Botany - The Science of Plant Life

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Title: Botany - The Science of Plant Life
Author: Taylor, Norman
Language: English
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[Illustration: Courtesy Journal of the International Garden Club]

[Illustration: _The prickly pear (Opuntia chlorotica santarita) of the
desert in the American Southwest._

(_This painting was kindly loaned by Dr. David Griffiths of the United
States Department of Agriculture and reprinted here through the courtesy
of the Journal of the International Garden Club, where it first
appeared._)]

POPULAR SCIENCE LIBRARY

EDITOR-IN-CHIEF

GARRETT P. SERVISS

AUTHORS

WILLIAM J. MILLER HIPPOLYTE GRUENER A. RUSSELL BOND
D. W. HERING LOOMIS HAVEMEYER ERNEST G. MARTIN
ARTHUR SELWYN-BROWN ROBERT CHENAULT GIVLER
ERNEST INGERSOLL WILFRED MASON BARTON
WILLIAM B. SCOTT ERNEST J. STREUBEL
NORMAN TAYLOR DAVID TODD
CHARLES FITZHUGH TALMAN
ROBIN BEACH

ARRANGED IN SIXTEEN VOLUMES
WITH A HISTORY OF SCIENCE, GLOSSARIES
AND A GENERAL INDEX

_ILLUSTRATED_

[Illustration]

VOLUME THIRTEEN

P. F. COLLIER & SON COMPANY
NEW YORK

MANUFACTURED IN U. S. A.

BOTANY

THE SCIENCE OF PLANT LIFE

NORMAN TAYLOR

CURATOR, BROOKLYN BOTANIC GARDEN

[Illustration]

P. F. COLLIER & SON COMPANY
NEW YORK

PREFACE

This book is for those who want some general knowledge of the plant
world, without necessarily caring for the technical details upon which
such knowledge is based. If it leaves the reader with an impulse to
follow the subject further than has been possible here, it will have
more than fulfilled its mission.

Throughout the book, it has often been convenient to refer to plants or
their behavior in terms implying reasoning faculties. Of course, plants
are never reasoning things, reasonable as many of their actions appear
to be, and to ascribe such qualities to them is to saddle them with
attributes perfectly foreign to the plant world. But the description of
them in the terms of our everyday speech, the translation of plant
behavior into the current conceptions of mankind, does so fix these in
our minds that they cease to be among those interesting things that
nearly everyone forgets. I have followed this method deliberately,
understanding perfectly the objections to it, but believing, with the
late C. E. Bessey, that in popular books “it is an admirable way of
looking at some botanical things.”

All of the half-tone illustrations, except two, are from the
photographic collections of the Brooklyn Botanic Garden, and I am under
the greatest obligation to the director of that institution for
permission to publish them here. The illustration of the living and
fossil algæ has been taken from Prof. Henry Fairfield Osborn’s “Origin
and Evolution of Life,” with his kind permission. The illustration of
desert vegetation is from a photograph by the late E. L. Morris, and
kindly loaned from the collection of the Brooklyn Museum. All the line
cuts in the text are from drawings made specially for this book by my
wife, Bertha Fanning Taylor.

While grateful and particular acknowledgments can be made for the
illustrations, it is difficult or impossible to properly express my
indebtedness to all those who, through their books and pamphlets, have
indirectly aided in the making of this book. It would involve the
mention of most of the better known writers of the books found in the
larger botanical libraries. It is a pleasure to acknowledge help from
Dr. M. A. Howe of the New York Botanical Garden on the literature of
fossil and hot-spring algæ, and from Dr. Orland E. White of the Brooklyn
Botanic Garden for helpful criticism of the section dealing with “How
Plants Change Their Characters.”

NORMAN TAYLOR.

BROOKLYN BOTANIC GARDEN
20th October, 1920

CONTENTS

CHAPTER PAGE

INTRODUCTORY--PLANTS AND OUR DAILY NEEDS 9

I. WHAT PLANTS ARE 13

II. PLANT BEHAVIOR 76

III. HOW PLANTS PRODUCE THEIR YOUNG 116

IV. THE FAMILIES OF FLOWERING PLANTS AND THEIR RELATIONSHIP 168

V. USES OF PLANTS TO MAN 208

VI. GARDEN PLANTS 267

VII. HISTORY OF THE PLANT KINGDOM 298

VIII. DISTRIBUTION OF PLANTS 337

LIST OF ILLUSTRATIONS

THE PRICKLY PEAR OF THE DESERT IN THE AMERICAN SOUTHWEST _Frontispiece_

FACING PAGE
BANYAN--A FIG TREE OF INDIA 32

LACELEAF--A SUBMERGED AQUATIC PLANT 33

ROOT HAIRS WITH FINE SOIL PARTICLES ATTACHED 33

AERIAL ROOTS OF FIG TREES 64

VENUS’S FLYTRAP--AN INSECTIVOROUS PLANT 65

INDIAN PIPE--A SAPHROPHYTIC PLANT 96

PARTRIDGE BERRY--A TRAILING VINE 96

RAFFLESIA, THE LARGEST FLOWER IN THE WORLD 97

TALIPOT PALM OF CEYLON 128

TRAVELERS’ TREE, A PLANT OF THE BANANA FAMILY 129

WIND-BLOWN POLLEN OF THE JAPANESE RED PINE 160

COCONUT GROVE IN THE PHILIPPINE ISLANDS 161

TRANSPLANTING RICE IN JAVA 192

TEA ESTATE IN CEYLON 193

BANANA PLANTATION IN FRUIT 224

RICE TERRACES IN CHINA 225

FOREST OF THE TEMPERATE ZONE 256

LUXURIANT VEGETATION OF A TROPICAL RAIN FOREST 257

FOSSIL AND LIVING ALGÆ COMPARED 320

LANDSCAPE OF THE CARBONIFEROUS AGE 321

DESERT PLANTS OF THE SOUTHWEST UNITED STATES 352

CONTEST BETWEEN GRASS LAND AND TREE VEGETATION 353

INTRODUCTORY CHAPTER

PLANTS AND OUR DAILY NEEDS

Perhaps few of us realize that without plants all our modern
civilization would be swept away and that upon plants has been built all
that we have so far accomplished and everything that we may yet become.
The overthrow of any king or republic, the wiping out of all money and
finance or any of the manifold evidences of our modern world could not
for a moment be compared to what would happen to us with the sudden
destruction of plant life from the earth.

Food and drink, the very houses we live in and heat, medicines and
drugs, books and pictures, musical instruments and tires for
automobiles, all these and hundreds of our daily needs depend upon the
fact that plants of many different kinds grow upon the earth and in
sufficient amounts to be of importance. It is easy to say in opposition
to this that we get much food from animals, that we can drink water, and
that neither of these comes from plants. But water would soon be lost to
us if forests did not conserve it, and upon pasturage most of our food
animals depend for their life. The discovery of a single tree in the
mountains of northern South America made possible for white man the
malarial regions unfit for him before the advent of quinine. Just before
Shakespeare’s time sugar and tea and coffee became regular articles of
commerce. Not until the discovery of America was tobacco, Indian corn,
chocolate, the pineapple or the potato known to man. Upon the spruce
forests in the north depends much of our paper supply, from cotton we
get clothes and explosives, from hemp and sisal ropes, from a single
kind of Brazilian tree most of our rubber, and from rice a food that
sustains nearly half the world.

While it is thus plain enough that life depends upon plants now present
upon the earth it may not be so obvious that from certain ancient
forests has come the greatest source of artificial heat in the world.
Coal is nothing but the partial decomposition of vast forests, living
ages before man was first found upon the earth, subsequently buried, and
under the earth’s pressure forming soft coal, or where the pressure was
severe enough hard coal. When it is remembered that a dead, partly
decayed tree is only a fraction of its living size and that coal is
found in many parts of the world in tremendous quantities we get a
partial glimpse of what our debt is to a great forest that lived in
luxuriance no one knows how many millions of years ago, reached its
climax, and upon whose embedded remains we depend for heat.

Later on in this book will be given in greater detail some of the plants
useful to man and just how we have used them. Hardly any part of the
study of the plant kingdom has so much of interest as that dealing with
our utilization of the things that grow about us. From the earliest
struggles of our half-savage ancestors to grow definite crops rescued
from the wild down to our modern nut butter made from the partly
fermented meat of the cocoanut and shipped half round the world before
it is refined, man has constantly striven to use for his advantage the
plants most likely to prove valuable. Countries and empires have been
built upon such facts. Even to-day rubber from the Straits Settlements
and palm oil from Africa are deciding the economic life of those
countries.

But man’s use of plants, in fact his absolute reliance upon them, is not
the only reason for attempting to find out more about them, what they
are, where they came from, how they live and produce their young. A
knowledge of even a small part of such a science opens up a rich field
of inquiry involving a concept of plant life of greater interest than
mere bread and butter. For those with an eye to see and knowledge to
interpret, a landscape with its trees or flowers or marshes may contain
a host of hidden secrets of dramatic import. Unfolded before one may be
found a spectacle of struggle and strife, quiet tragedies of the forest,
the inexorable pressure of plants upon their neighbors, the woods upon
the prairies or an apparently forlorn hope of some plant living in a hot
desert or upon some icy mountain peak. And while these rather obvious
things are happening how much more is hidden of the adjustments that
leaves or flowers or roots or other organs of the plant are constantly
making to the conditions about them. Upon the perfection of such
adjustments to light, heat, or water, for instance, depends their very
existence. Mistakes are fatal, the forces of nature seem peculiarly
relentless, and it is literally a case where many are called but few
chosen. Of the untold millions of seeds produced each year few ever
grow, yet out of this enormous wastage springs all that makes the earth
not only habitable but the beautiful panorama of vegetation to which we
are so accustomed that it is nearly taken for granted.

The study of botany attempts to answer some of the questions raised
above and many others. Subsequent parts of the book will deal with what
plants are, the behavior of them, with the life histories of some of the
better known ones, with the grouping of plants in families and their
relationships one to another, with their uses to man, with the history
of their development from the earliest times, and finally with their
distribution over the earth. The latter will be discussed last because
it is the most important of all the phases of plant life. How plants are
distributed, whether as forest or prairie or thickets or what not,
depends upon the response of individual plants and their organs to the
conditions about them. The type of vegetation in different parts of the
world has been dictated by the success of the survivors in meeting
existing conditions and of having met them in the past. Upon this fact
rests our civilization to-day. Upon this fact there has been reared a
study the cultural, esthetic, and practical value of which may well
outweigh any other.

While the study of botany is necessarily a technical one with a language
all its own, its terms, though generally unfamiliar, are unexcelled for
their purpose. They will be avoided here as much as a clear
understanding of the subject will permit. The few that must be used will
be explained where they first occur and it is assumed that the reader
will understand their subsequent use.

CHAPTER I

WHAT PLANTS ARE

What we commonly call plants, such as corn or buttercups or an oak tree,
are so familiar that a definition of what plants are may seem needless.
It would be quite so if these generally recognized examples comprised
all the plant kingdom. Actually what are ordinarily thought of as plants
make up only a fraction of the great plant world. The fact that our
familiar roadside and garden plants produce blossoms followed by a fruit
and seed, such as peas and beans and all the ordinary flora of any
region, separates them at once from that other large group of plants
that do not. Common examples of the latter class are the green scum on
the ponds, moss, seaweed, the rust on wheat, yeast, disease-causing
bacteria, the smallest of all known plants, and many others. Most of
these organisms are so small that they can be distinguished only under
the higher powers of the microscope. Some of them in their habits and
growth are like the minute animals described in the volume of this
series devoted to that subject. In fact there are organisms about which
scientists are still in doubt as to their animal or vegetable character.

One or two characteristics common to most plants, however, separate them
from animals and these are their method of getting food and their
practically immovable mode of life. Animals, however simple, do eat and
digest their food, plants take various mineral substances from the earth
or air or water in the form of inorganic matter such as oxygen, carbon,
nitrogen, and all the food materials found in the soil, and transform
them, with the aid of sunshine, into the structure that characterizes
each particular form. _Plants, then, may be defined as any living
organism that, with minor exceptions, has the power to assimilate
inorganic substances and transform them into organic matter._ Nothing
else in all the realm of nature has this power. It is a possession
beyond all price, this ability to take from the soil and air and water
simple chemical substances and under the magic of sunlight transform
them into the wonderful plant life of the world. But this faculty has
its handicaps, for it is usually, though not always, associated with
inability to move from place to place, which, in some measure, even the
simplest animals can accomplish.

It will be readily understood that this definition of plants includes
many other things that are commonly attributed to the plant kingdom. For
our purpose the discussion of these relatively unfamiliar forms of plant
life will be left until later. A rough and ready distinction between
those plants that everyone recognizes as such and those others like
yeast and microbes, which are plants to most of us only by virtue of the
definition given above, is that the first group produce flowers and
seeds and the second do not. It should not be forgotten, and it will be
shown later, that this is not a true distinction, but for practical
purposes of dividing the plant kingdom it suffices.

1. FLOWERING PLANTS

The fact of outstanding importance to everyone who really looks at most
plants is that part of them are above ground and part below. This simple
observation carries with it the recognition of a fundamental difference
of plant structure, namely roots and stem. Most plants bear obvious
leaves, and at some time in their life flowers, inevitably followed by
fruits and seeds. The ideally perfect plant would consist, then, of
root, stem, leaves, flowers, fruit, and seed. These are subject to many
changes of form, sometimes they are put to strange uses, and
occasionally one or two may be lacking, as the stem is apparently from
many violets, and leaves from some cactus and from the Tjemoro tree of
Malaya. In fact, so varied are the different forms of these common
attributes of most plants, so important are these differences of
structure that no right understanding of plant life can be had without
examining each in some detail.

THE ROOT

The obvious purpose of the roots of plants is to serve as an anchorage
or holdfast. Their other and equally important function is to secure
food for the plant, a process that will be described in the part devoted
to Plant Behavior. Certain plants bear no roots and attach themselves to
the roots of other plants in which case they literally steal their food,
as does the mistletoe and some others.

Roots are of various kinds, depending upon the soil in which they grow
and upon the kind of plant to which they are attached. In the case of
_annuals_, which live only one year, as does the purslane, and
_biennials_, which live only two years, as does the fringed gentian, the
roots are mostly fibrous (Figure 1) and apt to be only slightly under
the surface. In _perennials_, which live many years, such as the
dandelion, the root is deeper and forms what is known as a _taproot_
(Figure 2). In shrubs and trees they are harder, woodier, and often
penetrate to great depths.

[Illustration: FIG. 1.--FIBROUS ROOTS

As illustrated by the common garden nasturtium.]

If we examine the roots of a tree, we find a large part of them are
woody, often as thick as the smaller branches, and it is only toward
their extremities that they branch out into the multitude of rootlets

[Illustration: FIG. 2.--TAP ROOT OF CARROT

A store of food for the second year.]

that creep through the earth seeking food for the tree. Some, as in the
spruce or hemlock, do not go very deep but spread great distances
through the soil in search of food, others, like the hickory, go nearly
straight down. The interesting feature of these tree roots is that the
part nearest the trunk is all but dead, and acts mostly as an anchor,
while the fibrous rootlets or even finer subdivisions known as _root
hairs_ at the extremities are the food gatherers. At the very end of all
rootlets and of roots is a _rootcap_ (Figure 3), harder than the rest of
the threadlike rootlet. This rootcap is, if not quite dead, at least
useless as a food gatherer, but serves as a tiny pioneer wedge which
forces its way among stones or other obstructions, so allowing the
living root hairs just behind to gather the food to which it leads the
way. In certain of the rocky islands of the Bahamas wild fig trees may
be seen, growing on the bare rocks, their roots sprawling in every
direction in search of a crevice through which the rootcap can force its
way. Such roots may extend thirty or forty feet from the trunk of the
tree over the bare rock in search of a favorable crack where they plunge
to the cool depths and secure the food and water necessary for life.

[Illustration: FIG. 3.--TAP ROOT OF SEEDLING

The figure shows the root cap at the extremity.]

Roots are not always of this common type. Sometimes, particularly in
certain biennials, they are swelled to form great thickened portions,
often weighing many pounds. The sweet potato is a familiar example, and
a related plant, one of our morning-glories, has an enormous perennial
root, known to weigh as much as fifty pounds. This swelling of the
roots of plants is a quite common characteristic of certain kinds and
has great commercial significance. Carrots, turnips, rutabagas, beets,
and parsnips are familiar examples. The purpose of such roots is to
store food for the plant, and this thrifty habit of some roots has been
turned by the gardeners to our advantage.

It is a common sight to see parts of a sidewalk heaved up by a tree root
and their force in this respect is tremendous. One of our common ferns
has been known to raise a weight of over 500 pounds, and even to break
through a concrete walk. Such is the force exerted by the roots of
plants that we can truly think of roots as pushing through the earth
almost regardless of obstacles, binding the soil together and not only
serving the needs of the plants, but actually holding the soil on steep
slopes. Where fire or ruthless lumbering has stopped this natural
process the washing away of the soil and exposure of the bare rocks
leaves desolation behind it.

[Illustration: FIG. 4.--ADVENTITIOUS ROOTS OF THE TOMATO

Produced from joints or injured places.]

While most roots live under the surface many grow in the air, and a few
grow from stems that are injured. The tomato vine often produces roots
at the joints or where it has been injured. Such roots, known as
_adventitious roots_ (Figures 4 and 5), are fairly common in many
plants, the common garden practice of making cuttings, which take root
under favorable conditions, being based upon this fact.

[Illustration: FIG. 5.--PROP ROOTS OF THE INDIAN CORN

Usually produced from the first joint above ground and serving as
additional anchor and food gatherers.]

But some plants produce roots in the air, as in poison ivy and the
trumpet creeper, without injury or the gardener’s skill, and are known
as _aërial roots_. They are some of the most peculiar and fantastic of
nature’s devices for allowing plants to grow in apparently unfavorable
places. In many orchids, some relatives of the pineapple, and a few
other air-inhabiting plants, the roots live wholly in the air, the
plants being fastened to a tree or even to a telegraph wire. Such plants
live on the air and water vapor, and are mostly inhabitants of moist
tropical regions.

Quite the most extraordinary of aërial roots are those produced in
certain kinds of fig trees. Starting perhaps a hundred feet in the air
and no thicker than a lead pencil they appear first as slender vine-like
streamers blown hither and yon by the wind. Eventually they reach the
ground and penetrate it, grow often to a great size and even form
trunklike connections with the tree top. The banyan tree of India is the
best known case of this peculiar habit. One which started from a single
trunk, subsequently sending out great numbers of aërial roots, has now
spread to such a size that it is over 2,000 feet in circumference, has
3,000 trunks, and once sheltered 7,000 soldiers.

A variation of this habit is the case of a giant fig tree of the West
Indies in which a bird may deposit the seed of another tree. The
seedling soon develops, sending out long, at first threadlike, aërial
roots which are wrapped around the tree trunk. As the roots increase in
size and further encircle the trunk they ultimately reach the ground,
where they are frequently a foot in diameter. Then the true nature of
the process becomes evident. For these apparently innocent aërial roots,
as they reach the ground, have so completely inclosed the old trunk and
their pressure is so great that they literally strangle the tree from
which they started. It is slower but just as deadly as the strangulation
of an animal by a boa constrictor, for these encircling roots cut off
by strangulation the ascent of the sap, thus killing the tree. Fate
sometimes overtakes them, however, as it is a common sight to see the
strangler meet the same end. Some of nature’s most ruthless battles are
fought out in this way, very silently, but very effectively.

THE STEM

[Illustration: FIG. 6.--ROOTSTOCK OF SOLOMON’S SEAL

The figure shows roots and bud scars together with the ascending stem of
the year’s growth.]

Nothing dies harder than generally accepted delusions, particularly
those regarding plant lore, and of all such incorrect impressions the
one that a potato is a root, is the hardiest and most difficult to kill.
Yet, the “eyes” of a potato give it away if one stops for a moment to
reflect that the eyes are only buds and buds grow only on stems. That is
one of the chief uses of stems--to support in the air the leaves and
flowers that come from its buds, and no matter if the stem, as in the
potato and many other plants, be ever so deeply buried their true stem
nature cannot be mistaken. Sometimes these underground stems are not
thickened but lengthened out, in which case, notably in common garden
iris, they are called _rootstocks_. Again, these buried stems may be
swollen, as in the potato, when they are known as _tubers_. Onions and
the jack-in-the-pulpit bear still other kinds of underground stems, and
there are many more, but they cannot be mistaken for roots, for it will
be seen from Figures 6-9 that on their under sides they bear roots
themselves. Besides this they bear buds or shoots, which no true root
ever does.

[Illustration: Fig. 7.--CORM OF JACK-IN-THE PULPIT

(After Gray)

Really an underground stem.]

Stems above ground, which is the most usual form for them, are of many
kinds, all serving the purpose of support to the leaves and flowers, and
as a means of carrying sap from the roots or underground stems to the
upper part of the plant, and also to carry certain foods to the roots
from the leaves, of which more anon. In the case of herbs, like
goldenrod or daisy, the stem may be apparently all pith on the inside,
with only a thin outer coating of harder substance, not unlike bark, but
usually green. If we examine the cut-off trunk of a tree, a quite

[Illustration: FIG. 8.--TUBERS OF THE COMMON POTATO

Potatoes are swollen portions of rootstock.]

different structure is apparent. Any lumberman can point out at once
“heartwood” and “sapwood” (Figure 78), and his distinctions are just as
good as those of the scientist, for he says in these two words as
plainly as can be said that heartwood is the oldest and sapwood the
youngest. The sapwood is nearer the bark and is honeycombed with
passages which serve to carry the sap from the roots to the tree top,
while just under the bark is the bright, green, living layer, known as
_cambium_, which is renewed each year. The _phloem_ is the carrier for
the food made in the leaves to the roots. It is the successive layers of
_cambium_, year after year, that gives to tree trunks their annual
rings. The age of almost all trees can be reckoned exactly by counting
these, one representing a year’s growth, and the tree’s rate of growth
estimated from the closeness of the rings. Fires or droughts, perhaps
long forgotten, here find a lasting record in rings so close together as
to be all but invisible. The part nearest the center of the trunk is the
heartwood, usually quite lifeless, yet in its maturity furnishing us
with lumber. It may be and often is completely decayed, without injuring
the flow of sap or the life of the tree for many years.

[Illustration: FIG. 9.--BULB OF THE ONION

Showing root and leaf growth.]

These two streams of sap, one going up and the other returning to the
roots, each in its proper channel, are interspersed with air chambers
that extend from the center of the tree out toward the bark, where they
end in inconspicuous dots called _lenticels_. It is as though nature had
provided an air-cooling device for the constant activity of these
diverse currents. These lenticels are prominent on the bark of cherry,
but whether obvious or not they are found in nearly all woody stems and
insure a constant supply of fresh air to the busy interior.

In palms, sugar cane, corn, bamboo, and many other plants there is not
any distinction between heartwood and sapwood (Figure 82), and in place
of bark there is nothing but an outer rind, harder than the interior
tissue. Such stems do not usually rot first at the center, have no
cambium, and have no annual rings. This method of growth and structure
is associated nearly always with definite leaf and flower forms peculiar
to it and differing from most other plants. So fundamental are these
characteristics, so uniform their occurrence and so clear are the
distinctions between them and other plants that botanists have divided
all flowering plants into those belonging to this group or to some
others. More will be said of this in the chapter on the Families of
Plants and Their Relationship.

The stems of some plants, such as the Big Trees of California, for
instance, are among the oldest and most permanent of living things.
“General Sherman,” one of the biggest in that most famous grove, was
nearly three thousand five hundred years old when Columbus discovered
America; it has lived through all the great periods of modern history,
and to-day it is over 270 feet high and 35 feet in diameter. No living
thing is so large or has lived so long. In Australia are great forests
of blue gum trees even taller than our Californian Big Trees, but not so
old nor so thick.

In the Pacific, off the coast of Oregon and British Columbia, a seaweed
is commonly found with stalks over 500 feet long, and in India the
rattan palm climbs over the tree tops for great distances, a single stem
not much thicker than a broomstick measuring over 700 feet long. The
search by leaves for light and air results in the stems of some plants
performing almost incredible feats. Whether it is one of the Big Trees
with a great massive trunk, or the rattan palm with its sinuous winding
through the topmost heights of the tropical forests of India, the result
is always upward to a “place in the sun.” This struggle for sunlight has
taken many forms in different plants, the ordinary vines like
morning-glory or grapevine, for instance, where the climbing stem is of
great advantage. Some vines always twine to the left, as the hopvine,
others to the right, as in the morning-glory, all seeking support from
something else, each adopting its own most useful way of getting its
leaves in the most advantageous position to catch the life-giving
sunshine. If we could look down on any forest from an aeroplane, the
striking efforts of nearly all plants, whether herbs, shrubs, vines, or
trees, to get the utmost sunshine for their leaves would be evident at
once. No apparently impossible twisting or bending of tree trunks or
reaching out of stems of vines but is to be found in the inexorable
struggle of stems to fulfill their task of giving the plant its chance
to reach “a place in the sun.” Sometimes mere climbing or twining does
not seem sure enough--it seems as though winds or the elements might
break loose the vine from its support and thereby kill its chances. In
certain vines this contingency appears to have been foreseen, and as if
to clinch their opportunity of growing onward they are provided with
special helps. Slender green _tendrils_, delicate prolongations of the
stem, begin, almost insidiously, to catch hold of the nearest support
and by a couple of turns about it and subsequent strengthening of their
tissues make a permanent holdfast. The grapevine is a case in point. And
as if this were not enough, certain other plants, such as the Boston
ivy, have small disks which attach themselves to bare walls or tree
trunks. This is to make assurance doubly sure, and it is this that makes
the Boston ivy so useful to the gardeners for covering walls.

Some stems accomplish their purpose not by holding fast to a support in
the air, but by creeping along the ground, as in the running blackberry,
and often in the Virginia creeper. The purpose is the same, and, as if
to confirm it, a few otherwise quite prostrate vines have their tips
turned upward to the light, notably in the case of the creeping
speedwell.

In certain plants the stem may assume curious forms due to special
conditions under which they live and to which adjustment is necessary
for the plant’s existence. In deserts, for instance, the cactus produces
practically no leaves (Figure 10) and the green stem performs not only
the function of leaves but acts as a storage for water. Where water is
scarce this is of tremendous advantage, a single cactus having been
known to store up 125 gallons. A similar habit of the cactuslike spurges
in South Africa gives as weird an atmosphere to parts of their
landscapes as we find in Arizona. It is as if the stem of such plants,
being unable to push its leaves (it has none) up into the light, takes
over some of the functions of leaves and makes up the deficiency by
adopting other methods

[Illustration: FIG. 10.--COMMON PRICKLY PEAR CACTUS (_Opuntia Opuntia_)

Native along the Atlantic Coast. The green joints of the stem function
as leaves and store water.]

to secure the plant’s survival. Other stems, looking and acting like
leaves, reveal their true nature by producing buds, and the curious
feature of the common butcher’s-broom (Figure 11), often colored scarlet
for Christmas decorations, bearing flowers from the middle of what is
apparently a leaf, but is actually a modified stem, is explained by this
ability of stems to modify their habits to suit conditions. The
butcher’s-broom is an inhabitant of dry regions along the Mediterranean,
where a reduction or

[Illustration: FIG. 11.--BUTCHER’S-BROOM

(_Ruscus aculeatus_)

Note leaflike stems with flowers arising from the center.]

absence of leaf surface is a decided advantage. In many partly desert or
dry regions this production of leaflike stems or branches is common, an
excellent garden example being asparagus, which came originally from
Europe and the feathery growth of which is all stem. In Tasmania a kind
of yew tree produces no leaves, all the foliage being modified stem,
which is true of many kinds of spurge in the West Indies, where an
almost impenetrable scrub is largely made up of a shrub which is
apparently covered with leaves, all actually part of the branches and
stems.

[Illustration: FIG. 12.--DUCKWEED

The smallest known flowering plant, with _no_ leaves and tiny leaflike
stems floating on the surface. Flowers are borne from the margin of the
stem. (Eight times natural size).]

While stems, such as the Big Trees or the giant cactus, may be among the
largest of nature’s creations they may be also the smallest, as the
duckweed that floats on ponds is the tiniest of all flowering plants and
its flat expanded surface is wholly stem. Figure 12 on this page better
illustrates this strange modification of a stem than words could do.

From what has been read it will be seen that stems are not “just
stems”--they are among nature’s most ingenious devices to secure the
survival of the plant. Whether buried in the ground, and producing,
almost by stealth, buds that develop into mature plants, or thrusting
leaves to the utmost limits of their reach, or climbing by an
intricately varied mechanism, or changing their character to suit desert
conditions, or floating on the water--it matters not. Each modification
of form or use secures to the individual plant its chances to survive;
and in most cases its only chance, as anyone may see by the sudden death
which follows a series of changes which prevents a stem from performing
its proper tasks.

THE LEAF

As the palm reader is supposed to be able to tell your history and
future from veins in your hand, and as the veins in the wing of a
butterfly tell their story to an entomologist, so the veins of a leaf
are more significant than almost any other characteristic of a plant.
Most leaves have their veins, or skeleton, with a single midrib and many
branches off it on each side, which themselves break up into a fine
network of veins. Such leaves are _netveined_ (Figures 13-24). Others,
such as corn and grass, have the veins running side by side from one end
of the leaf to the other, sometimes with small branches off them, but
instead of the veins forming a network they are parallel, and such are
called _parallel-veined_ leaves (Figure 38). In the chapter on Plant
Families and Their Relationship more will be said as to the amazing
regularity with which netveined leaves are associated with certain kinds
of flowers and parallel-veined with other kinds, how these distinctions
have been recognized since hundreds of years before Christ, long before
their true import was understood. There are variations from both these

[Illustration: BANYAN TREE (_Ficus bengalensis_). A fig tree of India,
whose adventitious roots make frequent connection between the tree top
and the ground. Starting as thin, whiplike streamers these roots
ultimately form new trunks. (_Courtesy Brooklyn Botanic Garden._)]

[Illustration: LACELEAF (_Aponogeton fenestralis_). A submerged aquatic
plant, with permanently skeletonized leaves, and an inhabitant of forest
pools in Madagascar. (_After Engler & Prantl. Courtesy of Brooklyn
Botanic Garden._)]

[Illustration: ROOT HAIRS WITH FINE SOIL PARTICLES ATTACHED. Note soil,
water, and air spaces. Much magnified. (_After U. S. Department of
Agriculture. Courtesy of Brooklyn Botanic Garden._)]

[Illustration: FIGS. 13-24.--FORMS AND TIPS OF LEAVES

Fig. 13. A linear leaf with an acute tip. Fig. 14. Lanceolate leaf with
an acuminate tip. Fig. 15. Oblanceolate leaf broadest above the middle.
Fig. 16. Ovate, broadest below the middle. Fig. 17. Spatulate, broadest
above the middle and with an elongated base. Fig. 18. Elliptical. Fig.
19. Obovate in which the general shape is ovate, but broadest toward the
tip. Fig. 20. Oblong. Fig. 21. Orbicular or nearly round. Fig. 22.
Deltoid or somewhat triangular, an ovate leaf with a broad base. Fig.
23. Kidney-shaped or reniform with heart-shaped base. Fig. 24. Peltate
leaf of common garden nasturtium; note circular blade with leafstalk
attached to the center.]

types, but in nearly every case, once the difference is noted--and
scarcely any other character of a plant is so much worth notice--they
cannot be mistaken.

During the winter nearly all leaves are folded in various ways in a bud
for protection from the elements. Nature shows herself in some of her
wisest moods in the selection of methods to accomplish this. In some
buds, notably those of the horse-chestnut, the bud is coated with a
sticky substance to protect the tender young leaves inside. In others
there is a hard outer coat, as in the hickory, impregnable to the most
driving sleet, others again have the leaf rolled so tightly and pointed
so sharply at the end, as in the beech, that water cannot cling to the
bud nor soak in, until the warmth of spring gives the signal for the
annual miracle of the bursting out of foliage. Leaf buds are sometimes
hard to find on certain plants, as they are formed at the base of a
leafstalk and covered by it during the growing season. It is only as the
leaf falls in the autumn that the hollow base of its stalk is seen to
have hidden during the summer the young bud for the following season.
The plane tree or sycamore is a good example of a plant where no leaf
buds can be found until the falling of the leaves in autumn.

The forms of leaves are infinite in their variety, and the reasons for
some of their peculiarities in this respect are not yet understood. The
average netveined leaf is obviously composed of a _blade_ (Figure 25),
and at the base a stalk known as a _petiole_. Sometimes at the base of
the petiole--which is lacking in many leaves--there are two tiny
leaflike appendages, called _stipules_, which are of no apparent use to
the plant, and, as if in recognition of this fact, they often fall off
long before autumn. In some plants, however, stipules are permanent,
while in certain others they are never found, as, for instance, in the
horse-chestnut tree.

[Illustration: FIGS. 25-35.--FORMS AND BASES OF LEAVES

Fig. 25. Simple leaf with blade, leafstalk (petiole), and two stipules
at the base. Margins of the leafblade serrate or saw-toothed. Fig. 26.
Leaf with a sagittate base, or shaped like an arrowhead, the lobes
pointing downward, and with entire margins. Fig. 27. Retuse or
emarginate tip, somewhat indented. Fig. 28. With the base auriculate or
with rounded basal lobes. Fig. 29. Hastate, like an arrowhead but the
lobes pointing outward. Fig. 30. With cuneate base (wedge-shaped). Fig.
31. Cuspidate tip with a usually hard and stiff point. Fig. 32.
Perfoliate, the leaf bases joined and the stem passing through them.
Fig. 33. Truncate, the top flattened. Fig. 34. Pinnately lobed, with
deep indentations cut toward the midrib. Fig. 35. Palmately lobed, out
toward the top of the leafstalk.]

The outline of leaves is as varied as nature itself. Some of the common
kinds are shown in drawings (Figures 13-24), which tell more of the
story than pages of description could do. Their margins, too, their
tips, their bases (Figures 25-35), all parts of them, in fact, are so
variable and yet in each kind of plant so uniform, that in the
description of the plants of any region the botanist has used these
characteristics of leaves as one method of identifying the particular
plant in hand.

The terms used to designate these different kinds of leaf margins or
forms of blade are precise, nearly universally used, but need to be
studied only by those who, because of special fondness for the subject,
are likely to need them in using books which are beyond the scope of the
present one. If, for instance, the reader is interested in finding out
what his native roadside plants are, he would need a book describing
them, and there are many for different parts of the country. In such
books he would find these terms, which say so much in a single word
(there are other sets of terms for flowers, fruits, and seeds) totally
unfamiliar and quite likely to disgust him at the start. A little study
may open up to him that most interesting and easily accessible of
recreations, a first-hand familiarity with the wild flowers of one’s own
neighborhood.

All leaves are not as simple as the figures show them to be. In many the
midrib or principal vein is much elongated and there are small
_leaflets_, sometimes even scores of them, all fastened to a common
stalk. Such are called _compound_ leaves (Figures 36-37), which may be
found in ash, hickory, rosebushes, blackberries, peas, beans, and
thousands of other plants.

[Illustration: FIGS. 36-38.--COMPOUND AND PARALLEL-VEINED LEAVES

Fig. 36. Palmately compound leaf, the five leaflets all arising from the
tip of the common leafstalk. Fig. 37. Pinnately compound leaf, the
leaflets arising from the sides of the common leafstalk. Fig 38. A
parallel-veined leaf. All the other leaves figured are netted-veined.]

While leaves are literally factories in which one of the most wonderful
things in the world is produced, it is so much a part of what plants do
or their behavior that the story of it will be given in the chapter on
Plant Behavior. Sunlight is absolutely necessary for the process, and to
reach this sunlight leaves are attached to their stems in a variety of
ways. Some are always opposite each other, as in the common privet,
lilac, or honeysuckle; others always alternate, as in the mustard or the
rose. There are many variations of these simple arrangements, but in
every case the process results in giving each leaf the utmost exposure
to the light without which the plant must wither and die. So vital is
this exposure to light that in some plants parts of the leaves produce
_tendrils_, as in the case of peas, in order that some near-by support
may be used. In one African relative of our lily, this change of leaf
form has been so great that its long slender leaf tip is wonderfully
adapted to reaching up and catching by its curved tip some support to
lift it from the gloom of the tropical forest floor.

Looking down from above on any small plant or bush, or from the sky on a
forest, about all that can be seen are the thousands of leaves, all so
arranged that it is as though some celestial photographer asked every
one of them to so place themselves that they would all be “in the
picture.” The competition between leaves on the same plant and between
leaves on rival plants is infinitely keener than the friendly pushing of
a crowd to get in a picture, _and it lasts forever_. Furthermore,
failure to get in means certain death. So intricate is the method of
leaf arrangement, so marvelous the adjustments that all plants must make
to insure ample light, that it is not inaptly called _leaf mosaic_. As
we shall see in the chapter on Plant Distribution, particularly in
forests, certain variations or partial failures of the process have
far-reaching results.

If leaves did not perform this most important function to perfection,
all animals, including man as well, would perish, and it would almost
seem that their obligation to us and the plant world might stop there as
long as their success in reaching the light is so overwhelming. But
there are no union hours of labor, no regulation as to the kind of work
leaves may perform, and some actually reach out for new tasks to do, and
do them. In one, our common pitcher plant, the leaf, as is implied by
the name, is formed into a slender hollow pitcher, wide at the mouth,
but narrow at the base. Inside the pitcher are slender downward-pointing
hairs so arranged that an insect may crawl in, but never out. The lower
down the luckless insect gets the more certain is its death, and, to
clinch matters, there is a tiny pool at the bottom where it is not only
drowned, but, due to the composition of the mixture in the pool,
digested. Only a very few plants can do this; only a minute fraction of
the world’s vegetation can digest animal matter. Some experiments on the
pitcher plant, which grows in bogs, show that it will digest bits of
beefsteak dropped into the liquid at the base of the pitcher.

In the East Indies and in Africa there is a pitcher plant--in fact,
scores of varieties of them--which grows up on the branches of trees. In
this case the pitcher may be as long as some of our American kinds,
often twelve to eighteen inches, and many of them are attached to a
slender leafstalk two to three feet long, by which they hang suspended.
Insects, literally by the thousands, are caught in these gaudy traps,
for many of the pitchers are beautifully colored, and near the opening
they secrete a sweetish liquid that lures their prey. They are, in fact,
such curious and handsome plants that they are commonly grown in
greenhouse collections.

Nature sometimes finds still other ways of using strange and
curious-shaped leaves, and in our American bogs is a group of plants,
also insect digesters, still more unusual than the pitcher plants. In
bright sunny places in open bogs one may often find small reddish,
glistening plants, called sundews, usually only a few inches tall,
covered with sticky hairs. In fact, the glistening is due to the
secretion of the sticky substance, a tiny drop of which may be found at
the end of each hair. Flying insects are caught in these leaves, and, as
a fly on fly paper, the greater the struggle the more involved does the
insect become among the sticky threads. Once caught by such a plant,
escape is practically impossible.

Lying in ambush for chance insects, as these sundews and pitcher plants
do, may seem nearly the limit of what is to be expected of leaves.
Merely to be always on the job, with a plentiful supply of insect
digester, might seem to be all that could well be expected from what,
after all, are only modified leaves. But nature’s devices are infinite,
and there are still other ways to accomplish the apparently impossible.
In a small section of the southeastern States there grows a plant that
not only lies passively in wait for insects, but actually captures them.
This flycatcher, known as Venus’s flytrap, has two valves to the leaf
blade, supported on a stout broad stalk so arranged that their fringed
surfaces face each other. If an insect--and many do--alights between
these valves, they close together rapidly and the prisoner is hopelessly
caught by the interlocking marginal bristles that fringe each valve. In
this case there are glands on the face of the valves, against which the
live insect is tightly pressed, and which secrete a digestive fluid.
When nothing remains the valves slowly open and are ready for the next
victim. They may be made to close by slight irritation with a lead
pencil, and it is the impact of the insect that releases one of the most
curious examples of movement in leaves known to us. There are a few
other plants in different parts of the world that by still other
modifications of their leaves catch and digest insects, but none of them
are to be considered as “insect eaters,” or other names implying that
they have definite designs on the life of passing insects. The process
is sufficiently remarkable, the success of the operation so sure, that
there is nothing gained by attributing to such plants, as many have done
in the past, malignant characters that are possibly confined only to
man. The whole wonderful process is more reasonably explained by
realizing that all these insectivorous plants are so by virtue of
necessity, that many of them are bog plants, which are often hard put to
it to get suitable food, and that the extraordinary change of shape and
function is but one more contribution of leaves to the economy of
nature.

In dry or desert regions, where the conservation of moisture is
essential to plant growth, water storage by leaves is nearly as great an
aid to the plant as we have seen it to be in the stems of cactus, South
African spurges, etc. Our common century plant, whose leaves are, in
some kinds, a hundred times thicker than in ordinary foliage leaves, is
a good example of leaves adapted to water storage. In our southwestern
deserts hundreds of species of plants can exist only by virtue of the
fact that their leaves are so changed in their form or structure that
they serve as reservoirs for water storage. This may be accomplished by
thickening, or it is more often contrived by a thick coating of hairs.
The surfaces of thousands of different kinds of leaves are clothed with
hairs either on the upper or lower side, or sometimes on both sides. In
many cases they are quite obviously protection from too rapid drying out
of the leaf. In others, as in the nettle, the hairs secrete a stinging
substance which seems to insure the plant against grazing animals.

Leaves, then, are for something more than to provide the beautiful
foliage which is their most spectacular accomplishment. So varied is
this in its beauty, from plain green leaves to the wonderful coloring
found in begonias, coleus, and many other garden plants, that the sheer
beauty of the panorama of foliage is likely to blind us to the more
important uses of leaves. First of all must we consider them the
factories, in which night and day are produced the food of all plants
and most animals. Then in certain cases we have seen that, by every
ingenious device known to nature, they perform other special work, such
as helping the plant to climb where that is necessary, catching or even
capturing insects and digesting them when that peculiar service is
demanded of them, and, finally, serving as storage reservoirs in regions
where water is scarce. Probably no part of the plant works so
unceasingly each season at its varied tasks. In the autumn, dropping to
the forest floor, its decomposition furnishes still other food for the
plant, and, to crown all, this busy life and by no means unprofitable
death leaves behind it, as a promise for the continuance of the work, a
snugly protected leaf bud which will repeat the process the next season.

THE FLOWER

While the plant’s and, consequently, our debt to the leaf is seen to be
tremendous, it cannot be ignored that, if plants produced nothing but
leaves, the end of all plant life would come with the death from old age
or disease of the present generation of plants. Except for those kinds
that reproduce themselves by division or extension of their rootstocks,
which bear buds, there would be no provision for increase. As only a
comparatively small number of plants can reproduce by this method, it is
obvious that something more must be provided to secure new generations
of plants. Flowers, and the fruits and seeds which inevitably follow
them, do this. All plants, with some exceptions to be noted later,
produce flowers at some time in their life. In the case of the century
plant, only once, after which they die. But except for ferns, mushrooms,
seaweed, yeast, bacteria, and some other forms of so-called flowerless
plants, a flower or blossom is to be found at some stage in the life of
all plants.

If we examine the leaves of a goldenrod, we find that they are large
below and diminish in size toward the top. Just below and among the
flower clusters they are so much reduced in size and often changed in
color that they cease to be ordinary foliage leaves, and are known as
_bracts_. The occurrence of bracts is nearly universal in flowering
plants, and they form not only an apparently transitional stage between
leaves and flowers, but an actual one.

In a complete and perfect flower there are, at the bottom of it, a row
of green leaflike sheaths which

[Illustration: FIGS. 39-45.--THE FLOWER

Fig. 39. A perfect and complete flower. _A_, petals, all of them forming
the corolla; _B_, sepals, all of them forming the calyx; _C_, the
stamen, composed of (_C_) the filament, and (_C_^{1}) the anther, which
produces the pollen; _D_, the pistil, consisting of the swollen base
(_D_) the ovary, a slender shank (_D_^{1}) the style, and the swollen or
branched tip (_D_^{2}) the stigma. (H. D. House, “Wild Flowers of New
York.”) Fig. 40. Typical flower of the pea family. Two petals unite to
form the keel (below), two more unite to form the wings (center), the
remaining and larger petal forms the standard. In most plants of this
family the stamens and pistils are concealed within the keel. Fig. 41.
Two-lipped inequilateral flower, common in such plants as Salvia,
Snapdragon, etc. Note the united calyx and corolla. Fig. 42.
Gamopetalous or united and regular corolla of the Fringed Gentian. Figs.
43, 44, and 45, flowers of the _Compositæ_ or daisy family. Many small
flowers grouped in heads and usually surrounded by one or more series of
bracts. Fig. 43. Flowers all tubular, the small one at the left being an
individual flower. Common examples are Boneset and the common garden
Ageratum. Fig. 44. Flowers both tubular and with rays, the tubular in
the center and the rays on the margin. Below is an individual tubular
flower on the right, and on the left an individual ray flower. Note that
its five united divisions correspond to the five petals in other plants.
Common examples are the daisy, sunflower, black-eyed Susan, etc. Fig.
45. Flowers all ray flowers, an individual one at the right. The
_Compositæ_ with only ray flowers usually have a milky juice and have
often been grouped in a separate family, the _Cichoriaceæ_. Common
examples are dandelion, chicory, and lettuce.]

surround and often half inclose the brightly colored petals within. This
outer covering of flowers is called _calyx_ (Figure 39 B), the
individual parts of it, where they are separated, _sepals_. Their chief
use is to protect the interior petals while they are inclosed in the
bud. The calyx may or may not have bracts just underneath it, as it does
very conspicuously in the case of the flowering dogwood, whose white
“flowers” are really only brightly colored bracts. The transition
between bracts and calyx is not difficult to see in many plants, and
where it is impossible the evidence from their internal structure
confirms what our eye might be inclined to doubt.

Just inside the calyx is what most people call the “flower,” which is
really composed of more highly colored sepals, but which we call
_petals_ (Figure 39A). Where these are joined together the collection,
which forms tubular flowers like the lily of the valley, is called a
_corolla_. It is, of course, the petals or corollas of flowering plants
that give our landscapes their greatest beauty, their most gorgeous
coloring. While this from one point of view amply justifies a prodigal
nature in strewing the earth with beautiful flowers, the true value of
the color to the plant is in quite other directions, which will be
explained a little later.

Toward the base of the corolla, or sometimes on the petals or sepals,
may be found a series of slender appendages, usually threadlike or a
little thicker, crowned at the top by a distinctly large knob. The
individual appendage is known as a _stamen_ (Figure 39 C), its
threadlike portion a _filament_ (Figure 39 C), and the knoblike top an
_anther_ (Figure 39 C^{1}).

Directly in the middle of the flower there is still another organ,
usually swollen at the base, slender in the shank, and either thickened
or branched at the tip. This central part of nearly all flowers is
called collectively a pistil (Figure 39 D), its swollen base an _ovary_
(Figure 39 D), the slender shank the _style_ (Figure 39 D^{1}), and the
thickened or branched tip a _stigma_ (Figure 39 D^{2}). A perfect and
complete flower, then, is composed as follows:

Calyx Corolla Stamens consisting Pistil consisting
or + or + of filaments + of ovary, style,
sepals, petals, and anthers, and stigma.

The stamen is the male organ of reproduction and the pistil the female.
The actual process of fertilization, pregnancy, the forming of the fruit
and later the seed, and the latter’s birth of a new plant, comprise one
of the most fascinating of those provisions of nature which secure the
perpetuation of the plant world. In the life history of even the
commonest weed along the roadside there is this constant renewal of life
by sexual reproduction, just as in animals and in man. In the chapter on
“How Plants Produce Their Young” will be found some account of this
supreme function of flowers, after which, as if their usefulness were
over, they wither and perish.

Not all flowers are perfect or complete. Some lack petals, as the
buckwheat, where the colored calyx replaces petals. Others have neither
calyx nor corolla, as in the sycamore or plane tree. Most plants,
however, have both calyx and corolla. In some very few plants certain of
the flowers have no stamens, when they are said to be _pistillate_ or
female flowers, and certain others have no pistils, when they are called
_staminate_ or male flowers. In other words, the sexes are in different
flowers in the same cluster or plant, as is true of the walnut and
hickories, when they are said to be _monœcious_. In still others the
sexes are on entirely different plants, in which case they are
_diœcious_, as in practically all willows. In the latter case there
are _pistillate_ or female plants and _staminate_ or male plants.

While it is a commonplace that peas do not look like daisies, nor a
carnation like a rose, this simple observation does not begin to tell us
of the wonderfully different flower shapes and colors that are to be
found along any roadside. The perfect and complete flower that we have
been studying is quite regular, composed as often as not of four or five
petals, as many sepals, with five or ten stamens and perhaps a single
pistil. Yet there is literally no limit to the variations from this
scheme, and some of these must be understood here in order that the
life-histories and behavior of plants discussed in later chapters may
tell their full story.

The figures on page 44 show a regular flower, with five separate petals
and sepals (Fig. 39). Such flowers are said to be _polypetalous_, i.e.,
separate petals. Sometimes three of the petals are larger, two smaller,
in which case the flower is lopsided or, as it is said, _inequilateral_.
Again all the petals are united to form a regular and equilateral tube,
as in lily of the valley, when they are _gamopetalous_, _i.e._, united
petals (Figure 42). As we shall see in the chapter on Plant Families,
this is a distinction between two great groups of plants, as important
in their classification as negro and white man are in classifying
humans.

In peas, beans, the locust tree, and related plants the petals are much
changed to form an irregular flower, with a keellike or prow-shaped part
made from the uniting of two petals. Two more unite to form the wings,
and the remaining and larger petal forms the standard. Figure 40 and the
explanation under it illustrate this unusual form of flowers.

Our common garden salvia shows still another type of flower, which is
tubular and irregular (Figure 41). There is an arching, hoodlike
structure at the top overhanging a lower lip. This kind of irregularity
is common in thousands of different sorts of plants and, usually, it is
a device to insure fertilization of the flower by insect visitors. So
necessary are these for pregnancy in many plants, that an orchid, once
discovered in Madagascar with a tube eighteen inches deep, puzzled the
botanists, who were unable to understand how the plant produced seed in
the absence of any known insect with a tongue as long as that. Darwin
said at once that such an insect would one day be discovered on that
island. Years after, Baron von Humboldt, a German naturalist, found the
insect and explained the mystery.

Perhaps there is no feature of plant life that shows such an amazing
amount of variation as the forms of flowers, and while only a few of the
simplest deviations from the normal have been discussed here, it must
not be forgotten that this infinite variety is a reflection of the
ingeniousness of nature in securing a plentiful supply of seed. Form,
color, the secretion of sweetish nectar, the night or day blooming of
different kinds of flowers, every device that will make fertilization
certain, by the flower itself, by insects, or even by the wind, is used
in such prodigal fashion, that we come to see the importance of it to
all plants only by a realization of the complexity of it and the
provisions against its failure.

One apparently most lavish method of securing fertilization is the
arrangement of flowers in clusters. While many flowers are quite
solitary, the great mass of individual plants produce a few or dozens,
or even hundreds of flowers--in fact, certain relatives of the common
carrot may produce over a thousand flowers in a single cluster. The form
and plan of arrangement of these clusters follows a rather definite
scheme, and here, as in the case of leaves and parts of individual
flowers, the figures tell the story better than words. In the common
dandelion and daisy, and their thousands of relatives, the “flower”
(Figures 43-45), as commonly understood, is really composed of scores or
even hundreds of true flowers in each head. In the case of the daisy the
yellow center, if picked apart, is seen to be really made up of scores
of tiny tubular flowers, each just as truly a flower as a single rose.
The rays, or what are incorrectly called “petals,” which fringe the
golden center with white, if carefully separated and examined closely,
will be found to be also a complete flower, the true petals of which are
all joined to make the strap-shaped ray. If one looks sharply, the
united edges of these petals may be seen by the ridges or channels that
represent their joined edges. Because plants of this sort produce two
sets of flowers in each head, one conspicuous by its brightly colored
rays and with another tubular set in the center which makes doubly
certain the fertilization and seed supply, they are considered the most
highly developed of all plants. It is not a close aristocracy, nor an
exclusive one, for over eleven thousand different kinds of plants,
scattered all over the world, have their flowers arranged in this
fashion or some slight modification of it. They possess, above all
others, the certainty that there will be no slip in their fertilization,
pregnancy, and subsequent birth of a new generation. Because this is
the great object of all flowers, and these daisylike plants have brought
it to such perfection, they are most surely to be classed as the highest
type upon the earth to-day.

[Illustration: FIGS. 46-50.--TYPES OF FLOWER CLUSTERS

Fig. 46. A spike, the individual flowers attached directly to the common
stalk. Fig. 47. A raceme, a spikelike cluster where individual flowers
are stalked. Fig. 48. An umbel, the individual flower stalks all arising
from one point. Fig. 49. Individual flower stalks of different lengths
but the cluster usually flat-topped (corymb). Fig. 50. A flower cluster
in which the end of the stem is terminated by a flower from the base of
which side branchlets similarly tipped with flowers arise (cyme).]

While highly irregular flowers are common in nature, conspicuous
examples being the orchids in any florist’s window, or the milkweeds
along the roadside, they can nearly always be seen to have various
changes in the shape of their petals, or sepals, or stamens, or pistils,
which are adaptations to their mode of life, but which always result in
fertilization. Some plants, true monstrosities of nature, are not only
far from having the usual arrangement of flower parts, but they even
produce increased numbers of one part at the expense of others.

Double buttercups, and hundreds of our most beautiful garden blossoms,
have been rescued by cultivation or the arts of the gardeners. Some
roses seem to be practically all petals, but for every increase of
petals there must be a decrease of some other part of the flower, and
more often than enough it is the stamens and pistils that lose out in
this transformation. Just as there is a decrease almost to the vanishing
point in the birthrate when people become too effete and cultivated, so
in plants there seems to be a point beyond which they cannot be pushed
without suffering partial or often complete inability to produce young.
The more highly they have been developed, oftentimes the greater their
beauty, the less able are they to see to it that the chief function of
flowers is accomplished. Such garden plants are increased by root
division, cuttings and other arts of the gardener. Naturally true double
flowers are almost unknown in wild plants, and the habit seems to have
been brought about by too easy a time of it, too little struggle, too
much food, or by any other of those things that produce effete but
beautiful things, charming in their way, but of no significance in the
sturdy struggle for existence that all wild plants must meet or perish.
Another curious modification of a flower bud is cauliflower. Here the
bud has been so developed, its calyx, sepals, etc., so transformed that
the large, cabbagelike head, produced at the apex of the main stem of
the plant, has by so much lost all semblance of a flower that it is
actually a vegetable.

[Illustration: FIG. 51.--FLOWER ARRANGEMENT PECULIAR TO THE ARUM FAMILY

Fig. 51. The outer leaflike tubular or hooded spathe surrounds in our
common Jack-in-the-Pulpit a clublike spadix, upon which are crowded the
tiny flowers.]

No feature of a landscape gives us more pleasure than its flowers, over
which poets have sung and artists have painted their most charming
pictures, even a musician has composed a very beautiful piano piece, “To
a Water Lily.” But their true place in the scheme of nature has a deeper
significance: the wonderful color and symmetry of their parts, the plan
of their arrangement, their transformation into curious forms, like the
Madagascar orchid, and hundreds of others--all these point to their
supreme function, an act of self-sacrifice comparable only to the fall
of a leaf when its task is done. Petals, too, wither and die when the
fertilized ovary, already a mother, begins the slow process of maturing
its young and the end of the flowering stage is reached. Such a climax
is this in certain plants that the whole plant dies, as we have already
noted in the case of the century plant. The toddy or wine palm of India,
often sixty or seventy years old and more than a hundred feet tall,
flowers only once, and, as if in recognition of the fact that it has
done that for which it grew, slowly dies as the seed ripens. More humble
_annuals_, like buckwheat, and hundreds of others, live only one brief
growing season, produce flowers and seeds, and then die, leaving behind
them the only means of perpetuating their kind. The dormant seed carries
over the winter the life they were themselves unable to maintain, as
perennials and woody plants do in their buds.

THE FRUIT

The number of different kinds of fruits that one can buy even in the
greatest markets in the world is so small, compared to all fruits that
are annually produced by plants, that they might almost be likened to an
ear of corn as against a Missouri cornfield. If, as we have seen, all
flowering plants must produce fruits, then what we commonly call such
can be only a fraction of what actually makes up nature’s annual
harvest. It follows that fruits often occur in unfamiliar disguises and,
as we shall see presently, some of the things we have been calling
fruits may be so only partly, if at all.

Disregarding what we call fruits and looking at it from the plant’s
point of view, a fruit is anything in which, or upon which, a seed is
developed or ripened quite without regard as to whether it is edible by
man or not. As the ovary is the female organ of reproduction and
contains the yet undeveloped seed, it follows also that fruits are
practically always a development of some part or modification of the
ovary or the upper end of the flower stalk upon which it rests and from
which it is often scarcely separable.

