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Title: Introduction to the Study of Palæontological Botany
Author: Balfour, John Hutton
Language: English
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INTRODUCTION
TO THE STUDY OF
PALÆONTOLOGICAL BOTANY
INTRODUCTION
TO THE STUDY OF
PALÆONTOLOGICAL BOTANY
BY
JOHN HUTTON BALFOUR, A.M. M.D. EDIN.
F.R.S., SEC. R.S.E., F.L.S.
PROFESSOR OF MEDICINE AND BOTANY IN THE UNIVERSITY OF EDINBURGH,
REGIUS KEEPER OF THE ROYAL BOTANIC GARDEN,
AND QUEEN'S BOTANIST FOR SCOTLAND
WITH FOUR LITHOGRAPHIC PLATES, AND UPWARDS OF
ONE HUNDRED WOODCUTS
EDINBURGH
ADAM AND CHARLES BLACK
1872
_Printed by_ R. & R. CLARK, _Edinburgh_.
TO
PROF. HEINRICH ROBERT GOEPPERT, M.D.,
DIRECTOR OF THE BOTANIC GARDEN, BRESLAU;
ONE OF THE MOST EMINENT PALÆONTOLOGICAL
BOTANISTS OF EUROPE,
The following Treatise
IS DEDICATED, WITH BEST RESPECTS, BY HIS
OBLIGED FRIEND
THE AUTHOR.
PREFACE.
The subject of Fossil Botany or Palæophytology has formed a part of
the Course of Botany in the University of Edinburgh for the last
twenty-five years, and the amount of time devoted to the exposition
of it has increased. The recent foundation of a Chair of Geology and
of a Falconer Palæontological Fellowship in the University seems to
require from the Professors of Zoology and Botany special attention
to the bearings of their departments of science on the structure
of the animals and plants of former epochs of the Earth's history.
No one can be competent to give a correct decision in regard to
Fossils, unless he has studied thoroughly the present Fauna and Flora
of the globe. To give a well-founded opinion in regard to extinct
beings, it is essential that the observer should be conversant with
the conformation and development of the living ones now on the
earth; with their habits, modes of existence and reproduction, the
microscopic structure of their tissues, their distribution, and their
relation to soil, the atmosphere, temperature, and climate.
There can be no doubt that to become a good Fossil Geologist a
student must begin with living animals and plants. The study of
Geology must be shared by the Petralogist, who looks at the
condition of the rocks of the globe, the minerals forming them, and
their mode of formation; the Chemist, who determines the materials
which enter into the composition of minerals and rocks; the
Naturalist, who examines the plants and animals found in the various
strata; and perhaps also the Natural Philosopher, who calculates from
independent sources the phases of the Earth's history. It may be said
thus to combine all these students of Science in one brotherhood.
Much has been done by the efforts of such men as Hutton and Werner,
who were engaged chiefly in considering the mineral department of
Geology; but it is clear that the Science could not have attained its
present position without the continued labours of those who have been
examining fossils in their relations to time and space. Had it not
been for the researches of Palæontologists, Geology could not have
made its present advance.
In my Class Book of Botany I have given an introduction to
Palæophytology, and it occurred to me that it might be useful to
students to publish this in a separate form, with additions in
both the letterpress and the illustrations. The institution of
the Palæontological Fellowship, in memory of my former friend Dr.
Falconer, has brought the subject specially under my notice. The
Fellowship has been promoted chiefly by my friend and former pupil
Dr. Charles Murchison, a gentleman fond of science and of his Alma
Mater, the University of Edinburgh, where he and Falconer studied and
took their degrees.
The first award of the Fellowship has been made to a distinguished
student, who acquitted himself with the greatest credit during the
three days of examination on Geology, Zoology, and Botany. I trust
that the Fellowship will continue to stimulate our eminent students
in future years.
Having been a student of Natural Science along with Dr. Falconer, I
feel a peculiar interest in doing what I can to promote the study
of a subject to which he so successfully devoted his energies.
In my endeavour to do so I have been encouraged by my friend and
former pupil, Mr. William Carruthers, at the head of the Botanical
Department of the British Museum, and a former student in Edinburgh
under the late Professor Fleming. He has done much to advance our
knowledge of Fossil Botany, and to him I am indebted for two of the
plates and some of the woodcuts which illustrate this publication.
He has given me most efficient assistance, and I have to return my
best thanks for his kind aid. I am also indebted to my colleague,
Professor Geikie, for his valued assistance.
The neighbourhood of Edinburgh is rich in Fossils of the
Carboniferous epoch, and much yet remains to be done to illustrate
its Palæontology. Such labourers as Geikie and Peach may be expected
to give great assistance in the furtherance of our knowledge of
Scottish Geology, so as to form a school which shall revive the
reputation enjoyed by Edinburgh in the days of Hutton and Jameson.
If I can be useful in encouraging students to take up the study of
Palæontological Botany, and to prosecute it with vigour, I shall feel
that this introductory treatise has not been issued in vain. As one
of the few surviving relations of Dr. James Hutton, I am glad to be
able to show an interest in a science which may aid in elucidating
the "Theory of the Earth."
In writing this work I have taken for granted that the reader is
acquainted with the Elements of Botany, and knows the general
structure of plants of the present day. I have not, therefore,
hesitated to use the ordinary Botanical terms without explanation. I
am satisfied that no one can study Fossil Botany properly unless he
has studied Modern Botany.
Those readers who may find any difficulty as to technical terms I
would refer to my Botanist's Companion, where a full Glossary is
given.
27 INVERLEITH ROW,
_May 1872_.
TABLE OF CONTENTS.
PAGE
INTRODUCTORY REMARKS 1
DETERMINATION OF FOSSIL PLANTS 3
MODE OF PRESERVATION OF FOSSIL PLANTS 8
EXAMINATION OF THE STRUCTURE OF FOSSIL PLANTS 12
FOSSILIFEROUS ROCKS 20
NATURAL ORDERS TO WHICH FOSSIL PLANTS BELONG 22
PERIODS OF VEGETATION AMONG FOSSIL PLANTS 25
FOSSIL FLORA OF THE PRIMARY OR PALÆZOIC PERIOD 26
REIGN OF ACROGENS 26
FLORA OF THE CARBONIFEROUS EPOCH 36
FLORA OF THE PERMIAN EPOCH 71
FOSSIL FLORA OF THE SECONDARY OR MESOZOIC PERIOD 72
REIGN OF GYMNOSPERMS 72
FLORA OF THE TRIAS AND LIAS EPOCHS 77
FLORA OF THE OOLITIC EPOCH 80
FLORA OF THE WEALDEN EPOCH 84
FOSSIL FLORA OF THE TERTIARY OR CAINOZOIC PERIOD (INCLUDING
THE CRETACEOUS EPOCH) 87
REIGN OF ANGIOSPERMS 87
FLORA OF THE CHALK 87
FLORA OF THE EOCENE EPOCH 90
FLORA OF THE MIOCENE EPOCH 92
FLORA OF THE PLIOCENE EPOCH 98
GENERAL CONCLUSIONS 101
RECAPITULATION 103
WORKS ON FOSSIL BOTANY 105
EXPLANATION OF PLATES 111
INDEX 113
LIST OF WOODCUTS.
FIG. PAGE
1. Section of Peuce Withami, Lindley and Hutton 3
2. Bark of Araucaria 5
3. Markings on Araucaria bark 6
4. " " 7
5. " " 7
6. Leaf of Araucaria 7
7. Nicolia Owenii (Carr.) 11
8. Bryson's instrument for slitting Fossils 14
9. Tree-fern 27
10. Asplenium 28
11 _a._ Bifurcating Trunk of a Tree-fern (Alsophila Perrottetiana) 29
11 _b._ Rhizome of Lastrea Filix-mas 29
12. Transverse section of stem of a Tree-fern (Cyathea) 29
13. Scalariform vessels from Tree-fern 30
14. Sporangia of a Fern 30
15. Lycopodium clavatum 30
16. Spore-case, containing Microspores of Lycopodium 30
17. " " Macrospores of Selaginella 30
18. Fructification of Equisetum maximum 31
19. Polygonal scale of Equisetum 32
20. Spore of Equisetum--filaments contracted 32
21. " " " expanded 32
22. Marsilea Fabri 33
22 _bis._ Adiantites Lindseæformis 41
23. Pecopteris (Alethopteris) aquiline 43
24. " (Alethopteris) heterophylla 43
25. Neuropteris Loshii 43
26. " gigantean 43
27. " acuminate 43
28. Sphenopteris affinis 43
29. Cyclopteris dilatata 43
30. Stem of Caulopteris macrodiscus 44
31. " " Balfouri (Carr.) 44
32. " " Morrisi (Carr.) 44
33. " Sigillaria pachyderma 45
34. Sigillaria reniformis 45
35. " pachyderma 46
36. " (Favularia) tessellate 46
37. " pachyderma 46
38. Stigmaria ficoides 47
39. " " (S. anabathra of Corda) 47
40. Bifurcating stem of Lepidodendron obovatum (elegans) 49
41. Stem of Lepidodendron crenatum 49
42. Fructification of Lepidodendron 50
43. Longitudinal section of Fructification of Triplosporites 50
44. (1). Fruit of Selaginella spinulosa, A. Braun (Lycopodium
selaginoides, Linn.) 51
(2). Scale and sporangium from the upper part of cone 51
(3). Antheridian microspores from ditto 51
(4). Macrospore 51
(5). Scale and sporangium from lower part of cone, containing
macrospores 51
(6). Fruit of Lepidostrobus ornatus (Hooker) 51
(7). Three scales and sporangia of ditto 51
(8). Microspores from sporangia of the upper part of the
cone of Triplosporites Brownii, Brongn. 51
(9). Macrospore from the sporangia of the lower part 51
(10). Scales and sporangia of a cone of Flemingites 51
45 _a._ Calamites Suckovii 57
45 _b._ Septum or Phragma of a Calamite 57
46. Vertical stems of Calamites--in coal-measures of Treuil,
near St. Etienne 58
47. Fruits of Equisetum and Calamites 60
(1). Equisetum arvense, L. 60
(2). Portion of sporangium wall 60
(3, 4). Spores--elaters free 60
(5). Longitudinal section of part of one side of cone 60
(6). Transverse section of cone 60
(7). Calamites (Volkmannia) Binneyi (Carr.) 60
(8). Portion of sporangium wall 60
(9). Two spores 60
(10). Longitudinal section of part of one side of cone 60
(11). Transverse section of cone 60
48. Foliage and fruits of Calamites 62
(1, 2). Asterophyllites 62
(3, 4). Annularia 62
(5, 6). Sphenophyllum 62
49. Araucarioxylon Withami, Krauss (Pinites Withami) 63
50. Trigonocarpum olivæforme 63
51. Cardiocarpum Lindleyi (Carr.) 65
52. " " 65
53. Cardiocarpum anomalum (Carr.) 66
54. Pothocites Grantoni (Paterson) 67
55, 56. Walchia piniformis (Sternb.) 72
57. Pinus sylvestris 73
58. Abies excelsa 73
59. Larix Europæa 73
60. Cedrus Libani 73
61. Araucaria excelsa 74
62. Woody tubes of fir--single rows of discs 74
63. " " --double and opposite rows of discs 74
64. Woody tubes of Araucaria excelsa--double and triple
and alternate rows of discs 74
65. Longitudinal section of stem of a Gymnosperm 74
66. Linear leaves of Pinus Strobus 75
67. Cone of Pinus sylvestris 75
68. " Cupressus sempervirens 75
69. Scale of mature cone of Pinus sylvestris 75
70. Fruiting branch of Juniperus communis 76
71. Branch of Taxus baccata 76
72. Male flower of Yew 76
73. Fruit of Yew 76
74. Cycas revoluta 77
75. Encephalartos (Zamia) pungens 77
76. Schizoneura heterophylla 78
77. Zamites 79
78. Pterophyllum Pleiningerii 80
79. Nilssonia compta (Pterophyllum comptum of Lindley
and Hutton) 80
80. Palæozamia pectinata (Zamia pectinata of Brongniart, and
Lindley and Hutton) 80
81. Brachyphyllum mammillare 81
82. Equisetum columnare 81
83. Araucarites sphærocarpus (Carr.) 82
84. Termination of a scale of ditto 82
85. Section of a scale of ditto 82
86. The Dirt-bed of the island of Portland 83
87. Cycadoidea megalophylla (Mantellia nidiformis of Brongniart) 83
88. Kaidacarpum ooliticum (Carr.) 84
89. Pandanus odoratissimus 84
90. Fossil wood, Abietites Linkii 85
91. Sequoiites ovalis 88
92. Pinites ovatus (Zamia ovata of Lindley and Hutton) 89
93. Palmacites Lamanonis 90
95. Comptonia acutiloba 92
96. Acer trilobatum 93
97. Ulmus Bronnii 93
98. Rhamnus Aizoon 94
99. Alnus gracilis 95
100. Taxites or Taxodites Campbellii 95
101. Rhamnites multinervatus 95
102. Equisetum Campbellii 96
PALÆONTOLOGICAL BOTANY.
The study of the changes which have taken place in the nature of
living beings since their first appearance on the globe till the
period when the surface of the earth, having assumed its present
form, has been covered by the creation which now occupies it,
constitutes one of the most important departments in Geology. It is,
as Brongniart remarks, the history of life and its metamorphoses.
The researches of geologists show clearly that the globe has
undergone various alterations since that "beginning" when "God
created the heavens and the earth." These alterations are exhibited
in the different stratified rocks which form the outer crust of the
earth, and which were chiefly sedimentary deposits produced by the
weathering of the exposed rocks. Remains of the plants and animals
living on the globe at the time of the formation of the different
beds are preserved in them. Elevations and depressions of the surface
of the earth affected the organisms on its surface, and gave to
successive deposits new faunas and floras. Some of these epochs have
been marked by great changes in the physical state of our planet,
and they have been accompanied with equally great modifications
in the nature of the living beings which inhabited it. The study
of the fossil remains of animals is called Palæozoology (παλαιός,
ancient, and ζῷον, animal), while the consideration of those of
vegetables is denominated Palæophytology (παλαιός and φυτόν, a plant).
Both are departments of the science of Palæontology, which has been
the means of bringing geology to its present state of advancement.
The study of these extinct forms has afforded valuable indications
as to the physical state of the earth, and as to its climate at
different epochs. This study requires the conjunct labours of the
Zoologist, the Botanist, and the Petralogist.
The vegetation of the globe, during the different stages of its
formation, has undergone very evident changes. At the same time there
is no reason to doubt that the plants may all be referred to the
great classes distinguished at the present day--namely, Thallogens,
including such plants as Lichens, Algæ, and Fungi; Acrogens, such
as Ferns and Lycopods; Gymnosperms, such as Cone-bearing plants and
Cycads; Endogens, such as Palms, Lilies, and Grasses; and Exogens,
such as the common trees of Britain (excluding the Fir), and the
great mass of ordinary flowering plants. The relative proportion of
these classes, however, has been different, and the predominance of
certain forms has given a character to the vegetation of different
epochs. The farther we recede in geological history from the present
day, the greater is the difference between the fossil plants and
those which now occupy the surface. At the time when the coal-beds
were formed, the plants covering the earth belonged to genera and
species not existing at the present day. As we ascend higher, the
similarity between the ancient and the modern flora increases, and in
the latest stratified rocks we have in certain instances an identity
in species and a considerable number of existing genera. At early
epochs the flora appears to have been uniform, to have presented less
diversity of forms than at present, and to have been similar in the
different quarters of the globe. The vegetation also indicates that
the nature of the climate was different from that which characterises
the countries in which these early fossil plants are now found.
DETERMINATION OF FOSSIL PLANTS.
[Illustration: Fig. 1.]
[Sidenote: Fig. 1. Section of _Peuce Withami_, after Lindley and
Hutton, a fossil Conifer of the coal epoch. Punctated woody tissue
seen.]
Fossil plants are by no means so easily examined as recent species.
They are seldom found in a complete state. Fragments of stems,
leaves, and fruits, are the data by which the plant is to be
determined. It is very rare to find any traces of the flowers. The
parts of fossil plants are usually separated from each other, and
it is difficult to ascertain what are the portions which should be
associated together so as to complete an individual plant. Specimens
are sometimes preserved, so that the anatomical structure of the
organs, especially of the stem, can be detected by very thin slices
placed under the microscope. In the case of some stems the presence
of punctated woody tissue (Fig. 1) has proved of great service as
regards fossil Botany; this structure, along with the absence of
large pitted ducts, serving to distinguish Conifers. The presence
of scalariform vessels indicates a plant belonging to the vascular
Cryptogams, of which the fern is the best known example. The cautions
to be observed in determining fossil plants are noticed by Dr. Hooker
in the Memoirs of the Geological Survey of Great Britain (vol. ii.
p. 387). At the present day, the same fern may have different forms
of fronds, which, unless they were found united, might be reckoned
distinct genera; and remarkable examples are seen in Niphobolus
rupestris and Lindsæa cordata. Moreover, we find the same form of
frond belonging to several different genera, which can only be
distinguished by the fructification; and as this is rarely seen in
fossil ferns, it is often impossible to come to a decided conclusion
in regard to them. A leaf of Stangeria paradoxa was considered
by an eminent botanist as a barren fern frond, but it ultimately
proved to be the leaf of a Cycad. The leaf of Cupania filicifolia,
a Dicotyledon, might easily be mistaken for that of a fern; it
resembles much the frond of a fossil fern called Coniopteris. The
diverse leaves of Sterculia diversifolia, if seen separately, might
easily be referred to different plants. In the same fern we meet
also with different kinds of venation in the fronds. Similar remarks
may be made in regard to other plants. Harvey has pointed out many
difficulties in regard to sea-weeds.
As regards the materials for a fossil flora, the following remarks of
Hugh Miller deserve attention:--
"The authors of Fossil Floras, however able or accomplished they may
be, have often to found their genera and species, and to frame their
restorations, when they attempt these, on very inadequate specimens.
For, were they to pause in their labours until better ones turned up,
they would find the longest life greatly too short for the completion
of even a small portion of their task. Much of their work must be
of necessity of a provisional character--so much so, that there are
few possessors of good collections who do not find themselves in
circumstances to furnish both addenda and errata to our most valuable
works on Palæontology. And it is only by the free communication of
these addenda and errata that geologists will be at length enabled
adequately to conceive of the by-past creations, and of that gorgeous
Flora of the Carboniferous age, which seems to have been by far the
most luxuriant and wonderful which our emphatically ancient earth
ever saw."
[Illustration: Fig. 2.]
[Sidenote: Fig. 2. Bark of _Araucaria imbricata_.]
The bark of trees at the present day often exhibits different kinds
of markings in its layers. This may be illustrated by a specimen of
Araucaria imbricata, which was destroyed by frost in the Edinburgh
Botanic Garden on 24th December 1861. The tree was 24½ feet high,
with a circumference of four feet at the base of the stem, and
had twenty whorls of branches. The external surface of the bark
is represented in Fig. 2. There are seen scars formed in part by
prolongations from the lower part of the leaves, which have been
cut off close to their union with the stem. The base of each leaf
remaining in the bark has the form of a narrow elongated ellipse,
surrounded by cortical foliar prolongations. The markings on the
bark, when viewed externally, have a somewhat oblique quadrilateral
form. On removing the epiphlœum or outer bark, and examining its
inner surface, we remark a difference in the appearance presented
at the lower and upper part of the stem. In the lower portion the
markings have an irregular elliptical form, with a deep depression,
and fissures where the leaves are attached (Fig. 3). Higher up the
epiphlœal markings assume rather more of a quadrilateral form, with
the depressions less deep, and the fissures for the leaves giving off
prolongations on either side. Farther up the markings are smaller in
size, obliquely quadrilateral, and present circular clots along the
boundary lines chiefly (Fig. 4). Higher still the quadrilateral form
becomes more apparent, and the dots disappear (Fig. 5). The epiphlœum
thus presents differences in its markings at different heights on the
stem.
[Illustration: Fig. 3.]
[Illustration: Fig. 4.]
[Illustration: Fig. 5.]
[Sidenote: Figs. 3, 4, and 5. Markings on Araucaria bark.]
The part of the bark immediately below the epiphlœum is well
developed, and is of a spongy consistence. When examined
microscopically it is seen to be composed of cells of various
shapes--some elongated fusiform, others rhomboidal, others with
pointed appendages. The variety of forms is very great, but it is
possible that this may be partly owing to the effects of frost on the
cells. On the spontaneous separation of the bark, the portion below
the epiphlœum was seen to consist of distinct plates of a more or
less quadrilateral form, with some of the edges concave and others
convex, a part in the centre indicating the connection with the leaf,
along with which it is detached. In Fig. 6 a leaf is shown with one
of these plates attached.
[Illustration: Fig. 6.]
[Sidenote: Fig. 6. Leaf of Araucaria with a portion of bark.]
The appearances presented by the outer and middle bark of Araucaria
imbricata bear a marked resemblance to those exhibited by certain
fossils included in the genera Sigillaria and Lepidodendron. The
sculpturesque markings on the stems of these fossil plants indicate
their alliance to the ferns and lycopods of the present epoch. But
it is evident, from these markings, that much caution is required
in making this determination. Other points of structure must be
examined before a proper decision can be formed. When, for instance,
the presence of scalariform tissue, or of punctated woody tissue,
has been satisfactorily shown under the microscope, we are entitled
to hazard an opinion as to the affinities of the fossils. In many
instances, however, external appearances are the only data on which
to rely for the determination of fossil genera and species; and rash
conclusions have often been drawn by geologists who have not been
conversant with the structure of plants. The Araucaria markings point
out the need of care in drawing conclusions, and their variations at
different parts of the bark indicate the danger of a rash decision
as to species. There can be no doubt that in vegetable Palæontology
the number of species has been needlessly multiplied--any slight
variation in form having been reckoned sufficient for specific
distinction. We can conceive that the Araucaria bark markings in a
fossil state might easily supply several species of Lepidodendron.
A naturalist, with little knowledge of the present flora of the
globe, ventures sometimes to decide on an isolated fragment. Hence
the crude descriptions of fossil vegetable forms, and the confusion
in which Palæophytology is involved. Every geologist who examines
fossil plants ought to be well acquainted with the minute structure
of living plants, the forms of their roots, stems, leaves, fronds,
and fructification; the markings on the outer and inner surfaces of
their barks, on their stems, and on their rhizomes; the localities in
which they grow, and the climates which genera and species affect in
various parts of the world. (Professor Balfour in the Proceedings of
the Royal Society of Edinburgh, April 1862, vol. iv. p. 577.)
MODE OF PRESERVATION OF FOSSIL PLANTS.
The mode in which plants are preserved in a fossil state may be
referred to four principal classes:--1. Casts of the plants; from
which all the original substance and structure have been removed
subsequently to the burial of the plants, and to the greater or
less induration of the rocks in which they are entombed. Such casts
are occasionally hollow, but more frequently they consist of the
amorphous substance of the rock which has filled up the cavity,
and which exhibits, often with remarkable minuteness, the external
aspects of the original specimen. 2. Carbonisation; in which the
original substance of the plant has been chemically altered and
converted into lignite or coal. All trace of the form of the original
plant is generally lost, as is the case with the extensive beds of
coal; but frequently, when the organism has been buried in a bed of
clay, the external appearance is faithfully preserved, as in the
ferns and other foliage found in the shales of the coal-measures.
3. Infiltration; in which the vegetable tissues, though carbonised,
retain their original form from the infiltration of some mineral in
solution, chiefly lime or silex, which has filled the empty cells
and vessels, and so preserved their original form. This mode of
preservation occurs in the calcareous nodules in coal-beds, in the
remarkable ash-beds discovered by Mr. Wünsch in Arran, and generally
in the secondary rocks. 4. Petrifaction; in which the structure is
preserved, but the whole of the original substance has been replaced,
atom for atom, by an inorganic substance, generally lime, silex, or
some ore of iron. This is the condition of the beautiful fossils
from Antigua, and of many stems and fruits from rocks of all ages in
Britain.
Carbonised vegetables, or those which have passed into the state
of Lignites, often undergo modifications which render it difficult
to understand them rightly. Sometimes a portion of the organs of
vegetables which have passed into the state of lignite is transformed
into pyrites, or else pyrites of a globular shape is found in
the middle of the tissue, and may be taken for a character of
organisation. The section of certain Dicotyledonous fossil woods, in
that case, may resemble Monocotyledons. Petrifaction, as in the case
of silicified woods, often preserves all the tissues equally, at
other times the soft tissues are altered or destroyed; the cellular
tissue being replaced by amorphous chalcedony, while the ligneous
and vascular tissues alone are petrified, so as to preserve their
forms. In some cases the reverse takes place as to these tissues;
the fibrous portions disappear, leaving cavities, while the cells
are silicified. Sometimes we find the parts regularly silicified
at one place, so as to retain the structure, while at another an
amorphous mass of silica is found. In such cases there appear,
as it were, distinct silicified woody bundles in the midst of an
amorphous mass. The appearance depends, however, merely on irregular
silicification or partial petrifaction. Infiltrated fossil woods, by
means of chemical tests, are shown to possess portions of vegetable
tissues cemented into a mass by silica. In some cases we find the
vessels and cells separately silicified, without being crushed into a
compact mass. In these cases, the intercellular substance not being
silicified, the mass breaks down easily; whereas, when complete
silicification takes place, the mass is not friable. Coniferous wood
is often friable, from silicified portions being still separated
from each other by vegetable tissue more or less entire. During
silicification, or subsequent to it, it frequently happens that
the plant has been compressed, broken, and deformed, and that
fissures have been formed which have been subsequently filled with
crystallised or amorphous silica.
[Illustration: Fig. 7.]
