approach the Myrtifloræ, just
as the Escalloniæ appear to be closely allied to Bicornes, especially
_Vacciniaceæ_. Finally through _Pittosporaceæ_, they pass over to the
Frangulinæ. The family terminates in very reduced forms, on the one
hand in the arborescent orders with crowded inflorescences, on the
other perhaps in the very remarkable order _Podostemaceæ_.~

  [Illustration: FIG. 487.--Diagram of a 6-merous flower (_Sedum
  hispanicum_): _w_ branch of scorpioid cyme in the axil of the
  bracteole β.]

Order 1. =Crassulaceæ.= Nearly all are herbs or small shrubs with
round, succulent branches and scattered, _fleshy_, often more or less
round leaves, which are very rarely incised, and never have stipules.
The flowers are generally borne in dichasia or unipared scorpioid
cymes, which again may be arranged in racemes, umbels, etc.; they are
regular, ☿, hypogynous or perigynous, and most frequently have free
sepals and petals (gamopetalous corollas with sessile stamens are found
in _Cotyledon_, _Bryophyllum_, _Echeveria_, and others); the floral
formula is Sn, Pn, An + n, Gn, where n may have very different values,
partly depending upon the size of the flower (_e.g._ 4–7 in _Sedum_,
Fig. 487; 6–30 in _Sempervivum_; 4 in _Rhodiola_, _Bryophyllum_,
and _Kalanchoë_; 5 in _Echeveria_, _Umbilicus_, _Cotyledon_). The
carpels are _free_ and are _placed opposite the petals_ (Fig. 487).
Fruit a _syncarp composed of follicles_ containing many, small seeds
without endosperm. Outside each carpel is found a small, nectariferous
scale (Fig. 487). ~The northern genus, _Rhodiola_, is diœcious. The
petal-stamens are wanting in some (_Crassula_, _Bulliarda_, and
others). The floral-leaves are very often displaced upon their axillary
branches. A multicarpellary gynœceum also occurs.~

_Sedum_ (Stonecrop) is generally 5-merous with 10 stamens; _Sempervivum
tectorum_ (House-leek), 12-merous, and with 24 stamens. ~The leaves
of _Bryophyllum calycinum_ very readily form buds, and also frequently
exude water from the edges.~

   485 species; especially Temp. (Cape, Europe). Principally used
   as ornamental plants.

Order 2. =Saxifragaceæ.= The flowers are 4–5-merous with =2= (-3)
carpels, most frequently: S5, P5, A5 + 5 (obdiplostemonous), G2. They
are regular, ☿, polypetalous, hypogynous, perigynous or most frequently
_more or less epigynous_ (Fig. 488). The carpels may be individually
quite free, but are more frequently united at the base, or the entire
portion enclosing the ovules is united into a 1- or 2-locular ovary, the
styles, however, are always free. _Fruit a capsule_ with many seeds;
endosperm present.--They are herbs, most frequently with _scattered_
leaves without stipules; but the leaf-base is broad. The inflorescences
are most frequently cymose, and a displacement of the floral-leaves is
frequent (_e.g._ _Chrysosplenium_).--~Some _Saxifraga_-species, _e.g._
_S. sarmentosa_, have irregular flower with an _oblique_ plane of
symmetry. The petal-stamens in some may be wanting: _Heuchera_, species
of _Saxifraga_ and _Mitella_. The corolla is wanting in others.~

_Saxifraga_ (Saxifrage): S5, P5, A5 + 5, G2 (Fig. 488); capsule
bilocular, opening along the ventral suture between the 2 persistent
styles. ~_S. granulata_ has small tubers at the base of the
stem.~--_Chrysosplenium_ (Golden Saxifrage): 4 sepals, _no corolla_, 4
+ 4 stamens; 1-locular capsule.

   Protandry is most frequently found in _Saxifraga_, with the
   stamens successively bending towards the gynœceum; protogyny
   is more rare. In other genera there is protogyny without any
   movement of the stamens; _Chrysosplenium_ is homogamous.--About
   300 species; mostly in temperate climates. _Saxifraga_ is
   especially Alpine. _S. crassifolia_ and other species, _Hoteia
   japonica_, _Tellima_, etc., are ornamental plants.

  [Illustration: FIG. 488.--_Saxifraga granulata._ Longitudinal
  section of flower.]

The following genera are allied to the Saxifragaceæ:--

=1.= _Parnassia_ (about 14 species; _P. palustris_, Grass of
Parnassus). The flower is slightly perigynous, and has S5, P5, 5
fertile sepal-stamens, and 5 petal-stamens, which are developed as
barren staminodes, palmately-lobed, and (3–) 4 carpels united in a
1-locular ovary with (3–) 4 parietal placentæ. Capsule.--~Protandrous.
The flower has a slightly oblique plane of symmetry, which is
especially shown during its development and in the order of sequence
in which the anthers dehisce: originally they lie closely round the
gynœceum; the anthers dehisce extrorsely, first the one which is placed
opposite the most external sepal (the 2/5 arrangement is very distinct
in the calyx), the filament elongating so that the anther lies over
the ovary, and this is followed successively by the 4 others in a
zig-zag line; the filaments bend backwards after the pollen is shed
and the anthers drop off, and the stigmas are not developed until this
is completed. The barren stamens are palmately divided into an uneven
number (7, 9, 11) of lobes, tapering from the centre towards the edge,
and bearing apparently glandular tips; their gland-like appearance is
supposed to allure flies to visit the flower, or they may act as a kind
of fence which compels the insects to enter the flower in a certain
way, and thus effect pollination; the honey is secreted on their inner
side, and not by the gland-like tips.~

  [Illustration: FIG. 489.--Portion of _Cephalotus follicularis_:
  _k_ pitcher-like leaf with thick corrugated edge (_m_) and lid
  (_l_); _b_ foliage-leaf of the ordinary form.]