Familiar enough is the distinction between dry fruits, such as a pea pod
and fleshy ones like oranges, and this quality of being fleshy or dry is
practically universal. Among fleshy fruits a few well-known types may be
mentioned, such as the orange, tomato, grape, gooseberry, and cranberry,
all true _berries_. There are, of course, thousands of less familiar
examples of berries, but, whether with a hard rind as in the orange or
not, they are a direct development, or often a mere swelling of the
ovary, with sometimes the adhering calyx, and contain the seed. In
apples and pears, known as _pomes_, the fleshy part is a development of
part calyx and part the receptacle upon which the ovary is supported
while still in the flower. The ovary in these fruits is the
parchmentlike interior which contains the seed. Plums and cherries,
which have a single stone, instead of numerous seeds buried in the
flesh, are known as drupes. These familiar examples are matched by
thousands of others of which we hear nothing, all _drupes_ and all
formed directly from the ripened ovary and without much change, except
the increase of size, juiciness and large development of the tiny
immature seed, now transformed into a stone. In the watermelon, pumpkin,
and related plants, is still another kind of fleshy fruit, called a
_pepo_. All of this, including the hard rind, is transformed ovary and
calyx completely incorporated, and forming in the pumpkin perhaps the
largest fleshy fruit known. In a considerable number of plants there is
not a single ovary, but several, or in some cases many. These
occasionally all develop into what is called an aggregate fruit, of
which examples are the blackberry, mulberry, magnolia, and many others.

While it would be logical to think that these fleshy fruits were
designed to make delicious food for man, that, in the light of what we
have seen to be the real function of the flower, is an assumption which,
while flattering, is far from the truth. It is much more certain that
fleshy fruits help plants in the dispersal of their seeds and that this
fleshy, juicy character is just one more device of nature to see to it
that not only do plants produce seeds, but that the seeds are carried
and so spread the plant over considerable areas. Birds and animals eat
such fruits in enormous quantities and, in fact, bird migrations are
thought to be not so much response to winter cold as to the fact that
fruits are scarce then. When it is remembered that some birds make
tremendous flights, often over 10,000 miles in a few days, their
capacity to spread seeds through their droppings may be imagined. In the
chapter on plant distribution some truly remarkable cases of such seed
dispersal will be given.

The chance of having seed carried great distances, because it is
embedded in a fleshy, often brightly colored fruit, would seem to put
plants having dry fruits at a disadvantage. Birds and animals cannot be
expected to look after the dispersal of those fruits that are neither
tempting to the sight nor to the taste. And it must be confessed that
quite other qualities in dry fruits insure their dispersal. Some are so
nutritious, like the _acorn_, that thrifty squirrels store them over
the winter, as they do many other seeds which are harvested from dry
fruits. Various grains are often so stored by man, and rice, wheat,
buckwheat, and other cereals are common cases. In nearly all grains the
seed fills so completely the fruit that cereals are very generally, but
mistakenly, called seeds. A grain of wheat or corn is just as complete a
fruit as a watermelon. Only its outer coat and inner seed are so closely
welded together as not to be usually recognized as a fruit, with the
seed inside.

One of the commonest types of dry fruit is the _capsule_ (Figure 53),
well named, as it is almost an exact counterpart of the capsule of the
druggist, in that it is in many cases composed of a lower part and an
upper, usually merely a domed lid. Others again, instead of splitting
around the sides, split from top to bottom. Still others, as peas and
beans, known as _legumes_ (Figure 57), are pods that not only split
lengthwise, but have no central partition, as do many other fruits of
the same general type. When the seed is ripe nearly all pods and
_legumes_ finally split open, and the seed or seeds tumble out. A few,
as in the violet and touch-me-not or jewelweed, apparently realizing
that merely to spill out ripe seeds at the proper time will not spread
the species very far, open their fruits with a sudden explosion and
literally shoot their seeds considerable distances. The artillery plant,
commonly grown in greenhouses, a delicate feathery herb from tropical
America, opens its flowers with a report like a toy popgun and shoots
its small pollen grains for several feet, but not its seeds as stated by
some.

But many fruits do not open at all and seem to be at the greatest
disadvantage in the effort to insure

[Illustration: FIGS. 52-60.--TYPES OF DRY FRUITS

Fig. 52. The strawberry. The fleshy part consists of the modified upper
end of the flower stalk or receptacle, while the true fruits are the dry
achenes on or embedded in the surface and popularly called the seeds.
Fig. 53. A three-celled capsule splitting lengthwise as in the common
Iris. Fig. 54. Fruit of the cocklebur, the hooked prickles of which are
admirably adapted for clinging to the fur of animals. Fig. 55. Pods of a
plant of the Mustard family, which split down both edges, unlike the
true peas, which split down only one edge. Fig. 56. Two types of achenes
of the daisy family tipped with plumed bristles, greatly aiding their
carriage by the wind. Fig. 57. Common garden pea--a typical legume. Note
that it splits only on one side. Fig. 58. The samara or two-winged fruit
of the maple. Fig. 59. The samara or single-winged fruit of the ash.
Fig. 60. The dry two-pronged and bristly fruit of the unicorn plant
(_Martynia_), admirably adapted for dispersal by animals.]

dispersal of their seeds. Greater food value to birds and animals
overcomes this in some kinds, and another help is that some fruits of
this sort are covered with hooked prickles or barbs (Figures 54 and 60).
The common weedy burdock, the barbed fruits of which may often be found
sticking to the fur of animals in great quantities, is a case in point.
There are whole groups of plants that rely on this method for seed
dispersal, notably the avens, tick-seed, tick trefoil, and many shrubs
in the tropical regions.

Where the fruits are neither barbed nor very good to eat, and so
apparently doomed to be more or less permanent stay-at-homes, nature has
provided some of them with the proper equipment for flight through the
air. Winged fruits like the maple are to be seen on any windy day during
their season scurrying before the breeze, and consequently spreading
their kind over considerable distances. In the maple there are two
wings, joined at the base where the seeds are embedded in the wings, and
the fruit is known as a _samara_ (Figure 58), or key fruit, from a
slight resemblance to an old-fashioned key. Ash trees bear fruits that
are a slight modification of this type and may be carried considerable
distances by the wind (Figure 59).

In the dandelion, daisy, and nearly all its thousands of relatives, this
faculty of setting sail in the air has been carried to the greatest
perfection, just as we saw its flowers were. In this family of plants,
the largest in the world, the fruit is mostly tipped or surrounded by a
small collection of very fine bristles. The fruit, known as an _achene_
(Figure 56), is so light that with the added buoyancy of this tiny
collection of down it can be transported great distances. Some have
been known to fly hundreds of miles in severe storms, and, as we shall
see in the chapter on plant distribution, these tiny plant balloons have
played a conspicuous part in spreading their kind over the face of the
earth. Cat-tails also, together with many other plants, have this
faculty and make up by its possession for the lack of fleshy or
otherwise desirable fruits that might be carried. All _achenes_ are not
winged, those which dot the surface of the strawberry being imbedded in
the luscious flesh, which is not really fruit at all. Only the achenes
on the strawberry are true fruits, the fleshy part being merely a
development of the upper part of the flower stalk and not of the ovary
(Figure 52).

Fruits, then, cannot be restricted to the common understanding of them.
They are transformations of the ovary, in which or upon which seeds are
nursed, and upon which most plants depend for the dispersal of their
seeds. We shall see later on how fruits have fulfilled their destiny,
how some are fit for their true function only when they have been eaten
by birds, and when some digestive juice has released them from the
impotence they would suffer without being eaten, how a whole forest has
been changed in the West by the busy activity of squirrels upon the
fruits and seeds of a single kind of fir tree; how the fruit of the
coconut palm has been spread throughout the tropical world because it
can float in the sea securely protected from injury from salt by the
impervious coverings of its fruits.

THE SEED

As the final stage in the development of all plants is their seed, with
the dropping of which they bid good-by to their fellows, it is not
perhaps remarkable that in the seed of all flowering plants is the germ
for the new generation. To seeds which may be as small as the mustard,
so often mentioned in the Bible, or as large as the coco de mer, or
double coconut, from the Seychelles Islands, often fifty pounds or over,
is intrusted by cunning nature the one final and most important act in
the whole kingdom of the plant world. Nearly all plants would die off
forever if seeds did not have in them the germ of life, apparently quite
dead, but actually only dormant. This living germ may persist for years,
sometimes even a hundred years, and yet with the proper conditions it
never fails to sprout.

Seeds have inside them a tiny plantlet folded and ready to grow when the
seed splits to release it. Also, in the seed is stored up food to
sustain the new plant until such time as its own roots begin to act.
This young plantlet is known as the _embryo_, and to this all actions of
the seed are subservient.

As the seed splits, and the young plant develops its first leaves and
rootlets, there is shown one of the most remarkably uniform tendencies
in plant life. In all plants with net-veined leaves the young plantlet
starts life with two leaves, or _cotyledons_, as these first leaves are
called, and this whole group of plants are thus known as _dicotyledons_.
In plants with parallel-veined leaves the young plantlets start out with
a single cotyledon and are therefore called _monocotyledons_. In only
the pines, spruce, and a few other evergreen trees the seedling plants
have several cotyledons and are known as _polycotyledons_. All the
flowering plants in the world belong to one of these groups, so that
merely to see the germinating seed tells the story at once. The linking
of parallel-veined leaves and a single seed leaf, and net-veined leaves
with two seed leaves, is also associated with very definite arrangement
of their flower parts, their method of growth and other characters.
Something has already been said of this in the discussion of stems and
leaves, and more will be found in the chapter on plant families. No more
beautiful example of the plan or scheme of nature is to be found than
these characteristics of all plants, and in seeds we find the first hint
as to which army the plant will join, under which banner it will fight,
and under what generalship it will develop. Nothing tells us so much as
these first seed leaves, pushing their way up through the soil and
revealing, as they burst above ground, to what place in nature their
destiny will consign them.

Flowering plants, which make up the bulk of the vegetation of the earth,
have been discussed in some detail, not only because they furnish us
with all the things that make life possible, but also because they show
perhaps better than anything else the division of labor, all striving
for one end. Roots, the food gatherers. Stems, the framework for the
foliage and its means of reaching the light, or as a storage house for
reserve food. Leaves of many kinds, all factories working night and day
to make the necessary food. Flowers of every hue and shape to lure
insects, or by other means secure union of male and female. Fruits to
ripen the result of this mating of the sexes. And, finally, the seed
carrying with it the yet unborn life. Each part occasionally losing
itself in order that the end may be accomplished, many of them changing
their form or even their function where that is of advantage, all in
their separate ways doing their task, the end of which they cannot see,
and the fruits of which they will never enjoy. Nowhere is it so true as
in plants that to save oneself there must be the capacity to give
oneself. Untold millions of leaves fall, or trees crash down, or seeds
are developed, each fulfilling their destiny which is to insure the
perpetuation of their kind. As we shall see later on, there are many
mistakes, many apparently futile attempts, thousands are wiped out that
one may be saved, and in the past multitudes have gone out forever. Yet
the result of it all is the plant world as we know it to-day, each kind
struggling to increase its sphere of influence, or to cover more of the
earth’s area. The combat between different kinds is inexorable, yet the
capacity for sacrifice on the part of different organs, in order that a
certain individual kind may win, is literally beyond belief.

2. FLOWERLESS PLANTS

In the light of what has been said about flowers it may well be
questioned how anything can be a plant and still have no flower. The
fact is that flowers as we commonly understand them are unknown in the
plants about to be discussed, but that what _corresponds_ to a flower,
and performs the _function_ of a flower all plants must and do have. In
the case of most flowering plants the possession of flowers is one of
the beauties of nature in its most resplendent mood, while in the
so-called flowerless plants the functions of flowers are performed by
tiny microscopic organs, even the existence of which has been only
recently discovered. Because flowering plants produce their sexual
organs in such a gorgeous setting, for all the world to see their
matings they have been called _phanerogams_, which means literally
visible marriage, while the flowerless plants which perform similar
functions in more secret ways are called _cryptogams_, meaning hidden
marriage.

These _cryptogams_ or flowerless plants occur in far greater numbers in
the world than flowering plants, but their size in most cases is very
much less. Many individuals are so small, as in the case of bacteria,
that a single one can only be seen after it has been magnified many
hundreds of times by the microscope. Of the cryptogams some of the
largest, certainly the most beautiful, and probably the best known are

THE FERNS

In nearly all woods one may find delicate feathery plants with graceful,
usually much divided leaves that nearly always start up from the ground
like a slowly opening, but somewhat fuzzy coil. (Figure 62.) Ferns, at
least most of those that grow in America, uncoil their leaves in this
way, almost without exception. The accompanying figure shows the
procedure, and in addition to this character one may hunt in vain for
flowers.

While they bear no flowers we already know that nature could not leave
them with no means of reproduction without abandoning them to a
childless old age and the consequent extinction of the race of ferns. So
far from the truth is this that ferns make up a goodly proportion of the
world’s vegetation, and there are many hundreds of different kinds
known. The lack of flowers, of course, explains why ferns do not bear
seeds which are matured in a fruit or ripened ovary.

On the back of the leaves of most ferns, along or near the edges of the
finer subdivisions, one may

[Illustration: FIGS. 61-63.--COMMON WOODLAND FERN

Fig. 61. A general view. Fig. 62. Its uncoiling spring condition. Fig.
63. The back of one of the smaller divisions of the leaf showing the
collection of spore cases (sori). These are sometimes borne on special
leaves, but in most of our American kinds on the backs of ordinary
foliage leaves.]

find, at the proper season, collections or rows of tiny, usually
brownish dots. These contain often thousands of microscopic objects
known generally as _spores_, and from this fact the dots are called
spore-cases, or more technically _sori_. (Figure 63.) The process by
which new plants are formed is a

[Illustration: AERIAL ROOTS OF FIG TREES HANGING OVER THE EDGE OF A CAVE
IN THE RAIN FOREST, SAN LORENZO, SANTO DOMINGO. (_Photo by the author.
Courtesy of Brooklyn Botanic Garden._)]

[Illustration: VENUS’S FLYTRAP, AN INSECTIVOROUS PLANT OF THE
SOUTHEASTERN UNITED STATES. The fringed valves of its leaves close
together when an insect alights between them. (_Courtesy of Brooklyn
Botanic Garden._)]

somewhat complicated one, but the spores in these brown dots are the
agency which makes reproduction possible, and the actual mechanism of
it, one of the most interesting achievements in plant life, will be
described in the chapter on “How Plants Produce Their Young.” Sometimes
the spores are not borne on the backs of ordinary foliage leaves but on
special leaves that bear, very often, nothing else.

Ferns are much like ordinary flowering plants; except for their lack of
flowers, they have all the root, stem, and leaf characters of their more
showy neighbors. While most of them have compound leaves, even sometimes
twice or thrice compounded, a few have simple, narrow leaves without
teeth, and one kind in tropical America has threadlike leaves. In many
tropical rain forests, so called from their dripping wet condition,
ferns form large trees, and these tree ferns are among the most graceful
and feathery of all plants. There are, too, a few climbing kinds--one,
called the climbing fern, is a native of the eastern United States. Then
there is the walking fern, that seems to upset the statement that plants
do not move as animals do. It sends out delicate runners that, rooting
at the tips, form new plants, often several feet from the parent plant.

The characteristic of having, even in the simplest form, stems, leaves,
and roots, with all that this implies in their internal structure, marks
them off at once from all other flowerless plants. In ferns there is
always some internal equipment for carrying food from one part of the
plant, the roots, to another, and this ability is possessed by virtue of
ducts or vessels through the stem and leaves. This system, found in all
flowering plants and ferns, but _nowhere else in the plant world_, is
called the _vascular system_, or literally, a vessel system. We shall
see how important was the acquirement of this system of vessels, when we
get to the chapter on the History of the Plant Kingdom. Its appearance
upon the earth marks as important a stage in the development of plants
as the dawn of a definite backbone did upon animal life.

Ferns, then, are _vascular cryptogams_ because they do have conducting
vessels in their stems, and they produce their young by a process of
hidden marriage which will be described later. All other cryptogams or
flowerless plants are without this system of vessels and are called
therefore _non-vascular cryptogams_. Numerically they are tremendously
important; upon them depend many manufacturing processes like bread
making, brewing, and all arts using fermentation. But they are hardly
recognized as plants by the general reader, and because of their size
and the necessity of studying them with a microscope in order to
understand their structure they will be treated here only briefly.

OTHER FLOWERLESS PLANTS

The remaining flowerless plants, having no duct system in their make-up,
are, as we know, called _non-vascular cryptogams_. This is a general
term for a very large group of plants, some quite obvious and well known
like a mushroom, for instance; others so small or of such uncertain
structure that they are not even well known by experts. This great mass
of plant life, more numerous than all the other kinds of plants
combined, contains many different forms, some of which are of gigantic
size. A single plant of a certain Pacific Coast seaweed regularly
exceeds in length the height of the tallest

[Illustration: FIGS. 64-67.--TYPES OF FLOWERLESS PLANTS

Fig. 64. A moss plant. Fig. 65. A mushroom, a common type of the fungi,
which include also puffballs, molds, and many disease-causing
microscopic organisms. Fig. 66. A common seaweed, a representative of
the algæ, which include the green scum on the top of ponds, and the kelp
from which fertilizer is now being made. Fig. 67. A lichen, a common
cryptogamous plant on logs and rocks. Our native kinds are usually
grayish-green in color.]

known trees. And yet other inhabitants of the water, certain kinds that
float freely, are microscopic in size. The latter occur in such enormous
numbers that their tiny decomposed skeletons after dropping to the
bottom of the sea form the diatomaceous earth, so much used in polishing
machinery. The commercial product now comes from deposits of these
skeletons laid down in past ages, which, due to changes in the land and
water surfaces of the earth, are now found in Virginia, Nevada,
California, and in Bohemia. All these must have been in the bed of
waters long since gone, which teemed with these microscopic organisms.
To-day there are over ten thousand different kinds known, yet so small
are they that their dimensions are measured in thousandths of an inch!

Somewhat lower in the scale of life--and by this we mean simpler in
structure--than the ferns are the _mosses_. (Figure 64.) There are
thousands of different kinds, but everyone is familiar with the
collective growth of the commoner sorts which makes the velvety mossy
carpet in our woods. The individual plants are small, but in many kinds
sufficiently large to be seen without a microscope. Most important of
all, practically every one of them has the ordinary green color of the
better known plants, and as we shall see in the section devoted to
“Leaves as Factories for the Making of Food,” that stamps them at once
as plants, if other things did not.

Mosses are almost infinite in their habits, some growing on the dry
rocks or trunks of trees, many growing in moist woods, some in the
water, and immense quantities of certain kinds in bogs. The peculiar bog
mosses, known as sphagnum, play an important part in forming peat and
perhaps coal. While mosses are otherwise not of much commercial
importance, they are among nature’s most beautiful ground covers,
carpeting many a nook and dell with a soft, velvety, almost cushionlike
growth.

Although they are rather small, they appear to have a somewhat definite
stem and tiny leaflike appendages of it, without, however, having the
vascular system found in all ferns. Mosses might almost be considered
miniature ferns, of which they are perhaps only simple ancestors. Their
vegetative or green parts vary much in shape, size, and the arrangement
of the tiny leaflike appendages, and while most of them are a beautiful
bright green, nearly all the bog or sphagnum mosses are rather ashy gray
in color. In most of the typical mosses there arises from among the
vegetative growth of them a slender stalk, at the top of which is a
small capsulelike organ. This contains the spores, and it is upon this
long slender stalk and its spore-filled capsule, really marvelous in its
internal structure and mechanism for the discharge of the spores, that
mosses depend for their reproduction. As in the case of the ferns this
process will be considered later, along with that of some other plants.
This whole story of how plants produce their young, perhaps the most
fascinating of any part of the study of plant life, is so fundamentally
a part of their history and shows nature in her most maternal moods,
that a special chapter will be devoted to it. There we shall see, as a
whole, how these vastly different acts of fertilization and reproduction
are, in different groups of plants, all responses to that insistent
command for life, more life, in a never-ending stream.

The chief characters to remember about mosses are that they are very
simple, but practically always green plants that have some
differentiation into stem and leaf; that, while they have no vascular
system, their structure and particularly the mode of reproduction
suggests that they are not very distant from the ferns, and quite likely
simple ancestors of them. These characters are of more importance than
appears on the surface, as we shall presently see, for they mark mosses
off from many other nonvascular flowerless plants which have quite
different structure and altogether different mode of life.

If you will turn to the chapter on Plant Behavior and read particularly
the sections on “Leaves as Factories for the Manufacture of Food” and
“Borrowing from the Living and Robbing from the Dead,” you will see in
the food habits of the plants there noted the great difference that
exists between plants, like mosses and ferns, that have green coloring
matter in them, and those we are about to mention that never do. The
lack of this green coloring substance tells us at once that plants of
this sort live only on the dead remains of other plants. In the case of
these nonvascular flowerless plants there are certain modes of growth
that, in some forms at least, are always associated with this
scavenger-like food habit.

The common mushroom (Figure 65) is the best known of that large group of
plants, called generally fungi, which produce no green coloring matter,
have no leaves attached to a stem, and _always_ live on decayed
vegetable, or sometimes inhabit living animals, even man himself. The
mushroom with its brownish stalk and buttonlike dome is familiar enough,
but there are literally thousands of different kinds, a common sort
forming “brackets” on the trunks of trees. While perhaps everyone would
recognize these as plants, peculiar as they are in their often weird
shapes and unusual as they nearly always are in their color, there are
many minute kinds of fungi that scarcely anyone would even think of as a
plant, and yet for better or worse they are incomparably the most
powerful plants in the world. For upon these microscopic fungi man
depends for many things. It is certain kinds of them that make the
manufacture of cheese possible. They turn milk sour (pasteurizing milk
is merely stopping their work), give to yeast its power of “raising”
bread, all brewing depends upon them, every process of fermenting the
juice of fruits for wine making or for whatever else, the decay of
wood--all these processes and scores of others, whether for the good or
evil of mankind, depend upon the work of these plants, any one of which
is so small that a single individual must be magnified hundreds of times
to detect it. Many of them are the “germs”--better called bacteria--that
cause diseases like tuberculosis, cholera, typhoid, anthrax, and
diphtheria. All surgeons wage incessant warfare against a host of them
that attack wounds and form pus. They live in our intestines and have
much to do with digestion, and unhappily with indigestion, so that we
may be said to carry about with us a whole flora of them! Nearly all the
diseases of plants, like the blight of potato and the rust on wheat, are
caused by them. Some other kinds live in the soil, and many flowering
plants depend absolutely for getting their food upon the work of these
fungi. Unfortunately their minute size and consequently obscure mode of
life demand technical skill and the use of the microscope to detect
them, so we must leave them here, always keeping in mind that these
smallest of all plants are charged with a power for good or evil; so far
as man’s life is concerned, greater perhaps than all other plants.

While most fungi, particularly those familiar ones like mushrooms and
puffballs, are inhabitants of the land, the remaining group of
nonvascular flowerless plants are nearly all water plants. Most of the
better known ones live in the sea, and as the wrack or tangle washed up
on the shore we recognize them as seaweed. The _algæ_ (Figure 66), which
is a general name for such plants--and they live in the sea, in fresh
water, and even on dry land--are, so far as structure is concerned, the
simplest of all plants.

Those that are fastened to rocks are often beautifully colored, much
branched, and many kinds bear small bladders that act as buoys. These
coast seaweeds are generally of different colors, those nearest the
surface being generally greenish, the deeper water kinds reddish or
brown. None of these seaweeds are found at great depths, because the
really deep parts of the ocean are almost, if not quite, dark. Seaweeds,
and in fact all the algæ, have green coloring matter in them, even where
this is masked by reds and browns, as is the case in some particularly
showy kinds. As you will find in the section on “Leaves as Factories for
the Making of Food,” no plant with green coloring matter can live in the
dark. That is why seaweeds are not found in the great deeps of the sea,
some of which are several miles below the shore line along the coasts,
and are so cold and dark that neither plants nor animals can grow in
them.

Those seaweeds that grow along the coast, and are uncovered by the
retreating tides, are well known by everyone, but by far the greater
number of algæ float without anchorage of any kind. One kind that has
been torn from its anchorage occurs in such enormous quantities that off
the coast of America it has formed literally a floating island composed
entirely of dense mats of a species of seaweed. This place, known as
the “Sargasso Sea” from the name of the seaweed forming it, was the
terror of old mariners and Columbus’s ship was fouled in it for two
weeks. The area occupied by the weed is several hundred miles long and
wide, and while old sea yarns about ships being caught in it and never
escaping are gross exaggerations, it is certainly one of the most
curious of plant growths, due entirely to a nonvascular cryptogam.

Of those kinds that are never anchored the number is legion, and in
addition to those forming the diatomaceous earth, already mentioned,
there are many more. They form almost the only food of hosts of
creatures of the sea, but because of their floating freely in the water,
the consequent difficulty of collecting them, and their unusually minute
size, little is likely to be known of them, except by the experts.

Other algæ are always found in fresh water and form the scum found on
stagnant pools. Individuals of any of these are so minute that, while
under the microscope they are of the greatest beauty, their structure
must remain for most of us a sealed book.

SUMMARY OF WHAT PLANTS ARE

We have now traced, in only the briefest fashion, the outlines of what
plants are, reversing the order of nature in beginning with those most
complex but best known, the flowering plants. As we shall see later,
these are the climax of prodigal nature and are to be considered the end
rather than the beginning of plant life on the earth. Then, and still
more briefly, have we stopped to see those less known plants that
produce no flowers, such as the ferns, mosses, fungi, and finally the
seaweeds or algæ. These are all to be considered as the ancestors of
flowering plants, the ferns the nearest to them and the algæ probably
the most distant relatives. The development of plants from the minutest
alga up to our most gorgeous flowering plant, is an infinitely slow and
painful process. With many mistakes, with its pathway strewn with the
wreckage of forlorn hopes and false starts, it is incomparably the most
dramatic story in the plant world. Some of its details will be told in
the chapter on the “History of the Plant Kingdom.”

Nor can we leave the discussion of what plants are without some mention
of the thing that really makes up their structure, whether it be a
microscopic bacterial organism or the Big Tree of California. For the
unit of all animal and plant life is the _cell_. In its simplest form it
is merely a minute sac with a definite wall and inside the wall is a
substance known as _protoplasm_, literally _protos_, first, and
_plasma_, thing formed. It is protoplasm that forms the living tissue of
all plants and animals; it is life itself. No one has ever succeeded in
making any, notwithstanding that many learned men have tried for years.
Its inclosure in the cell wall, its power of self-division and
consequent multiplication of the units, make up those first things about
which most of us can never know much, but the end of which we recognize
in the beauty of plant life all about us. For only under the highest
powers of the microscope may cells be seen and studied. Just as bankers
reckon mills as a definite unit of a cent, and yet none of them has ever
seen a mill, so we must think of cells as the definite unit of all
living things, although most of us will never see a cell. But, unlike
the mill, cells may be seen by those equipped to see them, and this
study, the development and grouping of them to form all the varied
objects that inhabit the plant world, is known as _histology_. It is
literally the internal history of plants and animals, and lies quite
outside the scope of this book. What we must never forget is that
whatever knowledge we have gained, either from the foregoing account of
what plants are, or from our observation of them, is, after all, only a
partial notion of them, as unsatisfactory as our estimate of what people
really are, from merely looking at the outside of the houses in which
they live. The outer form we may know and admire, the inner substance
must ever remain for most of us a secret treasure house the value of
which is certain, but the key to which we do not possess.

CHAPTER II

PLANT BEHAVIOR

1. LIGHT AND ITS IMPORTANCE TO THE PLANT

Practically all that has been said in the first chapter relates to what
plants are, their organs, or what we may call the architecture or plan
of their framework. But what they do with this elaborate structure is as
important as what we do with a house that may contain every modern
improvement but is never a home until these things have been put to use.
One of the chief concerns of any architect is to see to it that the
house has as much sunshine by day and as attractive illumination by
night as possible. Nature, that greatest of all architects, also sees to
it that plants get the utmost necessary sunlight, but for a much more
important reason than the mere attractiveness of sunshine, be that ever
so beautiful. For light, the life-giver of all green things, is so
absolutely essential to plants that experiments to grow them in the dark
have always failed, and many gardeners now use electric light in
greenhouses in order to prolong the short daylight of winter. It is the
lack of light that makes celery blanch.

Plants grown in the house inevitably turn toward the windows, even
plants growing against a wall turn their leaves away from it--nowhere
can one find living green things that do not find the light as surely
and persistently as men try to get their food or their mates. Many
examples of this could be given and must have been noticed by everyone.

Sometimes seeds germinate under a barn floor for instance, and the puny
pale little plantling reaches out slender stems, all of which turn, as a
compass turns to the north, to perhaps a crack of light in one corner of
the building. We have already seen how the search for light will carry
the slender rattan palms of India hundreds of feet to the topmost leaves
of the forest. Individual plants, and, as we shall see later, whole
forests make desperate efforts to get to the light. We know already,
that the struggle for light is just as bitter as the struggle for food
by roots. And finally if, as we have many times proved by experiments,
plants die when grown in a dark room, what is it that light does for
plants and how is a process carried on that everything leads us to think
is of the greatest possible importance? Quite obviously it is not the
mere beauty of sunshine dancing upon the landscape, as entrancing a
picture as that may be any summer afternoon, with the play of sunshine
and shadow on the tracery of foliage. That green color of the foliage,
the almost universal green of so much of the earth’s vegetation, restful
to tired eyes, providing us with the most pleasant shade, has wrapped up
within it the secret of just what sunshine does for plants. For under
the magic of light acting upon this greenery one of the most important
industries in the world, the manufacture of food, is constantly going
on.

LEAVES AS FACTORIES FOR THE MAKING OF FOOD

It must be clear enough from the start that to call a leaf a factory for
the making of food forces us to decide at once whether this is a mere
way of speaking, or whether, incredible as it may seem, anything as
thin as a leaf _can_ really produce food. As we eat lettuce, and
millions of cattle graze every day, leaves as food producers win handily
on that score. But to understand how food is produced in such a tiny
factory demands that we walk about in it for a bit, study the inside of
it and especially its many small chambers within which is not only the
machinery, but some of the finished product stored up for later use.

Unlike modern factories there are many entrances, from any one of which
we can begin our tour of inspection. On the under side of nearly all
leaves and on the upper side of some there are scores or even hundreds
of small pores called _stoma_, so small that only with a microscope can
they be seen. These entrances through the factory wall, are carefully
guarded by a pair of watchmen whose business it is to see neither too
much dry air gets in nor too much of the product of the factory gets
out. They see to it, also, that waste products are thrown out at the
proper time. These watchmen, or _guard cells_, as they are called, are
constantly on the job, work almost automatically, but their chief
function is connected with the proper ventilation of the place, and will
be discussed later under “How Plants Breathe.”

Once past the entrance it is obvious that we are in one of the strangest
of all factories, for none of the rooms are truly square or oblong and
their irregularity as to outline would drive your average foreman into
profanity. Yet they are certainly divided into distinct classes, at
least as to size and as to what the rooms contain. Some are apparently
filled with nothing but air and have direct connection through the stoma
with the outdoors. These are called _intercellular spaces_. Others, and
these are most important, are filled mostly with the green coloring
matter that gives the leaf its color. This substance is known as
_chlorophyll_, its individual units as _chloroplasts_, or literally,
chlorophyll bodies. Quite independently of these chlorophyll cells or
rooms, or the intercellular spaces which correspond to halls, there are
some large and many small tubes. These are the veins of the leaf and
their finer branches and by their direct connection through the stem to
the roots, serve as the ducts through which some of the raw materials
are brought into the factory.

This green coloring matter or chlorophyll is perhaps the most important
substance in nature. Without it all except a very few plants would die,
and even in those beautifully colored leaves like coleus or caladium
chlorophyll is always found, but in these colored leaves it is merely
obscured by other coloring substances. It is in the chlorophyll that the
ability resides to take the inorganic substances through the roots or
from the air, and by the aid of sunlight transform them into organic
substances like starch and sugar. Nothing else in all nature can do it;
without this faculty, which the commonest green leaf possesses, the
earth would prove uninhabitable within a single year. Just what
chlorophyll is chemically is not yet thoroughly known, but the thing of
chief interest is that it is hardly ever found in parts of the leaf not
exposed directly to the sunlight, and that during the autumnal coloring
and before the fall of the leaf chlorophyll is carried to other parts of
the plant, and quite possibly stored for use the following season.

While the composition of chlorophyll is not surely known, iron is
certainly one of its constituents, as plants deprived of iron lose
their green color. It also is known to contain oxygen, carbon, hydrogen,
and nitrogen, but merely to catalog what we know about its make-up does
not tell us that it is a living green substance and that sunshine sets
it in motion. Just exactly how light acts on chlorophyll no one really
knows; we merely know that it does so act and that the result is one of
the marvelous secret processes of nature, perhaps like the secret of
life itself forever hidden from man. In our tiny factory, then, we have
raw products coming from the roots and through the stoma from the air;
machinery of the most efficient type, for chlorophyll works night and
day, and constantly renews itself while producing the finished products;
energy from the sun; and finally the complete manufactured products
which are foods in the shape of starch and sugar. During the growing
season there is no banking of the fires, no stoppage of this most
important of all industries, no strikes or lockouts. Each part of the
whole works smoothly and with the nicest precision--in fact so perfectly
does this process keep on going, so complete is the orderliness of the
place, and so regular are the completed products turned out, that no
modern factory manager or workman but can learn something from a rather
close study of this smallest but most efficient factory in the world.

Some of the raw products are delivered to the leaf from the roots where
they have been absorbed by another process that will be considered a
little later. These consist of water and the inorganic substances
dissolved in it, popularly called sap. Carbon and oxygen come mostly
from the air, sometimes separately, more often in the form of a
combination called carbon dioxide which is one of the chief
constituents of the gas thrown off by man as he breathes _out_. Now
these inorganic substances, contained in the sap or derived from the
air, are literally mixed by the chlorophyll and form, always with the
aid of sunlight, substances known as _carbohydrates_, the commonest
example of which is sugar. Some form of sugar is one of the earliest
results of this process, but sugar is quite easily dissolved in the sap
which has contributed to its manufacture, and the excess sugar is thus
removed. Otherwise it would clog the machinery and prevent the
production of fresh supplies. This first step in the manufacturing
process has not inaptly been called _photosynthesis_, the meaning of
which _photos_, light, and _synthesis_, combining by means of, suggests
in a word the necessity of light and the combination of the inorganic
substances mentioned above. Of course this process of photosynthesis is
not as simple as the brief account of it suggests, for it is actually a
complicated chemical process only part of which is yet understood. It is
fairly certain that it goes step by step; it is quite certain that the
beginning is inorganic and the end organic compounds like sugar.
Something is known also of the wear and tear on the chlorophyll, its
waste products, and how it keeps itself not only fit but provides for
its own constant renewal. One of the excess or by-products in this
initial manufacture of sugar is oxygen. This is either used in other
ways by the plant, or more generally it is thrown off through the stoma
into the outer air. Oxygen, as one of the necessary constituents of the
air that man breathes _in_, is thus thrown off, while, as we have seen,
carbon dioxide, a poisonous gas which we breathe _out_, is a necessity
for this manufacturing process in all green plants. Hardly any trick of
nature so completely fulfills the wants of animal and plant life as this
mutual exchange of by-products--in the case of animals it is the waste
of respiration, in plants it is the wastage of sugar making and some
other changes that go on in the plant just after this stage.

The amount of sugar made, carbon dioxide taken in, and oxygen given off
by this process suggests that while leaves may be very tiny factories
they are among the most efficient in the world. Assuming an area of leaf
surface equal to about a square yard the amount of sugar made would be
about one-third of an ounce in a day or nearly three pounds in a single
growing season. Carbon dioxide withdrawn from the air would average from
the same area of leaf surface about two gallons a day or over three
hundred gallons for the season. As an equal amount of oxygen is given
off by the leaf, it becomes clear that as all of this interchange must
go through the stoma the functioning of these and their guardians must
be nearly one hundred per cent perfect. As we shall see a little later,
they perform still other duties with even greater perfection. When we
stop to reflect what an absurdly minute fraction one square yard of leaf
surface is to the total leaf surface in the world, we come to some
realization of the gigantic proportions of this process of manufacturing
sugar and exchange of gases mutually useful to animals and plants. While
in the United States most of the leaves fall in the autumn, the great
bulk of the vegetation of the world holds the greater part of its leaves
all the year, notably in the vast evergreen forests in the north, and of
course practically all tropical vegetation. Chlorophyll in such places
works continually and what the total of sugar production may be no man
can even guess.

Sugar, although the first step in the process, is not the final one, and
the leaf has still other tasks to complete. Some of the sugar is used up
in the process of renewing the chlorophyll, some of it is moved to other
parts of the plant where in sugar cane it forms the world’s chief sugar
supply; but the remainder is transformed into starch, a substance that
is not dissolved by the water of the sap, and is therefore capable of
permanent storage either in the leaf itself or in other parts of the
plant, notably in the tubers of the potato, the solid part of which is
nearly all starch. The conversion of sugar to starch, which is really a
means of contriving to properly store the product of the factory, is
done by certain ferments known as enzymes. Just what enzymes are or even
how they work is not well known, but apparently they have the faculty of
converting certain substances like sugar, and in the process they
neither use up nor materially change their own composition. It is
certain that the conversion of sugar to starch is an elaborate chemical
process, but it is accomplished by these enzymes, the very existence of
which has only recently been discovered. Enzymes not only do this, but
they convert starch which is insoluble into a kind that may be dissolved
and thus carried to different parts of the plant. Upon this power
depends the storage of starch in roots, tubers, seeds, or wherever else
it is found in the plant, and it is of course upon this power man
depends for the food supply of the world. Wheat or corn, potatoes, rice,
all the foods that are rich in starch produce none in that part of the
plant harvested by man. All of it has come by the process which is only
sketched in its briefest outlines in the foregoing paragraphs. All of it
must come from that green coloring matter of nearly all plants which,
while mostly confined to leaves, is not always so. And wherever
chlorophyll is found this process goes on even in the simplest plants.
Because it is so overwhelmingly a characteristic of leaves and, as we
have seen, leaves are the one organ of the plant upon which man pins his
only hope of future food supply, the leaves of all plants may be truly
likened to a factory the work of which is never ending, the product of
which the leaf will never use, but the result of which has far-reaching
consequences to us all.

EFFECT OF LIGHT AND DARKNESS ON INDIVIDUAL PLANTS AND VEGETATION AS A
WHOLE

Now that we understand the importance of light to all except a very few
plants, and its very close relationship to the green coloring matter of
all leaves, many things about the arrangement and position of leaves,
and indeed of the whole plant, may be understood, which, without this
knowledge, seems the result of mere caprice or chance. It would seem as
though the habit of plants growing toward the light, and against the
pull of gravity, a character almost universal, no matter from what
mountain declivity or rocky cliff it may spring, might be the result of
the “pull” exerted by light on the green coloring matter in the leaves.
While light does aid in plants having a generally erect habit it is not
the cause of it, as we have many times proved by experiments. As a seed
sprouts and the roots go down into the earth, the shoot, before it has
broken through the surface and while _still in the dark_, always grows
upward. This property of growing in two opposite directions at the same
time, the roots always with gravity and the shoot nearly always against
it, is known as _geotropism_. In the case of vines or other trailing
plants there is the same tendency exhibited, even though the plant is
not erect. We must think of geotropism as a growth habit of all plants,
not caused by light, for it has been shown to act in the dark, but of
the greatest advantage to all plants in their initial start toward the
light. If this were not the case, it may be imagined into what chaos the
vegetable world would be thrown. We are so accustomed to roots going
down and shoots going up that we are not apt to think of it as the
result of two antagonistic growth habits, the true cause of which is not
understood, the result of which is common knowledge. Geotropism is one
of those mysteries with which the book of nature is crowded, and merely
to describe it and realize its force is by no means to arrive at its
true inwardness.

But, quite independently of this peculiar growth habit, the stems and
often whole plants do show response to light and many times the
response, in its effects, cannot be distinguished from geotropism.
Perhaps the most homely illustration of this is the common house
geranium which, no matter how often it is turned, always grows toward
the window, and if not turned at all becomes hopelessly lopsided, with
the leaves all bending sharply toward the light. Trees growing on a
cliffside, while always growing upward, nearly always may be seen
bending away from the cliff where light is scarce and toward the
unobstructed light. The position of hundreds of twigs and branches on
any tree have been dictated by their exposure to light, and the habit of
practically all trees in the forest of being clear of branches for many
feet from the ground is another illustration of the profound effect of
light. In the latter case the taller the trees the farther from the
ground are the first branches, and in the big trees of California the
first branches are frequently over a hundred feet from the ground. In
their young stages all these trees were furnished with branches, the
leaves of which in their day performed their appointed tasks. But in the
strife and hurry of the crowns of the forest to overreach their
neighbors these lower branches, from the bottom upward, gradually die
off. So inexorable is the plant’s demand for light, that these lower
branches, in spite of being nearest the source of their food from the
roots, are doomed to be killed. Nature plays no favorites and these
lower branches, once the pride and support of the young tree, are
ruthlessly dropped off when they can no longer play the game. This
wholesale slaughter of lower branches in a forest, more complete than
any pruning by man could ever be, gives us, if the story of the factory
leaf has not already done so, some conception of the part played by
light in the plant world.

The shade of certain trees is so much denser than others that they have
been planted for this purpose, notably the horse-chestnut and Norway
maple. Foresters have long recognized this difference in trees and it
would be strange if nature had not taken advantage of it also. If
certain trees can still maintain themselves in the forest without
producing a dense crowd of leaves, such as the silver maple for
instance, they would have a decided advantage over a tree like the sugar
maple which casts a much denser shade. A walk through any forest will
show scores of examples of trees that live and produce seeds by virtue
of the fact, not that they demand all available light, as their more
vigorous neighbors do, but that by a compromise, by an almost diabolical
cunning, their light demands, and of course their leaf exposure, have
been cut down to a point where the tree can grow in a place impossible
for trees that lack this ability. It is, of course, not a trick which
any individual tree can perform at will. Rather is it a characteristic
found in all individuals of certain kinds, where the comparative
disadvantage of making less food and having less leaf exposure is more
than overcome by the enormous advantage of being able to fight their way
into a forest that would otherwise be impossible for them. We shall see,
in the chapter on Plant Distribution, how this peculiar response to
light has had effects of considerable significance upon forests,
particularly after forest fires, lumbering, or other disturbance of the
natural conditions. Trees in the forest, and the shrubs and herbs under
them are not the quiet stately things about which the poets are so fond
of singing. They are places, on the contrary, of intense warfare, and
perhaps some of the greatest casualties occur in the battle for light.

Leaves, as being the most directly involved in the matter of utmost
exposure to light, show the greatest amount of response to it, by their
shape sometimes, by their position nearly always, and very often by the
character of their leafstalks. In many herbs the first young leaves are
relatively short-stalked, while as the plant grows upward the lower
leaves are progressively longer stalked, which is a direct response to
the fact that the upper leaves take their full share of light, leaving
little or nothing for the lower ones. To avoid complete shading their
leafstalks are often many times the length of their more fortunately
placed neighbors above them. In those plants like the garden primrose or
common weedy plantain, which bear all their leaves in a close cluster or
rosette at the level of the ground, we see an almost fiendish cleverness
in their earlier and later habits of growth. When the leaves first
start, as they nearly always do among grasslike vegetation in which
these plants usually have to fight for a chance of life, the leaves grow
straight up, so that they may get above the level of the surrounding
grass. Once there, and the precious light an assured fact, they
gradually flatten out their leaves to form a rosette, of course cutting
off the light from the grass about them and killing it just as certainly
as though it were pulled up by the roots. Hundreds of different kinds of
plants do this, apparently with the utmost cruelty to their inoffensive
neighbors, with whom they start upon nearly equal terms in the race for
life. If they began at once to spread out their rosette while it was
still in its small spring state, the upward pointing grasses would
smother it, and as if in anticipation of this the leaves grow up with
the grass, only to flatten out when the proper time comes for them to
show their true colors.

Light not only affects leaves in their habits of growth but it actually
causes movements in some leaves which are as regular as clockwork. The
best known cases are those in the pea family and wood sorrels, all of
which bear compound leaves. During the day these leaflets are spread out
in the ordinary way and catch the light, but at sundown, as though this
were a quite useless exertion for the night, they fold up and the leaf
“goes to sleep.” On cloudy days they partly fold up, as if in
recognition of the fact that for their business of getting light it is
an off day; but also if the sun comes out they hurriedly expand their
leaflets. It is not yet certain whether these apparently intelligent
movements of leaves in relation to light are of any real advantage to
the plant as a whole or not. They are surely one of the most interesting
things to watch and may be seen in locust trees and wood sorrel any
night.

Just as we can have too much of a good thing, it is possible for plants
to have too much direct sunlight. In open spaces, where the struggle for
life centers not about the fight for light but over other matters, we
find leaves actually protecting themselves against too much exposure,
and by a variety of ingenious ways. The texture of the upper or lower
side, the kind of hair growing on their surface, and the number and size
of their pores, are the most usual ways of leaves arming themselves
against an oversupply of the one thing that their neighbors in the cool
forest fight to the death to obtain. There seems to be a fatality
against which plants, like ourselves, are nearly helpless. Their
attempts to overcome it, again like our own struggles against an
apparently overmastering fate, develop those characteristics that insure
survival to the fittest, death to the puny or unaccommodating.

We could hardly leave the subject of light and plants’ relation to it
without mentioning, perhaps, the most remarkable case of adaptation to
peculiar light conditions. All those aquatic plants that grow beneath
the surface of the water need and get much less light than ordinary land
plants. But from the island of Madagascar comes the lace leaf or water
yam, which grows in quiet pools that are mostly in the depths of the
tropical forest. Add to the dense shade cast upon the gloomy surface of
such ponds the amount of light naturally lost in its passage through the
water, and we get some notion of the singularly secluded home of this
aquatic plant. What, now, is nature’s response to these peculiar
conditions? How do the leaves of this well-shaded inhabitant of quiet
pools behave? Their leaves are about a foot long and three or four
inches wide, quite unnecessarily large for a submersed aquatic, but they
consist _wholly of veins_. There is no “meat” to the leaf, none of that
soft, green tissue so familiar in ordinary leaves. The conditions under
which it is doomed to live almost seem as if it recognized the futility
of having a broad expanse of the usually constituted leaf blade to
expose to a light which is not there. It is significant that this
skeletonized condition is permanent, the leaf functions much as ordinary
aquatic leaves do, but its network of quite naked veins almost seems a
mute protest against its fate. The delicate, lacelike “foliage” of this
aquatic adds a touch of beauty to one of the most curious plants in the
world.

2. HOW PLANTS GET THEIR FOOD AND WATER FROM THE EARTH

If we could stretch an apparently impervious membrane, like the inner
white skin just inside an eggshell, or a piece of parchment, and so form
a wall through the middle of a glass box, and then pour into one of the
compartments pure water and in the other a mixture of water and
molasses, a very curious result would follow within a comparatively
short period. We should find that presently there would be a gentle
filtering of the water through the membrane toward the molasses water,
and similar gentle current in the other direction. In other words,
fluids of different density, if separated by a membrane, tend to
equalize each other. This equalization may not be very rapid, and at
first it will be more speedy from the less dense to the more dense, but
eventually it will make the different fluids of a common density. This
purely mechanical property of the equalization of fluids separated by a
membrane is known as _osmosis_, and it is upon the possession of the
equipment necessary for this that roots depend for getting food and
water from the soil.

In our discussion of roots in Chapter I, we found that they end in very
fine subdivisions, which are themselves split up into practically
invisible root hairs. These root hairs are the only way that roots can
absorb the food and water in the soil, and they are able to do this
because they are provided with a membrane which permits osmosis to act
between the solution inside the root hair and the water in the soil. The
solution in the root hair is mostly a sugary liquid, some of that
surplus sugar made in the leaves, and it is denser than the soil water,
so there is apparently nothing to prevent an equalization of the liquids
on different sides of the membrane. If this actually happened, as it
would in the case of the simple experiment noted above, then roots would
exchange a fairly rich sugary liquid for a much more watery one, and we
should find that plants did not get their food from the soil, but really
have it drained away from them by osmosis. But nature has a cunning
device for stopping such robbery, which is prevented by the membranes of
root hairs being only permeable to the extent of letting water _in_, not
permeable enough to allow sugar to escape. As we have seen, osmosis is
a purely mechanical process which, if left to operate without
interference, would not aid but injure the plant. Surely, nothing with
which plants are provided is so important to them as this delicate
membrane of the root hairs which, while allowing osmosis to act in a
one-sided fashion, preserves to the plant the sugary liquid that alone
makes the absorption of soil water possible.

As root hairs are very much alive and work constantly, they must be
provided with air, without which no living thing can exist. And here,
again, it seems as though nature, with almost uncanny foresight, had
deliberately planned for this requirement of roots. And, in this case,
not by interfering with a physical process by an adjustment of plant
structure, but by the arrangement of soil particles and the way in which
water is found in all soils. Soil particles, even in the most compact
clay, do not fill _all_ the space occupied by the soil as a whole. There
are tiny air spaces all through the soil, which insures a constant
supply of fresh air. That is one reason why gardens are cultivated, to
see to it that plenty of fresh air is allowed to permeate the soil.
Around the finest soil particles there is always an almost incredibly
thin film of water, which is renewed as soon as it is lost by its
absorption by the root hairs or by evaporation. This renewal of the
water film is itself a mechanical process, called capillarity, best
illustrated by putting a few drops of water on a plate and placing on
them a lump of sugar. The water will spread all through the lump of
sugar in a few seconds and the capillarity that forces it up through the
lump is the same as sees to it that the tiny film of water surrounding
the finest soil particles is constantly renewed from the lower levels
of the soil.

Little do we dream, as we walk over the commonest weed, that buried at
its roots are these delicate arrangements for securing food and water.
Osmosis allowed to act so that the “exchange” of liquids is all to the
advantage of the plant, capillarity providing a constant water supply,
and the very piling together of the soil so contrived that the
life-giving air filters all through it--does it not seem as if all this
were, if not a deliberate plan, certainly a more perfect one than mere
man could have devised?

If you will turn back for a moment to the beginning of the description
of how plants get their food, you will find that in osmosis the weaker
liquid tends to permeate the denser one more rapidly than the denser one
does the weaker. As we have just seen, the sugary liquid in the root
hairs is denser than the soil water outside, and, furthermore, _none of
it is allowed to escape_. This comparatively greedy process of taking
everything and giving nothing results in a constant flow of soil water
into the root hairs. When the flow of liquids in osmosis is not at once
equalized, a gentle pressure is brought to bear to make them so. This is
what is called _osmotic pressure_, and it is this pressure that forces
the absorbed liquid through the roots and part way up the trunk of even
the tallest trees. While we have just said it is a gentle pressure, that
is true only in the case where the osmosis has free play, and the
pressure is stopped with the perfect mixing of the two liquids. But what
if they can never mix? What may not the accumulated osmotic pressure
amount to in such a one-sided process as goes on in root hairs with
everything coming in and nothing going out. Cut-off stems, with a
pressure gauge attached to them, indicate that in some plants the
pressure is from 60 up to 170 pounds!

Another result of this pressure is that it keeps leaves and the fleshy
stems of plants in their ordinary position. The actual solid part of
nearly all leaves is scarcely 5 per cent of their bulk and all the rest
is water. The constant pressure of this water from the roots is
sufficient to keep leaves comparatively stiff and rigid, how stiff is
quickly realized if the pressure stops and the leaf wilts or withers.
Sometimes this osmotic pressure, particularly during rainy weather,
becomes so great as to cause injury to the plant, the splitting of
tomatoes and occasionally of plums, being due to it. This osmotic
pressure, together with the extra pull given by the leaves, is
sufficient to account for the rise of water to the tops of the tallest
trees. The tallest trees in the world are certain kinds of blue gum in
Australia which frequently reach a height exceeding 300 feet. What the
combined osmotic pressure and leaf pull must be to carry such a heavy
thing as water to such a great height is easier to imagine than to
calculate.

The root hairs, then, by the process already described, absorb the water
from the soil, but plants can no more live on water alone than we can.
As we have seen, the membrane in the root hairs cannot allow the passage
of even the tiniest particle of solid matter. In fact the root hair
itself is so small that it can only be seen through the microscope, and
of course the membrane is smaller still. Plant foods, then, can never be
solids, but must always be such materials as can be dissolved in water.
The chief of these are chemical substances, such as lime, potash,
nitrogen, magnesium, phosphorus, sulphur, and iron. Hydrogen is also
necessary, but as this makes up half the composition of water, there is
a permanent supply of that provided by the soil water. These things make
up the great part of plant foods taken in through the roots, and it is
from these that leaves, by a process you already understand in its
essential details, manufacture sugar and starch.

But neither starch nor sugar, important as they are to the plant, and
absolutely necessary as they are to us, are the only things made by
plants. Leaves may well be called factories, but plants are themselves
the most wonderful chemical laboratories, beside which any built by man
are as play-things. For plants, by processes too complicated to be
explained here, work over their accumulation of starch and sugar,
recombine some of their constituents, and store up in various parts of
the plant the results, which are often such food ingredients as protein.
This is the really essential food substance in wheat, as it is in eggs
and meat. No chemist has ever succeeded in making a single scrap of it,
yet it is such an everyday occurrence in practically all plants that it,
with starch and sugar, forms the great food supply of the world. Not
protein alone, but all the amazing plant products like the oils from the
olive and the resin from pine, rubber, the drugs of plant origin, even
tobacco--all these and hundreds of others are made by plants from those
few simple foods absorbed through the roots, literally pumped up to the
leaves and there, under the magic of sunlight, combined and recombined,
worked over and changed utterly in their make-up. Nothing could be more
perfect than the marshaling of forces and contrivances to secure the
result; let there be even the least bungling, and for us the world
would cease to be worth fighting for.

Nor does the work of plants stop here. If it did, they would be not
unlike a commission merchant who had gathered from the four corners of
the earth a supply of eggs only to find he could not or more likely
would not sell them all at once, and yet had failed to provide himself
with proper storage. Plants, too, have times in their life when adequate
storage is necessary for them. So true is this that unless there is food
enough stored in seeds to give a start to seedlings before their own
roots begin to work, they would die almost at once. In seeds and in many
nearly dormant parts of plants these foods are stored away for future
use. The tubers of potatoes and all our root crops, like beet and
parsnip, are common examples of this. Even the manufacture of wood in
the trunks of trees is a storage appliance on the part of the plant, for
wood is just as much one of the food products of a plant as wheat or
rice.

3. BORROWING FROM THE LIVING AND ROBBING FROM THE DEAD

With such a beautifully perfected mechanism for getting food it might
seem as though all plants would be satisfied to lead that life of
independence for which they are so splendidly equipped. Some of them,
however, are like men in one respect: there seems to be no end to the
chase after getting something for nothing. Those that stand on their own
roots, get their food honestly, and take nothing for which they do not
make prodigal returns, make up the great bulk of the vegetation of the
earth. Their independence has dubbed them with the title

[Illustration: INDIAN PIPE. (_Monotropa uniflora_). A saprophytic plant
inhabiting rich woods in eastern North America. (_Courtesy of Brooklyn
Botanic Garden._)]

[Illustration: THE PARTRIDGE BERRY (_Mitchella repens_), a trailing vine
of northern forests. (_Courtesy of Brooklyn Botanic Garden._)]

[Illustration: RAFFLESIA. ONE OF THE STRANGEST PRODUCTS OF THE RAIN
FOREST. It consists only of a giant flower, the largest in the world,
which is attached directly to the roots or stems of relatives of the
grape, upon which it is parasitic. (_After Kerner and Oliver. Courtesy
of Brooklyn Botanic Garden._)]

autophytes_, literally solitary or self-providing plants, and this
thrifty mode of life is called _autophytic_. But a few kinds of plants,
actually many millions of individuals, have more devious ways of getting
their food and provide strong contrast to their sturdier associates.

These baser modes of life appear to have been rather insidiously
developed, as though there had been some hesitation at even the smallest
departure from the normal. Of course we must not forget that plants,
while living things, are never reasoning ones, and that good and evil
and all other qualities that are ascribed to plants are perfectly
foreign to them. Throughout this book, and in many others, the habits of
plants are spoken of as base, for instance, or good. What is actually
the fact is that nature works in truly marvelous ways, and to our
reasoning faculties these adjustments seem clothed with attributes they
do not really possess. But the description of them in the terms of our
everyday speech, the translation of their behavior into the current
conceptions of mankind, does so fix them in our minds that they cease to
be “just plants,” and we no longer put their habits in the category of
those interesting things that nearly everyone forgets.

One of the first signs of departure from the usual methods of getting
food is the association of certain minute organisms at the roots upon
which plants, otherwise autophytic, depend for aid in securing
nourishment. This characteristic is fairly common, notably in all the
plants of the pea family, such as peas, beans, locust trees, vetch,
clover, and hundreds of others. If the roots of any of these be
examined, it will be seen that attached to the smaller divisions of
them are small tubercles from the size of a pinhead to a pea, depending
on the kind. These tubercles or galls are caused by and infested with
bacteria, the smallest of all plants. The bacteria have the
extraordinary power of changing nitrogen into nitrates, which is the
only form in which nitrogen can be absorbed by roots. Not only do they
accomplish this, but excess nitrogen is stored in the roots by the same
agency. It is this fact that has resulted in the planting of vetch and
kindred plants for soil enrichment, as each year there is a residue of
nitrogen left in their roots and by so much they add plant food to the
soil. For hundreds of years farmers have done this, but only quite
recently have we known why they did so. The occurrence of bacteria or
microbes at the roots of plants is much more common than was formerly
supposed to be the case, and many other plants than those of the pea
family depend, at least in part, upon them in getting food from the
soil. While not wholly autophytic, such plants do make some return for
what they gain, as some of them at least pay dividends in extra
nitrogen, and all of them provide opportunity for the bacteria to live.
The latter play an important part in populating the soil, which is not
the comparatively sterile thing it appears to be. Actually it is
infested with organisms that play a mighty, if rather inconspicuous,
part in the work of preparing the soil for plant growth. These organisms
are so minute and the chemical nature of their work is so complicated
that merely to mention their existence must suffice here. This close
association of certain roots and bacteria, which, as we have seen, is of
mutual advantage, is known as _symbiosis_. It is really only a kind of
exchange, not unlike the storybook community that helped out by taking
in each other’s washing. Unlike that community the association between
the two works to the actual advantage of both, but the process is
undeniably a step away from those wholly autophytic plants which live
free and independent of such aid.