[Sidenote: Fig. 7. _Nicolia Owenii_ (Carr.), from the Tertiary Strata
of Egypt.]
Silicified stems of trees have been observed in various parts of
the world, with their structure well preserved, so that their
Endogenous and Exogenous character could be easily determined. The
Rev. W. B. Clarke notices the occurrence of a fossil pine-forest
at Kurrur-Kurrân, in the inlet of Awaaba, on the eastern coast of
Australia. In the inlet there is a formation of conglomerate and
sandstone, with subordinate beds of lignite--the lignite forming
the so-called Australian coal. Throughout the alluvial flat, stumps
and stools of fossilised trees are seen standing out of the ground,
and one can form no better notion of their aspect than by imagining
what the appearance of the existing living forest of Eucalypti and
Casuarinæ would be if the trees were all cut down to a certain level.
In a lake in the vicinity there are also some fossilised stumps of
trees, standing vertically. In Derwent Valley, Van Diemen's Land,
fossil silicified trees, in connection with trap rocks, have been
found in an erect position. One was measured with a stem 6 feet high,
a circumference at the base of 7 feet 3 inches, and a diameter at the
top of 15 inches. The stems are Coniferous, resembling Araucaria. The
outer portion of the stem is of a rich brown glossy agate, while the
interior is of a snowy whiteness. One hundred concentric rings have
been counted. The tissue falls into a powdery mass. Silica is found
in the inside of the tubes, and their substance is also silicified.
The erect silicified stems of coniferous trees exist in their natural
positions in the "dirt-bed," an old surface soil in the sandstone
strata of the Purbeck series in the Isle of Portland, Dorsetshire. In
the petrified forests near Cairo silicified stems have been examined
by Brown, Unger, and Carruthers. They belong to dicotyledonous trees
(not coniferous), to which the names of Nicolia Ægyptiaca and Nicolia
Owenii (Fig. 7) have been given. The wood consists of a slender
prosenchyma, abundantly penetrated by large ducts. The walls of the
ducts are marked by small, regularly arranged, oval, and somewhat
compressed hexagonal reticulations. The ducts have transverse
diaphragms. There are numerous medullary rays. The wood in their
stems is converted into chalcedony. (Carruthers on Petrified Forest
near Cairo. Geol. Mag., July 1870.)
EXAMINATION OF THE STRUCTURE OF FOSSIL PLANTS.
When the structure of fossil plants is well preserved, it may be
seen under the microscope by making thin sections after the mode
recommended by Mr. William Nicol, the inventor of the prism which
bears his name, and to whose memory Unger dedicated the genus
Nicolia, which has just been described as constituting the petrified
forest at Cairo. The following is a description of the process of
preparing fossils for the microscope, by Mr. Alexander Bryson. (Edin.
N. Phil. Journal, N. S. iii. 297. Balfour's Botanist's Companion, p.
30.)
"The usual mode of proceeding in making a section of fossil wood is
simple, though tedious. The first process is to flatten the specimen
to be operated on by grinding it on a flat _lap_ made of lead charged
with emery or corundum powder. It must now be rendered perfectly flat
by hand on a plate of metal or glass, using much finer emery than in
the first operation of grinding. The next operation is to cement the
object to the glass plate. Both the plate of glass and the fossil
to be cemented must be heated to a temperature rather inconvenient
for the fingers to bear. By this means moisture and adherent air are
driven off, especially from the object to be operated on. Canada
balsam is now to be equally spread over both plate and object, and
exposed again to heat, until the redundant turpentine in the balsam
has been driven off by evaporation. The two surfaces are now to be
connected while hot, and a slow circular motion, with pressure, given
either to the plate or object, for the purpose of throwing out the
superabundant balsam and globules of included air. The object should
be below and the glass plate above, as we then can see when all the
air is removed, by the pressure and motion indicated. It is proper
to mention that too much balsam is more favourable for the expulsion
of the air-bubbles than too little. When cold, the Canada balsam
will be found hard and adhering, and the specimen fit for slitting.
This process has hitherto been performed by using a disc of thin
sheet-iron, so much employed by the tinsmith, technically called
_sheet-tin_. The tin coating ought to be partially removed by heating
the plate, and when hot rubbing off much of the extraneous tin by a
piece of cloth. The plate has now to be planished on the polished
_stake_ of the tinsmith, until quite flat. If the plate is to be
used in the lathe, and by the usual method, it ought to be planished
so as to possess a slight convexity. This gives a certain amount
of rigidity to the edge, which is useful in slitting by the hand;
while by the method of mechanical slitting, about to be described,
this convexity is inadmissible. The tin plate, when mounted on an
appropriate chuck in the lathe, must be turned quite true, with its
edge slightly rounded and made perfectly smooth by a fine-cut file.
The edge of the disc is now to be charged with diamond powder. This
is done by mingling the diamond powder with oil, and placing it on a
piece of the hardest agate, and then turning the disc slowly round.
Then, by holding the agate with the diamond powder with a moderate
pressure against the edge of the disc, it is thoroughly charged with
a host of diamond points, becoming, as it were, a saw with invisible
teeth. In pounding the diamond, some care is necessary, as also a
fitting mortar. The mortar should be made of an old steel die, if
accessible; if not, a mass of steel, slightly conical, the base of
which ought to be 2 inches in diameter, and the upper part 1½ inch.
A cylindrical hole is now to be turned out in the centre, of ¾ths of
an inch diameter, and about 1 inch deep. This, when hardened, is the
mortar; for safety it may be annealed to a straw colour. The pestle
is merely a cylinder of steel, fitting the hollow mortar but loosely,
and having a ledge or edging of an eighth of an inch projecting round
it, but sufficiently raised above the upper surface of the mortar, so
as not to come in contact while pounding the diamond. The point of
the pestle ought only to be hardened and annealed to a straw colour,
and should be of course convex, fitting the opposing and equal
concavity of the mortar. The purpose of the projecting ledge is to
prevent the smaller particles of diamond spurting out when the pestle
is struck by the hammer."
[Illustration: Fig. 8.]
[Sidenote: Fig. 8. Mr. Bryson's instrument for slitting fossils. A
very simple slicing and polishing machine has been invented by Mr. J.
B. Jordan of the Mining Record Office, and is sold by Messrs. Cotton
and Johnson, Grafton Street, Soho, London. It costs about £10.]
Mr. Bryson has contrived an instrument for slitting fossils. The
instrument is placed on the table of a common lathe, which is, of
course, the source of motion (Fig. 8). It consists of a Watt's
parallel motion, with four joints, attached to a basement fixed
to the table of the lathe. This base has a motion (for adjustment
only) in a horizontal plane, by which we may be enabled to place the
upper joint in a parallel plane with the spindle of the lathe. This
may be called the azimuthal adjustment. The adjustment, which in
an astronomical instrument is called the plane of right ascension,
is given by a pivot in the top of the base, and clamped by a screw
below. This motion in right ascension gives us the power of adjusting
the perpendicular planes of motion, so that the object to be slit
passes down from the circumference of the slitting-plate to nearly
its centre, in a perfectly parallel plane. When this adjustment
is made accurately, and the slitting-plate well primed and flat,
a very thin and parallel slice is obtained. This jointed frame is
counterpoised and supported by a lever, the centre of which is
movable in a pillar standing perpendicularly from the lathe table.
Attached to the lever is a screw of three threads, by which the
counterpoise weight is adjusted readily to the varying weight of the
object to be slit and the necessary pressure required on the edge of
the slitting-plate.
The object is fixed to the machine by a pneumatic chuck. It consists
of an iron tube, which passes through an aperture on the upper
joint of the guiding-frame, into which is screwed a round piece of
gun-metal, slightly hollowed in the centre, but flat towards the
edge. This gun-metal disc is perforated by a small hole communicating
with the interior of the iron tube. This aperture permits the air
between the glass plate and the chuck to be exhausted by a small
air-syringe at the other end. The face of this chuck is covered with
a thin film of soft india-rubber not vulcanised, also perforated with
a small central aperture. When the chuck is properly adjusted, and
the india-rubber carefully stretched over the face of the gun-metal,
one or two pulls of the syringe-piston is quite sufficient to
maintain a very large object under the action of the slitting-plate.
By this method no time is lost; the adhesion is made instantaneously,
and as quickly broken by opening a small screw, to admit air between
the glass plate and the chuck, when the object is immediately
released. Care must be taken, in stretching the india-rubber over the
face of the chuck, to make it very equal in its distribution, and as
thin as is consistent with strength. When this material is obtained
from the shops, it presents a series of slight grooves, and is rather
hard for our purpose. It ought, therefore, to be slightly heated,
which renders it soft and pliant, and in this state should now be
stretched over the chuck, and a piece of soft copper wire tied round
it, a slight groove being cut in the periphery of the chuck to detain
the wire in its place. When by use the surface of the india-rubber
becomes flat, smooth, and free from the grooves which at first mar
its usefulness, a specimen may be slit of many square inches, without
resort being had to another exhaustion by the syringe. But when a
large, hard, siliceous object has to be slit, it is well for the
sake of safety to try the syringe piston, and observe if it returns
forcibly to the bottom of the cylinder, which evidences the good
condition of the vacuum of the chuck.
After the operation of slitting, the plate must be removed from
the spindle of the lathe, and the flat lead _lap_ substituted. The
pneumatic chuck is now to be reversed, and the specimen placed in
contact with the grinder. By giving a slightly tortuous motion to
the specimen, that is, using the motion of the various joints, the
object is ground perfectly flat when the length of both arms of the
joints is perfectly equal. Should the leg of the first joint on the
right-hand side be the longer, the specimen will be ground hollow; if
shorter, it will be ground convex. But if, as before stated, they are
of equal length, a perfectly parallel surface will be obtained.
In operating on siliceous objects, I have found soap and water
quite as speedy and efficacious as oil, which is generally used;
while calcareous fossils must be slit by a solution of common soda
in water. This solution of soda, if made too strong, softens the
india-rubber on the face of the pneumatic chuck, and renders a
new piece necessary; but if care is taken to keep the solution of
moderate strength, one piece of india-rubber may last for six months.
The thinner and flatter it becomes, the better hold the glass takes,
until a puncture occurs in the outer portion, and a new piece is
rendered necessary.
The polishing of the section is the last operation. This is performed
in various ways, according to the material of which the organism is
composed. If siliceous, a _lap_ of tin is to be used, about the same
size as the grinding _lap_. Having turned the face smooth and flat, a
series of very fine notches are to be made all over the surface. This
operation is accomplished by holding the edge of an old dinner-knife
almost perpendicular to the surface of the _lap_ while rotating;
this produces a series of _criddles_, or slight asperities, which
detain the polishing substance. The polishing substance used on the
tin lap is technically called lapidaries' rot-stone, and is applied
by slightly moistening the mass, and pressing it firmly against
the polisher, care being taken to scrape off the outer surface,
which often contains grit. The specimen is then to be pressed with
some degree of force against the revolving tin _lap_ or polisher,
carefully changing the plane of action, by moving the specimen in
various directions over the surface.
To polish calcareous objects, another method must be adopted as
follows:--
A _lap_ or disc of willow wood is to be adapted to the spindle of the
lathe, three inches in thickness, and about the diameter of the other
laps (10 inches), the axis of the wood being parallel to the spindle
of the lathe, that is, the acting surface of the wood is the end of
the fibres, the section being transverse.
This polisher must be turned quite flat and smoothed by a plane, as
the willow, from its softness, is peculiarly difficult to turn. It
is also of consequence to remark that both sides should be turned,
so that the _lap_, when dry, is quite parallel. This _lap_ is most
conveniently adapted to the common face chuck of a lathe with a
conical screw, so that either surface may be used. This is made
evident, when we state that this polisher is always used moist, and,
to keep both surfaces parallel, must be entirely plunged in water
before using, as both surfaces must be equally moist, otherwise the
dry surface will be concave and the moist one convex. The polishing
substance used with this _lap_ is putty powder (oxide of tin), which
ought to be well washed, to free it from grit. The calcareous fossils
being finely ground, are speedily polished by this method. To polish
softer substances, a piece of cloth may be spread over the wooden
_lap_, and finely-levigated chalk used as a polishing medium.
In order to study fossil plants well, there must be an acquaintance
with systematic botany, a knowledge of the microscopical structure
of all the organs of plants, such as their roots, stems, barks,
leaves, fronds, and fruit; of the markings which they exhibit on
their different surfaces, and of the scars which some of them
leave when they decay. It is only thus we can expect to determine
accurately the living affinities of the fossil. Brongniart says,
that before comparing a fossil vegetable with living plants, it is
necessary to reconstruct as completely as possible the portion of
the plant under examination, to determine the relations of these
portions to the other organs of the same plant, and to complete the
plant if possible, by seeing whether, in the fossils of the same
locality, there may not be some which belong to the same plant. The
connection of the different parts of the same plant is one of the
most important problems in Palæophytology, and the neglect of it has
led to many mistakes. In some instances the data have been sufficient
to enable botanists to refer a fossil plant to a genus of the present
day, so that we have fossil species of the genera Ulmus, Alnus,
Pinus, etc. Sometimes the plant is shown to be allied to a living
genus, but differing in some essential point, or wanting something to
complete the identity, and it is then marked by the addition of the
term _ites_, as Pinites, Thuites, Zamites, etc.
Before drawing conclusions as to the climate or physical condition
of the globe at different geological epochs, the botanist must be
well informed as to the vegetation of different countries, as to the
soils and localities in which certain plants grow, whether on land
or in the sea, or in lakes, in dry or marshy ground, in valleys or
on mountains, or in estuaries, in hot, temperate, or cold regions.
Great caution must be employed also in predicating from one species
the conditions of another, inasmuch as different species of the
same genus frequently exist in very different habitats, and under
almost opposite conditions of moisture and temperature. It is
only by a careful consideration of all these particulars that any
probable inferences can be drawn as to the condition of the globe.
Considering the physiognomy of vegetation at the present day, we
find remarkable associations of forms. The Palms, although generally
characteristic of very warm countries, are by no means confined to
them; Chamærops humilis extending to Europe as far as lat. 43° to 44°
N., and C. palmetto in North America to lat. 34° to 36° N., while
C. Fortunei, from the north of China, is perfectly hardy in the
south of England. Major Madden mentions the association of Palms and
Bamboos with Conifers at considerable elevations on the Himalayas.
(Edin. Bot. Soc. Trans. iv., p. 185.) Epiphytic Orchids, which
usually characterise warm climates, have representatives at great
elevations, as Oncidium nubigenum at 14,000 feet in the Andes, and
Epidendrum frigidum at from 12,000 to 13,000 feet in the Columbia
mountains. These facts point out the care necessary before drawing
conclusions as to the climate which fossil plants may be supposed to
indicate.
FOSSILIFEROUS ROCKS.
The rocks of which the globe is composed are divided into two
great classes--the Stratified or Aqueous, and the Unstratified or
Igneous. The stratified rocks frequently contain fossil remains,
and are then called fossiliferous; those with no such remains are
designated non-fossiliferous or azoic. The igneous unstratified
rocks, included under the names of Granitic and Trappean, show no
appearance of animal or vegetable remains. Those trap rocks, however,
which have been formed of loose volcanic ashes have often enclosed
and preserved the remains of plants and animals; while even between
the successive beds of old lava-like trap rocks organic remains are
sometimes found. Thus, in Antrim, near the Giant's Causeway, deposits
containing vegetable remains occur inter-stratified with basaltic
rocks. These remains are of Miocene age, and have been referred to
coniferous plants, beeches, oaks, plane trees, etc. Similar plants
have been discovered in a similar position by the Duke of Argyll
in the island of Mull. In trap rocks near Edinburgh, lignite with
distinct structure has also been detected. Silicified wood and coal,
imbedded in trap rocks, have been seen in Kerguelen's Land. The wood
is found enclosed in basalt, whilst the coal crops out in ravines,
in close contact with the overlying porphyritic and amygdaloidal
greenstone. Hooker has also seen silicified wood, in connection with
trap, in Macquarrie's Plains, in Tasmania. Several beds of trap-tuff
or ash, formed into solid compact rock by infiltrated carbonate of
lime, occur in the north-east of Arran, which contain numerous stems,
branches, and fruits of carboniferous plants. These represent the
remains of successive forests which grew on this locality, and were
one after the other destroyed by the ash-showers poured forth from a
neighbouring volcano during its intermittent periods of activity.
Fossil remains are extremely rare in certain rocks, which, from the
changes they have undergone, have been denominated Metamorphic.
These include Gneiss and Mica-slate, which are stratified rocks
subsequently altered by heat and other causes, and so completely
metamorphosed that the traces of organisms have been nearly
obliterated. Nevertheless, recognisable traces of plant and animal
remains have been found in what were recently thought to be azoic
rocks. The absence of organic remains in rocks is therefore not
sufficient to enable us to state that these rocks were formed before
animals or vegetables existed.
The stratified rocks which contain fossils have been divided into
three great groups--the Palæozoic, the Secondary, and the Tertiary,
or into Palæozoic and Neozoic groups. The formations included under
these are exhibited in the following table, taken from Lyell's Manual
of Geology:--
1. Recent. } Post Tertiary. } Recent.
2. Post Pliocene. } }
3. Newer Pliocene. } Pliocene. }
4. Older Pliocene. } }
}
5. Upper Miocene. } Miocene. } Tertiary }
6. Lower Miocene. } } or }
} Cainozoic. }
7. Upper Eocene. } } }
8. Middle Eocene. } Eocene. } }
9. Lower Eocene. } } }
} Neozoic.
10. Maestricht Beds. } } }
11. White Chalk. } } }
12 Chloritic Series. } } Secondary }
13. Gault } Cretaceous. } or }
14. Neocomian. } } Mesozoic. }
15. Wealden. } } }
16. Purbeck Beds. } } }
17. Portland Stone. } } }
18. Kimmeridge Clay. } } }
19. Coral Rag. } Jurassic. } }
20. Oxford Clay. } } Secondary }
21. Great or Bath Oolite. } } or } Neozoic.
22. Inferior Oolite. } } Mesozoic. }
23. Lias. } } }
} }
24. Upper Trias. } } }
25. Middle Trias. } Triassic. } }
26. Lower Trias. } } }
27. Permian. Permian. }
28. Coal Measures. } }
29. Carboniferous } Carboniferous. }
limestone. } }
}
30. Upper } { Devonian or }
31. Middle } Devonian. { Old Red } }
32. Lower } { Sandstone. } Primary }
} or } Palæozoic.
33. Upper } } Palæozoic. }
34. Lower } Silurian. Silurian. }
}
35. Upper } }
36. Lower } Cambrian. Cambrian. }
}
37. Upper } }
38. Lower } Laurentian. Laurentian. }
NATURAL ORDERS TO WHICH FOSSIL PLANTS BELONG.
The plants found in different strata are either terrestrial or
aquatic, and the latter exhibit species allied to the salt and fresh
water vegetables of the present day. Their state of preservation
depends much on their structure. Cellular plants have probably in a
great measure been destroyed, and hence their rarity; while those
having a woody structure have been preserved. The following is the
number of fossil genera and species, as compiled from Unger's work on
Palæophytology--(Unger, Genera et Species Plantarum Fossilium, 1850).
DICOTYLEDONES. Genera. Species.
Thalamifloræ. 24 84
Calycifloræ 56 182
Corollifloræ 23 60
Monochlamydeæ Angiospermæ 48 221
------------- Gymnospermæ 56 363
MONOCOTYLEDONES.
Petaloideæ 38 130
Glumiferæ 5 12
ACOTYLEDONES.
Thallogenæ 31 203
Acrogenæ 121 969
Doubtful 35 197
---- ----
437 2421
These plants are arranged in the different strata as follows:--
{Cambrian, Silurian, and Devonian 73
Palæozoic {Carboniferous 683
{Permian 97
{Triassic 115
Mesozoic {Jurassic 294
{Cretaceous 183
{Eocene 414
Cainozoic {Miocene 496
{Pliocene 35
Recent Post-Pliocene 31
----
Fossil Species. 2421
During the twenty years that have elapsed since this enumeration was
made, the number of fossil species has been very greatly increased.
The proportion exhibited in this table is likewise greatly altered
from the enormous additions made to the Tertiary Flora by Unger,
Ettingshausen, and Heer, and from the important contributions by
Principal Dawson to the Devonian Flora.
Among the fossil Thalamifloral Dicotyledons, Unger mentions species
belonging to the orders--
Magnoliaceæ.
Anonaceæ.
Nymphæaceæ.
Capparidaceæ.
Malvaceæ.
Byttneriaceæ.
Tiliaceæ.
Aurantiaceæ.
Malpighiaceæ.
Aceraceæ.
Sapindaceæ.
Cedrelaceæ.
Zygophyllaceæ.
Xanthoxylaceæ.
Coriariaceæ.
Among Calycifloral Dicotyledons--
Celastraceæ.
Rhamnaceæ.
Anacardiaceæ.
Amyridaceæ.
Leguminosæ.
Rosaceæ.
Calycanthaceæ.
Combretaceæ.
Melastomaceæ.
Myrtaceæ.
Halorageaceæ.
Cucurbitaceæ.
Cornaceæ.
Loranthaceæ.
Rubiaceæ.
Among Corollifloral Dicotyledons--
Ericaceæ.
Styracaceæ.
Ebenaceæ.
Aquifoliaceæ.
Sapotaceæ.
Oleaceæ.
Apocynaceæ.
Gentianaceæ.
Among Monochlamydeous Angiosperms--
Nyctaginaceæ.
Lauraceæ.
Proteaceæ.
Aquilariaceæ.
Samydaceæ.
Santalaceæ.
Euphorbiaceæ.
Urticaceæ.
Artocarpaceæ.
Ceratophyllaceæ.
Salicaceæ.
Myricaceæ.
Betulaceæ.
Altingiaceæ.
Platanaceæ.
Corylaceæ.
Juglandaceæ.
Rafflesiaceæ.
Among Monochlamydeous Gymnosperms--
Coniferæ.
Taxaceæ.
Gnetaceæ.
Cycadaceæ.
Among Petaloid Monocotyledons--
Smilaceæ.
Orchidaceæ.
Zingiberaceæ.
Musaceæ.
Liliaceæ.
Palmæ.
Pandanaceæ.
Araceæ.
Typhaceæ.
Naiadaceæ.
Restiaceæ.
Among Glumiferous Monocotyledons--
Cyperaceæ.
Gramineæ.
Among Acrogenous Acotyledons--
Filices.
Marsileaceæ.
Lycopodiaceæ.
Equisetaceæ.
Musci.
Hepaticæ.
Among Thallogenous Acotyledons--
Lichenes.
Characeæ.
Algæ.
Fungi.
PERIODS OF VEGETATION AMONG FOSSIL PLANTS.
On taking a general survey of the known fossil plants, Brongniart
thought that he could trace three periods of vegetation,
characterised by the predominance of certain marked forms of
plants. In the ancient period there is a predominance of Acrogenous
Cryptogamic plants; this is succeeded by a period in which there is
a preponderance of Gymnospermous Dicotyledons; while a third period
is marked by the predominance of Angiospermous Dicotyledons. There
is thus--1. The reign of Acrogens, which includes the plants of the
Devonian, Carboniferous, and Permian periods. During these periods
there seems to be a predominance of Ferns, and a great development of
arborescent Lycopodiaceæ, such as Lepidodendron and Sigillaria, and
with them are associated some Gynmosperms, allied to Araucaria, and
some anomalous plants, as Noeggerathia. 2. The reign of Gymnosperms,
comprehending the Triassic and Jurassic periods. Here we meet with
numerous Coniferæ and Cycadaceæ, while Ferns are less abundant. 3.
The reign of Angiosperms, embracing the Cretaceous and the Tertiary
periods. This is characterised by the predominance of Angiospermous
Dicotyledons, a class of plants which constitute more than
three-fourths of the present vegetable productions of the globe, and
which appear to have acquired a predominance from the commencement of
the Tertiary formations. These plants appear sparingly even at the
beginning of the chalk formation in Europe, but are more abundant in
this formation as developed in North America.
FLORA OF THE PRIMARY OR PALÆOZOIC PERIOD.
REIGN OF ACROGENS.
In the present day, acrogenous plants are represented by cellular
and vascular Cryptogams. In considering fossil plants our attention
is specially directed to the latter. In the recent Floras, vascular
Acrogens are represented by such plants as Ferns, Lycopods, and
Equisetums. Some of them have an arborescent habit, but the greater
number are shrubby and herbaceous. Many of them have creeping
rhizomes, which are either subterranean, or run along the surface
of the ground. One of these arborescent forms is seen in Tree-ferns
(Fig. 9). Another form with a rhizome is seen in Fig. 10. The trunks
of ferns are marked by scars, which indicate the parts where the
bases of the fronds were attached, and where the vascular tissue
passes out from the interior (Fig. 11, _a_ and _b_). A transverse
section of the stem (Fig. 12) shows a continuous cylinder of
scalariform vessels (Fig. 13), enclosing a large mass of cellular
tissue frequently penetrated by small scalariform bundles. The
cylinder is pierced by meshes, from the inner sides of which rise the
vascular bundles going to the leaves, while some of the free bundles
of the axis pass through the mesh, carrying with them a portion of
the cellular tissue into the petiole. The fructification consists
of spore-cases (sporangia), often with an elastic ring round them,
containing spores in their interior (Fig. 14).
[Illustration: Fig. 9.]
[Sidenote: Fig. 9. Tree-fern, with a slender cylindrical trunk and a
crown of drooping fronds. It is a vascular acrogen.]
[Illustration: Fig. 10.]
[Sidenote: Fig. 10. _Asplenium_; a species of Spleenwort. A. Rhizome,
_r_, covered with the bases (stalks or stipes) of the fronds; _f_,
fronds in bud, rolled up in a circinate manner (this is very rarely
seen in fossil ferns); _g_, fronds bearing fructification on their
backs. B. Portion of a frond separated to show the linear sori or
clusters of sporangia (spore-cases).]