=2.= _Adoxa moschatellina_ (Moschatel). This is a perennial, creeping
herb; the horizontal rhizome has an unlimited growth, and bears, in
a _scattered_ arrangement, both foliage-leaves, and white, fleshy
scale-leaves. The aerial stem bears 2 opposite foliage-leaves and a
capitate inflorescence of 5 flowers, 4 placed laterally (in opposite
pairs) and 1 terminally. The flower is semi-epigynous, the calyx
gamosepalous, corolla absent. The stamens are divided to the base, so
that each filament bears a bilocular anther. The style is free, deeply
cleft. The _terminal_ flower has 2 bracteoles, 4 sepals, 4 stamens,
cleft to the base, and a 4-locular ovary. The bracts of the _lateral_
flowers are displaced on the flower-stalk, as in _Chrysosplenium_, and
united with the 2 bracteoles into a kind of 3-leaved involucre; these
flowers have 5 sepals, 5 split stamens with 2-locular anthers, and a
5-locular ovary. 1 pendulous ovule in each loculus. Fruit a _drupe_,
green-coloured, with 1–5 stones.--This plant, which would perhaps
be best placed in a special order, has also been classed with the
Araliaceæ and Caprifoliaceæ.

   The following are also allied to this order: _Escalloniaceæ_
   (arborescent plants with simple, scattered, leathery leaves),
   _Cunoniaceæ_ (arborescent with opposite leaves), _Cephalotaceæ_
   (with pitcher-like, insect-catching leaves; Australia; Fig.
   489) and _Francoaceæ_. These have respectively 85, 107, 1 and 3
   species.

  [Illustration: FIGS. 490–492.--_Ribes rubrum._

  FIG. 490.--Floral diagram.

  FIG. 491.--Flower in longitudinal section.

  FIG. 492.--Seeds in longitudinal section.]

Order 3. =Ribesiaceæ= (=Currants=). 5-stamened Saxifragaceæ with
epigynous flowers.--Moderately sized shrubs with _scattered_, stalked
and palminerved, and generally palmilobed leaves, with a large
leaf-sheath. The flowers (Figs. 490, 491), most frequently borne in
_racemes_, are regular, _epigynous_, and have often, _above the ovary_,
a cup- or bell-shaped, or tubular prolongation of the receptacle, on
which the sepals, petals and stamens are situated; they have 5 sepals
(often large, coloured), 5 _small_, free petals, only =5= stamens
(opposite the sepals) and a =2=-carpellate gynœceum with a _unilocular_
ovary and 2 _parietal_ placentæ bearing many ovules. The fruit is a
_berry_, whose seeds have a fleshy and juicy outer covering (Fig. 492).
~In some species, for example _Ribes grossularia_, there is found an
unbranched, or a 3–5-branched spine, very closely resembling the spiny
leaves of the _Berberis_, but which, however, are emergences springing
from the base of the petiole. _Ribes_ has two kinds of branches:
long-branches and dwarf-branches, the latter alone bearing the
flowers.~--_Ribes_ (Figs. 490–492). The blades of the leaf are folded
or rolled together in vernation. _R. alpinum_ is diœcious.

   75 species; especially from the N. Temp. regions (especially
   N. Am.).--The receptacle secretes honey on its inner surface.
   The Gooseberry-flower is slightly protandrous, others are
   homogamous; insect-and self-pollination are found. The following
   are FRUIT BUSHES: _R. nigrum_ (Black Currant), _R. rubrum_
   (Red Currant), _R. grossularia_ (Gooseberry), originating in
   Northern Europe and Asia. ORNAMENTAL BUSHES: the North American
   _R. aureum_ (Golden Currant) and _R. sanguineum_ (Blood-red
   Currant), etc.

  [Illustration: FIG. 493.--_Deutzia crenata._ Longitudinal section
  of flower.]

Order 4. =Hydrangeaceæ.= Shrubs, with simple, opposite leaves,
without stipules; flowers generally epigynous, 4–5-merous (Fig.
493).--_Hydrangea_ (_H. hortensia_, etc.). Shrubs from N. Am. and E.
Asia; corolla often valvate. The inflorescence, as in the case of the
inflorescence of _Viburnum opulus_ (Guelder Rose), has often irregular,
large, but barren flowers at the circumference, whilst the others are
much smaller, regular and ☿; the barren flowers are mostly 4-merous;
in these cases it is the calyx which is large and petaloid, while the
other parts of the flower are more or less suppressed. The branches of
the inflorescence appear to be partially devoid of floral-leaves, since
they are displaced upon the main axis.--_Philadelphus_; racemes (with
terminal flower), sepals 4 (valvate), petals 4 (twisted), stamens many,
and carpels 4 (opposite the petals), forming a 4-locular ovary. The
numerous stamens (20–30) occur by the splitting of the sepal-stamens
and are often therefore placed in distinct bundles. Fruit a capsule.
_Ph. coronaria_ (Syringa, Mock Orange-blossom), from S. Eur., is a
common ornamental shrub, as also is _Deutzia_ (Fig. 493) from N. Am.
and E. Asia. The latter has S5, P5, A5 + 5, G3.--About 70 species.