A much more gruesome habit of certain plants is their reliance for food
only upon the dead. In the Indian pipe, some kinds of shinleaf, and in
many other plants their roots and root hairs are changed or often nearly
lacking, and we find them growing only on the dead bodies of other
plants. One peculiarly repulsive characteristic of such plants is that
they secrete at their roots a substance that hastens the decay of the
dead, and, as if this were not rapid enough, there are associated with
them certain kinds of minute fungus organisms that also speed up
decomposition. Plants with this charming mode of life are known as
_saprophytes_, literally _sapros_, rotten, and _phytes_, plants. “Rotten
plants” they may be in their mode of life, but the pearly white stems
and flowers of the Indian pipe have a certain ghostly charm, an almost
statuesque beauty among the normal greenery of the gloomy dark woods in
which they always grow. It is not without significance that Indian pipe
bears no leaves, has none or almost none of the life-giving green
coloring matter which we have seen to be the almost priceless possession
of plants which lead a different, and perhaps a better life. The great
bulk of saprophytes bear no leaves, and some only partially wedded to
the habit appear to be midway between bearing normal green leaves and
bearing none, or much reduced ones that are quite unlike the busy
factories we know normal green leaves to be. Plants with this method of
getting their food, must of course grow in places where dead and
decaying vegetation is plentiful, and often as such soil is turned up
there may be noted a peculiar dank odor, suggestive not only of its
origin, but of the fact that these “rotten plants” make their home in
it. Some of our most beautiful orchids grow in this fashion, but even
there, in spite of flowers that for beauty of form are without rivals,
the plants have no green coloring matter in their leaves, which are
often reduced or even wanting altogether.

It might almost seem as if demoralization, so far as food habits are
concerned, had reached its lowest point in these plants that literally
rob the dead, but there are still lower depths to which certain plants
have been reduced. This consists of robbing the living, and such plants
are called _parasites_, a word perfectly familiar in other connections.
Parasitic plants have no roots, but attach themselves to the roots of
other plants, somewhat generously called _hosts_, from which they derive
their food. The best known case is the common Christmas mistletoe, and
the dodder (Figure 68), but there are hundreds of others. Nothing in all
the realm of plant life so perfectly fits the action to the word as
plants of this type, flourishing when the host flourishes, dying when it
dies. Producing flowers and seeds, and often, by an irony of fate,
perfectly green leaves, they are nevertheless the most debased of all
plants in their mode of life.

These successive steps in the degradation of food habits, are not always
the clean-cut things they might be inferred to be from the foregoing.
There are many intermediate stages; it may even prove to be the case
that some plants are wholly autophytic at certain stages of their life,
and slip partially into more devious practices at other stages. The
whole affair is not yet thoroughly understood and may well be the result
of competition, as it is quite conceivable that if the getting of food
in normal ways became difficult or impossible plants may have had to
resort to other methods.

[Illustration: FIG. 68.--THE DODDER

A leafless parasitic vine which steals its food from the plants to which
it is attached.]

4. WHAT PLANTS DO WITH WATER AND HOW THEY BREATHE

Some one has said that one day without water would make men liars, in
two days they become thieves, and after the third or fourth day they
would kill to get water. In the Army Records at Washington is a report
of one of our expeditions, which in chasing Indians got lost in a
desert, and in which the soldiers fought among themselves for even the
most repulsive liquids. It hardly needs these gruesome examples,
however, to confirm what everyone who has ever been mildly thirsty
knows, that water is an essential for all animals, and that to be
without it is to suffer torture. Air of the proper kind is just as
important, and because its absence or impurity causes more sudden agony
and a quicker death, the need of it is that much more acute. Plants rely
even more upon these two essentials of life, and in getting them they
behave in ways just as ruthless as do men who are suddenly deprived of
either of them.

As we have already seen in “How Plants Get Their Food and Water from the
Soil,” the water is the carrier of the food elements from the soil, but
water as such does much more for the plant than act as a carrier.
Osmotic pressure, a never-ending pump, keeps sending up a steady stream
of water to the limits of its power. In everything except trees it seems
fairly certain that this pressure is sufficient to drive water into the
remotest leaves. It finally reaches these tiny rooms in the leaf about
which we read in the account of Leaves as Factories. And just here a
very curious thing happens. Each room is, as we have seen, a very busy
place, crowded with all the necessary equipment to make sugar, and yet
there is still room for water which is just as necessary as the other
fittings; in fact so necessary is it that the whole interior of the room
is bathed in water. This irrigation system works so well that the walls
of the room literally bulge with the pressure of the water in them. If
they did not--a condition known as turgor--the plant would at once wilt,
and if no new supply came it would wither and die.

But water cannot stay in this condition of pressure and stagnation for
even a brief period. That would be as if a leaf were like a toy balloon
which, after inflation, had the entrance pinched and so remained
inflated. And while we have all along spoken of factories for making
sugar, and pressure pumps for forcing up food and water, it must never
be forgotten that this marvelously adjusted mechanism is a living thing.
Constantly growing, even producing their own means of falling in the
autumn, leaves must be thought of as living machines, just as we are
still more highly developed machines. In other words the accumulated
water in the cells of the leaf must be removed, after it has served its
use, and replaced by fresh supplies. The removal is carried on by its
evaporation into the halls, or, in the more precise terms of our account
of leaves as factories, into the _intercellular spaces_. It will be
recalled that these are connected with the outside air through the pores
or stoma. When the air outside is hot and dry it might easily suck out
by evaporation all the water vapor in these intercellular spaces and
wilting follow at once. This would actually happen if the guard cells,
already mentioned, were not constantly on the job. They control the size
of the opening just as certainly as a steam valve does, and maintain,
with a few exceptions, just the proper amount of water loss not only to
maintain turgor, but to see to it that transpiration, as this process is
called, goes on rapidly enough to insure fresh supplies of water being
sent to the leaf. The opening and closing of the stoma by the guard
cells is a nicely balanced operation dependent upon root pressure,
turgor, and atmospheric conditions. Guard cells have, because of this,
been much studied in spite of the fact of their microscopic size. We now
know that they allow greater openings during the night and reduce them
during the day. When we reflect that the constant removal of water in
the leaf, both as such, and as the only carrier of food supplies from
the roots, depends in such large measure upon the functioning of these
guard cells, then we come to some realization of their importance to the
plant.

They do not always work unaided, for in many places the transpiration,
even with their best efforts, would exceed the rise of water in the
plant and death must follow if such a condition exists for long. This
may be the case in certain bog plants, where, even with their roots in
the water, they actually are in danger of drying out because the
composition of bog water makes it partially unfit for most plants. And,
again, in very open dry or windy places, such as deserts or the mountain
tops above timber line, the actual supply of water may be insufficient.
Many plants growing in such places have their leaves, particularly the
under surfaces of them, clothed with various kinds of hairs. These may
be quite velvety or cottony, but in any event, either by their texture
or their color, they tend to reduce transpiration. An extreme case is a
desert plant from Arizona where the whole leaf surface is covered with
an ashy gray velvety coating, which, of course, absorbs less heat than a
normal green leaf, and in addition there are much fewer pores through
which transpiration could be carried on. In ever so many leaves nature
has provided them with a thick coating of hairs in early spring, which
they lose later in the summer. Shrubs and herbs, especially those that
start earlier than the trees under which they grow, very often may be
found with a dense woolly or silky covering in early spring. As the
shade becomes denser and the need of the protection less, the wool or
silk is shed, sometimes completely. Some of the most conspicuous cases
of this are certain kinds of our common shadbush, which in April are
covered with a beautiful grayish-white silky coat, but by August are
practically the ordinary green color of other leaves. The hairy covering
of leaves is well worth observation, as it may hide not a few facts
about transpiration and, in some leaves, has had much to do with their
preservation from grazing animals. Some, like the common mullein, are
never touched, and may be found standing like sentinels in fields
otherwise cropped short.

In many leaves there is conflict between those forces that result in the
leaf getting the utmost possible exposure to light and those that
prevent too rapid transpiration. On the one hand there is the absolute
necessity for light, on the other the ever-present danger that the
response of leaves to this necessity will result in a transpiration rate
too rapid to be held in check by the guard cells. The compromise between
these two forces, each pulling in opposite directions, gives to some
leaves a series of movements that are among the most interesting things
in nature. One of the most marked examples is the common wild lettuce, a
weedy plant of our roadsides introduced from Europe. In bright sunlight
the leaves are turned so that the edge of the blade faces upward, and
the surface is thus protected from the direct rays of the sun, but
during cloudy weather or in the shade the leaves turn into the ordinary
position of most foliage leaves. It is difficult to avoid the inference
that photosynthesis, which, as we have seen is an absolute necessity to
the leaf, is in the wild lettuce retarded by transpiration, to avoid the
too rapid rate of which the leaf is turned on edge. In this plant the
leaf base, as though to be ready for whatever change transpiration or
photosynthesis may demand, is so attached to the stem that such changes
are made with the least possible delay or wrenching. In one of the many
kinds of blue gum trees of Australia all the leaves turn one way in the
light, and another in shade or on cloudy days. Ever so many plants have
partial movements of their leaves, a good many of which are in response
to these opposing demands, one pulling the leaf into the greatest
possible light, the other holding it away from that condition. There are
other movements of leaves, of parts of the flower, or even of the whole
plant that are not so certainly the result of the conflict between light
requirements and the necessity of conserving water supply. They will be
considered presently.

While most plants are well provided with methods of losing water, so
well provided in fact that in very hot or very long dry periods it is a
common sight to see many plants literally panting for more water, there
are some apparently more cautious individuals, who reverse this process.
All throughout tropical America hundreds of relatives of the pineapple
have their leaves so formed and arranged that they catch and hold
considerable quantities of water. In one kind, called _Hohenbergia_, the
long leaves are joined together toward their base into a water-tight
funnel, which will hold a quart or two of water over a period of
drought. In Africa the extraordinary traveler’s-tree, a giant herb
growing twenty to thirty feet tall, has the overlapping leaf bases so
arranged that they hold many gallons of water. And we have already seen
how the giant cactus of our own Southwest will hold 125 gallons. The
most remarkable case is the Ibervillea from the deserts of Arizona. In
riding over this country one may find objects that look not unlike a
burned pudding, about two feet in diameter and nearly as high. From the
center comes a delicate stalk with the finest feathery foliage and tiny
flowers. Of roots there appear to be almost none, and these curious
objects, which are very hard and woody, might almost be taken for
stones. But they are actually plants not distantly related to squash and
pumpkin, and one of them collected years ago and brought into a museum
behaved in quite the most thrifty fashion of any plant yet discovered.
It was carefully cleaned and put in a museum case and locked up as a
curiosity for the wondering public to gaze at. But suddenly, almost
miraculously, it sent out its delicate growth which grew its appointed
time and then withered. Imagine the astonishment of the curators of this
museum to find it doing the same thing the next year, and the next.
Finally after putting forth its shoot for five years it actually died
and is now a peaceful museum specimen. No other such case of water
storage is known, but thousands of plants have this remarkable ability
to a less degree, all in response to conditions that would mean
destruction to plants not so providently equipped.

This conservation of water on such a great scale offers striking
contrast to the truly prodigal habits of certain plants that actually
drip water, so charged are they with this precious liquid, and so little
stress do their conditions of life put them under in this respect. Where
water is plentiful and turgor maintained almost to the bursting point,
evaporation in a moist or chilly atmosphere does not suck out water
vapor fast enough. Sometimes, around the edges of the leaves of the
common garden nasturtium, drops of water may be found, literally forced
out as drops, rather than transpired as water vapor. This happens to a
considerable number of plants, during the night when transpiration is
laggard, and such drops are usually mistaken for dew. The latter is
actually the condensation of moisture in the air upon the leaves of
plants which cool down more rapidly than the air, and seldom due to the
forcing out of drops of water from leaves, although in rare cases it may
be. In tropical forests, where the humidity is very heavy and water
supply from the roots copious, certain leaves leak water so fast and are
so constructed that this excess is prevented from accumulating on the
leaf. The pipal tree of India has long drip tips to its leaves that
conduct the excess water from the blade to the end of the slender tip
where it drips off. The advantage of these dripping points is obvious,
for in regions so humid that water is forced out of the leaf, the
coating of the leaf with this extra moisture would by that much retard
transpiration. Dripping points, which in less exaggerated forms than in
the pipal tree are common in many parts of the world, are thus of
decided advantage.

Whether it be desirous to retain water or to lose it by gradual
evaporation, or expel an excess of it, each species of plant has
developed the apparatus to best preserve its individual life. While only
the barest outline of these adjustments to the water requirements of
plants has been given here, the details form an almost dramatic picture
of struggle of the different kinds of plants for survival. The extremes
are the desert plants on the one hand and those of the rain forests in
the tropics on the other. The chapter on Plant Distribution will show
how important these water requirements of plants have been in
determining what grows on the earth to-day.

With carbon dioxide going in, oxygen, water vapor and, as we have seen,
even liquid water coming out of the stoma of leaves, it might be
surmised that these busy little pores and their guard cells had done
work enough for the plant. And yet there is still one more act to play
and the stoma have much to do with it. For this process of
photosynthesis and the closely related one of supplying food and water
to the leaf cannot go on without respiration, which is quite another
thing. In plants respiration or breathing has no more to do with
digestion than it does in man. Digestion in man is not unlike
photosynthesis in plants, except that plants make food in the process
while men destroy it. But plants must breathe just as we do, and, as we
need oxygen to renew our vital processes, so do they. While respiration
is a necessary part of plant activity it is not such an important part
as photosynthesis, for which it is often mistaken. The thing to fix in
our minds is that photosynthesis makes food, uses the sun’s energy and
releases oxygen in the process, while respiration uses oxygen and might
almost be likened to the oil of a machine--necessary but producing
nothing.

5. RESTLESS AND IRRITABLE PLANTS

In walking through the quiet cathedrallike stillness of a deep forest or
over the fields and moors, perhaps our chief thought is how restful the
scene is, and what a contrast the quiet, patient plants make to the
darting insects or flitting birds that our walk disturbs. We found at
the beginning of this book that ability to get about is one of the main
differences between animals and plants. Like so many first thoughts,
this is, however, only a half truth, for while most plants, seemingly by
a kind of fatality, are anchored forever to the place of their birth,
many of them do move certain parts of themselves and that quite
regularly. While some of these movements have already been hinted at as
a possible response to transpiration or too intense light, there are
others where the advantage to the plant, if any, has yet to be
demonstrated. These other movements, perhaps because their cause has
never been discovered, seem the more mysterious as they certainly are
more weird and interesting than almost any other of the curious things
that plants do.

Perhaps the most difficult thing in the world is to keep an active
growing child perfectly still for more than a few moments at a time.
There seems to be some impelling force that makes young growing things
in a constant state of restlessness, and it is perhaps not so
extraordinary, after all, that practically all young plants are restless
in the sense that they are never quite still. And, like many grown-up
people who do not know what repose in their waking moments really means,
there are a goodly number of plants that are restless until the day they
die.

Charles Darwin, perhaps the greatest man that the last century produced,
wrote a book in two volumes on these restless plants, and proved by a
series of experiments illustrated by charts which the plants themselves
drew for him, that there were perhaps no plants that do not move at
least some part of themselves during the early stages of their career.
While he never could explain the cause of these movements he left in
that book an imperishable record of the amount and direction of these
mysterious movements, which are almost to be likened to the growing
pains of young children.

The tips or growing shoots of many plants will point in one direction in
the early morning, a different way at noon and still a different one by
nightfall. Hundreds of totally unrelated plants seem to have this habit
of moving their tips through a definite cycle during each day and this
restlessness does not appear to be of the slightest use to them. It
cannot be response to the moving of the sun through the sky, for often
the movement may be away from the direct sunshine, and sometimes the
motion goes on in the dark, as experiments have proved.

It is hard to see the movement of the whole upper part of a plant,
although it is well known that they do move in many cases. But in the
tendrils the movement is often easy to observe and even to induce. Some
of these slender aids to climbing plants, if they happen to be swinging
freely in the air, do actually make slow circular movements, that even
if they were designed for the purpose could not more perfectly
accomplish their obvious intent, which is to catch the nearest favorable
support. These circular movements are to the left in the hop,
honeysuckle and many other plants, to the right in the climbing beans,
morning-glory and some others. When the tendril reaches a support it
almost immediately turns about it, in the same direction as its free
movements through the air have been. It is thus this apparently aimless
swinging of tendrils through space that determines whether the vine is
going to twine to the right or left. The speed with which a tendril will
take its first turns about a support is so comparatively rapid that,
once the support is caught there is scarcely a chance of the vine being
torn away by the wind or other agency as would surely happen if tendril
movements were the leisurely things that some folks think they are. In
the case of one Passion-flower vine, which are gorgeous climbers mostly
from the tropics, the tendril made a complete turn in two minutes after
it first touched a possible support. And there is a quite noticeable
movement in thirty seconds if the tip of the tendril be ever so lightly
touched. Teasing tendrils to see how much or how fast they will coil has
resulted in some extraordinary cases of the “comeback” of some of them.
Darwin irritated a tendril for a few moments and induced a partial
coiling which straightened out when the object causing it was withdrawn.
To see how long the plant would stand this sort of thing and still not
be literally tired of coiling he succeeded in making the plant partially
coil, and by withdrawing the incentive uncoil again, over twenty times
in fifty-four hours. An impulse to coil of such persistence as this
naturally results in vines forming the impenetrable thickets they do in
many forests. It emphasizes how restless are the growing points of these
climbers, and serves as a striking illustration of those gradual
movements of many other plants that seem to have some relation to
growth, but in a way not yet understood. For while it is an obvious
advantage for the vine to swing its tendrils through the air this
advantage has not yet been proved the cause of the swinging. In fact if
all possible supports are removed the tendril will often coil anyway, a
perfectly futile proceeding, that looks almost like disgust.

This general restlessness, which by the imaginative has been thought of
as a mild protest by plants at their otherwise fixed position, is not so
spectacular as that of certain other plants, notably the poplars. A
flattened instead of a round leafstalk makes the leaves of these trees
flutter in the lightest air and in a gale the tree is a mass of animated
foliage. No use has ever been found for this curious habit and it is not
certain that it is of the least advantage to the tree. If anything, the
constant movement may have the decided disadvantage of increasing
transpiration.

In our common wood sorrel the leaflets on cloudy days or during the
night regularly “go to sleep.” That is, they are folded at such times,
rather than spread out in the ordinary way. These sleep movements may
have something to do with transpiration, but whether or not this is true
they are very regular and in certain plants the habit is remarkably and
rather mysteriously uniform. Why, for instance, do the leaflets of these
wood sorrels, the beans, lupine, locust tree and licorice plant, always
fold downward while the clovers, vetch, peas, and bird’s-foot trefoil
are always folded upward? Such movements and their direction are among
the unsolved problems of botany, and merely to know of them or observe
them leads us nowhere as to their true inwardness.

But quite apart from these merely restless plants, and there are
thousands of different kinds which are known to move slightly, at least
during their young stages, are a few more decidedly active ones that are
seemingly irritable. At least they show peculiar movements if touched,
and at night. One of the best known is the sensitive plant from tropical
America. Its twice compound leaf is composed of many tiny leaflets
which upon the slightest touch close up and apparently wither on their
stalk at once. In five seconds after the leaf is touched it will appear
like a wilted wreck. If the jar is sharp enough the whole plant will
droop, and the response to a sudden jar is almost electrically quick in
its action. And yet all this sudden wilting, actually caused by a quick
loss of turgor, is slowly repaired and the plant carries on quite
normally again until another shock renews its irritable response. This
plant does the same thing gradually during the night, except that the
leaflets recover their normal position only with the rise of the sun.

From India comes the most remarkable of all plants so far as movements
are concerned. For in the telegraph plant the movements are so regular
and long continued that irritability might almost be said to be
continuous. The plant is a low shrub or herb with compound leaves, and
the terminal leaflet, which is much larger than its neighbors on either
side of their common stalk, performs a motion that describes with its
tip an irregular oval or ellipse. But the movement is not steady; it
goes by a series of slight but perfectly distinct jerks. It takes about
two minutes for the leaf to complete its cycle, and it is this jerky
movement that has given the plant its name. During the night its
leaflets stop this apparently quite useless performance, the cause of
which is quite unknown. It is often grown in greenhouse collections
where its strange movements may be seen on any sunny day.

Many other cases of the restlessness or irritability of plants could be
given, and nothing has been said here of the curious movements of some
insectivorous plants as they have already been mentioned. The very
considerable movements of certain flower and fruit organs will also be
considered elsewhere.

* * * * *

It cannot have escaped the thoughtful reader that all of this chapter on
plant behavior has dealt with those functions of plants in which roots,
stems, or leaves play the chief part. These purely vegetative actions of
plants, what might almost be called their bread and butter activities,
would never lead to perpetuating their kind. For while all of these
functions are necessary, except certain apparently wayward movements
which still remain unexplained, they are in a sense only the preparation
for an infinitely more important act, the reproduction of their kind.
What the poetic have called the love of the flowers, or in more prosaic
but perhaps more truthful words the fertilization, pregnancy, and birth
of the new race, will be considered in a separate chapter. No other act
of the plant world is so interesting as the mechanism of reproduction,
the almost endless devices for securing it, and the ingenuity of nature
in seeing to it that there are no flukes.

CHAPTER III

HOW PLANTS PRODUCE THEIR YOUNG

There is perhaps no device of nature that more perfectly accomplishes
its purpose than the one with which all living things are endowed--the
instinct for the renewal of life. In man the dawn of the mating instinct
has ever been the theme of poets, and some of its manifestations are the
despair of ascetics. Through it some of the noblest of man’s emotions
have arisen, and because of its perversion our daily newspapers
chronicle the basest and most sordid tragedies.

But whether noble or ignoble, this instinct for mating is, in its
simplest terms, only a provision of nature that all life contains within
itself the means of renewing life. Without this, life, so far as we know
it, would end with the present generation. Perhaps our understanding of
this decree of an all-wise nature to increase and multiply will be
heightened by looking at it not only from its familiar manifestations in
man, but more broadly. Seen from this broader viewpoint, it is the
inherent legacy of all living things from the dawn of life on the earth
down to the present. Even the simplest one-celled organisms have the
faculty of increasing. In all plants, both the flowerless ones and those
producing flowers, the process is carried to a perfection almost
unbelievable in its intricacy and in provisions against its failure.
From the matings of flowers much may be gleaned; even man himself can
learn from them the capacity for sacrifice, the sinking of individual
aims and pleasures in the greater scheme of conforming to that necessity
for renewal of the race upon which all progress must be based.

The equipment which different flowers have developed for this purpose,
their almost uncanny devices to make certain that only the distant and
foreign male can ever impregnate the female, the enormous wastage of
both unfertilized females and males that will never become fathers, and
the overwhelming effectiveness of it all, in spite of this
prodigality--these manifestations of the production of young in the
plant world will take up the rest of this chapter. All the first part
will tell of this process in flowering plants, while the second shows
how flowerless plants accomplish the same end in more secret ways.
Finally, in a brief third part, we shall see how, without mating of the
sexes, nature has still one other way to see to it that there is a
constant supply of young.

We have already made clear that all plants are divided upon the basis of
whether they bear flowers and their mating goes on before the world, or
whether they bear none and the process is accomplished in more secret
ways. Because flowers are so much better known, and it is simpler to see
how the act is consummated in them than in the _cryptogamous plants_, we
shall first consider the _phanerogams_ or flowering plants, and in the
second section of this chapter the _cryptogams_ or flowerless plants.

1. VISIBLE MARRIAGE OF FLOWERING PLANTS

In the first chapter, under the section devoted to flowers, we found
that the stamens are the male and the pistils the female organs of
reproduction. As the period for mating draws near there is developed in
the _anther_, which is the enlarged tip of the stamen, a fine, usually
yellow, powder known as _pollen_. This matures in the anther, and when
ripe is discharged from tiny pores.

Pollen is made up of individual _pollen grains_, which are very often
stuck together so that we see only the mass, not the individual pollen
grain. Sometimes the pollen is not sticky, as in the case of pine trees
or in the ragweed--a fertile cause of hay fever. In these, and hundreds
of other plants, the wind will blow great clouds of pollen through the
air. When we stop to consider that a single, or at most a very few
pollen grains are all that are necessary--in fact, are all that _can_ be
of real service--the enormous wastage of the male fertilizing substance,
in order that mating be secured, gives us some idea of how prodigal is
nature in this supreme function.

The pistil, or female organ of reproduction, is more cautious in the
expenditure of its resources. As we have seen, it is composed of a
swollen base, the _ovary_, a slender shank, the _style_, and a swollen
or branched tip, the _stigma_. In some plants the ovary is divided into
several compartments or cells, each with one or more _ovules_, which are
only immature or unfertilized seeds, often very tiny, but usually quite
easily seen if the ovary is cut open. It is the entrance of the pollen
grain into this ovule that consummates the act of fertilization. As the
ovule is carefully secreted within the ovary of the flower, and as the
male fertilizing stuff or pollen is found only on the anther, it is
obvious that some method of bringing the two together must be provided
for.

In some plants this is accomplished by the anthers being just above the
stigma, and when the pollen is ripe and the ovule ready, the stigma is
found to be covered with a sticky substance. As the falling pollen
grains touch the stigma, they are caught in this sticky substance just
as surely as flies are caught once they touch a fly paper. But just here
one of the most wonderful processes of nature begins. The pollen grain
begins, slowly at first, to grow, and in the act it penetrates the outer
coat of the stigma with a minute _pollen tube_. This slender threadlike
tube, carrying with it the male germ, grows straight down through the
stigma, into the narrowed style, and through this to the ovule. Once the
pollen is caught on the stigma, nothing is so sure of fulfillment as
that this male fertilizing stuff will ultimately reach the ovule. For
the hitherto virgin ovule this impregnation starts a new phase in life.
It means the beginning of the end, but in the process fruit and seed
will be developed, and the young bride, already a mother, has
triumphantly accomplished that for which she exists.

If fertilization of all flowers were as simple as this, there would be
no need of what follows, but actually in surprisingly few plants are the
stamens and pistils so arranged, the ripening of the pollen and
readiness of the ovule for impregnation so timed that the act can be
accomplished in such direct fashion. For it is quite obvious that in
flowers in which the whole drama of mating goes on within the petals,
without the interference or help of any outside agency, the result will
be a crop of young who know no other characters than those of the
parents, and have nothing to look forward to but a closely inbreeding
progeny, very little, if at all different from themselves. In other
words, such plants are pure bred, they lack the usually obvious virility
that comes from crossing the male of one plant with the female of
another. There are so many devices to prevent self-fertilization in
flowers, so marvelous are the contrivances to see to it that only
cross-fertilization can be effective, and, finally, the experience of
breeders that strength and virility often or usually result from
impregnating the ovules of one plant with the pollen of another, that we
are forced to the conclusion that absolute purity in the sexual
relations of flowers is rare indeed. It occurs, without peradventure of
a doubt, only in those flowers whose petals never open and where
fertilization is consummated, if not in private, at any rate without
external help. In many violets the showy violet blossoms are often
nearly infertile, while down near the ground are inconspicuous flowers
which never open, but within which fertilization is so successful that
the crop of seeds is far more plentiful than in the more showy ones that
most people think are the only flowers ever borne by violets. These
flowers that never open, or at any rate open so slightly that their
sexual processes are modestly completed without intrusion, are known as
_cleistogamous_ flowers (Figure 69). They have been found in a few
plants, but overwhelmingly the greater number of flowers not only do,
but must, rely on some outside agency to insure fertilization.

Certain structural features of flowers have been so developed that
fertilization of the ovary by the pollen of the same flower is
impossible. The commonest case is in those flowers where the stamens are
shorter than the pistils, as they always are in the common snowdrop,
hyacinth, the sassafras tree, and in hundreds of others. There can be
no consummation of the reproductive process in such flowers without some
outside aid. More futile still without this aid are those flowers where
the stamens are well above the pistils, but the time of maturing in both
differs by a few days or even hours. Nothing could be more
helpless than the pistil under these circumstances, for if
its instinct for maternity were ever so strong, it would be doomed to
barren sterility by the premature development of the males. Sometimes,
too, the female is prematurely ripe for impregnation, and the stamens
lag behind a day or two. Her time passes and with it her only chance of
fertilization--by her own haste she has rendered impotent the now
useless pollen which appears doomed to fall aimlessly upon the
unreceptive stigma.

[Illustration: FIG. 69--THE VIOLET

Note the showy, often partly infertile upper flowers and the much
smaller cleistogamous ones at the base, which never open and yet produce
a good crop of seeds.]

But, perhaps, the most hopeless of all is the well-known partridge
berry, whose red berries are common in the woods during August and
September. This seems as though it fought off any chance of securing a
mate by a flower structure and behavior that would certainly so result
if some way out of the difficulty were not at hand. The partridge berry
bears two kinds of flowers that outwardly look much alike, but whose
sexual organs differ in this way: in some flowers the stamens are all
shorter than the pistil, and in others the pistil is much outtopped by
the stamens. The extraordinary feature of it is not so much this
structural difference, however, but the fact that pollen from the
short-stamened flower is useful only to its neighboring short-styled
relative, while the pollen from this long-stamened but short-styled
neighbor is nearly useless where it is found and really useful only on
the long-styled plant. By this device, but again only with outside aid,
this plant does not prevent maternity, but increases its chances of
being fruitful, for, as we have already seen, cross-fertilization
appears to be the rule rather than the exception, and the partridge
berry not only needs it, but can exist only when its offspring are the
result of such crosses.

In all those plants that bear the different sexes in different flowers
on the same plant, as in the hickory, or even on different plants, as in
the willow, there must, of course, be some method arranged for
cross-fertilization or they would promptly die out. So general is this
cross-fertilization, so much a part of the economy of nature does it
appear to be, that we can only think that there must be in the
production of this vast horde of the cross-fertilized some advantage.
Besides securing greater virility, which almost certainly results from
this promiscuity, greater variability is promoted. If virility is the
result, the price paid for it is tremendous, for the hindrances to
self-fertilization are so many and so effective that most flowers would
inevitably die as perfectly pure but ineffectual virgins if that
fatality were not prevented. How they are saved from such a sterile
fate, how they finally secure a mate by devices that outshine the most
bewitching tricks of the daughters of Eve, is one of the most
fascinating stories in all the history of the plant world.

For, of course, flowers do secure a mate, and they are aided in this
enterprise by the most formidable array of helpers, one might almost
call them conspirators. The chief of these are insects, thousands of
different kinds of which are constant flower visitors. Some of the
smaller birds, and even snails, also help flowers to meet their mates.
The wind, too, bears pollen through the air to some expectant
bride-to-be. And, finally, in the water, by a series of acts the like of
which no one could improve for cunning, the cross-fertilization of
certain aquatic plants is consummated. It would take a book larger than
the present one to give even the briefest account of how these different
aids to maternity do their work and how the flower responds to this
help. As that is quite out of the question, only some of the best-known
examples of cross-fertilization will be given, and these will be grouped
according to what agency the flower is indebted for its chance of doing
that for which it is created.

INSECTS AS FLOWER VISITORS

On any summer day, especially when the sun is shining brightly, we may
see bees and butterflies flitting from flower to flower, busy as the
proverbial bee. We already know enough about nature’s ways of doing
things to be certain that these, and hundreds of other kinds of insects,
do not come for nothing, and that the flower must have something to
offer. Bees, especially, are thrifty creatures whose business demands
exacting and prolonged toil. They would not waste five seconds upon idle
flower calling if the blossoms did not yield a rich store. And thousands
of flowers do yield the sweetest and richest kinds of stores of nectar
or honey, which is, in fact, by the help of insects who alone can
extract it, our sole source of honey. Many flowers which produce no
nectar do have such plentiful stocks of pollen that the bees come for
that alone. In the peony, for instance, over three million pollen grains
are produced in each flower, only a minute fraction of which can ever
fertilize an ovule. All the rest would be wasted were not pollen in
itself a particularly nutritious food for young bees, and consequently
much sought after by the careful bee mothers. They are the only insects
that feed their young on pollen, or beebread, as it is called by the
beekeepers, so that the enormous overproduction of this male fertilizing
agent, from the point of view of the flower, is a decided attraction,
one might almost call it a trap, to insure constant visitations from
bees. For they are perhaps the most useful of all insects in the great
game of securing cross-fertilization, as we shall presently see. Many
other kinds of adult insects eat pollen directly and so add to the
number of insect visitors.

No one has ever been able to explain the beautiful coloring of flowers,
except that it serves as an attraction for insects and small birds. Like
the honey or nectar, it seems to play no real part in the home economy
of the flower, to be of not the least use otherwise. While honey and the
gorgeous colors of flowers are a delight to man, that would be no
sufficient reason for the ability to produce them. Both of these
attributes of flowers, as attractions for insect visitors, are, however,
so absolutely essential to cross-fertilization that we must think of
them as having grown up out of that demand. As we shall see a little
later, even the structure of some insects has been modified so that they
can reach the nectar or pollen only by automatically doing for the
flower what it cannot do itself.

While color of flowers seems as though it were attraction enough, it is
very likely that their fragrance or perfume is still more seductive in
its power of luring insect visitors and repelling useless ones. Poets
have called this perfume the soul of the flower, and in its almost
intangible beauty it might well be so called were it not for the fact
that it appears to be of not the slightest use, except as a lure. In all
the equipment of seduction there is none like this fragrance of flowers
for attracting insects.

Flowers, then, have things to offer to insects which the latter need.
Nectar and pollen are the chief, and where these merely bread and butter
objects are not enough, or sometimes in addition to them, the flower is
dressed out in gorgeous colors or perfumed with a fragrance beyond the
dreams of the fairest bride. What insects do to complete the
fertilization of such a legion of beauties makes up the romance of the
flowers. Perhaps not even in man himself is this creation of new life so
surrounded with beautiful ideas. Also, as in man, it sometimes is bound
up with an almost fiendish cruelty and cunning. Some of these visitors
and what they do, but unfortunately only a very few, can be mentioned
here. They must serve as types or examples of what is going on all about
us on any summer day.

The common blue columbine, much grown in gardens for its beautiful
blossoms, always has the flowers hanging upside down, a habit that
admirably serves to keep its pollen from rain. The opening and closing
of many flowers in cloudy weather, or at night, may be for the same
reason. Everyone knows the five blue spurs into which the petals of
columbine are produced. At the very end of each spur, which is always
curved, the flower secretes a considerable quantity of honey. This, one
of the greatest attractions to bees, leads inevitably to a visit from
one. The bee, in order to reach the honey, hangs on to the inverted
flowers, clutching the base of the spur with its foreleg, and further
securing itself by the mid or hind legs, which grasp the slender column
into which, in the columbine, the stamens and pistils are crowded. In
its anxiety to reach the honey the bee pokes its head as far into the
spur as possible, but it gets in only a fraction of the full length of
the tube. To reach the honey it extends its sucking apparatus, which is
a complicated mechanism for this purpose on the head of nearly all
insects, and which will hereafter be called by its true name of
_proboscis_. It happens that bees can easily bend the proboscis downward
or toward their own body, but only with considerable difficulty can they
bend it in the opposite way. And yet the honey in the curved tip of the
columbine can _only_ be reached by curving the proboscis to fit the
tube, and in this process the bee’s body for nearly half its length is
forced to touch the anthers. While these are close to the stigma, they
produce pollen only on their outside surface, where it is, of course,
scarcely likely to reach the stigma, but must be brushed off by the
contortions of the bee’s body in reaching the honey. The hairy body of
the bee, coated with pollen, goes next to perhaps an older flower of the
columbine. Heedless of any change in the flower the bee goes straight
for the honey in one of the spurs, again catches hold of the only
available support in the center of the flower. But this time, instead of
brushing pollen off the exposed anthers, it brushes it off its own body
to the stigmas, which, at a slightly later stage than in the one just
described, are branched and perfectly adapted for collecting the pollen
with which the bepowdered bee can hardly avoid dusting them.
Cross-fertilization is of course assured, but it seems a precarious
business at best, as the number of bees with a proboscis long enough to
do the work is limited. The columbine, by a kind of uncanny foresight,
is so constructed that bees or other insects that try to reach the honey
and are not provided with a sufficiently long proboscis, nevertheless in
further attempts upon other flowers, inevitably cross-fertilize them
without reaping their reward. One or two kinds of bees, as though in
retaliation for this subterfuge of the columbine, make short work of the
honey by biting a hole in the spur and forthwith sucking out the honey
without so much as touching anther, pollen, or stigma. The reply of the
columbine to this ravaging of its chief attraction is that finally, as a
last resort, and by a new movement of its reproductive organs, it is
self-fertilized. Here the shape of the flower, the original position of
the pistil and anthers, the exposure of pollen only in such a direction
that, while a chance of cross-fertilization still exists, it can hardly
ever fertilize its own stigmas, all point to cross-fertilization as the
plant’s greatest requirement. And yet failing this, it falls back on
self-fertilization rather than endure barren sterility.

[Illustration: FIG. 70.--COMMON BARBERRY

The stamens of this, two at a time, drive off bees by sharp blows, thus
preventing self-fertilization.]

While the columbine by its spurs and other interior structure succeeds
nearly always in holding a bee long enough to insure its being dusted
with pollen, the common barberry bush of Europe (Figure 70), also much
planted in American gardens for ornament, actually drives bees away by
sharp blows of its stamens, so that self-fertilization shall not result
from the visit. In this shrub the petals partly cover the stamens unless
the latter are disturbed, and, in fact, the curved tip of the petals
forms a kind of socket into which each of the six stamens are fitted.
The position of these is such that any insect

[Illustration: PLANTS OF THE PALM FAMILY, _Palmaceæ_, in Ceylon. They
are the talipot palm (_Corypha umbraculifera_), the fiber from the wood
of which is used in India for paper making. (_After Reinhardt. Courtesy
of Brooklyn Botanic Garden._)]

[Illustration: A GIANT HERB OF THE BANANA FAMILY, _Musaceæ_. It is the
travelers’ tree (_Ravenala Madagascariensis_), the sheathing leafstalks
of which hold considerable quantities of water--hence the name. Grown
throughout the tropical world. (_Courtesy of Brooklyn Botanic
Garden._)]

can go straight to the honey glands which are at the base of the flower,
without touching the anthers. But their filaments are broadened out at
the base, so much so that their edges touch. The honey glands are so
placed that the insect must touch the broad bases of at least two
filaments, between which, in fact, it must force its proboscis in order
to reach the honey. The moment any particular pair of filaments are
irritated by the bee, two pollen-dusted stamens fly out from their
position among the petals and the anthers strike the bee with a sharp
blow. Many observations prove that almost never does the bee go on with
his honey sucking after this rude interruption, which has resulted in at
least its head being dusted with pollen. The low, sticky stigma is so
placed that it is one of the first things the bee’s head strikes as it
reaches the center of the flower. Because of the position of the
stamens, while they are undisturbed, it is impossible that pollen from
them could have been brushed off at the bee’s entrance of the flower.
And by an almost miraculous adjustment of the power of the blow by the
irritated stamens, this drives off the intruder only after he has
brushed his pollen-laden head over the stigma. His head at this stage
is, of course, covered only with foreign pollen gathered elsewhere, but
just as soon as the bee tries to get what he came for, sometimes even
before he gets his reward, out fly the pair of stamens, thoroughly
dusting the bee, and seeing to it that the blow is just sufficient to
drive off the pollen-laden insect. No device to secure
cross-fertilization could be more effective. If the blow of the stamen
were only ever such a slight fraction less than it is, the bee would
only stop a moment and then go on honey sucking; which, because of the
release of the pollen by even the gentlest blow, would result in
self-fertilization by the aid of the bee, rather than
cross-fertilization. Very few, if any, bees will stand this gentle
reminder to go, however, and it is a little curious that such
intelligent creatures as they are supposed to be, should not realize
that it is all the clever but quite harmless trick of an apparently
still more intelligent flower to secure fertilization from any pollen
but its own.

To attract insects and then repel them seems a little like using them as
some flirts notoriously use men, only to throw them over when they are
no longer interesting. In the large-flowered magnolia tree from the
southeastern United States, insects, however, fare somewhat better than
this. In this magnolia, which has flowers several inches long,
self-fertilization is impossible as the stigmas are ready to receive a
mate several days before the laggard stamens are provided with the
wherewithal. Without some insect or other outside help there would be
only a childless old age for this particular tree. The flower opens
rather early in the season, while the nights are still cool, and as a
protection from the cold, rose beetles habitually fly into them. They
find a pleasant shelter under the three inner petals which arch over the
honey-coated stigma, and form a snug little chamber so much warmer than
the outer air that its heat is appreciable to the touch. The rose
beetles, once they are inside this warm shelter, cannot get out and are
often held for a few days. Then, as the stigma passes its period and the
stamens are furnished with pollen, the chamber opens by the gradual
withering of the petals. But the insects, in their efforts to get out,
have raised a perfect dust storm of pollen with which they are
naturally covered. Just as soon as they are released they are free to
seek another warm shelter where the process is repeated. Thus they
always enter the flower with foreign pollen, use it up impregnating the
waiting ovule, and are held until the flower’s own pollen gives the
signal for their release properly dusted for a renewal of the work. The
premature timing of the stigma, the tardiness of the anther in producing
pollen, the generation of heat and secretion of honey which frequently
covers the whole stigma--there could scarcely be a better equipment for
securing cross-fertilization. And without it the magnolia would be
simply sterile.

There are some other flowers that hold visiting insects in a trap until
cross-fertilization has been completed, and all of them by no means
furnish their visitors such a snug little heated chamber as the
magnolia. One vine from the eastern United States, known as the
Dutchman’s-pipe, or sometimes as the pipevine (Figure 71), is singularly
ruthless in this respect. Its flowers are of such evil odor that only
carrion-loving insects, such as certain kinds of flies and gnats, ever
visit them. The flower is of very peculiar structure, being formed of a
hollow tube bent from its stalk first downward, and then upward. The
upper part ends at the opening which is provided with a three-lobed lip
or doorway. Through this the insects crawl, and they finally reach the
bottom of the curved part of the flower. Behind and above them is the
entrance through which they have just come. And above them, in the other
curved part of the flower, is the stigma. As in the magnolia, this
matures several days before the pollen from its surrounding stamens is
ripe, so that self-fertilization is never possible. What is now the

[Illustration: FIG. 71.--THE DUTCHMAN’S-PIPE

A vine producing evil-smelling flowers, which trap insects sometimes for
days, thus insuring cross-fertilization.]

plight of the insect at the bottom of the upward-pointing tubes, one
leading to the organs of reproduction, the other to the exit? By an
almost diabolical cunning the inside of this flower is so smooth that no
insect can crawl up its slippery sides. It takes some time for the
prisoner to find this out, and, in the meantime, it has explored every
nook and corner of the flower by flying. In the course of this
exploration it reaches and covers the stigma with pollen, for as we
shall see presently, it always comes _into_ the flower pollen-laden.
Evidently becoming panicky about getting out, the insect then flies with
very considerable force in every direction. Toward the true exit it
naturally flies the most, and by a refinement of cruelty this is the
lighter end of the flower, and therefore the obvious mode of escape for
it. But the three lips and the entrance they cover are not flat across
the flower, as the cover of a lunch box would normally be, but turned at
such an angle as the lunch box would be if set on end. The insect, in
flying toward the light, invariably hits the smooth surface just inside
the three lips and falls to the bottom of the flower because there is
nothing rough enough for it to cling to. Throughout most of the day, and
sometimes for several days, the insect will keep up this ceaseless
struggle to escape, flying first up one tube and then the other. These
frantic efforts would end in exhaustion if kept up too long, and before
that happens, but after the impregnated ovules have no further use for
the flies, the anthers give forth plentiful supplies of pollen. Of
course, the insect can scarcely avoid becoming covered with this, and
then, but only then, the flower begins to wither and up its now wrinkled
sides the pollen-laden prisoner can at last crawl to liberty.

There appears nothing very romantic about the cross-fertilization of the
Dutchman’s pipe, in fact, the whole affair seems but a sordid and, it
must be confessed, a very efficient trick to get what the flower needs
from the insect, rewarding it by many hours of apparently hopeless
captivity. But most flowers do have something that insects want, and
none so well fulfill the expectations of butterflies as the meadow pink.
This is a graceful little perennial native in the fields in central
Europe, but often grown in American flower gardens. It has beautiful
pink flowers, with a long tubular calyx, at the bottom of which are rich
honey glands, accessible only to the long proboscis of different kinds
of butterflies. No other insects, and many try, are able to get the
honey from this plant. It begins flowering by opening its five
beautifully fringed petals, all of which are marked with lines from
their edge toward the center. These obvious “pathfinders” are common on
many other flowers and all seem to be there to act as a guide for
alighting insects, and, as it were, steer them to the center of the
flower. As a butterfly alights he finds five protruding anthers covered
with pollen. These are of no use to him, but nevertheless his head is
covered by their pollen. In fact, many other visitors, who can never
reach the honey, find the bright color and good stocks of pollen
sufficient attraction for them, and after a pollen feast fly off to
other flowers. If the butterfly comes at this state of the flower’s
life, it pokes its long proboscis down into the tube of the calyx, but
finds the passage almost blocked by another set of five stamens not yet
ready to discharge pollen, and, as though ashamed of the fact, quite
hidden from view. Also, the proboscis is very nearly stopped by the
style, which, if its stigmas were ready for mating, would then and there
become impregnated. But they are rolled together into a tight spiral,
and their pollen-receptive faces tightly pressed together in addition to
the whole structure being twisted, so that the very probably
pollen-laden proboscis of the butterfly finally gets to the honey
without leaving one grain of pollen where it could possibly
self-fertilize the flower. Honey-laden, it now flies away, and so far as
this particular flower is concerned, simply nothing has happened but to
coat several insects with pollen. A little later the anthers of the
first set of stamens cease work and drop off. Then the five stamens
hitherto hidden in the calyx burst out and furnish a second crop of
pollen, but the stigmas are still safely coiled away from the possible
danger of self-impregnation. During this second stage the flower may
repeatedly be visited, but until this second crop of anthers become
useless there is not the slightest risk of the stigmas becoming
self-fertilized. For the hole through which the second set of stamens
has come is so small that still only the proboscis of the butterfly can
penetrate it. When finally the second crop of anthers also fall off,
then the style slowly uncoils and thrusts its now receptive stigmas
above the calyx and in plain view of passing visitors. These come,
pollen-laden of course, from other flowers, and cross-fertilization is
assured. Here the flower furnishes two crops of pollen, plentiful
supplies of honey, and asks only that in gathering these the butterflies
see to it that its stigma be covered only with foreign pollen. Keeping
carefully out of the way while they are about their business and there
is danger of self-fertilization, they come out boldly once that danger
is past. In this meadow pink self-fertilization is simply impossible;
everything in the production of its young it owes to the butterflies, to
which it surely makes adequate returns.

While such plants as the meadow pink and thousands of others have lost,
if they ever possessed, the power of self-fertilization, and rely
absolutely on insect visitors for their perpetuation, there are many
hundreds of kinds that apparently hope for cross-fertilization, but, in
default of it, due to their inability to absolutely compel it, they
finally accept self-fertilization as a last resort. Darwin once said
that “Nature abhors perpetual self-fertilization,” and the frequent
visits of insects and their rôle in preventing it, together with the
flowers’ adaptations to such visits, support the contention, which has
never been seriously questioned. But some flowers appear to have left
the back door open, as it were, so that failing cross-fertilization,
they may still rely upon self-fertilization. A geranium from the
Pyrenees, a relative of our common woods geranium, is of this type. A
day or two before its stigmas are ripe it produces first one set of five
anthers, all pollen-coated, and then another. If these have not been
brushed clean, as often or usually happens, then the stigmas ripen and,
of course, are impregnated by their pollen. If they are brushed clean of
pollen, then the stigmas must rely on foreign pollen, of which it is
assured a supply from the visits of pollen-laden insects from other
flowers, which are still attracted by the flowers’ color and honey.
Perpetuation is assured, in any case, but the preference is still for
cross-fertilization.

A more remarkable case of leaving one final chance for
self-fertilization is the gas plant. It exhales such a strong and
peculiar odor that only certain kinds of insects will visit it. In fact,
the odor is so strong and is so heavily charged that a lighted match
held near it has been known to slightly ignite--hence the plant’s name.
The flower bears a low, squat stigma, profusely covered with honey,
which is perfectly accessible to any insect visitor. It has ten stamens,
which at first are quite out of the way of insects, two being folded
back in each of the five yellow petals. First one stamen begins moving
gently from the shelter of its petal, and the anther, pollen-coated,
hovers over the stigma, which would inevitably lead to
self-fertilization if the stigma were only ready. It never is, and, as
though realizing this, the stamen gently moves back out of the way,
still, in most cases, retaining some of its pollen. Then another tries
and, again, as though realizing the futility of impregnating the
unreceptive stigma, it also moves back. So it goes with all the other
eight stamens, each of which moves gently out over the stigma, and
gently back again, all of them failing to fertilize the laggard stigma.
But there has been during all this time a constant procession of insects
coming for the honey, and never for a moment have the stamens been off
guard, so that each visitor goes off with at least some pollen clinging
to it. Finally the stigma, after all the faithful ten are folded back
among the petals, comes into its period, and is cross-fertilized by the
insects which come from other flowers laden with pollen, as we now know.
But if, by one of those accidents of nature, such as bad weather or what
not, no insect ever does come, what then is to be the fate of the
stigma? Has it staked all only to lose out in the end? It would almost
seem that to ignore the steady attentions of the willing ten might make
barren sterility a fitting punishment. But, in spite of what has
happened, the stamens come to the rescue, if all insects fail, and this
time, in a body, they rise up and shed upon the stigma from the
half-withered anthers their few remaining pollen grains. There could be
no finer example of having an anchor to windward.

One of the largest families of flowering plants is the pea family
(Figure 72), with over five thousand members, practically all of which
rely on bees for cross-fertilization. In some kinds, where bees
occasionally fail them, the flowers wither without self-fertilization
and, of course, no seed are then produced. In such a large family of
plants there are

[Illustration: FIG. 72.--THE EVERLASTING OR PERENNIAL PEA

A member of the Papilionaceæ or pea family which rely almost entirely on
bees for fertilization.]

naturally many different adaptations for securing
cross-fertilization--some of them of such extreme complexity that they
could hardly be included here. All the family have the characteristic
pealike flowers familiar enough in the sweet pea, which have already
been described and figured on page 44. In all of these stamens and
pistils are hidden inside the keel, at least in the early stages of the
flower. In some, such as clovers, for instance, the organs emerge from
the keel, and after fertilization by insects re-enter their retreat.
There are scores of different plans for securing the desired object, but
the common alfalfa, with a few other related plants, has the most
startling. The flower begins life with its stamens and pistils
concealed within the keel, which is apparently impregnable. When a bee
alights on the flower and begins work he is welcomed by a small but
violent explosion. When the dust of this clears away, and it is actually
dusty with pollen, the dazed bee is seen to have fertilized with almost
instantaneous rapidity the stigma of the exploding flower, which springs
violently out of the burst keel. This is so arranged that, as it flies
out of its trap, due to the explosion touched off by the bee, it strikes
the under side of the bee’s body a distinct blow, brushing off in the
process the pollen nearly always found there. This pollen has come from
other plants. But, as in most plants of the pea family, the stamens
closely surround the stigma, but are shorter than it. When the explosion
occurs, the stigma, because it is slightly longer than the stamens, is
the first thing to strike the bee’s body. Already impregnated, it is
then indifferent to the cloud of pollen from the stamens of its own
flower, which only a fraction of a second later also strikes the bee’s
body. The first flower that a bee visits cannot, of course, be
cross-fertilized notwithstanding the explosion which results, no matter
from what angle the bee attempts to insert its proboscis. But in this
case, as the stigma is unfertilized by foreign pollen, its own performs
that service. In the vast majority of cases cross-fertilization is
assured by certainly the most novel of processes, and, in the rare event
of the bee not being covered with foreign pollen, self-fertilization is
still possible.

In many of the plants already noted cross-fertilization is accomplished
by virtue of the fact that the stamens mature before the stigma. But in
the common strawberry the reverse is true. As the insect stands on the
white petals, it must, in order to reach the honey at the base of the
flower, put its head down so that if pollen were available there could
only result self-fertilization. But while the stigma is ready, the
pollen at this stage never is, and the insect which comes usually laden
with pollen from other flowers cannot avoid impregnating the stigma with
this foreign pollen. Later the stamens mature and, as insect visits
continue so long as honey is to be found, they become dusted with pollen
which is used for the fertilization of other plants. Scores of other
plants also produce ripened stigmas before the pollen matures, and they
must rely on insects to cross-fertilize them.

The cross-fertilization of the strawberry is such a comparatively simple
process--seems in fact almost inevitable--that we are lost in wonder at
the almost mathematical complexity of the act in the common purple
loosestrife, which has been introduced into American gardens from
Europe, and sometimes runs wild. In this plant there is a long terminal
spike of showy, purplish-pink flowers, the color of which is sufficient
to attract many insects from even a fairly swift flight. The petals are
streaked with “pathfinders” toward the center of the flower. This
consists of a tubular calyx; at the bottom of this is the honey, which
secures the insect’s further interest once the color has attracted it.
But it finds a condition of the reproductive organs almost without
parallel. In some plants the style is hidden down in the calyx tube,
while one set of stamens just peep out of the end of the tube, and a
second set are still further and quite obviously protruded. In a
neighboring plant the style will be found outside the tube, one set of
stamens hidden in it, and the other set outtopping everything, except
the petals. In still a third type of the loosestrife, the style exceeds
everything but the petals, one set of stamens just emerge from the tube
and the lowest set are hidden. It would appear as if the loosestrife
could scarcely escape self-fertilization, except possibly in that form
where the stigma outtops all the stamens, and this would result always
if the pollen were indiscriminately useful from all three lengths of
stamens. But it never is, only that from the short-stamened plants will
fertilize the short-styled one, the mid-stamened ones the mid-styled
counterpart, and the long-stamened ones the long-styled flower. The
pollen grains of the different-lengthed stamens are even of different
size and color. If this were not so, it is a simple mathematical problem
that, with three different sets of style lengths and six sets of
stamens, two in each flower, eighteen different crosses might be
possible. As it is, only six crosses are ever possible and these only by
the aid of insects, for it must be remembered that stamens and pistils
of the same length are never found in the same flower. By an adjustment
of the size of the body of the different insect visitors it works out so
that, while all three body sizes frequently visit each flower, only that
particular size of insect suited to the carrying of pollen from stamens
of one definite length to a style of similar length actually
accomplishes the cross-fertilization of that particular flower. And this
without interfering with the visit of another different-sized insect
which will accomplish the work for its particular set of stamens and
pistils. So marvelous is the adjustment of style length and stamen
length to each particular body size of the visiting insects, so perfect
is the arrangement of the organs in each flower, that each contributes
to the fertilization of its neighbors, never to its own, nor does it
interfere with the process in other lengthened styles.
Cross-fertilization is thus almost always accomplished in the six
different combinations possible in this truly remarkable case of
adaptation between insects and flowers.

From the almost mathematical complications of the cross-fertilization of
the loosestrife it seems a far cry indeed to that of the Italian
honeysuckle. This often runs wild over fences, but is unlike the more
widely known Japanese honeysuckle, in that its stem passes through the
different pairs of opposite, bluish-green leaves, which are joined
together at the base. The Italian honeysuckle falls back on the more
simple seductions of odor and honey for securing its really important
insect visitors. It has such a long tube that only certain night-or
evening-flying moths or butterflies can reach the honey. There is, even
during the day, such a plentiful supply of this that it frequently fills
half the tube, but even then it is quite out of reach of bees which
never succeed in getting any. Toward evening, particularly on quiet,
still evenings, the flower begins to send off in much increased quantity
a heavy rich-scented odor almost overpowering in its sweetness. The
butterflies and moths of the dusk having a long proboscis, succumb to
this really enchanting lure, which, with the large store of honey,
insures quantities of eager suitors. The stigma, while ripening
simultaneously with the anthers, protrudes beyond them, so that the
butterflies touch pollen only _after_ touching the stigma, which of
course is impregnated with pollen from an earlier visit of the insect to
a different flower. So assiduous are the butterflies, that on a still
night there will be not one grain of pollen left on the much-brushed
anthers. If the night is cold or windy much pollen remains and
cross-fertilization is left to pollen-eating insects such as mother bees
or flies. While these can never get the honey they often do accomplish
cross-fertilization and, sometimes by misadventure, self-pollination. It
is only those moths and butterflies which, forcing their long proboscis
down the honey-laden tube, must accomplish cross-fertilization. But
failing this, the plant is more or less at the mercy of hosts of insect
triflers, mere pollen eaters, who may or may not insure
cross-fertilization, but in any case provide for self-fertilization.