Among Acrogens of the present day there are also plants belonging
to the natural order Lycopodiaceæ or Club-mosses (Fig. 15), having
creeping stems, which give rise to leafy branches. The leaves are
small, sessile, and moss-like, and the fructification consists of two
kinds of cellular bodies, small spores or microspores (Fig. 16),
and large spores or macrospores (Fig. 17). They consist of cellular
and vascular tissues, the latter occurring in the form of woody,
annular, and scalariform vessels, which occupy the axis or central
part of the stem. They differ from ferns in the distribution of
their vascular bundles. The order is represented also by such plants
as Selaginella, Psilotum, Phylloglossum, and Isoetes. In the plant
called Isoetes (Quillwort) there is a peculiar short stem which does
not increase in height. It produces additions laterally, so that the
stem increases in thickness. The leaves continue to multiply, and
bear fructification at their bases. They have both large and small
spores.
[Illustration: Fig. 11, _a_. Fig. 11, _b_. Fig. 12.]
[Sidenote: Fig. 11, _a_. Bifurcating (forked or dichotomous) trunk
(caudex) of a Tree-fern (_Alsophila Perrottetiana_), showing the
scars (cicatrices) left by the fallen fronds. These scars exhibit
the arrangement of the vascular bundles. Fig. 11, _b_. Rhizome of
_Lastrea Filix-mas_ (male fern), showing scars of the leaves, _c_,
with markings of the vascular bundles.]
[Sidenote: Fig. 12. Transverse section of the stem (caudex) of a
Tree-fern (_Cyathea_), showing the arrangement of the cellular and
vascular tissue. The cellular tissue of the centre, _m_; that of
the circumference, _p_; vascular cylinder, _f v_, consisting of
dark-coloured pleurenchyma or ligneous tubes, _f_, and paler vessels,
_v_, chiefly scalariform and closed spiral, and pierced by the meshes
for the leaf-bundles at _m_; the outer cortical portion connected
with the bases of the leaves, _e_.]
[Illustration: Fig. 13-17.]
[Sidenote: Fig. 13. Scalariform vessels taken from a Tree-fern. They
are marked with bars like the steps of a ladder, hence their name.
The membrane occasionally disappears, so that the walls are made up
of fibres only at some parts.
Fig. 14. Sporangia of a Fern, supported on stalks, _p_, each of which
ends in an elastic cellular ring, _s_, partially surrounding the
spore-case, and opening it when mature.
Fig. 15. _Lycopodium clavatum_, a common Club-moss. The leafy branch,
_l_, ends in a stalk bearing two spikes of fructification, _f_.
Fig. 16. A kidney-shaped 2-valved case, containing small spores
(microspores) of Lycopodium.
Fig. 17. Two-valved case, containing large spores (macrospores) of
Selaginella.]
[Illustration: Fig. 18.]
[Sidenote: Fig. 18. Fructification of _Equisetum maximum_, Great
Water Horse-tail, showing the stalk surrounded by membranous sheaths,
_s s_, which are fringed by numerous processes called teeth. The
fructification, _f_, at the extremity, is in the form of a cone
bearing polygonal scales, under which are spore-cases containing
spores with filaments.]
Another important order of vascular Acrogens is the Equisetaceæ
or Horse-tails (Fig. 18). These are Cryptogams, having rhizomes,
bearing hollow, striated branches, which secrete in their epidermis
a considerable amount of silex. These branches are jointed and have
membranous sheaths at the articulations, which are whorls of leaves
reduced to a very rudimentary condition. The fructification consists
of cone-like bodies (Fig. 18, _f_) bearing peltate polygonal scales,
under which are spore-cases (Fig. 19), enclosing spores with four
hygrometric club-shaped filaments called elaters (Figs. 20 and 21).
At the present day some of these plants in tropical regions have
stems of 15 or 16 feet high.
[Illustration: Fig. 19-21.]
[Sidenote: Fig. 19. Polygonal scale, _s_, of a species of Horse-tail
(_Equisetum_), bearing membranous sacs, _t_, which open on their
inner surface to discharge spores.
Fig. 20. Spore of Equisetum, surrounded by two filaments
with club-shaped extremities. The filaments are represented as coiled
round the spore.
Fig. 21. Spore of Equisetum, with the filaments (elaters)
expanded.]
Among vascular Acrogens is included the natural order Marsileaceæ
or Rhizocarpeæ, the Pepperworts (Fig. 22). The order consists of
aquatic plants, with creeping stems, bearing leaves, which are either
linear, or divided into three or more wedge-shaped portions not
unlike clover. The fructification is at the base of the leaf-stalks,
and consists of sacs (sporocarps) containing spores of two kinds,
microspores and macrospores. The order contains Marsilea, Pilularia,
Azolla, and Salvinia.
For a fuller account of Acrogenous plants, see Balfour's Class Book
of Botany, p. 954.
These orders are represented in the Palæozoic flora. Many of the
fossil species assume a large size, and show a greater degree
of development than is seen in their recent congeners. The most
important coal plants belong to the Ferns, Lycopods, and Horse-tails.
The examination of the structure and conformation of the plants of
the present flora assists much in the determination of the fossil
carboniferous flora.
[Illustration: Fig. 22.]
[Sidenote: Fig. 22. _Marsilea Fabri_, a species of Pepperwort or
Rhizocarp, with a creeping stem, quadrifoliate stalked leaves on one
side, and roots on the other. The fructification, _s_, is at the base
of the leaves, and consists of sporangia, called sporocarps.]
In the lower Palæozoic strata the plants which have been detected
are few. In the Silurian and Cambrian systems, we meet with the
remains of ancient marine plants, as well as a few terrestrial
species. Even in the still older Laurentian rocks, if the remarkable
structure known as Eozoon canadense be considered, as it generally
is, an animal, the existence of contemporary plants may be inferred,
inasmuch as without vegetable life animals could not obtain food.
In the Lower Silurian or Grauwacke, near Girvan, Hugh Miller found
a species resembling Zostera in form and appearance. In the Lower
Old Red Sandstone of Scotland he detected Fucoids, a Lepidodendron,
and Lignite with a distinct Coniferous structure resembling that of
Araucaria,[1] besides a remarkable pinnate frond. In the middle Old
Red of Forfarshire, as seen in the Arbroath pavement, he found a
fern with reniform pinnæ and a Lepidodendron. In the Upper Old Red,
near Dunse, a Calamite and the well-known Irish fern Cyclopteris
Hibernica occur.[2] This fern, Palæopteris Hibernica of Schimper
(Plate I. Figs. 1 to 4), along with Sigillaria dichotoma, is very
abundant in beds of the same age in the south of Ireland, from
which the specimens described by Edward Forbes were obtained. The
fructification has recently been discovered. This shows that the fern
belongs to the Hymenophylleæ, and is consequently nearly related to
the equally famous Killarney fern, Trichomanes radicans.
Mr. Carruthers states that the frond-stalk of this fern is thick,
of considerable length, and clothed with large scales, which form
a dense covering at the somewhat enlarged base. The well-defined
separation observed in several specimens probably indicates that
the frond-stalks were articulated to the stem or freely separated
from it, and some root-like structures which occur on the slabs with
the ferns may be their creeping rhizomes. The pinnæ are linear,
obtuse, and almost sessile. The pinnules are numerous, overlapping,
of an ovate or oblong-ovate form, somewhat cuneate below, and with
a decurrent base. The veins are very numerous, uniform, repeatedly
dichotomous, and run out to the margin, where they form a slight
serration. Single pinnules rather larger than those of the pinnæ
are placed over the free spaces of the rachis, as was pointed out
by Brongniart. Carruthers has not met with any recent fern in which
this occurs; but it has been observed in several fossil species, as
in the allied American Palæopteris Halliana (Sch.), in Sphenopteris
erosa (Morris), and others. The pinnules are sometimes entirely,
but only partially fertile. The ovate-oblong sori are generally
single and two-lipped, the slit passing one-third of the way down
the sorus. The vein is continued as a free receptacle in the
centre of the cup or cyst, as in existing Hymenophylleæ, in which
it is included, not reaching beyond its entire portion. In some
specimens the receptacle is broad or thick, indicating the presence
of something besides itself in the cup, and giving the appearance
that would be produced if it were covered with sporangia; there is
no indication on the outer surface which might have been expected
from the separate sporangia. The compression of the specimens in the
rock, which has made the free receptacle appear like a vein on the
wall of the cup, together with the highly altered condition of the
rock in which the fossils are contained, accounts for the imperfect
preservation of the minute structures. The interpretation here given
of the fructification of this interesting fossil exhibits so close
a resemblance to what we find in the living genus Hymenophyllum,
that, were it not for the vegetative portions, it would be placed
in that genus. Several ferns have been described by Bunbury from
Devonian rocks at Oporto. A still more extensive and varied land
flora of Devonian age (or Erian, as he calls it) has been described
and illustrated by Principal Dawson from the rocks of that period
occurring in Canada; and during a recent visit to Britain he has
correlated many of the fragments collected by Miller, Peach, and
others, with the American species he has described. The following
are some of the fossil plants from beds older than the Carboniferous
system:[3]--Prototaxites Logani, Dadoxylon Ouangondianum, Calamites
transitionis, Asterophyllites parvulus, Sphenophyllum antiquum,
Lepidodendron Gaspianum, Lepidostrobus Richardsoni, L. Matthewi,
Psilophyton princeps, P. robustius, Selaginites formosus, Cordaites
Robbii, C. angustifolius, Cyclopteris Jacksoni.
From the microscopic examination of the structure of specimens of
fossil trunks described under the name of Prototaxites Logani, and
which Principal Dawson believes to be the oldest known instance of
Coniferous wood, Mr. Carruthers has come to the conclusion that
they are really the stems of huge Algæ, belonging to at least more
than one genus. They are very gigantic when contrasted with the
ordinary Algæ of our existing seas, nevertheless some approach to
them in size is made in the huge and tree-like Lessonias which Dr.
Hooker found in the Antarctic Seas, and which have stems about 20
feet high, with a diameter so great that they have been collected by
mariners in these regions for fuel, under the belief that they were
drift-wood. They are as thick as a man's thigh. Schimper regards the
Psilophyton of Dawson (Plate IV. Fig. 5) as allied to Pilularia, one
of the Rhizocarps (Fig. 22), and Carruthers places it among the true
Lycopodiaceæ.
_FLORA OF THE CARBONIFEROUS EPOCH._
The Carboniferous period is one of the most important as regards
fossil plants. The vegetable forms are numerous, and have a great
similarity throughout the whole system, whether exhibited in the Old
or the New World. The important substance called Coal owes its origin
to the plants of this epoch. It has been subjected to great pressure
and long-continued metamorphic action, and hence the appearance
of the plants has been much altered. It is difficult to give a
definition of Coal. The varieties of it are numerous. There is a
gradual transition from Anthracite to Household and Parrot Coal; and
the limit between Coal and what is called bituminous shale is by no
means distinct. Coal may be said to be chemically-altered vegetable
matter inter-stratified with the rocks, and capable of being used as
fuel. On examining thin sections of coal under the microscope, we can
detect vegetable tissues both of a cellular and vascular nature. In
Wigan cannel coal, vegetable structure is seen throughout the whole
mass. Such is likewise the case with other cannel, parrot, and gas
coals. In common household coal, also, evident traces of organic
tissue have been observed. In some kinds of coal punctated woody
tissue (Plate III. Fig. 5) has been detected, in others scalariform
tissue (Plate III. Fig. 6), as well as cells of different kinds.
Sporangia are also frequently found in the substance of coal, as
shown by Mr. Daw in that from Fordel (Plate III. Figs. 1 to 3); and
some beds, like the Better bed of Bradford, are composed almost
entirely of these sporangia imbedded in their shed microspores,
as has been recently shown by Huxley. The structure of coal in
different beds, and in different parts of the same bed, seems to vary
according to the nature of the plants by which it has been formed,
as well as to the metamorphic action which it has undergone. Hence
the different varieties of coal which are worked. The occurrence of
punctated tissue indicates the presence of Coniferæ in the coal-bed,
while scalariform vessels point to ferns, and their allies, such as
Sigillaria and Lepidodendron. The anatomical structure of the stems
of these plants may have some effect on the microscopic characters
of the coal produced from them. In some cannel coals structure
resembling that of Acrogens has been observed. A brownish-yellow
substance is occasionally present, which seems to yield abundance of
carburetted hydrogen gas when exposed to heat.
It appears that in general each bed of coal is accompanied by the
remains of a somewhat limited amount of species. Their number,
particularly in the most ancient beds, is scarcely more than eight
or ten. In other cases the number is more considerable, but rarely
more than thirty or forty. In the same coal-basin each layer often
contains several characteristic species which are not met with
either in the beds above or below. Thus, there are sometimes small
local or temporary floras, each of which has given birth to layers
of coal. The quantity of carbonaceous and other matter required to
form a bed of coal is immense. Maclaren has calculated that one acre
of coal three feet thick is equal to the produce of 1940 acres of
forest.[4] The proportion of carbon varies in different kinds of
coal. Along with it there is always more or less of earthy matter
which constitutes the ashes. When the earthy substances are in such
quantity that the coaly deposit will not burn as fuel, then we have
what is called a shale. The coal contains plants similar to those of
the shales and sandstones above and below it. Underneath a coal-seam
lies the Underclay, containing roots only, and representing the
ancient soil; then comes the Coal, composed of plants whose roots are
in the clay, with others which have grown along with and upon them,
in a manner precisely similar to the growth of peat at the present
day; while above the coal is the Shale, marking how mud was laid
down on the plants, and bearing evidences of vigorous vegetation
on neighbouring land, from which currents brought down the fine
sediment, mingled with broken pieces of plants.
The total thickness of coal in the English coal-fields is about 50
or 60 feet. In the Mid-Lothian field there are 108 feet of coal.
Coal-beds are worked at 1725 feet below the sea-level, and probably
extend down to upwards of 20,000 feet. They rise to 12,000 feet above
the sea-level, and at Huanuco, in Peru, to 14,700.[5] It is said that
the first coal-works were opened at Belgium in 1198, and soon after
in England and Scotland; it was not till the fifteenth century that
they were opened in France and Germany.
The following calculations have been made as to the extent of the
coal formation in different countries, and the amount of coal
raised:--[6]
+--------------------------------+----------------+------------------+
| COUNTRIES. | Square Miles of| Annual Production|
| | Coal Formation.| of Coal in Tons.|
+--------------------------------+----------------+------------------+
|Great Britain and Ireland | 5,400 | 65,887,900 |
|British North America | 7,530 | 1,500,000 |
|United States | 196,650 | 5,000,000 |
|Belgium | 518 | 8,409,330 |
|France | 1,719 | 7,740,317 |
|Prussia and Austria | ---- | 4,200,000 |
|Saxony | 30 | 1,000,000 |
|Russia | 100 | 3,500,000 |
|Japan, China, Borneo, Australia,| | |
| etc. | ---- | 2,000,000 |
+--------------------------------+----------------+------------------+
| Total Produce of the World | ---- | 99,237,547 |
+--------------------------------+----------------+------------------+
The total quantity of coal annually raised over the globe appears
thus to be about 100 millions of tons, of which the produce of Great
Britain is more than two-thirds, and would be sufficient to girdle
the earth at the equator with a belt of 3 feet in thickness and
nearly 5 feet in width. The coal-fields of the United States are
nearly forty times larger than those of Great Britain.
Roscoe gives the following estimated quantities of coal in the
principal countries:--
+-----------------------------------+------------+-------------------+
| | Average | |
| COUNTRIES. | Thickness. | Tons. |
| | No. Feet. | |
+-----------------------------------+------------+-------------------+
|Belgium | 60 | 36,000,000,000 |
|France | 60 | 59,000,000,000 |
|British Islands | 35 | 190,000,000,000 |
|Pennsylvania | 25 | 316,400,000,000 |
|Great Appalachian Coalfield | 25 | 1,387,500,000,000 |
|Indiana, Illinois, Western Kentucky| 25 | 1,277,500,000,000 |
|Missouri, and Arkansas Basin | 10 | 739,000,000,000 |
|North America (assumed thickness | | |
| over an area of 200,000 square | | |
| miles) | 20 | 4,000,000,000,000 |
+-----------------------------------+------------+-------------------+
Unger enumerates 683 plants of the coal-measures, while Brongniart
notices 500. Of the last number there are 6 Thallogens, 346
Acrogens, 135 Gymnosperms, and 13 doubtful plants. This appears
to be a very scanty vegetation, as far as regards the number of
species. It is only equal to about 1/20th of the number of species
now growing on the surface of the soil of Europe. Although,
however, the number of species was small, yet it is probable that
the individuals of a species were numerous. The proportion of
Ferns was very large. There are between 200 and 300 enumerated.
Schimper thinks there are 7 species congeneric with Lycopodium
found in the coal-measures. The following are some of the
Cryptogamous and Phanerogamous genera belonging to the flora of
the Carboniferous period:--Cyclopteris, Neuropteris, Odontopteris,
Sphenopteris, Hymenophyllites, Alethopteris, Pecopteris, Coniopteris,
Cladophlebis, Senftenbergia, Lonchopteris, Glossopteris, Caulopteris,
Lepidodendron (Lepidostrobus, Lepidophyllum, Knorria), Flemingites,
Ulodendron, Halonia, Psaronius, Sigillaria and Stigmaria, Calamites
(Asterophyllites and Sphenophyllum), Noeggerathia, Walchia, Peuce,
Dadoxylon, Pissadendron, Trigonocarpum.
Ferns are the carboniferous fossil group which present the most
obvious and recognisable relationship to plants of the present day.
While cellular plants and those with lax tissues have lost their
characters by the maceration to which they were subjected before
fossilisation took place, ferns are more durable, and retain their
structure. It is rare, however, to find the stalk of the frond
completely preserved down to its base. It is also rare to find
fructification present. In this respect, fossil Ferns resemble
Tree-ferns of the present day, the fronds of which rarely exhibit
fructification. Hooker states that of two or three kinds of New
Zealand Tree-fern, not one specimen in a thousand bears a single
fertile frond, though all abound in barren ones. Only one surface
of the fossil Fern-frond is exposed, and that generally the least
important in a botanical point of view. Fructification is sometimes
evidently seen, as figured by Corda in Senftenbergia. In this case
the fructification is not unlike that of Aneimidictyon of the present
day. Carruthers has recently detected the separate sporangia of Ferns
full of spores in calcareous nodules in coal (Plate I. Fig. 5). These
have the elastic ring characteristic of the Polypodiaceæ, and in
their size, form, and method of attachment, they are allied to the
group Hymenophylleæ. The absence of fructification presents a great
obstacle to the determination of fossil Ferns. Circinate vernation,
so common in modern Ferns, is rarely seen in the fossil species,
and we do not in general meet with rhizomes. Characters taken from
the venation and forms of the fronds are not always to be depended
upon, if we are to judge from the Ferns of the present day. There
is a great similarity between the carboniferous Ferns of Britain
and America; and the same species, or closely allied species of the
same genera as those found in Britain have been met with in South
Africa, South America, and Australia. In the English coal-measures
the species are about 140. The Palæozoic flora of the Arctic regions
also resembles that of the other quarters of the globe. Heer, in
his account of the fossil flora of Bear Island,[7] enumerates the
following plants:--Cardiopteris frondosa, C. polymorpha, Palæopteris
Roemeriana, Sphenopteris Schimperi, Lepidodendron Veltheimianum, L.
commutatum, L. Carneggiannum, L. Wilkianum, Lepidophyllum Roemeri,
Knorria imbricata, K. acicularis, Calamites radiatus, Cyclostigma
Kiltorkense, Stigmaria ficoides, etc., Cardiocarpum ursinum, C.
punctulatum, besides various sporangia and spores.
[Illustration: Fig. 22, _bis_.]
[Sidenote: Fig. 22, _bis_. Adiantites Lindseæformis.]
The preponderance of Ferns over flowering plants is seen at the
present day in many tropical islands, such as St. Helena and the
Society group, as well as in extra-tropical islands, as New Zealand.
In the latter, Hooker picked 36 kinds in an area of a few acres;
they gave a luxuriant aspect to the vegetation, which presented
scarcely twelve flowering plants and trees besides. An equal area
in the neighbourhood of Sydney (in about the same latitude) would
have yielded upwards of 100 flowering plants, and only two or three
Ferns. This Acrogenous flora, then, seems to favour the idea of
a humid as well as mild and equable climate at the period of the
coal formation--the vegetation being that of islands in the midst
of a vast ocean. Lesquereux, in Silliman's Journal, gives three
sections of Ferns in the Carboniferous strata--viz. Neuropterideæ,
Pecopterideæ, and Sphenopterideæ. In Neuropterideæ fructification has
been seen in Odontopteris. In this genus the spores are in a peculiar
bladdery sporangium. In Neuropterideæ the fructification appears to
have resembled Danæa in some cases, and Osmunda in others. Professor
Geikie has noticed in the lower Carboniferous shales of Slateford,
near Edinburgh, a fern which has been named Adiantites Lindseæformis
by Bunbury (Fig. 22, _bis_). It has pinnules between crescent and
fan shaped. (Mem. Geol. Survey of Edinburgh, 1861, p. 151.)
Among the Ferns found in the clays, ironstones, and sandstones of
the Carboniferous period, we shall give the characters of some
by way of illustration.[8] Pecopteris (Fig. 23) seems to be the
fossil representative, if not congener, of Pteris. Pecopteris
heterophylla (Fig. 24) has a marked resemblance to Pteris
esculenta of New Zealand. The frond of Pecopteris is pinnatifid,
or bi-tri-pinnatifid--the leaflets adhering to the rachis by the
whole length of their base, sometimes confluent; the midrib of the
leaflets runs to the point, and the veins come off from it nearly
perpendicularly, and the fructification when present is at the end of
the veins. Neuropteris (Figs. 25, 26, 27) has a pinnate or bipinnate
frond, with pinnæ somewhat cordate at the base--the midrib of the
pinnæ vanishing towards the apex, and the veins coming off obliquely,
and in an arched manner. Neuropteris gigantea (Fig. 26) has a thick
bare rachis, according to Miller, and seems to resemble much Osmunda
regalis. Odontopteris has leaves like the last, but its leaflets
adhere to the stalk by their whole base, the veins spring from the
base of the leaflets, and pass on towards the point. Sphenopteris
(Fig. 28) has a twice or thrice pinnatifid frond, the leaflets being
narrowed at the base, often wedge-shaped, and the veins generally
arranged as if they radiated from the base. Sphenopteris elegans
resembled Pteris aquilina in having a stout leafless rachis, which
divided at a height of seven or eight inches from its club-like base
into two equal parts, each of which continued to undergo two or three
successive bifurcations. A little below the first forking two divided
pinnæ were sent off. A very complete specimen, with the stipe, was
collected in the coalfield near Edinburgh by Hugh Miller, who has
described it as above. Lonchopteris has its frond multi-pinnatifid,
and the leaflets more or less united together at the base; there is a
distinct midrib, and the veins are reticulated. Cyclopteris (Fig. 29)
has simple orbicular leaflets, undivided or lobed at the margin, the
veins radiating from the base, with no midrib. Schizopteris resembles
the last, but the frond is deeply divided into numerous unequal
segments, which are usually lobed and taper-pointed.
[Illustration: Fig. 23-29.]
[Sidenote: Figs. 23 to 29 exhibit the fronds of some of the Ferns
of the Carboniferous epoch. Fig. 23. _Pecopteris (Alethopteris)
aquilina_. Fig. 24. _Pecopteris (Alethopteris) heterophylla_. Fig.
25. _Neuropteris Loshii._ Fig. 26. _Neuropteris gigantea._ Fig. 27.
_Neuropteris acuminata._ Fig. 28. _Sphenopteris affinis._ Fig. 29.
_Cyclopteris dilatata._]
[Illustration: Fig. 30-32.]
[Sidenote: Figs. 30 to 32. Stem of Tree-ferns, called _Caulopteris_.
Fig. 30. _Caulopteris macrodiscus._ Fig. 31. _Caulopteris Balfouri_
(Carr.), Coal-measures. Fig. 32. _Caulopteris Morrisi_ (Carr.),
Coal-measures.]
The rarity of Tree-ferns in the coal-measures has often been
observed, and it is the more remarkable from the durable nature of
their tissues. Several species have, however, been noticed. They
are referred to the genus Caulopteris. One of them, C. macrodiscus
(Fig. 30) has the leaf-scars in linear series. Two other species are
figured, the one a slender form with the scars widely separated,
as in some Alsophilas, C. Balfouri (Fig. 31) from the Somersetshire
coal-field; and the other with larger stems and more closely
aggregated scars, C. Morrisi (Fig. 32), from the coal-measures at
Newcastle. The latter species shows the cavities at the base of the
petiole described by Mohl in many living fern-stems. The fossils
named Psaronius appear to have been fern-stems with a slender axis
and a large mass of adventitious roots, as in some Dicksonias and
in Osmunda regalis. These stems probably belong to some of the
fronds to which other names are given, but as they have not been
found attached, it is impossible to determine the point. Miller has
described a fern as occurring in the coal-measures, which at first
sight presents more the appearance of a Cycadaceous frond than
any other vegetable organism of the carboniferous age except the
Cycadites Caledonicus (Salter), from Cockburnspath Cove. He thus
describes it:--
"From a stipe about a line in thickness there proceed at right
angles, and in alternate order, a series of sessile lanceolate
leaflets, rather more than two inches in length, by about an eighth
part of an inch in breadth, and about three lines apart. Each is
furnished with a slender midrib; and, what seems a singular, though
not entirely unique feature in a Fern, the edges of each are densely
hirsute, and bristle with thick short hair. The venation is not
distinctly preserved."