Order 5 (?). =Pittosporaceæ.= This order has its home especially in
Australia (90 species). The flower has S5, P5, A5 (episepalous), G2
(3–5), most frequently a unilocular ovary with many ovules in 2 rows,
borne on 2 parietal placentæ, or a bilocular ovary. Some have berries,
others capsules. _Pittosporum, Citriobatus, Sollya, Billardiera._

Order 6. =Hamamelidaceæ.= Flowers more or less epigynous, with S4, P0
or 4, 4 fertile sepal-stamens, and 4 barren petal-stamens, bilocular
ovary with 1–2 ovules in each loculus. Fruit a capsule. _Hamamelis_:
one species in Japan and one in N. Am. _Fothergilla._ _Liquidambar_:
monœcious; flowers in capitula or spikes; ♂-flowers without perianth,
stamens indefinite; ♀-flower: slight perianth, 2-locular ovary with
many ovules. OFFICINAL: “Styrax-balsam,” which is obtained by boiling
the bark of _Liq. orientalis_, from Asia Minor. _Liquidambar_ and
_Parrotia_ are found as fossils in the Upper Oligocene; _Hamamelis_
perhaps in the Chalk.

Finally two orders with very reduced flowers are included in this
family.

Order 7. =Platanaceæ.= Trees, with large, scattered, palminerved and
lobed leaves, and ochreate stipules; the buds are concealed in a hollow
at the base of the petiole. The bark falls off in large scales. ♂-and
♀-flowers (monœcious) in crowded, spherical inflorescences which are
placed at wide intervals on a terminal, thin, and pendulous axis. The
flowers have an insignificant calyx and corolla; the ♂-flower has few
stamens; ♀-flower, perigynous, with 4 free carpels, 1 _pendulous_,
_orthotropous_ ovule in each. Fruit a nut; endosperm absent. 5 species;
frequently grown in avenues and parks. _P. occidentalis_ (N. Am.); _P.
orientalis_ (W. Asia.).

Order 8. =Podostemaceæ.= Aquatic plants, especially in swiftly
running water, with somewhat of an Alga-like, Moss-like, or thalloid
appearance; they show themselves in many ways to be adapted to their
mode of life and situations (having a dorsiventral creeping stem, the
flowers sunk in hollows, a formation of haptera upon the roots, and
thalloid assimilating roots and thalloid stems, etc.). Tropical; 100
species.


                        Family 20. =Rosifloræ.=

The leaves are scattered, stipulate, or have at least a well developed
sheath, which is generally prolonged on each side into a free
portion (“adnate stipules”). The flowers are regular, _perigynous_
or _epigynous_. Calyx and corolla 5 (-4)-_merous_ with the usual
position. The corolla is always polypetalous. The stamens are present
in very varying numbers (5–∞) and position, but _always_ placed in
5-_or_ 10-_merous whorls_; they _are frequently_ 20 in 3 whorls (10
+ 5 + 5; see Figs. 494, 502, 505); the nearer they are placed to the
circumference, the longer they are; they are generally _incurved in the
bud, or even rolled up_. The number of the carpels is from 1–∞; in most
cases all are _individually free_ (syncarp), and when they are united
it is in every case with the ovaries only, whilst the _styles_ remain
more or less _free_ (_Pomaceæ_, species of _Spiræa_). The _seeds_ have
a straight embryo, and usually no endosperm.

   The perianth and stamens are most frequently _perigynous_ on
   the edge of the widened receptacle; its form varies between a
   flat cupule and a long tube or a cup (Figs. 495, 496, 498, 499,
   500); the carpels are situated on its base or inner surface, in
   some instances on a central conical elongation of the floral
   axis (Fig. 496). The carpels in _Pomaceæ_ also unite more or
   less with the hollow receptacle, or this grows in and fills up
   the space between the carpels, so that a more or less epigynous
   flower is formed (Fig. 504).--The following numbers of _stamens_
   occur: 5, 10 (in 1 whorl), 15 (10 + 5), 20 (10 + 5 + 5), 25 (10
   + 10 + 5), 30-50 (in 10-merous whorls)--compare the diagrams.
   The theoretical explanation of this relation of the 10-merous
   whorls and their alternation with the 5-merous whorls is not
   definitely determined; a splitting of the members of the
   5-merous whorls may be supposed, but the development shows no
   indication of this, and it is not supported in any other way.
   Several genera have “_gynobasic_” styles, that is, the style
   springs from the base of the ovary (Fig. 497 _A_, _B_).

   The Rosifloræ are on one side closely related to the
   Saxifragaceæ (especially through _Spiræa_) from which it is
   difficult to separate them, and to the Myrtifloræ; on the other
   side they are allied, through the Mimosaceæ with the large
   number of stamens, and through the Amygdalaceæ with its single
   carpel, to the Leguminosæ. The family begins with forms which
   have many-seeded follicles, and passes on the one side to forms
   with nuts and drupes in perigynous flowers, and on the other
   side to the Pomaceæ.

Order 1. =Rosaceæ.= Herbs or shrubs, generally with compound leaves and
persistent (adnate) stipules, flower _perigynous_, _gynœceum formed of
many free_ (therefore oblique) _carpels, syncarps_ with fruitlets of
various kinds. The exceptions are noted under the genera.

  [Illustration: FIG. 494.--Diagram of _Comarum palustre_.]

  [Illustration: FIG. 495.--Flower of _Spiræa lanceolata_.]

=1.= SPIRÆEÆ (Fig. 495) has 2–many ovules in each ovary, while in the
other groups there is generally only 1, and never more than 2 ovules in
each loculus. There are generally 5 _cyclic_ carpels and the fruit is
5 _follicles_, which are not enclosed by the receptacle. The majority
are shrubs. Stipules are often wanting.--_Spiræa_ (Meadow-Sweet).
The flowers are generally borne in richly flowered inflorescences
of various forms. The carpels, in some species, unite together
and form a _simple_ gynœceum with free styles (an approach to the
_Pomaceæ_).--~Closely allied to _Spiræa_ are the East Asiatic shrubs:
_Kerria japonica_, which has solitary flowers, in this country nearly
always double (the fruit a nut), and _Rhodotypos kerrioides_ which
has opposite leaves, a remarkable feature among the Rosifloræ; it has
a 4-merous flower, a well developed disc inside the andrœcium, and a
drupe. Closely allied also is _Gillenia_ (N. Am.) differing chiefly
in the ascending ovules, _Spiræa_ having pendulous ovules, and a more
tubular receptacle.~

   The groups _Quillajeæ_ and _Neuradeæ_ form a transition from
   _Spiræa_ to _Pomaceæ_. In the first group, which contains only
   trees or shrubs with generally simple leaves, the carpels are
   either free or united (into a capsule); in the second the
   receptacle unites with the carpels, which are themselves often
   united together; in this case, too, the fruit is a capsule.
   _Quillaja_ (S. Am.); _Exochorda_ (China).