Another use which certain plants make of honey, besides acting as a lure
of insects, is found in the common lilac. The flower in this has
considerable honey at the bottom of the tube, which can only be reached
by insects with a proboscis sufficiently long to reach it. The lilac has
only two stamens inserted near the top of the tube, the passage to which
they very nearly obstruct. The stigma is hidden in the tube, and it
matures simultaneously with the ripening of the pollen. As the insect
inserts its proboscis between the stamens no pollen clings to it due to
the character of the pollen grains. But as the proboscis is withdrawn
from the tube its lower end is covered with honey to which pollen
sticks. If a needle is inserted between the stamens and pushed only far
enough to be still clear of the honey, no pollen will be found on it
when withdrawn, but if pushed all the way down, its honey-coated point
will catch considerable pollen. In the lilac, if insect visitors do not
accomplish the work of cross-fertilization, the flower is
self-fertilized ultimately by the protruding of the stigma far enough
out of the tube to catch some of the remaining pollen grains.

It is perhaps useless to multiply instances of flowers which by various
devices secure the cooperation of insects in getting pollen from a
foreign source. To recapitulate some of those devices it is necessary
only to recall what some flowers have done to force cross-fertilization.
The heated chamber of the magnolia, the cruelty of the prison cell in
Dutchman’s-pipe, the blow from the stamen of the barberry, the faithful
rotation of the ten stamens of the gas plant, the explosive flower in
some members of the pea family, the lure of honey and seductive odor of
the Italian honeysuckle, the mathematical complexity of the
loosestrife--these and hundreds of others all point to the necessity of
cross-fertilization and a means to produce it almost beyond belief.
There is the best of evidence that not only flowers but insects
themselves have been modified in this great work, and that for every
flower needing cross-fertilization some agency has been developed to
secure it. Insects, beyond all other animal life, do this work, but it
is accomplished by humming birds often, and in one plant even by a
snail.

Two of the very largest plant families, not so far mentioned in this
account, depend almost absolutely upon insects. In the daisy family,
with over eleven thousand members, the large heads of flowers, often
containing scores of individual flowers, are constantly brushed, over
and over again, by the pollen-coated bodies of insect visitors. And in
all or nearly all orchids (Figures 73-75), comprising over five thousand
kinds, the same process is accomplished. In these plants, in fact, the
act is, if possible, more

[Illustration: FIG. 73.--PINK LADY’S SLIPPER

(_Cypripedium acaule_)

A native orchid in northeastern North America.]

complicated than in any so far noted. Darwin’s book, “On the Various
Contrivances by Which British and Foreign Orchids Are Fertilized by
Insects,” reads like a fairy tale. Yet it is the result of years of
patient observation by incomparably the greatest naturalist of recent
times. To it the reader must go for the details of a drama of absorbing
interest, but too long to sketch even briefly here. Perhaps one
illustration may be mentioned of how far the principle of
cross-fertilization has been carried, and to the deadly effects of its
failure in at least one case. In a certain orchid from Brazil, known as
butterfly orchid, the pollen is nearly always carried out of the flower
by an insect visitor, but, if by mischance it is not, and falls on the
stigma, not only does it fail to fertilize the ovules, but it kills the
pistil forthwith. There may be a few other cases of such drastic
results of self-fertilization, but in any case, and disregarding these
apparently suicidal fanatics, cross-fertilization is so very nearly
universal that nature must find it of enormous advantage. Only in this
way is it possible to explain the intricate adjustments of insects and
flowers, which work together in such wonderful harmony that
cross-fertilization hardly ever fails in those flowers where it appears
to be necessary.

[Illustration: FIG. 74.--SHOWY ORCHID

(_Orchis spectabilis_)

Native of eastern North America, with showy magenta-pink or white
flowers in a loose raceme.]

It must have struck many thoughtful readers to ask a rather obvious
question at this point. Why, if untold millions of insects are
constantly flitting from flower to flower, does not the pollen get
mixed, as it is quite certain that they will not fly from a

[Illustration: FIG. 75.--RATTLESNAKE PLANTAIN

(_Peramium pubescens_)

One of the few orchids native in eastern North America, with white
variegated leaves. It grows in dense patches and bears free-blooming
spikes of whitish flowers.]

certain kind of geranium to another similar one for instance, but
perhaps to a rose? The answer to this is simple enough, but its
implications are limitless. Only pollen of a certain species or variety
is useful to the stigmas of that variety. To practically all others the
stigma is simply unreceptive, except in those closely related plants
that may all have a common parentage. When crosses between such closely
related plants do occur the result is known as a hybrid, which will be
considered elsewhere. To this extent, then, flowers are peculiarly
exclusive in their matings and promiscuity occurs in the vast number of
cases only in plants of the same species. We do not yet understand the
impotence of pollen of one species upon another; all that we do know,
which has many times been proved by experiments, is that it fails to
act. If it did act, no one could picture the chaos into which the
vegetative world would be thrown.

WIND AND WHAT IT DOES FOR FLOWERS

While, as we have seen, thousands of plants rely upon insects for
producing their young, still other thousands put everything to the
hazard of the wind. Pollen is so light that it can easily be blown very
great distances, and while the wastage is enormous, the process works so
well that the greater part of the vegetation of the earth is thus
fertilized. This is true not as to the number of different kinds of
plants, for in that respect insect fertilization is more important than
that accomplished by the wind. But in the number of _individual_ plants
concerned the wind is incomparably the greatest fertilizing agency that
is known to us. This for the reason that all grasses and sedges, most
catkin-bearing trees such as oak, hickory, birch, practically all pine
trees and their relatives rely wholly on the wind for fertilization.

For reasons that will be enlarged upon in another chapter, all of these
great groups of plants must be considered as of simple structure, some,
like the pines, relics of a remote past when no flowering plants, as we
know them to-day, existed on the earth. In any event the reliance upon
the wind is certainly hazardous, and while it of course insures nearly
universal cross-fertilization, it may well result in scanty
fertilization or, in exceptional cases, complete failure of it. Quite
obvious also is the amount and direction of the wind in the process, for
in very open and windy places grasslike vegetation, or at least a
predominance of species fertilized by wind, is likely to be found,
rather than those plants that rely upon insects, that, unable to stand
the full force of the wind, seek more sheltered places. While such a
thing is not the cause of prairies, or the predominantly grasslike
vegetation along sand dunes, or the exclusive spruce forests of the
bleak and windy north country, it unquestionably aids in maintaining the
often exclusive nature of such pure associations of plants. Over
thousands of square miles on our own great plains or on the steppes of
Russia, both subject to violent winds, the great bulk of the vegetation
is wind fertilized. It could hardly be expected that pollen, once in the
grip of such a wayward and shifting thing as the wind, should not be
wasted in great quantities. This is particularly true of pine trees,
which at pollen time may often be seen giving off golden clouds of dust,
of which perhaps 95 per cent is wasted.

WATER AS AN AID TO FERTILIZATION

Those submerged aquatic plants upon which neither the winds nor
honey-seeking insects can work the magic of cross-fertilization, seem to
be about the poorest equipped for perpetuating their kind through
impregnation of their tiny flowers. And yet, for at least two of them,
which will be described presently, the process is accomplished by an
adaptation of their mode of life to their watery environment that seems
incredible. These two have been selected as illustrating two peculiar
adaptations in the weight of pollen or pollen-holding flowers that is
common to some other submerged aquatic plants. In one the male flower,
or pollen from it, with the very nicest adjustment of function to
environment in all the realm of the plant world, is just of the right
specific gravity to float to the surface with dramatic suddenness and
perfectly timed effectiveness. In the other the pollen is _just_ enough
heavier than the water to float betwixt the surface and the bottom, so
that at the proper moment it is where it can fulfill its destiny.

The common eelgrass or tapegrass is a submerged aquatic which roots in
the mud and has long grasslike leaves which may often be seen waving
gently in the current of many quiet streams in this country and in
Europe. Down near the base and in among its swaying verdure, it bears
tiny flowers which have no petals, and in which, as if recognizing the
futility of display in such a secluded watery home, even its calyx is
reduced to small scales. Some of these minute flowers are females,
others again all males, and as they appear in their early stages it
looks as though never the twain could meet. And the hopelessness of
their ever meeting is increased as the maturing female begins slowly to
uncoil the fine stalk upon which it grows. Steadily but surely the loose
spirals of the stalk of this ever more mature female flower uncoils,
until, when quite ready for the pollen, it is at last upon the surface.
The male flowers, in the meanwhile, are down near the bottom with their
small freight of pollen ready to perform their function, but firmly
anchored to a stalk absurdly inadequate to reach the surface where alone
they can be of service. A great Belgian, Maurice Maeterlinck, who
studied this plant with more sympathetic vision than any botanist has
yet been able to equal, wrote in one of his essays on “The Intelligence
of Flowers” the solution of this little drama of apparent hopelessness.
No other words can ever convey the meaning of what happens to the
eelgrass quite so well as his. “Is there any more cruel inadvertence or
ordeal in nature? Picture the tragedy of that longing, the inaccessible
so nearly attained, the transparent fatality, the impossible with not a
visible obstacle! It would be insoluble, like our own tragedy upon this
earth, were it not that an unexpected element is mingled with it. Did
the males foresee the disillusion to which they would be subjected? One
thing is certain: that they have locked up in their hearts a bubble of
air, even as we lock up in our souls a thought of desperate deliverance.
It is as though they hesitated for a moment; then, with a magnificent
effort, the finest, the most supernatural, that I know of in all the
pageantry of the insects and the flowers, in order to rise to happiness,
they deliberately break the bond that attaches them to life. They tear
themselves from their peduncle, and, with an incomparable flight * * *
dart up and break the surface of the water. Wounded to death, but
radiant and free, they float for a moment beside their heedless brides
and the union is accomplished, whereupon the victims drift away to
perish, while the wife, already a mother, closes her calyx, in which
lives their last breath, rolls up her spiral, and descends to the
depths, there to ripen the fruit of the heroic kiss.”

In the eelgrass it is the specific gravity of the male flower, or, the
secreted air bubble, which makes the flower lighter than the water, and
actually causes the flight from the depths to the surface. Because of
this, fertilization can only take place on the surface, although the
flowers and fruits otherwise mature under water. But in sea wrack, in
Naias, and in ditch grass, all submerged aquatics, the flowers are even
fertilized under the water. Pollen in such plants is much modified, and
instead of being in the ordinary form of pollen grains, it is, at the
time of ripening, lengthened out into tubular, hairlike structures.
These delicate prolongations of the male fertilizing stuff are carried
by the currents of the water, just as a thread would be, but with the
difference that the pollen threads are so beautifully weighted to fit
their watery environment that they float, suspended, in the depths of
the water at or near the level of the female flowers. The pollen is set
free at maturity, just as it is in the eelgrass, but to meet the female,
which never rises, it must float with the current of the stream. There
must, as in the wind-carried pollen, be a tremendous wastage, yet
sufficient quantities of it do fertilize the females, particularly in
the ditch grass, which fruits very freely.

Whether it be any of the various contrivances for insect fertilization,
or by the winds, or, as in the eelgrass, by the water, the climax of the
flower’s life is always reached in this act. For all annuals the plants,
also, begin to die down then, a process that is completed with the
production of seed, which is, of course, the object of all those varied
modes of fertilization. Perhaps no answer to the question of why plants
do not always self-fertilize themselves is so eloquent as the hundreds
of ways they have adopted to avoid doing so, a few of which we already
know. Many volumes have been written on this subject, but all of them,
intricate as the methods they describe nearly always are, merely confirm
what we have already seen--that rather than submit to
self-fertilization, plants will adopt almost undreamed-of expedients.
Sometimes, as in the eelgrass and in the visits of nocturnal insects to
those night-blooming flowers that carry on their matings in the glamour
of moonlight or in the dusk of eventide, the drama, in the eyes of
imaginative writers, is one of singular beauty and charm. And, on the
other hand, we have seen the well-nigh heartless cruelty of the
Dutchman’s-pipe in keeping as prisoners its absolutely necessary insect
deliverers. Even this is outranked for matchless ruthlessness by a wild
arum, a relative of our jack-in-the-pulpit, from the East Indies. It
produces a club-shaped inflorescence composed of tiny flowers that need
cross-fertilization, but so offensive is the odor of the flower that no
insects will tolerate it. A snail, a voracious eater of foliage, is
attracted to the flower partly by the fine fleshy leaves, but mostly by
a juice secreted at the apex of the flower column. To this the snail
crawls, and fertilizes the tiny flowers over which it drags its body.
When this is accomplished it speeds on hungrily to the juice just above
it and eagerly devours the poison. Death follows almost immediately. The
secretion of this murderous liquid to lure the only creature that will
visit such an offensively malodorous plant, which, without it, would
very likely be itself destroyed by the foliage-eating snails, is a
gruesome contrast to that happy flitting of butterflies which completes
the fertilization of most flowers in equally effective but more pleasing
fashion.

Once impregnation of the ovule has been consummated, it begins a slow
process of change, involving sometimes the modification of the ovary, or
of the calyx, and very often of the swollen apex of the flower stalk
upon which these organs are borne, known technically as the
_receptacle_. We have seen, in the first chapter, what greatly different
types of fruits are developed from different ovaries, and they of
course produce seeds in varying size and amount. In the coco de mer, a
palm from the Seychelles, the seed often weighs forty or fifty pounds,
while in some orchids a single capsule will contain over a million
almost microscopic seeds. Some of the devices of fruits and of seeds to
secure the utmost spreading of the species over the earth will be
considered in another chapter. All the devious methods of plants in
producing their young become significant, so far as the earth’s
vegetation is concerned, only when we find out what this enormous
progeny has done with their opportunity. The chapter on the Distribution
of Plants will tell us how well that opportunity has been used.

2. HIDDEN MARRIAGE OF FLOWERLESS PLANTS

As we stated in the first chapter _cryptogams_, while they produce no
flowers, must bear organs that perform the _functions_ of flowers in the
reproduction of new individuals. Because, generally speaking, the
process is more hidden in its manifestations, and nearly always requires
the aid of the microscope to detect it, it is not so well known as the
reproductive processes of flowering plants by those who have not the
opportunity to manipulate such instruments. The act, however, is just as
interesting, and, as we shall presently see, it may well be considered
the ancestor of those more showy methods of producing young, which have
been all too inadequately treated in the preceding pages. While the
parts having to do with reproduction in flowerless plants are
microscopic in size, it is possible to understand the broad outlines of
what goes on and perhaps the life history of such plants is as well
illustrated in ferns as in anything else.

THE LIFE HISTORY OF A FERN

In the discussion of ferns in the first chapter we found that on the
back of some of their leaves, or occasionally on special leaves devoted
to the purpose, were many small brownish or dark spots, arranged in
rather definite fashion, and known as _sori_. (Figure 63.) Each sorus
contains many minute bodies known as _spores_, not unlike very miniature
seeds in general appearance, but quite unlike them in behavior and mode
of life. No better idea of their size can be gleaned than to record the
fact that in each sorus there may be about one hundred small, often
short-stalked spore cases, known as _sporangia_, and that in each
sporangium well over forty, and sometimes over sixty, spores will be
crowded. A healthy specimen of many of our common ferns will bear about
ten or a dozen leaves, each of which is divided into many divisions, and
among these divisions of the leaf there may be at least fifty that bear
from fifteen to twenty sori. It can be easily figured from this that a
healthy plant of this fern may and usually does produce over forty-five
million spores, each of which contains within it the opportunity of
developing into a new plant. There is thus a prodigality in producing
the means of renewal of life among ferns that far outstrips the
production of seeds in even the most prolific of flowering plants.

When the spores in the sporangium are mature and therefore ready for the
next stage in their life history several things must happen. With
somewhere about six thousand of them crowded together under each sorus,
more room to develop is obviously the first consideration. This is
provided for by the fact that when the spores are ripe the sporangia
have the ability to throw them considerable distances; then of course
the wind can carry them much farther. To be of any use they must fall
upon damp ground, for some degree of moisture is absolutely necessary
for what is about to happen to them. In nature countless millions never
do fall in a favorable location, or, if they did, such an enormous
production of fern spores would soon make the world exclusively a fern
garden. The comparatively minute fraction of them that ever do find
congenial surroundings, once they are expelled from the spore case, then
begin a process that is not unlike the germination of a seed. For the
spore must take in water from the soil, which by osmotic pressure
finally bursts it open. From the burst spore a minute tube, known as the
_protonema_, or literally first thread, begins to develop. It is, of
course, of microscopic size, and yet near its base there is a branch
tube formed, differing from it in structure and ultimately forming
_rhizoids_, which are rootlike hairs. Both the protonema and the
rhizoids begin growing, the first forming, usually flat on the ground,
an often heart-shaped body having the characteristic green coloring
matter of all plants. The rhizoids multiply and look not unlike roots.
This young, still microscopic plant, grows apace, and may soon be
distinguished with the naked eye. It looks not unlike a heart-shaped
mass of greenish tissue quite flat on the ground, and is called a
_thallus_.

Up to this point, then, we may trace the story of any fern which has
thrown off its cloud of spores and from which develops this tiny
thallus, looking not in the least like a fern nor as though it could
ever be modified into one. Because this thallus is,

[Illustration: FIG. 76.--PROTHALLUS OF A FERN SEEN FROM THE UNDER SIDE

(_A_^{1}) archegonia, (_A_^{2}) antheridia, and (_A_^{3}) the rhizoids.
_B_: Prothallus, showing the young plant with its first leaf (_B_^{1}),
its own roots (_B_^{3}) and the rhizoids of the prothallus (_B_^{2}).
Drawing and legend for it slightly altered from Kraemer.]

in the truest sense, merely a preparation for the process that _will_
produce another fern, it is always known as a _prothallus_. The
prothallus is thus the first stage in the reproduction of ferns, a very
simple stage, with only the faintest indication that the thallus might
be considered the vegetative and its rhizoids perhaps the rootlike
counterparts of foliage and roots of mature ferns. As we shall see
presently, even this differentiation has not the significance that such
a structure in flowering plants would indicate. There is not, as yet,
the faintest indication of sexes that need to mate in order to produce
their young. The spore has so far only produced a tiny flat body of
green tissues with a few rootlike threads, so unlike the fern from which
it started that its true significance, or even the fact that it had
ought to do with ferns was not known until about the middle of the last
century.

This green cushiony prothallus keeps on growing, its heart-shaped mass
becoming divided into an obviously left and right hand side and the
rhizoids multiplying in number. They are always borne on the lower side
next the ground, or next whatever the prothallus may be growing on. Near
the notch of the heart-shaped prothallus are developed a few
flask-shaped bodies which contain within them an egg cell or single
ovum, the female reproductive body. By a series of changes this egg cell
becomes embedded in a mucilaginous material. This flask-shaped body with
the female egg cell inside is known as the _archegonium_. From among the
rhizoids there may, at about the same time, be found developing small
globular organs that have in them a number of tiny cells, each of which
has attached many minute threadlike tails. The globular organs, with
their minute, tailed cells are known as _antheridia_, and comprise the
male reproductive equipment. Just as in flowering plants, neither the
_archegonia_ (female) nor the _antheridia_ (male) can produce offspring
without mating and the method by which this marriage is accomplished
differs tremendously both in practice and in its significations from
that in phanerogams. In the first place, the male and female
reproductive cells are separated by a considerable distance, they are
both inclosed in structurally different casings, and the whole operation
is so microscopic that insects can be of no service. Nor can the wind do
for them what we have seen that it does for the pollen of pines and
grasses.

Of the aids to fertilization there remains then only the water, which
plays such an important part in the mating of the eelgrass and ditch
grass among flowering plants. But in these ferns a very different drama
is about to be enacted. The male cells, as we have seen, are provided
with slender tails, which are movable. They move, in fact, to such good
purpose that the male cell can actually swim in the water. Of course its
minute size demands only the merest drop of water, in which it will take
the only excursion of its brief life. For just as soon as it is mature,
a heavy dew or the tiniest particle of water will set free the little
male messengers. The water too has not been without effect on the female
cell. More remarkable still, this mucilaginous matter contains in it a
substance that acts as a lure to the swimming male cells. In any event
they do swim directly to the entrance of the female cell’s abode,
through it and to her, when the union is effected. At once there is
thrown across the entrance a membrane that excludes all other males, and
the fertilization is complete. From this union of the male and female
cells a true young fern begins to develop. First a young leaf and roots,
finally a stem and in the end, of course, a full-grown fern producing
spores, ready to renew the whole process.

Some ferns do not follow all the steps exactly as we have outlined, for
all of them have not the structure of the typical one whose life history
has been sketched above. In the adder’s-tongue fern, for instance there
is a stalklike prolongation from the base of the only leaf the plant
bears, on which all the spores are borne. In certain others, as in the
ostrich fern, the spores are borne on leaflike growths that serve only
this function. Most ferns, however, bear spores on otherwise unmodified
foliage leaves and the great bulk of them on the under side of such
leaves.

There are several things about the life history of a fern that differ
fundamentally from any flowering plant and perhaps the chief is what is
known as the alternation of generations. A spore, for instance, can
never produce a fern as a seed will always produce a flowering plant. In
this respect they are like many insects that always have two or
sometimes three different stages in their life history. Only by the
complicated method of first a spore then the prothallus, from which
archegonia and antheridia are produced, followed by the free swimming
male cells fertilizing the female, can a fern reproduce itself. As we
shall see in the chapter on the History of the Plant Kingdom, this
alternation of generations, the absolute necessity of water in which to
carry on the fertilization, and above all the ability of the male cells
for free swimming in the water, are all landmarks in the development of
plant life. In its simplest form fertilization in flowerless plants is
characterized by one or all these processes, as it is in the ferns,
while in the flowering plants, the act is accomplished by processes,
discussed previously, which, in the development of the plant kingdom,
mark a period only comparable, in the history of man, to such tremendous
achievements as the acquirement of speech or the ability to make a fire.

LIFE HISTORY OF A MOSS

Ever since the war, the peat-forming mosses, known as sphagnum, have
become more widely known to the general public than any of the ten or
twelve thousand mosses known to grow on the earth. Its power of
absorption, greater than linen bandages, made it extensively used to pad
surgical dressings. Hundreds of thousands of these sphagnum

[Illustration: A SMALL CLOUD OF WIND-BLOWN POLLEN OF THE JAPANESE RED
PINE (_Pinus densiflora_). (_Photo by C. Stuart Gager. Courtesy of
Brooklyn Botanic Garden._)]

[Illustration: A COCONUT GROVE IN THE PHILIPPINE ISLANDS. The people of
tropical regions have more uses for this plant than there are days of
the year. Its fruits will float in the sea for months without injury and
it is thought to have been distributed all over the tropical world by
ocean currents. Its true wild home is not certainly known, but is
probably tropical America. See chapter V for an account of the tree.
(_Courtesy of Brooklyn Botanic Garden._)]

dressings were made, and the collection of sphagnum from the bogs in
which it nearly always grows was the task of many who could render no
other service.

The reproduction of sphagnum is not unlike that of ferns already
described. There is the same necessity of a film of water in which the
free swimming male can fertilize the female. But some other things about
their reproduction of young differ from ferns.

In the first place sphagnum is a nonvascular cryptogam, in that its
leaves have no veins or ducts in them and its minute stem is also
without those conducting passages that characterize all ferns, and the
flowering plants, which are considered the most highly developed of all
plant life. (See Chapter I for a discussion of this point, in the
section devoted to “Flowerless Plants.”)

In this moss, also, there are small branches, some of which bear only
the tiny leaves, but some bear leaves and the reproductive organs. The
female or _archegonia_ are much like those in the ferns, and the
_antheridia_ or male are also, as in the ferns, minute globular organs
in which are the male cells. The branches bearing males are greenish,
yellow, or even reddish, quite unlike the ashy gray foliage leaves which
give to sphagnum its characteristic ashy gray color. Unlike the ferns,
the male cells of sphagnum have only two tails, but they nevertheless
swim, tail first, to the female, when the time for fertilization comes.
The female branches are found mostly toward the upper end of the plant
and bear the archegonia at their extremities.

From what we know of the reproductive stages in the ferns it is now
obvious enough that in sphagnum moss, as we ordinarily see it, we have,
because it bears antheridia and archegonia, a quite different condition
from the ordinary spore-bearing leaves of ferns. For as yet spores have
not been developed on the moss. The mating of male and female cells,
directly on the plant, proves that in this “plant,” at least, our
ordinary notion of this moss is mostly confined to a stage in its life
history comparable in ferns to the production of archegonia and
antheridia on the fern prothallus. From this mating of the male and
female cells there results, as in the ferns, the production of a
spore-bearing structure. This consists of a spore case, matured for the
most part in the chamber occupied by the fertilized female cell, but
ultimately its cap is carried upward. Later on the spore case ruptures,
releasing the spores. As in the ferns, these germinate, forming a short
green protonema followed by a prothallus. From this a short leafy branch
develops, which completes the life cycle, as this is the young moss
plant.

In other words, sphagnum, as we ordinarily see it, produces, on the
plant, male and female cells which unite to form a spore case with
spores in it. These are shed, develop into a protonema which is followed
by the prothallus and from this the young moss plant develops. In ferns
the conspicuous well-known stage is the spore-bearing one, in sphagnum
it is the production of male and female cells directly on what appears
to be the mature plant.

There are many other kinds of mosses than sphagnum, and their life
histories differ in slight degrees from it. But they all agree in this,
that the greenish, feathery little moss plant is a stage in its life
history bearing male and female cells, the mating of which produces a
spore-bearing contrivance. In most of the familiar green mosses this is
a capsulelike body on a short stalk, usually well elevated above the
green mass of plants. From this the spores are shed and develop into a
protonema or “first thread” just as in ferns. Unlike them, and unlike
sphagnum, the green mosses produce no thallus, and the young leaves of
the moss are developed directly from this protonema.

LIFE HISTORY OF A MUSHROOM

The common mushroom that we eat is easily enough divided into a thick
stalk, known as a _stipe_, and a broad hood called a _pileus_. The under
side of the pileus is seen to be composed of thin plaits set closely
together and radiating from the center toward the edge. These are known
as _gills_. From among the gills the spores are shed when they are
mature, usually foretold by the changing of the color of the gills from
whitish to purplish and even to brown or blackish. The spores are then
shed and ready for the next stage. From what we already know about ferns
and mosses, it is clear that from these spores a mushroom cannot develop
without the production of male and female cells and all the rest of that
process of hidden marriage that characterizes all flowerless plants. But
in most mushrooms no one has ever seen, nor have the most carefully
conducted experiments ever demonstrated the germination of the spore. So
far as we know at the present, many mushrooms may or may not produce
their young through the germination of their spores in their native
fields and meadows and the subsequent production of male and female
reproductive organs. But if their spores do produce such organs, which
all our knowledge of spores makes probable, it is, in a truer sense than
in most cryptogams, a case of hidden marriage. The process of producing
their young is thus a secret one that scientists have not yet been able
to disclose. Of course it is a common practice of mushroom growers to
purchase _spawn_ from seedsmen which under favorable conditions will
produce many young mushroom plants. This, however, is the production of
young without mating of the sexes, a fairly common characteristic of
many other plants which will be considered presently.

As we saw in the section devoted to Flowerless Plants in Chapter I,
there are many other kinds of fungi than the familiar edible mushroom
and their close relatives, the often deadly poisonous toadstools. The
reproductive processes in these other fungi are fairly well understood,
but they can hardly be included here. In the mold on bread, the yeast
used in baking, the rust of wheat and the diseases of other plants and
of animals, the individual organism is so minute that it can only be
detected under the microscope. Their reproductive processes are, of
course, on such a minute scale that they could be followed with profit
only by those equipped to study them. They have been described in many
botanical textbooks, and those interested in them should consult such
books.

In recapitulating the reproductive processes in cryptogamous plants the
thing that distinguishes them from all flowering plants is that they
bear, in some stage of their life history, a spore. From this, in the
great bulk of them, a mature plant never develops. Only by the
production from the spore of some contrivance for bearing male and
female cells, which may, as in some seaweeds, even be on different
plants, can a mating of these be accomplished, and from this union will
develop the mature plant. There are many modifications of this plan, but
in nearly all of them the presence of water, for the free swimming of
the male cell to its mate, is essential. Just as in flowering plants and
in all the larger animals, however, the reproduction of young in
cryptogams is a sexual process depending on the union of male and
female. While in phanerogams that process may well be spoken of as
visible marriage, with all the pageantry of insects and beautifully
colored flowers, in cryptogams the process is not only a hidden
marriage, its ways are sometimes so secret that, even in the common
mushroom, the actual mating is conjectured rather than demonstrated.

THE PRODUCTION OF YOUNG PLANTS WITHOUT MATING

It is so generally true in all plants that a union of male and female is
necessary for the production of young, and, as we have seen in most of
them, the process is so uniformly successful that still another mode of
producing them seems almost unnecessary. Yet in a surprisingly large
number of plants new individuals, both of flowering and flowerless
plants, are regularly produced without such a union and where sexuality
has nothing to do with the increase.

In the life plant--a thick-leaved shrub from Mexico commonly grown in
greenhouses--the leaves are wavy margined. From their edges, especially
when injured, many tiny new plants will often start to grow. Even if the
leaf is cut up into fairly small pieces many of these will develop young
plants, and in various forms of the common rex begonia the leaves are
usually cut into small pieces by gardeners for the production of young
plants which always sprout from such pieces. It is useless to multiply
such cases, as everyone knows of the production of young plants from the
ends of strawberry runners, the cutting up of potatoes, the universal
garden practice of making cuttings, and the sprouting of willows, all of
which are effective by virtue of this faculty of plants to produce young
quite without the intervention of different sexes. Not so well known are
the cases of a liverwort, a small relative of the mosses, which, if
chopped into fine pieces, each will develop into a new plant. We have
already spoken of the spawn of mushrooms; and even on sphagnum moss, in
addition to its sexual reproduction, it produces sterile branches that
will root and, after separation from the old plant, form a new one.

Wherever this tendency is found, whether it be in a microscopic seaweed,
some of which know no other means of reproduction, or in the showy
begonia, it depends for its success upon a property of the ultimate unit
of its structure, the cell. Sometimes, as in bacteria or the most minute
seaweeds and in some other kinds, the whole plant consists of a single
microscopic cell, when it is said to be a _unicellular_ plant. All
others, in which the grouping or modifications of the cell makes more
complex structures, such as trees or shrubs and all the plants that
grow, both flowering and flowerless, are called _multicellular_ plants.
Whether they be of one or many cells, these have the faculty of
dividing, and by this division making two where one existed before the
division. This division of cells is what happens in the normal growth of
plants and it is this division, in more unusual ways, that results in
the production of new plants without mating of the sexes. As cells are
themselves microscopic, of course their division is equally so, and
cannot be described in detail here. It has been many times described and
pictured both in books on plants and animals, as it is the ultimate unit
of the structure of both.

Plant life, then, seems to be better provided with means to renew itself
than most animals, for, as we have seen, it has several methods to rely
on. These may be divided into sexual, which includes both that in
flowering plants with their visible mating and in flowerless plants with
invisible mating, and _asexual_, literally without sex. In the latter
are all those unicellular plants that reproduce themselves by simple
division of the cell, and also those flowering plants that either
naturally, as in life plant, or by the gardener’s art of making
cuttings, produce new plants quite without the intervention of the
sexes. Whether it be sexual or asexual, nature has more than fulfilled
its obligation to the plant world in providing it opportunities for
self-renewal. No matter what apparently unfavorable condition arises and
often in spite of an almost unbelievable wastage of potential life
stuff, the renewal goes on, or else there is the total disappearance of
the species. So strong is this tendency to provide for renewal of their
kind that many plants, if injured or cut by a mower, will almost in
their last gasp hurriedly flower and set seeds, and we have already seen
that the little liverwort, even if cut to pieces, also obeys that nearly
universal law of nature: “Be fruitful and multiply.”

CHAPTER IV

THE FAMILIES OF FLOWERING PLANTS AND THEIR RELATIONSHIP

There are perhaps over 150,000 different kinds of flowering plants known
in the world to-day, but the flowerless ones are fewer than these in
numbers. No one really knows how many thousands of the cryptogams there
may be in the world, for all of them have not yet been described, and
there are doubtless thousands of which we merely suspect the existence.
Flowering plants are so much better known, and have for 2,000 years been
the subject of scientific writings, that their relationships and obvious
groupings into families are fairly definite and often easily
recognizable.

In our ordinary discussions or gossip of neighbors or relatives, the
absolutely necessary starting point is to know their name. Their
acquirement of this by christening, or by the adoption of it through the
usage of parents, settles for life what they will be called. Plants are
also christened, and that ceremony is one of the most important events
in our subsequent discussion of them.

PLANT NAMES AND HOW THEY ARE ACQUIRED

As we always have at least two names, one to show that we are a Smith,
for instance, and another to fix us as John Smith, so all plants have
two names, sometimes three.

And because plants come from all over the world and are studied and
loved by people of many different languages, it became necessary very
early in the descriptive writings about them to hit upon some device
that should insure the name of a particular plant being the same all
over the world, whether used by a student in the Imperial University of
China, or by a garden enthusiast in Connecticut. At the time when this
need for christening plants with names that would pass current
throughout the world was getting to be a crying necessity, the language
of all learned men was Latin, so it was natural that they should give
Latin names to plants. That practice has continued to the present day,
and there are even now some botanists that cling to the old custom of
describing the newly christened plant in Latin. In the olden days this
was always done, so that much of our knowledge of plants has come down
to us from early books written wholly in Latin. The unfamiliarity of
Latin to most of us, and the terrifyingly difficult spelling of some
plant names, has resulted in many people saying: “God made the flowers,
but the devil gave them names.” Nevertheless, these Latin names are the
only ones we can use without endless confusion, just as we bear the
names assigned to us by our parents, and no others.

If we were to go out into the country and pick up a wild rose which
seemed to be different from any other rose, it would be necessary, in
order to talk about it subsequently, to give it a name. After carefully
searching through all the books about roses and finding out that it
really is a new kind of rose rather than merely being new to us, we
should then be ready to christen our new find. As we have said, all
plants bear two names. One of these is a general one, like Smith, for
instance, and the other more specific, like John. These general names of
plants, and they are always their first names, are, because they fix the
plant as belonging to a particular group, known as generic names. The
generic name of violets, for instance, is _Viola_; of buttercups,
_Ranunculus_; of wheat, _Triticum_; of corn, _Zea_; and of roses,
_Rosa_. Our new rose then bears, without any act of ours, the generic
name _Rosa_, which was applied to roses many years ago, and must
therefore be used for all subsequently discovered roses. This generic
name of _Rosa_, like all other generic names, tells us that roses are a
well-recognized group of plants, all more like one another than like
blackberries, for instance, and because of this they are said to all
belong to the same genus. A genus (plural, genera) is a group of
different plants, all more like one another than like anything else. To
go back to our new _Rosa_, we must now apply its second and more
specific name. If it were a white rose, and had never before been
described, we should almost certainly use for its second name something
signifying its color and assign _alba_ as the obvious Latin equivalent
of white. The second name is always called the specific name, because it
shows us that from all other roses our new _Rosa alba_ differs in being
white. It is of the genus _Rosa_, but it is also and forever after a
recognized member of _Rosa_, to which a specific name has been
applied--in other words, _Rosa alba_ is a species of rose. Species are
thus plants more like one another than they are like any other member of
the genus to which they belong. _Rosa alba_ is a species quite unlike
_Rosa lucida_, or _Rosa carolina_, or all the other scores of roses
already known or described. At the time of christening _Rosa alba_, we
should not only enter its name in a book, as ours would be in a parish
register, but do much more than that. We should so carefully describe it
and, preferably, illustrate it with a picture that no one coming after
could ever mistake _Rosa alba_ for any other rose. It can be readily
seen that the christening of new plants is very nearly as serious an
affair as christening babies, and furthermore, it is only to be
attempted by experts. Because this has not always been done, many plants
have been christened two or three times. Of course, these subsequent
christenings do not seriously matter, for plants, like ourselves, should
have only one specific name, the first applied to them. But their
subsequent christenings by the careless and ignorant have enormously
increased the difficulty of talking or writing about plants. These
spurious names are common throughout the literature of botany and are
known as synonyms.

The thing to remember about plants, so far as our need for classifying
them is concerned, is that they belong to different species which might
almost be considered the unit or simplest recognizable category into
which they may be sorted. For convenience, we sort species into genera
which may well be considered the next highest category in which plants
are grouped. The grouping of genera into tribes, of tribes into
families, and of families into still larger categories, has nothing to
do with their names, but everything to do with our understanding of how
they are related to one another, and what these different categories
mean in the great collection of plants all about us. In other words, it
reduces to a definite system an apparently hopelessly mixed-up mass of
plants that, without some contrivance of the sort, would simply be a lot
of totally unrelated specimens of plant life. Actually they are grouped
in fairly definite categories, some of which are easily recognizable,
and all of which fit into that great scheme of nature where everything
may seem chaotic, but to the observant it is really a very pattern of
order. What it all means and how plants have been grouped into families
will be explained, now that we understand how they have acquired their
generic and specific names.

PLANT FAMILIES AND ORDERS

A scientist once visiting in Bulgaria noticed that the peasants in that
country frequently lived over a hundred years and, in trying to find out
the reason, he discovered that they drank large quantities of sour milk.
This is alive with a definite kind of bacterium that is of great benefit
to the digestive apparatus, and therefore helps in the prolongation of
life. In Bulgaria, in other words, a certain food habit of the people
has resulted in a definite prolongation of life and fixes that
population as of somewhat different characteristics from people not
addicted to sour milk. In Japan a whole race lives largely on fish and
rice, and while this is not the cause of their yellow skin, it is almost
surely the cause of their generally small stature. Many of the English
are tall, light-haired, and blue-eyed people, fond of outdoor life and
sports, and among the most highly developed of the peoples of the earth.
The climate of that island, their generally large consumption of meat
and the outdoor life of so many of them, have resulted in quite definite
characteristics that make the typical Englishman an easily
distinguishable type.

In studying man we are able not only to divide him into such broad
divisions as white, black, and yellow races, but due to their particular
country or mode of life there are scores of racial subdivisions of these
larger categories that everyone recognizes. Such differences are often
based on stature, shape of head, mental characters and many others, but
those still finer shades of difference between, for instance, a
Connecticut Yankee and a plantation owner in the South, are, while noted
by everyone, very difficult to accurately describe.

In attempting to find such major differences in plants, some structural
character that would set off one large group of plants from every other
group, the botanist has a harder task than the person studying man. For
all those differences of language and mentality that make up such a
large part of our common knowledge of the different peoples of the earth
are characters that are foreign to plants. We are thus thrown back on
structure as the chief way in which plants differ, and because their
reproductive organs are their most important ones, and therefore least
likely to vary, it is upon certain characters of these organs that all
flowering plants have been divided.

In the chapter on “How Plants Produce Their Young,” we found that most
flowering plants have their ovules in an ovary which, after
fertilization, develop into fruit and seed. But some plants, while they
have ovules, only bear them naked or between scales, never inclosed in
an ovary. This is true in all pines, spruces, hemlocks, and all the host
of their generally evergreen relatives. Such trees bear cones, between
the scales of which are perfectly naked ovules that develop into seeds
(Figure 77) that have never been hidden in an ovary, as have the vast
majority of the seeds of other plants (Figure 53). These naked-seeded
plants are known as _gymnosperms_ or literally _gymnos_, naked, and
_sperma_, seed, and comprise all the cone-bearing trees in the world,
the larger part of which are always evergreen. In some past ages such
trees made up the bulk of vegetation of the earth, but at present they
are much reduced in numbers. Familiar examples of these _Coniferæ_, or
cone-bearing trees, are larch, spruce, fir, pine, hemlock, juniper, and
yew.

[Illustration: FIG. 77.--THE JERSEY PINE

(_Pinus virginiana_)

A gymnosperm or naked-seeded plant. Note the seeds dropping from between
the scales of the cone.]

Most of these are evergreen, which does not, of course, mean that they
bear the same leaves always, but that only a few drop off at a time and
are so constantly renewed that the tree is actually ever green.

All other flowering plants always bear their ovules in an ovary and,
because of this fact, are called _angiosperms_, literally _angeion_, a
vessel, and _sperma_, seed. These inclosed seeded plants comprise the
great bulk of the vegetation of the earth to-day. So far as the
temperate zone is concerned, nearly all of them drop their leaves in the
fall, and the trees belonging to the angiosperms are thus said to be
deciduous trees.

No better idea of the present size and importance of these two groups of
plants can be gained than to state the fact that perhaps not over 500
different kinds of gymnosperms, all of which are trees and shrubs, are
known. All the rest of the flowering plants in the world, comprising
over 150,000 different kinds of herbs, shrubs, and trees of infinite
variety, are angiosperms and therefore bear ovules in an ovary, followed
by seeds in or on some sort of a fruit. It would almost seem as though
the simplest way to dispose of this great mass of plants would be to
sort them into trees, shrubs, and herbs. For all of them belong to one
of these types of plant growth, and the ancient students of plants, just
before the time of Christ, actually divided all flowering plants into
these three classes. This, of course, threw the coniferous trees in with
all other kinds and, as we have already seen, they differ from all other
kinds in the important character of having naked ovules.

Here, again, in order to get some system out of apparent chaos, we must
fall back on some fundamental character. And, again, it is the product
of the reproductive process in all this host of angiosperms which
furnishes the clue. In the seeds of many of them the young embryo has
folded up within it two seed leaves, while in all the rest only one. As
we saw in Chapter I, these seeds germinate either with a single seed
leaf, like corn (Figure 85), or with two seed leaves, like beans (Figure
81). Every one of these angiosperms belongs to one of these classes or
the other, and perhaps more extraordinary still is the fact that in
those with one seed leaf there are associated certain leaf and flower
characters, while those with two seed leaves are always very different.

In the monocotyledons, or plants with a single seed leaf, the leaves are
practically always parallel veined (Figure 83), like corn and grass, and
lilies and palms, and hundreds of others. Also, they nearly always have
the parts of their flowers in threes (Figure 84). That is, they have
three sepals, petals, stamens, and often pistils, or multiples of three.
The common trillium or wake-robin, for instance, has three sepals, three
petals, six stamens, and three styles. With a few exceptions, and nature
seems to delight in producing a few such, all monocotyledons have this
parallel-veined leaf character and flower parts in threes or multiples
of three.

Plants which send up two seed leaves (Figure 81), on the other hand,
bear practically always netted-veined leaves (Figure 79), and the parts
of their flowers are nearly always in fours or fives or multiples of
these numbers (Figure 80). The well-known wild geranium has five sepals,
five petals, ten stamens, and a five-lobed or five-celled ovary. There
is some individual variation from this plan, sometimes one organ and
sometimes another having more or less than the regular number. But so
overwhelmingly true are these distinctions that dicotyledons, or plants
with two seed leaves, and monocotyledons,

[Illustration: FIGS. 78-85.--PLANT FAMILIES

Dicotyledonous and Monocotyledonous growth habits contrasted. Figs.
78-81. The trunk of a dicotyledonous tree showing division of the wood
into heartwood, sapwood, and cambium, which the removal of a piece of
outer bark exposes. Note the net-veined leaf (79), the seedling with two
seed leaves (81), and with the parts of the flower in 5’s (80). Figs.
82-85. Monocotyledonous plant. Note the lack of zones of wood, cambium
and corky bark. Such plants have parallel-veined leaves (83), parts of
their flowers in 3’s or 6’s (84), and germinate with a single seed leaf
(85).]

or plants with a single seed leaf, have been for hundreds of years the
two great classes into which all angiospermous flowering plants are
divided.

Our general view of all the flowering plants may be summarized then as
follows:

1. Gymnosperms, or naked seeded plants, include all cone-bearing plants,
mostly evergreen and always trees or shrubs. The pine is a familiar
example.

2. Angiosperms, or inclosed seeded plants, include all other flowering
plants of whatever kind. Divided into: (_a_) Monocotyledons. Sprouting
with one seed leaf, and leaves practically always parallel-veined. Parts
of the flower in threes or multiples of three. Familiar examples are
corn, grass, sugar-cane, palms, cannas, and lily of the valley (Figures
82-85). (_b_) Dicotyledons. Sprouting with two seed leaves, and the
leaves practically always netted-veined. Parts of the flower in fours or
fives or multiples of these numbers. Includes all the remaining
flowering plants and is a larger group than the monocotyledons and the
cone-bearing plants combined (Figures 78-81).

No matter from what part of the world a totally unfamiliar plant may
come, it is always possible to decide into which one of these groups it
belongs. That in itself tells us a good deal about its ancestors and its
future, “places” it, in fact, in one of those major groups into which
all plants are divided. No other characters that plants possess are so
important in determining their true position in the scale of plant life
as those we have briefly outlined. But merely to sort plants into these
large groups does not tell us all we need to know about them. For all
plants not only belong to monocotyledons, or dicotyledons, or
gymnosperms, but also to smaller divisions of these groups. Just as
white men are divided into Englishmen, Frenchmen, etc., so there is the
greatest necessity of dividing our large plant groups into smaller and
more precise categories.

Some of the chief subdivisions of these large groups have been decided
upon the fact that a considerable number of plants in them have some
character in common, not found in the remaining plants of the group.
Among the monocotyledons, for instance, there is a large class of plants
that have tiny flowers between dry, chaffy scales, bear no true petals
or sepals, all wind pollinated and are all commonly, though incorrectly,
called grasses. These include, strictly speaking, two groups; one, the
true grasses in which the stem is mostly hollow and the fruit a grain,
while the other, with solid stems and bearing achenes for fruits, are
the sedges. The grasses form one family and the sedges another, but
while they differ in the characters just mentioned they agree in having
flowers of the same general type. Families of plants are thus groups of
genera, placed together in the scheme of classification, because they
are more like one another than like any other such group. Among the
grasses, for instance, are corn, wheat, rice, bamboo, orchard grass,
Kentucky blue grass, sugar cane, and hundreds of others, all belonging
to different genera, but all those genera grouped into a single family
because of their generally similar flowers. Just as the Kentucky blue
grass has a generic name (_Poa_) and a specific one (_pratensis_), the
families of plants must also bear names, usually derived from the
generic name of one of the chief genera in it. Because _Poa_ is a large
and important genus of the grasses, the family is named after it, with
the addition of _ceæ_. _Poaceæ_ is thus the family name of all the
grasses. Among the sedges one of the commonest genera is _Cyperus_,
including many species of the galingale or earth almond. From this genus
the sedge family has been named _Cyperaceæ_ (Figure 87). So the rose
family is the _Rosaceæ_, the violet family is _Violaceæ_, and so on
through all the three hundred or more families which contain all the
flowering plants so far discovered. Going back for a moment to the
_Poaceæ_ and _Cyperaceæ_, the fact that these two large families are
different from each other, but have some characters in common, fixes
them as both belonging to one _order_. Orders are thus groups of one or
more plant families, all differing one from another, but obviously
related and having some characters in common. The order containing the
grasses and sedges is named for one of the families in it with the
ending _ales_. Thus _Poales_ include _Poaceæ_ and _Cyperaceæ_. _Rosales_
include _Rosaceæ_ and several families.

In other words, individual plants are grouped in species, species into
genera, genera into families, and families into orders. These orders are
themselves grouped into still larger divisions; there are, for instance,
twelve orders comprising all the monocotyledons, and about twenty orders
comprising all the dicotyledons. Once we have decided that any plant is
a monocotyledon or a dicotyledon, our next step should be as to which
order it belongs, then its family, its genus, and finally its species.
Needless to say, such studies are necessarily of a technical nature, and
while the details of them lie outside the scope of this book, the
general plan or scheme of flowering plant classification is as we have
outlined it above.

This scheme of plant classification has been developed not only for our
convenience in sorting plants into definite categories, but more
important still to show, if possible, the relationships, and
particularly the development from the simplest to the most complex types
of plant life. Thus the monocotyledons begin with the cat-tails, which
have mere bristles for calyx and corolla, and lead by infinite
gradations to the showy and highly complex orchids, which are considered
the climax of the monocotyledonous families. While no general account of
the plant families can be attempted here, some of the more interesting
in both the monocotyledonous and dicotyledonous groups will be briefly
discussed.

SOME MONOCOTYLEDONOUS PLANT FAMILIES

Of the simple plants of this group the Grass Family, or _Poaceæ_ (Figure
86), is the most important, for in it are all our turf grasses, the
bamboo and sugar cane, besides scores of others. Over 4,500 species are
known, and they inhabit every region of the globe. The steppes of Russia
and our Great Plains are predominately grassy; in the wonderful bamboo
forests in the tropics are also woody representatives of this family.
Certain kinds in the tropics grow as vines, with great hooked spines at
the joints, so that nearly every kind of growth-form is to be found in
the _Poaceæ_. All agree in having very small flowers, arranged in tiny
spikelets, which are themselves grouped in various ways, although the
inflorescence is usually some form of spike, or raceme or panicle. The
individual flowers are between chaffy scales, of which several make up
each spike. Always the lowest two scales are empty, and the flowers
begin in the third from the bottom, or

[Illustration: FIG. 86.--BLUE-JOINT GRASS

(_Calamagrostis canadensis_)

FIG. 87.--WOOL GRASS

(_Scirpus Cyperinus_)

Fig. 86. Blue-joint grass, a common grass of North America and a member
of the _Poaceæ_. Fig. 87. Wool-grass, a tall swamp sedge popularly but
incorrectly spoken of as grass. It is a member of the _Cyperaceæ_ or
Sedge family, which have usually triangular solid stems, whereas grasses
have hollow round stems.]

sometimes even above that. The flower is so simple that there is neither
calyx nor corolla, only three stamens and one to three styles. The fruit
is a grain and the Poaceæ, therefore, are the chief source of cereals.
Wheat, rice, corn, oats, barley, millet, and rye, all come from grasses,
and all, except corn, are natives of the Old World. They were grown for
countless ages before the discovery of America, when Europeans first saw
corn used by the Indians. As they are wind-pollinated, the flowers of
grasses produce no honey nor colored petals, and the vast majority of
them have no odor. Most of them reproduce, not only by seeds, but by
rootstocks, and many of them grow so closely together that they form
turf. In nearly all of them the stem is hollow, and in the largest of
them, the bamboo, these hollow stems are used as water and sewer pipes,
especially in India. An exception to the hollow stem is the sugar cane,
from whose solid stem the juice is pressed out, that is the chief source
of sugar; and our common Indian corn.

[Illustration: FIG. 88.--SHOWY WAKE-ROBIN

(_Trillium grandiflorum_)

A plant of the lily family (_Liliaceæ_). Note the tendency to net-veined
leaves in a monocotyledonous plant. Such instances are common in nature
and net-veined leaves are found in certain species of smilax and most of
the plants of the Arum family, containing the jack-in-the-pulpit, both
monocotyledons.]

Much more highly developed than the grasses is the lily family or
_Liliaceæ_ (Figure 88), but comprising less than 1,500 species in about
125 genera. They are nearly always herbs, but the Spanish bayonet forms
a woody trunk, while the dragon tree of the Canary Islands is an
extraordinary plant for a lily relative, one giant specimen of this
being 80 feet tall and over 45 feet in circumference.[1] The flowers in
the _Liliaceæ_ are nearly always perfect, that is, stamens and pistils
are found in the same flower. Its perianth segments are nearly always
six, sometimes distinguishable as petals and sepals, but more often, as
in the tulip, all colored similarly. The fruits are practically always a
capsule that splits lengthwise. Perhaps the different plants in the
_Liliaceæ_, as well as any others, illustrate the fact that plants of
any particular family need not look like one another in order to be
included in the same family. Nothing could be farther from resemblance
than the bulb-bearing onion, the tulip, the Easter lily, the Spanish
bayonet, and the dragon tree. Yet they and hundreds of other plants
belong to the _Liliaceæ_. It cannot be overemphasized that it is flower
and fruit characters that determine inclusion in any plant family, and
similarity of leaves or habit may or may not accompany such characters.
Among other well-known plants in the family, which is found throughout
the world, are the crocus, the day lily, the dogtooth violet, hyacinth,
and colchicum and aloes used in medicine. Many of them produce bulbs,
such as onion, tulip, and lily and some of these contain valuable foods
and drugs. The great majority of them are insect fertilized and are
therefore wonderfully colored, and some furnish rich stores of honey.

But the most highly developed and interesting of all the
monocotyledonous plants are the orchids (Figures 89-92). This family,
_Orchidaceæ_,

[Illustration: FIG. 89.--ROSE POGONIA

(_Pogonia ophioglossoides_)

FIG. 90.--YELLOW-FRINGED ORCHID

(_Blephariglottis ciliaris_)

Fig. 89. Rose pogonia. A native bog orchid with purplish-pink flowers.
Fig. 90. Yellow-fringed orchid. A bog and meadow orchid of the eastern
United States.]

comprises over 6,000 species and many varieties, the overwhelming
proportion of which live in the tropics. Perhaps 90 per cent of them are
epiphytes, or air plants, which are perched high up on the branches or
bark of trees, and take all their food and water from the air. All the
native orchids of temperate North America grow in the ground, however,
and their food habits are unique. They depend for food upon a
microscopic organism found inside the roots of all orchids, and which
helps them to take in the food from the soil. So many of these orchids
are partial saprophytes, and without the associated organism they could
not grow. Almost uniformly the

[Illustration: FIG. 91.--WHORLED POGONIA

(_Isotria verticillata_)

FIG. 92.--ARETHUSA

(_Arethusa bulbosa_)

Fig. 91. Whorled pogonia. A woodland orchid with the leaves and flowers
whorled at the apex of the stem. Fig. 92. Arethusa. The most beautiful
of our bog orchids, with a fringed lip and pinkish-purple flowers which
bloom about Decoration Day. Note the highly irregular flowers in this
and Figs. 89-91.]

_Orchidaceæ_ have only a very few sheathing leaves, entirely without
marginal teeth, and some kinds are practically leafless. The flowers,
among the most gorgeous in the world, are always irregular in the sense
that there is no obvious series of sepals and petals. Both these are so
much transformed as to be nearly unrecognizable as such, but in some
orchids there appear to be three sepals. More often of the three inner
segments of the flower two are somewhat alike, while the third is quite
unlike them and is known as the lip; it is among the most variable of
any parts of the orchid flower. As adapted to insect visitors, the
flowers of orchids are the most wonderfully developed of all plants.
Because of their beauty and strange shapes, orchids have been much
sought after by collectors, and explorations of tropical, fever-ridden
forests have not infrequently ended in death to orchid hunters. New and
rare species of them are constantly being gathered by these collectors.
One expedition to New Guinea found over 1,000 kinds never before known,
and in the last few decades over 4,000 new orchids have been discovered.
For these plants orchid fanciers pay large sums, and a single plant of a
rare one sold in London at auction for over $500. The chances of
collecting such species made expeditions to the tropics frequent during
the latter half of the last century.

These three families, Poaceæ, Liliaceæ, and Orchidaceæ, are perhaps the
most important of all the monocotyledons, although commercially the
palms, or Palmaceæ, are extensively used. It is impossible to describe
or even mention all the monocotyledonous families, but a list of the
more important is added. The families are arranged in the order that
seems to reflect the development from simpler ones to the most complex,
and is the sequence of such families used by nearly all botanists in
describing the plant families of the world:

_Typhaceæ_--The cat-tails. Tall, reedlike swamp plants found throughout
the world. One genus and about ten species.

_Pandanaceæ_--The screw pines. Shrubs or trees with stout, woody trunks
and mostly prickly margined, long sword-shaped leaves. Confined to the
Old World tropics.

_Poaceæ_--The grasses. Noted above.

_Cyperaceæ_--The sedges. Grasslike plants with solid, often triangular
stems. Very often inhabitants of wet places. Throughout the world, Crex
rugs are made from a species of Carex, the largest genus in the family.
About 75 genera and 3,200 species.

_Palmaceæ_--The palms. All trees or shrubs, or sometimes climbing vines.
Includes the coconut and palm-oil trees, two palms of tremendous
economic importance. Inhabitants of tropical and warm regions, and only
very few found in the United States. Over 130 genera and 1,200 species.

_Araceæ_--The arums, of which the jack-in-the-pulpit is our best-known
native representative. They are nearly always herbs, often of giant
size, and the great majority are found in the tropical regions. Flowers
very minute, crowded together on a central column (the spadix), and this
often surrounded or having at its base a leaflike appendage (the
spathe). Calamus root and the skunk cabbage are also native
representatives. About 105 genera and over 900 species.

_Liliaceæ_--The lily and related plants, noted above.

_Smilaceæ_--Smilax. Mostly prickly vines; our native kinds often called
cat briers. Sarsaparilla comes from at least four species of _Smilax_.
Three genera and about 300 species, mostly natives of tropical, but a
few of temperate regions.

_Amaryllidaceæ_--The amaryllis family, noted chiefly for the sisal fiber
that comes from a species of _Agave_, which is one of the many different
kinds of century plant. The family has usually capsular fruits and black
seeds, and the narcissus and amaryllis of our gardens are well-known
members. About 70 genera and 800 species from tropical and warm
countries; a few in temperate regions, mostly herbs.

_Iridaceæ_--The iris, the source of orris root, and containing some our
most beautiful garden plants, the blue-eyed grass of fields, and over 50
genera and 100 species are found in this family. Nearly throughout the
world, and nearly all herbs.

_Musaceæ_--The banana and traveler’s-tree. Giant herbs, in the banana
having the largest leaves known, frequently twelve feet long and two
wide. Natives of tropical and warm regions, and 4 genera and 75 species
are known. Flowers often very irregular, and in _Strelitzia_ gorgeous.

_Orchidaceæ_--The orchids, already noted.