[Illustration: Fig. 33-34.]
[Illustration: Fig. 36-37.]
[Sidenote: Figs. 33 to 37 exhibit forms of Sigillaria stems found in
the shales of the Carboniferous epoch. Fig. 33. Stem of _Sigillaria
pachyderma_ in an erect position, covered by successive deposits
of sandstone and shale; one of the stems is bifurcated. Fig. 34.
_Sigillaria reniformis_, with its external markings, and roots
which are Stigmarias, as proved by Mr. Binney. Fig. 35. _Sigillaria
pachyderma_, after Lindley and Hutton, from the shale of Killingworth
Colliery, showing the scars or places through which the vessels of
the stem passed to the leaves. Fig. 36. _Sigillaria (Favularia)
tessellata_, from the Denbigh coal-shale, showing the fluted stem
with scars. Fig. 37. _Sigillaria pachyderma_; the stem marked with
scars, and fluted longitudinally.]
[Illustration: Fig. 35.]
Sigillaria (Plate IV. Figs. 1 and 2) is perhaps the most important
plant in the coal formation. The name is derived from sigillum, a
seal, to indicate the seal-like markings in the stem. It is found
in all coal-shales over the world. Schimper mentions 83 species. It
occurs in the form of lofty stems, 40-50 feet high, and 5 feet broad
(Figs. 33 and 34). Many stems of Sigillaria may be seen near Morpeth,
standing erect at right angles to the planes of alternating strata
of shale and sandstone (Fig. 33). They vary from 10 to 20 feet in
height, and from one to three feet in diameter. Sir W. C. Trevelyan
counted 20 portions of these trees within the length of half-a-mile,
of which all but four or five were upright. Brongniart mentions
similar erect stems as being found near St. Etienne. The stem of
Sigillaria is fluted in a longitudinal manner, like a Doric column,
and has a succession of single scars, which indicate the points
of insertion of the leaves (Figs. 35, 36, and 37). When the outer
part of the stem separates like bark, it is found that the markings
presented by the inner surface differ from those seen externally.
This has sometimes given rise to the erroneous multiplication of
species and even of genera. Sigillaria elegans, as figured by
Brongniart in Archives du Museum, i. 405, has a stem consisting of a
central cellular axis or medulla, surrounded by a vascular cylinder,
and this is invested by a thick cellular cortical layer, the outer
portion composed of fusiform cells of less diameter than those of
the inner portion. What Brongniart calls medullary rays are mere
cracks or separations in the wedges traversed by vessels. In its
structure it resembles its root Stigmaria, and must be referred to
Lycopodiaceæ, along with Lepidodendron, Halonia, Ulodendron, etc. The
small round sporangia of Sigillaria are borne in a single patch on
the somewhat enlarged bases of some of the leaves. (See Carruthers
on Structure and Affinities of Sigillaria, in Journ. Geol. Soc. Aug.
1869.)
[Illustration: Fig. 38-39.]
[Sidenote: Fig. 38. _Stigmaria ficoides_, root of Sigillaria, giving
off rootlets, which have been compressed.
Fig. 39. _Stigmaria ficoides_ (_S. Anabathra_ of Corda),
which is the root of a Sigillaria. The markings are the points whence
rootlets proceed.]
It has been ascertained by Professor King and Mr. Binney of
Manchester, that the plant called Stigmaria (Fig. 38) is not a
separate genus, but the root of Sigillaria (Plate IV. Figs. 1
and 2). The name is derived from στίγμα, a mark, indicating the
markings on the axis. It is one of the most common productions of the
coal-measures, and consists of long rounded or compressed fragments,
marked externally by shallow circular, oblong, or lanceolate
cavities (Fig. 39) in the centre of slight tubercles, arranged more
or less regularly in a quincuncial manner (Plate III. Fig. 7). The
cavities occasionally present a radiating appearance. The axis of
the fragments is often hollow, and different in texture from the
parts around. This axis consists of a vascular cylinder or woody
system, penetrated by quincuncially arranged meshes or openings,
through which the vascular bundles proceed from the inner surface
of the cylinder to the rootlets (Plate III. Figs. 8 and 9). From
the scars and tubercles arise long ribbon-shaped processes, which
were cylindrical cellular roots, now compressed (Fig. 38). The
vascular cylinder of Stigmaria is composed entirely of scalariform
tissue, pierced by meshes for the passage, from the inner surface
of the cylinder, of the vascular bundles which supply the rootlets.
(Carruthers in Geol. Proc., Aug. 1869.) Stigmaria ficoides (Fig.
38) abounds in the under-clay of a coal-seam, sending out numerous
roots from its tubercles, and pushing up its aerial stem, in the form
of a fluted Sigillaria. On the Bolton and Manchester Railway Mr.
Binney discovered Sigillarias standing erect, and evidently connected
with Stigmarias which extended 20 feet or more.[9] Stigmaria is
regarded by Schimper as roots, not of Sigillaria only, but of
Knorria longifolia (one of the Lepidodendreæ). The base of the stem
of this species of Knorria is Ancestrophyllum, and the upper part
is Didymophyllum Schottini of Goeppert. Professor King and others
suppose that the Fern-like frond called Neuropteris is connected with
Sigillaria, but this is a mere conjecture, set aside by the discovery
of leaves attached to a species allied to Sigillaria elegans, which
establishes that the long linear leaves described under the name
Cyperites are the foliage of this genus. Goldenberg has figured the
fructification, which consists of small sporangia like those of
Flemingites, borne on the basis of but slightly modified leaves.
This establishes the opinion that Sigillaria was an acrogenous plant
belonging to Lycopodiaceæ. Brongniart reckons it as representing an
extinct form of Gymnosperms, and King, having erroneously associated
the Cyclopteris with it, places it between the Ferns and Cycadaceæ.
Mr. Carruthers informs me that he has examined the stem of a true
fluted Sigillaria, with the tissues preserved, and that these agree
with the structure of Lepidodendron, a position in which he had
already placed it from the structure of its fruit.
[Illustration: Fig. 40-41.]
[Sidenote: Figs. 40 to 44 exhibit the stems and fructification of
Lepidodendron. Fig. 40. Bifurcating stem of _Lepidodendron obovatum_
(_elegans_), showing the scale-like scars, and the narrow-pointed
leaves, resembling those of Lycopodium, but much larger. Fig. 41.
Stem of _Lepidodendron crenatum_, with the scars of its leaves.]
[Illustration: Fig. 42-43.]
[Sidenote: Fig. 42. Fructification of Lepidodendron, showing its
cone-like form and spiral arrangement of scales. It is called
_Lepidostrobus Dabadianus_ by Schimper, but it is probably
Triplosporites.
Fig. 43. Longitudinal section of the fructification,
showing central axis and scales carrying sporangia. The upper
sporangium contains microspores, the lower macrospores; hence it has
the character of Triplosporites.]
[Illustration: Fig. 44.]
[Sidenote: In woodcut 44 are represented the fruits of Selaginella
(one of the Lycopodiums of the present day), Lepidostrobus,
Triplosporites, and Flemingites. Fig. 1. _Selaginella spinulosa_, A.
Braun (_Lycopodium selaginoides_, Linn.) 2. Scale and sporangium from
the upper portion of the cone. 3. Antheridian microspores from the
same. 4. Macrospore. 5. Scale and sporangium from the lower part of
the cone, containing macrospores. 6. _Lepidostrobus ornatus_, Hooker.
7. Three scales and sporangia of ditto. 8. Microspores from the
sporangia of the upper part of the cone of _Triplosporites Brownii_,
Brongn. 9. Macrospore from the sporangia of the lower part (drawn
from Brongniart's description and measurements). 10. Scales and
sporangia of a cone of Flemingites.[10]]
Lepidodendron (Figs. 40 to 44) is another genus of the coal-measures
which differs from those of the present day (Plate IV. Fig. 3).
Lepidodendrons, or fossil Lycopodiaceæ, had spikes of fructification
comparable in size to the cones of firs and cedars, and containing
very large sporangia, even larger than those of Isoetes, to which
they approach in form and structure. Schimper, in 1870, enumerates
56 species of Lepidodendron, all arborescent and carboniferous.
The stem of a Lepidodendron is from 20 to 45 feet high, marked
outside by peculiar scale-like scars (Fig. 41), hence the name of
the plant (λεπίς, a scale, and δένδρον, a tree). Although the scars
on Lepidodendron are usually flattened, yet in some species they
occupy the faces of diamond-shaped projections, elevated one-sixth
of an inch or more above the surface of the stem, and separated from
each other by deep furrows;--the surface bearing the leaf being
perforated by a tubular cavity, through which the bundle of vessels
that diverged from the vascular axis of the stem to the leaf passed
out. The linear or lanceolate leaves are arranged in the same way as
those of Lycopodiums or of Coniferæ, and the branches fork like the
former. The internal structure of the stem is the same as that of
Sigillaria. The fruit of Lepidodendron and allied genera is seen in
Lepidostrobus and Triplosporites (Figs. 42, 43; Plate III, Fig. 10).
Carruthers, in his lecture to the Royal Institution, in describing
the forms of Lepidostrobus, says--"The fruit is a cone composed
of imbricated scales arranged spirally on the axis like the true
leaves, and bearing the sporangia on their horizontal pedicels. Three
different forms of fruit belong to this genus, or it should perhaps
rather be called group of plants. The first of these is the cone
named by Robert Brown Triplosporites (Figs. 42, 43), and described by
him from an exquisitely preserved specimen of an upper portion, in
which the parts are exhibited as clearly in the petrified condition
as if they belonged to a fresh and living plant. The large sporangia
have a double wall, the outer composed of a compact layer of oblong
cells placed endwise, or with the long diameter perpendicular to the
surface; the inner is a delicate cellular membrane. The sporangium
is filled with a great number of very small spores, each composed of
three roundish bodies or sporules. Recently Brongniart and Schimper
have described a complete specimen of this fruit, in which the minute
triple spores are confined to the sporangia of the upper and middle
part of the cone, but the lower portion, which was wanting in Brown's
specimen, bears sporangia filled with simple spherical spores ten or
twelve times larger than the others (woodcut 44, 9).
"The structure of another form of cone (Lepidostrobus) has been
expounded by Dr. Hooker. The arrangement of the different parts
comprising it is precisely similar to what occurs in Triplosporites;
but the sporangia are filled with the minute triple spores throughout
the whole cone (woodcut 44, 6 and 8).
"The third form of cone, described by me under the name Flemingites,
differs from the other two in having a large number of small
sporangia supported on the surface of each scale; and it agrees with
Lepidostrobus in the sporangia containing only small spores (woodcut
44, 10).
"In comparing these fossils with the living club-mosses, one is
struck with the singular agreement in the organisation of plants so
far removed in time, and so different in size, as the recent humble
club-mosses and the palæozoic tree Lepidodendrons. The fruit of
Triplosporites, like that of Selaginella (woodcut 44, 1), contains
large and small spores, the microspores being found in both genera on
the middle and upper scales of the cone, and the macrospores on those
of the lower portion (Fig. 43).
"On the other hand, the fruits of Lepidostrobus and Flemingites
agree with that of Lycopodium in having only microspores. The size
of the two kinds of spores also singularly agrees in the two groups.
This is of some importance, for among the recent vascular Cryptogams
there is a remarkable uniformity in the size of the spores in the
members of the different groups, even when there is a great variety
in the size of the plants. Thus the spore of our humble wall-rue
is as large as that of the giant Alsophila of tropical regions. So
also the spores of Equisetum and Calamites agree in size, as may be
seen in woodcut 47, Figs. 3, 4, and 9, where the spores of the two
genera are magnified to the same extent. And a similar comparison
of the macrospore and microspore of Triplosporites with those of
Selaginella, and of the microspore of Lepidostrobus with that of
Lycopodium, exhibits a similar agreement. This is made apparent by
the drawings in woodcut 44 of the two kinds of spores of Selaginella,
3 and 4, with those of Triplosporites, 8 and 9, which are drawn to
the same scale."
The genus Sigillaria, as we have already said, has, according to the
observation of Hooker, small sporangia exactly agreeing in size and
form with those of Flemingites. Most probably the contents of these
small sporangia were the same in both genera, so that Sigillaria
would be placed with Flemingites and Lepidostrobus as arborescent
Lycopodiaceæ having their affinities with Lycopodium, as they have
all microspores only in their fructification.
The scales upon the Lepidodendron stems, as well as those in the
cones, are arranged in a spiral manner, in the same way as plants
of the present day. Professor Alexander Dickson has examined the
phyllotaxis of Lepidodendrons, and gives the following results of his
observations (Trans. Bot. Soc. Edin. xi. 145). The fossil remains
of Lepidodendrons are often so compressed that it is difficult,
or even impossible, to trace the secondary spirals round the
circumference of the stem. In those cases, however, where there is
comparatively little compression, _i.e._ where the stem is more or
less cylindrical, the determination of the phyllotaxis is easy. Of
such stems he has examined fifteen specimens, which may be classed
according to the series of spirals to which the leaf-arrangement
belongs:--
A. Ordinary series, ½, ⅓, ⅖, ⅜, 5/13, etc.
(a.) Single spirals (D turning to the right, S to the left).
(1.) _Lepidodendron_ (Possil Ironstone series). Stem about ¾
of an inch in diameter. Secondary spirals 8 D, 13 S, 21 D.
Divergence = 13/34 (or possibly 21/55).
(2.) _Lepidodendron_ (Knightswood, near Glasgow, Mr. J. Young).
Stem about 1½ inch in diameter. Secondary spirals 13 D, 21 S, 34
D. Divergence = 21/55.
(3.) _Lepidodendron_ (Possil Sandstone series). Trunk about
2 feet long, with an average diameter of 20 inches. Steepest
secondary spirals 55 S, 89 D. Divergence = 55/144.
(b.) Conjugate spirals.[11]
(4.) _Lepidostrobus ornatus_ (Bathgate coal-field). About ¾ of
an inch in diameter. Secondary spirals 10 D, 16 S, 26 D, 42 S.
Divergence = 13/(34×2) (Bijugate arrangement).
(5.) _Lepidostrobus_ (Plean, Stirlingshire, Mr. Mackenzie). About
½ an inch in diameter. Secondary spirals 9 S, 15 D, 24 S, 39 D.
Divergence = 8/(21×3) (Trijugate arrangement).
(6.) _Knorria taxina_ (from collection of Dr. Rankin, Carluke).
Somewhat compressed, 2-2½ inches[12] in diameter. Secondary
spirals 15 D, 24 S. Divergence = 15/(13×3) (Trijugate
arrangement).
(7.) _Lepidodendron_ (from Dr. Rankin's collection). About 1¼
inch in diameter. Secondary spirals 10 D, 15 S, 25 D, 40 S.
Divergence = 5/(13×5) (Quinquejugate arrangement).
(8.) _Lepidodendron_ (Dowanhill, Glasgow, Possil Sandstone
series). Trunk about 1 foot long, and 1 foot in diameter. The
upper portion exhibits secondary spirals 35 D, 56 S, 91 D; thus
indicating a 7-jugate arrangement, with divergence = 8/(21×7).
The arrangement on the middle and lower portion is indistinct
and confused; so much so as to render any determination of the
arrangement doubtful.
B. Series, ⅓, ¼, 2/7, 3/11, etc.
(9.) _Lepidodendron_ (Messrs Merry and Cunningham's Clayband
Iron-Pit, Carluke). Stem 2 inches in diameter. Secondary spirals
18 S, 29 D, 47 S. Divergence = 21/76.
C. Series, ¼, ⅕, 2/9, 3/14, etc.
(10.) _Lepidodendron_ (R. B. Garden, Edinburgh, Museum). Stem
somewhat flattened, 1-1½ inch in diameter. Secondary spirals 9 D,
14 S, 23 D, 37 S. Divergence = 13/60.
(11.) _Lepidodendron_ (Redhaugh, near Edinburgh, Mr. Peach). Stem
somewhat flattened, ¾ to ½ inch in diameter. Secondary spirals 9
S, 14 D, 23 S, 37 D. Divergence = 13/60.
D. Series, ⅕, ⅙, 2/11, 3/17, 5/28, etc.
(12.) _Knorria taxina_ (Stockbriggs, Lesmahagow,--Hunterian
Museum). About 1 inch in diameter. The specimen consists of a
main stem and one of the branches into which it has forked.
On the main stem the secondary spirals are 6 D, 11 S, 17 D.
Divergence = 5/28 (series, ⅕, ⅙, 2/11, 3/17, 5/28, etc.)--On the
branch the secondary spirals are 8 S, 13 D. Divergence = 8/21
(ordinary series, ½, ⅓, ⅖, ⅜, etc.)
E. Series, ½, ⅖, 3/7, 5/12, 8/19, 13/31, 21/50, etc.
(13.) _Lepidodendron_ (from Dr. Rankin's collection). About ⅞
inch in diameter. Secondary spirals 12 D, 19 S, 31 D. Divergence
= 21/50.
F. Series, ⅓, 3/10, 4/13, 7/23, 11/36, 18/59, etc.
(14.) _Lepidodendron elegans_ (Possil Ironstone). About 1¼ inch
in diameter. Secondary spirals 10 S, 13 D, 23 S, 36 D. Divergence
= 18/59.
(15.) _Lepidodendron_ (Possil Ironstone). About 2¼ inches in
diameter. Secondary spirals 23 S, 36 D, 59 S, 95 D. Divergence =
47/154.
From the above it is evident that the phyllotaxis of Lepidodendron
is extremely variable, as much so perhaps as that of those most
variable plants, in this respect, the Cacti. It is also clear that
what has been enunciated by Professor Haughton (Manual of Geology,
Lond. 1866, pp. 243, 245) as the law according to which the leaves of
palæozoic plants were arranged--viz. that of alternate whorls--does
not apply to these ancient Lycopods. Lepidodendron aculeatum is noted
by Naumann as exhibiting an 8/21 arrangement. (Poggendorff, Annalen,
1842, p. 5.) Professor Alexander Braun (Nov. Acta Ac. C. L. C. xv.
1, pp. 558-9), speaking of the excessive deviation from ordinary
arrangements in Equisetaceæ (including Calamites), compares them in
this respect with Lycopodiaceæ (including Lepidodendron), saying
that in these two families "the utmost limits of the domain of all
leaf-arrangement appears to be attained."
Lepidophyllum is certainly leaves of Lepidodendron, the different
Lepidophylla belonging to different species of the genus. The slender
terminal branches are noticed under the name of Lycopodites. In coal
from Fordel Mr. Daw has detected innumerable bodies (Plate III.
Figs. 1, 2, 3) which have been shown to be sporangia. (Balfour,
Trans. Roy. Soc. Ed. xxi. 187.) On their under surface Mr. Carruthers
has observed a triradiate ridge (Plate III. Fig. 4). (Geological
Magazine, 1865, vol. ii. p. 140.) These sporangia have been found
connected with the cone-like fructification called Flemingites, and
resembling Lycopodium (woodcut 44, Fig. 4). Many forms of fossil
plants, such as Halonia, Lepidophloios, Knorria, and Ulodendron,
belong to the Lepidodendron group. Knorria is said to be the internal
cast of a Lepidodendron.
Ulodendron minus and U. Taylori (Plate III. Fig. 11), found in
ferruginous shale in the Water of Leith, near Colinton, exhibit
beautiful sculptured scars, ranged rectilinearly along the stem.
The surface is covered with small, sharply relieved obovate scales,
most of them furnished with an apparent midrib, and with their edges
slightly turned up. The circular or oval scars of this genus are
probably impressions made by a rectilinear range of aerial roots
placed on either side. When decorticated, the stem is mottled over
with minute dottings arranged in a quincuncial manner, and its oval
scars are devoid of the ordinary sculpturings. Bothrodendron is a
decorticated condition of Ulodendron.
[Illustration: Fig. 45 _a_.]
[Illustration: Fig. 45 _b_.]
[Sidenote: Fig. 45. _a_, _Calamites Suckovii_, composed of jointed
striated fragments having a bark. Fig. 45. _b_, Septum or phragma of
a Calamite.]
Calamites (κάλαμος, a reed) is a reed-like fossil, having a
sub-cylindrical jointed stem (Fig. 45, _a_ and _b_; Fig. 46; Plate
IV. Fig. 4). The stem is often crushed and flattened, and was
originally hollow. Calamites is thus defined by Grand d'Eury (Ann.
Nat. Hist. ser. 4, vol. iv. p. 124):--Stem articulated, fistular, and
septate; outer part comparatively thin, formed of three concentric
zones--1, an exterior cortical layer now converted into coal; 2, a
thin subjacent zone of vascular tissue, now invariably destroyed;
3, a sort of inner lining epidermis, which is carbonified. Cortical
envelope marked interiorly with regular flutings, interrupted and
alternate at the articulations. Inner epidermis smooth, or scarcely
striated. Vascular cylinder thin; outer surface of bark more fully
fluted and articulated than the inner surface.
[Illustration: Fig. 46.]
[Sidenote: Fig. 46. Vertical stems of fossil trees, Calamites
chiefly, found in the coal-measures of Treuil, near Saint Etienne.]
Carruthers gives the following description of the structure of a
species of Calamite which he examined:--The stem was composed of a
central medulla, which disappeared with the growth of the plant,
surrounded by a woody cylinder, composed entirely of scalariform
vessels, and a thin cortical layer. The medulla penetrated the
woody cylinder by a series of regular wedges, which were continued,
as delicate laminæ of one or two cells in thickness, to the
cortical layer. The cells of those laminæ were not muriform; their
longest diameter was in the direction of the axis. The wedges were
continuous, and parallel between each node. As the axial appendages
were produced in whorls, the only interference with the regularity of
the tissues was by the passing out through the stem at the nodes of
the vascular bundles which supplied these appendages. As the leaves
of each whorl were (with one or two exceptions) opposite to the
interspaces of the whorls above and below, there was also at each
node a re-arrangement of the wedges of vascular and cellular tissues.
Schimper considers Calamites as having an analogy with Equisetum in
its fructification. He looks on them as fossil Equisetaceæ. Annularia
and Sphenophyllum are considered as establishing a passage from the
Equisetaceæ to the Lycopodiaceæ. Some gigantic fossil Equiseta had
a diameter of nearly 5 inches, and a height of 30 or more feet. The
branches, which adorned the higher part of them in the form of a
crown, are simple, and have at their extremity a spike of the size
of a pigeon's egg, and organised exactly like the spikes of living
Equiseta. The subterranean rhizomes are well developed, and gave
origin, like many Equiseta, to tubercles which had the form and size
of a hen's egg.
The characters of Equisetum of the present day and Calamites, are
exhibited in woodcut 47. They show a marked resemblance in the
fructification. (See also page 31.)
Plants of Calamites have been seen erect by Mr. Binney, and he has
determined that what were called leaves or branches by some are
in reality roots. Mr. Binney gives a full description of various
Calamites, under the name of Calamodendron commune, in his Memoir
published by the Palæontographical Society, 1868. There are between
50 and 60 species recorded.[13]
In Spitzbergen, in rocks of the Carboniferous epoch, there have been
found Calamites, Sigillaria, Lepidodendron, and ferns, apparently the
same as those found in the Carboniferous epoch in Europe--Calamites
radiatus, Lepidodendron Veltheimianum, Sigillaria distans, Stigmaria
ficoides. Some species--Sigillaria Malmgreni, Lepidodendron
Carneggiannum, and L. Wilkianum--seem to be peculiar to Bear Island.
[Illustration: Fig. 47.]
[Sidenote: Fig. 47. Fruits of Equisetum and Calamites. 1. _Equisetum
arvense_, L. 2. Portion of sporangium wall. 3, 4. Spores, with the
elaters free. 5. Longitudinal section of the part of one side of
cone. 6. Transverse section of cone. 7. _Calamites (Volkmannia)
Binneyi_, Carr., magnified three times. 8. Portion of the sporangium
wall. 9. Two spores. 10. Longitudinal section of the part of one side
of cone. 11. Transverse section of cone.]
According to Carruthers the Equisetaceæ are represented in Britain by
the two genera Calamites found in primary beds, and Equisetum found
in secondary rocks and living at the present day. The difference in
the structure of their fruits is shown in woodcut 47. The fruit of
Calamites, called Volkmannia Binneyi (woodcut 47, 7), is a small
slender cone composed of alternating whorls of imbricate scales,
twelve in each verticil. The scales completely conceal the leaves
connected with the fructification. The fruit-bearing leaves are
stalked, peltate, and are arranged in whorls of 6. There are four
sporangia borne on the under-surface of the peltate leaves. These
spore-cases have cellular parietes, and in their interior there is
a deposit of cellulose in the form of short truncate processes not
unlike imperfect spirals. The spores are spherical, and appear to
have thread-like processes proceeding from them, similar to elaters.
The fruit-cone bears a marked resemblance to the fruit of Equisetum
in its fruit-bearing leaves, sporangia, spores, and elaters (see
Figs. 18, 19, 20, 21). In the modern plant all the leaves of the cone
are fructiferous, while in the fossil plant some are fruit-bearing,
and others are like the ordinary leaves of the plant. It is thought
that the fossil may be reckoned as having a somewhat higher position
than that possessed by the living genus.
[Illustration: Fig. 48.]
[Sidenote: Fig. 48. Foliage and fruits of Calamites. 1 and 2.
Asterophyllites; 3 and 4. Annularia; 5 and 6. Sphenophyllum.]