=2.= POTENTILLEÆ (Figs. 494, 496, 497). The flower has an “_epicalyx_”
(Fig. 494 _C_) alternating with the sepals and formed by their
stipules which are united in pairs, and hence its leaves are often
more or less deeply bifid. The receptacle is cupular and often quite
insignificant. The sepals are valvate in the bud. The large number of
fruitlets are _achenes_, borne on a well-developed convex portion of
the receptacle (~the Ranunculeæ resemble the Potentilleæ, but have
no epicalyx, no enlarged receptacle, and spirally-placed stamens~).
Most of the species are herbs with dichasial inflorescences, often
arranged in racemes.--_Potentilla_ (Cinquefoil). The achenes are
borne on a _dry_, hairy receptacle; the style is situated towards
the apex of the ovary, and is not prolonged after flowering. Herbs
with digitate, in some, however, pinnate leaves, and generally yellow
flowers.--_Comarum_ (Fig. 494) (Marsh Cinquefoil) forms, by its
fleshy-spongy receptacle, a transition to the next genus.--_Fragaria_
(Strawberry) (Fig. 496). The receptacle becomes finally fleshy,
coloured, and falls off (biologically it is a berry); the numerous
fruitlets (drupes with thin pericarp) have basal styles (Fig. 497);
leaves trifoliate; long, creeping runners.--_Geum_ (Avens) has a
terminal style which after flowering elongates into a long beak, with
the apex (after the uppermost part has been thrown off) bent back into
a hook, thus furnishing a means of distribution for the fruits. Leaves
pinnate.--~_Dryas_ comprises 3 Arctic or Alpine species with simple
leaves and solitary flowers, the calyx and corolla 8–9-merous, the
fruit resembles that of _Geum_, but the styles become still longer and
feather-like (a flying apparatus).~

  [Illustration: FIGS. 496, 497.--_Fragaria vesca._

  FIG. 496.--Longitudinal section of flower.

  FIG. 497.--A carpel, entire, and in longitudinal section.]

=3.= RUBEÆ. _Rubus_ (Bramble) has the same form of receptacle as the
_Potentilleæ_, but _no epicalyx_; _the fruitlets are drupes_, not
enclosed by the persistent calyx. Most frequently shrubs or undershrubs
with prickles (emergences), glandular bristles and compound leaves.
In the Raspberry (_R. idæus_) the fruitlets unite together and detach
themselves from the receptacle.

=4.= ROSEÆ. _Rosa_; the receptacle is hollow, ovoid and contracted
beneath the insertion of the calyx (Fig. 498), ultimately _fleshy_
and _coloured_; it encloses a large number of fruitlets which are
achenes as hard as stones (“hip,” biologically a berry).--Shrubs with
imparipinnate leaves and adnate stipules. ~The sepals show clearly the
order of their development (a divergence of 2/5), the two outer ones on
both sides are lobed, the third one on one side only, and the two last,
whose edges are covered by the others, are not lobed at all. _Prickles_
(emergences) are generally present and in some species are placed in
regular order, being found immediately below each leaf (usually two)
although at somewhat varying heights.~

  [Illustration: FIG. 498.--Longitudinal section of flower of
  _Rosa_.]

  [Illustration: FIGS. 499, 500.--_Agrimonia eupatoria._

  FIG. 499.--Flower in longitudinal section.

  FIG. 500.--Fruit and receptacle in longitudinal section.]

=5.= AGRIMONIEÆ. The receptacle is more or less cup- or bell-shaped,
and almost closed at the mouth; it is persistent and envelopes the
_nut-like fruitlets_, but is _dry_, and in some species hard, the
fruitlets being firmly attached to it. In biological connection
with this the number of the carpels is generally only 1 or 2, and
the whole becomes a _false nut_ (Fig. 500). Herbs.--_Agrimonia_
(Agrimony; Figs. 499, 500); the perianth is 5-merous, stamens 5–20.
The receptacle bears externally, on the upper surface, a number of
hooked bristles which serve as a means of distribution for the 1–2
achenes which are enclosed in it, and hence the entire flower finally
falls off. The inflorescence is a long upright raceme. ~These bristles
are arranged in whorls of 5 and 10, of which the uppermost alternate
with the sepals.~--_Alchemilla_ (Ladies-mantle; Fig. 501) has 8 green
perianth-leaves in two whorls (some authorities consider the four outer
as an epicalyx, and the flower therefore apetalous), and 4 stamens
_alternating with the innermost whorl_. There is only one carpel with a
_basal_ style and capitate stigma. The flowers are small and greenish,
the filaments jointed. The anthers open by one extrorse cleft. The
leaf-sheath entirely envelops the stem; the leaves are palminerved.
_A. aphanes_ has often only 1–2 stamens. ~The following genera, with
4-merous flowers borne in short spikes or capitula, are allied to this
group. _Sanguisorba_ has entomophilous, ☿-flowers with 4(-20) stamens,
1 carpel; stigma papillose.--_Poterium_; spike or capitulum, the
uppermost flowers are ♀, the lowermost ♂, and some intermediate ones ☿
(the order of opening is not always centripetal); S4, P0, A20–30, G2,
the long styles having brush-like stigmas (wind-pollination). Leaves
imparipinnate.~

  [Illustration: FIG. 501.--Flower of _Alchemilla_ in longitudinal
  section.]