While there are many thousands of plants contained in these
monocotyledonous families and in the others not mentioned here, they
make up only about one-third of the total number of different kinds of
plants known in the world. But in grasses and sedges, in the rushes and
a few other families, the number of individuals is greater than in
probably any other plant family.

DICOTYLEDONOUS PLANT FAMILIES

All the great bulk of the flowering plants not included in the
monocotyledons or the gymnosperms belong to about two hundred plant
families that are included in the dicotyledons. In all of them the seed
sends up two seed leaves, there are generally netted-veined leaves and
the parts of the flower are in fours or fives or multiples of these
numbers. In such a large aggregation of plant families there are three
well-marked divisions, namely, those that bear no petals or sepals,
those that do bear them and where they are separated to form individual
sepals or petals, and those where the petals are united to form some
sort of a tubular or at least connected corolla. These divisions are
perhaps best shown thus:

(_a_) _Apetalæ_--Including families where the petals are never present,
and in some there is even no calyx. Examples: walnut, hickory, willow,
and oaks.

(_b_) _Polypetalæ_--Petals present but separate, not forming a tubular
or connected corolla. Examples: buttercup, rose, pea, apple, geranium.

(_c_) _Gamopetalæ_--Petals united and forming some sort of a tubular or
connected corolla. Examples: garden primrose, gentian, salvia, mint,
snapdragon, and the daisy family.

Any attempt to describe the families contained in these three divisions
of the dicotyledons would take all the rest of this book and crowd out
other things about plant life that must not be omitted. All that can be
done here is to outline briefly a few families in each division so that
we shall have fixed in our minds what the general principles of plant
classification are and how these are illustrated by well-known plants.
There are many books that deal with this subject in great detail and to
them the student should go for further elaboration of the subject. It is
one of the most interesting phases of the study of botany, but it
demands a longer and more intensive study than can be included here.

(_a_) _Apetalæ_--These include families of plants that are the simplest
in structure of all the dicotyledons. In all of them there are no petals
and in some both petals and sepals are lacking, leaving only essential
organs. Taking first those families that have neither petals nor sepals
we find that most of them bear their flowers in catkins, a flower
cluster familiar enough in the pussy willow. Some of these families are
the following:

_Juglandaceæ_--Trees with compound leaves, flowers in catkins and fruits
inclosed in a thick husk. Examples: walnut and hickory. Six genera and
over 30 species.

_Salicaceæ_--Shrubs or trees with simple leaves, flowers in catkins and
capsular many-seeded fruits, but no nuts. Containing only willows and
poplars. Two genera and over 200 species. (Figure 93.)

_Myricaceæ_--Shrubs or trees with simple usually fragrant leaves,
flowers in catkins and fruits one-seeded. The bayberries. Two genera and
about 35 species. (Figure 94.)

[Illustration: FIG. 93.--PRAIRIE WILLOW

(_Salix humilis_)

The _Salicaceæ_, consisting only of willows and poplars, are always
woody plants bearing their flowers in catkins.]

These and some other families of close relationship are the least
developed, in their flower structure, of any of the dicotyledons. All of
them bear only the essential organs of reproduction in their very simple
flowers. In the walnuts and hickories the different sexes are in
different flowers on the same plant, in the willows they are even on
different plants, and in Myricaceæ they are often found both ways. All
of these flowers are wind-pollinated, so that they bear no honey,
usually have no odor, and of course their need for showy petals for
attracting insects is nil, although some pollen-eating insects visit
them.

[Illustration: FIG. 94.--SWEET FERN

(_Comptonia peregrina_) belonging to the _Myricaceæ_.

These are usually aromatic, always woody plants, of which several
species besides sweet fern grow in the United States.]

Somewhat higher in the scale of plant life are those families that,
while still lacking petals, do have sepals. Their flowers are for this
reason much better protected against rain or other inclement conditions,
which means that they are so much the more likely to reproduce their
kind. At least two of these slightly more developed families cling to
the habit of bearing some of their flowers in catkins, however. Other
families are also found in other parts of the world, but in North
America this group is represented by:

[Illustration: TRANSPLANTING RICE IN JAVA

(_Courtesy of Brooklyn Botanic Garden._)]

[Illustration: A TEA ESTATE IN CEYLON

(_Courtesy of Brooklyn Botanic Garden._)]

_Betulaceæ_--The birch, alder, hazelnut, and hornbeam. Both staminate
and pistillate flowers in catkins. Fruit a small one-seeded nut or a
winged samara in the birch. All wind-pollinated. Six genera and about
seventy-five species, nearly all from north temperate zone.

[Illustration: FIG. 95.--LOW BIRCH

(_Betula pumila_)

A bog shrub of the _Betulaceæ_ or birch family. Most of them are tall
trees with both male and female flowers in catkins.]

_Fagaceæ_--The oaks, beech, and chestnut. All trees or shrubs with at
least their staminate flowers in catkins. Fruit inclosed in a bur
(chestnut and beech) or borne in a cup (the acorns of oaks). At least
five genera and about 375 species, widely distributed.

The habit of bearing some or all their flowers in catkins which flower
usually before the leaves appear, and of having such flowers wholly at
the mercy of precarious winds, is, if not lost, at least much less
frequent in the remaining families of the apetalæ. All the others, while
still without petals, do have sepals and some of these are colored so
that insect visitors are likely. There are too many of these families to
be enumerated here, but two of the chief are:

_Ulmaceæ_--The elms and hackberry. Trees or shrubs with minute greenish
or yellowish flowers crowded in small clusters or in spikes. Fruit a dry
nut or one-seeded and winged; or in the hackberry a drupe, one of the
first evidences of even a slightly fleshy fruit in the dicotyledons.
About 13 genera and 140 species, widely distributed.

_Polygonaceæ_--The buckwheat, knotweeds, common dock, and many other
genera. Sepals often colored white or pink so the flowers are sometimes
at least insect-pollinated. Flowers small and crowded in various
clusters, often in a spike. Fruit an achene, a dry fruit familiar enough
in the buckwheat. About 40 genera and over 800 species, mostly herbs or
vines here, but often trees in the tropics.

From here on plant families leave, with some exceptions, the greenish or
otherwise inconspicuous flower color, and somewhere about here they
begin to rely more upon insect fertilization for the perpetuation of
their kind. None of those so far mentioned have any petals to their
flowers, but in the pink family or Caryophyllaceæ we find the first
evidences on any considerable scale of the presence of sepals and
petals, the latter usually beautifully colored. Familiar representatives
of this family are the pink, carnation, chickweed, corn cockle, and the
stichwort. There are over 50 genera and 1,000 species, nearly all in
temperate regions.

The apetalous families appear to show a development from catkin-bearing
trees with the sexes separated, and with neither petals nor sepals,
through the Polygonaceæ, with often colored sepals, and the beginnings
of insect fertilization. In Caryophyllaceæ, the most highly developed of
them all, there are, besides the sepals, often or usually petals, and
the reliance on insect fertilization is nearly complete. There are many
transitional stages which cannot be included here, but they show step by
step the development of the apetalous families from perfectly naked
reproductive organs to the next larger group, the polypetalæ, where the
process of increasingly complex flower development will now be sketched.

(_b_) _Polypetalæ_--In this large group of plant families the petals are
free and quite separate, but as if they had not yet lost all the
characters of the apetalæ, some families show incompletely the general
characteristics of their more stable neighbors. There are, for instance,
no petals in many species of the buttercup family, none in the sweet-gum
tree nor in the maples, and a few others. But in spite of occasional
exceptions this large group of polypetalous families do usually bear
separate petals and sepals, and are among the most important of all the
plant families. As they number over a hundred and contain thousands of
species, all that can be done here is to mention a few typical or
important ones. Just as in the apetalæ the families in this large group
appear to show definite stages in development from simpler to more
complex forms. But the steps are harder to trace and what appears
simple characters in some plants are very complex in others.

While all the families in this group have separate petals some of them
show a tendency to have united sepals, a character of perhaps some
advantage and certainly very common among the still more developed
gamopetalæ. Some of the families that have separate sepals agree in
having the stamens inserted below the ovary. Of these the following
three families may serve as types.

_Nymphæaceæ_--The water lilies. Aquatic plants with usually large showy
flowers in which the calyx, corolla, and stamens often merge one into
the other so that it is sometimes difficult to know where one series
ends and the other begins. Five genera and 45 species throughout the
world.

_Ranunculaceæ_--Buttercup family. Includes buttercups, clematis,
columbine, meadow rue, golden seal, marsh-marigold, hepatica, and scores
of other native plants. All herbs, except a few semiwoody vines like
clematis. Sepals always present, and where no petals are found, as in
marsh-marigold, colored like them. Highly irregular flowers are not
uncommon, as in columbine and monkshood. The fruits are berrylike in
some genera and in others dry capsules. Thirty-five genera and over
1,000 species throughout the world, but most abundant in temperate
regions.

_Lauraceæ_--Laurel or sassafras family. Includes besides them the guava
and cinnamon and camphor trees, all tropical, and the native spice-bush.
All trees and shrubs with small, yellow, or greenish-yellow flowers and
usually aromatic juice. Fruit a one-seeded drupe or a berry. About 40
genera and over 1,000 species, nearly all tropical, but a few in the
United States.

At this point, in the sequence of plant families, there are two or three
families that bear quite different fruits than any heretofore noted, and
in one of them, at any rate, the four petals are in the form of a cross.
So uniformly is this true that the family was for years known as the
Cruciferæ, but is better known as Brassicaceæ, from _Brassica_, the
generic name of the mustard. This large mustard family mostly has fruits
known as a silique or silicle, which are pods that split into two
valves; and yellow or white, rarely pinkish flowers. The juice is always
somewhat acrid, familiar through the pleasant pungent taste of
water-cress, but none of the family is poisonous. There are over 200
genera and nearly 2,000 species of wide distribution, and common
representatives include the cress, mustard, horse-radish, garden stock,
sweet alyssum, cabbage, cauliflower, brussels sprouts, radish, and
turnip.

Between the Brassicaceæ and the following families there are many others
that cannot be mentioned here. Somewhat farther along in the sequence
are a group of families, large and important, and all having their
stamens inserted around or even above the ovary, and in which the sepals
are partly or wholly united. They include some of our most beautiful
flowers and useful fruits. Of the many closely related families that
agree in these characters the two most important are:

_Rosaceæ_--Rose family. In the broad sense including, besides the rose,
the strawberry, blackberry, apple, pear, peach, plum, besides many herbs
with wholly dry fruits. There are always five petals, five lobes to the
partly united calyx, but numerous stamens. They may be herbs, shrubs,
or trees, with simple or compound leaves, but these are nearly always
alternately arranged. There are over 100 genera and nearly 2,000
species. Because of the size of the Rosaceæ and differences in fruit,
the apple and its relatives are often included in a separate family, the
Malaceæ (Figure 96), and the peaches and plums in Amygdalaceæ. The
general structure of the flower is sufficiently uniform, however, for
them all to have been included in Rosaceæ (Figure 97).

[Illustration: FIG. 96.--WASHINGTON THORN

A prickly shrub related to the apple, which, with the plums, cherries,
pears, strawberry, blackberry and hundreds of other plants are all
grouped in the _Rosaceæ_ or rose family.]

_Papilionaceæ_--Pea family. A large family having characteristic pealike
flowers, a description of which has already been given in Chapter I.
They all bear legumes, a pod that splits down one side, not both, as in
Brassicaceæ. Besides the pea, the bean, vetch, alfalfa, lentil, locust
tree, and dozens of valuable timber trees in the tropics belong here.
Flowers all showy and absolutely dependent upon insects for
fertilization. Seeds highly nutritious in many genera, and the roots of
nearly all have bacteria associated with them. (See chapter on Food
Habits of Plants.) Three hundred and twenty-five genera and over 5,000
species of wide distribution, but most frequent in the tropics.

[Illustration: FIG. 97.--THIMBLEBERRY

(_Rubus odoratus_)

A bristly shrub of the Rose family common in rocky places in eastern
North America.]

There are many other smaller families in different parts of the world
which hover, as it were, about these two giant plant families that make
definite landmarks in the scheme of plant classification. The character
of having partly united sepals and numerous stamens inserted around, or
even above the ovary, give to all the flowers of the Rosaceæ and related
plants a general family resemblance that is very striking. The pea
family, and its relatives, also have flower and fruit characters of
remarkable uniformity, considering the tremendous number of species.

From this point on to the end of the polypetalæ there are scores of
plant families, all agreeing in having a compound ovary, that is, one
that is more than one-celled, and in also having quite distinct and
separate sepals. Their agreement in these characters, however, ends all
other evidences of relationship, and it is beyond the scope of this book
to go into the details of each, or even a few of them. A list with some
brief notes on those most important must suffice here.

_Geraniaceæ_--Geranium family. Includes also the common garden as well
as the wild geranium. Fruit splitting into five parts. Leaves always
divided or even dissected; 12 genera and 470 species, all herbs.

_Anacardiaceæ_--Includes the tree of heaven, sumac, poison ivy, and in
the tropics, the mahogany, all trees, shrubs, or vines; 60 genera and
500 species, mostly in the tropics.

_Malvaceæ_--Mallow family, including, besides the marshmallow, the rose
of Sharon, and cotton. They all have the stamens united into a column or
tube which surrounds the style. About 40 genera and 900 species of
herbs, shrubs, or trees of wide distribution.

_Cactaceæ_--Cactus family. Nearly all desert plants, with no leaves or
practically none, and greenish stems that function as leaves and also
store water. Of the greatest variety of form and always bearing numerous
petals and fleshy fruits, of which the prickly pear is familiar enough.
Of 40 genera and over 1,000 species, all, but a handful, come from North
and South America.

_Umbelliferæ_ (often called _Ammiaceæ_)--The climax of the polypetalous
families, and nearly always bearing flowers in umbels. There are usually
many flowers, sometimes several hundred in each cluster. Familiar
examples are parsley, celery, parsnip, Queen Anne’s lace, and many
others. The seeds often contain an aromatic oil, as in caraway, and some
are violently poisonous, as the water hemlock. About 250 genera and over
2,000 species, all herbs, widely distributed, but most common in
temperate regions.

We have seen from the foregoing the probable development of
dicotyledonous plants from those simplest ones, where, as in the pines,
there is merely a naked ovule between scales, through the catkin-bearing
trees, without petals or sepals, and all wind-pollinated, to families
where just an inconspicuous and, subsequently, a colored calyx is found,
and after this the dawn of those plants that have complete and perfect
flowers. Among the latter all those so far noted have separate petals,
but after the Ammiaceæ, or carrot family, there appears a new character,
setting off practically all other dicotyledonous plants from those
already treated. This new character--and hints of it are found before it
reaches the perfection found in the subsequently described families--is
that of the petals being united to form some sort of a connected or,
more often, a tubular corolla. The petals are represented merely by the
lobes of the corolla, mostly four or five, and in many families of this
group, known as the gamopetalæ, literally, united petals, this tubular
corolla is irregular and often beautifully formed. In salvia, for
instance, there is a hoodlike upper part overhanging the lower tubular
part. Other familiar examples of these irregular corollas are the garden
snapdragon, Oswego tea, skullcap, pentstemon, and many others.

(_c_) _Gamopetalæ_--The earlier families among those generally having
united petals seem not yet quite sure of their new character, for a few
of them hark back to the condition of having, in some genera, quite
separate petals. One of the first families in this series, the Ericaceæ
(Figure 98), or heath family, has several genera in which this is true,
notably in the Labrador tea and the sand myrtle among native plants, and
some foreign relatives. The Ericaceæ are almost exclusively shrubs or
trees, but some of our native sorts, such as trailing arbutus and
wintergreen, are practically herblike, although they are, strictly
speaking, woody plants. The family is remarkable for containing
beautiful flowered garden plants, such as the hundreds of species of
South African heaths, the heather, the azaleas and rhododendrons, and
our beautiful native Rhodora, about which Emerson wrote one of his most
beautiful poems. The flowers in the heath family are often perfectly
regular and bell-shaped, but sometimes irregular, as in azaleas and
several other genera. Nearly all the family rely on microscopic
organisms to get their food, and some close relatives, like the Indian
pipe, are saprophytes. There are over 70 genera and 1,200 species widely
distributed. Central Asia is the home of most rhododendrons and azaleas,
scores of species being found in the upper reaches of the Himalayas.

The Ericaceæ are typical of many families in the first group of the
gamopetalæ, in that all of them, with a few exceptions like the
cranberry, have a superior ovary. That is, the petals and sepals arise
from the base or below the ovary, and consequently the mature fruit in
such plants is never crowned with the remains of the withered calyx, as
blueberries always are and all other gamopetalæ that have an inferior
ovary. The character of having an inferior or superior ovary separates
the gamopetalæ into two large groups of families, the heath family and
many others, with superior ovary, and a few but numerically very
important families that always have an inferior ovary.

[Illustration: FIG 98.--SWAMP AZALEA

A shrub of the _Ericaceæ_, with white or pink sticky flowers and dry
capsular fruits.]

Taking first the families that all have a superior ovary, we must, for
lack of space, exclude most of them from here. A few of the most
important, or typical, after the Ericaceæ, are:

_Primulaceæ_--Primrose family. All herbs in which the stamens are as
many as the lobes of the corolla and inserted on them. The flowers are
quite regular. They all have some form of a capsule for fruit, which in
most generally split lengthwise. Familiar examples include the garden
primrose (not the wild evening primrose), yellow loosestrife, the star
flower, pimpernel, shooting star, and the beautiful cyclamens. A few
members of the family are slightly luminous in the dark, apparently an
attraction to night-flying insects. About 28 genera and over 400
species, mostly from the northern hemisphere, a few in temperate South
America and South Africa.

_Gentianaceæ_--Gentian family. Over 700 species in 70 genera, all bitter
herbs, with opposite leaves, quite without teeth and beautiful,
sometimes fringed, always regular flowers. In this and related families
the stamens are of the same number as the lobes of the corolla, and
always alternate with them. Gentian and sea or marsh pinks are our
best-known native representatives, while some related plants are
medicinal.

There are many other families in this part of the scheme of plant
classification that have minor differences among themselves, but agree
pretty generally in the number and position of their stamens, their
superior ovary, and, on the whole, in the regular flower. Irregular and
regular flowers may be recognized at once by cutting them lengthwise
through the middle. In regular flowers there would be as much on one
side as on the other of the dividing line, and in irregular ones quite
obviously more on one side than the other. The character of all the
genera in a family having irregular flowers begins to occur here with
greater and sometimes exclusive frequency. In the mint family, or
Lamiaceæ, nearly all of its 160 genera and over 3,000 species have
two-lipped or irregular flowers. The garden salvia well illustrates the
type.

The _Lamiaceæ_ or Labiatæ, as they are often called from the two-lipped
corolla, are herbs locally, but in the tropics often shrubs or trees.
Almost universally they have four-sided stems and opposite leaves
without stipules. The flowers may be solitary, much more often they are
crowded into various kinds of clusters. The four stamens are borne on
the corolla tube, and nearly always there are two long and two short
ones. The family is universally fertilized by insects, and some of the
flowers are wonderfully adapted for this end. Common examples, besides
the salvia, are mint, thyme, skullcap, hyssop, bugle, blue curls,
catnip, hedge-nettle, coleus, and Oswego tea. Most of the genera contain
heavy odorous oils in their foliage, from which oil of mint, pennyroyal,
lavender, rosemary, marjoram, savory and balm are the best known. These
volatile oils give to members of the family their characteristic and
often very beautiful odors.

There are many other families of plants, some with irregular and others
with regular flowers, that appear to group themselves around the
Lamiaceæ, all of which agree, in spite of individual differences, in
having a superior ovary. The remaining families of the gamopetalæ,
however, always have an inferior ovary, usually obvious by the insertion
of petals above the ovary, and in the fruit often conspicuous by the
remains of the withered calyx still clinging to the top of the fruit.
Only two of the scores of families, with inferior ovary and gamopetalous
corollas, will be mentioned here, both of which are important.

_Rubiaceæ_--Madder family. Common examples are the creeping bedstraw,
the sweet woodruff, partridge berry, button bush, and bluets or
quaker-ladies. All, except one of these, are herbs, but in the tropics
the Rubiaceæ are nearly all shrubs or trees. Among those are the coffee,
quinine, and ipecac. All the family have opposite leaves (a few
verticillate) and stipules, regular flowers, with stamens as many as
the corolla lobes, and alternate with them. The fruits are a drupe,
berry, or capsule. Over 340 genera and 6,000 species are known almost
throughout the earth.

_Compositæ_ or _Carduaceæ_--The daisy family and the largest and most
complex of all the plant families. As the culmination of the scheme of
plant classification, they show the greatest perfection in the
arrangements for cross-fertilization. For a description of their flower
structure, see Chapter I, page 44, and Figures 43-45. Some of the
Compositæ have no ray flowers, others are all ray flowers, but the great
bulk of them bear both tubular and ray flowers in a single head. This
may be single, or more commonly it is arranged in various kinds of
clusters. Each head is surrounded at its base by one or more series of
usually tightly overlapping bracts, incorrectly called a calyx by the
unobservant. The Compositæ include over 900 genera and 11,000 species
from all parts of the world. Most of them in America are herbs. Daisy,
dandelion, dahlia, chrysanthemum, sunflower, boneset, chicory, lettuce,
and scores of other examples could be cited, all herbs. In the tropics
the Compositæ are more often trees and shrubs. The family contains many
economic plants such as arnica, chamomile, artichokes, inula, and many
others.

This all too brief account of the grouping of plants in families, and
the sequence of these from the comparatively simple naked-seeded pines,
through monocotyledons, the apetalous dicotyledons, followed by the
polypetalous dicotyledons, and culminating in the Compositæ among the
gamopetalous families, gives us merely a hint of what are the characters
upon which plants are divided. While the details are necessarily
omitted, the gradual development from naked-seeded plants, wholly at the
mercy of the elements, up to those which are marvelously provided with
contrivances to insure cross-fertilization, has been traced. Perhaps no
other phase of botanical study offers such a rich opportunity as this,
for upon the solution of some of the problems of plant classification
depends the answer to many questions about the history of the earth and
man’s ability to live on it. Certain of these plant families have lived
on the earth hundreds of thousands of years before man first came.
Others have apparently arisen comparatively recently. Many botanists
believe that all the monocotyledons should be placed after the
dicotyledons, as the latter may be a more ancient type than the former.
How these different plant structures, some very ancient and others more
recent, help to show us some of the history of the earth, will be
treated, among many other evidences of a plant nature, in the chapter on
“The History of the Plant Kingdom.”

CHAPTER V

USES OF PLANTS TO MAN

For perhaps the largest number of readers the chief value of plants is
what they furnish in the way of food, clothing, fuel, and so forth, and
from this standpoint alone the study of them is more than worth while.
It is unnecessary here to enumerate all the thousand and one things that
we get from plants, and no attempt will be made to do so in the
following pages. But certain plants like wheat, corn, cotton, jute,
rubber producers, and tobacco have so shaped the life of the people, so
absolutely dictated the development of whole regions of the earth’s
surface that their stories are part of the history of mankind. What our
cotton fields of the South, the wheat and corn fields of the Middle
West, the jute in India, and the coconut palm and sugar cane in the
tropics have done to dictate the economic destiny of those regions is
common knowledge. Hundreds of less important plants throughout the world
contribute their quota to the huge debt that man owes to the plant
world. Probably no other feature of plant life offers such attractions
as the study of man’s uses of plants, which is known as Economic Botany,
and for which our Government maintains a large staff of experts. Some of
the publications of this bureau are textbooks of the greatest value to
those who grow or import plants or their products. What that amounts to
in the aggregate no one can readily estimate. It certainly exceeds all
other commerce combined.

1. FOODS

Those early ancestors of ours that roamed over northern and central
Europe between the periods of ice invasion, which at times made all that
country uninhabitable, tell us by the relics of them found in caves that
agriculture was then unknown. Living mostly by the chase and on a few
wild fruits picked from the forest these half-wild and savage people
wandered wherever game was plentiful and the continental glacier would
permit. But there came a day when one of these races began the
cultivation of some of the wild plants about them and with that day
dawned the real beginning of man’s use of plants. And with that day also
these simplest of our ancestors stopped their wanderings in large part
and became farmers, albeit very crude ones, as their primitive stone
implements show. They did not give up the chase, but their collection
into more or less permanent camps or villages began with their
cultivation of plants. Just when this happened no one can say, but most
estimates of the time since the last ice age indicate that it could not
have been much less than forty thousand years ago. And considerably
before this, and long before the use of metals by man, we find these
stone implements of agriculture and the probable beginnings of that
great reliance upon plant life which the modern world has carried to
such tremendous lengths. Unfortunately we do not know what plants these
“Men of the Old Stone Age” grew in their primitive gardens, and it is
thousands of years after this, and after man’s discovery of the use of
metals, that we know definitely what plants he grew and how he used
them. Unquestionably some of the early uses of plants, such as dyes for
the face or for “rock pictures” are very ancient and are found long
before any sign of agriculture, but as food in the sense of being
produced food rather than that gathered from the wild, there are only
the faintest traces until, in the remains of the lake dwellers in
Austria, a single grain of wheat was discovered. Their metal instruments
showed them to have been familiar not only with this, but with other
plants, and it is well to remember that these people lived far longer
ago than our most ancient historical records such as the Egyptians or
Chinese. Both the latter, so far as our oldest records of them show,
were an agricultural people who had enormously developed man’s uses of
plants as compared with the men of the stone or bronze ages, whose
agriculture must perhaps forever be a secret of the past.

WHEAT

The discovery of the grain of wheat in the remains of the lake dwellers
tells us some things about men’s travels even in those early days, for
wheat is not a wild plant there and must have come to central Europe
from a great distance. Researches upon the home and antiquity of wheat
are not very definite, but its occurrence as a wild plant somewhere in
Mesopotamia or the vicinity appears to be indicated. The Chinese grew it
2700 B.C. and the earliest Egyptians spoke of its origin with them as
due to mythical personages such as Isis, Ceres, or Triptolemus. From its
ancient and perhaps rather restricted home it has gone throughout the
temperate parts of the earth and now forms perhaps the most important
source of food. Although many different kinds of wheat are raised in
different parts of the world most of them have been derived from one
wild ancestor, _Triticum sativum_. Forms known as hard and soft wheat
and dozens of others suited to different regions or market conditions
have been developed by plant breeders. As the most important of all the
cereals it has been much studied, and its cultivation in America is on
such a tremendous scale that we furnish a large part of the world’s
supply. Russia, Argentina, and the southern part of Australia also raise
large quantities. The plant is a grass and the “seed” is really a grain
or fruit in which the outer husk tightly incloses the true seed.

It were perhaps well to note here that popular stories about the
germination of grains of wheat taken from Egyptian mummies are not true.
Wheat and even corn are sometimes given to travelers, and it is taken
from these ancient Egyptian tombs. But it was not put there by the early
Egyptians, as the presence of corn proves only too well. For this cereal
is an American plant unknown before Columbus and 1492. Arabs and others
have recently inserted various seeds in these mummies, some of which
undoubtedly have germinated--hence the fable. The early Egyptians did
put seeds in their mummy cases, but none have ever germinated.

INDIAN CORN OR MAIZE

The grass family furnishes this second most important cereal to all
Americans and Europeans, although among inhabitants of tropical regions
rice is perhaps more important than either wheat or corn. With the
discovery of America the early travelers found the North American
Indians, the Mexicans, and the Peruvians all growing corn and using it
on a considerable scale. It must have been grown for hundreds of years
before that time, as its wide distribution and many varieties testified
even at that date. Its true home nor its actual wild ancestor has never
been certainly determined, but a wild plant very closely related to our
modern corn is found in the northern part of South America, and either
there or in Central America is apparently the ancient home of corn. So
much had corn entered into the life of the early Mexicans that the first
Europeans to visit that country found the Mexicans making elaborate
religious offerings to their corn goddess. And, as in Egypt, the tombs
of the Incas of Peru contain seeds of the cereal most prized, which in
the case of corn consists of several varieties. While their civilization
is not as old as certain Old World races, the cultivation of corn must
date back to the very beginnings of the Christian era. It is now spread
throughout the world in warm regions, and as early as 1597 it was grown
in China, a fact that led to the erroneous notion that China was its
true home. Perhaps no fact is more conclusive as to its American origin
than that corn belongs to a genus _Zea_, which contains only the single
species _mays_, with perhaps one or two varieties, and that until the
discovery of America _Zea mays_ or Indian corn was unknown either as a
wild or cultivated plant. Such an important cereal, if it actually were
wild in the Old World, would have spread thousands of years ago as wheat
did, and Columbus and his adventurous successors would not have brought
from the New World a food that has since become second only to wheat.

Field corn of several different sorts, pop corn, and sweet corn were all
developed by the Indians from the ancient stock, but comparatively
recently the juice of the stem has been used for making corn sirup. The
use of the leaves for cattle feed is known to all farmers, and from its
solid stems it is now likely that some fiber good for paper making will
be extracted.

RICE

Both wheat and corn are grasses that are cultivated in ordinary farm
soils, but rice is derived from a grass that is nearly always grown for
part of its life in water. It is taller than wheat, but not so tall as
corn, and its wild home is in the tropical parts of southeastern Asia.
It is still grown there in greatest quantity, and in the Philippines,
while only a small part of the world’s supply comes from the New World.
There are perhaps more people that rely upon rice for food than upon
wheat and corn combined. It still is the principal article of diet of
the inhabitants of China, Japan, India, and dozens of smaller Old World
regions, while its use as a vegetable in tropical America is practically
universal. A considerable part of the starch manufactured in Europe
still comes from rice, and in India the intoxicating beverage arrack is
made from it. The Japanese saké, a sweetish intoxicating liquor, is also
made from rice. Notwithstanding its wide use it is not as nutritious as
wheat or corn, being much lower in proteins than either of them.

More than 2800 years before Christ the Chinese cultivated rice, for at
that time one of the emperors instituted a ceremony in which the grain
plays the chief part. It has been grown on land useful to almost no
other crops as it is usually subject to inundations. Some varieties,
however, have been developed which will grow on uplands and these are
grown even on terraced land both in China and the Philippines. It needs
a heavy rainfall, however, and grows best in lands that are flooded. It
is occasional dry seasons that produce the famines of India when the
crop fails. The botanical name of rice is _Oryza sativa_, and it is
known now as a wild plant in India and tropical Australia. Its
introduction into Europe must have been long after wheat, for rice is
not mentioned in the Bible, and was unknown in Italy before 1468, when
it was first grown near Pisa. Rice paper, which some people think is
made from this grain, comes from the pith of _Aralia papyrifera_, a tree
of the rain forests of Formosa, related to our temperate region
Hercules’-club.

SUGAR

In the chapter on what plants do with the material they take from the
air and soil we found that sugar was one of the first fruits of that
process. In at least two plants the overproduction of sugar is on such a
great scale that our chief supplies of this substance now come from
these two plants--the sugar cane, which is a tall grass, and the sugar
beet. Hundreds of other plants produce surplus sugar, but for commercial
purposes these two, and the sap of the sugar maple (_Acer saccharum_),
are our chief sources of supply.

Cane sugar is an Old World grass known as _Saccharum officinarum_,
frequently growing twelve feet high, and with a solid woody stem, quite
unlike our ordinary grasses. It looks not unlike corn on a stout stem,
and it is the stem which is cut and from which the sweet juice is
pressed out between great rollers. The pressed-out juice goes through
various processes in the course of which first molasses, then brown
sugar, and finally white granulated sugar are produced.

Our consumption of sugar is now on such a scale that we scarcely realize
that before the days of Shakespeare it was very scarce and expensive.
Even as recently as 1840 it regularly sold in England for forty-eight
shillings per hundred pounds, wholesale. At that time the total
consumption in the world was only slightly over a million tons, while
to-day it is over fifteen times that amount. The plant is native in
tropical Asia, but just where is not known, nor are wild plants found in
any quantity. It has been much modified by long cultivation, and has
been reproduced by root-stocks for so long a period that it is rare for
the plant to bear flower and seed. It has been known in India since
before the Christian era, and was taken from there to China about 200 B.
C. Neither the Greeks nor Romans knew much about it, nor do the Hebrew
writings mention it. Somewhere in the Middle Ages the Arabs brought it
into Egypt, Sicily, and Spain. Not until the discovery of the New World
was it cultivated on any considerable scale, when the climate of Santo
Domingo and Cuba and the African slaves imported to those islands
afforded conditions that resulted in Cuba at least being one of the
world’s chief sugar-producing countries. Sugar cane is now grown all
over the earth in regions with a hot, moist climate, India and
neighboring countries producing over half the world’s supply.
Practically all the sugar produced in India is used there, however, so
that the American tropics furnish to Europe and America about one-third
of the world’s total consumption of cane sugar.

In 1840 under fifty thousand tons of beet sugar were produced, while in
1900 more sugar from this plant was made than from sugar cane.
Considerably more than half this beet sugar was grown in three
countries, Russia, Austria, and Germany, which explains what the great
war has done to the sugar market. The plant from which beet sugar is
derived is botanically the same as the common garden beet, _Beta
vulgaris_, which is wild on sandy beaches along the Mediterranean and
Caspian seas, and perhaps in India. Much cultivation has made this
slender-rooted plant into the large-rooted vegetable we now have and its
sugar content was much increased by Vilmorin, a French horticulturist.
Many garden varieties are known, and some of these are grown in the
United States, where beet sugar is produced, although in 1910 less than
half a million tons were made here as against over four million tons in
Europe. While the beet as a vegetable was known perhaps a century or two
before the time of Christ, it was not until 1760 that its sugar content
was understood, and it was nearly eighty years later before beet sugar
became commercially important. Its cultivation in England on any
considerable scale did not begin before the beginning of the present
century.

THE BANANA

Among the largest herbs in the world are the ordinary banana plants, now
cultivated throughout the tropical regions, but originally native in the
Malay Archipelago. From there it spread into India, and the early
Greeks, Latins, and Arabs considered it a remarkable fruit of some
Indian tree. It is actually a giant herb with a tremendous fleshy stem,
formed mostly of the tightly clasping leaf bases, the blade of which is
frequently ten to twelve feet long. In nature the blade splits into many
segments due to tearing by the wind, a process that the plant not only
tolerates but aids. The leaf has a thinner texture between its principal
lateral veins, and along these weaker parts the leaf tears so that
normal plants are usually almost in ribbons. The leaf expanse, without
this relief, is so great that tropical storms would doubtless destroy
the plant.

Many wild species of the banana are still found in tropical Old World
countries, the genus _Musa_ to which the banana belongs having over
sixty-five species. There are at least three well-marked types of banana
used to-day, two of them, our common yellow one and a smaller red sort
being fruits of almost universal use. The remaining type is usually
larger than the kinds sent to northern markets, is picked and used while
still green and is always cooked before using, usually boiled as a
vegetable. In this form it is known as the _plantain_, and is a good
substitute for the potato in regions where the latter cannot be grown.
Plantains are used on a large scale in all tropical countries, much more
so than the yellow and red bananas which are familiar enough in northern
markets. These are too sweet to be used as a staple diet, and the
plantain is practically the only such diet which millions of the poorer
people in the tropics ever get. There is almost no native hut but has
its plantain field.

The flowers of the banana plants, all of which appear to be derived from
the single species _Musa sapientum_ or possibly also from _Musa
paradisiaca_, are borne in a large terminal cluster which ultimately
develops into the “hand” of bananas familiar in the fruit shops. The
plant then dies down and a new one develops from a shoot at the base of
the old stem. For countless ages this has been the only method of
reproduction, and usually the banana produces no seeds. The plant is
easily grown in greenhouses, one in the conservatory of the Brooklyn
Botanic Garden producing 214 pounds in a single cluster consisting of
300 bananas.

POTATO

Sir Walter Raleigh is usually credited with the introduction of the
potato into Europe, although it appears as though the Spaniards were the
first to bring the plant from America. It was brought to Ireland in 1585
or 1586 and from its wide use there became known as the Irish potato.
Its native home is in southern South America, and although Columbus did
not mention it after his first and second voyages, subsequent Spanish
adventurers found natives on the mainland making extensive use of it.
There are now several wild relatives of it in South America, but their
tubers are not so large as those of _Solanum tuberosum_ from which all
the different varieties of potato have been derived. The plant is too
well known to need description here, but its edible tuber, actually a
stem organ, is often wrongly called a root. Figure 8 shows the tubers
and true roots of the plant.

The sweet potato, which in early writings was often confused with
_Solanum tuberosum_, is a very different plant. Its edible portion is
the root of a vine very like our common morning-glory or convolvulus,
and its Latin name is _Ipomœa batatas_. The specific name is taken
from a native American word, which due to early confusion was corrupted
into potato, and applied to the “Irish” potato. No one certainly knows
where the sweet potato is native, but probably in tropical America. It
belongs to a section of the genus _Ipomœa_, all the other species of
which are American, and before Columbus and his followers its
cultivation was unknown in the Old World. It was very soon carried by
the Portuguese to Japan and other parts of the Old World, and for a time
it was thought to be native there. America, however, is in all
probability its ancient home, although no really wild plant has ever
been found there or anywhere else. Its cultivation from very early times
in America is indicated, and Columbus upon his return from the New World
presented sweet potatoes to Queen Isabella.

COCONUT

It has been said many times that there are more uses for this plant than
there are days in a year. Wood, thatch, rope, matting, an intoxicating
beverage, and scores of other things are derived from different parts of
this palm, but it is as a food and beverage that its chief value lies.
The coconut palm is a tall tree with a dense crown of feathery but stout
leaves and inhabits all parts of the tropics. It is found apparently
wild along sandy shores, but its ancient home, while still unknown, is
probably America. Each year the tree bears from ten to twenty fruits
which are at first covered with a green and very tough fibrous husk,
inside which is the seed, the coconut of commerce. In the early stages
of the fruit the white meat is preceded in large part by a delicious
milky liquid much used by the natives, but only rarely found in any
quantity in the coconuts shipped to our markets. The meat is highly
nutritious and is used on a great scale as food by millions of tropical
peoples. Within the last few years a method of taking out the meat of
the coconut and shipping it in a state of arrested fermentation to the
north has been discovered. This product, known as copra, is produced in
enormous quantities, both in the Old and the New World, particularly in
India and the Philippines. From this copra a palm oil is refined, which
is the chief source of the nut butter now so widely sold. Some idea of
the extent of the cultivation of coconuts may be gleaned from the fact
that in India and the Philippines the trees are counted by the hundreds
of millions. The oil from the nuts is also largely used in cookery, in
making candles, for burning in lamps, and in making certain kinds of
perfume. The tree belongs to the _Palmaceæ_, a monocotyledonous family
of plants of great commercial importance. It is known as _Cocos
nucifera_, and the genus has over a hundred species, all of tropical
American origin. Whether _Cocos nucifera_ is American or not is still a
disputed point. From the fact that it will float in sea water without
injury to the seed it has been supposed that it was carried great
distances by currents. It is found both wild and cultivated throughout
the tropical world, and its use appears to have been known to the
Asiatics probably four thousand years ago. The curious fact remains that
it is the only palm that, in its wild state, is known both in the Old
and New World, all others being peculiar to one hemisphere or the other.
Perhaps its capacity for floating in the sea without injury may explain
what is otherwise still a good deal of a mystery.

There are many other foods derived from plants, besides all the fruits
and vegetables too numerous to be noted in detail here. One fact of
significance seems to stand out from a study of the uses of plants by
man. There are three distinct regions from which the great bulk of our
food and many other useful plants have apparently come. One is the area
of which Indo-China is approximately the center, and which is the
ancestral home of rice, the banana, tea, sugar cane, and many other
valuable plants. Somewhere in this southeastern corner of Asia there
must have been a highly developed agriculture which rescued these plants
from the wild, and from which they have spread throughout the world. The
second region, somewhere near Mesopotamia, appears to be the cradle of
wheat and a few other useful plants. And the third region is the western
part of America from southern Mexico to northern Chile, where corn,
tobacco, the pineapple, sweet potato, potato, the red pepper, and the
tomato were all discovered with the discovery of this continent.

Alphonse de Candolle, from whose studies much of our information on the
origin of cultivated plants is derived, once prepared a list of our
common vegetables showing their ancient homes, their wild ancestors, and
the length of time during which they have been in cultivation. With some
recent additions and corrections by Dr. Orland E. White of the Brooklyn
Botanic Garden, the list is printed below:

The letters indicate the probable length of cultivation.

(_a_) A species cultivated for more than 4,000 years.

(_b_) A species cultivated for more than 2,000 years.

(_c_) A species cultivated for less than 2,000 years.

(_d_) A species cultivated very anciently in America.

(_e_) A species cultivated in America before 1492 without giving
evidence of great antiquity of culture.

(_f_) A species or subspecies of very recent domestication.

COMMON NAME SCIENTIFIC NAME DATE ORIGIN
Artichoke, Globe _Cynara Scolymus_ L. C Southern Europe,
northern Africa,
Canary Islands.
Artichoke, _Helianthus tuberosus_ L. E Eastern North America.
Jerusalem
Asparagus _Asparagus officinalis_ L. B Europe, western temperate
Asia.
Bean (Broad
or Windsor) _Vicia Faba_ L. B(?) Temperate Europe.
Bean (Pole
Lima) _Phaseolus lunatus_ L. E Tropical America, Peru,
Brazil.
Bean (Bush
Lima) _Phaseolus lunatus_ L. F Eastern North America.
Bean (String,
etc.) _Phaseolus vulgaris_ L. D Western South America.
Bean (Tepary) _Phaseolus acutifolius_ D Southwestern United
Gray States.
Bean (Adzuki) _Phaseolus angularis_
Willd. B(?) China, Japan.
Beet (Chard) _Beta vulgaris_ L. B Canary Islands,
Mediterranean region,
western temperate
Asia.
Beet (Root) _Beta vulgaris_ L. B Europe, Mediterranean
region.
Broccoli _Brassica oleracea_ var.
_botrytis_ DC. C Western Asia.
Brussels
sprouts _Brassica oleracea_ var.
_gemmifera_ DC. C Belgium (?)
Cabbage _Brassica oleracea_ L. A Western Asia.
Cabbage
(Chinese) _Brassica Pe-tsai_ Bailey B China, Japan.
Carrot _Daucus Carota_ L. B Europe, western temperarate
Asia.
Cauliflower _Brassica oleracea_ B Western Asia.
_botrytis_ DC.
Celeriac _Apium graveolens_ L. var.
_rapaceum_ DC. C Europe.
Celery _Apium graveolens_ L. B Temperate and southern
Europe, northern
Africa, western
Asia.
Chives _Allium Schoenoprasum_ L. C Temperate Europe,
Siberia, northern
North America.
Corn (field) _Zea Mays_ L. D Mexico, northwestern
South America (?)
Corn (sweet) _Zea Mays saccharata_ E Eastern North America,
Sturt. New England.
Cress (garden) _Lepidium sativum_ L. B Persia (?).
Cress (water) _Radicula
Nasturtium-aquaticum_ L. B Europe, northern Asia.
Cucumber _Cucumis sativus_ L. A India.
Cucumber
(gherkin) _Cucumis Anguria_ L. F West Indies.
Dandelion _Taraxacum officinale_ Weber C Europe and Asia.
Egg plant
(aubergine) _Solanum Melongena_ L. A India, East Indies.
Endive _Cichorium Endiva_ L. C Mediterranean region,
Caucasus, Turkestan.
Garlic _Allium sativum_ L. B Kirghis desert region
in Siberia.
Horse-radish _Roripa Armoracea_ L. C Eastern temperate
Europe, western
Asia.
Kale _Brassica oleracea_
var. _acephala_ DC. B Europe.
Kohl-rabi _Brassica oleracea_
var. _Caulo-Rapa_ DC. B Europe.
Leek _Allium Porrum_ L. B Mediterranean region,
Egypt.
Lentil _Lens esculenta_ Moench A Western temperate
Asia, Greece.
Lettuce _Lactuca sativa_ L. B Southern Europe,
western Asia.
Mushroom _Agaricus campestris_ L. C Northern hemisphere
(Europe).
Okra (gumbo) _Hibiscus esculentus_ L. C Tropical Africa.
Onion _Allium Cepa_ L. A Persia, central Asia.
Onion (Welsh) _Allium fistulosum_ L. C Siberia, Kirghis desert
region to Lake Baikal.
Parsley _Petroselinum Hortense_
Hoffm. C Southern Europe,
Algeria, Lebanon.
Parsnip _Pastinaca sativa_ L. C(?) Central and southern
Europe.
Pea (garden) _Pisum sativum_ L. A Western and central
Asia, southern
Europe, north
India (?).
Pea (wrinkled
garden) _Pisum sativum_ L. F England (?).
Pea (edible
podded) _Pisum sativum_
var. _saccharatum_ Hort. C Holland, etc.
Pepper (red) _Capsicum annuum_ L. E Brazil, western South
America.
Potato _Solanum tuberosum_ L. E Chile, Peru.
Potato (sweet) _Ipomœa Batatas_ Poir. D Tropical America.
Pumpkin _Cucurbita pepo_ L. E Subtropical and tropical
America.
Radish _Raphanus sativus_ L. B Temperate Asia.
Radish (Japanese
giant or
Daikon) _Raphanus sativus_ L. (?) Japan, China.
Rhubarb _Rheum Rhaponticum_ L. C Desert and subalpine
regions of southern
Siberia, Volga River.
Rutabaga _Brassica oleracea_
var. _Napo-Brassica_ L. C Europe.
Salsify or
Oyster plant _Tragopogon porrifolius_ L. C(?) Southeastern Europe
or Algeria.
Spinach _Spinacea oleracea_ L. C Persia, southwestern
Asia.
Spinach (New
Zealand) _Tetragonia expansa_
Thunb. F New Zealand.
Squash
(winter) _Cucurbita maxima_
Duch. E or D Tropical America.
Squash
(summer) _Cucurbita Pepo_ L. E Temperate or tropical
America.
Tomato _Lycopersicum esculentum_
Mill. F Peru.
Tomato (currant
or
raisin) _L. pimpinellifolium_ Dunal F South America.
Turnip _Brassica Rapa_ L. A Europe.
Yams Several sp. including
_Dioscorea alata_ L.
and _D. Batatas_ Decne. B (?) Southeastern Asia,
Africa and South
Pacific Islands.

The following list of the common fruits also gives their native country,
period of cultivation, and some additional notes about them. Those
marked with a star were found in the markets of New York City by Dr.
White, who also revised this list. The letters for the dates are the
same as in the list of vegetables:

NAME DATE ORIGIN REMARKS
Achocon F(?) Peru Relative of the violet.
Much esteemed locally.
*Actinidia (?) N. E. Asia, China Tastes something like a
gooseberry, with a fig
flavor.
Akee F W. tropical Africa Much esteemed cooked
fruit in Jamaica.
*Alligator pear E West Indies, W. Excellent salad fruit.
(avocado) South America to
Chile
Anchovy pear West Indies Unripe fruit pickled.
*Apple A E. Europe, W. Asia Very different type common
to China
*Apricot A Central Asia, China Wild species variable.
*Banana A Southern Asia Exists in hundreds
of varieties.
*Blackberry F United States Wild species very variable.
*Blueberry F E. and N. North Four species. Often confused
America with huckleberry.
Breadfruit (?) East Indies Baked and eaten as a
vegetable.
Buffalo berry F N. W. United States Very acid, bright red or
yellow fruit. Local.
*Cactus fig E Mexico, West Indies Common New York City
fruit.
Cambuca (?) Brazil Subacid garden fruit.
Local.
Cashew (?) Tropical America Fruit excellent as preserves.
*Cherry, sour B Asia Minor, S. E. Locally common.
Europe (?)

[Illustration: A BANANA PLANTATION IN FRUIT. The banana is now grown
throughout the tropical world, but native in tropical southeastern Asia.
(_Courtesy of Brooklyn Botanic Garden._)]

[Illustration: RICE TERRACES IN CHINA. In many regions where the forests
have been destroyed and all the soil washed into the valleys,
agriculture has to be carried on under conditions of great difficulty.
Soil is brought up these slopes and held there by the artificially made
terraces. (_Photo by Bailey Willis. Courtesy of Brooklyn Botanic
Garden._)]

NAME DATE ORIGIN REMARKS
*Cherry, sweet B S. Europe, E. Asia N. Y. City markets from
California.
Chirimoya E Ecuador, Peru Repeatedly dug up from
prehistoric graves in
Peru.
Chupa-chupa F Colombia Apricot-mango flavored.
Citron B India, S. Asia Very variable.
*Cranberry F E. and N. North Cultivated for about 100
America years.
*Currant, black C N. Europe and Asia Rarely cultivated in America.
*Currant, red C N’th’n Hemisphere White and yellow varieties
are forms.
*Custard apple (?) Tropical America
*Date A Arabia, north Hundreds of varieties.
Africa
Dewberry F South and central Form of blackberry.
North America
Duku (?) Malay Peninsula Fine Malayan fruit, somewhat
turpentine in
flavor.
Durian F Malaysia, East Odor of old cheese, rotten
Indies onions flavored with
turpentine. Delicious except
for odor.
*Fig A Southern Arabia Wild form common.
Genip (?) N. South America Children’s fruit.
Genipap (?) American tropics Used for a refreshing
drink locally.
*Gooseberry C N. Europe, N. Old and New World species
Africa, W. Asia, distinct. New World
United States varieties in some cases
hybrids.
“Goumi” berry (?) Japan, China Delicious acid fruit.
*Grape, New North America Many probably hybrids.
World F
*Grape, Old Western temperate California and Old World
World A Asia grape.
*Grapefruit B Malayan and Pacific Largely cultivated in U. S.
Is., east of Java
Ground cherry F Barbadoes, W. South Three or more species.
America, Asia
Grumixama (?) Brazil Much like bigarreau
cherry.
*Guava E Tropical America Fruits of several species
used.
Haw China, South United Local fruit.
(2 species) (?) States
Icaco F (?) Tropical America Common fruit in San Salvador.
Jaboticaba F Brazil Common fruit tree around
Rio Janeiro.
Jujube, China Very excellent dried fruit
common B in China.
Juneberry F United States, Locally esteemed.
Canada
*Kumquat (?) Cochin-China or Resembles very small
China oranges.
*Lemon B India
*Lime B India Largely used for limade
and citric acid.
*Litchi and S. China, Malay Finest Chinese fruit. Numerous
relatives C Archipelago forms.
*Loquat (?) Central-east’n Much esteemed in China
China and Japan.
Lulo F Colombia Tomatolike fruit.
Mammee
apple (?) West Indies to “St. Domingo apricot.”
Brazil
*Mango A (?) India “Should be eaten in a
bathtub.”
Mangosteen (?) Sunda Islands, King of tropical fruits.
Malay Peninsula
Marang (?) Sulu Archipelago Similar to but much better
than breadfruit.
Marmalade Mexico, N. E. Resembles in taste a ripe,
plum E South America luscious pear.
Matasano Central America “Delicious.”
Medlar C Central Europe to Local applelike fruit.
W. Asia
Monstera F Mexico Pineapple-banana flavor.
Mulberry, Armenia, N. Persia Most valued for fruit.
black B (?)
Mulberry, India, Mongolia Most valued for feeding
white A (?) silk worms.
*Muskmelon C India, Beluchistan, Hundreds of varieties.
W. Africa
Natal plum F South Africa Local fruit for preserves.
*Nectarine (?) Cultivated form of Smooth-skinned.
peach
*Olive A Syria, southern Does not fruit in Florida.
Anatolia and
neighboring
islands
*Orange, king (?) Cochin-China Recently common in New
York City markets.
*Orange, sweet C India Numerous hybrids with
other species.
*Orange, Cochin-China, China
tangerine ?
Papaw F South’n United Local fruit related to the
States custard apple.
Papaw, true E Tropical America Excellent breakfast fruit.
*Passiflora F (?) Tropical America Used locally for ices, fruit
salads, jams, etc.
*Peach E China Hundreds of varieties.
*Pear A Temperate Europe Two species, and hybrids
and Asia, N. between them.
China
*Persimmon (?) Northern China Common in New York
City markets.
*Pineapple E American tropics. Red Spanish and sugar
loaf, common market
varieties.
Piñuela (?) Mexico, C. America Sold cooked in Mexico.
and N. South Common market fruit
America of Caracas.
*Plantain Form of banana.
*Plum A S. Europe, W. Asia, Much hybridized group.
N. America
*Pomegranate A Caucasus, Persia, A seedless variety is
Afghanistan, known.
Beluchistan
*Quince A Persia to Turkestan “Apple of Cydon” (Crete).
*Raspberries, Middle N. America Locally much esteemed
black F American fruit.
*Raspberries, red C N. Europe, Asia, N. Varieties and hybrids of
America two species.
Rose apple B Malaysia, S. Asia Rose-water taste and
perfume.
Rose apple Tropics of Old and Many promising local
relatives New Worlds fruits.
*St.-John’s-Bread A (?) Syria, S. Anatolia, Common dried pod fruit
Barca (?) in New York City.
Sand cherry F N. W. United States Local fruit.
*Sapodilla E West Indies, “Chicle” or chewing gum
Central America, made from its sap.
N. South America
Sapote, black F Mexico Relative of persimmon.
Shaddock B East Indies Large pyriform relative of
grapefruit.
Soursop (?) West Indies Locally esteemed.
Star apple E W. Indies, Central Delicious. “Damson
America plum.”
*Strawberry F Temperate N. At least three species
America, Pacific involved. Mostly
coast of N. and hybrids.
S. America, Europe
Strychnos Bush veldt of South Tastes like clove-flavored
apple F Africa. pears.
*Sweetsop (?) West Indies Locally esteemed.
Tahiti apple (?) Society, Friendly, Common tropical fruit.
Fiji Islands
Tahiti apple South America Common West Indian
relatives (?) fruit.
*Tamarind B (?) Either India or N. Occasional New York
Africa City fruit.
“Tomato,” tree (?) Peruvian Andes Apricot-flavored tomato.
*Watermelon A Tropical and South Often a desert plant.
Africa

2. BEVERAGES

The operation of the Eighteenth Amendment to our Constitution will stop
the manufacture in this country of the chief beverages that were made
here from plants. All wines and brandies were from the juice of the
grape, whiskey from rye and some other cereals, and beer from hops and
barley. Our three remaining beverages of practically universal use are
none of them produced in the United States, with the exception of a
little tea grown in a more or less experimental way.

TEA

It is related in an old legend that a priest going from India into China
in 519 A.D. who desired to watch and pray fell asleep instead. In a fit
of anger or remorse he cut off his eyelids which were changed into the
tea shrub, the leaves of which are said to prevent sleep. Unfortunately
for the story tea was known in China more than three thousand years
before the date of that legend, and it is very doubtful if it was ever
brought from India to China. The wild home of the tea is apparently in
the mountainous regions between China and India, but the plant will not
stand the frost, so that its cultivation is now mostly in parts of
China, Japan, India, Ceylon, Java, and some in Brazil.

The plant is mostly a shrub or occasionally a small tree, with white
fragrant flowers and evergreen oval-pointed leaves. All the different
kinds of tea are derived from the single species _Camellia Thea_, the
differences in color and flavor being due to processes of culture or
curing of the leaves.

[Illustration: FIG. 99.--TEA

(_Camellia Thea_)

A shrub or small tree with white fragrant flowers.]

While the use of tea has been known to the Chinese for over four
thousand years, its introduction into Europe dates from the days of the
Dutch East India Company, who brought some to Holland about 1600, and by
the English East India Company, who sent some from China to England in
1669. It fetched at that time 60 shillings per pound for the common
black kinds and as much as £5 to £10 per pound for the finer kinds. It
was almost fifty years, or about 1715, before the price fell to 15
shillings per pound. From that time until the present there has been a
tremendous increase in its use, although then as now the great bulk of
the world’s tea is used by the Mongolians and Anglo-Saxons. Just before
the war over 700 million pounds comprised the annual crop of tea. As its
use became general the English put a tax upon its importation into Great
Britain or its colonies, with results here that we all know.

The cultivation of tea is restricted to those regions where there is a
large and frequent rainfall as well as a high temperature. It will not
grow in marshy places such as rice prefers, but needs light,
well-drained soils. The plant is propagated only from seeds which are
sown in nurseries, and the young plants set out in the tea fields about
four and a half feet apart each way. In two years they are bushes from
four to six feet tall when they are cut back to a foot high. The
increased vigor of the bush from this severe cutting back results in a
dense bush, from which leaves are plucked from the third year in small
quantity. Not until after the sixth or seventh year is there a normal
yield, which in an average year would be from four to five ounces of
finished tea. A poor yield of leaves would average about 400 pounds of
tea per acre, good yields going as high as a thousand pounds or even
more than that. The tea fields must be kept free of weeds, a tremendous
task in a moist tropical region, which demands cultivation about nine
times a year. The expense of properly setting out and maintaining a tea
plantation is therefore considerable.