The different forms of foliage called Asterophyllites, Sphenophyllum,
and Annularia, belong to the one genus Calamites, but they may form,
perhaps, well-characterised sections when their fruits are better
known. In woodcut 48 representations are given of the foliage and
fruit of varieties of Calamites. In 1 and 2 we see the simplest form
called Asterophyllites. The leaves are linear and slender, with a
single rib. The form called Annularia (3 and 4) differs chiefly
in having a larger amount of cellular tissue spread out on either
side of the midrib. This form has a different aspect in a fossil
state from the other, from its whorls of numerous broad leaves
spread out on the surface of deposition, while the acicular leaves
of Asterophyllites have penetrated the soft mud, and are generally
preserved in the position they originally occupied in reference
to the supporting branch. The third form (5 and 6) is called
Sphenophyllum, and consists of whorls of wedge-shaped leaves, with
one or more bifurcating veins. They occur like those of Annularia,
spread out on the surface of the shale.
[Illustration: Fig. 49-50.]
[Sidenote: Fig. 49. _Araucarioxylon Withami_, Krauss (_Pinites
Withami_), from the Coal-measures, Craigleith, near Edinburgh,
showing pleurenchyma with disks, and medullary rays. An excellent
specimen of a stem of this pine may be seen in the Edinburgh Royal
Botanic Garden.
Fig. 50. _Trigonocarpum olivæforme_, an ovate, acuminate,
three-ribbed, and striated fruit or seed, which some suppose to be a
sporangium of a Lepidodendron, others refer it to Cycadaceæ. Hooker
refers it to Coniferæ like Salisburia.]
True Exogenous trees exist in the coal-fields both of
England and Scotland, as at Lennel Braes and Allan Bank, in
Berwickshire; High-Heworth, Fellon, Gateshead, and Wideopen, near
Newcastle-upon-Tyne; and in quarries to the west of Durham; also in
Craigleith quarry, near Edinburgh, and in the quarry at Granton, now
under water. In the latter localities they lay diagonally athwart
the sandstone strata, at an angle of about 30°, with the thicker and
heavier part of their trunks below, like snags in the Mississippi.
From their direction we infer that they have been drifted by a stream
which has flowed from nearly north-east to south-west. At Granton,
one of the specimens exhibited roots. In other places the specimens
are portions of stems, one of them 6 feet in diameter by 61 feet in
length, and another 4 feet in diameter by 70 feet in length. These
Exogenous trees are Gymnosperms, having woody tissue like that of
Coniferæ. We see under the microscope punctated woody tissue, the
rows of disks being usually two, three, or more, and alternating.
They seem to be allied in these respects to Araucaria and Eutassa
(Fig. 61, p. 74) of the present flora. Araucarioxylon or Pinites
Withami (Fig. 49) is one of the species found in Craigleith quarry;
the concentric layers of the wood are obsolete; there are 2, 3, or
4 rows of disks on the wood, and 2-4 rows of small cells in the
medullary rays. Along with it there have also been found Dadoxylon
medullare, with inconspicuous zones, 2, 3, and 4 rows of disks, and
2-5 series of rows of cells in the rays. Pissadendron antiquum (Pitus
antiqua) having 4-5 series of cells in the medullary rays, and P.
primævum (Pitus primæva), with 10-15 series of cells in the medullary
rays, occur at Tweedmill and Lennel Braes in Berwickshire; Peuce
Withami (Fig. 1, p. 3) at Hilltop, near Durham, and at Craigleith.
Sternbergia is considered by Williamson as a Dadoxylon, with a
discoid pith like that seen now-a-days in the Walnut, Jasmine, and
Cecropia peltata, as well as in some species of Euphorbia.[14]
Sternbergia approximata is named by him Dadoxylon approximatum.
Hooker believes from the structure of Trigonocarpum (Fig. 50) that it
is a coniferous fruit nearly allied to Salisburia (Trans. Roy. Soc.
1854). Several species of Trigonocarpum occur in the Carboniferous
rocks, such as T. olivæforme from Bolton (Plate II. Fig. 5), and T.
sulcatum from Wardie, near Edinburgh (Plate II. Fig. 6). Noeggerathia
and a few other plants, such as Flabellaria and Artisia, are referred
by Brongniart to Cycadaceæ. Flabellaria borassifolia, according
to Peach, has leaves like Yucca. Noeggerathia has pinnate leaves,
cuneiform leaflets, sometimes fan-shaped; the veins arise from the
base of the leaflets, are equal in size, and either remain simple or
bifurcate, the nervation (venation) being similar to that of some
Zamias.
The fossils of this period, referred to as Antholithes,[15] have
just been shown by Mr. Carruthers to be the inflorescence of
Cardiocarpum (Geol. Mag. Feb. 1872), and he proposes to set aside
the former name, confining it to the tertiary fossils to which it
was originally given by Brongniart, and to use the latter name.
The main axis of the inflorescence is simple, stout, and marked
externally with interrupted ridges. The axis bears in a distichous
manner sub-opposite or alternate bracts of a linear-lanceolate
form and with decurrent bases. In the axils of the bracts were
developed flower-like leaf-bearing buds, and from them proceeded
three or four linear pedicels, which terminated upwards in a somewhat
enlarged trumpet-shaped apex. To this enlarged articulating surface
was attached the fruit, to which has been given the generic name
Cardiocarpum[16] (Fig. 51). The place of attachment is indicated by
the short straight line which separates the cordate lobes at the base
of the fruit. The fruit is flattish, broadly ovate, with a cordate
base and sub-acute apex. It consists of an outer pericarp, inclosing
an ovate-acute seed. That the pericarp was of some thickness,
and formed probably a sub-indurated rind, is shown by a specimen
preserved in the round, and figured (Fig. 53 _a_). The pericarp is
open at the apex; and the elongated tubular apex of the spermoderm
passes up to this opening. The seed forms a distinct swelling in the
centre of the fruit, and a slight ridge passes up the middle to the
base of the apical opening.
[Illustration: Fig. 51-52.]
[Sidenote: Fig. 51. _Cardiocarpum Lindleyi_, Carr. Fig. 52. Do.,
Coal-measures, Falkirk.]
These fossils are believed to be an extinct form of Gymnosperms. Two
species have been described, of both of which we are able to give
figures. The first figure is from the specimens collected by Mr.
Peach at Falkirk. It is Cardiocarpum Lindleyi (Figs. 51, 52); it has
a primary axis with sub-opposite axillary axes, bearing four to six
lanceolate leaves and three or four pedicels. Primary bracts short
and arcuate. Fruit ovate-cordate, with an acute bifid apex, and a
ridge passing up the middle of the fruit.
[Illustration: Fig. 53.]
[Sidenote: Fig. 53. _Cardiocarpum anomalum_ (Carr.), natural size:
with separate fruit (_a_), twice natural size--Coal-measures,
Coalbrookdale.]
The second species is Cardiocarpum anomalum (Fig. 53) from
Coalbrookdale; it has a primary axis with alternate or sub-opposite
axillary axes, slender and elongated, bearing many linear leaves, and
several slender pedicels; primary bracts long, slender, and straight;
fruits small, margined. The somewhat magnified separate fruit (_a_)
shows the thickness of the pericarp and the enclosed seed.
[Illustration: Fig. 54.]
[Sidenote: Fig. 54. _Pothocites Grantoni_, Paterson. _a_, Spike
natural size; _b_, Portion of spike magnified; _c_, Perianth,
4-cleft, magnified.]
In the bituminous shale at Granton, near Edinburgh, Dr. Robert
Paterson discovered in 1840 a peculiar fossil plant, which he called
Pothocites Grantoni (Fig. 54, _a_). It is figured in the Transactions
of the Edinburgh Botanical Society, vol. i. March 1840. It is a spike
covered by parallel rows of flowers (Fig. 54, _b_), each apparently
with a 4-cleft calyx (Fig. 54, _c_). It was supposed to be allied to
Potamogeton or Pothos, more probably to the latter. In that case it
must be referred to the natural order Araceæ. The original specimen
is deposited in the museum at the Royal Botanic Garden, Edinburgh.
Our knowledge of the real state of the vegetation of the earth
when coal was formed must be very limited, when we reflect how
seldom the fructification of coniferous trees has been met with
in the coal-measures. A very doubtful fragment, supposed to be a
cone, is given in Lindley and Hutton's work, under the title of
Pinus anthracina; but it is believed by Carruthers to be a fragment
of a Lepidodendroid branch. Lyell never saw a fossil fir-cone of
the Carboniferous epoch, either in the rocks or museums of North
America or Europe. Bunbury never heard of any other example than
that noticed by Lindley and Hutton. Principal Dawson is disposed
to think that the suberin of cork, of epidermis in general, and of
spore-cases in particular, is a substance so rich in carbon that
it is very near to coal, and so indestructible and impermeable to
water, that it contributes more largely than anything else to the
mineral. Sir Charles Lyell remarks--"To prevent ourselves, therefore,
from hazarding false generalisations, we must ever bear in mind the
extreme scantiness of our present information respecting the flora
of that peculiar class of stations to which, in the Palæozoic era,
the coal-measures probably belonged. I have stated elsewhere my
conviction that the plants which produced coal were not drifted from
a distance, but nearly all of them grew on the spot where they became
fossil. They constituted the vegetation of low regions, chiefly the
deltas of large rivers, slightly elevated above the level of the sea,
and liable to be submerged beneath the waters of an estuary or sea
by the subsidence of the ground to the amount of a few feet. That
the areas where the carboniferous deposits accumulated were low,
is proved not only by the occasional association of marine remains,
but by the enormous thickness of strata of shale and sandstone to
which the seams of coal are subordinate. The coal-measures are often
thousands of feet, and sometimes two or three miles, in vertical
thickness, and they imply that for an indefinite number of ages a
great body of water flowed continuously in one direction, carrying
down towards a given area the detritus of a large hydrographical
basin, draining some large islands or continents, on the margins of
which the forests of the coal period grew. If this view be correct,
we can know little or nothing of the upland flora of the same era,
still less of the contemporaneous plants of the mountainous or alpine
regions. If so, this fact may go far to account for the apparent
monotony of the vegetation, although its uniform character may
doubtless be in part owing to a greater uniformity of climate then
prevailing throughout the globe. Mr. Bunbury has successfully pointed
out that the peculiarity of the carboniferous climate consisted
more in the humidity of the atmosphere and the absence of cold, or
rather the equable temperature preserved in the different seasons of
the year, than in its tropical heat; but we must still presume that
colder climates existed at higher elevations above the sea."
The plants of the coal-measures are evidently terrestrial plants.
Brongniart agrees with Lyell in thinking that the layers of coal have
in general accumulated in the situation where the plants forming
them grew. The remains of these plants covered the soil in the same
way as layers of peat, or the vegetable mould of great forests. In a
few instances, however, the plants may have been transported from a
distance, and drifted into basins. Phillips is disposed to think that
this was the general mode of formation of coal-basins. He is led to
this conclusion by observing the fragmentary state of the stems and
branches, the general absence of roots, and the scattered condition
of all the separable organs. Those who support the drift theory, look
on the coal plants as having been swept from the land on which they
grew by watery currents at different times, and deposited in basins
and large sea-estuaries, and sometimes in lakes. The snags in the
Mississippi, the St. Lawrence, and other large rivers, are given as
instances of a similar drifting process.
The vegetation of the coal epoch seems to resemble most that of
islands in the midst of vast oceans, and the prevalence of ferns
indicates a climate similar to that of New Zealand in the present
day. In speaking of the island vegetation of the coal epoch,
Professor Ansted remarks (Ancient World, p. 88)--"The whole of the
interior of the islands may have been clothed with thick forests,
the dark verdure of which would only be interrupted by the bright
green of the swamps in the hollows, or the brown tint of the ferns
covering some districts near the coasts. The forests may have been
formed by a mixture of several different trees. We would see then,
for instance, the lofty and widely-spreading Lepidodendron, its
delicate feathery fronds clothing, in rich luxuriance, branches
and stems, which are built up, like the trunk of the tree-fern, by
successive leafstalks that have one after another dropped away,
giving by their decay additional height to the stem, which might at
length be mistaken for that of a gigantic pine. There also should we
find the Sigillaria, its tapering and elegant form sustained on a
large and firm basis--enormous matted roots, almost as large as the
trunk itself, being given off in every direction, and shooting out
their fibres far into the sand and clay in search of moisture. The
stem of this tree would appear like a fluted column, rising simply
and gracefully without branches to a great height, and then spreading
out a magnificent head of leaves like a noble palm-tree. Other trees,
more or less resembling palms, and others like existing firs, also
abounded, giving a richness and variety to the scene; while one
gigantic species, strikingly resembling the Norfolk Island pine,
might be seen towering a hundred feet or more above the rest of the
forest, and exhibiting tier after tier of branches richly clothed
with its peculiar pointed spear-like leaves, the branches gradually
diminishing in size as they approach the apex of a lofty pyramid of
vegetation. Tree-ferns also in abundance might there be recognised,
occupying a prominent place in the physiognomy of vegetation,
and dotted at intervals over the distant plains and valleys, the
intermediate spaces being clothed with low vegetation of more humble
plants of the same kind. These we may imagine exhibiting their rich
crests of numerous fronds, each many feet in length, and produced
in such quantity as to rival even the palm-trees in beauty. Besides
all these, other lofty trees of that day, whose stems and branches
are now called Calamites, existed chiefly in the midst of swamps,
and bore their singular branches and leaves aloft with strange and
monotonous uniformity. All these trees, and many others that might
be associated with them, were, perhaps, girt round with innumerable
creepers and parasitic plants, climbing to the topmost branches of
the most lofty amongst them, and relieving, in some measure, the dark
and gloomy character of the great masses of vegetation."
Hugh Miller remarks--"The sculpturesque character of the nobly-fluted
Sigillarias was shared by not a few of its contemporaries.
Ulodendrons, with their rectilinear rows of circular scars, and
their stems covered with leaf-like carvings, rivalled in effect the
ornately relieved torus of a Corinthian column. Favularia, Halonia,
many of the Calamites, and all the Lepidodendrons, exhibited the most
delicate sculpturing. In walking among the ruins of this ancient
flora, the palæontologist almost feels as if he had got among the
broken fragments of Italian palaces erected long years ago, when
the architecture of Rome was most ornate, and every moulding was
roughened with ornament; and in attempting to call up in fancy the
old Carboniferous forests, he has to dwell on this peculiar feature
as one of the most prominent; and to see in the multitude of trunks
darkened above by clouds of foliage that rise upon him in the
prospect, the slender columns of an older Alhambra, roughened with
arabesque tracery and exquisite filigree work."
_FLORA OF THE PERMIAN EPOCH._
[Illustration: Fig. 55-56.]
[Sidenote: Figs. 55 and 56. _Walchia piniformis_, Sternb., a common
species in the Permian rocks of Europe. Fig. 55. Plant with leaves
and fructification. Fig. 56. Fructification, natural size.]
The nature of the vegetation during the Permian period, which is
associated with the Carboniferous, under the reign of Acrogens, has
been extensively illustrated by Goeppert. Brongniart has enumerated
the fossils in three different localities, which he refers doubtfully
to this period. 1. The flora of the bituminous slates of Thuringia,
composed of Algæ, Ferns, and Coniferæ. 2. Flora of the Permian
sandstones of Russia, comprehending Ferns, Equisetaceæ, Lycopodiaceæ,
and Noeggerathiæ. 3. Flora of the slaty schists of Lodève, composed
of Ferns, Asterophyllites, and Coniferæ. The genera of Ferns here met
with are those found in the Carboniferous epoch; the Gymnosperms are
chiefly species of Walchia and Noeggerathia (the latter is supposed
by Schimper to be a Cycad); Lepidodendron elongatum, Calamites gigas,
and Annularia floribunda, are also species of this period. Walchia
is a conifer characteristic of the Permian epoch, of which there are
eight species described (Figs. 55 and 56). It has a single seed to
each scale of the cone, and two kinds of leaves, the one short and
imbricated, the other long and spreading. Among the plants of the
Permian formation Goeppert enumerates the following:[17]--Equisetites
contractus, Calamites Suckowi, C. leioderma, Asterophyllites
equisetiformis, A. elatior, Huttonia truncata, H. equisetiformis,
many species of Psaronius, one of the filicoid plants,
Hymenophyllites complanatus, Sphenopteris crassinervia, Sagenopteris
tæniæfolia, Neuropteris imbricata, and many other species of these
genera; several species of Odontopteris, Callipteris, Cyclopteris,
Dioonopteris, Cyatheites, Alethopteris, Noeggerathia, Cordaites,
Anthodiopsis, Dictyothalamus, Calamodendron, Arthropitys; besides
species of Sigillaria, Stigmaria, and Lepidodendron. Various fruits
are also mentioned, under the names of Rhabdocarpum, Cardiocarpum,
Acanthocarpum, Trigonocarpum, and Lepidostrobus.
FOSSIL FLORA OF THE SECONDARY OR MESOZOIC PERIOD.
REIGN OF GYMNOSPERMS.
[Illustration: Fig. 57, Fig. 59.]
[Illustration: Fig. 58, Fig. 60.]
[Sidenote: Fig. 57. _Pinus sylvestris_, Scotch Fir.
Fig. 58. _Abies excelsa_, common Spruce Fir of northern
Europe.
Fig. 59. _Larix Europæa_, the Larch, indigenous on the
Alps of middle Europe.
Fig. 60. _Cedrus Libani_, Cedar of Lebanon.]
The Gymnospermous plants of the present day are included in two
natural orders, Coniferæ and Cycadaceæ. Under Coniferæ are enumerated
the various species of Pine (Fig. 57), Spruce (Fig. 58), Larch
(Fig. 59), Cedar (Fig. 60), Eutassa, Araucaria (Fig. 61), Sequoia,
Cryptomeria, Taxodium, Cypress, Juniper (Fig. 70), Salisburia,
Dacrydium, Yew (Fig. 71), etc.
[Illustration: Fig. 61, Fig. 65.]
[Illustration: Fig. 62-64.]
[Sidenote: Fig. 61. _Araucaria excelsa_, called also _Altingia_ or
_Eutassa_ or _Eutacta excelsa_, Norfolk Island Pine.
Fig. 62. Woody tubes of fir, with single rows of discs.
Fig. 63. Woody tubes of fir, with double rows of discs,
which are opposite to each other.
Fig. 64. Woody tubes of _Araucaria excelsa_, with double
and triple rows of discs, which are alternate.
Fig. 65. Longitudinal section of the stem of a Gymnosperm,
showing tubes of wood marked with punctations in one or more
rows, and a medullary ray composed of cells running across the
pleurenchyma.]
[Illustration: Fig. 66-69.]
[Sidenote: Fig. 66. Linear leaves of _Pinus Strobus_, Weymouth Pine,
in a cluster of five, with scaly sheath at the base.
Fig. 67. Cone of _Pinus sylvestris_, Scotch Fir.
Fig. 68. Cone of _Cupressus sempervirens_, common Cypress.
Fig. 69. Scale, _s_, of mature cone of _Pinus sylvestris_,
with two naked winged seeds, _m m_, at its base; _ch_ marks the
chalaza, _m_ the micropyle.]
The Coniferæ of the present day are distinguished as resinous trees
or shrubs with punctated woody tissue (Figs. 62, 63, 64, 65), linear
acerose or lanceolate parallel-veined leaves, sometimes clustered,
and having a membranous sheath at the base (Fig. 66). Male flowers
in deciduous catkins; female flowers in cones (Figs. 67, 68). The
seeds are considered by most botanists as being naked, _i.e._ not
contained in a true pistil (Fig. 69). Some of the conifers have a
succulent cone, as the juniper (Fig. 70), and the yew (Figs. 71-73)
has a succulent mass covering a single naked seed (Fig. 73). The yew
also has its pleurenchyma marked both with punctations and spiral
fibres. The arrangement of the punctations in the Coniferæ gives
characters which enable us to classify the woods into groups that
have some relation to the genera established from the reproductive
organs (see Figs. 62-65).
[Illustration: Fig. 70-73.]
[Sidenote: Fig. 70. Fruiting branch of _Juniperus communis_, common
Juniper, with linear acerose leaves and succulent cones.
Fig. 71. Branch of _Taxus baccata_, common Yew.
Fig. 72. Male flower of Yew, with bracts at the base.
Fig. 73. Fruit of Yew, consisting of a single naked seed
partially covered by a succulent receptacle.]
The natural order Cycadaceæ is not so largely represented at the
present day as it was during the Mesozoic epoch. Among the genera of
the present day are Cycas (Fig. 74), Zamia, Macrozamia, Encephalartos
(Fig. 75), Dion, Stangeria, etc. They are small palm-like trees or
shrubs, with unbranched stems, occasionally dichotomous, marked
with leaf-scars, and having large medullary rays along with pitted
woody tissue. The leaves are pinnate, except in Bowenia, which has a
bipinnate leaf. Males in cones. Females consisting of naked ovules
on the edges of altered leaves, or on the inferior surface of the
peltate apex of scales.[18]
_FLORA OF THE TRIAS AND LIAS EPOCHS._
[Illustration: Fig. 74-75.]
[Sidenote: Fig. 74. _Cycas revoluta_, one of the false Sago-plants
found in Japan.
Fig. 75. _Encephalartos (Zamia) pungens_, another
starch-yielding Cycad.]
In this reign the Acrogenous species are less numerous; the
Gymnosperms almost equal them in number, and ordinarily surpass them
in frequency. There are two periods in this reign, one in which
Coniferæ predominate, while Cycadaceæ scarcely appear; and another
in which the latter family preponderates as regards the number of
species, and the frequency and variety of generic forms. Cycadaceæ
occupied a more important place in the ancient than in the present
vegetable world. They extend more or less from the Trias formation up
to the Tertiary. They are rare in the Grès bigarré or lower strata
of the Triassic system. They attain their maximum in the Lias and
Oolite, in each of which upwards of 40 species have been enumerated,
and they disappear in the Tertiary formations. Schimper describes
13 genera of fossil Zamiæ, and about 20 Cycadeæ. He thinks that
Trigonocarpum (15 species), Rhabdocarpum (24 species), Cardiocarpum
(21 species), and Carpolithes (9 species), are all fruits of
Cycadeæ. Many supposed fossil Cycads are looked upon by Carruthers
as Coniferæ. Zamia macrocephala, or Zamites macrocephalus, or
Zamiostrobus macrocephalus, is called by him Pinites macrocephalus;
Zamia ovata, or Zamites ovatus, or Zamiostrobus ovatus, is Pinites
ovatus; Zamia Sussexiensis is Pinites Sussexiensis. Among other
species of Pinites noticed by Carruthers are Pinites oblongus,
P. Benstedi, P. Dunkeri, P. Mantellii, P. patens, P. Fittoni, P.
elongatus. It is important to notice that in an existing Cycad called
Stangeria paradoxa the veins of the pinnæ rise from a true midrib
and fork, characters which render untenable the distinction usually
relied upon between the foliage of Ferns and Cycads.
[Illustration: Fig. 76.]
[Sidenote: Fig. 76. _Schizoneura heterophylla_, one of the fossil
Coniferæ of the Triassic system.]
In Brongniart's Vosgesian period, the Grès bigarré, or the Red
Sandstones and Conglomerates of the Triassic system, there is a
change in the flora. Sigillarias and Lepidodendrons disappear, and
in their place we meet with Gymnosperms, belonging to the genera
Voltzia, Haidingera, Zamites, Ctenis, Æthophyllum, and Schizoneura
(Fig. 76). The genus Voltzia is confined to the Trias, and though a
true conifer, it is not easy to correlate it with any living form. It
is apparently Abietineous, having two seeds to each scale, but they
are placed on the dilated upper portion of the scale. The leaves are
of two kinds, the one broad and short, and the other at the tops of
the branches long and linear. Species of Neuropteris, Pecopteris,
and other acrogenous coal genera are still found, along with species
of Anomopteris and Crematopteris--peculiar Fern-forms, which are
not found in later formations. Stems of arborescent Ferns are more
frequent than in the next period.
[Illustration: Fig. 77.]
The Jurassic period of Brongniart embraces the Keupric period or
variegated marls of the Triassic system, the Liassic epoch, the
Oolitic and the Wealden. The flora of the Keupric epoch differs from
that of the Grès bigarré of the Vosges. The Acrogens are changed as
regards species, and frequently in their genera. Thus we have the
genera Camptopteris, Sagenopteris, and Equisetum. Among Gymnosperms,
the genera Pterophyllum and Taxodites occur.
[Illustration: Fig. 78-79.]
[Sidenote: Figs. 77 to 81. Cycadaceæ of the Jurassic epoch of
Brongniart, and of the Oolite. Fig. 77. Zamites, one of the fossil
Cycadaceæ. Fig. 78. _Pterophyllum Pleiningerii_, leaf of a fossil
Cycad. Fig. 79. _Nilssonia compta_ (_Pterophyllum comptum_ of
Lindley and Hutton), from the Oolite of Scarborough. Lower part of
the pinnatifid leaf, with blunt almost square divisions. There are
numerous veins, slightly varying in thickness; while in Pterophyllum
there are numerous veins of equal thickness, in Cycadites there is a
solitary vein forming a thick midrib. Fig. 80. _Palæozamia pectinata_
(_Zamia pectinata_ of Brongniart, and Lindley and Hutton), a pinnated
leaf, with a slender rachis. The pinnæ are linear, somewhat obtuse,
with slender equal ribs. It is found in the Oolite of Stonesfield
(Lindley and Hutton).]
[Illustration: Fig. 80.]
In the Lias the essential characters of the flora are the
predominance of Cycadaceæ, in the form of species of Cycadites,
Otozamites, Zamites (Fig. 77), Ctenis, Pterophyllum (Fig. 78),
and Nilssonia (Fig. 79), Palæozamia (Fig. 80), and the existence
among the Ferns of many genera with reticulated venation, such as
Camptopteris and Thaumatopteris, some of which began to appear at
the Keupric epoch. Coniferous genera, as Brachyphyllum (Fig. 81),
Taxodites, Palissya, and Peuce, are found. In the Lias near Cromarty,
Miller states that he found a cone with long bracts like those of
Pinus bracteata.