   POLLINATION. A yellow ring on the inner side of the receptacle,
   inside the stamens, serves as a nectary when any honey
   is formed; this, for instance, is not the case in _Rosa,
   Agrimonia_, _Spiræa ulmaria_, _S. filipendula_, _S. aruncus_,
   etc., to which the insects (especially flies and bees) are
   allured by the quantity of pollen. Homogamy and slight
   protogyny are frequent, in many instances self-pollination
   also is finally possible. _Poterium_, with the long-haired
   stigma, is wind-pollinated.--About 550 (1100?) species,
   especially in northern temperate regions.--USES. OFFICINAL:
   the petals of _Rosa centifolia_ and _gallica_, the fruits of
   the Raspberry (_Rubus idæus_), the rhizome of _Geum urbanum_,
   the flowers of the Koso-tree (_Hagenia abyssinica_ or _Brayera
   anthelmintica_).--The bark of _Quillaja saponaria_ (Chili) is
   used as soap and contains _saponin_. “Attar of Roses” from
   _Rosa damascena_, _centifolia_ and other species, especially
   from the southern slopes of the Balkans. Many species and
   varieties of Roses are ORNAMENTAL plants: from S. Europe, _Rosa
   lutea_ (the Yellow Rose), _R. gallica_ (the French Rose) and
   _R. rubrifolia_; from W. Asia, _R. centifolia_, of which the
   Moss Roses (_R. muscosa_ and _cristata_) are varieties, and _R.
   damascena_; from India and N. Africa, _R. moschata_ (the Musk
   Rose); from China, _R. indica_ (Tea Rose) etc., besides the
   native species and the varieties which have been derived from
   them. In addition, _Kerria japonica_, species of _Potentilla_,
   _Rubus odoratus_ from N. Am., and many species of _Spiræa_ from
   South-eastern Europe and N. Am. ESCULENT: the “hips” of _R.
   mollissima_, _R. pomifera_, etc.; the fruits of _Rubus_-species:
   Raspberry (_R. idæus_), Cloudberry (_R. chamæmorus_), Blackberry
   (_R. fruticosus_), etc.; of _Fragaria_-species (_F. vesca_,
   _collina_, _grandiflora_, etc).

Order 2. =Amygdalaceæ.= Trees or shrubs with rosaceous flowers;
leaves simple with caducous stipules; a regular, _perigynous_ flower,
the receptacle being partly thrown off by a circular slit; sepals
5, petals 5, stamens 20–30; _gynœceum simple, formed of 1 carpel_
(hence oblique, Fig. 502), with terminal style and 2 pendulous ovules,
ripening into a _drupe_ (Fig. 503).--The leaves are penninerved and
frequently have _glands_ on the stalks and edges; _thorns_ (modified
branches) often occur, _i.e._ dwarf-branches, which, after producing
a few leaves, terminate their growth in a thorn (_e.g._ _Prunus
spinosa_). ~The vernation of the _foliage-leaves_ varies in the
different genera; in the Almond, Peach, Cherry, and Bird-Cherry they
are folded; in the Apricot, Plum, Sloe and Bullace, rolled together. In
some the flowers unfold before the leaves (_Amygdalus_, _Armeniaca_).
That the gynœceum is formed of 1 carpel is evident in this as in other
instances (_e.g._ in the Leguminosæ, which are closely related to this
order), from the fact that the carpel is oblique, and has only one
plane of symmetry, and similarly in the fruit there is a longitudinal
groove on one side which indicates the ventral suture. It is only
exceptionally that both ovules are developed. In abnormal instances
more than 1 carpel is developed.~

  [Illustration: FIG. 502.--Diagram of _Prunus virginiana_.]

=A.= FRUIT HAIRY: _Amygdalus_ (_A. communis_, Almond-tree) has a dry
pulp which is detached irregularly, when ripe, from the wrinkled,
grooved, ovoid and somewhat compressed stone.--_Persica_ (_P.
vulgaris_, Peach-tree) differs from the Almond in having a juicy pulp,
not detachable from the stone, which is deeply grooved and has pits
in the grooves (Fig. 503). (~The name of the genus is derived from
Persia, though it is a native of China.~).--_Armeniaca_ (_A. vulgaris_,
Apricot) has a hairy, velvety fruit, but the stone is smooth and has
two ribs along one of the edges; the pulp is juicy. (~The generic name
has been given on the incorrect assumption that it was a native of
Armenia; its home is China.~)

  [Illustration: FIG. 503.--Fruit of the Peach. The pulp is cut
  through so that the stone is visible.]

=B.= FRUIT GLABROUS (_i.e._ without hairs): _Prunus_ (Plum) has a
glabrous fruit with bluish bloom; the stone is compressed, smooth or
wrinkled. The flowers are borne solitarily or in couples, and open
before or at the same time as the leaves; they are borne on shoots
without foliage-leaves.--_Cerasus_ (Cherry) has a glabrous, spherical
fruit, without bloom, and a spherical stone. The flowers are situated
in 2–many-flowered umbels or racemes, and open at the same time as the
leaves or a little before them. ~_Long-stalked_ flowers in _umbels_
are found in _C. avium_ (Wild Cherry), _C. vulgaris_ (the cultivated
Cherry, from Western Asia); _racemes_ at the apex of leaf-bearing
branches and small spherical fruits are found in _C. padus_ (Bird
Cherry), _C. virginiana_, _C. laurocerasus_ (Cherry-laurel), _C.
mahaleb_.~