The plucking of tea leaves is a fine art beginning with the starting of
new growth and continuing every few days until growth stops. In certain
regions growth is practically continuous and plucking also, but in most
regions the plant has an obvious resting period, when it is pruned back.
A properly cared for plant may last as long as forty or fifty years. In
a modern tea plantation the only part of the process of tea making that
involves handling is the plucking of the leaves, largely done by women
and children. The leaves are then spread on racks and allowed to partly
wither, after which they are put between rollers so as to crush the
tissue, thereby allowing the more rapid escape of water. After rolling,
all black teas are again spread out when oxidation of their juices
changes their color, but green teas omit this second spreading out and
sometimes even the first. The oxidation of black teas is produced by an
enzyme in the juice, in green tea this process is stopped by subjecting
the leaf at once to steam. This kills the enzyme but preserves the green
color of the leaf. In the black tea the enzyme is allowed to work for
two or three hours when the leaves are again slightly rolled to seal in
the juices and the leaves are then subjected to a current of air
progressively warmer until it reaches a temperature well above boiling
point. Once the temperature reaches about 240 degrees the process goes
on only for about twenty minutes when the leaves are perfectly dry and
crisp. The different sized leaves, buds, twigs, etc., are then sorted by
mechanical sifters and the finished tea is ready for packing. Experts
declare that there is no difference between broken and unbroken leaves,
and if there is any the flavor is probably better from broken leaves.
From the upper three leaves and their bud the finest teas are made, but
from adjoining plantations, even from the same plants at different
seasons or different pluckings, vastly different teas are often
produced. In different regions the process varies slightly in its
details, and different soils and culture undoubtedly affect the flavor
of tea, just as they do other crops. Some of these local conditions are
of great value, and the skillful handling of the leaves is as much of a
fine art as it is a science. Unlike wines, tea is best when fresh and
much of the romance of the sea centers around the China clippers which
made remarkably swift passages between China and England around the Cape
of Good Hope. With the opening of the Suez Canal competition for
increased speed became still more keen, but steam vessels took the
romance out of the trade. Much of the tea used in the United States
comes from Japan and does not go through London, which for over two
hundred years was the tea market of the world.

The thing for which we drink tea is an alkaloid in its leaves that is
pleasant to the taste and refreshing to the senses. It is released in
boiling water in a very few minutes, but if tea is allowed to stay in
water longer than this, tannic acid is also released. This is a
substance found in the bark of certain trees and is used in tanning
leather. As 10 per cent of the leaf of tea consists of this substance it
may readily be seen how easily improper methods of making tea will
render it not a refreshing and delightful beverage but an actual poison
to the digestive tract.

COFFEE

Like tea and chocolate, coffee also comes from a plant that can only be
grown in the tropics. Its original home was in or near Arabia and its
botanical name is _Coffea arabica_. There are, however, other species of
the genus that produce coffee, but _Coffea arabica_ is still its chief
source. The plant is

[Illustration: FIG. 100.--COFFEE

(_Coffea arabica_)

The coffee beans are contained in a red berry.]

now grown throughout the tropical world, but it does not thrive so well
along the coast as it does at elevations of a thousand feet or so,
where, in America at least, the best coffee is produced. The plant is a
shrub or small tree, usually not over 12 to 15 feet tall, with opposite
leaves and small tubular flowers, followed by a bright red berry, which
contains the coffee “beans.” The flowers and berries are in small
clusters in the axils of the leaves. Its use among the natives appears
to date from time immemorial, but the Crusaders did not know it, nor was
it introduced into Europe much before 1670. Its annual consumption is
now well over two billion pounds, nearly half of which is used in this
country. We use over ten pounds a year for each man, woman and child in
the country, or nearly ten times the per capita consumption in England.
Brazil produces over half the world’s total supply and consequently
controls the coffee markets of the world. The plant was first brought
into South America by the Dutch, who in 1718 brought it to Surinam. From
there it spread quickly into the West Indies and Central America.

The coffee berries are collected once a year and spread out to dry,
after which the two seeds are taken out. This is the simple method of
all the smaller plantation owners, but a modern Brazilian coffee
plantation follows a very different procedure. The berries are put in
tanks of water, or even conveyed by water flues from the fields, and
allowed to sink, which all mature berries will do. They are then
subjected to a pulping machine which after another water bath frees the
beans from the pulp. The former are still covered by a parchmentlike
skin which, after drying of the beans, is removed by rolling machines.
The coffee is then ready for export, but not for use until it is
roasted. This is a delicate operation not understood except by experts,
and should not be done until just before the coffee is ready to be used.

The average yield per plant is not over two pounds of finished coffee a
year, but larger yields from specially rich soils are known. The plant
is rather wide-spreading and not over five or six hundred specimens to
the acre can be grown.

The so-called Mocha coffee is obtained in Arabia, where Turkish and
Egyptian traders buy the crop on the plants and superintend its picking
and preparation, which is by the dry method. Not much of this ever
reaches the American markets, and the total amount of coffee now
produced in Arabia, its ancestral home, is negligible.

CHOCOLATE

Unlike tea and coffee, chocolate is a native of the New World and was
noticed by nearly all the first explorers. It grows wild in the hot,
steaming forests of the Orinoco and Amazon river basins, although it was
known in Mexico and Yucatan as a cultivated plant from very early times.
By far the largest supply still comes from tropical America, although it
is grown in the Dutch East Indies, Ceylon, and West Africa. It must have
been cultivated for many centuries before the discovery of America, as
scores of varieties are known, all derived from one species. This is
_Theobroma cacao_, and both the generic and specific names are
interesting. _Theobroma_ is Greek for god food, so highly did all
natives regard the plant, and _cacao_ is the Spanish adaptation for the
original Mexican name of the tree. Throughout Spanish or
Portuguese-speaking tropical America the tree is always spoken of as
_cacao_.

The chocolate tree is scarcely over twenty-five feet tall, has large
glossy leaves and bears rather small flowers directly on the branches or
trunk. This unusual mode of flowering, common in rain forests, results
in the large sculptured pods appearing as if artificially attached to
the plant. Each pod, which may be 6 to 9 inches long, contains about
fifty seeds--the chocolate bean of commerce.

When the beans first come out of the pod they are covered with a slimy
mucilaginous substance and are very bitter. To remove this the beans are
fermented or “sweated,” usually by burying in the earth or piled in
special houses for the purpose. After several days, sometimes as long as
two weeks, the beans lose the mucilage, most of their bitter flavor and
often change their color. After this they are dried and are ready for
roasting, which drives off still more of their bitter flavor. Chocolate
is made from the ground-up beans containing nearly all the oil, which
is the chief constituent, while cocoa is the same as chocolate with a
large part of the oil removed. As in tea and coffee, there is an
alkaloid in chocolate for which, with its fat, the beverage is mostly
used.

Very little chocolate is now collected from wild plants, and cacao
plantations are important projects in tropical agriculture. Because of
its many varieties, some nearly worthless, the business was rather
speculative until a few good sorts were perpetuated. Much valuable work
on this plant and the isolation of many good varieties has been done by
the Department of Agriculture in Jamaica, British West Indies. Cacao
plantations are usually in moist, low regions near the coast, preferably
protected from strong winds, to which the plant objects. The trees are
set about ten to fifteen feet apart each way and begin bearing after the
fifth or sixth year. The young plants are always shaded, often by
bananas, which are cut off as the trees mature. The tree will not thrive
unless the temperature is about 80 degrees or more and there should be
preferably 75 inches of rainfall a year, about twice that at New York.
Chocolate-growing regions are apt to be unhealthy for whites, and native
labor is practically always used. The business is very profitable, but
still somewhat speculative.

3. FIBERS

Not only do plants furnish us with food and drink, but most of our
clothing is made from plant products. There is annually produced twice
as much cotton as wool, while linen is made from the fibers in the stem
of the flax plant, which is also the source of linseed oil. Fibers occur
in many different parts of plants, but most often in the stem, or in
the bark of the stem. Some occur in the wood itself, as for instance
that in spruce wood, from which news paper is made. Others are found in
the attachments of the seed, such as cotton. Some are very coarse, such
as that of _Carex stricta_, a swamp sedge from which Crex rugs are
woven. Others like that of the leaves of the pineapple are as fine as
silk, and in the Philippine Islands where much pineapple fiber is
produced, some of the most beautiful undergarments and women’s wear are
made from it. Again, others, such as Manila hemp, furnish us with
cordage of great strength.

COTTON

It has been stated, perhaps a little rashly, that the value of the
cotton crop in our Southern States exceeds all other agricultural
products of the country. Whether this be true or no matters not, as
cotton production and manufacture is certainly one of the most important
industries of the world. Our own New England mills and those in
Lancashire total an enormous volume of manufactured cotton goods, and
what the stoppage of the cotton crop means to these industrial centers
was shown even so far back as the Civil War, when the “cotton riots” in
Lancashire were noised all over the world. Cotton is the most important
of all fiber plants.

There are several different kinds of commercially important cottons, and
perhaps dozens of others, all derived from the genus _Gossypium_, a
relative of our common garden mallows belonging to the _Malvaceæ_. By
far the most valuable is Sea Island cotton, derived from _Gossypium
barbadense_, which is probably a native of the West Indies, although
really wild plants are yet to be discovered. It is the kind, of which
scores of varieties are known in cultivation, that is grown mostly along
our southeastern coastal States. Next in value, but cultivated in
greater quantity because larger areas are suited to it, is _Gossypium
hirsutum_. The fiber is a little shorter, but the total amount of cotton
derived from this species probably exceeds that from all other kinds. It
is the cotton grown mostly in upland Georgia, Louisiana, and Texas, and
the wild home of this species is supposed to be America, although it,
too, has never been found in the wild state. The third cotton plant is
_Gossypium herbaceum_, a native of India, and the origin of many
varieties now grown in that country. It has a shorter fiber and is worth
about one-third the price of Sea Island cotton. From Abyssinia and
neighboring regions comes the fourth important cotton plant, _Gossypium
arboreum_, differing from the others in being a small tree. All the
others are shrubby, while _G. herbaceum_ is merely a woody herb. These
different plants have been tried in the countries suited to cotton
raising, but, generally speaking, the chief crop from each is produced
in the country nearest the supposed wild home of it.

In all of them the fiber is really an appendage of the seeds, and each
pod as it splits open is found to be packed full of a white cottony mass
of these fibers with the seeds attached. These white masses of cotton,
or bolls, have to be picked by hand, as no really successful machine has
ever been found for this purpose. Women and children do a large part of
the picking, and the wastage due to careless picking is tremendous. The
whole value of the cotton crop depends upon an invention by Eli Whitney,
an American, of a machine to separate the cotton from its seed. This
“ginning” machine is now much perfected and, in America at least, is the
chief method of separation of fiber and seed. In India and for certain
other varieties a different type of machine, known as the Macarthy gin,
is employed. The latter is used in America also for some of the
long-fiber Sea Island cottons. With the baling of the cotton the work of
the grower is over and the product is ready for the manufacturers. The
resulting seed, after ginning, once little valued, is now an important
plant product, cottonseed oil, cattle feeds, soap, cottolene, fuel oil,
and fertilizers being derived from it. Its value in the United States
now totals millions of dollars annually.

In growing cotton in America seeds are sown in April, and the beautiful
yellow flowers with a red center bloom about June or July, followed in
August by the pod. This splits open and is ready for picking by
September and October. The plants are grown in rows four feet apart and
are set one foot apart in the row. Clean cultivation is absolutely
necessary, and in first-class plantations all weeds are kept out. The
plant needs a rich deep soil.

HEMP AND CORDAGE

There are a variety of plants which furnish products known as hemp, but
commercially only three are of much importance, the plant universally
known under that name, the Manila hemp, and sisal. All of them are used
chiefly for cordage.

The hemp of the ancients is a tall annual related to our nettles, with
rough leaves, and a native of Asia. For centuries an intoxicating drink
was made from the herbage of this plant, and this with the narcotic
hashish, which is made from a resin exuded by the stems, obscured the
fact that _Cannabis sativa_ is a very valuable cordage plant. The coarse
fibers are found in the stem, and these are cut and retted, the retting
or rotting process separating the fibers from the waste portions of the
stem. The fibers are so long and coarse that only cordage, ropes, and a
rough cloth are made from them, but enormous quantities are raised for
this purpose, especially in Europe. As hashish is now a forbidden
product in many countries, due to its dangerous narcotic effects, the
hemp plant is more cultivated for fiber than for the narcotic. But in
the olden days hashish had a tremendous vogue in the Orient and was
known at the time of the Trojan wars, about 1500 B.C. Fiber from the
plant was almost unknown to the Hebrews, and it was not until the
beginning of the thirteenth century that it came into general use. It is
now probably as important as sisal, but not as Manila hemp, the most
valuable of all cordage plants. The hemp is diœcious and the female
plants are taller and mature later than the male. Two cuttings are
therefore necessary in each field.

The Manila hemp is derived from a banana (_Musa textilis_), that is a
native of tropical Asia and is much grown in the Philippines. While the
fruits of this plant are of very little or no value, the fiber from the
long leafstalk is the best cordage material known. Also the finer fibers
near the center of the stalk are made up into fabrics, which are rarely
seen here, but are said to be almost silky in texture. As a cordage
plant, however, _Musa textilis_ is now easily the most important, and
from a commercial point of view the Philippine Islands is the only
region to produce it in quantity. It has been tried with not much
success in India and the West Indies. Methods of extracting the fibers
are still very primitive, as it is nearly all scratched out by natives
with saw-toothed knives made for the purpose. After the fleshy part of
the leafstalk has been separated from the fiber this is merely put out
on racks to dry. The finished product has so much value for large cords
and ropes that the fiber makes up about half the total exports of the
Philippine Islands. Its great strength may be judged from the fact that
a rope made from it, only about one inch thick, will stand a strain of
over four thousand pounds. No other fiber is anywhere near this in
strength and yet of sufficient length to be of use as cordage. There are
still thousands of acres suitable for its culture in the Philippines,
but the extraction of the fiber awaits some inventive genius who will
make a machine for that purpose. Many have tried, but so far the
primitive scratching out by natives is the only method in use and it is
admitted that it wastes nearly one-third of the fiber. The so-called
Manila or brown paper is often made from old and worn-out ropes of
Manila hemp, but, as in the case of cordage itself, adulteration with
cheaper fibers is common.

From Yucatan, the Bahamas, and some other regions of tropical America
comes the most valuable American cordage plant, known as sisal. The
fiber is extracted from the thick coarse leaves of a century plant,
known as _Agave sisalina_ or _Agave rigida_, which looks not unlike the
century plant so common in cultivation. The plant belongs to the
Amaryllis family and is native in tropical America. Thousands of acres
are planted to sisal in Yucatan and a machine for scratching out the
fiber is in general use. The plant produces each year a crown of eight
or ten leaves from three to five feet in height, each tipped with a
stout prickle. Unlike the common century plant of our greenhouses there
are no marginal prickles on the leaves of the sisal. After extraction
the fiber is stretched out on racks to dry and is then ready for
manufacture into rope.

JUTE

During the late war the Germans were reported to be sending flour and
sugar to their armies pressed into large bricks for the want of bags to
ship them in the ordinary way. Gunny sacks, or jute bags, as they are
more often called, are made literally by the hundreds of millions, as
practically all sugar, coffee, grains and feeds, and fertilizers are
shipped in them. Jute is a tall herb, a native of the Old World tropics,
but suitable for cultivation in many other tropical regions. Practically
all the world’s supply now comes from India, probably because of the
cheapness of labor rather than any peculiar virtue of the soil or
climate of that country. The plant has been experimentally grown in Cuba
with entire success, but labor conditions made cheap production of the
fiber impossible.

The jute plant, known as _Corchorus capsularis_ or _C. olitorius_, grows
approximately six to nine feet tall and is an annual, often branching
only near the top. They are not very distantly related to our common
linden tree. At the proper maturity the whole plant is harvested and the
stems are tied into bundles ready for the retting process. Of all fiber
processes this is the most difficult, largely because no machine or
chemical has yet been found to

[Illustration: FIG. 101.--THE JUTE PLANT

The fiber is mostly derived from _Corchorus capsularis_ and from
_Corchorus olitorius_.]

extract the fiber of jute, or flax, and this is accomplished by placing
the stems in water, which rots out the fleshy part of the stem, leaving
the fiber. Some notion of the difficulty of this task in such plants as
jute is gained by realizing that over twelve million bales of finished
fiber are produced each year, and that the retting may take from two
days to a month. The retting process is aided by certain organisms of
decay in the water, by the temperature, and by some other factors not
yet understood. The process is allowed to go on only long enough to
separate flesh from fiber, which makes frequent inspection of the
bundles in the filthy water an absolute necessity. At the proper time
the natives are able to split off the bark, which contains the fiber,
from the stem, and while standing up to the waist in the water, he picks
or dashes off with water the remaining impurities. The fiber is then
dried on racks and subsequently, under enormous pressure, packed in
bales of four hundred pounds each. An average crop would be about two
and one-half bales from an acre of jute, so that in India there must be
considerably over five million acres devoted to the cultivation of the
plant. While for many years this tremendous output of fiber was sent to
England for manufacture, power looms were set up in India about the
middle of the last century. There are now over three-quarters of a
million spindles there, and some jute is sent to the United States for
manufacture here.

Next to cotton jute is probably the most important fiber plant in the
world. For hundreds of thousands of people in India and in England it is
the only source of livelihood. To the inventor who can eliminate or
reduce the costly retting process of jute, or of flax, which goes
through essentially the same operation, there is waiting a golden
future, for it is largely the cheapness of labor and willingness of its
natives to stand in the retting pools that has made India the jute
region of the world.

Lack of space forbids mention of the many other fiber plants, some of
which, like flax, are of large importance. Their fibers are used in a
variety of ways and are found in different parts of the plant. A few of
these, together with the names of the plants and the regions where they
are native, are as follows:

NAME OF PLANT PRODUCT NATIVE

Bowstring hemp. Bowstrings and Tropical Africa
_Sansevieria_, several cordage. and Asia.
species.

Coconut palm. Coir. Tropical America (?)
_Cocos nucifera._

Flax. _Linum usitatissimum._ Linen. Europe and Asia.

Kapok. Kapok, for stuffing. India.
_Eriodendron anfractuosum._

New Zealand flax. Cordage. New Zealand.
_Phormium tenax._

Paper mulberry. Paper pulp in Japan.
_Broussonetia papyrifera._ Japan.

Pita. _Bromelia Pinguin._ Pita fiber, fabrics. Tropical America.

Queensland hemp. Jute substitute. Tropical regions.
_Sida rhombifolia._

Raffia. _Raphia ruffa._ Cloth and for tying. Madagascar.

Ramie. _Boehmeria nivea._ Ramie cloth. Tropical Asia.

Rattan cane. Rattan, cordage, India.
_Calamus rotang._ and coarse cloth.

Rush. _Juncus effusus._[2] Matting in Japan. North temperate
regions.

Sedge. _Carex stricta._ Rugs and mattings. Northern North
America.

Spruce. _Picea rubens_, Paper pulp. Northern North
_canadensis_, etc. America.

Willows. _Salix_, many Basketry. Temperate regions
_species_. mostly.

No mention can be made here of the hundreds of fiber plants used by the
natives of various parts of the world, some of them probably having
great commercial possibilities. The extraction of these fibers by
machinery or chemically will open up a large commerce in such plant
products, the value of which is now unsuspected or ignored. While the
value of cotton, jute, and Manila hemp is reckoned in the hundreds of
millions, some of these native fibers are found in plants whose wild
supply is almost inexhaustible, and some of which are quite as capable
of cultivation as the better known fiber plants. Few fields of inquiry
offer greater possibilities to the economic botanist than fibers.

4. THE STORY OF RUBBER

Along the north coast of Haiti, particularly near Cap Haiti and Puerto
Plata, there are scattered a few plantations devoted to rubber growing;
and it is not without interest that Columbus on his first voyage landed
at about this precise spot in December, 1492, and found the natives
playing a game of ball made of rubber. He wrote: “The balls were of the
gum of a tree, and although large, were lighter and bounced better than
the wind balls of Castile.” This is apparently the first notice of the
use of rubber, a substance now of world-wide importance, and derived
from many other plants than the tree mentioned by Columbus. This is
_Castilla elastica_, a native of certain islands of the West Indies and
the adjacent mainland, and a relation of our common mulberry.

For over three centuries rubber, or caoutchouc as it was often called,
was only of very casual use before the process of vulcanizing was
discovered by Charles Goodyear, an American, in 1839. This combination
of rubber with sulphur transformed a material much subject to heat and
cold, and of almost no manufacturing value, into one from which hundreds
of articles of daily use are now manufactured. Previous to this it had
been used mostly, and in fact almost exclusively, as a waterproofing
material for cloth, a process much developed by the firm of Charles
Macintosh & Co., who appear to have taken out the first patent for a
waterproofing process in 1791, in England. The rubber tree found by
Columbus is still grown in considerable quantities and is a valuable
source of rubber, but it has been greatly overshadowed by a Brazilian
tree which now produces over two-thirds of all the rubber in the world.

[Illustration: FIG. 102.--BRAZILIAN OR PARA RUBBER (_Hevea
brasiliensis_)

Native in the Amazon region, but now much grown in the East Indies.]

This Brazilian tree, a native of the rich rain forests of the Amazon, is
_Hevea brasiliensis_, and a relative of our common spurges of the
roadsides and of the beautiful crotons of the florist, all belonging to
the family _Euphorbiaceæ_. The first important notice of this rubber
appears to be by the astronomer C. M. de la Condamine, who was on an
astronomical trip to the Amazon in 1735. He described _Para_ rubber, as
it has since been called, and by 1827 the export of this gum had grown
to 31 tons a year. In 1910 Brazil exported over 38,000 tons, nearly all
of which was collected from wild trees. After the discovery of
vulcanization the demand for all kinds of rubber increased by leaps and
bounds and it became obvious that the wild trees, although tapped
regularly, would not supply all of the necessary amount. For years the
Brazilian Government protested the export of seeds or other means of
growing the plant out of the Amazon, but in 1876 H. A. Wickam chartered
a steamer and loaded her with 70,000 seeds of para rubber trees and some
crude rubber, and had the ship passed by the Brazilian port authorities
as loaded with “botanical specimens.” He safely transported the cargo to
the Kew Gardens, London, where only about 4 per cent of the seeds ever
germinated. From there the young plants were sent to India, where now,
and in the Straits Settlements and the adjacent islands, there are huge
plantations of para rubber. From the wildest speculation in rubber
shares on the London Stock Exchange, which followed the successful
introduction of the plant into British possessions, the industry has now
settled down to be one of the most profitable in plant products of the
East.

The rubber of both _Hevea_ and _Castilla_ is produced from the milky
juice or sap of the trees and is actually a wound response. As the trees
are tapped the _latex_, as the milky juice is called, runs out of the
wound and upon reaching the air coagulates. This material is removed and
a new wound made, a process which is repeated for several years. There
is still work to be done upon the problem of how often plantation trees
should be tapped to get the greatest flow of latex without injuring the
tree, but in many plantations it is done every day or every other day in
the season, some rubber planters allowing a resting period during leaf
fall, others again tapping almost continually. The actual wound is made
by removing just enough bark to induce a flow of latex, but not until
the wound is completely healed, a process taking from four to six
years, can that particular part of the bark be cut again. With almost
daily tappings the problem of finding fresh pieces of bark into which
the cut may safely be made has been developed into a fine science. In
the wild trees of Brazil it is still done by natives, probably rather
wastefully. Rubber plantations in the tropical regions of Asia now total
over a million acres, as compared to only slightly over 200,000 acres in
the American tropics and from all other non-Asiatic sources. Of this
probably 100,000 acres are in Africa. At the present time nearly half
the world’s supply of rubber comes from these plantations, the balance
still coming from Brazil.

There are two other rubber-producing plants, neither of which are as
important as _Hevea_ and _Castilla_. One is the common rubber plant so
much grown as a house plant and said to be much cherished for that
purpose in Brooklyn. It is a kind of fig tree, known as _Ficus
elastica_, a native of India and the source of India rubber. It was used
for years, before the days of vulcanization, mostly for lead-pencil
erasers. Thousands of acres of it in India were recently destroyed to
make room for _Hevea_, although it still produces a respectable amount
of rubber, inferior, however, to _Hevea_ and _Castilla_. In Mexico a new
source of rubber is the guayule rubber plant, a small shrub native of
the drier parts of the Mexican uplands. It does not produce latex, as
practically all other rubber plants do, but particles of rubber are
found directly in its tissues, mostly in the bark. While of some
importance, this shrub, known as _Parthenium argentatum_, a member of
the _Compositæ_ or daisy family, is not likely to become a dangerous
rival of either Para or _Castilla_ rubber. Wild sources of guayule
rubber are already reported as diminishing rapidly, so that its
permanent success will depend upon cultivation. At least a score of
other plants are known to produce rubber of a kind, but none of them
have yet been much developed. From most plants with a milky juice, such
as dogbane or spurge, rubber of some sort can usually be recovered. The
production of this substance is directly due to a response of the plant
to wounds, and there are still great fields of research necessary on
this phase of plant activity, upon which a great industry has already
been built.

5. DRUGS

Nearly all the drugs and medicines of importance are of vegetable
origin, and from the days of Theophrastus the study of plants as
possible medicines has been one of the chief phases of botanical
research. In the early days all that was known about plants was learned
by men interested in medicine, and some of their quaint old books are
interesting relics of a bygone day. At present, pharmacognosy, or the
science of medicinal plant products, is a highly developed specialty
taught in medical and pharmacy schools. And yet the greatest medical
college in this country has recently issued instructions to its staff of
doctors and nurses to pay particular attention to “old wives’ remedies,”
most of which consist of decoctions of leaves and other parts of plants.
They have done this because all the knowledge of the scientists
regarding medicinal plants has its origin in the habit of simple people
turning to their local plants for a cure. The accumulation of the ages,
aided and guided by the scientist, has resulted in the wonderful things
that can now be done to the human body through the different drugs,
nine-tenths of which are of plant origin.

There is almost no part of a plant that, in some species at least, has
not been found to contain the various acids, alkaloids, oils, essences,
and so forth, which make up the chief medicinal or, as the pharmacists
call it, the active principle of plants. In certain of them the most
violent poisons are produced, such as the poison hemlock which killed
Socrates, and the deadly nightshade. And again the unripe pod of one
plant produces a milky juice so dangerous that traffic in it is
forbidden in all civilized countries, and yet later the seeds from that
matured pod are sold by the thousands of pounds to be harmlessly
sprinkled on cakes and buns by the confectioners. Earlier in this book
it was said that plants are chemical laboratories, and nowhere has this
alchemy been carried to such a pitch of perfection as in the hundreds of
drugs produced by different plants. Reference to special books on that
subject should be made by those interested, as only a few of our most
important drug plants can be mentioned here.

QUININE

The Spanish viceroy of Peru, whose wife, the Countess del Chinchón, was
dangerously ill of a fever in that country about 1638, succeeded through
the aid of some Jesuit priests in curing the malady, with a medicine
which these priests had gotten from the natives. It was a decoction from
the bark of a tree, and its fame soon spread throughout the world as
Peruvian bark. Even in those days malaria was the curse of the white man
in tropical regions, and since then it is hardly too much to say that
the discovery of this drug has made possible for white colonists the
retention of thousands of square miles of tropical country that without
it would in all probability be unfit for occupancy. To the natives, too,
quinine has been one of the greatest blessings, and in some of the
remote regions of the tropics the writer has found quinine more useful
than dollars in getting help from fever-ridden natives, too poor and too
remote from civilization to get the drug.

For more than a hundred and fifty years after the discovery of Peruvian
bark it was always taken as a liquid, usually mixed with port, and an
extremely noxious and bitter drink it made. The fine white powder which
we now use in tasteless pellets or pills has made the drug even more
useful than before.

The trees from which the bark is used all belong to the genus
_Cinchona_, named for the first distinguished patient to benefit by it,
and belong to the _Rubiaceæ_ or madder family. There are at least four
or five different species. For many years Peru and near-by states were
the only source of the bark, and the English became convinced that the
great trade in the drug would exterminate the tree, so in 1880 they
introduced the plant into India. These cinchona plantations now provide
most of the world’s demand, and some idea of what that means may be
gleaned from the fact that in Ceylon alone over fifteen million pounds
of the drug are produced annually. In India itself the plantations are
largely government owned and quinine is sold in the post offices at a
very low rate. In cinchona plantations strips of the bark are removed,
and after a proper period of healing, the process is repeated. It takes
about eight years before it is safe to begin cutting the bark.

ACONITE

Most doctors use aconite for various purposes and it is mentioned here
chiefly as illustrating a common characteristic of many medicinal
plants. The whole plant is deadly poisonous, and in the root there
appears to be a concentration of this poisonous substance, which makes
the plant one of the most dangerous known. All of the drug aconite is
derived from _Aconitum Napellus_, a monkshood, belonging to the
buttercup family. It is a perennial herb with beautiful spikes of
purple-blue flowers, not unlike a larkspur, and is a native of temperate
regions of the Old World. A related Indian species has been used for
probably thousands of years by the natives. They poison their arrows
with it and so deadly is the drug that a tiger pricked by such an arrow
will die within a few minutes. It is conceded to be the most powerful
poison in India. Numerous accidents have resulted in Europe from
careless collectors of the roots of horseradish, who sometimes get
aconite roots mixed with that condiment, usually with fatal results.

So many other plants are violently poisonous, and yet yield the most
valuable drugs, that the greatest care has to be used in their
collection and preparation. The habit of many children of eating wayside
berries should be discouraged, as some of our most innocent-looking
roadside plants are actually deadly if their fruits or foliage are
eaten. Fortunately only a very few plants are poisonous to the touch,
notably poison ivy and poison sumac, and some of their relatives.

OPIUM AND MORPHINE

Almost no plant product has caused more misery and relieved more pain
than the juice of the unripe pod of the common garden poppy, _Papaver
somniferum_. From it opium is extracted, the chief constituent of which
is morphine. If tea can be said to have precipitated our war of
independence, opium was indirectly the cause of the opening of China to
the western world. The degrading effects of opium had become so
notorious that the Chinese in 1839 destroyed large stocks of it, mostly
the property of British merchants, and prohibited further importations.
In the subsequent negotiations which ended in war, China was opened up
to trade. No civilized country now openly permits the sale of opium,
although there is still a good deal of it used in practically all parts
of the world. The effects of lassitude, subsequent ecstasy, and
stupefaction are due to an alkaloid, the continued use of which forms a
drug habit of serious consequences. Parts of China, Turkey, Persia, and
Siam are said to be still large users of opium which is chewed, or more
often smoked. Until comparatively recently fifteen out of every twenty
men in some of these countries were regular users of the drug. The
legitimate use of morphine by physicians has done more than almost
anything else, with the possible exception of cocaine, to relieve
suffering, and there is consequently a considerable trade in the drug.

The home of this poppy is unknown, as it has been cultivated from the
earliest days. The ancient Greeks and Romans knew it and the Egyptians
grew it for opium. It is still grown in India and China, where,
notwithstanding vigorous governmental measures, there is a large opium
consumption. After maturity the pods of the poppy, from whose milky
juice in its earlier stages the drug is obtained, produce many seeds.
From these an oil is pressed which is widely used as a cooking oil in
the East, and is perfectly harmless. The seeds are also used as bird
seed and by confectioners.

COCAINE

[Illustration: FIG. 103.--COCAINE PLANT

(_Erythroxylon Coca_)

Native in northern South America. The fresh leaves of this are used as a
valuable but harmless stimulant by the natives.]

In the northern part of South America the Peruvians and some of their
neighbors were discovered by early explorers to be chewing the leaves of
a native shrub, apparently with much profit and no evil after effects.
It served them much as the betel nut does to the natives of India and
other regions of the tropical East. With scanty or no food this
apparently harmless intoxicant will carry both men and women over
periods of severe fatigue. The shrub bearing these leaves is not over
four or five feet tall and has bright green foliage and small white
flowers.

Quite different in its effects has been the drug which has been
extracted from this plant, known as _Erythroxylon Coca_. Far from being
a beneficial and harmless stimulant, cocaine is now one of the drug
evils of our time. Its use, outside that prescribed by physicians, is
forbidden practically everywhere, but its consumption in this country,
aside from its great and legitimate use as a relief from pain, is still
very large.

The number of drug plants is legion, so large in fact, that volumes have
been filled with descriptions and notes about them. A few of the most
important, omitting those already mentioned, are listed below:

DRUG DERIVED FROM THE NATIVE

Betel nut. Seed of Areca Catechu. India.
Calamus. Rootstock of Acorus Calamus. Eastern U. S. and
in Asia.
Sarsaparilla. Roots of various species of Tropical America.
Smilax.
Saffron. Stigmas of Crocus sativus. Europe.
Arrowroot. Rootstock of Maranta arundinacea. Tropical America.
Cubeb. Unripe fruit of Piper Cubeba. Old World tropics.
Creosote. Wood of Fagus americana North America and
and F. sylvatica. Europe.
Hydrastis. Rootstock of Hydrastis canadensis. Eastern N. America.
Star Anise. Fruit of Illicium anisatum. Southern China.
Camphor. All parts of Cinnamomum China and Japan.
Camphora.
Witch-hazel. Leaves and bark of Hamamelis Eastern N. America.
virginiana.
Licorice. Underground parts of Glycyrrhiza Europe.
glabra.
Cascara Bark of Rhamnus Purshianus. Western United
Sagrada. States.
Ginseng. Rootstock of Panax quinquefolium. Eastern N. America
and Asia.
Wintergreen. Leaves of Gaultheria procumbens. Eastern N. America.
Nux vomica. Seeds of Strychnos Nux India.
vomica.
Digitalis. Leaves of Digitalis purpurea. Europe.
Ipecac. Root of Uragoga Ipecacuanha. Brazil.
Castor oil. Seeds of Ricinus communis. Africa or India.

6. THE STORY OF TOBACCO

Not until 1492 was the use of tobacco known to the Europeans, when
Columbus found the natives of Cuba and Santo Domingo both chewing and
smoking it. Subsequent Spanish explorers of the mainland found its use
almost universal both in North and South America. It had apparently been
used there for countless ages, as smoking it formed part of the most
solemn ceremonial rites both of the natives’ religion and their
political gatherings. Brought to England in 1586 by Ralph Lane and Sir
Francis Drake, the smoking of tobacco spread with the great speed that
such a comfortable habit might be expected to exhibit. Notwithstanding
violent opposition by certain priests and physicians and other more
intolerant opponents of the weed, its use increased throughout the
world. To-day, in spite of our modern anti-tobacco fanatics, over two
billion pounds are produced annually, and in the United States there is
a per capita consumption of over five pounds per year, greater than any
country in the world, save Belgium.

All of the many different forms in which tobacco is used are derived
from the leaves of _Nicotiana tabacum_, or perhaps one or two other
species of the genus _Nicotiana_, which belongs to the _Solanaceæ_ or
potato family. There are many other species, all natives of the New
World, but the actual home of the tobacco plant is in some doubt. As in
so many cultivated plants, which have been grown for countless ages,
wild specimens are practically unknown. The plant seeds freely and
consequently frequently escapes from cultivation, so that in many parts
of America apparently wild plants are to be found that

[Illustration: TEMPERATE FOREST ON GARDINER’S ISLAND, LONG ISLAND, N. Y.
Note the open vista through the trees, and lack of undergrowth, due to
the forest canopy, and contrast with the profusion of the under
vegetation in the rain forest (_Courtesy of Brooklyn Botanic Garden._)]

[Illustration: RAIN FOREST. Root-climbing lianas on a tree stem in the
south Mexican rain forest (State of Chiapas). Below: _Sarcinanthus
utilis_, with bipartite leaves. Farther up: _Araceæ_. Highest of all:
epiphytic shrubs are visible near leaves of _Araceæ_. Around the stem,
the cord-like aerial roots of _Araceæ_ on the branches of the tree. (_A
photograph by G. Karsten._) (_After Schimper. Courtesy of Brooklyn
Botanic Garden._)]

trace their origin to cultivated plants. The antiquity of its culture
may be gauged by the fact that in the most ancient Aztec tombs
elaborately carved tobacco pipes have been found.

The plant is grown as a field crop in rows from one and one-half to
three feet apart and set about fifteen inches apart in the row. From the
time the seed is sown until the harvesting of the leaves is usually
three or four months, during which the plants demand the best of
culture. In the United States thousands of acres of tobacco are now
grown under cheesecloth shades, an expensive process which is more than
compensated for by the improved flavor.

Once the tobacco is cut there begin chemical changes in the leaves that
are of great importance to its subsequent flavor and use. These are
aided or induced first by a process of curing, which is accomplished by
suspending the wilted leaves in the sun, a process that has been
practically abandoned for curing by artificial heat. The leaves are hung
in a building where slow fires bring the temperature up to 150 degrees
F., which is maintained for a few days. The cured tobacco is then
gathered into small bundles which are stacked or packed so closely that
fermentation begins, often generating a temperature of 150 degrees F.
The bundles are then reshifted and the process allowed to start again,
which may be done several times, depending upon the quality of the leaf,
flavor desired, and commercial requirements. Enzymes and bacteria play a
large part in the fermentation process and inoculation of poor grades of
tobacco with the organisms of finer grades has been tried. After
fermentation has been stopped practically all tobaccos are aged for at
least two years, some for longer periods.

In Cuba, where its use was first noticed, the finest tobacco in the
world is still produced, notably in the province of Pinar del Rio. It is
still something of a mystery as to what peculiar combination of soil,
climate, or handling the unquestionable superiority of the Cuban leaf is
due. For one thing it is grown in the open, without shade, and is never
cured by artificial heat. Nor is the very excellent cigarette tobacco of
Turkey ever artificially cured. But attempts to imitate the conditions
under which these finest grades of tobacco are produced outside Cuba and
Turkey have never been really successful, so that those countries have
practical monopolies on the production of the finest cigars and
cigarettes. The weed is cultivated nearly throughout the world, even
Canada producing considerable quantities, but the best kinds and
greatest production is in warmer regions. It is second only to the sugar
crop in Cuba, and the United States produces over one-third the world’s
total supply. Immense quantities are grown, however, in India and
Sumatra, and in the Philippines.

Perhaps the most unusual and localized conditions of climate and
subsequent handling are found in the production of perique tobacco. All
the world’s supply is grown on a ridge at Grand Point, in the parish of
St. James, Louisiana. The leaves are subjected to great pressure and the
expressed juice, after oxidation, is reabsorbed by the leaves after the
pressure is removed. The peculiar flavor is apparently due to this and
to the damp climate. Perique is now used throughout the world as an
ingredient of the better kinds of pipe tobacco.

The diseases and breeding of different strains of tobacco are commercial
factors of tremendous importance to the industry. With a yearly value of
well over two billions of dollars, the crop is one of the most important
plant products, outside of foods. The capital invested in America alone
is over five hundred million dollars.

7. SPICES

As we have seen many of our most valuable food plants are natives of and
are now cultivated in temperate regions, but “sugar and spice and all
things nice” mostly come from the tropics. What we usually know as
spices such as nutmeg, vanilla, ginger, mace, cloves, allspice, and
cinnamon are practically all confined to the tropical regions in or near
the East Indies, only vanilla being of American origin. The trade in
these spices has been for hundreds of years a practical monopoly in the
hands of Dutch and British traders, and for hundreds of years before
that the caravans from the Far East came laden with precious freight
from the then mysterious country beyond the Mediterranean.

VANILLA

The long pods of two climbing orchids native in Central America and the
West Indies furnished for many years our only supplies of this flavoring
extract. But in 1891 a process of making vanilline chemically from sugar
was perfected so that the vanilla trade is not what it was years ago.
Vanilla planters, however, have been able to keep up the price of the
plant product because of its unquestionable superiority over the
manufactured article. But the latter has enormously increased the
general use of vanilla, while the total plant output scarcely exceeds
four hundred tons a year. Nearly all this is grown in the Old World
tropics, as tropical America, where the plant is common enough as a
forest orchid, has not greatly developed its culture.

In both species, known as _Vanilla pompona_ and _Vanilla planifolia_,
the orchid has flat leaves and a fleshy climbing stem that hugs tree
trunks or other supports, always in the dense shade of the tropical
forests. It needs a hot moist climate, but if there be too much rain as
the pods are ripening they drop off, so that only certain localities are
suited to its cultivation. Various islands are apparently better suited
to the plant than the mainland, Tahiti producing alone nearly half the
world’s supply. The species most cultivated is _Vanilla planifolia_,
which came originally from southern Mexico, where considerable
plantations are still maintained. The pods are about as thick as a thumb
or finger and from five to seven inches long, and yellow when ripe. The
ripening process takes several months and when completed the pod is
still without the delicious fragrance for which it is famous. Curing by
dipping in boiling water or by fermentation, a very delicate process
requiring long experience, brings out the flavor. In some regions the
pods are plunged into ashes and left there until they begin to shrivel
when they are cleaned off, rubbed with olive oil, and tied at their
lower end to prevent splitting. Still another process demanding that the
pods be plunged in rum is followed, but only in limited degree, owing to
the expense. In all of them the result is the same--that of inducing
chemical changes in the pod which are responsible for its subsequent
flavor.

NUTMEG

[Illustration: FIG. 104.--NUTMEG (_Myristica fragrans_)

A native of southeastern tropical Asia. The fruit, somewhat enlarged
here, consists of an inner part, the nutmeg. Around this is a “splendid
crimson network” which is removed by hand and forms the mace of
commerce.]

A small tree of the tropical regions of eastern Asia, known as
_Myristica fragrans_, or perhaps better as _Myristica moschata_, is the
source of both nutmeg and mace which come from different parts of the
same plant. The genus contains over one hundred species, belongs to the
_Myristicaceæ_, and is scattered all over the Malayan region. Almost
none of its relatives, however, have the fragrance of the nutmeg and
none is used as a spice. Both nutmeg and mace have been known in Europe
only from about 1195 A.D., when in a poem about the entry of the Emperor
Henry VI into Rome, the streets were described as being perfumed by the
burning of nutmegs and other fragrant plants. It was not until the rise
of the Dutch, who burned large stores of it at Amsterdam in 1790 in
order to keep up a falling price, that nutmegs came into general use.
The trees are now chiefly cultivated in the Dutch East Indies, a small
fraction of the supply coming from the West Indies, which is alleged to
be an inferior product.

The trees produce male and female flowers, usually on different plants,
but sometimes on the same one, yellow in color and aromatic. From the
females are developed the fruit which is a drupe about two inches long
with a thick fleshy husk which splits upon ripening. The seed inside is
the nutmeg, but from its base is an outgrowth which covers the nut with
a “splendid crimson network.” This covering or network is removed by
hand and forms the mace of commerce.

CLOVES

In the family _Myrtaceæ_, which contains hundreds of plants from all
over the world, mostly all shrubs and trees of tropical regions,
however, there is a large genus, _Eugenia_. From the unopened flower
buds of _Eugenia caryophyllata_, a small tree native only on a few
islands in the Moluccas, the widely used spice known as cloves is
derived. It appears to have been known to the Chinese at least two
hundred years before Christ, and was regularly imported into Europe from
the eighth century by caravans. Not until the Dutch began to import it
by ship did it become cheap enough to have general use, but in 1609 a
Dutch vessel reached England with over a hundred thousand pounds on
board.

While the tree is of very local distribution, it has been introduced on
a considerable scale into Penang, Zanzibar, and even to the West Indies.
Trees are set out thirty feet apart each way, and in from four to eight
years, depending on the locality, they begin to flower. After the full
bearing stage is reached, a tree will produce from five to seven pounds
of dried cloves, an average crop being about 375 pounds to an acre. The
flowers are produced in small clusters not over an inch and a half long,
so that hand picking is the only method of collection. As the buds
become blood red they are usually in a fit state for picking, after
which they are either sun dried or, more rarely, by artificial heat.
Nothing further is done to them before shipment. Zanzibar and Pemba now
produce more cloves than nearly all the rest of the world put together.
Oil of cloves, largely used in perfumery, is pressed out of the dried
cloves.

[Illustration: FIG. 105.--CLOVE PLANT

A native of only a few islands in the Moluccas. Cloves consist of the
unopened flower buds of _Eugenia caryophyllata_.]

CINNAMON

One of the commonest trees in the lowland parts of Ceylon is _Cinnamomum
zeylanicum_, a tree of the family _Lauraceæ_, which also contains our
native sassafras. From the bark of this tree is derived cinnamon, and
from a related Japanese tree, _Cinnamomum Camphora_, camphor is taken.
Practically all the _Lauraceæ_ are aromatic shrubs or trees, most of
them tropical. Ceylon was occupied by the Portuguese in 1536 for the
cinnamon then growing on it, which they forced the native king to supply
them. Later the Dutch completely controlled the cinnamon, often burning
it in Holland to keep up the price. The British, who took Ceylon in
1796, made a government monopoly of cinnamon, but subsequently turned
the plantations over to private interests. The tree is now grown on an
extensive scale, not only in Ceylon, but in Java and India. Ceylon still
controls the cinnamon market, however.

[Illustration: FIG. 106.--CINNAMON

A common tree of Ceylon (_Cinnamomum zeylanicum_). From the related
_Cinnamomum Camphora_ camphor is derived.]

While the wild cinnamon trees reach considerable heights, the cultivated
plants are cut so regularly that they almost always throw up a lot of
young shoots from the roots, and it is the bark of these that furnishes
the spice. When the bark is fit for peeling, the natives cut off the
shoots, and strip the bark from them by hand, but with a specially
constructed knife. After removal the bark is kept moist and in a day or
two the outer skin is scraped off and the bark stretched over a stick,
to form the familiar pipes or quills of cinnamon. These are graded, cut
to uniform length, and after drying are ready for shipment. All of this
is as yet hand work.

Other spice plants and condiments are of wide use, but can scarcely be
mentioned in detail here. A few of the more important are the following:

NAME DERIVED FROM THE NATIVE

Allspice or pimento Unripe fruits of West Indies.
_Pimenta officinalis_

Cassia bark Bark of _Cinnamomum Cassia_ Eastern Asia.

Black pepper Fruit of _Piper nigrum_ Tropical Asia.

Cardamoms Fruit of _Elettaria Cardamomum_ Malabar.

Capsicum or Cayenne Fruits of species of _Capsicum_ Tropical Asia.
pepper

Coriander Fruits of _Coriandrum sativum_ Europe.

Cumin Fruits of _Cuminum Cyminum_ Mediterranean
region.

Dill Fruits of _Peucedanum graveolens_ Europe and
northern Africa.

Ginger Rootstock of (?)
_Zingiber officinalis_

Turmeric Rootstock of _Curcuma longa_ Tropical Asia.

Mustard Seed of _Brassica nigra_ and _alba_ Old World.

Thyme Foliage of _Thymus vulgaris_ Southern Europe.

Caraway Fruit of _Carum Carui_ Europe.

Caper Seeds of _Capparis spinosa_ Southern Europe
and Asia.

This brief review of what the plant world provides us with in the shape
of foods, beverages, fibers, drugs, rubber, spices, and tobacco, does
not begin to tell us what man’s debt to plants really is. Thousands of
plants, used by natives all over the world, may well provide future
generations with unsuspected sources of plant products. No mention has
been made of timbers nor all the forest products, except paper, which in
the aggregate total an enormous sum. Perhaps no better idea of the
tremendous value of plants, of the absorbing interest their utilization
has always had for man, can be gained than to refer the reader to
incomparably the best book on the subject, so far as tropical plants
are concerned. Sir George Watt, in his “Dictionary of the Economic
Products of India,” a book of several volumes, most of which deals with
plants, has left an imperishable record of man’s struggles to tame the
wild plants of the forest to his needs.

A few more economic plants not yet noted are listed below, and with this
our account of plants as they are used by man must close:

PLANT PRODUCT DERIVED FROM THE NATIVE OF

Absinthe Foliage of _Artemisia absinthium_ Europe.

Brazil nut Seeds of _Bertholletia excelsa_ Tropical S. America.

Camomile Flowers of _Anthemis nobilis_ Europe.

Cassava Roots of species of _Manihot_ Tropical America.

Water chestnuts Fruits of _Trapa natans_ Southern Europe.

Cohune nut Fruits of _Attalea Cohune_ Central America.

Cork Bark of _Quercus Suber_ Southern Europe and
northern Africa.

Gamboge resin Stems of species of _Garcinia_ Southeastern Asia.

Gum arabic Exudation of species of Tropical Asia and
_Acacia_ Africa.

Hops Female flowers of Eastern Europe.
_Humulus Lupulus_

Indigo Whole plant of India.
_Indigofera tinctoria_

Mushroom Whole plant of Temperate regions.
_Agaricus campestris_

Teak Wood of _Tectona grandis_ Southeastern Asia.

Japanese varnish
or lacquer Sap of _Rhus vernicifera_ China.

CHAPTER VI

GARDEN PLANTS

Not only does the plant world furnish us with all the multitudinous
products that we have already noticed, but it makes possible the
beautifying of our homes and parks. For with plant materials, anyone
with the knowledge and taste necessary for work of this kind may paint
living landscape pictures that grow in beauty as their individual units
reach maturity.

It lies outside the scope of this book to tell you the principles of
design upon which such landscape pictures must be based to be really
effective--that is the function of the landscape architect. But every
one of us knows when a house looks and is bare of vegetation about it,
and consequently has the earmarks of being merely a house, but not a
home. A walk through any suburb of a large city or through most of our
American villages would convince the lover of gardening that we are
still miles behind England and many other countries in the love and
appreciation of that kind of beauty in our home surroundings which plant
life alone can furnish. How unnecessary this is anyone can see by
visiting certain distinguished exceptions to the general indifference to
plant life about our homes. Such suburbs as Brookline near Boston,
Garden City and Morristown near New York, Guilford at Baltimore,
Germantown near Philadelphia and many places on the Pacific Coast show
what can be done to transform an otherwise indifferent landscape into a
beauty spot. While these are on the whole the homes of the wealthy,
money is not what has made them, for thousands of cottage gardens in
England are just as beautiful and have been made by people who live a
busy industrial life, but whose desire for beautiful surroundings makes
them spend their brief leisure in tending their flowers.

While large garden schemes demand somewhat expert advice as to their
planning and arrangement, it is perfectly simple for anyone to begin
planting his own home grounds if he has in his mind’s eye the ultimate
picture which he wishes his house and garden to become. But the habits
of plants, their growth requirements, their stature, and particularly
their colors are so various that, with the best will in the world, a
garden enthusiast without some knowledge of these things will get a
wholly disappointing result. Certain plants will grow in some sections
of the country, but fail in others; some flower in the south, but will
not do so in the north, and a few set seeds in certain places, but never
do in less favored regions. In the different sections of this chapter a
few good garden plants will be noted according to the regions to which
they are suited, but it must not be forgotten that some are suited also
to other regions than the one in which they are listed.

Those who have read the earlier chapters already know the difference
between annuals, biennials, and perennials which comprise all the
herbaceous plants upon which we depend mostly for cut flowers and in
large measure for giving color to the garden. The woody plants are the
ones upon which most garden pictures depend for their permanent
value--trees, shrubs and vines of infinite shape and foliage character.
In the case of trees, there are two major classes, those that drop their
leaves in fall and are therefore deciduous, and of value chiefly during
the growing season; and the evergreens, which retain their foliage all
the year and make winter landscapes of great beauty. The garden
enthusiast will very soon learn that evergreen plantings, while in many
ways the most beautiful, are much the most expensive and are never
suited to regions near big cities, for they will not stand smoke and
other fumes as many deciduous trees will do. Nor will they stand violent
winds, small rainfall, and great summer heat such as characterize the
central parts of the country. Their best development is therefore found
east of the Mississippi and west of the Rockies, and generally speaking,
their use in the garden should be confined to this region.

PLANT MATERIALS FOR THE GARDEN

TREES

So much of what makes landscapes permanently beautiful depends upon
trees that first place must always be given to them in any scheme of
planting. The location and ultimate spread of these trees will
infallibly make or mar any garden picture so that great care should be
used in selecting and planting them. The actual planting details such as
preparation of the soil and all the after care of plants cannot be dealt
with here, but many nursery catalogues give accurate directions and
there are hosts of books on the practice of gardening which give the
necessary information. In listing the different trees, symbols will be
put before the names, indicating in which region they are likely to grow
best, as follows:

* Suited to the region east of the Mississippi and north of the
frostless region of the Gulf States, but not all hardy in the
northern part of United States and adjacent Canada.

** Suited to the same general region, but most at home in the
northern part of the area.

Those that have no symbol before the name are understood to be,
generally speaking, hardy throughout the country, with, of course,
exceptions such as the desert and alkali regions of the country.

EVERGREENS

* White Pine, _Pinus Strobus_.
* Austrian Pine, _Pinus Austriaca_.
* Scotch Pine, _Pinus sylvestris_.
* Pitch Pine, _Pinus rigida_.
** Red Pine, _Pinus resinosa_.
* Umbrella Pine, _Sciadopitys verticillata_.
* White Fir, _Abies concolor_.
** Fraser’s Fir, _Abies Fraseri_.
* Nordman’s Fir, _Abies Nordmanniana_.
* Norway Spruce, _Picea excelsa_.
** White Spruce, _Picea alba_.
** Red Spruce, _Picea rubens_.
* Koster’s Blue Spruce, _Picea pungens glauca_.
* Engelmann’s Spruce, _Picea Engelmannii_.
* Juniper. Different species of the genus _Juniperus_,
mostly low growing and suitable for ground covers.
* Japanese Cypress, _Retinospora obtusa_. There are many
garden varieties.
* Southern Cypress, _Taxodium distichum_. Not hardy in
the northern part of the area. Best in wet places.
* Lawson’s Cypress, _Chamæcyparis Lawsoniana_.
* English Yew, _Taxus baccata_.
** American Yew, _Taxus canadensis_.
* Hemlock, _Tsuga canadensis_.

Of these the Austrian pine, hemlock, and the firs have the densest
foliage and should be used for such effects. Almost nothing will grow
under the evergreen trees, so close is their foliage. Lack of light and
the acid leached out of their bark by rains, stop the growth of nearly
all herbs underneath them.

DECIDUOUS TREES

Planted mostly for their foliage masses, but a few bear showy flowers
and such will be noted. The same symbols apply.

* American Beech, _Fagus ferruginea_.
* European Beech, _Fagus sylvatica_.
* White Oak, _Quercus alba_.
* Red Oak, _Quercus rubra_, the most rapid grower of all
the oaks.
* Scarlet Oak, _Quercus coccinea_.
Horsechestnut, _Aesculus Hippocastanum_.
* Norway Maple, _Acer platanoides_.
* Red Maple, _Acer rubrum_. Prefers moist places.
Sugar Maple, _Acer saccharum_.
* Silver Maple, _Acer saccharinum_. Fine tree with interesting
branching, but brittle.
* Tulip Tree, _Liriodendron tulipifera_. Showy orange-green
flowers.
* American Plane Tree, _Platanus occidentalis_. A native
tree, but not so satisfactory as
* Oriental Plane Tree, _Platanus orientalis_.
* Sweet Gum, _Liquidambar styraciflua_.
White-leaved Poplar, _Populus alba_.
Balsam Poplar, _Populus balsamifera_.
* Flowering Plum, _Prunus Pissardi_ and many other varieties
and species of the genus _Prunus_ such as Japanese
Flowering Cherries and Plums.
* American Elm, _Ulmus americana_.
* English Elm, _Ulmus campestris_.
* Maidenhair Tree, _Ginkgo biloba_. Not hardy in the northern
part of the area.
Black Locust, _Robinia Pseudacacia_. Showy pink flowers.
European White Birch, _Betula alba_.
Black Alder, _Alnus glutinosa_.
Ash, _Fraxinus americana_.
* Dogwood, _Cornus florida_. Showy white bloom. Tree will
not grow well unless in partial shade.
* Cornelian Cherry, _Cornus Mas_. Covered with yellow
flowers before the leaves come out in early spring.
* European Hornbeam, _Carpinus Betulus_.
Weeping Willow, _Salix Babylonica_.
Box Elder, _Acer Negundo_.
* Magnolias. Different trees and some shrubs of the genus
_Magnolia_ all with showy flowers. Rather tender and
cannot be grown without considerable care, especially
when young.
Honey Locust, _Gleditsia triacanthos_.
Catalpa, _Catalpa speciosa_. Showy flowers.
* _Paulownia imperialis._ Showy flowers, but not hardy in
northern part of the area.

There are many other deciduous and evergreen trees that might be listed
and which will be found in the nursery catalogues of dealers in
different parts of the country. Some of these require special conditions
of soil and climate and should not be planted unless these conditions
are understood. In the frostless region of the country many plants can
be grown that are of tropical or near-tropical origin, but no list of
them will be included here. Some of them are hardy as far north as
Washington, D. C., and are worth trying by anyone living in this region,
as they give us effects not possible with the trees noted.

SHRUBS

While trees make the major feature of any garden, shrubs are chiefly
used to fill in between them, or in small gardens the only woody plants
that can be used are often shrubs. Within the last two or three years
the Government has prohibited the importation of plants from abroad,
upon the ground that various insect pests and fungous diseases were
likely to be carried into the country upon such plants. For this reason
American gardeners will have to propagate their own plants and we shall
have to use more native plants than European and Asiatic species, which
made up the bulk of our gardening material in the past.

There are excellent reasons for using native shrubs upon quite other
grounds than the difficulty or danger of importing foreign ones. Native
plants fit into the natural landscape better than introduced sorts, and
very often the garden enthusiast can go out into the country and dig out
small specimens instead of buying them.

In the list of native American shrubs given below, there are directions
of where to use them, their heights, their flower color and other
information about them that will help the amateur gardener to select his
shrubs for definite effects. All of the shrubs listed can be gown in
most parts of the country, and from the list nearly every wish of the
garden planner may be gratified. This list is a practical one and has
been used by landscape architects and others. It was written by the
author for “The Garden Magazine” whose publishers, Doubleday, Page &
Company, have kindly allowed its use here.

It will be noted that under each month group the names are arranged in
botanical sequence so that allied plants are brought together. All the
ninety-four species are offered for sale in American nurseries. Those in
the column “Remarks and Notes” as well as about twenty others not
included, must be collected in the wild.