_FLORA OF THE OOLITIC EPOCH._
In the Oolitic epoch the flora consists of numerous Cycadaceæ and
Coniferæ, some of them having peculiar forms. Its distinctive
characters are, the rarity of Ferns with reticulated venation,
which are so numerous in the Lias, the frequency of the Cycadaceous
genera Otozamites and Zamites, which are most analogous to those
now existing; the occurrence of a remarkable group presenting very
anomalous structure in their organs of reproduction, to which
Carruthers has given the name of Williamsonia; and the diminution
of Ctenis, Pterophyllum, Palæozamia, and Nilssonia, genera far
removed from the living kinds; and lastly, the greater frequency
of the coniferous genera, Brachyphyllum and Thuites, which are
much more rare in the Lias. In the Scottish Oolite at Helmsdale,
Miller detected about 60 species of plants, including Cycadaceæ
and Coniferæ, with detached cones, and Fern-forms resembling
Scolopendrium. He also discovered a species of Equisetum, and what he
supposed to be a Calamite.
[Illustration: Fig. 81-82.]
[Sidenote: Fig. 81. _Brachyphyllum mammillare_, a Coniferous plant of
the Oolitic system, Yorkshire.
Fig. 82. _Equisetum columnare_, a fossil species of the
Oolite of Yorkshire.]
[Illustration: Fig. 83-85.]
[Sidenote: Fig. 83. _Araucarites sphærocarpus_, Carr., found in the
inferior Oolite at Bruton, Somersetshire.
Fig. 84. Termination of a scale of _Araucarites
sphærocarpus_, Carr.
Fig. 85. Section of a scale of _Araucarites sphærocarpus_,
Carr., showing the size and position of the seed.]
[Illustration: Fig. 86-87.]
[Sidenote: Fig. 86. The _Dirt-bed_ of the Island of Portland,
containing stumps of fossil Cycadaceæ in an erect position.
Fig. 87. _Cycadoidea megalophylla_ (_Mantellia nidiformis_
of Brongniart), a subglobose depressed trunk, with a concave apex,
and with the remains of the petioles disposed in a spiral manner, the
markings being transversely elliptical. It is found in the Oolite of
the Island of Portland, in a silicified state.]
There is an absence of true coal-fields in the secondary formations
generally; but in some of the Oolitic series, as in the lower Oolite
at Brora, in Sutherlandshire, and in the north-east of Yorkshire,
and the Kimmeridge clay of the upper Oolite, near Weymouth, there
are considerable deposits of carbonaceous matter, sometimes forming
seams of coal which have been worked for economic purposes.[19] Some
suppose that the Brora coal was formed chiefly by Equisetum columnare
(Fig. 82). In the sandstones and shales of the Oolitic series,
especially in the lower Oolite of the north of England, as at Whitby
and Scarborough, as well as in Stonesfield slate, the Portland Crag
of the middle, and the Portland beds of the upper Oolite, numerous
fossil plants are found. Peuce Lindleyana is one of the Coniferæ
of the lower Oolite. Beania (Plate II. Fig. 2) is a Cycadaceous
fossil from the Oolite of Yorkshire (Carruthers, Geol. Mag. vi. 91).
Araucarites sphærocarpus (Figs. 83, 84, 85) is found in the inferior
Oolite, and separate scales of Araucarian fruits occur in the Oolitic
shales of Yorkshire (Araucarites Phillipsii, Plate II. Fig. 11), and
in the "slate" at Stonesfield (A. Brodiei, Plate II. Fig. 10). The
upper Oolite at Portland contains an interesting bed, about a foot in
thickness, of a dark brown substance. This is the _Dirt-bed_ (Fig.
86) made up of black loam, which, during the Purbeck period, formed
a surface soil which was penetrated by the roots of trees, fragments
of whose stems are now found in it fossilised. These consist of
an assemblage of silicified stumps or stools of large trees, from
1-3 feet high, standing in their original position, with the roots
remaining attached to them, and still penetrating the earth in which
they grew. Besides the erect trunks many stems have been broken and
thrown down, and are buried in a horizontal position in the bed.
They belong to Coniferæ and Cycadaceæ. One of these is Mantellia
nidiformis, shown in Fig. 87. Carpolithes conicus and C. Bucklandi
are fruits found in the Oolite. Some look upon them as fruits of
palms.
[Illustration: Fig. 88-89.]
[Sidenote: Fig. 88. _Kaidacarpum ooliticum_, Carr., fruit of a fossil
allied to Pandanaceæ, from the great Oolite near Northampton.
Fig. 89. _Pandanus odoratissimus_, Screw-pine, with
adventitious roots.]
Several species of Pandanaceous fruits have been found in Oolitic
strata. Buckland described one of them as Podocarya, which is
remarkable, as it consists of a single but many-seeded drupe. To
another form, more nearly allied to the existing plants, Carruthers
has given the name Kaidacarpum, and has described three species.
These fruits are made up of a large number of single-seeded drupes.
The species figured (Fig. 88) is from the great Oolite, near
Northampton. In Fig. 89 a representation is given of one of the
Pandanaceæ, the screw-pines of the present day.
_FLORA OF THE WEALDEN EPOCH._
[Illustration: Fig. 90.]
[Sidenote: Fig. 90. Fossil Wood, _Abietites Linkii_. A Coniferous
plant from the Wealden, showing punctated woody tissue and medullary
rays.]
The flora of the Wealden epoch is characterised in the south of
England by the abundance of the fern called Lonchopteris Mantellii,
and in Germany by the predominance of the Conifer denominated
Abietites Linkii (Fig. 90), and the presence of Araucarites
Pippingfordensis, as well as by numerous Cycadaceæ, such as species
of Cycadites, Zamites, Pterophyllum, Mantellia, Bucklandia, and a
remarkable genus having a fleshy fruit, and related to the ordinary
Cycadaceæ as Taxus is to the other Coniferæ, which has been fully
described in the Linn. Trans., under the name of Bennettites (Plate
II. Fig. 3). In the Wealden at Brook Point, Isle of Wight, Cycads
have been detected allied to Encephalartos. The fruits of them are
described by Carruthers as Cycadeostrobus. He describes the following
species:--Cycadeostrobus ovatus (Plate II. Fig. 1), C. truncatus, C.
tumidus, C. elegans, C. Walkeri, C. sphæricus, in the Oxford clay of
Wiltshire; C. primævus in the inferior Oolite at Burcott Wood and
Livingston, and C. Brunonis. Mantell states that he has found 40 or
50 fossil cones in the Wealden of England; they belong either to the
genus Cycadeostrobus or to the pines mentioned below as occurring in
the Wealden. The Wealden fresh-water formation terminates the reign
of Gymnosperms. Carruthers gives the following list of the remains of
Coniferæ which have been found in the secondary strata of Britain,
excluding the Trias:--
Upper Chalk.--Wood in flint nodules.
Upper Greensand.--Foliage and cone of Sequoiites Woodwardii; cone
of Pinites oblongus.
Gault.--Cones of Pinites gracilis and P. hexagonus, Sequoiites
Gardneri and S. ovalis.
Lower Greensand.--Water-worn and bored pieces of wood; cones of
Pinites Benstedi, P. Sussexiensis, and P. Leckenbyi.
Wealden.--Driftwood, foliage of Abietites Linkii; cones of
Pinites Dunkeri, P. Mantellii, P. patens, and P. Fittoni, and
of Araucaria Pippingfordensis; foliage (and drupes?) of Thuites
Kurrianus.
Purbeck.--Fossil forest _in situ_ at Isle of Portland; cone
"nearly related to Araucaria excelsa" in the Dirt-bed.
Portland Stone.--Driftwood Araucarites.
Kimmeridge Clay.--Cone of Pinites depressus.
Oxford Clay.--Driftwood and foliage of Araucarites.
Great Oolite.--Driftwood of Araucarites; foliage of Thuites
acutifolius, T. articulatus, T. cupressiformis, T. divaricatus,
and T. expansus, and of Taxites podocarpoides; detached cones at
Helmsdale, Sutherland.
Inferior Oolite.--Wood of Peuce Eggensis (Tertiary according to
Geikie); foliage of Brachyphyllum mammillare, Cryptomerites?
divaricatus, and Palissya? Williamsonis; cones of Araucarites
sphærocarpus, A. Brodiei, and A. Phillipsii. Pinites primæva
(Lindl. and Hutt.) is a Cycadean fruit.
Lias.--Wood of Pinites Huttonianus and P. Lindleyanus; foliage
of Araucaria peregrina and Cupressus latifolia; cone of Pinites
elongatus, and "cone with long bracts like those of Pinus
bracteata," from Cromarty.
Carruthers gives the following arrangement of fossil Cycadaceæ in
the Transactions of the Linn. Soc. vol. xxvi.--Firstly, the Cycadeæ:
including the genus Bucklandia, Presl; and species B. anomala, B.
Mantellii, B. squamosa, B. Milleriana--the two first-named species
being from the Wealden, and the two last-named from the Oolite.
Secondly, the Zamieæ: including the genus Yatesia, Carr.; and
species Y. Morrisi, Lower Cretaceous; Y. gracilis, Lias; Y. crassa,
M. Oolite; Y. Joassiana, M. Oolite; the genus Fittonia, Carr., and
species F. squamata, U. Cretaceous; the genus Crossozamia, Pomel,
and species C. Moreaui, Pomel, Jurassic, and C. Buvignieri, Pomel,
Jurassic--both from St. Michel, France. Thirdly, the Williamsonieæ:
including the genus Williamsonia, Carr.; and species W. gigas, W.
pecten, W. hastula, all from the inferior Oolite. Fourthly, the
Bennettiteæ: including the genus Bennettites, Carr., and species
B. Saxbyanus, Wealden; B. Gibsonianus, Lr. Greensand; B. maximus,
Wealden; B. Portlandicus, Lr. Purbeck; and B. Peachianus, M.
Oolite; the genus Mantellia, Brong., and species M. nidiformis, M.
intermedia, M. microphylla, from the Lr. Purbeck; and M. inclusa,
from the Lr. Cretaceous; the genus Raumeria, Goeppert, and species R.
Reichenbachiana, from Galicia, and R. Schulziana from Silesia.
FOSSIL FLORA OF THE TERTIARY OR CAINOZOIC PERIOD,
(INCLUDING THE CRETACEOUS EPOCH).
REIGN OF ANGIOSPERMS.
This reign is characterised by the appearance of Angiospermous
Dicotyledons, plants which constitute more than three-fourths of the
species of the existing flowering plants of the globe, and which
appear to have acquired the predominance from the commencement of the
Tertiary epoch. They are plants with seeds contained in seed-vessels,
and each seed with two cotyledons. These plants, however, appear even
at the beginning of the Cretaceous period. In this reign, therefore,
Brongniart includes the upper Secondary period, or the Cretaceous
system, and all the Tertiary period. The Cretaceous may be considered
as a sort of transition period between the reign of Gymnosperms and
Angiosperms.
_FLORA OF THE CHALK._
The Chalk flora is characterised by the Gymnospermous almost
equalling the Angiospermous Dicotyledons, and by the existence of a
considerable number of Cycadaceæ, which do not appear in the Tertiary
period. The genus Credneria is one of the characteristic forms. In
this period we find Algæ represented by Cystoseirites, Confervites,
Sargassites, and Chondrites; Ferns by peculiar species of Pecopteris
and Protopteris; Naiadaceæ by Zosterites; Palms, by Flabellaria and
Palmacites; Cycadaceæ by Cycadites, Zamites, Microzamia, Fittonia,
and Bennettites; Coniferæ, by Brachyphyllum, Widdringtonites,
Cryptomeria, Abietites, Pinites, Cunninghamites, Dammarites,
Araucarites; and Angiospermous Dicotyledons, by Comptonites, Alnites,
Carpinites, Salicites, Acerites, Juglandites, and Credneria. At the
base of the Tertiary period there are deposits of Algæ of a very
peculiar form, belonging to the genera Chondrites and Munsteria. No
land plants have been found mingled with these marine species.
[Illustration: Fig. 91.]
[Sidenote: Fig. 91. _Sequoiites ovalis._ Large cone.]
In the Gault, near Folkestone, an interesting association of
coniferous fruits has been found, consisting of two species of
Sequoia, along with two of Pinus. The pines belong to the same group
as those which now grow with the Wellingtonias in California, showing
the remarkable fact that the coniferous vegetation of the high lands
of the Upper Cretaceous period had a _facies_ similar to that now
existing in the mountains on the west of North America. We figure
both the species of Sequoiites--viz. S. ovalis (Fig. 91), a large
cone, and S. Gardneri (Plate II. Fig. 7). In the present day there
are two species of the genus Sequoia--viz. S. gigantea (Wellingtonia
gigantea) and S. sempervirens.[20] In the Lower Greensand a
remarkably fine cone belonging to the same group as the Cedar has
been found. This is the Pinites Leckenbyi (Plate II. Fig. 4). A
section exhibits the seeds in their true position, some of which are
preserved so as to exhibit the form and position of the embryo.
[Illustration: Fig. 92.]
[Sidenote: Fig. 92. _Pinites ovatus_ (_Zamia ovata_ of Lindley and
Hutton), an ovate cone with a truncated base and obtuse apex, nearly
allied to the stone-pine.]
The Tertiary period is characterised by the abundance of
Angiospermous Dicotyledons and of Monocotyledons, more especially of
Palms. By this it is distinguished from the more ancient periods.
Angiosperms at this period greatly exceed Gymnosperms. Cycadaceæ
are very rare, if not completely wanting, in the European Tertiary
strata, and the Coniferæ belong to genera of the temperate regions.
In the lower Tertiaries Carruthers has found a fossil Osmunda, and
the existence of a group of Pines having cones with a very thick
apophysis. From their remarkable external aspect, these cones
had been considered to be Cycadean, but their internal structure
indicates that they are coniferous. Pinites ovatus is one of
these cones (Fig. 92). The Cupressineæ are found in the Tertiary
beds only. Taxodieæ are represented by Sequoiites (Plate II. Fig.
7) in the Cretaceous and Eocene strata. Peuce australis of Van
Diemen's Land and P. Pritchardi of Ireland are Tertiary plants.
The Peuce of Eigg (P. Eggensis), according to Geikie, is also
Tertiary, and not Oolitic. Isoetes is mentioned by Schimper as a
Tertiary genus. Although the vegetation throughout the whole of the
Tertiary period presents pretty uniform characters, still there
are notable differences in the generic and specific forms, and in
the predominance of certain orders at different epochs. Brongniart
does not entirely agree with Unger as to these epochs. Many of the
formations classified by Unger in the Miocene division he refers with
Raulin to the Pliocene. He divides the Tertiary period, as regards
plants, into the Eocene, Miocene, and Pliocene epochs, and gives the
following comparative results from an examination of their floras:--
+-----------------+---------------+----------------+-----------------+
| Classes and | | | |
| Sub-Classes. | Eocene Epoch. | Miocene Epoch. | Pliocene Epoch. |
+-----------------+---------------+----------------+-----------------+
| Thallogenæ | 16 | 6 | 6 |
| Acrogenæ | 17 | 4 | 7 |
| Monocotyledones | 33 | 26 | 4 |
| Dicotyledones-- | | | |
| Gymnospermæ | 40 | 19 | 31 |
| Angiospermæ | 103 | 78 | 164 |
+-----------------+---------------+----------------+-----------------+
| | 209 | 133 | 212 |
+-----------------+---------------+----------------+-----------------+
_FLORA OF THE EOCENE EPOCH._
In the Eocene formation the fossil fruits of the Isle of Sheppey
increase the number of Phanerogamous plants, only a small proportion
of which have as yet been described. This is an exceptional locality,
and the deposit in which the fruits occur is probably the silt found
at the mouth of a large river which flowed, like the Nile, from
tropical regions towards the north. The number of plants as given by
Brongniart is much smaller than that mentioned by Unger (p. 23). The
latter includes in his enumeration a considerable amount of uncertain
species.
[Illustration: Fig. 93.]
[Sidenote: Fig. 93. _Palmacites Lamanonis_. Fan-shaped (flabellate)
leaf of a Palm.]
The Eocene epoch in general is characterised by the predominance of
Algæ and marine Naiadaceæ, such as Caulinites and Zosterites; by
numerous Coniferæ, the greater part resembling existing genera among
the Cupressineæ, and appearing in the form of Juniperites, Thuites,
Cupressinites (Plate II. Figs. 8, 9), Callitrites, Frenelites, and
Solenostrobus; by the existence of a number of extra-European forms,
especially of fruits, such as Nipadites, Leguminosites, Cucumites,
and Hightea; and by the presence of some large species of Palm
belonging to the genera Flabellaria and Palmacites (Fig. 93).
[Illustration: Fig. 94.]
[Sidenote: Fig. 94. _Osmunda regalis_, Royal Fern, having a bipinnate
frond and fructification in a spike-like form, the branches bearing
sporangia.]
Unger says that the Eocene flora has resembled in many respects that
of the present Australian vegetation. He gives the following genera
as occurring at the Eocene epoch:--Araucaria, Podocarpus, Libocedrus,
Callitris, Casuarina, Pterocarpus, Drepanocarpus, Centrolobium,
Dalbergia, Cassia, Cæsalpinia, Bauhinia, Copaifera, Entada, Acacia,
Mimosa, Inga. (Seemann's Journal of Bot. vol. iii. p. 43.) Amber is
considered to be the produce of many Coniferæ of this epoch, such
as Peuce succinifera or Pinites succinifera, and Pinus Rinkianus. It
occurs in East Prussia in great quantity, and it is said that many
pieces of fossil wood occur there, which, when moderately heated,
give out a decided smell of amber. Connected with these beds are
found cones belonging to Pinites sylvestrina and P. Pumilio-miocena,
species nearly allied to the living species; others to Pinites
Thomasianus and P. brachylepis. Goeppert contrasts the present flora
of Germany and that of the Amber epoch as follows:--
German Flora. Amber Flora.
Cryptogameæ 6800 60
Phanerogameæ 3454 102
and gives the following specimens of two of the orders:--
Cupuliferæ 12 10
Ericaceæ 23 24
(See remarks by Goeppert on the Amber Flora, etc., Edin. N. Phil.
Journ. lvi. 368; and Quart. Journ. Geol. Soc. x. 37.) In the lower
Eocene of Herne Bay, Carruthers noticed a fern like Osmunda (Fig.
94), which he calls Osmundites Dowkeri (Plate I. Figs. 8, 9). This
specimen was silicified; starch grains contained in its cells, and
the mycelium of a parasitic fungus traversing some of them, were
perfectly preserved. Berkeley has detected in amber fossil fungi,
which he has named Penicillium curtipes, Brachycladium Thomasinum,
and Streptothrix spiralis.[21] Some Characeæ are also met with, as
Chara medicaginula and C. prisca, with a fossil called Gyrogonites,
the nucule or the fructification of these plants. Carpolithes ovatus,
a minute seed-vessel, occurs in the Eocene beds of Lewisham. Another
small fruit, of a similar nature, called Folliculites minutulus,
occurs in the Bovey Tracey coal, which belongs to the Tertiary beds.
_FLORA OF THE MIOCENE EPOCH._
[Illustration: Fig. 95.]
[Sidenote: Fig. 95. _Comptonia acutiloba_, apparently the leaf of
a plant belonging to the natural order Proteaceæ, which abound in
Australia, and are also found at the Cape of Good Hope at the present
day.]
[Sidenote: Figures 96 to 99 show the leaves of plants belonging to
the Miocene epoch.]
[Illustration: Fig. 96-97.]
[Illustration: Fig. 98.]
[Sidenote: Fig. 96. _Acer trilobatum_, a three-lobed palmate leaf,
like that of the Maple, with the lobes unequal, inciso-dentate, the
lateral ones spreading, found at Œningen. Fig. 97. _Ulmus Bronnii_,
a petiolate leaf, like that of the Elm, unequally ovato-acuminate,
feather-veined and toothed, found in Bohemia. Fig. 98. _Rhamnus
Aizoon_, a petiolate elliptical obtuse feather-veined leaf, with an
entire margin, found in Styria.]
The most striking characters of the Miocene epoch consist in the
mixture of exotic forms of warm regions with those of temperate
climates. Unger says that it resembles that of the southern part
of North America. Thus we meet with Palms, such as species of
Flabellaria and Phœnicites, a kind of Bamboo called Bambusium
sepultum; Lauraceæ, as Daphnogene and Laurus; Combretaceæ, as
Getonia and Terminalia; Leguminosæ, as Phaseolites, Desmodophyllum,
Dolichites, Erythrina, Bauhinia, Mimosites, and Acacia--all plants
having their living representatives in warm climates; Echitonium,
Plumiera, and other Apocynaceæ of equatorial regions; Comptonia (Fig.
95), a Proteaceous genus, and Steinhauera, a Cinchonaceous genus;
mingled with species of Acer (Fig. 96), Ulmus (Fig. 97), Rhamnus
(Fig. 98); and Amentiferous forms, such as Myrica, Betula, Alnus
(Fig. 99), Quercus, Fagus, Carpinus, all belonging to temperate
and cold climates. The statements as to the occurrence of Pinus
sylvestris and Betula alba among the Miocene fossils have not been
founded on complete data. It is by no means easy, even in the present
day, to distinguish fragments of dried specimens of Pinus Pumilio
from those of P. sylvestris, and from a great many other Pines.
The difficulty is still greater in fossils (Hook. Kew Journ. v.
413). There are a very small number of plants belonging to orders
with gamopetalous corollas. In the Miocene formation of Lough
Neagh in Ireland, and of Mull in Scotland, silicified trunks of
considerable size have been found. The Irish silicified wood has been
denominated Cupressoxylon Pritchardi from its apparent resemblance
to the Cypress. As connected with the Miocene epoch, we may notice
the leaf-beds found at Ardtun, in the island of Mull, by the Duke
of Argyll.[22] Above and below these beds basalt occurs, and there
are peculiar tuff-beds alternating with the leafy deposits. These
tuff-beds were formed by the deposit of volcanic dust in pools
probably of fresh water. They contain fragments of chalk and flint.
The leaves are those of plants allied to the Yew, Rhamnus, Plane, and
Alder, along with the fronds of a peculiar Fern, and the stems of an
Equisetum. The genera are Taxites or Taxodites (Fig. 100), Rhamnites
(Fig. 101), Platanites, Alnites, Filicites, and Equisetum (Fig.
102). In the leaf-beds at Bournemouth Mr. Wanklyn detected several
ferns. One is a species of Didymosorus, and shows distinct venation
and fructification. Fossilised wood was found in the Arctic Regions
by Captain M'Clure. At the N.W. of Banks Land he found trees with
trunks 1 foot 7 inches in diameter.
[Illustration: Fig. 99-101.]
[Sidenote: Fig. 99. _Alnus gracilis_, an ovate-oblong leaf, like that
of the Alder, found in Bohemia.]
[Sidenote: Figures 100, 101, 102, exhibit fragments of plants which
occur in the leaf-bed at Ardtun Head, in Mull, and which is referred
to the Miocene epoch. The figures are from the Duke of Argyll's
paper.]
[Sidenote: Fig. 100. _Taxites_, or perhaps _Taxodites Campbellii_, a
branch with leaves resembling those of the Yew, or rather those of
Taxodium.
Fig. 101. _Rhamnites multinervatus_, a leaf resembling
that of Rhamnus.]
[Illustration: Fig. 102.]
[Sidenote: Fig. 102. _Equisetum Campbellii_, a stem like that of an
Equisetum of the present day.]
Dr. Oswald Heer[23] has examined the plants preserved in the lignite
beds of Bovey Tracey, in Devonshire, and he finds that they belong
to the Miocene formation. There is a remarkable coincidence between
this and several of the continental fossil floras, such as those
of Salzhauser in the Wetterau, Manosque in Provence, and of some
parts of Switzerland. Bovey Tracey has no species in common with
Iceland, although the Tertiary flora of Iceland belongs to the
same period. Two of its species (Corylus MacQuarrii and Platanus
aceroides) have been found in the Miocene of Ardtun Head. Even the
genera are distinct, with the exception of Sequoia and Quercus. The
Bovey Tracey flora has a much more southern character, corresponding
entirely with that of the Lower Miocene of Switzerland. It contains
three species of Cinnamon, one Laurel, evergreen Figs, one Palm, and
large Ferns, thus manifesting a subtropical climate. One of the most
important plants is Sequoia Couttsiæ, a Conifer which supplies a link
between S. Langsdorfii and S. Sternbergi, the widely-distributed
representatives of S. sempervirens and S. gigantea (Wellingtonia),
which are Californian trees. Among other characteristic plants may be
mentioned Cinnamomum lanceolatum and C. Scheuchzeri; Quercus Lyellii,
an evergreen oak; species of evergreen fig (Ficus Falconeri and F.
Pengellii), Palmacites Dæmonorops, a prickly twining Rotang-palm;
species of Vine (Vitis Hookeri and V. Britannica); Pecopteris
lignitum, a large tree-fern; species of Nyssa, at present confined
to North America. Among other plants recorded by Heer in his paper
are the following:--Laurus primigenia, Daphnogene Ungeri, species
of Dryandroides, Andromeda, Vaccinium acheronticum, Echitonium
cuspidatum, Gardenia Wetzleri, species of Anona, Nymphæa Doris,
Carpolithes Websteri, C. Boveyanus, and other species. In the
post-tertiary white clay of Bovey Tracey, Salix cinerea, and a
species allied to S. repens, as well as Betula nana, are found.