   POLLINATION. _Prunus spinosa_ (Sloe, Blackthorn) is protogynous,
   but the stamens are developed before the stigma withers. Honey
   is secreted by the receptacle. _Cerasus padus_ (Bird-Cherry)
   agrees in some measure with _P. spinosa_. In the flowers of
   the Plum and Cherry the stamens and stigma are developed
   simultaneously and self pollination seems general; the
   stigma, however, overtops the inner stamens and thus promotes
   cross-pollination.--DISTRIBUTION. 114 species in the N. Temp,
   zone; few in the warmer regions; the majority from W. Asia. _C.
   vulgaris_, from the regions of the Caspian; _Prunus spinosa_,
   _insititia_ (Bullace), _domestica_ (Plum, from the Caucasus,
   Persia).--USES, principally as fruit-trees: Cherry, Plum,
   Apricot, etc.; “Almonds” are the seeds of _Amygdalus communis_
   (W. Mediterranean), “bitter,” “sweet,” and “shell” almonds are
   from different varieties, the latter being remarkable for the
   thin, brittle stone. In the majority of species and in almost
   all parts of the plant (especially the bark, seed and leaves)
   is found the glycoside, _amygdalin_, which forms prussic acid.
   Many form _gum_, and the seeds have _fatty oils_ (“Almond
   oil”). OFFICINAL: the seeds and oil of _Amygdalus communis_,
   and the fruit of the Cherry; in other countries also the leaves
   of _C. laurocerasus_.--The stems of _Cerasus mahaleb_ are
   used for pipes. Ornamental Shrubs: _Amygdalus nana_, _Cerasus
   laurocerasus_.

   Order 3. _Chrysobalanaceæ._ Tropical Amygdalaceæ with
   zygomorphic flower and gynobasic style. 200 species; especially
   Am. and Asia. _Chrysobalanus icaco_ (Cocoa-plum) is cultivated
   on account of its fruit (Am.)

Order 4. =Pomaceæ.= Trees and shrubs, most frequently with simple
leaves and caducous stipules. The flowers (Fig. 505) have 5 sepals, 5
petals and generally 20 stamens (10 + 5 + 5, or 10 + 10 + 5). There are
from 1–5 _carpels_, which unite entirely or to some extent with each
other, and with the hollow, fleshy receptacle (the _flower_ becoming
_epigynous_), (Figs. 505, 506, 507). The carpels are nearly always
free on the ventral sutures, rarely free at the sides also. The whole
outer portion of the fruit becomes fleshy, but the portions of the
pericarp surrounding the loculi (endocarp) are most frequently formed
of sclerenchymatous cells, and are more or less firm (the “core”). The
nature of the fruit varies, according to the thickness and hardness
of the endocarp, being either a “berry” or a “drupe” (see _A_ and
_B_). When the endocarp is thin and parchment-like, the fruit has the
characteristics of a berry, each of the 5 loculi generally present
containing several seeds; but when this is hard the fruit resembles a
drupe, only one seed is developed in each loculus, and the number of
the loculi is reduced to one or two. There are nearly always 2 ovules
in the loculi of the ovary, but in _Cydonia_ there are a large number
in 2 rows. In the genera which have stones, only one seed is developed
in each stone. The genera are distinguished mainly in accordance with
the kind of fruit and the number of ovules and seeds.

  [Illustration: FIG. 504.--Longitudinal and transverse section
  through the flowers of _A_, _B_ _Cotoneaster_; _C_ _Cydonia_;
  _D_ _Malus communis_; _E_ _Raphiolepis_; _F_ _Cydonia_; _G_
  _Mespilus_.]

  [Illustration: FIG. 505.--Floral diagram of _Mespilus germanica_.]

=A.= SORBEÆ. THE ENDOCARP IS PARCHMENT-LIKE OR PAPERY (drupe, with thin
stone or berry).

1. _Pyrus_ and _Cydonia_; carpels completely embedded in the cup-like
receptacle, styles always free.--_Pyrus_: the fruit is glabrous,
and has only a small calyx, withering or deciduous, and a 5-locular
ovary with at most 2 ascending ovules in each loculus (Fig. 504
_D_). The large flowers are situated in few-flowered umbels or
corymbs. ~_P. communis_ (Pear; free styles, Fig. 507; it has the
well-known pear-shaped fruit; the core is reduced to several groups
of sclerenchymatous cells embedded in the pulp, the leaf-stalk is as
long as the blade).~--_Cydonia_ (Quince) has a hairy fruit with _many
seeds in 2 rows_ in each loculus of the endocarp (Figs. 504 _C_, _F_;
506); the testa of these seeds is mucilaginous. _C. vulgaris_, large,
terminal flowers on lateral branches, and large leaf-like, persistent
sepals.

  [Illustration: FIG. 506.--_Cydonia vulgaris._ Longitudinal
  section of fruit.]

  [Illustration: FIG. 507.--Longitudinal section of Pear flower.]

2. _Malus_ and _Amelanchier_ (_Aronia_); carpels free on the ventral
edge; styles united. _Malus communis_ (Apple) the fruit is “umbilicate”
at the base; no sclerenchymatous cells in the pulp; styles united at
the base (Fig. 504 _D_); leaf-stalk shorter than the blade. _Sorbus_
(Mountain-ash) differs only in having a 2–3-locular fruit with
extremely thin endocarp. Cymose inflorescences in umbellate cymes.
~_S. aucuparia_ has pinnate leaves, _S. aria_ (White-beam) and other
species have simple leaves.--_Amelanchier_ (the Service-tree) has a
false divisional wall springing from the dorsal suture, and more or
less projecting into each of the loculi of the ovary; _Raphiolepis_
(Fig. 504 _E_) has racemes and a juicy berry; _Eriobotrya japonica_
(Loquat).~