A word now as to cultivation and care. Most of the shrubs, except those
so noted, can either be planted in the spring or fall, as this is a
matter that should be determined by the planter’s convenience. In
digging the holes make them twice as wide and deep as the size of the
roots apparently demand. Note carefully the column “Preferred Habitat,”
so that the shrubs may find congenial surroundings. Pack the soil well
around the roots, water thoroughly, and frequently if the weather is dry
and windy. The first winter or two a heavy mulch of leaves, or leaves
and manure mixed, to be dug in the following spring, will well repay the
expense and trouble.

It will be noted that some of the shrubs are marked with an asterisk
(*). These all belong to the heath family and require special treatment.
A soil composed of rotten sods and leafmold, about half and half, is
most essential for the successful cultivation of these plants. They
require peculiar acid soil conditions well approximated by the above
mixture, and a mulch, preferably of red-oak leaves, or the leaves of the
mountain laurel if available. Never disturb the roots of these plants by
digging in the mulch, which is better left on indefinitely. Soils with
much lime in them must also be avoided when growing these heath-family
plants.

It is often somewhat difficult in arranging a shrubbery planting to
group the plants according to the color of their flowers. For the
greater ease in using the larger table, and so that one can arrive at
the relative frequency of the various colors desirable for use in the
scheme, the following table is appended. The numbers refer, of course,
to those in the table below. The figures given in parentheses are the
total of plants in each division.

_By color of flowers._ Yellow-green (10): 1, 8, 9, 10, 30, 31, 36,
44, 49, 86. Brown-green (10): 2, 3, 4, 11, 12, 13, 14, 15, 27, 39.
Yellow (5): 5, 25, 41, 84, 92. Pink-purple (4): 7, 74, 75, 83.
White (35): 6, 17, 18, 19, 20, 21, 22, 24, 28, 29, 32, 40, 42, 43,
45, 46, 47, 51, 55, 57, 58, 59, 69, 70, 71, 72, 76, 78, 79, 80, 81,
82, 88, 89, 90. Green-white (11): 16, 23, 33, 50, 52, 63, 64, 65,
66, 87, 94. Pinkish-white (10): 26, 37, 38, 54, 56, 61, 67, 73, 77,
93. Pink (5): 34, 60, 62, 85, 91. Lilac (1): 35. Violet-purple (2):
48, 68. Orange-red (1): 53.

It often happens, too, that we have some definite spot, such as a small
stream or swamp, a dry hill-side, or a shaded wood, that we wish to
beautify. Therefore:

_By preferred habitat of shrubs._ Moist places (19): 1, 2, 4, 9,
15, 17, 30, 36, 42, 50, 75, 78, 82, 83, 84, 85, 87, 88, 89.
Indifferent (32): 3, 5, 6, 7, 12, 14, 24, 29, 32, 35, 37, 38, 41,
43, 45, 47, 48, 51, 52, 59, 60, 61, 62, 68, 70, 71, 72, 79, 80, 81,
90, 91. Shaded woods (13): 8, 16, 23, 25, 26, 27, 31, 63, 65, 67,
69, 74, 92. Dry places (19): 10, 13, 18, 20, 21, 22, 34, 39, 46,
49, 53, 54, 56, 58, 64, 77, 86, 93, 94. Swamps (6): 11, 40, 55, 66,
73, 76. Thickets (1): 19. Cool woods (4): 28, 33, 44, 57.

In planning a screen for an unsightly fence or building, or to cover up
some small landscape importunity, it is often essential to know, _en
masse_, the heights of shrubs for such purposes. The following table
gives the dimensions of the shrubs, normal individuals averaging about
midway of the extreme heights given.

_By height of shrubs._ One to four feet (13): 2, 6, 21, 27, 34, 56,
62, 75, 77, 83, 84, 91, 93. Two to five (24): 10, 11, 13, 16, 22,
25, 31, 36, 37, 42, 44, 53, 57, 60, 61, 65, 67, 69, 73, 81, 82, 85,
90, 94. Three to nine (29): 3, 4, 8, 12, 14, 15, 17, 20, 26, 28,
32, 33, 35, 38, 39, 41, 43, 45, 48, 54, 58, 59, 70, 72, 74, 78, 80,
86, 88. Six to fifteen (21): 1, 5, 7, 18, 19, 29, 40, 46, 47, 49,
50, 52, 55, 64, 68, 71, 76, 79, 87, 89, 92. Ten to eighteen (7): 9,
23, 24, 30, 51, 63, 66.

PLANTING TABLE FOR OUR NATIVE SHRUBS[3]

Rhododendrons and azaleas, hundreds of varieties of which are known and
admired by all garden lovers, are mostly derived from Asiatic species,
and under the new law have become rare and expensive in this country. A
few American nurserymen are able to propagate them so that we can still
get plants of these showiest of all shrubs. They should not be used in
regions where there is scant rainfall, very hot summers, high winds or
extreme winters. Their use is practically confined to the region east of
the Alleghenies.

GARDEN HERBS

The foregoing lists of shrubs and trees give sufficient information so
that all garden enthusiasts can at least make the broad outlines of a
garden picture. It must never be forgotten that these woody plants are
the only really permanent things in the scheme and should therefore be
placed with more care and thought than the herbs, which can be moved at
will. In selecting herbs, two chief divisions of them should be kept in
mind; annuals which are planted for quick effects and which die down at
the end of the year, and perennials which live year after year and
produce flowers usually after the second year. It is from perennials
that the great bulk of our fine garden plants are derived. Planted in
beds or better yet among shrubbery or on shrub-backed borders they are
the most beautiful and most satisfactory of all herbaceous plants.

Most of them may be started from seed in August of any year and grown
along through the balance of that growing season, after which they
should be covered up with straw or manure. The following season at least
three-quarters of them will flower and by their third season all of them
will do so.

COLOR, SEASON, AND HEIGHT OF HARDY PERENNIALS

A study of the following list will show any garden amateur how he may
group his perennials in borders or beds and how he can get different
color effects at different seasons and in plants of different heights.
This admirable list of perennial plants was prepared by Charles Downing
Lay, a landscape architect, and published by “Landscape Architecture.”
The editors of that publication and Mr. Lay have kindly consented to
having the list reprinted here.

+=================================================++====================================================+
| COLOR || |
+----+-----+------+------+---+----+--------+------|| HARDY GARDEN PERENNIALS |
|Pink|White|Yellow|Orange|Red|Blue|Lavender|Purple|| |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Achillea Ptarmica fl.-pl., The Pearl |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || Millefolium, Cerise Queen |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | --|-- | || Aconitum autumnale. Monkshood |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----|---- | ---- | |---| | | || Althæa rosea. Hollyhock |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || Alyssum saxatile compactum. Golden Tuft |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Anchusa italica var. Dropmore. Alkanet |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || sempervirens. Alkanet |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Anemone japonica. Japanese Windflower |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || japonica, Queen Charlotte. Japanese Windflower |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Anthemis tinctoria. Marguerite |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | |----| | || Aquilegia Helenæ. Columbine |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | |---| | | || canadensis. Columbine |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || chrysantha. Columbine |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | |---|----| | || formosa hybrida. Columbine |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || haylodgensis. Columbine |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || vulgaris nivea grandiflora. Columbine |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Arabis alpina. Alpine Rock Cress |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || Armeria plantaginea. Sea Pink |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Artemisia lactiflora. White Mugwort |
+----+-----+------+------+---+----+--------+------++----------------------------------------------------+

+====================================================++============================================++==================================================+
| || SEASON || HEIGHT |
| HARDY GARDEN PERENNIALS ||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| ||April|May|June|July|August|September|October||6 inches|1 foot|2 feet|3 feet|4 feet|5 feet|6 feet|
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Achillea Ptarmica fl.-pl., The Pearl || | |----|----| | | || | ---- | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Millefolium, Cerise Queen || | |----|----| | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Aconitum autumnale. Monkshood || | | | | --|-- | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Althæa rosea. Hollyhock || | | | | | | || | | | | | ---- | ---- |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Alyssum saxatile compactum. Golden Tuft || | | | | | | || | ---- | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Anchusa italica var. Dropmore. Alkanet || | | --|-- | | | || | | | --| ---- |-- | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| sempervirens. Alkanet || | --|-- | | | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Anemone japonica. Japanese Windflower || | | | | --| ---- | ---- || | --| ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| japonica, Queen Charlotte. Japanese Windflower || | | | | --| ---- | ---- || | --| ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Anthemis tinctoria. Marguerite || | | | --|-- | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Aquilegia Helenæ. Columbine || | --|----|-- | | | || | --| ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| canadensis. Columbine || | --|----|-- | | | || | | ---- |-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| chrysantha. Columbine || | | --|----|-- | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| formosa hybrida. Columbine || | | --|----|-- | | || | | ---- |-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| haylodgensis. Columbine || | --|----|-- | | | || | --| ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| vulgaris nivea grandiflora. Columbine || | --|----|-- | | | || | | ---- |-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Arabis alpina. Alpine Rock Cress || --|-- | | | | | || ---- |-- | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Armeria plantaginea. Sea Pink || | --|----| | | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Artemisia lactiflora. White Mugwort || | | | | --|-- | || | | | | --| ---- |-- |
+----------------------------------------------------++-----+---+----+----+------+---------+-------++--------+------+------+------+------+------+------+

+=================================================++====================================================+
| COLOR || |
+----+-----+------+------+---+----+--------+------|| HARDY GARDEN PERENNIALS |
|Pink|White|Yellow|Orange|Red|Blue|Lavender|Purple|| |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | ---- | | | | || Asclepias tuberosa. Butterfly Weed |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | --|-- | || Aster alpinus. Alpine Aster |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----|-- | || novæ-angliæ. New England Aster |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | --|-- | || tataricus. Late-blooming Aster |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | | ---- | || Thomas S. Ware |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Baptisia australis. False Indigo |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----|---- | | | | | | || Bellis perennis. English Daisy |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Boltonia asteroides. False Chamomile |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| -- |-- | | | | | | || latisquama nana. Dwarf False Chamomile |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | |----| | || Campanula carpatica. Carpathian Harebell |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----|---- | | | |----| | || Medium. Canterbury Bells (Biennial) |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | |----| | || persicifolia grandiflora. Peach Bells |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | |----| | || pyramidalis. Chimney Bellflower |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || rapunculoides |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Centaurea montana. Mountain Bluet |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Cerastium tomentosum. Snow-in-Summer |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----|---- | ---- | ---- |---| | | || Chrysanthemum, Hardy Pompons |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || maximum |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Clematis heracleæfolia (C. tubulosa) |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || recta. Herbaceous Clematis |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || integrifolia. Herbaceous Clematis |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Convallaria majalis. Lily of the Valley |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || Coreopsis lanceolata grandiflora. Tickseed |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | --|-- | || Delphinium belladonna. Larkspur |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || formosum. Larkspur |
+----+-----+------+------+---+----+--------+------++----------------------------------------------------+

+====================================================++============================================++==================================================+
| || Season || Height |
| HARDY GARDEN PERENNIALS ||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| ||April|May|June|July|August|September|October||6 inches|1 foot|2 feet|3 feet|4 feet|5 feet|6 feet|
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Asclepias tuberosa. Butterfly Weed || | | | --|-- | | || | | --| ---- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Aster alpinus. Alpine Aster || | --|-- | | | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| novæ-angliæ. New England Aster || | | | | --|-- | || | | | | --| ---- |-- |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| tataricus. Late-blooming Aster || | | | | | --| ---- || | | | | | --|-- |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Thomas S. Ware || | | | | --|-- | || | | | --|-- | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Baptisia australis. False Indigo || | | --|-- | | | || | | | | --| ---- | ---- |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Bellis perennis. English Daisy || | --|-- | | | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Boltonia asteroides. False Chamomile || | | --|----| ---- |-- | || | | --| ---- | ---- | ---- | ---- |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| latisquama nana. Dwarf False Chamomile || | | --|----| ---- | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Campanula carpatica. Carpathian Harebell || | | | --| ---- |-- | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Medium. Canterbury Bells (Biennial) || | | --|-- | | | || | --| ---- |-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| persicifolia grandiflora. Peach Bells || | | --|-- | | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| pyramidalis. Chimney Bellflower || | | | | ---- |-- | || | | | | -- |-- | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| rapunculoides || | | |----|-- | | || | | --| ---- |-- | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Centaurea montana. Mountain Bluet || | | --|----| ---- | | || | --| ---- | -- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Cerastium tomentosum. Snow-in-Summer || | | --|----| | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Chrysanthemum, Hardy Pompons || | | | | | --|-- || | | --| ---- |-- | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| maximum || | | --|----| ---- | | || | | ---- |-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Clematis heracleæfolia (C. tubulosa) || | | | --|-- | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| recta. Herbaceous Clematis || | | | --|-- | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| integrifolia. Herbaceous Clematis || | | | --| ---- | | || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Convallaria majalis. Lily of the Valley || --|---| | | | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Coreopsis lanceolata grandiflora. Tickseed || | | --|----| ---- |-- | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Delphinium belladonna. Larkspur || | |----| | | ---- |-- || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| formosum. Larkspur || | |----| | | ---- |-- || | | --|-- | | | |
+----------------------------------------------------++-----+---+----+----+------+---------+-------++--------+------+------+------+------+------+------+

+=================================================++====================================================+
| COLOR || |
+----+-----+------+------+---+----+--------+------|| HARDY GARDEN PERENNIALS |
|Pink|White|Yellow|Orange|Red|Blue|Lavender|Purple|| |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | |----| | || Delphinium grandiflorum chinense., Larkspur |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| --|-- || Kelway’s Hybrids |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Dianthus barbatus. Sweet William |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || barbatus, Newport Pink |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | |---| | | || barbatus, Scarlet Beauty |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || plumarius. June Pink, Clove Pink |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || plumarius, Mrs. Sinkins |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || plumarius, White Reserve |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || Dicentra eximia |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || spectabilis. Bleeding-Heart |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----|---- | | | | | | || Dictamnus Fraxinella. Gas Plant |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----|---- | | | | | | || Digitalis purpurea. Foxglove |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || sibirica. Siberian Foxglove |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || Doronicum plantagineum excelsum. Leopard’s Bane |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Echinops humilis. Globe Thistle |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || Erigeron macranthus. Flea Bane |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Eryngium amethystinum. Sea Holly |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Eupatorium cœlestinum. Mist-Flower |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | --|-- | | | | | || Filipendula hexapetala. Meadow Sweet |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | | ---- | || Funkia Fortunei. Day Lily |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | | ---- | || lancifolia. Day Lily |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | |----| | || ovate. Day Lily |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | | ---- | || subcordata grandiflora. Day Lily |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | | | || variegata. Day Lily |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | --|-- | | | || Gaillardia grandiflora. Blanket Flower |
+----+-----+------+------+---+----+--------+------++----------------------------------------------------+

+====================================================++============================================++==================================================+
| || SEASON || HEIGHT |
| HARDY GARDEN PERENNIALS ||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| ||April|May|June|July|August|September|October||6 inches|1 foot|2 feet|3 feet|4 feet|5 feet|6 feet|
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Delphinium grandiflorum chinense., Larkspur || | | --|----|---- | | || | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Kelway’s Hybrids || | | --|-- | | ---- | ---- || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Dianthus barbatus. Sweet William || | --|-- | | | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| barbatus, Newport Pink || | --|-- | | | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| barbatus, Scarlet Beauty || | --|----|-- | | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| plumarius. June Pink, Clove Pink || | |----| | | | || --|-- | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| plumarius, Mrs. Sinkins || | |----|-- | | | || ---- |-- | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| plumarius, White Reserve || | |----|-- | | | || ---- |-- | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Dicentra eximia || | --|----|----|-- | | || --|-- | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| spectabilis. Bleeding-Heart || |---|-- | | | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Dictamnus Fraxinella. Gas Plant || | | --|----| | | || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Digitalis purpurea. Foxglove || | | --|----|-- | | || | | | --| ---- |-- | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| sibirica. Siberian Foxglove || | | --|----|-- | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Doronicum plantagineum excelsum. Leopard’s Bane || |---|-- | | | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Echinops humilis. Globe Thistle || | | | | ---- |-- | || | --| ---- |-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Erigeron macranthus. Flea Bane || | | | --| ---- | | || | ---- |-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Eryngium amethystinum. Sea Holly || | | | --| ---- | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Eupatorium cœlestinum. Mist-Flower || | | | | --| ---- | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Filipendula hexapetala. Meadow Sweet || | | --|-- | | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Funkia Fortunei. Day Lily || | | |----|-- | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| lancifolia. Day Lily || | | | | --|-- | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| ovate. Day Lily || | | --|-- | | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| subcordata grandiflora. Day Lily || | | | | ---- | ---- | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| variegata. Day Lily || | | --|----|-- | | || --|-- | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Gaillardia grandiflora. Blanket Flower || | | --|----| ---- | | || --|-- | | | | | |
+----------------------------------------------------++-----+---+----+----+------+---------+-------++--------+------+------+------+------+------+------+

COLOR, SEASON AND HEIGHT OF HARDY PERENNIALS--_Continued_

+--------------------------------------------------+----------------------------------------------------+
| COLOR | |
+----+------+------+------+---+----+--------+------+ HARDY GARDEN PERENNIALS |
|Pink| White|Yellow|Orange|Red|Blue|Lavender|Purple| |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| |------| | | | | | |Gypsophila paniculata. Baby’s Breath |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| |------| | | | | | | paniculata fl.-pl. Double-flowering Baby’s Breath |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | | | | |----| | | repens. Creeping Baby’s Breath |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | | |------|---| | | |Helenium autumnale. Sneezeweed |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | |------| | | | | |Helianthus moltis. Woolly Sunflower |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | |------| | | | | | orgyalis. Tall Sunflower |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | |------| | | | | | rigidus, Miss Mellish |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | |------| | | | | | Maximilianii. Late-flowering Sunflower |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | | |------| | | | |Hemerocallis Dumortieri. Dwarf Day Lily |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | |------| | | | | | flava. Yellow Day Lily |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | |------| | | | | | Florham. Giant Day Lily |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | | |------| | | | | fulva. Tawny Day Lily |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | | |------| | | | | fulva var. Kwanso. Double Orange Lily |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | | |------| | | | | fulva, Gold Dust |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | |------| | | | | | Thunbergii. Japanese Day Lily |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
|----| | | | | | | |Heuchera brizoides. Hybrid Coral Bells |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | | | |---| | | | sanguinea. Coral Bells |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
|----|------| | | | | | |Hibiscus militaris. Marsh Mallow |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
|----|------| | | | | | | Moscheutos, Mixed. Marsh Mallow |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | | | |---| | | | Moscheutos, Giant Red. Marsh Mallow |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| |------| | | | | | |Iberis sempervirens. Evergreen Candytuft |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | | | | | |--------| |Iris cristata. Dwarf Blue Iris |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | | | | |----| | | germanica. German Iris |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
|----|------| | | |----|--------|---- | Kaempferi. Japanese Iris |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+
| | |------|------|---| | | |Kniphofia Hybrids. Red-Hot-Poker Plant |
+----+------+------+------+---+----+--------+------+----------------------------------------------------+

+----------------------------------------------------+--------------------------------------------+--------------------------------------------------+
| | SEASON | HEIGHT |
+ HARDY GARDEN PERENNIALS |-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| |April|May|June|July|August|September|October|6 inches|1 foot|2 feet|3 feet|4 feet|5 feet|6 feet|
+----------------------------------------------------+--------------------------------------------+--------+------+------+------+------+------+------+
|Gypsophila paniculata. Baby’s Breath | | | --------| | | | | | ----|---- | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| paniculata fl.-pl. Double-flowering Baby’s Breath | | | ---|----| | | | | | ----|---- | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| repens. Creeping Baby’s Breath | | | | ---|------| | |--------| | | | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
|Helenium autumnale. Sneezeweed | | | | | ----|----- | | | | ----|---- | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
|Helianthus moltis. Woolly Sunflower | | | | |------|-- | | | | | | | --|---- |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| orgyalis. Tall Sunflower | | | | | ---|----- | | | | | | ---|------|-- |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| rigidus, Miss Mellish | | | | |------|-- | | | | | | ---|------|------|
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| Maximilianii. Late-flowering Sunflower | | | | | | ----|-------| | | | | | --|---- |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
|Hemerocallis Dumortieri. Dwarf Day Lily | | --|----| | | | | | ---|--- | | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| flava. Yellow Day Lily | | |----|-- | | | | | | ---|--- | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| Florham. Giant Day Lily | | | |----|-- | | | | ---|--- | | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| fulva. Tawny Day Lily | | | | |------|-- | | | | ---|--- | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| fulva var. Kwanso. Double Orange Lily | | | | |------|---- | | | | ---|--- | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| fulva, Gold Dust | | |----|-- | | | | |------| | | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| Thunbergii. Japanese Day Lily | | | ---|-- | | | | | --|-- | | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
|Heuchera brizoides. Hybrid Coral Bells | | | ---|-- | | | | | ---|--- | | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| sanguinea. Coral Bells | | | ---|-- | | | | | ---|--- | | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
|Hibiscus militaris. Marsh Mallow | | | | |------|----- | | | | --|------|--- | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| Moscheutos, Mixed. Marsh Mallow | | | | |------|----- | | | | | ---|------|--- | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| Moscheutos, Giant Red. Marsh Mallow | | | | |------|-- | | | | | ---|------|--- | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
|Iberis sempervirens. Evergreen Candytuft | |---|-- | | | | | ----|-- | | | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
|Iris cristata. Dwarf Blue Iris | | --|-- | | | | |--------| | | | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| germanica. German Iris | |---|--- | | | | | |------|------| | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
| Kaempferi. Japanese Iris | | | |----|-- | | | | ---|-- | | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+
|Kniphofia Hybrids. Red-Hot-Poker Plant | | | | ---|------| | | | | -----|---- | | | |
+----------------------------------------------------+-----+---+----+----+------+---------+-------+--------+------+------+------+------+------+------+

+=================================================++=============================================================+
| COLOR || |
+----+-----+------+------+---+----+--------+------|| HARDY GARDEN PERENNIALS |
|Pink|White|Yellow|Orange|Red|Blue|Lavender|Purple|| |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | |---| | | ---- || Lespedeza. Japanese Bush Clover |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | | | | | ---- || Liatris pycnostachya. Blazing Star |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | | | | | ---- || epicata. Gay Feather |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| |---- | | | | | | || Lilium candidum. Madonna Lily |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | --|-- | | | | || tigrinum splendens. Tiger Lily |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
|----|---- | | | |----| | || Lupinus polyphyllus. Lupine |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| |---- | | | | | | || Lychnis Flos-cuculi plenissima semperflorens. Campion |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | |---| | | || chalcedonica. Campion |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
|----| | | |---| | | || Haageana. Campion |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | |---|-- | | || viscaria. Campion |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
|----| | | | | | | || Lycoris squamigera. Fragrant Spider Lily |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | | | | | ---- || Megasea cordifolia. Saxifrage |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | | | | ---- | || Mentha piperita. Peppermint |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | |---| | | || Monarda didyma. Oswego Tea |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | | |----| | || Myosotis palustris semperflorens. Everblooming Forget-me-not|
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | ---- | | | | | || Œnothera fruticosa, Youngli. Evening Primrose |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | ---- | | | | | || Opuntia vulgaris. Prickly Pear |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| |---- | | | | | | || Pæonia, Couronne d’Or |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | |---| | | || Delachei |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
|----| | | | | | | || delicatissima |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | ----|-- | | | | | || Duchesse de Nemours |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| | | | |---| | | || Felix Crousse |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| |---- | | | | | | || festiva maxima |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| |---- | | | | | | || Mme. Crousse |
+----+-----+------+------+---+----+--------+------||-------------------------------------------------------------|
| |---- | | | | | | || Queen Victoria |
+----+-----+------+------+---+----+--------+------++-------------------------------------------------------------+

+=============================================================++============================================++==================================================+
| || SEASON || HEIGHT |
| HARDY GARDEN PERENNIALS ||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| ||April|May|June|July|August|September|October||6 inches|1 foot|2 feet|3 feet|4 feet|5 feet|6 feet|
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Lespedeza. Japanese Bush Clover || | | | | --|-- | || | | | --|-- | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Liatris pycnostachya. Blazing Star || | | | --| ---- |-- | || | | | | ----|-- | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| epicata. Gay Feather || | | | --| ---- |-- | || | | | | ----|-- | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Lilium candidum. Madonna Lily || | |----| | | | || | | | ---- | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| tigrinum splendens. Tiger Lily || | | | | ---- |-- | || | | | ---- | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Lupinus polyphyllus. Lupine || | | --|-- | | | || | | ---- | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Lychnis Flos-cuculi plenissima semperflorens. Campion || | --|----| | | | || ---- | | | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| chalcedonica. Campion || | | |----|-- | | || | | ---- | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Haageana. Campion || | | |----|-- | | || | ---- | | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| viscaria. Campion || | --|-- | | | | || --|-- | | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Lycoris squamigera. Fragrant Spider Lily || | | |----|-- | | || | ---- | | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Megasea cordifolia. Saxifrage || | --|----| | | | || | --|-- | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Mentha piperita. Peppermint || | | | | | | || | --|-- | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Monarda didyma. Oswego Tea || | |----|-- | | | || | | | ---- | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Myosotis palustris semperflorens. Everblooming Forget-me-not|| |---|-- | | | | || ---- | | | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Œnothera fruticosa, Youngli. Evening Primrose || | | --|----|-- | | || | --|-- | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Opuntia vulgaris. Prickly Pear || | | | | ---- | | || ---- | | | | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Pæonia, Couronne d’Or || | --|-- | | | | || | | | ---- | | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Delachei || | --|-- | | | | || | | | ---- |-- | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| delicatissima || | --|-- | | | | || | | | ---- |-- | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Duchesse de Nemours || | --|-- | | | | || | | | ---- |-- | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Felix Crousse || | --|-- | | | | || | | | ---- |-- | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| festiva maxima || | --|-- | | | | || | | | ---- |-- | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Mme. Crousse || | --|-- | | | | || | | | ---- |-- | | |
|-------------------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Queen Victoria || | --|-- | | | | || | | | --|-- | | |
+-------------------------------------------------------------++-----+---+----+----+------+---------+-------++--------+------+------+------+------+------+------+

+=================================================++====================================================+
| COLOR || |
+----+-----+------+------+---+----+--------+------|| HARDY GARDEN PERENNIALS |
|Pink|White|Yellow|Orange|Red|Blue|Lavender|Purple|| |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || Pæonia, Richardsen’s Dorchester |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | |---| | | || rubra superba |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----|---- | | | | | | || sinensis, Mixed |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || Triomphe de l’Exposition de Lille |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | ---- | ---- | | | | || Papaver nudicaule. Iceland Poppy |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | |---| | | || orientale. Oriental Poppy |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Paradisea Lillestrum. St. Bruno’s Lily |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | |---| | | || Penstemon barbatus Terreyi. Scarlet Beardtongue |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Polygonatum giganteum. Solomon’s Seal |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | |---| | | || Phlox paniculata, Baron Van Dedem |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | | | ---- || paniculata, B. Comte |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| --|-- | | | | | | || paniculata, Beranger |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || paniculata, F. G. von Laseburg |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || paniculata, Independence |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || paniculata, Rheinlander |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | | | ---- || paniculata, Von Hochberg |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || suffruticosa, Miss Lingard |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || subulata alba, Moss Pink |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | | ---- | || subulata lilacina |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || subulata rosea |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | --|-- | | | || Physalis Franchetii. Chinese Lantern Plant |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| --|---- | | | | | | || Physostegia virginica. False Dragonhead |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || virginica alba. False Dragonhead |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | |----| | || Platycodon grandiflora. Balloon-Flower |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----|---- | ---- | |---| | | || Primula veris. English Primrose |
+----+-----+------+------+---+----+--------+------++----------------------------------------------------+

+====================================================++============================================++==================================================+
| || SEASON || HEIGHT |
| HARDY GARDEN PERENNIALS ||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| ||April|May|June|July|August|September|October||6 inches|1 foot|2 feet|3 feet|4 feet|5 feet|6 feet|
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Pæonia, Richardsen’s Dorchester || | |----| | | | || | | | --|-- | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| rubra superba || | |----| | | | || | | | ---- |-- | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| sinensis, Mixed || | --|-- | | | | || | | | ---- |-- | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Triomphe de l’Exposition de Lille || | --|-- | | | | || | | | ---- |-- | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Papaver nudicaule. Iceland Poppy || | --|----|----| | | || --|-- | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| orientale. Oriental Poppy || | |----| | | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Paradisea Lillestrum. St. Bruno’s Lily || | | --|-- | | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Penstemon barbatus Terreyi. Scarlet Beardtongue || | | --|-- | | | || | | | ---- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Polygonatum giganteum. Solomon’s Seal || |---| | | | | || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Phlox paniculata, Baron Van Dedem || | | | --| ---- | ---- |-- || | | | ---- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| paniculata, B. Comte || | | | --| ---- |-- | || | | | ---- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| paniculata, Beranger || | | | --| ---- |-- | || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| paniculata, F. G. von Laseburg || | | | --| ---- | ---- | || | | | ---- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| paniculata, Independence || | | |----| ---- | ---- | || | | | --| ---- | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| paniculata, Rheinlander || | | |----| ---- |-- | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| paniculata, Von Hochberg || | | | --| ---- | ---- | || | | | ---- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| suffruticosa, Miss Lingard || | | --|----| ---- | ---- | || | | | --|-- | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| subulata alba, Moss Pink || --|---| | | | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| subulata lilacina || --|---| | | | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| subulata rosea || --|---| | | | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Physalis Franchetii. Chinese Lantern Plant || | | | | --| ---- |-- || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Physostegia virginica. False Dragonhead || | | --|----| | | || | | | | --|-- | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| virginica alba. False Dragonhead || | | --|----| | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Platycodon grandiflora. Balloon-Flower || | | --|----| | | || | | | ---- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Primula veris. English Primrose || --|---| | | | | || ---- |-- | | | | | |
+----------------------------------------------------++-----+---+----+----+------+---------+-------++--------+------+------+------+------+------+------+

+=================================================++====================================================+
| COLOR || |
+----+-----+------+------+---+----+--------+------|| HARDY GARDEN PERENNIALS |
|Pink|White|Yellow|Orange|Red|Blue|Lavender|Purple|| |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----|---- | | |---| | | || Pyrethrum roseum |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || Ranunculus acris fl.-pl. Double-flowered Buttercup |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || Rudbeckia laciniata. Golden Glow |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | | | ---- || purpurea. Giant Purple Coneflower |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Sagina subulata. Pearlwort |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | --|-- | || Salvia azurea grandiflora. Meadow Sage |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----|-- | || pratensis. Meadow sage |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || Sedum acre. Stonecrop |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || spectabile. Stonecrop |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || Silphium perfoliatum. Cup plant |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
|----| | | | | | | || Spiræa (Astilbe) Arendsii, Ceres |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | | | ---- | || Statice latifolia. Great Sea Lavender |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Stokesia cyanea. Cornflower |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || cyanea alba. White Cornflower |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Tradescantia virginica. Spiderwort |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || virginica alba. Spiderwort |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | ---- | | | | | || Trollius europæus. Globeflower |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| --|-- | | | | | | || Valeriana officinalis. Garden Heliotrope |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Veronica longifolia subsessilis. Blue-Jay Flower |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || amethystina. Speedwell |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || longifolia. Japanese Speedwell |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Viola cornuta alba. Tufted Pansy |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || cornuta, G. Wermig. Tufted Pansy |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| | | | | |----| | || Violet, Double Russian |
+----+-----+------+------+---+----+--------+------||----------------------------------------------------|
| |---- | | | | | | || Yucca filamentosa. Spanish Bayonet |
+----+-----+------+------+---+----+--------+------++----------------------------------------------------+

+====================================================++============================================++==================================================+
| || SEASON || HEIGHT |
| HARDY GARDEN PERENNIALS ||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| ||April|May|June|July|August|September|October||6 inches|1 foot|2 feet|3 feet|4 feet|5 feet|6 feet|
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Pyrethrum roseum || | --|----| | | | || | | | ---- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Ranunculus acris fl.-pl. Double-flowered Buttercup || | --|-- | | | | || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Rudbeckia laciniata. Golden Glow || | | | | ---- |-- | || | | | | | | ---- |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| purpurea. Giant Purple Coneflower || | | | --|-- | | || | | | | | ---- | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Sagina subulata. Pearlwort || | | --|-- | | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Salvia azurea grandiflora. Meadow Sage || | | | | ---- |-- | || | | | | ---- | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| pratensis. Meadow sage || |---|-- | | | | || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Sedum acre. Stonecrop || | | --|-- | | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| spectabile. Stonecrop || | | | | ---- |-- | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Silphium perfoliatum. Cup plant || | | | | ---- |-- | || | | | | | | ---- |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Spiræa (Astilbe) Arendsii, Ceres || | | --|-- | | | || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Statice latifolia. Great Sea Lavender || | | | --| ---- | | || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Stokesia cyanea. Cornflower || | | |----| ---- |-- | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| cyanea alba. White Cornflower || | | |----| ---- |-- | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Tradescantia virginica. Spiderwort || | --|----| | | | || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| virginica alba. Spiderwort || | --|----| | | | || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Trollius europæus. Globeflower || --|---|-- | | | | || | --|-- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Valeriana officinalis. Garden Heliotrope || | |----|----| | | || | | | | | ---- | ---- |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Veronica longifolia subsessilis. Blue-Jay Flower || | | | | ---- | ---- |-- || | | --|-- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| amethystina. Speedwell || | |----|-- | | | || | | ---- | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| longifolia. Japanese Speedwell || | |----|----| | | || | | | ---- | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Viola cornuta alba. Tufted Pansy || |---|----|----|-- | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| cornuta, G. Wermig. Tufted Pansy || | --|----|----|-- | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Violet, Double Russian || |---|-- | | | | || ---- | | | | | | |
|----------------------------------------------------||-----+---+----+----+------+---------+-------||--------+------+------+------+------+------+------|
| Yucca filamentosa. Spanish Bayonet || | | |----|-- | | || | | | --| ---- | | |
+----------------------------------------------------++-----+---+----+----+------+---------+-------++--------+------+------+------+------+------+------+

ANNUALS

For those who prefer growing flowers merely to pick, the quickest way of
getting them is to plant summer-blooming annuals. A list of thirty
popular annuals, all of them easily grown, is given below.

BLOOMING IN JULY

Lavatera _Lavatera trimestris_
Clarkia _Clarkia elegans_
Large-flowered Godetia _Œnothera Whitneyi_
Early Cosmos _Cosmos bipinnatus_
Sweet Alyssum _Alyssum maritimum_
Marigold _Tagetes patula_
Nicotiana _Nicotiana alata_
Sander’s Nicotiana _Nicotiana Sanderæ_
Arctotis _Arctotis grandis_
Stock, gillyflower _Matthiola incana_ var. _annua_
Annual larkspur _Delphinium Ajacis_
Bedding Lobelia _Lobelia Erinus_
Wishbone flower _Torenia Fournieri_
Phacelia _Phacelia congesta_
African marigold _Tagetes erecta_
California poppy _Eschscholtzia californica_
Giant tulip _Hunnemannia fumariæfolia_
Annual Gaillardia _Gaillardia pulchella_
Scarlet sage _Salvia splendens_
Youth-and-old-age _Zinnia elegans_
Rose moss _Portulaca grandiflora_
Balsam _Impatiens balsamina_
Painted tongue _Salpiglossis sinuata_

BLOOMING IN AUGUST

Gilia _Gilia capitata_
Three-colored chrysanthemum _Chrysanthemum carinatum_
Mourning bride _Scabiosa atropurpurea_
China asters _Callistephus chinensis_
Everlasting _Helichrysum bracteatum_
Didiscus _Trachymene cœrulea_

CHAPTER VII

HISTORY OF THE PLANT KINGDOM

1. DAWN OF PLANT LIFE ON EARTH

“And the Earth was without form and void”

The quotation from the second sentence of the first chapter of Genesis
tells us more in eight words than could very well be said in as many
chapters. Not only have we biblical authority for this early absence of
life on the earth, but all the accumulated knowledge of the ages points
in the same direction. We have already seen that plants, because they
can take inorganic substances from the earth and air and transform them
into organic food, must in all probability have come on the earth before
animals which, directly or indirectly, all rely upon plants for their
food. Even those animals that eat only flesh devour other animals which
depend upon plants for food. It may safely be repeated, then, that upon
plants all animal life depends, and that, in the dim beginnings of
things on the earth, it must have been some form of plants that were the
first living things. Extremely simple unicellular animals, however, are
known to date from early times.

In the volume devoted to that subject in this series, you will find that
at the very earliest stages of what we know as our globe there was a
segregation of land and water somewhat different from our great oceans
and continents to-day in extent and area, but differing mostly in
this--that much of the water was fresh and very nearly boiling hot. We
have still the remnants of those great reservoirs of hot water, as our
hot springs and shooting geysers only too well prove. And if all plants
were as quickly killed by hot or boiling water as the common garden
geranium, we should not expect any plant life to have developed upon the
earth until all those great bodies of water had cooled. To have waited
for that would have been to delay the appearance of plants for no one
knows how many millions of years, and there is some fairly good evidence
that long before normal conditions of heat and cold were established
there already flourished certain kinds of plants. What those plants were
is something of a speculation, and indeed exactly what they were no one
knows. But in our present hot springs grow certain plants, microscopic
in size, but quite obviously related to the algæ or to certain
bacterialike organisms. They live with apparent comfort and reproduce
themselves freely in water so hot that no other form of life will
maintain itself. While there is no proof that these present plant
inhabitants of hot springs, common in the West, are descended from
infinitely ancient progenitors, it is a fair assumption that some
organism capable of growing in warm or hot water was the first living
thing to appear in a world otherwise “without form and void.”

This great question of how plants came on the earth, and particularly
how from these apparently simplest organisms our whole wonderful
vegetation has arisen, has always been one of the most interesting
things in the history of the world. There are many different ways of
studying this, and in the very earliest stages of plant development we
are forced to reason, not so much by actual records or buried skeletons
of the plants that probably existed then, for only a very few have ever
been found, but by our knowledge of the physical and chemical
requirements of unicellular plants, and those slightly more developed,
and of their individual life histories. It is, for instance, certain
that the first plants must have been aquatic, as no real land plants are
known for hundreds of thousands of years after the earth was quite
capable of maintaining plant life. The absolute necessity of water to
complete fertilization in nearly all cryptogams also makes it fairly
certain that water plants, and these of the simplest nonflowering type,
were the first living things to be found on the earth. And it is more
than a fair inference that these were inhabitants of warm or hot water.
Subsequently, as the water cooled, they may well have been not unlike
the green scum found on ponds to-day.

Of course, the actual origin of life itself is still as much of a riddle
as it was when the ancient philosophers began to speculate about it
years before the Christian era. Protoplasm, the unit or basis of all
life, while its composition and growth requirements are fairly well
known, has never been made in any laboratory. Nor have scientists ever
been able to decide what the combination of physical and chemical forces
must have been to originate it. But that from a perfectly sterile,
probably steaming hot globe, there did finally develop some form of
life, and that this must have been aquatic plant rather than animal
life, seems not only certain, but the only hypothesis upon which all
subsequent development of life must have been based. It is not necessary
to ascribe the origin of life to providential inspiration nor to the
meddling of strange and outlandish deities, as all savage tribes did and
some more civilized peoples still do. There can, however, be no escaping
the fact that life is more than the combination of physical and chemical
conditions which sustain it, and that its origin has never, and may
never be “explained” by merely describing the conditions which
unquestionably favored its appearance. In other words, the origin of
plant life throws us back upon things believed but incapable of proof,
and is none the less wonderful because we cannot yet understand the
probable progression of forces and materials to which it owes its
origin.

Assuming, then, and we must all start with this proposition, that
aquatic plants certainly, and warm or hot water plants probably, were
the first living things upon the earth, what are the next steps in the
history of the plant kingdom? The answer to that question involves a few
simple facts in geology and, particularly, in the making of fossils,
which must be understood before we can see those steps or their
significance. The geological changes which have resulted in the present
condition of the earth’s surface are described in the volume devoted to
that subject, and will not be repeated here. But some mention must be
made of the formation of fossil plants, particularly as it is upon the
evidence of these that the story of the development of plant life is
literally written in the rocks.

If a leaf or twig drops into shallow water with a clay or mud bottom, it
ultimately sinks, and if then a film of clay or silt is brought down by
freshets or what not, it will bury the leaf or twig, of course, filling
in every slight depression. If then the buried object were raised so
that it dried out and could be split open, we should find a perfect
impression of the veins and other outward characters of the leaf etched
in the clay. This is often such a perfect process that every detail of
the leaf is left in the mud impression, and only the opportunity for
this impression to become hardened into rock is needed for us to have a
fossil. For these are merely the final hardened rock stages of a process
that began as we have indicated, and the thousands of fossils that have
been dug out of the earth prove how common the conditions for their
formation must have been in certain periods of the world’s history.

But of the untold millions of fossils that have been made most have been
destroyed, for the geologists tell us that the earth’s crust has been
subjected to much upheaval. Mountain chains thrown up, inland seas
formed, great river systems carved out, and tremendous periods of
vulcanism or fire action have made the earth’s crust, at different
periods, a mighty restless place. And these changes, so slow that often
millions of years have elapsed before they were completed, have
sometimes been favorable to the making of fossils and sometimes to their
destruction. Darwin once wrote about the fossil record that he saw it
“as a history of the world imperfectly kept, and written in a changing
dialect; of this history we possess the last volume alone relating only
to two or three countries. Of this volume, only here and there a short
chapter has been preserved; and of each page, only here and there a few
lines. Each word of the slowly changing language, more or less different
in the successive chapters, may represent the forms of life, which are
entombed in our consecutive formations, and which falsely appear to have
been abruptly introduced.” And yet it is upon the evidence of this
fossil record that most of our knowledge of the history of the plant
kingdom is based.

The difficulty of getting any true picture of the beginnings of plant
life is great, for those earliest stages of development were
unquestionably water-inhabiting plants, whose tissue is mostly too soft
and too easily decayed to make fossil impressions of them likely to be
preserved. Yet fossil algæ have been found in rock strata so old that no
fern or flowering plant had yet made its appearance. It is not too much
to picture the world then as peopled only by cryptogamous plants of
simple structure, living in the water, and land plants which to-day make
up the bulk of our vegetation as not yet developed. Furthermore, there
is in these earliest stages no trace of plants with any kind of a
vascular system, such as all ferns and flowering plants possess. No
stretch of our imagination can readily picture the earth as it in all
probability was in that period, with no trees or vines or flowers, the
land wholly bare of vegetation, and in the water, along its sterile
shores, only unicellular or slightly more developed, wholly nonflowering
plants. The conditions supporting such plant life existed for many
millions of years, and some geologists have claimed that this period of
time exceeded all the subsequent ones combined, so that algæ and some
other unicellular plant types are the oldest in the world; and they
still exist in enormous numbers.

Much later than this, fossil algæ of comparatively complex structure
have been found, showing by their frequency and more highly developed
characters a more advanced stage in the development of the plant
kingdom. So common were these various types of what we now call
seaweeds, although most of them apparently lived in fresh water, and so
widespread was their occurrence, that this Pre-Cambrian period has often
been called the reign of algæ. As yet no other plants had been developed
and none of these ancient types had invaded the land, which for millions
of years more must have been entirely without vegetation.

2. THE DEVELOPMENT OF LAND PLANTS

After the reign of algæ and other cryptogamous water plants, our
knowledge of which is so unsatisfactory because of the incompleteness of
the fossil record, there appeared the first evidences of plants that
were able to live with “one foot on the land and the other in the
water,” so to speak. How many transitional stages there may have been,
and what relation any of these may bear to existing plants, is not
known, or is, at any rate, so little understood that it is a disputed
point. But somewhere about this period there did appear plants capable
of living at least part of their life on the land, and possessing in
their vascular system a structure of enormous advantage over their
predecessors. It is pure speculation as to what this first land plant
was derived from, or from what particular group of water-inhabiting
plants it took some of its characteristics. Its appearance, in any case,
was a dramatic event of the first importance. Not the least interesting
feature of it is that the very plants of which we have indisputable
evidences of being the first land plants have come down through the ages
to the present day. For it is practically impossible to separate our
modern representative from its ancient ancestor, despite all the
tremendous changes that have been going on both in the history of the
earth’s crust and in the vicissitudes of the vegetation in meeting those
changes.

There is the best of evidence that these first land plants were of the
club moss family, which are relatives of the ferns. One of them,
representing our present _Lycopodium Selago_ (Figure 107) so closely as
to be practically indistinguishable, is a common type, as revealed to us
in the fossil record. The present plant inhabits rich, moist, and mostly
evergreen woods in the northern part of the globe, and is common in the
Adirondack and White Mountains.

[Illustration: FIG. 107.--CLUB MOSS

(_Lycopodium Selago_)

A club moss which has come down through the ages almost unchanged from
the days when coal was being formed. Grows to-day in the north temperate
zone, particularly in mountains.]

Nor was the earth peopled wholly by this ancestor of _Lycopodium
Selago_, for we find at this time, or just after it, a great development
of plants of this type. Some of these were giant, treelike club-mosses
that have been so well preserved as fossils that even their internal
structure and spore-bearing characters are well known. Many other
strange relatives of our modern club mosses flourished in those days,
some of which have wholly disappeared, as have all the treelike forms.
These highly organized club mosses, quite unlike any modern
representative of the family, appear to have been crowded off the earth
by other and subsequent types of vegetation, while _Lycopodium Selago_,
and about thirty related species, have persisted to the present day; not
precisely in all cases as they were in this dawn of a land flora, but in
many cases with modern structure and reproductive processes so close to
the ancestral types as to be nearly identical.

Perhaps nothing gives one a better impression of the tremendous time
that must have elapsed before the appearance of these ancient club
mosses than the very slight modifications from their ancient condition
which their structure at the present time exhibits. While nothing is
certainly known of their origin, when they first appeared they were
plants with a well-developed vascular system, having stems and leaves
quite unlike any of their predecessors’, and a reproductive process
almost precisely like their modern descendants. In other words, if they
have changed so slightly in all the millions of years since our
rock-written records of them first occur, what an infinitely greater
period must have elapsed down the dim vista of the ages before their
appearance. Of this period, with the exception of fossil algæ, we know
practically nothing, and, worst of all, the actual transition from a
wholly water-inhabiting flora to these certainly land-inhabiting club
mosses may never be known. For, added to the difficulty of water plants
being preserved as fossils, already mentioned, is the fact that as they
are the oldest, they are found in the deepest strata and, consequently,
the hardest to find; and due to changes in the earth’s crust, these
ancient fossil-bearing strata have often been much disturbed.

The conclusion appears to be indicated that the origin of a land flora
came about with the appearance of these ancient club mosses, which are
not mosses in our present-day interpretation of those plants, and that
at about the same period many other plants also were found, the whole
vegetation resembling nothing that exists at the present time, but many
of the different kinds of this ancient flora showed unmistakable
evidence of being the progenitors of many plants that exist to-day. What
these were, and particularly what they accomplished, both in the history
of the plant kingdom and in making the world habitable for man who did
not come for millions of years after they were preparing the way, will
be considered in

3. CARBONIFEROUS PLANTS AND THE FORMATION OF COAL

The carboniferous time, or the period when the earth was covered with
huge forests of strange shrubs and trees, most of which were unlike
their modern successors, apparently had a climate so nearly uniform and
seasonless that fossil remains of these plants have been found
throughout the world. Even in the Arctic the rock strata show the
flourishing of forests that must have needed a climate very different
from the frigid condition there to-day, and furnishing indisputable
evidence of a warm, most probably frostless, climate practically
throughout the world.

[Illustration: FIG. 108.--HORSETAIL

(_Equisetum hyemale_)

A modern horsetail or scouring rush, common in the north temperate zone.
Ancestors of these formed huge forests at the time that coal was being
formed.]

The giant club mosses have already been mentioned, with their
persistence to the present day in much reduced number, and vastly
reduced sizes. No one can picture the grandeur of those ancient forests,
peopled with queer animals long since extinct and with dragon flies
known to have a wing-spread of two feet or more. But with the club
mosses were giant horsetails, which in somewhat changed form have also
come down to our times, but in much reduced stature and frequently are
familiar enough as weedy plants along railway embankments, and
sometimes in more natural environments. Most of our modern
representatives of the genus _Equisetum_ (Figure 108), or horsetails,
are low herbs, but one South American kind still retains the ancient
habit of growing to considerable heights, as specimens up to twenty feet
high are known. Related to the ancient treelike horsetails were queer
vines with slender twining stems, which, judging from their fossil
remains, must have been very common. Both the ancestors of our club
mosses and the horsetails must have occupied vast swampy areas, as their
stem structure indicates a fondness for water, to which, as we have
already seen, their still more ancient ancestors were always confined.

Vigorously competing with these plants for occupancy of those great
swamps were vast quantities of plants that have been called cycadlike
ferns from their likeness to ferns on the one hand and plants like the
so-called sago palm on the other. The sago palm, or _Cycas revoluta_, is
a modern representative of these ancient forms, and retains the
remarkable characteristic of having its male fertilizing cell capable of
movement as we know to be the case in nearly all cryptogamous plants.
Yet _Cycas_, with its related genera, which are found in nearly all the
warmer parts of the earth to-day, are true flowering plants which bear
cones. We see, therefore, in these old cycadlike ferns one of the first,
almost experimental, evidences of the seed habit, and consequently the
breaking away from the spore habit which overwhelmingly characterized
the reproductive processes of its ancient associates.

The inhabitants of higher parts of that dim, mysterious world, of which
we know only that part revealed in the fossil record, were largely
ancestors of our modern cone-bearing evergreens. They are known as
_Cordaitales_ and have long since disappeared. Forming forests of huge
size and making long, slender trunks with a crown of leaves at the top
not unlike some modern conifers to which they are, of course, related,
these progenitors of our pines and spruces must have been striking
objects of that strange landscape. Rooted stumps of these ancient trees
have been uncovered, and their narrow leaves, often three feet long, are
common as fossils. By some our present conifers and the _Cordaitales_
are both thought to be descendants from a still more ancient group, of
which the existence is only conjectured.

We can, perhaps, best summarize our sketch of the plant life existing at
the close of this period by saying that all the forms show unmistakable
evidence of being crytogamous so far as their reproductive processes are
concerned, or else, as in the progenitors of our conifers and cycads,
the beginnings of a definite seed habit are indicated. Most of the
lowland representatives of this flora were cryptogamous in their
characters and ancestry, while some of them, and nearly all the flora of
drier sites, appear to have shown the beginnings of flower production.
Some of these flowers, which are always cones, are unmistakable as such,
and pollen in tremendous quantities has been found among their buried
remains. These cones belong to trees that are actual gymnosperms or
obvious ancestors of them, for no herbs are known as yet. Nor are
angiospermous flowering plants known from this period, nor have any ever
been found in strata millions of years younger than the fossil-bearing
strata of this age of the ancestors of our modern ferns, conifers, or
cycads.

Nor must we picture the development of these different plant inhabitants
of that time as passing from one to another in orderly sequence, for
that would give us the impression of a regular progression from simple
to complex, which may or may not be the truth. There appears to be such
a sequence, and the internal structure of the remains of many of these
ancient types of plant life have greatly aided our ability to understand
their relationships. But with the possibility of various reproductive
processes or other structures appearing in quite unrelated forms, and
with the comparative paucity of the fossil record in mind, no one can
say for certain what are the true lines of descent. The necessity for
water in the reproductive act of nearly all the crytogams, the origin of
the vascular structure, and the consequent ability to live upon the
land, and finally the production of a conelike flower structure with
pollen, and all that that implies, are all found during this period.

To the vegetation inhabiting the swamps during this period, man owes a
debt perhaps as great as to our modern food plants, for it is upon this,
and some later plant remains, that we rely for coal. This period has
been well called the Carboniferous, for its chief claim to attention,
outside the realms of botanical research, was the deposition of those
great collections of plant remains, which, as coal, contain as high as
90 per cent of carbon and furnish the fuel of the world. This is
scarcely the place or time to go into the composition of different kinds
of coal, but some mention of the conditions under which these ancient
swampy forests were transformed into that valuable substance may well
conclude the account of a vegetation period the history of which has in
large part been found written in the very strata from which coal itself
is derived.

In the lowest and wettest parts of those forests there occurred, just as
there may occur to-day, a large accumulation of fallen trees and other
vegetable refuse. In the ordinary way these would simply rot, due to the
work of insects and the fungi of decay, and in a few score years there
would be nothing to show. “Dust to dust” would be, and is, the history
of so many living things that it is only some machinery for arresting
this process which will give us very different results. In the case of
coal formation the original impetus appears to be certain microscopic
organisms, probably saprophytic fungi, fossil remains of which have been
identified, which work upon the fallen mass of vegetation and start its
decay, but which can only do so while their prey is still within the
influence of the air. The initial stages of decay must, therefore, have
been going on while the water was low enough for these organisms to
work. But in many parts of that ancient landscape the water level was a
fluctuating quantity, due to local conditions or to changes in the
earth’s crust. So that many times partially decomposed vegetation masses
would become submerged, stopping the work of these organisms of decay
that demand air, but providing the only conditions under which certain
others could complete the transformation. These bacterial organisms that
will work only when deprived of air continue the process, but in a
different way. For one thing, the lack of air delays decomposition or
almost stops it, as witness the resistance of logs under water, some of
which are known to be hundreds of years old. And forest stumps off the
coast of Cape May, in New Jersey, are in nearly as perfect a state as
when first submerged, over 40,000 years ago. In the production of coal
these anærobic (living without air) bacteria release oxygen and hydrogen
from the partly decayed mass, leaving as a residue a substance known as
peat, which is largely carbon. The transformation of peat into coal
depends upon requisite pressure of the strata that may be laid down on
top of the peat bed, and probably upon chemical changes that go on after
such covering strata have been laid down.

The fact that coal is sometimes found only in thin veins, with layers of
shale and other material between, tells us that its origin must often
have been a precarious affair, where alternate emergence and submergence
would permit first the vegetation to develop and then its transformation
to peat, followed by the deposition of fine sands or silt covering the
bed. Several such cycles occurred, sometimes separated by untold ages of
time, or again by much briefer periods. Certain mines, however, contain
over 200 feet of solid coal. The length of time necessary for such a
vast accumulation, or how many generations of these ancient plants went
into their making, is beyond calculation. With the mining of coal
running into the hundreds of millions of tons yearly, we get some idea
of how great were those Carboniferous forests, and how extensive they
were is proved from the widely separated localities in which coal mines
are found.

The Carboniferous age of fern, cycad, and conifer ancestors was by no
means a quiet, orderly period, as from geological evidence it appears to
have been much subject to alternate emergence and submergence of great
tracts of land. Compared with what followed, it actually was a period of
comparative quietness, however, and it must, in at least most parts of
the world, have permitted the slow development of certain of its plant
groups to a state of perfection never reached since. This is
particularly true of the ancient relatives of our club mosses and
horsetails.

Perhaps one of the most obvious questions to ask about these plants is
how long ago they lived, and upon the answer to such a question depend
many others. What, for instance, is the position of the Carboniferous as
compared to what preceded it and came after? How old is the earth and
when did life first appear on it? The evidence upon which such questions
are answered comes from the estimates of physicists as to the age of the
earth; from students of fossil animals and plants; from astronomers,
from geologists and other students. A compromise of these different
estimates, and one that has consequently been widely accepted, gives the
age of the earth, dating from the time of its having a definite crust
with land and water masses, as somewhere near a hundred million years.
Such figures are beyond our comprehension and consequently mean almost
nothing, but the proportion in time of the different stages of the
development of plants may be stated with greater certainty. Taking the
total age of the earth as 100 per cent, the period when there is no
record of life of any sort may be set down as about 45 per cent of the
total, the reign of algæ and development of land plants about 8 per
cent, the carboniferous or coal-forming plants about 28 per cent, which
leaves only 19 per cent from that distant time to the present. And many
things happened in this comparatively brief fifth of the plant world’s
history, among them the origin of some plants that have come straight
down to us, without discoverable change.

[Illustration: FIG. 109.--GINKGO OR MAIDENHAIR TREE

(_Ginkgo biloba_)

Found in most fossil strata and in a practically unchanged condition
from the upper part of the Carboniferous to the most recent fossil
records. Now unknown as a wild tree and preserved for us through its
cultivation in ancient temple gardens in eastern Asia.]

We could hardly leave the Carboniferous time without at least brief
mention of the ginkgo tree (Figure 109), or, as some call it, the
maidenhair tree. From the upper strata of the Carboniferous it is
common, as it is in practically all subsequent fossil accumulations down
to the most recent. And yet the tree has never been found wild, although
its frequency in temple gardens in China and Japan, always as a
cultivated tree, suggests that its disappearance as a wild plant must
have come since the priests began preserving it, which can be only a
matter of a few thousand years at most. In other words, we have just
missed seeing in the ginkgo what has so many times happened to these
very ancient types of vegetation, namely, their final extinction. This
must have occurred within historic times, and, judging by its frequent
use as a temple tree in eastern Asia, that region was its last outpost
after its long journey from the dim past. Thousands of other ancient
plants have completely disappeared, and one cycad from New South Wales
is at this moment putting up a losing fight against modern competitors,
but in the ginkgo tree the actual twilight and extinction of its wild
existence has missed observations by modern plant geographers by only a
brief period. It is almost as though we had waited all our life to see
some great event and then missed it by a few moments. Fortunately the
tree is now common in cultivation, and not the least interesting feature
of it is the fact that its male fertilizing cell retains its power of
movement, which dates back to its early associates. Among modern
flowering plants only the ginkgo and the relatives of the sago palm or
cycads retain this relic of an overwhelmingly cryptogamous ancestry.