The Arctic fossil flora (Miocene), according to Heer, amounts to
162 species: Cryptogamia, 18 species, of which 9 are large ferns;
Phanerogamia, Coniferæ, 31; Monocotyledons, 14; Dicotyledons, 99.
Among the Coniferæ are--Pinus M'Clurii, Sequoia Langsdorffii,
Sternbergi, and Couttsiæ, Taxodium dubium, Glyptostrobus europæus,
Thujopsis europæa. Among leafy trees are--Fagus Deucalionis, Quercus
Olafseni, Platanus aceroides, willows, beeches, Acer, Otopteryx,
tulip-tree, walnuts, Magnolia Inglefieldi, Prunus Scottii, Tilia
Malmgreni, Corylus M'Quarrii, Alnus Kefersteinii, Daphnogene Kannii,
probably one of the Lauraceæ; and among Proteaceæ, MacClintockia? and
Hakea. In Greenland are found species of Rhamnus, Paliurus, Cornus,
Ilex, Cratægus, Andromeda, Myrica, Ivy, and Vine. From the flora of
Spitzbergen, in the Miocene epoch, we may conclude that under 79°
N. lat. the mean temperature of the year may have been 41° Fahr.,
while at the same epoch that of Switzerland was 69°·8 Fahr.; judging
from the analogy of floras, it appears that the mean temperature
has fallen 6°·9. From this it follows that at Spitzbergen, at
78° N. lat., the mean temperature was perhaps 41°·9 Fahr. In
Greenland, at 70°, it would be 49°·1 Fahr., and in Iceland and on
the Mackenzie, in lat. 65°, it would be 52°·7 Fahr. At the Miocene
epoch the temperature seems to have been much more uniform, the
mean heat diminishing much more gradually in proportion as the pole
was approached. The isothermal line of 32° Fahr. might have fallen
upon the pole, while now it is situated under 58° N. (See Heer's
conclusions as to changes of temperature depending on proportion
of sea and land, eccentricity of the earth, and the earth moving
through warm and cold spaces in the universe--Ann. Nat. Hist. 4th
ser. i. 66.)
In speaking of the Polar flora of former epochs, Heer says that every
plant executes a slow and continuous migration. These migrations,
the starting-point of which is the distant past, are recorded in
the rocks; and the interweaving of the carpets of flowers which
adorn our present creation retraces them for us in its turn. For
the vegetation of the present day is closely connected with that of
preceding epochs; and throughout all these vegetable creations reigns
_one_ thought, which not only reveals itself around us by thousands
upon thousands of images, but strikes us everywhere in the icy
regions of the extreme north. Organic nature may become impoverished
there, and even disappear when a cold mantle of ice extends over the
whole earth; but where the flowers die the rocks speak, and relate
the marvels of creation; they tell us that even in the most distant
countries, and in the remotest parts, nature was governed by the same
laws and the same harmony as immediately around us.[24]
_FLORA OF THE PLIOCENE EPOCH._
The flora of the Pliocene epoch has a great analogy to that of the
temperate regions of Europe, North America, and Japan. We meet with
Coniferæ, Amentiferæ, Rosaceæ, Leguminosæ, Rhamnaceæ, Aceraceæ,
Aquifoliaceæ, Ericaceæ, and many other orders. There is a small
number of Dicotyledons with gamopetalous corollas. The twenty
species with such corollas recognised by Brongniart are referred to
the Hypogynous Gamopetalous group of Exogens, which in the general
organisation of the flowers approach nearest to Dialypetalæ. In
this flora there is the predominance of Dicotyledons in number and
variety; there are few Monocotyledons. No species appear to be
identical, at least with the plants which now grow in Europe. Thus
the flora of Europe, even at the most recent geological epoch of the
Tertiary period, was very different from the European flora of the
present day.
Taking the natural orders which have at least four representatives,
Raulin[25] gives the following statement as to the Tertiary flora
of central Europe. The Eocene flora of Europe is composed of 128
species, of which 115 belong to Algæ, Characeæ, Pandanaceæ, Palmæ,
Naiadaceæ, Malvaceæ, Sapindaceæ, Proteaceæ, Papilionaceæ, and
Cupressineæ. The Miocene flora has 112 species, of which 69 belong to
Algæ, Palmæ, Naiadaceæ, Apocynaceæ, Aceraceæ, Lauraceæ, Papilionaceæ,
Platanaceæ, Quercineæ, Myricaceæ, and Abietineæ. The Pliocene
flora has 258 species, of which 226 belong to Algæ, Fungi, Musci,
Filices, Palmæ, Ericaceæ, Aquifoliaceæ, Aceraceæ, Ulmaceæ, Rhamnaceæ,
Papilionaceæ, Juglandaceæ, Salicaceæ, Quercineæ, Betulaceæ, Taxaceæ,
Cupressineæ, and Abietineæ. The Eocene species are included in
genera which belong at the present day to inter-tropical regions,
comprising in them India and the Asiatic islands of Australia. Some
are peculiar to the Mediterranean region. The aquatic plants, which
form almost one-third of the flora, belong to genera now peculiar to
the temperate regions of Europe and of North America, or occurring
everywhere. The Miocene species belong to genera, of which several
are found in India, tropical America, and the other inter-tropical
regions, but which for the most part inhabit the sub-tropical and
temperate regions, including the United States. Some of the genera
are peculiar to the temperate regions. The aquatic genera, poor in
species, occur everywhere, or else solely in the temperate regions.
The Pliocene species belong to genera which almost all inhabit the
temperate regions, either of the old continent or of the United
States. A few only are of genera existing in India, Japan, and the
north of Africa. These various floras, which present successively
the character of those of inter-tropical, sub-tropical, and
temperate regions, seem to indicate that central Europe has, since
the commencement of the Tertiary period, been subjected, during
the succession of time, to the influence of these three different
temperatures. It would appear, then, Raulin remarks, that the climate
of Europe has during the Tertiary period gradually become more
temperate.
Brown coal occurs in the upper Tertiary beds, and in it vegetable
structure is easily seen under the microscope. Goeppert, on examining
the brown coal deposits of northern Germany and the Rhine, finds that
Coniferæ predominate in a remarkable degree; among 300 specimens of
bituminous wood collected in the Silesian brown coal deposits alone,
only a very few other kinds of Exogenous wood occur. This seems
remarkable, inasmuch as in the clays of the brown coal formation
in many other places leaves of deciduous Dicotyledonous trees have
been found; and yet the stems on which we may suppose them to have
grown are wanting. The leaves have been floated away from the place
where they grew by a current of water which was not powerful enough
to transport the stems. The coniferous plants of these brown coal
deposits belong to Taxineæ and Cupressineæ chiefly; among the plants
are Pinites protolarix and Taxites Ayckii. Many of the Coniferæ
exhibit highly compressed, very narrow annual rings, such as occur in
Coniferæ of northern latitudes. Goeppert has described a trunk, or
rather the lower end of a trunk, of Pinites protolarix, discovered
in 1849 in the brown coal of Laasan in Silesia. It was found in a
nearly perpendicular position, and measured more than 32 feet in
circumference. Sixteen vast roots ran out almost at right angles from
the base of the trunk, of which about four feet stood up perfect in
form, but stripped of bark. Unfortunately the interior of the stem
was almost entirely filled with structureless brown coal, so that
only two cross sections could be obtained from the outer parts, one
sixteen inches, the other three feet six inches broad. In the first
section Goeppert counted 700, in the second 1300 rings of wood, so
that for the half-diameter of 5½ feet, at least 2200 rings must have
existed. As there is every reason to believe that the rings were
formed in earlier ages just as the annual zones are now, this tree
would be from 2200 to 2500 years old. Exogenous stems in lignite are
often of great size and age. In a trunk near Bonn, Nöggerath counted
792 annual rings. In the turf bogs of the Somme, at Yseux near
Abbeville, a trunk of an oak-tree has been found above 14 feet in
diameter.
_GENERAL CONCLUSIONS._
We have thus seen that the vegetation of the globe is represented
by numerous distinct floras connected with the different periods
of its history, and that the farther back we go, the more are the
plants different from those of the present day. There can be no doubt
that there have been successive deposits of stratified rocks, and
successive creations of living beings. We see that animals and plants
have gone through their different phases of existence, and that their
remains in all stages of growth and decay have been imbedded in rocks
superimposed upon each other in regular succession. It is impossible
to conceive that these were the result of changes produced within the
limits of a few days. Considering the depth of stratification, and
the condition and nature of the living beings found in the strata at
various depths, we must conclude (unless our senses are mocked by
the phenomena presented to our view) that vast periods have elapsed
since the Creator in the beginning created the heavens and the earth.
How far it may be possible in the future to correlate the history
of the earth inscribed on its rocky tablets and deciphered by the
geologist, and that short narrative which forms the introduction to
the Sacred Volume, it is too difficult to say. At present there are
no satisfactory materials for such a correlation; but one thing is
certain, that both Revelation and Geology testify with one voice to
the work of a Divine Creator.
"Who shall declare (Hugh Miller remarks) what through long ages the
history of creation has been? We see at wide intervals the mere
fragments of successive Floras; but know not how, what seem the
blank interspaces, were filled; or how, as extinction overtook in
succession one tribe of existences after another, and species, like
individuals, yielded to the great law of death, yet other species
were brought to the birth, and ushered upon the scene, and the chain
of being was maintained unbroken. We see only detached bits of
that green web which has covered our earth ever since the dry land
first appeared. But the web itself seems to have been continuous
throughout all time; though, as breadth after breadth issued from
the creative loom, the pattern was altered, and the sculpturesque
and graceful forms that illustrated its first beginnings and its
middle spaces have yielded to flowers of richer colour and blow, and
fruits of fairer shade and outline; and for gigantic club-mosses
stretching forth their hirsute arms, goodly trees of the Lord have
expanded their great boughs; and for the barren fern and the calamite
clustering in thickets beside the waters, or spreading on flowerless
hill-slopes, luxuriant orchards have yielded their ruddy flush, and
rich harvests their golden gleam."
When we find animals and plants, of forms unknown at the present
day, in all stages of development, we read a lesson as to the
history of the earth's former state as conclusive as that which
is derived from the Nineveh relics (independent of Revelation) in
regard to the history of the human race. There is no want of harmony
between Scripture and Geology. The Word and the Works of God must
be in unison, and the more we truly study both, the more they will
be found to be in accordance. Any apparent want of correspondence
proceeds either from imperfect interpretation of Scripture or from
incomplete knowledge of science. The changes in the globe have all
preceded man's appearance on the scene. He is the characteristic
of the present epoch, and he knows by Revelation that the world is
to undergo a further transformation, when the elements shall melt
with fervent heat, and when all the present state of things shall be
dissolved, ere the ushering in of a new earth, wherein righteousness
is to dwell.
_RECAPITULATION._
Recapitulation of the chief points connected with Fossil Botany:--
1. The vegetation of the globe has varied at different epochs of
the earth's history.
2. The farther we recede in geological history from the present
day, the greater is the difference between the fossil plants and
those which now occupy the surface.
3. All fossil plants may be referred to the great classes of
plants of the present day, Acotyledons, Monocotyledons, and
Dicotyledons.
4. The fossil species are different from those of the present
flora, and it is only when we reach the Tertiary periods that we
meet with some genera which are without doubt identical.
5. Fossil plants are preserved in various conditions, according
to the nature of their structure, and the mode in which they have
been acted upon. Sometimes mere casts of the plants are found, at
other times they are carbonised and converted into coal, while
at other times, besides being carbonised, they are infiltrated
with calcareous or siliceous matter, and finally, they may be
petrified.
6. Cellular plants, and the cellular portions of vascular plants,
have rarely been preserved, while woody species, and especially
Ferns, which are very indestructible, have retained their forms
in many instances.
7. In some cases, especially when silicified or charred, the
structure of the woody stems can be easily seen in thin sections
under the microscope.
8. The determination of fossil plants is a matter of great
difficulty, and requires a thorough knowledge of structure, and
of the markings on stems, roots, etc.
9. The rocks containing organic remains are called fossiliferous,
and are divided into Primary, Secondary, and Tertiary, or into
Palæozoic, Mesozoic, and Cainozoic, each of these series being
characterised by a peculiar facies of vegetable life.
10. The mere absence of organic remains will not always be a
correct guide as to the state of the globe.
11. The number of fossil species has been estimated at between
3000 and 4000; but many parts of plants are described as separate
species, and even genera, and hence the number is perhaps greater
than it ought to be.
12. Brongniart divides the fossil flora into three great
epochs:--1. The reign of Acrogens; 2. The reign of Gymnosperms;
3. The reign of Angiosperms.
13. The reign of Acrogens embraces the Silurian, Carboniferous,
and Permian epochs, in which there was a predominance of plants
belonging to the natural orders Filices, Lycopodiaceæ, and
Equisetaceæ, associated, however, with others of a higher class.
14. The reign of Gymnosperms embraces the lower and middle
Secondary periods, and is characterised by the presence of
numerous Coniferæ and Cycadaceæ.
15. The reign of Angiosperms includes the Cretaceous and Tertiary
periods, and is marked by the predominance of Angiospermous
Dicotyledons.
16. Coal is a vague term, referring to all kinds of fuel formed
from the chemically-altered remains of plants.
17. When there is a great admixture of mineral matter, so that it
will not burn as fuel, then a shale is produced.
18. The microscopic structure of Coal probably varies according
to the nature of the plants of which it is composed, and the
changes produced by pressure, heat, and other causes. Cellular
tissue, punctated woody tissue, and scalariform vessels, have
been detected in it.
19. Certain temporary and local floras seem to have given origin
to peculiar layers of coal.
20. During the Carboniferous epoch we meet with Ferns,
Sigillarias, and their roots called Stigmarias, Lepidodendrons,
Ulodendrons, Calamites, Gymnosperms, etc.
21. The plants forming coal have grown in the basin where the
coal is found; but sandstone rocks in the coal-measures deposited
by water having a considerable velocity, and consequently
carrying power, contain sometimes trunks of large trees which
have been drifted like snags.
22. The strata between the Permian epoch and Chalk display
numerous Gymnosperms, especially belonging to the Cycadaceous
Order. Some of them exhibit limited coal deposits.
23. The Chalk and Tertiary strata display not only Acrogens and
Gymnosperms, but also Angiospermous Dicotyledons, some of which,
at the Miocene period, belong apparently to genera of the present
day.
24. Brown Coal occurs in the Upper Tertiary beds, and in it
vegetable structure is easily seen under the microscope.
25. Raulin thinks that during the Tertiary epoch the flora of
Europe has gradually assumed a more temperate character.
26. The Eocene flora, according to Unger, resembled in many
respects that of Australia at the present day.
27. The Miocene flora is characterised by a number of exotic
forms of warm regions with those of temperate climates. It is
largely seen in the Arctic Regions.
28. The Pliocene flora has great analogy with that of the
temperate regions of Europe, North America, and Japan.
_WORKS ON FOSSIL BOTANY._
On the subject of Fossil Botany the following works may be
consulted:--
Abhandlungen der Kaiserlich Königlichen Geologischen
Reichsanstalt, Band. ii. Wien. 1855.
Argyll, Duke of, on Tertiary Leaf-Beds in the Isle of Mull,
Journ. Geol. Soc. Lond., vii. May 1851.
Balfour, J. H., on certain Vegetable Organisms in Coal from
Fordel, Trans. R.S.E., vol. xxi. p. 187.
Baily, W. H., Figures of Characteristic British Fossils, 1871-2.
Bennett, J. Hughes, on the Structure of Torbane Hill Mineral and
other Coals, Trans. R. Soc. Ed., vol. xxi. p. 173.
Binney, E. W., on Calamites and Calamodendron, Palæontographical
Society's Memoirs, 1868.
---- on the Structure of Fossil Plants found in the Carboniferous
Strata. Palæontographical Society's Memoirs, 1871.
---- Description of some Fossil Plants, showing Structure in the
Lower Coal Seam of Lancaster and Yorkshire, Phil. Trans., vol.
155, p. 579.
Bowerbank, Fossil Fruits and Seeds of the London Clay.
Brongniart, Histoire des Végétaux Fossiles, 1828-44.
---- Observations sur la Structure intérieure du Sigillaria,
etc., in Archives du Museum, i. 405.
---- Exposition Chronologique des Périodes de Végétation, in Ann.
des Sc. Nat. 3d series, Bot. xi. 285.
Carruthers, on Gymnospermatous Fruits from the Secondary Rocks of
Britain, Journ. Bot., Jan. 1867.
---- on the Structure of the Stems of the Arborescent
Lycopodiaceæ of the Coal Measures, Nos. i. to iv., Month.
Microsc. Journ., vols. i. ii. iv.
---- on the Cryptogamic Forests of the Coal Period, Paper read
before the Royal Institution of Great Britain, 16th April 1869.
---- on the Structure and Affinities of Sigillaria and Allied
Genera, Quart. Journ. Geol. Soc., Aug. 1869.
---- on a Fossil Cone from the Coal Measures, Geol. Mag., 1865.
---- on Caulopteris punctata, _ibid._
---- on Araucaria Cones from the Secondary Beds of Britain,
_ibid._ 1866.
---- on an Aroideous Fruit from the Stonesfield Slate, _ibid._
1867.
---- on Cycadoidea Yatesii, _ibid._ 1867.
---- on the Structure of the Fruit of Calamites, Journal of
Botany, 1867.
---- on British Fossil Pandanaceæ, _ibid._ 1868.
---- on British Fossil Coniferæ, _ibid._ 1869.
---- on the Petrified Forest near Cairo, Geol. Mag., vii. 306.
---- on the Structure of a Fern-Stem from the Lower Eocene,
Journ. Geol. Soc., xxvi. 349.
---- on the Structure and Affinities of Lepidodendron and
Calamites, Trans. Bot. Soc. Edin., viii. 495.
---- on some Fossil Coniferous Fruits, Geol. Mag., vols. iii. vi.
---- on Beania, a new genus of Cycadean Fruit, from the Yorkshire
Oolites, Geol. Mag., vol. vi.
---- on Plant-remains from the Brazilian Coal-beds, with Remarks
on the genus Flemingites, Geol. Mag., vol. vi.
---- on the Fossil Cycadaceous Stems from the Secondary Rocks of
Britain, Linn. Trans., xxvi. 675.
---- on the History and Affinities of the British Coniferæ, Brit.
Assoc. Reports, 40th Meeting, p. 71.
Carruthers, List of New Genera and Species of Fossil Plants, Nos.
i. ii. and iii., Journal of Botany, vols. viii. ix. x.
Coalfields, by a Traveller under ground.
Corda, Beiträge zur Flora der Vorwelt, Prag. 1845.
Cotta, Dendrolithen, Leipzig, 1850.
Dawson, J. W., on Spore-Cases in Coal, Ann. Nat. Hist., 1871, p.
321.
---- on Vegetable Structures in Coal, Quart. Journ. Geol. Soc.,
1860.
---- on the Pre-Carboniferous Flora of New Brunswick and Eastern
Canada, Canadian Naturalist, May 1861.
---- on the Flora of the Devonian Period in North-Eastern
America, Quart. Journ. Geol. Soc., Nov. 1862.
---- on an Erect Sigillaria and a Carpolite from Nova Scotia,
Quart. Journ. Geol. Soc. Lond.
---- on Calamites, Ann. Nat. Hist. 4th ser. vol. iv. 272.
---- on the Varieties and Mode of Preservation of the Fossils
known as Sternbergiæ, Canadian Naturalist; also in Edin. New
Phil. Journal, N.S. vii. 140.
---- Acadian Geology, 1868.
---- the Fossil Plants of the Devonian and Upper Silurian
Formations of Canada, Geol. Survey of Canada, 1871.
---- on the Pre-Carboniferous Floras of North-Eastern America,
with special reference to that of the Erian (Devonian) Period,
Proc. Roy. Soc. Lond., May 5, 1870.
---- on the Graphite of the Laurentian Rocks of Canada, Quart.
Journ. Geol. Soc., xxvi. 112.
Dunker, Zettel, and Meyer, Beiträge zur Naturgeschichte der
Vorwelt.
Ettingshausen, Beiträge zur Flora der Vorwelt in Abhandlungen der
Geolog. Reichsanstalt, Vienna, 1851.
Forbes, on Tertiary Leaf-Beds in the Isle of Mull, discovered by
the Duke of Argyll, F.G.S., with a note on the Vegetable Remains
from Ardtun Head, Quart. Journ. Geol. Soc. Lond., vol. vii.
Giebel, Palæontologie.
Goeppert, Beiträge zur Bernsteinflora; sur la Structure de la
Houille.
---- Die Gattungen der Fossilen Pflanzen, Bonn, 1841.
---- Monographie des Fossilen Coniferen, 1850.
---- Systema Filicum Fossilium, Nova Acta, xvii.
---- Ueber die Fossilen Cycadeen, Breslau, 1844.
---- Erläuterung der Steinkohlen-Formation.
Goeppert, Die Fossile Flora der Permischen Formation,
Palæontographica, Hermann von Meyer, Cassel, 1864.
---- Beiträge zur Kenntniss Fossilen Cycadeen, Breslau.
Grand d'Eury, on Calamites and Asterophyllites, Ann. Nat. Hist.,
ser. 4, vol. iv. 124.
Harkness, on Coal, Edin. Phil. Journ., July 1854.
Heer, Flora Tertiaria Helvetiæ, 3 vols.
---- Flora Fossilis Arctica, 1868-1871.
---- on the Fossil Flora of Bovey Tracey, Phil. Trans. R.S.L.,
152, p. 1039.
---- on the Fossil Flora of North Greenland, Phil. Trans., vol.
159, p. 445.
Hooker, on Some Minute Seed-Vessels (Carpolithes ovulum,
Brongniart) from the Eocene beds of Lewisham, Proceed. Geol.
Soc., 1855.
---- Vegetation of the Carboniferous Period, in Mem. of Geol.
Survey, ii.
---- on a New Species of Volkmannia, Quart. Journ. Geol. Soc.
Lond., May 1854.
King, on Sigillaria, etc., in Edin. New Phil. Journal, xxxvi.
Lesquereux, on the Coal Measures of America, Silliman's Journal,
1863.
Lindley and Hutton, Fossil Flora, 3 vols. A revision of the
original work, with a supplementary volume containing the recent
additions, and a Synopsis of the Fossil Plants of Britain by Mr.
W. Carruthers, is announced as about to be published.
Lowry, Table of the Characteristic Fossils of Different
Formations.
M'Nab, on the Structure of a Lignite (_Palæopitys_) from the Old
Red Sandstone, Trans. Bot. Soc. Edin., x. 312.
Mueller and Smyth, on Some Vegetable Fossils from Victoria, Geol.
Mag., vii. 390.
Meyer, Hermann Von, Palæontographica. Beiträge zur
Naturgeschichte der Vorwelt, 1864.
Nicholson, on the Occurrence of Plants in the Skiddaw Slates,
Geol. Mag., vol. vi.
Paterson, Description of Pothocites Grantoni, a New Fossil
Vegetable from the Coal Formation, Trans. Bot. Soc. Edin., vol. i.
Penny Cyclopædia, vol. vii., Coal Plants.
Pictet, Traité de Paléontologie.
Quekett, on the Minute Structure of Torbane Hill Mineral, Journ.
Microsc. Sc., 1854.
Raulin, Flore de l'Europe pendant la Période Tertiaire, in Ann.
des Sc. Nat., 3d ser. x. 193.
Redfern, on the Nature of the Torbane Hill and other Varieties of
Coal, Brit. Assoc. Liverpool, 1854.
Roehl, A. von, Fossile Flore der Steinkohlen Formation
Westphalens.
Saporta, Etudes sur la Végétation du Sud-Est de la France à
l'Epoque Tertiaire, Annales des Sciences Naturelles, ser. 4, tome
xvi. 309, xvii. 191, xix. 5; ser. 5, tome iii. 5, iv. 5.
Schenk, Professor, die Fossile Flore der Nordwest Deutschen
Wealden Formation.
Schimper, Traité de Paléontologie Végétale, 1870-71.
Tate, on the Fossil Flora of the Mountain Limestone Formation of
the Eastern Borders, in connection with the Natural History of
Coal (in Johnstone's Eastern Borders).
Torbane Coal, as noticed in the Report of the Trial as to the
substance called Torbane Mineral or Torbanite.
Unger, Genera et Species Plantarum Fossilium.
---- Chloris Protogæa.
---- Le Monde Primitive (a work which contains picturesque views
of the supposed state of the earth at different geological
epochs).
---- on the Flora of the Eocene Epoch, Journ. Bot., iii. 39.
Weber and Wersel, Die Tertiarflore der Nieder Sheinescher
Braunkohlen Formation.
Williamson, W. C., on the Organisation of the Fossil Plants of
the Coal Measures, Ann. Nat. Hist., 1871, p. 134.
---- on the Structure and Affinities of the Plants hitherto known
as Sternbergiæ, Mem. Manch. Lit. and Phil. Soc., ix.
---- on a New Form of Calamitean Strobilus, from the Lancashire
Coal Measures, Mem. Lit. Phil. Soc. Manchester, vol. iv. 3d
series.
---- on the Structure of the Woody Zone of an Undescribed Form of
Calamite, Mem. Lit. Phil. Soc. Manchester, vols. iv. and viii. 3d
series.
---- on Volkmannia Dawsoni, _ibid._ 1870-71.
---- on Zamia gigas (Williamsonia gigas), Linn. Trans., xxvi. 663.
---- on the Organisation of Fossil Plants of the Coal Measures,
Part I., Calamites, Phil. Trans. R.S.L., vol. 161, p. 477.
Witham, on the Structure of Fossil Vegetables.
Yates, on Zamia gigas, Proceed. Yorkshire Phil. Soc., April 1847.