=B.= CRATÆGEÆ. THE ENDOCARP IS HARD AND BONY (“drupes,” generally
with several, sometimes, however, with only 1–2 stones, rarely one
multilocular stone; only 1 seed in each of the loculi).--_Cratægus_
(Hawthorn, May). There are 1–5 stones in the spherical or ovoid fruit.
The disc, found on the apex of the fruit, inside the small, withered
calyx, is small (much less than the transverse section of the fruit).
Shrubs with thorns (branches) and moderately large flowers borne in
corymbs.--_Mespilus_ (Medlar) differs from the last-named only in
having a _large disc_ at the apex of the fruit, inside the large,
_leaf-like sepals_, _i.e._ almost equal to the greatest diameter of the
fruit. The flowers are solitary and terminal.--_Cotoneaster_ is chiefly
distinguished from the others by its syncarps, the 2–5 carpels (and
stones) being free from one another, and only united to the receptacle
by a larger or smaller portion of their dorsal surface (Figs. 504 _A_,
_B_). Small shrubs with leathery leaves, generally covered with white,
felted hairs on the lower surface, and with small flowers; the fruit is
red or black.

   Pear, Apple, Mountain Ash and Hawthorn have protogynous
   flowers which secrete honey, and are conspicuous to ensure
   insect pollination.--180 species; in the northern temperate
   regions.--Pear and Apple are especially cultivated as fruit
   trees in a number of varieties; the Paradise Apple (_Pyrus
   baccata_); especially in southern countries also the Quince
   (from N. Persia and the Caucasian districts), Medlar and
   _Amelanchier vulgaris_. _Malus pumila_ (Caucasus,
   Altai) and _M. dasyphylla_ (Orient, S. Eur.) are regarded
   as primitive forms of the Apple-tree; _M. sylvestris_,
   which grows wild in European forests, appears to have been less
   used. The early Lake-dwellers in Switzerland had the apple-tree
   both wild and cultivated.--The original form of the Pear is
   supposed to be _Pyrus achras_ (Central Asia).--Many of
   the species of _Cratægus_, some with double flowers, and
   _Pyrus (Chænomeles) japonica_, with brilliant red flowers,
   are cultivated as ornamental shrubs. OFFICINAL: Quince
   pips, on account of the mucilaginous testa.--The fruits contain
   free organic acids and sugar; prussic acid may be obtained from
   the seeds. The wood of the Pear-tree is used in manufactures.


                       Family 21. =Leguminosæ.=

The most characteristic feature is, that the _gynœceum is 1-locular_
and formed of _1 carpel, the ventral suture of which is turned
posteriorly_. The fruit, in most instances, is a _pod_ (legume),
which opens generally along both sutures, the two valves twisting
more or less in opposite directions. ~In other instances it opens
along one suture only, or as a pyxidium (Red Clover), or it is
indehiscent, in which case it is more or less berry-like (_e.g._ the
Tamarind, Carob-bean), or it is a drupe (_e.g._ the Tonquin-bean), or
a 1–few-seeded nut (_e.g._ _Melilotus_), or a lomentum, which divides
transversely into as many joints as there are seeds (_Ornithopus_, see
Fig. 513).~

The inflorescences belong to the _centripetal_ type (_i.e._
indefinite); cymes do not occur. The flowers are _zygomorphic_, with
vertical plane of symmetry, seldom regular; _5-merous_ with but a few
exceptions, ☿, and slightly _perigynous_. The following diagram is the
most general (Fig. 511): 5 sepals, with the _unpaired sepal median
and anterior_, 5 petals, 5 + 5 stamens, all in alternating whorls, 1
carpel. The calyx is most frequently gamosepalous, the gynœceum is
narrowed down at the base to a short stalk and, in the majority, is
more or less bent. The seed is most frequently kidney-shaped, with
a smooth, hard and shining testa, the hilum being very distinct.
_Endosperm is wanting_, or is reduced to a thin layer, which is of
service when the seed swells during germination. The vegetative parts
have these features in common, namely, the _leaves are scattered,
stipulate_, and almost always _compound_. Peculiar _sleep-movements_
and _sensitiveness_ are found in some, chiefly in the Mimosas. Many,
probably all, Leguminosæ have _small tubercles on their roots_ which
are produced by a kind of bacterium, and assist in the assimilation
of free nitrogen. Spontaneous movements are exhibited by _Desmodium
gyrans_ (Telegraph-plant).

   This family is closely allied to the Rosifloræ, with which it
   agrees in the scattered leaves, the presence of stipules, the
   generally 5-merous and most frequently perigynous flowers with
   eucyclic stamens, and the absence of endosperm. _Amygdalaceæ_
   and _Chrysobalanaceæ_, with solitary carpels, approach on one
   side to the Leguminosæ, among which genera with drupes are also
   found; _Mimosaceæ_, with their many stamens, form a connecting
   link on the other side. In this respect the Mimosa-genus
   _Affonsea_, and certain Cæsalpineæ and Swartzieæ, are of special
   interest in having more than one carpel (syncarp), a condition
   which is sometimes met with abnormally in other Leguminosæ, as
   well as in Amygdalaceæ. About 7,000 species of the Leguminosæ
   are known.

Order 1. =Cæsalpiniaceæ.= These are _leguminous plants with straight
embryo and a flower which is not papilionaceous and has not the
same æstivation_ (Figs. 508–510); but in reality there is not a
single characteristic which absolutely distinguishes them from the
Papilionaceæ.--The majority are arborescent; the leaves as a rule
are pinnate or bipinnate. The flower is 5-merous, most frequently
perigynous and slightly zygomorphic; the calyx is free or gamosepalous,
the corolla polypetalous with _ascending imbricate æstivation_ (_i.e._
the two lowest petals envelop the lateral ones, and these again the
posterior; Fig. 508); 10 _free stamens_; fruit various.

  [Illustration: FIGS. 508–510.--_Cassia floribunda._

  FIG. 508.--Floral diagram.

  FIG. 509.--Flower.

  FIG. 510.--The same in long. sect.]