Young, J., and Armstrong, Jas., on the Carboniferous Fossils of
the West of Scotland, Trans. Geol. Soc. Glas., vol. iii.
Besides geological treatises such as those of Ansted,
Beudant, Jukes, Lyell, and others.
EXPLANATION OF PLATES.
PLATE I.
Fig. 1. Palæopteris Hibernica, Schimper (Cyclopteris Hibernica,
Forbes). One-sixth the natural size.
Fig. 2. A pinnule somewhat magnified, showing the venation.
Fig. 3. A fertile pinna, natural size.
Fig. 4. Two cup-shaped indusia borne on the rachis.
Fig. 5. Sporangia enclosing spores. From the Coal-measures.
Fig. 6. Sporangia of Hymenophyllum Tunbridgense, Sm. (Fern of
present epoch.)
Fig. 7. Sporangium of Polypodium vulgare, Linn. (Fern of present
epoch.) Figs. 5, 6, and 7, magnified to the same extent.
Fig. 8. Transverse section of Osmundites Dowkeri, Carruthers.
Fig. 9. Two cells of Osmundites, filled, the one with starch
granules, and the other with mycelium of a fungus.
PLATE II.
Fig. 1. Cycadeostrobus ovatus, Carr. From the Wealden, Isle of
Wight.
Fig. 2. Beania gracilis, Carr. From the Yorkshire Oolite.
Fig. 3. Bennettites Saxbyanus, Carr. From the Lower Greensand of
the Isle of Wight.
Fig. 4. Pinites Leckenbyi, Carr. From the Lower Greensand of the
Isle of Wight.
Fig. 5. Trigonocarpon olivæforme, Lindl. and Hutt. From the
Coal-measures, Manchester.
Fig. 6. Trigonocarpon sulcatum, Carr. Coal-measures, Wardie,
Edinburgh.
Fig. 7. Sequoiites Gardneri, Carr. From the Gault at Folkestone.
Figs. 8, 9. Cupressinites Thujoides, Bowerbank. From the Eocene
at Sheppey.
Fig. 10. Scale of Araucarites Brodiei, Carr. From the Great
Oolite at Stonesfield.
Fig. 11. Scale of Araucarites Phillipsii, Carr. From the Oolite
of Yorkshire.
All the figures on this Plate (except Fig. 2, which is one-half
of the natural size) are drawn the size of nature.
PLATE III.
Fig. 1. Mass of coal from Fordel, Fifeshire, containing numerous
sporangia of Flemingites. These sporangia occur in coal from
different localities in England and Scotland. Binney has seen
them in Wigan coal. Huxley has found them abounding in coal near
Bradford (Balfour, R.S.E. Trans.)
Fig. 2. One of the Sporangia entire, and separated from the coal
(Balfour).
Fig. 3. Sporangium with its valves separated, containing a
quantity of black carbonaceous matter in its interior (Balfour).
This matter is formed by the altered spores (microspores).
Fig. 4. Sporangium, showing the triradiate marking on the under
surface, and a granulation produced probably by the spores in the
interior.
Fig. 5. Punctated woody tissue (Coniferous). From the needle coal
of Toplitz, Bohemia (Harkness).
Fig. 6. Scalariform vessels from coal (Balfour).
Fig. 7. Stigmaria, with markings of rootlets. One showing the
papilla to which the rootlet was articulated (Hooker).
Fig. 8. Transverse section of Stigmaria, showing the vascular
cylinder divided into wedges (Hooker).
Fig. 9. Tissues of Stigmaria, showing the inner portion of the
vascular cylinder (Hooker).
Fig. 10. Transverse section of a Lepidostrobus, the
fructification of Lepidodendron, showing scales and sporangia
(Hooker).
Fig. 11. Ulodendron Taylori (Carruthers).
PLATE IV.
Fig. 1. Sigillaria Brownii, restored (Dawson).
Fig. 2. Sigillaria elegans, restored (Dawson).
Fig. 3. Lepidodendron, restored (Carruthers, Bot. Soc. Trans.)
Fig. 4. Calamites, restored (Carruthers, Bot. Soc. Trans.)
Fig. 5. Psilophyton, a fossil of the Devonian epoch (Dawson).
[Illustration: Pl. I.
A. T. Hollick del. et lith. Mintern Bros. imp.
Fossil Ferns.]
[Illustration: Pl. II.
A. T. Hollick del. et lith. Mintern Bros. imp.
Fossil Gymnospermous Fruits.]
[Illustration: Pl. III.
M^cFarlane & Erskine, Lith^{rs} Edin^r
Coal and Coal-Plants.]
[Illustration: Pl. IV.
M^cFarlane & Erskine, Lith^{rs} Edin^r
Devonian and Carboniferous Flora.]
INDEX.
Abietites, 84, 85, 87.
Acacia, 90, 92.
Acanthocarpum, 72.
Acer, 92, 97.
Acerites, 87.
Acrogens of present day, 26.
Acrogens, fossil, reign of, 25, 26.
Adiantites, 41.
Æthophyllum, 79.
Alder, 94.
Alethopteris, 43, 72.
Algæ, 35.
Algæ of Cretaceous epoch, 87.
Alnites, 87, 94.
Alnus, 94, 97.
Alsophila, 29.
Amber, 90.
Amber flora, Goeppert on the, 91.
Amentiferæ, fossil, 92.
Ancestrophyllum, 48.
Andromeda, 96, 97.
Angiosperms, fossil, reign of, 25, 87.
Annularia, 61, 71.
Anomopteris, 79.
Anona, 97.
Anthodiopsis, 72.
Antholithes, 64.
Anthracite, 36.
Apocynaceæ, fossil, 92.
Araucaria, 5, 6, 7, 85, 90.
Araucarioxylon, structure of, 63.
Araucarites, 82, 83, 84, 85, 86, 87.
Arctic fossil flora (Miocene), 97.
Arctic Regions, Palæozoic flora of, 40.
Arctic Regions, fossil wood of, 95.
Arthropitys, 72.
Artisia, 64.
Asplenium, 28.
Asterophyllites, 35, 61, 71.
Bambusium, 92.
Bauhinia, 90, 92.
Beania, 82.
Bear Island, fossil flora of, 40, 59.
Beeches, 97.
Bennettiteæ, 86.
Bennettites, 85, 87.
Betula, 94, 97.
Bothrodendron, 57.
Bovey Tracey flora, 96.
Bovey Tracey, Devonshire, lignite beds of, 96.
Brachyphyllum, 80, 86, 87.
Bryson's instrument for slitting, 14.
Bucklandia, 84, 86.
Cæsalpinia, 90.
Cainozoic period, fossil plants of, 87.
Calamites, 35, 41, 53.
Calamites, foliage and fruit (woodcut), 62.
Calamites, structure of, 57.
Calamites, structure of fruit, 60.
Calamodendron, 59, 72.
Callipteris, 72.
Callitris, 90.
Camptopteris, 79, 80.
Carboniferous epoch, 36.
Carboniferous vegetation, its general character, 69.
Carbonisation, 9.
Cardiocarpum, 41, 72, 78.
Cardiocarpum, structure of, 64.
Cardiopteris, 40.
Carpinites, 87.
Carpinus, 94.
Carpolithes, 78, 83, 92, 97.
Cassia, 90.
Casts of plants, 8.
Casuarina, 90.
Caulinites, 90.
Caulopteris, 43.
Centrolobium, 90.
Chalk flora, characteristics of, 87.
Chara, 92.
Characeæ, fossil, 91.
Chondrites, 87.
Cinchonaceæ, fossil, 92.
Cinnamomum, 96.
Classes to which fossil plants belong, 2.
Climate as determined by fossil plants, 19.
Climate of the Tertiary period, 100.
Club-mosses, 26, 30.
Coal-basins, 37.
Coal, brown, structure of, 100.
Coal, Fordel, 36, 56.
Coal-formation, extent of, 38.
Coal, household, 36.
Coal-measures, flora of, 39.
Coal, parrot, 36.
Coal-plants, _in situ_, or drifted, 67.
Coal, structure in, 36.
Coal, Wigan cannel, 36.
Coal of Oolitic epoch, 82.
Coal of Tertiary beds, 100.
Combretaceæ, fossil, 92.
Comptonia, 92, 94.
Comptonites, 87.
Cones, fossil, of Wealden, 85.
Confervites, 87.
Coniferæ, 87.
Coniferæ, modern, 72.
Coniferæ, number of Miocene species, 97.
Coniferæ, Oolitic, 80.
Coniferæ, structure of recent, 74.
Coniferæ of brown coal deposits, 100.
Coniferæ of Miocene Arctic fossil flora, 97.
Coniferæ of Secondary strata, 85.
Coniferæ of Tertiary period, 89.
Coniferous genera of Lias, 79.
Coniferous vegetation of Upper Cretaceous period, appearance of, 89.
Copaifera, 90.
Cordaites, 35, 72.
Cornus, 97.
Corylus, 96, 97.
Cratægus, 97.
Credneria, 87.
Crematopteris, 79.
Cretaceous system, fossil plants of, 87.
Crossozamia, 86.
Cryptogamia, number of Miocene species of, 97.
Cryptomeria, 87.
Cryptomerites, 86.
Ctenis, 78, 79.
Cucumites, 90.
Cunninghamites, 87.
Cupressineæ, 89.
Cupressoxylon, 93.
Cyathea, 29.
Cyatheites, 72.
Cycadaceæ, 87.
Cycadaceæ, fossil, Carruthers' arrangement of, 86.
Cycadaceæ, modern, 72, 75.
Cycadaceæ, Oolitic, 80.
Cycadaceæ in Mesozoic period, 77.
Cycadaceæ of Lias, 79.
Cycadaceæ of Tertiary period, 89.
Cycadaceæ of Wealden epoch, 84.
Cycadeostrobus, 85.
Cycadites, 44, 79, 84, 87.
Cycadoidea, 83.
Cycas, 76.
Cyclopteris, 32, 35, 43, 72.
Cyclostigma, 41.
Cyperites, 48.
Cystoseirites, 87.
Dadoxylon, 35, 63.
Dalbergia, 90.
Dammarites, 87.
Daphnogene, 92, 96, 97.
Dawson on Devonian fossils, 35.
Desmodophyllum, 92.
Dicotyledons of Pliocene epoch, 98.
Dictyothalamus, 72.
Didymophyllum, 48.
Didymosorus, 95.
Dioonopteris, 72.
Dirt-bed, Portland, 83.
Dolichites, 92.
Drepanocarpus, 90.
Dryandroides, 96.
Echitonium, 92, 96.
Encephalartos, 76.
Entada, 90.
Eocene epoch, Algæ of, 90.
Eocene epoch, characteristics of, 90.
Eocene epoch, Coniferæ of, 90, 91.
Eocene epoch, flora of, 89, 90.
Eocene epoch, fruits of, 90.
Eozoon Canadense, 31.
Equisetaceæ, 29, 59.
Equisetites, 71.
Equisetum, 31, 53, 79, 94, 95.
Equisetum spores, 32.
Equisetum, structure of fruit, 60.
Erian fossil plants, 35.
Erythrina, 92.
Exogenous trees of Carboniferous epoch, 62.
Fagus, 94, 97.
Favularia, 46.
Fern-flora in connection with climate, 41.
Ferns, 96.
Ferns, structure of, 29.
Ferns of Carboniferous strata, 41.
Ferns of present day, 26.
Ficus, 96.
Fig, evergreen, 96.
Filicites, 94.
Fittonia, 86, 87.
Flabellaria, 64, 87.
Flemingites, 51, 52, 57.
Floras of present day in connection with fossil plants, 19.
Folliculites, 92.
Fossil botany, recapitulation of chief points connected with, 103.
Fossil botany, list of works treating of, 105.
Fossil plants compared with modern plants, 3, 4.
Fossil plants, determination of, 3.
Fossil plants, mode of preservation of, 8.
Fossil plants, number of, 23.
Fossiliferous periods, according to Brongniart, 25.
Fossiliferous rocks, 20.
Fructification in ferns of Carboniferous epoch, 40.
Fruits, fossil, of Isle of Sheppey, 90.
Fungi, fossil, 91.
Gardenia, 97.
Gault, Coniferæ of, 80, 85.
Getonia, 92.
Glyptostrobus, 97.
Grès bigarré, 78.
Gymnosperms, fossil, reign of, 25.
Gyrogonites, 92.
Haidingera, 78.
Hakea, 97.
Halonia, 57.
Heer's list of plants from the Bovey Tracey Miocene formation, 96.
Heer on the migration of plants, 98.
Heer on the number of species in the Arctic fossil flora, 97.
Heer's remarks on the Polar flora, 98.
Hightea, 90.
Horse-tails, 29.
Huttonia, 71.
Hymenophylleæ, 34.
Hymenophyllites, 71.
Hymenophyllum, 35.
Ilex, 97.
Infiltration, 9.
Inga, 90.
Isoetes, 27, 49, 89.
Ivy, 97.
Juglandites, 87.
Jurassic period of Brongniart, 79.
Kaidacarpum, 84.
Keupric period, 79.
Kimmeridge Clay, Coniferæ of, 85.
Knorria, 41, 48, 57.
Knorria, phyllotaxis of, 55.
Lastrea, 29.
Lauraceæ, 97.
Lauraceæ, fossil, 92.
Laurel, 96.
Laurentian rocks, 31.
Laurus, 92, 96.
Leaf-beds of Ardtun, Mull, 93.
Leaf-beds of Bournemouth, 95.
Leaf-beds, genera of, 94.
Leguminosæ, fossil, 92.
Leguminosites, 90.
Lepidodendron, 35, 41, 49.
Lepidodendron, phyllotaxis of, 54.
Lepidophloios, 57.
Lepidophyllum, 41, 56.
Lepidostrobus, 35, 50, 52.
Lias, Coniferæ of, 80.
Lias, fossil plants of, 79.
Libocedrus, 90.
Lignite, 32.
Lignite beds of Bovey Tracey, 96.
Lignites, 9.
Lonchopteris, 43, 84.
Lough Neagh, Miocene formation of, 93.
Lower Greensand, cone of, 89.
Lower Greensand, Coniferæ of, 85.
Lycopodiaceæ, 49, 54.
Lycopodiaceæ, modern, 26.
Lycopodites, 56.
Lycopodium, 30, 53.
MacClintockia, 97.
Macrospores, 30.
Magnolia, 97.
Mantellia, 83, 84, 86.
Marsilea, 31, 33.
Marsileaceæ, 31.
Mesozoic period, flora of the, 72.
Microspores, 30.
Microzamia, 87.
Mimosa, 90.
Mimosites, 92.
Miocene epoch, flora of, 89, 92.
Miocene period, temperature of, 97.
Mull, leaf-beds of, 93.
Mull, Miocene formation of, 93.
Munsteria, 87.
Myrica, 94, 97.
Naiadaceæ, 87.
Natural orders to which fossil plants belong, 22.
Neuropterideæ, 41.
Neuropteris, 42, 71.
Nicolia, 11.
Nicol's mode of preparing sections, 13.
Nilssonia, 79.
Nipadites, 90.
Noeggerathia, 64, 71, 72.
Nymphæa, 97.
Odontopteris, 42, 72.
Oolitic epoch, flora of, 80.
Oolite, fruits of, 83.
Oolite, Inferior, Coniferæ of, 86.
Oolite, Lower, 82.
Oolite, Scottish, plants of, 81.
Oolite, Upper, 82.
Oolite, Yorkshire, 83.
Osmunda, 89.
Osmundites, 91.
Otopteryx, 97.
Otozamites, 79.
Oxford Clay, Coniferæ of, 86.
Palæophytology, 1.
Palæopitys, 32.
Palæopteris, 32, 34, 41.
Palæozamia, 79.
Palæozoic or Primary period, 26.
Palæozoology, 1.
Palissya, 80, 86.
Paliurus, 97.
Palm, 96.
Palmacites, 87, 90, 96.
Pandanaceæ, 84.
Pecopteris, 42, 96.
Pecopterideæ, 41.
Pepperworts, 31.
Permian flora, 71.
Permian period, fruits of, 72.
Petrifaction, 9.
Petrified forests, 11.
Pence, 64, 80, 82, 86, 89.
Phanerogamia, number of Miocene species of, 97.
Phaseolites, 92.
Phœnicites, 92.
Phyllotaxis, 54, 55.
Pilularia, 31.
Pinites, 78, 85, 86, 87, 89, 100.
Pinites, structure of, 63.
Pinus, 86, 94, 97.
Pissadendron, 63.
Pitus, structure of, 64.
Plane, 94.
Platanites, 94.
Platanus, 97.
Pliocene epoch, flora of the, 89, 98.
Plumiera, 92.
Podocarpus, 90.
Podocarya, 84.
Portland beds, 82.
Portland Crag, 82.
Portland stone, Coniferæ of, 85.
Pothocites, 66.
Proteaceæ, fossil, 92, 97.
Protopteris, 87.
Prototaxites, 35.
Prunus, 97.
Psaronius, 44, 71.
Psilophyton, 35.
Pterocarpus, 90.
Pterophyllum, 84, 79.
Purbeck, Coniferæ of, 85.
Purbeck period, 83.
Quercus, 94, 96, 97.
Raulin on the Tertiary flora of Central Europe, 99.
Raumeria, 86.
Recapitulation of chief points connected with fossil botany, 103.
Rhabdocarpum, 72, 77.
Rhamnites, 94, 95.
Rhamnus, 94, 97.
Rhizocarpeæ, 31.
Rings, number of annual, in fossil Exogens, 100.
Sagenopteris, 71, 79.
Salicites, 87.
Salix, 97.
Sargassites, 87.
Scalariform vessels, 30.
Schizopteris, 43.
Secondary period, flora of the, 72.
Sections of fossils for microscope, 12.
Selaginella, 27, 51, 53.
Selaginites, 35.
Senftenbergia, 40.
Sequoia, 87, 96, 97.
Sequoiites, 85, 89.
Shale, 37.
Sheppey, fruits of Isle of, 90.
Sigillaria, 45.
Silicified stems, 10.
Sphenophyllum, 35, 61.
Sphenopterideæ, 41.
Sphenopteris, 34, 41, 42.
Sporangia, 30, 56.
Stangeria, 78.
Steinhauera, 92.
Sternbergia, 64, 97.
Stigmaria, 41, 47, 48.
Stonesfield slate, 82.
Stratified rocks, 21.
Structure of fossil plants, 12.
Table of formations, 21.
Taxites, 86, 94, 95, 100.
Taxodieæ, 89.
Taxodites, 79, 80, 94, 95.
Taxodium, 97.
Terminalia, 92.
Tertiary flora of Europe, 99.
Tertiary period, characteristics of, 89, 100.
Tertiary period, fossil plants of, 87.
Tertiary vegetation, Brongniart's divisions of, 89.
Thaumatopteris, 80.
Thuites, 81, 85, 86.
Thujopsis, 97.
Tilia, 97.
Trap rocks, 20.
Tree-fern, 27.
Trees of Miocene Arctic fossil flora, 97.
Triassic fossils, 77.
Trigonocarpum, 64, 72.
Triplosporites, 50, 53.
Tuff-beds, 94.
Tulip tree, 97.
Ulmus, 92.
Ulodendron, 57.
Underclay, 37.
Unger's list of genera of Eocene epoch, 90.
Upper Chalk, 85.
Upper Greensand, Coniferæ of, 85.
Vaccinium, 96.
Vitis, 96.
Volkmannia, 60.
Voltzia, 78, 79.
Vosgesian period, Brongniart's, 78.
Walchia, 71.
Walnuts, 97.
Wealden, Coniferæ of, 85.
Wealden epoch, flora of, 84.
Widdringtonites, 87.
Williamsonia, 81.
Williamsonieæ, 86.
Willow, 97.
Works, list of, treating of fossil botany, 105.
Yatesia, 86.
Yew, 94.
Zamia, 78.
Zamieæ, 86.
Zamiostrobus, 78.
Zamites, 78, 79, 84, 87.
Zostera, 32.
Zosterites, 87.
THE END.
_Printed by_ R. & R. CLARK, _Edinburgh_.
FOOTNOTES:
[1] Miller's Footprints of the Creator, 192-199. Doubts have been
thrown on the antiquity of this specimen by those who support the
erroneous progressive development theory; but the presence, in the
same nodule, of a scale of a fish only found in the lower Old Red,
puts the matter beyond doubt. Dr. M'Nab on the Structure of a Lignite
(_Palæopitys_) from the Old Red Sandstone. (Trans. Bot. Soc. x. p.
312.)
[2] Specimens of these fossil plants, as well as numerous others,
illustrating the fossil flora of Scotland, are to be seen in Mr.
Miller's collection, now in the Edinburgh Museum of Science and Art.
[3] Dawson, Jour. Geol. Soc. Lond. xv. Canadian Naturalist, v.
Acadian Geology, 2d edit. Fossil plants of the Devonian and upper
Silurian Formations of Canada, with 20 plates; in Report of
Geological Survey of Canada.
[4] Maclaren, Geology of Fife and the Lothians, p. 116.
[5] Our Coal-fields, by a Traveller under Ground.
[6] See Hall's Coal-fields of Great Britain, 1861; Roscoe's Lectures
on Coal, Manchester, 1866-67; Hunt's Mineral Statistics of Great
Britain; Taylor's Statistics of Coal, 1855-56.
[7] Heer, Flora fossilis Arctica; Fossile Flora der Bären Insel.,
1871.
[8] In giving names to fossil Ferns, the Greek word πτερίς, meaning
a Fern, is often used with a prefix indicating some character in the
form of the leaves, or stem, or fructification: such as, πέκος, a
comb; νεῦρον, a nerve; ὀδούς, a tooth; σφήν, a wedge; καυλός, a stalk
or stem; κύκλος, a circle; σχίζω, a split, etc.
[9] The imbedding of plants in an erect state in strata is similar to
what was noticed at the present day by Gardner in Brazil, where stems
of recent Coco-nut Palms were seen covered with sand to the depth of
50 feet.
[10] For woodcuts 44, 47, and 48, I am indebted to Dr. H. Bence
Jones, who has kindly placed them at my disposal. They were used to
illustrate Mr. Carruthers' remarks on the Cryptogamic forests of the
Coal period, published in the Journal of the Royal Institution of
Great Britain, April 16, 1869. Mr. Carruthers' observations are given
in the text.
[11] Conjugate spirals result from _whorls_ of usually 2, 3, 5, 8,
etc., leaves arranged so as to give 2, 5, 8, etc., parallel spirals,
each with an angular divergence equal to ½, ⅓, ⅕, ⅛, etc., of one
of the fractions expressing the divergence in an arrangement of
_alternate_ leaves.
[12] By inadvertence, the diameter is stated in my Class-book as 4-5
inches.
[13] See Remarks on the Structure of Calamites by W. C. Williamson,
Philos. Trans., 161, p. 477.
[14] Williamson on the Structure and Affinities of Sternbergiæ, in
Manch. Lit. and Phil. Soc. Mem. ix. Dawson on Sternbergia, in Edin.
New Phil. Journ., new series, vii. 140.
[15] See Notice of _Antholithes Pitcairniæ_, by C. W. Peach, in Bot.
Soc. Trans. Edin. vol. xi.
[16] See Professor Duns on the association of Cardiocarpum with
Sphenopteris. Proc. R.S.E., April 1, 1872.
[17] See Meyer's Palæontographica, Cassel, 1864.
[18] See fuller description of Coniferæ and Cycadaceæ in Balfour's
Class Book of Botany, pp. 906-912.
[19] Coal in the Kimmeridge clay is probably of animal origin.
[20] Carruthers, Geol. Mag., vol. viii. December 1871.
[21] Annals and Mag. of Nat. Hist. 2d ser. ii. 380.
[22] Journ. Geol. Soc. of London, vii.
[23] Philosophical Transactions, R. Soc. Lond., vol. clii. p. 1039.
[24] Heer, Flore Fossile des Regions Polaires, Zurich; also
Bibliotheque Univ. xxxix. p. 12; see also Ann. Nat. Hist. 4th ser. i.
61, iv. 81.
[25] Raulin, Sur les Transformations de la Flore de l'Europe centrale
pendant la période Tertiaire.--Ann. des Sc. Nat. 3d ser. Bot. x. 193.
* * * * *
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TRANSCRIBER'S NOTE
Italic text is denoted by _underscores_.
Superscripts are denoted by ^ eg Lith^{rs} Edin^r.
Basic fractions are displayed as ½ ⅓ ¼ etc; other fractions are shown
in the form a/b, eg 3/11 or 13/(34×2).
Most entries in the Table of Contents had a corresponding section
heading in the text. Twelve entries had a corresponding page-header,
on odd-numbered pages, but no section heading in the text itself.
All the page-headers have of course been removed in the etext. To
improve readability these twelve section headings have been created
and inserted in the etext; they have been italicized to indicate they
have been added by the transcriber.
The caption for an illustration is displayed as a sidenote in the
etext. It was shown as a page footnote in the original text.
Obvious typographical errors and punctuation errors have been
corrected after careful comparison with other occurrences within the
text and consultation of external sources.
Except for those changes noted below, misspelling in the text, and
inconsistent or archaic usage, have been retained. For example,
planished; punctated; coal-field, coalfield; criddles.
Pg 11, 'silicicified' replaced by 'silicified'.
Pg 39, '1-20th' replaced by '1/20th' for consistency.
Pg 42 Footnote [8], 'I split' replaced by 'a split'.
Pg 73 Illustration, 'Fg. 61' replaced by 'Fig. 61'.
Pg 79, 'aborescent' replaced by 'arborescent'.
Pg 102, 'to difficult' replaced by 'too difficult'.
Pg 105, '29. The Pliocene' replaced by '28. The Pliocene'.
Pg 111, 'Erom the Gault' replaced by 'From the Gault'.
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