_Cassia_ (Figs. 508–510) is the largest genus (about 200 species); it
has an almost hypogynous, zygomorphic flower with 5 free sepals and
petals; of the 10 stamens the 3 posterior are generally barren, the
others are of very unequal length and open at the apex by _pores_ (Fig.
509). In some (the _Senna_ group) the fruit is a flat, short, thin,
dehiscing pod; in others (_Cathartocarpus_) it is round, long, woody
or fleshy, indehiscent, and divided internally by more or less fleshy
transverse walls into as many cells as there are seeds.--The following
also have DEHISCENT FRUITS: _Bauhinia_ (often lianes, tropical climbers
with tendrils [stem-structures] and anomalous stems), _Copaifera_,
_Hæmatoxylon_ (whose pod does not dehisce along the suture, but
laterally), _Cercis_ (simple leaves; the corolla resembles that of
the Papilionaceæ, but the posterior petal is the smallest, and is
enveloped by the 2 lateral ones, which are enveloped in their turn by
the 2 anterior).--FRUIT INDEHISCENT: _Tamarindus indica_; the pod is
almost round, often a little abstricted between the seeds; the wall
is formed by a thin, brittle external layer, enclosing an acid pulp;
well-developed septa are present, between the seeds; the most internal
layer is parchment-like. Calyx 4-merous by the coalescence of 2 sepals.
Only 3 fertile stamens.--_Ceratonia siliqua_ (Carob-bean, Locusts);
the pod is long, compressed, with thick sutures, and has a wall, the
central part of which is more or less leathery, fleshy and sweet;
there are transverse septa between the seeds, as in the Tamarind.
Embryo greenish in endosperm. The flower is without a corolla, 5
stamens.--_Pterogyne_ (winged fruit), etc.--KRAMERIEÆ with _Krameria_
is an anomalous group.

   DISTRIBUTION. 80 genera, with 740 species; almost exclusively
   in the Tropics. The Carob-tree and _Cercis_ grow in the
   Mediterranean basin. The largest and most widely distributed
   genus is _Cassia_, which is found as trees, shrubs, and weeds
   in all tropical countries. The order has many important
   uses to mankind. MEDICINAL: the leaves and pods of _Cassia
   acutifolia_ and _angustifolia_ (officinal, Senna-leaves),
   the fruit-pulp of the _Cassia_-sub-genus, _Cathartocarpus_.
   Rhatany root from _Krameria triandra_ (Peru, officinal).
   _Balsam_ is extracted from a number of _Copaifera_-species
   (Balsam of Copaiba) from S. Am. (officinal), and from _Hymenæa_
   (Copal balsam), _Trachylobium_ and others. _Edible fruits_ are
   obtained especially from the Carob-tree (from the East) and
   the Tamarind (officinal). The heart-wood of several species of
   _Cæsalpinia_, such as _C. brasiliensis_ (the Pernambuco-tree),
   _echinata_ (Red-tree), and _sappan_, yield _dyes_; _Hæmatoxylon_
   (_H. campechianum_, Logwood), _Copaifera bracteata_
   (Amarant-tree).--_Timber_ is obtained from many (_Melanoxylon_
   and others). In Europe they are of little importance as
   ornamental plants, these being confined principally to the
   species of _Gleditschia_ (_G. triacantha_, from N. Am.) and
   _Cercis_ (the Judas-tree, _C. siliquastrum_, S. Eur.), which
   are cultivated in gardens; but in tropical gardens beautiful
   flowering species, _e.g._ of _Cassia_, _Poinciana_, _Brownea_,
   are found, and the most beautiful of all ornamental plants, the
   Indian _Amherstia nobilis_.

  [Illustration: FIG. 511.--Diagram of _Faba vulgaris_: _f_ the
  standard; _v_ the wings; _k_ the keel.]

Order 2. =Papilionaceæ.= The flower (Figs. 511, 512) is _strongly
zygomorphic_ and somewhat perigynous (Fig. 512 _B_; most frequently
more on one side than the other). The calyx is _gamosepalous_ and
persistent. The polypetalous corolla has _descending_ imbricate
æstivation, the posterior, large leaf, the _standard_ (Figs. 511 _f_;
512 _B’_, _e_), _covering in the bud_ the two lateral ones, the _wings_
(Figs. 511 _v_; 512 _B’_, _a_), which again cover the two anterior;
these are united in the form of a boat, the _keel_ (_k_ and _c_); the
wings and the two petals of the keel are very unsymmetrical. That the
keel is formed of two petals is seen by its position (in front of one
sepal) and by the two often more or less free claws. The 10 (5 + 5)
_stamens_ (monadelphous) _are either all united into one bundle, or
into two bundles_ (diadelphous), the posterior one being free (Fig. 512
_C_). The ovules are _curved_ and _also the embryo_ (Fig. 512 _G_),
especially the hypocotyl, so that the radicle assumes a position close
to the edge of the thick, fleshy cotyledons. Endosperm wanting; the
cotyledons are very rich in proteid reserve material. The forms of the
fruit and exceptions are described under the genera.

  [Illustration: FIG. 512.--_Pisum sativum_: _A_ entire flower; _B_
  in longitudinal section; _C_ gynœceum and stamens; _D_ gynœceum;
  _B’_ corolla dissected, _e_ standard, _a_, _a_ wings, _c_ keel;
  _D_ seed opened to show the cotyledons (_c_), the radicle (_r_),
  the plumule (_g_); _E_ fruit (legume); _F_ seed.]

   _Geocarpic_ fruits, _i.e._ those which penetrate the soil during
   their development and ripen underground, are found in _e.g._
   _Arachis hypogæa_ (see page 472), _Trifolium subterraneum_,
   _Vicia amphicarpæa_. _Germination_ takes place in various ways.
   In the majority the c