The end of the Carboniferous or coal-forming ages was marked by great
changes in the earth’s surface, some of them cataclysmic in their
effects. What they were in detail is described in the volume on geology
and need not be repeated here. What happened to the development of the
plant kingdom after this will be considered in the next section of this
chapter.

4. MORE RECENT ANCESTORS OF OUR MODERN FLORA

The vegetation at the ending of Carboniferous times was much affected by
the great changes in the earth’s surface which happened then. The
thrusting up of great mountain chains, the slow encroachment of
continental glaciers, and the other phenomena characterizing that period
could not but be reflected in the plant population. For one thing the
giant club mosses and horsetails were much reduced in extent and finally
disappeared, leaving only the immediate ancestors of our present-day
forms. _Cordaitales_ gave place to trees not unlike some of the modern
yew trees. True ferns as well as the cycadlike ferns with seeds appear
to have lived side by side with true cycads, which subsequently
supplanted their obvious cycadlike fern ancestors. There was an obvious
dwindling of ancient Carboniferous forms, some of which, however,
persisted in considerable numbers. Many other plants existed then, some
of which died out there, and some of which still survive in descendants,
particularly among our conifers and ferns. But there happened toward the
upper end of this period an event in the history of the plant kingdom so
dramatic, of such far-reaching results, that its appearance might be
likened to the overthrow of the Czar in Russian history or to the
downfall of the Kaiser in Germany. For with it dawned a new era for the
plant world, the effects of which we see all about us to-day.

Somewhere in the rock strata of this period we find the first
angiosperm, or plant that matures its seed in a closed ovary, and with
the origin of that habit there began such a development of plants of
this type that its impetus has not yet been lost. It is impossible to
tell at this distance from the origin of that first angiosperm from what
it developed, nor how many ages it may have existed before the accident
of its preservation as a fossil revealed its presence. It is certainly
not without significance that it bore conelike fruits, such as all its
associates and predecessors among flowering plants had done, but its
possession of large, showy petals is the first evidence of a flower
characteristic that was destined to make our present vegetation the
lovely thing it is. This exceedingly interesting plant was a _Magnolia_
(Figure 110), or so like our present plants of that genus as to be their
obvious ancestor. Somewhere here, too, must have arisen the insect
fertilization of flowers which we have seen to be such an important part
of flower economy at the present time. Most of this ancient magnolia’s
associates must have relied on wind pollination for seed production, as
many modern plants still do, but the origin of insect fertilization
appears to have come with the appearance of the first really
petaliferous flower.

[Illustration: FIG. 110.--COMMON LAUREL MAGNOLIA

(_Magnolia virginiana_)

The fossil record tells us that probably the first flowering plant was
some ancestor of magnolia.]

With this _Magnolia_ were found other flowering plants which soon
increased tremendously in numbers of individuals and differences of
structure, such as our sassafras, the tulip tree, the poplar tree, and
some others. All of these are trees or shrubs and we do not yet know
whether herbs grew in the strange surroundings of that ancient forest or
not. Their soft tissue may have prevented their preservation as fossils,
but, at any rate, no herb has left its rock-written record from as early
in this period as the trees and shrubs. All of these ancient trees have
been recorded only in the northern hemisphere and it may be true that
this part of the earth was the cradle of all those hosts of the
flowering plants that now number over 150,000 species.

There must have been a mighty struggle for occupancy of the really
desirable plant sites soon after the rise of these immediate ancestors
of our modern plants. For there is every evidence of the progressive
dwindling of those still more ancient holdovers from the Carboniferous,
and the steady encroachment of the newly arisen and obviously vigorous
young race. As we get higher up in the strata, or, in other words,
nearer to the present, there are literally thousands of these immediate
ancestors of our modern flora, and it is not very long before herbs,
particularly grasses and sedges, begin to be common, together with other
monocotyledonous plants such as palms. One not unlike our coconut palm
has been found in some of these strata in France.

While this period records the origin of hundreds, and there are probably
thousands of unrecorded species which are very near our modern
descendants of them, it was also a period when the earth’s crust was in
an almost constant state of restlessness. Ice periods, huge inland seas,
great volcanic upheavals, and the thrusting up of mountain chains such
as the Alps, Himalayas, and some others, were only a few of the
disturbances to the orderly procession of this wholly new type of
vegetation that doomed the older kinds and subsequently conquered the
world. The spread of this new element in the plant kingdom was greatly
helped and sometimes greatly hindered by land connections between
continents, now separated by the oceans. The giant redwoods, now
isolated in a few localities on our Pacific Coast, were found then
nearly throughout the world. Because of these changes of land areas and
some others of even greater influence on plant growth, such as climate,
there was a constant shuffling of floral and, of course, animal
elements, so that by the end of this period the new type of flora had
spread throughout the world, but with here and there very local
occurrence of certain genera and families, some of which have persisted
to the present day. As we shall see in the last chapter of this book,
certain whole families are confined to restricted areas; the cactus and
pineapple family, and the genus _Helianthus_, or sunflowers, for
instance, are, with one or two trifling exceptions, wholly American. And
we have already seen how many food and other useful plants were first
found here by the Spaniards--chocolate, tobacco, corn, the potato, and
others.

It would fill the rest of this book to enumerate the plants that
flourished toward the end of this period, and, in fact, it might almost
be said that the flora of those days was not very different from our
own, only it was distributed in different ways and mixed in very
different proportions. With the disappearance or partial dwindling of
more ancient groups, the rise of the plants that immediately preceded
our own ushered in a new era in the history of the plant kingdom.

[Illustration: FOSSIL AND LIVING ALGÆ COMPARED. C. A living algal pool
colony near the Great Fountain Geyser, Yellowstone Park. (_After
Walcott._) B. Fossil calcareous algæ. _Cryptozoön proliferum_ Hall, from
the Cryptozoön ledge in Lester Park, near Saratoga Springs, N. Y. These
algæ, which are among the oldest plants of the earth, grew in
cabbage-shaped heads on the bottom of the ancient Cambrian sea and
deposited lime in their tissue. The ledge has been planed down by the
action of a great glacier which cut the plants across, showing their
concentric interior structure. (_Photographed by H. P. Cushing. Pictures
and explanations of them from “The Origin and Evolution of Life,” by
Professor Henry Fairfield Osborn, who kindly permitted their
reproduction here._) (_Courtesy of Brooklyn Botanic Garden._)]

[Illustration: PROBABLE LANDSCAPE IN THE CARBONIFEROUS AGE. ABOUT THE
TIME COAL WAS IN THE MAKING. (_After Patonie_) 1. Tree fern 2. Giant
ancestors of our horsetails. 3 and 4. Ancestors of our club mosses. 5.
_Cordaites_, a primitive type, or perhaps even the ancestor of our
modern evergreens. At this time no herbs and no plants with petals, were
known, nor for ages after this period. (_Courtesy of Brooklyn Botanic
Garden._)]

At the end of this period an event of commanding interest occurred,
because it happened only some 40,000 years ago. With it came the
encroachment from the north and south poles of the last of the great
continental glaciers. There had been many before, stretching over a past
period of time, but as the last of these great ice invasions it is the
most interesting to us. It crowded all these temperate and even
subtropical plants that then grew up in the far north toward the
equator, and scraped clear of vegetation every part of the earth which
it covered. In the volume on geology you will find an account of the
extent and thickness of this great ice sheet, which ultimately receded
to its present home. As it went back the plants crowded forward to
occupy the freshly released land, the far northern or glacial first,
followed by waves of other kinds. Some of the glacial or northern plants
were left on the tops of the highest mountains, where to-day they
persist in complete isolation, nearly all their friends and associates
of that greatest of all winters having left them for points farther
north. Many students of plant geography think that wave of plant life
creeping northward to occupy the region uncovered by the retreating ice
is still going on, and recent studies appear to show in at least one
isolated mountain in the Adirondacks that the survivals of the ice age
which have been isolated on its rocky peak ever since are in
considerable danger of being crowded out by invaders from the lowlands.

Not all the geological changes which have remodeled the earth’s surface
have been mentioned in this brief history of those plants that preceded
our own, nor have anything like all the plants occurring in the
different strata been even hinted at. But the thing which has been
stressed and for us to fix in our minds is that all our present
vegetation literally has its roots deep down in the earth. Some, as
_Lycopodium Selago_, go back no one knows how many millions of years;
others, like the flowering herbs, are much more recent. We come to
understand how recent we are and what a comparatively brief flash in the
pan all our modern development both of plants and in man has been since
the last glacial period only by looking for a moment at what has
happened in the past. In the account of the Carboniferous plants we
found that there remained after that period only about 19 per cent of
the earth’s age in which all the changes since then could have come
about. If, as may well be possible, this period has been about
19,000,000 years, then the mere 40,000 years since the last Ice Age
seems a brief period indeed. As some one has written, to contrast all
man’s historic period, back to the days of the most ancient Chinese
manuscript, with that long journey from the dim past which the plant
world has slowly accomplished, is to realize that we are “as the
flashing of a meteor through the sea of night.”

Fossil plants then, and this delving into the dead past of the plant
world, reveals to us as nothing else can how much the modern plant
kingdom is literally built upon a mighty race of ancestors. Some
perished as did the _Cordaitales_, but left descendants who themselves
gave rise to other groups that survive to-day. To look over a list of
the fossil plant genera of the different strata is to visualize a drama
the like of which no one living will ever see replayed, the results of
which are recorded all over the world with its changing panorama of
vegetation.

5. PRESENT-DAY PLANTS AND WHERE THEY COME FROM

There are living to-day somewhere about 150,000 species of flowering
plants; half a hundred conifers or gymnosperms; about 3,500 ferns; 500
club mosses; over 70,000 bacteria, fungi, and lichens, and probably over
20,000 species of algæ. The estimates of the last three divisions are
more or less uncertain, as many species are still being discovered.

From what has just been read regarding the plants of earlier periods it
is at once clear how completely the flowering plants have conquered all
their ancient forbears, and what a pitifully small remnant of once proud
and ancient forests are now represented by our club mosses and
horsetails. That process of crowding, of the dominance of one kind to
the exclusion or even extinction of others is still going on, and, as we
shall see in the last chapter, often on a great scale.

If the period just after plants were first known on the earth may be
called the Reign of Algæ, and subsequent periods were typified by still
other kinds of plants, then our present period is _par excellence_ the
reign of flowering plants. In numbers of individuals they are still far
outclassed by such cryptogams as the fungi, bacteria, algæ, etc., but
their dominating influence in the plant world is unquestioned.

While all our present vegetation must have been derived from preexisting
types, all of it is not necessarily directly descended from species
which from their fossil records we know to have existed in geological
periods older than our own. While the fossil record of the times
immediately preceding the last ice age is a much more complete one than
for many other periods, it fails to account directly for the great bulk
of our varied flora of to-day. While ferns in great variety,
gymnosperms, and hundreds of flowering plants are known quite
definitely, they total only a minute fraction of these groups to-day.
Even granting the always imperfect nature of the fossil record, and we
have seen what an accident the formation of a plant fossil may be, and
it is common knowledge how few comparatively have ever been
recovered--even granting all this, there still remains a large part of
our present flora of which the origin probably dates from comparatively
recent times. So overwhelmingly true is this that of the Compositæ, or
daisy, family, now numbering over 11,000 species, scarcely a handful of
fossil species have been found. And in all collections of fossils the
woody plants far outnumber the herbs, perhaps because of the greater
probability of their being thus preserved rather than to any actual
scarcity of herbs in the upper strata. And yet herbs to-day outnumber
woody species over two to one. While it is true, then, that our present
flora must have been derived from preexisting races, it is also true
that much of it is apparently derived from plants that do not date very
far back into the past. A few main _types_ of flowering plants
unquestionably are to be linked with fossil genera, but these types have
now branched out into a wealth of detail that may not have existed and
is certainly not recorded in the fossil record.

Some of these types stand out with remarkable clearness, notably
magnolia, willows, poplars, walnuts, birches, oaks, figs, sassafras and
its relatives, the rosales, the pea family, the spurges, maples, grapes,
linden, myrtle, ginseng, and some others. All these, and in not very
different aspect from their modern representatives, have been found in
the fossils of the different and usually more recent strata before the
last Ice Age. But the total fossil record of even these well-known
genera is only a fraction of their modern development, and we are
constantly confronted with the apparent dilemma of accounting for a
present wealth of forms based upon an obvious poverty of ancestry. While
the whole race of flowering plants is certainly a new one, as such
things are reckoned fossilwise, there has been a fecundity in the origin
of new species among these lusty upstarts that is simply amazing. How
that, in part at least, has been accomplished will be considered in the
final section of this chapter. Not only among these present-day plants,
but all through the story of the development of the plant kingdom, we
have been reading and writing of the changes of form and structure, some
of which have been of far-reaching consequences. It is clear enough that
if new types of vegetation and different races of plants have come into
being and so modified the complexion of the plant kingdom, those changes
must have first arisen in individuals which had within them some
capacity for change, and furthermore the ability to use the change to
their advantage. While, as we have seen, the losses have been
tremendous, no one, with even this brief history of their development in
mind, can doubt that there has been progress toward our present
perfection of plant life.

6. HOW PLANTS CHANGE THEIR CHARACTERS AND BECOME NEW SPECIES

It was with something very different in mind than the changing of plant
characters that Cardinal Newman once said: “To live is to change, and to
be perfect is to change often.” And yet nothing better expresses the
facts of plants’ ability to change and the results of it than this reply
of a great churchman to critics who could not or would not understand
the truth of his now famous reply.

It is perhaps best to begin any discussion of the changes in plants by
remembering a few simple facts regarding changes in ourselves. “Like
father like son” is something more than an old saw which we repeat for
centuries without stopping to think whether it is true or only half
true. As with so many speeches of the sort, this is just precisely a
half truth, for while sons are more apt to be like their fathers than
other men, we all have within us the capacity, whether expressed or not,
to change very considerably. In other words, all living things may be
said to be a reflection or, perhaps better, the result of two divergent
tendencies, one of which tends to make like produce like, and the other
to produce something different.

Upon the ability of like to produce like rests the continuity of those
plant groups, well exemplified by _Lycopodium Selago_ and the ginkgo,
which, through all the changing panorama of the history of the plant
world, have steadily produced individuals so close to the ancestral type
as to be essentially indistinguishable from it. It is upon the
possession of this ability that all the different races of plants depend
for the unchanged perpetuation of their kind. And, as we shall presently
see, it is also upon this very ability that the new forms that do arise,
rely for holding fast to their differences.

While it is true, then, that like tends to produce like, it is also and
perhaps even more true that they do not precisely do so. In fact, they
never do absolutely, and it is the degree of divergence from the type
that different plants or animals exhibit, which is the measure of their
ability to vary, or “produce something different.” Upon this capacity to
vary, from whatever cause, rest all the changes which have occurred in
the plant world, and, as we have seen in previous chapters, that has
been by no means an insignificant affair. We know, in fact, that while
one plant of _Lycopodium Selago_, than which scarcely any other now
living has had greater opportunity to become fixed in its characters, is
much like another, no two of them are actually identical. Nor are any
two plants of the same species ever precisely alike, any more than two
children, even of the same parents, are. The tendency for like to
produce like is matched then, or sometimes exceeded, by an almost
equally strong tendency to vary.

Heredity on the one hand and variation on the other are the two forces
upon which the origin of new species or kinds of plants is based. Both
of these work in rather definite ways, some of which are fairly well
understood, but many of which are still among the things that scientists
are striving to clear up. As the capacity to inherit characters from one
generation to another reflects itself in the generally stable conditions
which the plant world exhibits, while the capacity to vary is the only
source of new forms, it is quite naturally the variations of plants from
one generation to another which have been most studied. And the study of
variation in plants is not the simple thing we might assume it to be,
having in mind only the well-known fact that no two organisms are
exactly alike. Wherein do they differ? Are their perhaps temporary or
even quite casual differences passed on to their progeny? These and
many other questions about variation make it at once the most
complicated and often one of the most fruitful subjects of plant
research. It is clear enough that with the bewildering variety of
different plants in nature it is next to impossible not only to record
accurately the amount of variation or its probability of being handed
on, but least of all to arrive at any clue as to the origin of that
variation. Because of this, and still more because practically no one
has ever seen the actual origin of a new species in nature, for we only
see the finished product, practically all our knowledge of the laws of
variation has been derived from studying cultivated plants. The ease of
controlling them and of recording thousands of observations of their
characteristics has made the work of the plant breeder, and others who
study variation in the vegetable world, much more of an exact science
to-day than the mass of often interesting but usually unrelated data
that crowd the pages of older botanical literature.

One of the main facts about variation is that it is itself a very
variable thing, and the nature of those “fluctuating variations” which
are so common in nature well illustrate the point. Within what we know
as a species there are many individuals that vary one way or the other
from a fairly central, we might almost call them normal, mass of
individuals which are typical of that species. Nearly all these forms on
the fringe of the species due to the environmental changes and not to
changes of hereditary constitution will, if left to themselves, tend
through their progeny to become more like the central mass as time goes
on, while their position, or some other equally nontypical edge of the
fringe, will be taken up by other variants from the average conditions.
The amount of this fluctuating variability among plants is beyond
calculation, and its action has often been likened to the swinging of a
pendulum, which of course spends twice the time passing through the
center of its arc, that it does on the limits of it. This very nearly
expresses the proportion of fluctuating variants to the mass of typical
individuals in many species of plants. In many others, often peculiarly
unstable species, the number of individuals at the fringe is very large
indeed. Sometimes there may be one or more that do hold their
characteristics, in which case we know that they are not true
environmental variations but have actually a different constitution.
These will be considered presently under another and different sort of
variability. But, speaking generally, these fluctuating or environmental
variants are merely forms of the species, and, other things being equal,
they will not actually originate new species.

It should be emphasized here, and before we go further in our discussion
of variation, that species and varieties are after all largely creations
of the mind of man rather than the reflection of actuality in nature.
When we speak of a “species” it is merely a term which through usage by
botanists becomes the symbol of a group of plants more like one another
than like anything else. It is obvious that it is therefore necessarily
an inaccurate designation of the actual conditions found among plants,
which might almost be considered as all belonging to one great group of
which, for our convenience in referring to them, we mark off units
(families, genera, species, etc.), much as units are marked off on a
rule. Species, then, and varieties of plants, notwithstanding the
utmost refinement of method used in designating and describing them, and
this is historically the most ancient and the most widely developed
phase of botanical science, cannot reflect the true conditions, and for
a number of reasons. The chief one is that species differ in usually
several characters one from another and in large genera there is often a
bewildering recombination of characters of the genus in the species
belonging to it. Species and varieties are concepts of convenience, nay
of absolute necessity, in talking or writing about plants, but hardly
expressions of exact truth.

With this in mind we can appreciate the position of those plant breeders
who insist that the basis of differences in all plants are the simplest,
so-called, factor expressions, which can be isolated and studied with
some approach to exactitude in experimental cultures. A factor may be
defined as the hereditary determiner or base, which, either singly or in
conjunction with other factors, is expressed as a character, such as
tallness in peas, or brown eyes in human beings. Such studies have built
up a body of information about variation in plants that show it to be of
several kinds and with different chances of being passed on from one
generation to another.

It was noted in the paragraph before the last that fluctuating variants
were sometimes so far off the usual that they might almost be considered
distinct forms or varieties. Many such changes appear to be the result
of different conditions of the local environment, due to changed
conditions rather than to any internal difference in the constitution of
the plant itself. A familiar illustration of environmental variation
may be seen in lima beans. In any considerable number of plants one
often finds smaller and larger pods, either sparsely or well filled with
beans. If the beans from the small-podded, few-seeded variants are
planted they will produce, apparently quite indiscriminately, large and
small podded progeny, just as there will result a mixed progeny if only
beans from the well-filled and large-podded kind are sown. In other
words the plant fluctuates about a general average which typifies the
usual or mass characteristics of the species. One should not, however,
regard _all_ variations of the character in lima beans, or any other
plant as environmental or fluctuating ones, for some of them may be due
to differences in hereditary constitution. And these could only be
determined by breeding tests.

Environmental variations are as frequent as the ever-changing conditions
of plant growth may determine, and it is common knowledge that such
diversity of the environment and the variants resulting from it are
extremely frequent.

A much more fruitful source of new forms of plant life results from
natural cross-fertilization, which, as we saw in an earlier chapter, is
the nearly universal condition in the plant world. If species and
varieties can be distinguished only by factor differences, as the plant
breeders no doubt correctly insist, it becomes obvious enough that we
have in cross-fertilization to consider not alone the factor differences
of the pistillate or female, but also of the staminate or male
contribution to the union, and how these are reflected in the progeny.
Our knowledge of this has practically all been based on work done on
cultivated plants under control conditions and it shows some
interesting developments which occur from crossing.

If garden peas with, let us say, reddish-purple flowers are crossed with
white-flowered ones, the progeny will not be a mixture of these colors
but all reddish-purple. If all danger of subsequent cross-fertilization
is excluded this first generation of reddish-purple progeny will
themselves produce reddish-purple and white progeny in the ratio of
three to one. But the extraordinary part of it is that in the third
generation all the white and about one-third of the reddish-purple
plants will breed true to color. The balance of the reddish-purple
plants, which comprise about two-thirds of the second generation, will,
if their seeds are germinated, produce colored as against white-flowered
progeny in the three-to-one ratio. In other words, these artificial
crosses, made by the plant breeder, and this splitting up of hybrids
which has been many times verified, are seen to be very fertile causes
of the origin of new forms of plant life, if only the factor and
character differences in the ancestry be sufficiently complex. With no
two plants precisely alike, with cross-fertilization so nearly
universal, and with all characters, not a single character or factor
expression, as in control conditions likely to be affected by the cross,
it may be seen how fruitful a source of new forms this natural crossing
may be. It is, in fact, not surprising that plants vary, but that the
force of heredity will hold them into such recognizable categories that
the red maple, or white ash, or blue cohosh are, with thousands of other
species, after all fairly definite designations without which talking
and writing about plants would be all but impossible. Some of our most
beautiful garden plants have arisen either as the result of natural
crossing, or crosses deliberately made by the plant breeder. The scores
of forms of the common garden lilac have mostly come about by such
crosses, although many other garden plants have arisen by still another
kind of variability.

The effects of crossing which have been so briefly noted were not
understood, as indeed the cause of them is still unknown, before 1865,
when Gregor Mendel, an Augustinian monk, published the results of his
work on peas, which furnished the basis for all subsequent work on this
kind of variability. His work was neglected until 1900, when what is now
known as Mendel’s law, involving the Mendelian ratio already noted, was
rediscovered by three independent workers. It is now practically
universally accepted as the way in which natural or induced hybrids
transmit their characters.

There remains still another type of variability which has been noticed
from very early days, and received the name _sport_, because quite
suddenly, from a crop of otherwise similar specimens, one or a few
plants showed marked and permanently transmitted differences from the
average condition. Such sudden offshoots, which occur rather frequently
in many plants, are known as mutants, the process as mutation. Hugo de
Vries, a Dutch botanist of world-wide fame, was the chief modern figure
who drew attention to mutants, and explained how they differ from
fluctuating variants in that while these tend to revert to the average
or mass conditions the mutant, once it appeared, held true to type. A
well-known example of mutation is the cabbage, brussels sprouts,
cauliflower, and kohl-rabi, all of which are sports or mutants from a
weedy seaside plant of the mustard family, native in Europe. Since
their appearance, hundreds of years ago, they have held their essential
characters. If they had been environmental variants they would in all
probability have reverted to their weedy ancestor. Hundreds of sports or
mutants have been recognized and isolated, so that many of our most
valuable garden plants have arisen through this ability of plants to
vary in often sudden and rather startling degree. The gardener and
horticulturist, from long observation and a keen sight for valuable
novelties, have always known that sports are fruitful sources of new
forms of plants, but De Vries first scientifically studied them and
worked out the principles by which they apparently react. The cause of
them is still unknown.

While the cause of mutants has not yet been revealed, we have already
seen that the two remaining kinds of variability are due to changes in
the environment, or to crossing. Charles Darwin when he published his
“Origin of Species,” than which no other book has so completely
revolutionized modern thought, did not state the cause of those
variations of which he was our greatest observer. He did state the now
universally accepted law of the “Survival of the Fittest” which explains
how, once these variations make their appearance, the inexorable
conflict of nature would automatically weed out the unfit. We have seen
all through the course of this history of the plant kingdom how whole
types of vegetation have been overthrown to give way to other types
better fitted to survive. That process is going on with just as
inexorable results to-day as it has down through the ages. While Darwin
never claimed that such a purely selective process could initiate new
species, many of his partisans who waged battle for him during the first
years of the tremendous opposition his views encountered, did so claim,
and probably wrongly. The actual cause of the origin of new species,
except those demonstrated to result from new combinations of already
known characters, through crossing, cannot be explained through the
natural selection of plants or animals which exhibit favorable
variations. We see their effects; it is obvious enough, that those of
value tend for the survival of plants having such variations, and it was
natural enough that older students of the problem should mistake these
effects for the cause of them. The process of selective elimination
constantly going on does tend to fix certain favorable variations and
untold millions of plants have had their day in the past due to their
possession of such, and the killing off of their less fortunately
provided associates. We speak of this great march from the simplest
organism up to our most complex plants and animals as their evolution,
but we must never forget that it has gone step by step, by one or the
other methods by which we have seen that plants vary, or perchance by
some undetected method, and that while the results of it are for all to
see, the causes of that infinitely slow and quite often wayward
variation are not understood. Upon such a conception our modern plant
life is seen to be a development of plants that have gone before, that
all existing life is derived from preexisting, and not from providential
interposition or special creations. All through the long marches of
plant evolution there appears to be a definite and final goal toward
which it tends, but we do not know the direction, least of all the
object, of that goal. In fact, there may be many goals, just as there
are the diversity of ambitions among human beings. In tracing the
present ascendancy of our flowering plants from their links with the
past perhaps we shall find no better statement of their present
condition or destiny than to repeat Cardinal Newman’s reply: “To live is
to change, and to be perfect is to change often.”

CHAPTER VIII

DISTRIBUTION OF PLANTS

We have seen in the previous chapters how many and how varied are the
activities of the plant world and in this final one we shall get a
glimpse of what these activities have produced. All the delicate
mechanism of food getting and the manufacture of starch; the
fertilization of flowers by insects, the wind or water; the response to
changing light and to climate--these and scores of other activities of
plants have resulted in the present vegetation of the world being what
it is. Here we see the final reflection or register of not one but all
the kaleidoscopic evidences of plant response and activities and history
working in harmony, or, as we shall see presently, sometimes in violent
conflict, and leaving as the result the wonderfully varied vegetation
that now covers the earth. If we could read aright the story of which
the vegetation of any particular country is the silent narrator, it
would tell us not only what happened in the past but what is likely to
happen in the future.

Plants, by what amounts to a kind of fatality, are rooted to the spot
where they grow so that, unlike animals, their rapid distribution
appears to be almost impossible, and yet the tremendous distances that
some species have traveled seem like a pretty successful protest against
the fact of the anchorage of individuals to the point of their origin.
It is more than a successful protest, for it amounts in many species to
an active campaign for dominance, to the exclusion or extinction of less
aggressive neighbors, so that in any field or meadow or forest there are
silent struggles constantly going on. Some of these are so inexorable in
their results that they change not only the frequency of occurrence of
the individuals involved, but sometimes the whole type of vegetation.

The competition to occupy just as much of the favorable plant sites as
possible has been much aided by many species possessing means for the
dispersal of their seeds or fruits that are ingenious in the extreme.
Some of these are written plainly enough in the structure of the seed
and its wonderful adaptability for the peculiar conditions to which it
will be subjected. Before considering some of these structures we may
profitably see how some plants look after the dispersal of their seeds
within their own limited sphere of action.

In hundreds of plants the ripened pods, instead of being erect as their
flowers have been, are pointed downward about the time the seeds are
ready to be released, and their harvest is sown, sometimes by deliberate
movements, in the immediate vicinity. No great areas are captured by
such plants, except by the slow process of successive generations
extending their range a few inches or at most a few feet a year. The
great bulk of all seeds never do grow into new plants, but in those that
only shed their seeds close to the parent plant the opportunity to reach
new sites is by that much restricted. The chance of the species getting
very far afield except by slow invasion of the neighboring region is
limited. A few of such plants show remarkable ingenuity in reaching the
utmost distance possible, perhaps the most effective cases being those
that shoot their seeds by explosive bursting of their pods. Nearly all
the violets do this, often shooting seeds several feet from the parent
plant. Many plants of the pea family have pods that are twisted, which
upon splitting release the previously pinched seeds so suddenly that
they are shot considerable distances. In the common witch-hazel (Figure
111), the seed is shot through the air often as much as thirty feet.

[Illustration: FIG. 111.--THE WITCH-HAZEL

(_Hamamelis virginiana_)

Is a fall or winter flowering plant which shoots its seed sometimes as
much as thirty feet. Native of eastern North America.]

But with even the greatest ingenuity and the most explosive bursting of
pods, most plants could never capture much new ground, and their very
existence as a species is often contingent on their ability to spread,
if these various methods by which plants shed their seeds were not aided
by outside help. Some of these have had conspicuous and almost startling
results.

1. DISPERSAL BY ANIMALS, THE WIND, AND WATER

The seeds or fruits of those plants that are used for animal food are
often carried considerable distances, while the thrifty squirrels’
burying of acorns is everyday knowledge to those who have seen them
busily engaged in the making of winter stores, or the planting of new
trees, often many rods from the parent tree. In years of plentiful seed
production squirrels have been known to plant great quantities of seeds
of the Douglas fir, thereby hastening the establishment of one of the
greatest evergreen forests in the west.

While some seeds are destroyed by passing through the digestive tract of
animals many are not harmed in the least. From over two hundred and
fifty different kinds of plant seeds fed to a variety of birds over 80
per cent germinated perfectly after passing through their digestive
tracts. And perhaps the most remarkable case is the seed of a pondweed
said to be incapable of germination until it has passed through a bird.
This plant grows in fresh water ponds in great quantities and is much
eaten by wild ducks. From the stomach of one bird over three hundred
such seeds were recovered. In the Eastern States a common feature of our
farms is the red cedar or juniper scattered along fence rows, nearly all
of which are due to birds roosting on fence rails and dropping the seeds
after passage through their digestive tract.

We get some idea of the part birds play in plant dispersal when we
realize the enormous number of them that make their flights twice a
year, often over great distances. Wild ducks, in untold millions, travel
from the far north to the tropics, each carrying their freight of
seeds, sometimes as food and often mechanically clinging to their feet.
The writer once saw at Gardiner’s Island and Montauk, Long Island,
hundreds of thousands of tree swallows which feed on the fruits of the
bayberry (_Myrica carolinensis_). So dense was the flock that they
covered nearly every inch of the bayberry patches, and after eating no
one can calculate how many million seeds they started off toward their
winter home. Stopping as they do each day on their long flight
southward, is it any wonder that the bayberry is one of the commonest
bushes along the Atlantic coast?

With flights of birds stretching from the Arctic to the Antarctic,
sometimes a single species making such a flight during its migration
period, and hundreds of species making shorter flights twice a season,
it is easily seen how birds can carry seeds for long distances. That
they do so carry them is common knowledge and in eleven wild ducks
examined by H. B. Guppy, he found nearly 300 seeds of bur reed,
forty-one of pondweed, 270 sedges and 222 seeds that he could not
identify. Nearly all these seeds germinated when sown, some sprouting
more quickly than if they had not passed through the bird’s stomach.
Some few seeds which would usually be dormant for one, two or even three
years, have their germination unquestionably hastened by passage through
birds, who may be looked on in some cases at least as “flying
germinators.”

Some sea-flying birds have been captured over five hundred miles from
land and seeds of a buttercup and of the sea blite recovered from their
stomachs. One student of the flora of Spitzbergen has stated that nearly
all the plants of that cold region have come from the northern part of
the Scandinavian peninsula through their carriage by birds. One of the
commonest plants of that region is the crowberry, which is a favorite
food of birds. The plant is found throughout the Arctic regions and on
high mountain tops to the south of it, such as the Alps, our own
Adirondacks and White Mountains, and many others. There are some islands
in the Pacific known to have received a few of the plants now growing on
them by birds carrying the seeds from other regions, often thousands of
miles away. Several species of birds are known to make sustained oversea
flights from Labrador to South America, and one from Alaska to Hawaii.
In such flights stopping is impossible, so that the carrying of fresh
seeds and spores is always likely and probably more quickly accomplished
than by any other means of transport. In New Zealand a northern European
bird was once found with the seeds of two species of marsh arrow grass
in its stomach, both of which germinated. The plants are native in the
cooler parts of the north temperate zone.

Not far from New York, at Montauk Point, Long Island, there was found a
few years ago some plants of the cloudberry, a kind of blackberry with
amber-colored fruits, which is otherwise unknown in that region but is
common enough in the Arctic and on mountain tops northward. That point
of land, extending out to sea, is a favorite stopping place for
migrating birds and to them was undoubtedly due the introduction of the
plant so far south of its true home. Scores of similar cases could be
cited which confirm the observations of naturalists all over the world
that birds are among the greatest aids to plants in securing wide
dispersal. Of course the factors of favorable or unfavorable conditions,
once the seed is deposited in the new home, operate to keep plants from
the tropics from settling permanently in colder regions and _vice
versa_, but we cannot escape the conclusion that the sky is filled
during certain seasons with millions of seed carriers that have, in many
cases, populated their stopping places with foreign plants.

Other animals than birds carry fruits and seeds, besides those that eat
them. Some fruits like the _Martynia_ (Figure 60), are so arranged that
no animal with fur can avoid catching some if they come in contact. The
prickly fruits of cocklebur resulted in one species of that weed from
the steppes of Russia being carried all over southern Europe in a
comparatively few years. Tickseeds, _Bidens_, and all the hosts of
plants that have prickles, burs, spines or what not attached to their
fruits, have, by the possession of such devices, a better chance for
dispersal of their fruits than those not so provided. Others, again,
have various coatings of mucilage which stick to animals and thus help
plants to overcome their chief drawback to dispersal--their anchorage at
the place of birth.

THE WIND

The great trade winds, the violent hurricanes and monsoons of Asia, are
all active and constant aids to plant dispersal. The fruits of many
plants are provided with various devices to insure buoyancy in the air,
such as maple, ash, and most seeds of pines and their relatives,
birches, poplars, and willows, all of which may be carried distances of
a few hundred feet in ordinary winds. In the buttonball tree, the
milkweeds, fireweed, and many other plants there are feathery
attachments or plumes that insure their seeds or fruits being carried
very long distances indeed in regular or violent winds. But in the daisy
family or _Compositæ_ we find nearly all the eleven thousand species
provided with a plumelike attachment of their light fruits, familiar
enough in the dandelion, which may explain their being more widely
distributed than any other plants. Some of them, however, are carried by
animals, as they produce, in certain genera, barbed or hooked achenes.

The whole seed of some plants is so small that it can be lifted bodily
by the wind, for instance _Rhododendrons_ and many other heaths, one of
the hanging pitcher plants of tropical Asia, many orchid seeds, and of
hundreds of other plants. Many of these are less than one ten-thousandth
of a gram in weight and, with dust and the spores of nearly all
cryptogams, may be transported thousands of miles. When it is recalled
that the dust from a volcanic eruption at Krakatoa in the Pacific was
picked up on London window sills, and that some seeds and nearly all
spores are as light as most dust, the wind as a plant dispersal agent
becomes significant. In the western part of the United States over 800
million tons of dust are carried over 1,400 inches in a single year,
according to estimates by J. W. Evans in his article on “The Wearing
Down of Rocks.” Some effects of wind dispersal of seeds and spores
furnish interesting data to the plant geographer.

In the Bahamas the natives speak of “hurricane grass” as a plant that
was unknown on Great Bahama Island before August 13, 1890, when there
was a great hurricane. Soon after this the sedge, which had been blown
over from another island, began to be common on Great Bahama, where it
is now thoroughly established. On Krakatoa near Java a violent eruption
in 1883 completely destroyed the vegetation, covering the island with
volcanic material. In thirteen years over sixty species of plants had
arrived on the island, of which about twenty had been blown there as
seeds or spores. Birds had carried about 7 per cent and the remainder
had come by other means. No plants with sticky burs or other devices for
catching in the coats of animals were found.

It is among the _Compositæ_ or daisy family that the wind is seen to
work most effectively as distributing agents of its light-plumed fruits.
In the Falkland Islands, St. Helena, and Prince’s Island, all from 300
to 1,500 miles from the nearest land, species of _Senecio_ or groundsel
have been found that may well have been wind-driven onto these remote
islands from the mainland. In fact the whole genus _Senecio_, consisting
of over two thousand species, and of world-wide distribution, has in all
probability been spread largely by its wind-borne achenes. They are not
edible, nor are they suited to carriage by the ocean currents, but some
of them are known to stick in the plumage of birds.

But it is hardly necessary to cite these far-flung examples of the
wind’s action in distributing seeds, for there are many interesting
cases much closer home. The tumbleweeds, such as the false indigo and
certain grasses, are familiar sights scudding before the wind over
prairies in the West and open places in the East. By a kind of foresight
the winged seeds of the pines are so weighted, due to lack of symmetry,
that instead of sailing quickly to the ground, they tumble and flutter
about, thus prolonging the time of flight. And in the linden the curious
winglike attachment from which the stalk of the fruit arises is
admirably fitted to slide over the snow and ice upon which, through
their often tardy falling, they are deposited. Scores of such
adaptations of structure to function are known, where there seems direct
response to conditions and there is the temptation to say that such
adaptations are caused by the wind or other agency. Nothing could be
farther from the truth, as plants do not produce winged seeds or
luscious fruits to insure seed dispersal, but the seeds of plants having
such devices, from whatever cause, are naturally favored in the
ceaseless struggle to occupy new land, which is quite another thing.

WATER

The scattering of seeds along streams is too common a process to need
more than a mere mention here, for it is to be seen along any fresh
water stream at harvest time. But seeds that may be carried by ocean
currents have a much greater influence on the distribution of plants,
such as the coconut palm, already mentioned among the food plants, and
now common throughout the tropical world.

The number of seeds that will float in sea water and still keep the
power of germinating is not very great. Most seeds sink at once; many
will float for months, but are useless when they reach land; but those
that will both float and grow afterward have worked some curious changes
in the floras of different islands. Sometimes the great ocean currents,
like the Gulf Stream, appear particularly futile in the fruits they
carry such long distances, as the pods of a tropical vine from the West
Indies are not infrequently found on the coast of Norway and even of
Nova Zembla, of course uselessly. But many ocean currents, particularly
in the Pacific, have carried fruits and seeds thousands of miles, they
have even carried so-called floating islands of vegetation bodily.

Perhaps the most remarkable case is that of _Entada scandens_, a
tropical vine of the pea family, bearing large pods, sometimes several
feet long. The plant is not typically a seaside plant, and there is
evidence that fruits matured in the shade of its usual forest home will
not float. Those that grow nearer the coast and more in the open
develop, through partial drying, a small air chamber inside upon which
the seed depends for buoyancy. Its original home is apparently somewhere
in Central America, from the west coast of which it spread over the
Pacific to the shores of the Indian Ocean. Over the Atlantic it has
reached the shores of tropical Africa, and in fact wherever ocean
currents cast up their refuse on lonely beaches parts of the giant pod
or individual seeds of _Entada scandens_ are found. Partly fossilized
remains of them have been taken from peat bogs along the coast of
Norway, of course dating since glacial times, but showing by their
presence there how long this water-borne seed of the pea family has been
attempting to populate the earth. Of course all that do not reach tropic
shores are lost, but nearly throughout the Pacific Islands, with some
exceptions, the vine is now established. The extraordinary feature of it
all is that scarcely half the seeds of the plant will float at all,
nearly all inland forms sinking at once in the fresh water rivers into
which they may chance to fall. Only those that grow near the sea, in
mangrove swamps and the like, or at any rate near brackish water, will
float. These, however, apparently float indefinitely without loss of
germinating power. There is abundant evidence that many plants of
oceanic islands have similar characteristics so far as their inland and
seaside forms are concerned.

While _Entada scandens_ has spread in spite of unfavorable adaptation
for seed floating, there are some plants whose seeds always float, and
in spite of the sea water retain their power of germination. H. B.
Guppy, from whom much of the above data are taken and who has
experimented for years on the buoyancy and germinating power of
sea-borne seeds, reckons about two hundred species that may have spread
by ocean currents. Many of these are nearly world-wide in their
distribution within their climatic requirements, and most are confined
to the tropics.

2. INVASION, MIGRATION, AND RELICS

It is perhaps a natural enough question why such elaborate and effective
methods of seed dispersal are necessary and why plants, once they grow
in any particular locality are not satisfied to stay there. The answer
to this is that individual and racial competition is so great that
without means of dispersal, which may be looked on as equipment for
seeking a more favorable site, species would often be crowded out.

There is no better place to see this than at the edge of a forest and
grassland. The presence of the forest tells us at once that what may be
described as the forest type of climate must have existed in the past to
have produced the woods. In clearing off parts of this forest the
openings will usually be grassland at first, but never in the end if
nature is allowed to work out the solution. Along the edge of such a
forest will be found a host of pioneers pushing out among the grasses,
making ready, by conditions of shade, protection from drying winds and
other influences, for the seedlings of the forest trees that creep
slowly but resistlessly out to capture areas that by right of previous
occupancy belong to them. In practically all parts of the world, with a
few local exceptions, wherever the forest was the original type there is
this ceaseless struggle to reclaim the open places, often or usually
peopled by grass. It may be set down as almost a rule that if the open
places produce herbs with broader leaves than grasses, the forest will
capture the area many years sooner than if grass alone is the temporary
tenant. Grass by its exclusive growth, its complete monopolization, so
far as low seedlings are concerned, of much light and nearly all
available surface water, is singularly well able to take care of itself
once it is thoroughly established. But plotted and marked areas of this
contact between forest and artificial clearings in it, show that in the
end the forest will win, often at the rate of five hundred feet in a
hundred years, sometimes much quicker than this.

If, on the other hand, what may be called the prairie type of climate
has resulted in the formation of grassland, which has happened in our
own West, in the steppes of Russia and less extensively in many other
places in the world, forests can hardly ever get a foothold. Where, as
in river bottoms, they sometimes flourish, the line between forest and
grassland is sharp and apparently an impassable barrier for trees.

This invasion of immediately adjoining territory is going on constantly
not only by different types of vegetation but by the units of it. The
frequency of different plants in different years, their final ascendancy
or extinction, all point to the struggle for expansion which in a score
of ways the plant world is constantly waging. In many cases we are not
yet able to see the struggle, but only its results, while in some places
the bitterness of it may be gauged by the dead and dying that strew
these silent battle fields.

The dominance of certain species of plants, such as grasses on a
prairie, the fir and spruce in the coniferous forests of our North, the
blue-gum trees in parts of Australia and the giant dipterocarp forests
in the Philippines, are all based on the ability of individuals to
spread from their point of origin. All species of plants must have one
day been of very local distribution and confined to the region where
they were born, but from their often very modest beginnings some of them
at any rate have gone to the ends of the earth. The common bracken fern
is found in nearly every country in the world from far northward through
the tropics to the antipodes, and yet no one knows where its original
home might have been. Somewhere up in the northern Andes it is supposed
that the first ancestor of the huge daisy family had its origin. From
there its many descendants, now ramified into hundreds of genera and
over eleven thousand species, have spread to the very limits of plant
growth. And the daisy family is one of the most recent of all the
families of plants.

The distribution of plants is of many kinds depending on local
conditions of climate and soil, on individual and racial competition, on
methods of fertilization or other means of propagation or seed
dispersal, and particularly upon the distribution of the plant or its
ancestors in past ages. While it is often difficult or impossible to
determine upon which of these factors, or upon what combination of them
the distribution of any particular species is based, certain facts of
plant dispersal appear to be indicated by a study of existing floras. A
few instances must suffice here to illustrate the principles by which
many plants are scattered over the earth, or else restricted to
localized regions, and which, without knowledge of the factors involved,
seem merely the wayward caprice of nature.

In the flora of eastern North America there are many genera that appear
to be endemic there (found nowhere else), but are actually duplicated in
eastern Asia, if not as to species, at any rate by plants so closely
allied as to be of obviously common origin. These plants are unknown in
Europe, or on our own western coast. The skunk cabbage, sassafras,
twinleaf, May apple, Canada moonseed, spice-bush, ginseng, sour gum,
trailing arbutus, fringe tree, lopseed and many others, all fairly
common in eastern North America, are unknown between this and eastern
Asia where, if not the identical species, which often happens, closely
related forms are duplicated. The explanation of such discontinuous
present distribution appears to be that at some time in the distant past
there was a land connection between Asia and the western coast of
America, the remnants of which form the Aleutian Islands, and over which
there was a constant migration of plants and animals. With subsequently
changing climatic conditions on our own western coast, due to warm ocean
currents, most of those Asiatic migrants, or it may have been a
migration in the opposite direction, were crowded out by later types
which now dominate the Pacific coast. There is small chance that these
plants were spread by birds, as an east-west bird migration is hardly
likely. Nor is there any record that the seed of these plants, even
where they might float, would survive ocean transport.

Sometimes the ancestors of now widely separated species or genera once
covered all or nearly all the intervening area, and again sometimes only
a minute fraction of the ancient distribution is left at the present
time. Our own Big Trees of California were once known to grow in
England, Iceland, all through central Europe and eastern Asia,
Australia, New Zealand, southern Chile, and from Texas to Alaska. In the
face of such widespread occurrence in the past their present
distribution over an area of a few square miles is merely a pitiful
relic of ancient grandeur. Scores of cases are known where, instead of a
single outpost as in the Big Trees, there are only a few widely
scattered survivors from a probably much more continuous distribution in
the past. In northeastern North America there grows along pond sides and
fresh-water beaches the shore-weed, a relative of our common weedy
plantain. The only other species, and a close relative, comes from the
southern tip of South America.

[Illustration: SOME OF THE COMMONER PLANTS OF THE DESERT in the
Southwest. The fanlike branches at the left are the ocotillo
(Fouquieria), the two short tree cacti and choya cactus (Opuntia) and
the leafless tree in the central background the palo verde
(Parkinsonia).

(Photo by the late Edward L. Morris, released for publication here by
the Brooklyn Museum.)]

[Illustration: GRASSLAND AND TREE VEGETATION. All over the
world there is a contest between grassland and tree vegetation for
dominance wherever both occur. In this thorn veld in Natal the
struggle is particularly keen. (After Bews. Courtesy of Brooklyn
Botanic Garden.)]

Many other species now existing are to be viewed only as relics of a
bygone, often much more continuous and more widespread dispersal. In the
persimmons, of which over a hundred different kinds are now known, the
original distribution covered all North America, all Europe and Asia,
except the Scandinavian Peninsula, all of Africa, northern Australia and
South America. To-day the genus is restricted mostly to tropical Asia,
southern Africa, northern South America, and in North America it has
dwindled to a handful of species confined to the region south of the
Great Lakes and generally east of the Mississippi. In Mexico and south
of it the genus is better represented. But with the persimmon, as in so
many other types, our existing species are the remnants of preexisting
ones, without a knowledge of which their present dispersal would be
impossible to explain.

It is easy to reason from the foregoing that widely separated but
related species of plants are all either very ancient, or directly
descended from ancient ancestors, and that other things being equal a
widely dispersed species is older than one with a restricted
distribution. It is most certainly true that relics are unquestionably
very ancient, and do actually represent the last outposts of a
preexisting condition. But many isolated plants are relatively very new,
so far as their immediate origin is concerned, as witness the hosts of
young species of the daisy family, some of which have spread scarcely at
all from their obvious point of origin. In judging of the distribution
of even the commonest tree or shrub of our woodlands there are these
links with the past, as well as response to present conditions, to be
weighed if we are to understand the story aright.

Once a plant reaches a new and for it a strange country it is remarkable
how quickly it will often capture the new territory. In the United
States over six hundred of our commonest weeds have come from Europe and
Asia. The daisy, dandelion, wild carrot, many hawkweeds, dozens of wild
mustards, and many others are among the somewhat undesirable immigrants
that now reach over a great part of the country--all brought over by the
early settlers of America. From their home in subtropical Asia the
lemon, lime, and orange have invaded every part of the tropical world.
Once, in the most remote part of the Sierra Maestra Mountains in eastern
Cuba, where only by the most arduous cutting could a passage through the
dense tropical forest be forced, the writer found within a few square
rods an orange and a tree from tropical India. Such cases could be
multiplied, and all over the world we see this endless struggle of
plants to conquer new territory, often at the expense of existing
vegetation. On Long Island, New York, the introduced locust tree,
brought from the southeastern United States about a hundred years ago,
has completely routed the native trees in many places along the north
shore of the island. And in Hawaii, some seeds of a screw pine, washed
up among refuse along the beach or brought in by early aborigines, have
made this Malayan plant a common tree thousands of miles from its home.

3. HOME ECONOMY OF PLANTS, OR ECOLOGY

The geographic distribution of species of plants may be, as we have
seen, the result of the geological changes of the past, of bird
migrations, of more or less fortuitously water-borne seeds, or more
usually of the slow spreading by invasion of those species apparently
not so well supplied with external helps to dispersal. But no matter
where plants grow, nor how they got there, they must fit the particular
environment in which they find themselves or perish. This home economy
of plants, or how they meet the environment and each other, is called
Plant Ecology, a phase of botany now much studied, for it tells us more
directly than most other plant research what the actual response to
various factors of the environment may be. Just as plant distribution is
the reflection of many, usually widely operating forces, so ecology
narrows down to individual plants or groups of them the impact of the
immediately surrounding conditions upon vegetation.

The basis for all study of the response of plants to the conditions
under which they grow must rest upon the response of their different
organs to those factors, just as our general movements are dictated by
sufficient food or air or water to keep ordinary bodily functions going
in the ordinary way. But the study of such plant response has shown that
certain kinds of environmental conditions have resulted in quite similar
response nearly throughout the world. Often totally unrelated plants
assume characteristically similar growth forms where the conditions in
widely separated areas are climatically or otherwise similar. In our own
Southwest we have the dominant cactus vegetation, matched in parts of
South Africa by giant cactuslike spurges. In Mexico we find the wealth
of century plants, which are confined to the New World, matched in the
Old World dry regions by the aloe, a group of succulent plants nearly as
well suited to such areas. The _species_ of plants characterizing
peculiar regions may well be the result of geographic distribution that
rests on more widely operating factors such as we saw in the previous
section of this chapter, but the _type_ of plants growing in a
particular place hardly ever fails to be dictated by the local
condition. With this in mind, a vast amount of time has been spent in
studying the various factors of the environment, such as climate, soils,
altitude, light, etc. And an equally valuable study has been the
response of individual plants or their organs to such conditions. From
this great body of information, obviously impossible to include here, we
all recognize certain well-marked societies or groupings of plants
which, wherever they occur, exhibit similarity of general response to
the different conditions responsible for their occurrence. Once these
typical plant societies or groupings are understood we can recognize
them wherever they may occur, and we shall see that they are as
widespread as are plants themselves.

Just as societies or races of men have often obscure beginnings, reach a
climax, and afterward die, so these plant societies may be considered as
exhibiting a similar progression. What these plant societies are, at
least the more important of them, will be considered in the next section
of this chapter. It should never be forgotten that the _species_ of
plants making up the dominant plant societies in different parts of the
world are dictated by quite other conditions than those that result in
the dominance of the society itself. Perhaps as good an illustration as
any is the aristocratic type of mankind, recognizable throughout the
world by the possession of finer qualities than the common run, but
differing in individuals as much as the best type of Americans, the
British peerage, and the samurai of Japan differ one from the other.

Not the least interesting feature of these plant societies is that we
must view them as associations of plants, often of widely differing
origin due to the vicissitudes of plant distribution, but all taking
their part in the society to which they belong and often, as
individuals, losing their life that the society may live. Upon such a
conception a wood or prairie, or river bank, or salt marsh or alpine
garden upon a mountain summit are, with many other plant societies,
places of intense conflict. More cruel than any human society, these
plant communities exist under conditions where only the individually
strong survive, and only those societies are destined to reach their
climax which can take advantage of every aid, quite without regard for
severe losses or even death to the individual members of it. It is as if
we poured into a crucible molten metals from many different sources, and
after the incredible and relentless forces of manufacture had worked
their magic upon them there resulted a product, purified and cleared of
all dross. So the inexorable and relentless processes of nature work
over the materials found in these plant communities, the results of
which are the dominant types of vegetation in the world to-day. With
this understanding of the part they play in plant distribution we may
now consider a few of the most widely recognized plant societies and see
how they have affected the vegetation, sometimes even the history of the
regions in which they are found.

4. SOME OF THE CHIEF PLANT SOCIETIES

Forests

No one who has ever seen both our temperate forests and those in the
tropics can fail to be impressed with the difference between them. Not
only for the different plants in them, but for their wholly different
aspect, tropical and temperate forests stand far apart as an expression
of the forest covering the earth. Not all of us realize, however, that
the heat of the tropics is not the deciding factor in the luxuriance of
those dim jungles, and that a rainfall far above anything occurring in
the United States is even more important. Upon the distribution of
rainfall depends the occurrence not only of the two forest types that
will be mentioned here, but of most of the other chief plant societies.

TROPICAL RAIN FOREST

A small section along the lower side of the Gulf of Mexico, the
northeastern edges of Cuba and Santo Domingo, nearly all of the region
drained by the Orinoco and Amazon Rivers; in the Congo, Zanzibar, and
Madagascar in Africa; all of southeastern Asia, including the East
Indies and part of the north coast of Australia--these comprise the
regions of the tropical rain forest. All of them have, besides
continuous heat, a nearly continuous or in some places a periodic
rainfall, averaging over, and usually much over, eighty-five inches a
year, as compared with about half that near New York. There are, of
course, other places in the world where these rain forests, so called
from their abundant moisture and some of the effects of it, are found.
But in the regions mentioned they are at once the most wonderful and to
most white men the most awesome manifestations of the plant world.

Such forests seem, and actually are, pulsating with life, as instruments
stationed in them have many times proved. With some kinds of bamboo
growing over two feet a day, and a eucalyptus tree in Java forty-five
feet in three years--and these are not isolated cases--the tremendous
annual increase in the amount of vegetation can be glimpsed. Of course
not all the plants in them grow at any such rate, but the great heat and
abundant moisture does make tropical rain forests irresistible in their
power. Plantation owners, and railways that have been run through such
forests, wage constant warfare against the recapture by the teeming
forest of man’s intrusion of it. The writer once saw in Santo Domingo a
railway cut through such a jungle and abandoned only two or three years
before. Not a trace of the roadbed could be found, ties, rails, and
switches all covered with a dense vegetation, and overhead the canopy of
the forest had closed over the opening and was already sending down
hundreds of adventitious roots that would complete the obliteration of
man’s handiwork. Everywhere there is the evidence of vegetable life run
riot, ever crowding and pushing to close up openings made by the
crashing down of old trees or the artificial clearings of man. Those
living on the edges of such forests speak and think of them as dim,
mysterious places where strange creatures and the ever-present fevers
join forces with the vegetation to keep out humankind. That they are
places of actual danger everyone knows who recalls that Stanley’s trip
through equatorial Africa cost one hundred and seventy lives, many of
which were sacrificed to disease and strangely enough nine were lost
through starvation. While the tropics supply much of the food used
there, these jungles produce almost none of it and because of the
scarcity of edible fruits, the extraordinary difficulty of getting about
and collecting what does grow, starvation faces anyone who goes into
them without adequate supplies.

In the Amazon grows the largest water lily in the world, _Victoria
regia_, with giant leaves upon which a moderate-sized man may stand in
safety. It produces a flower over a foot in diameter, and it is
surrounded by a forest the like of which it is difficult to describe.
H. H. Rusby, who spent two years in this region hunting for medicinal
plants, has described the country a few hundred miles below where
_Victoria_ was discovered. He writes: “Passing down the river Madeira to
the lower Amazon, we come into a region of such grandeur in its
vegetation that it is difficult of comprehension, even by one who is an
eyewitness. Everything is in such proportion that one is apt in its size
to miss the gigantic. Many of the trees of this region are undoubtedly
many centuries old and appear to be good for many centuries more. Most
of them have enormous buttresses at the base, and these buttresses often
begin as high above the ground as are the tops of ordinary forest trees
in our land. All are bound together with an impenetrable mass of tough
vines. Running through these swamps are the most beautiful little bayous
or canals. Nothing can exceed in interest and delight a day’s canoeing
among these narrow waterways, although there is great danger that the
inexperienced boatman will hopelessly lose his way. In the rainy season
this river rises sixty feet or more above its low water mark and the
boatman travels among the tree tops which a few weeks before were high
above his head.”

The abundant water supply in the rain forests results in an atmosphere
saturated with water vapor and in some of them it is a common sight in
the morning to see the forest rising out of an unbroken blanket of mist.
As this dries up under the heat of the day, or if there occurs one of
the torrential downpours to which such regions are frequently subjected,
there rises from the forest in plainly visible waves a vast quantity of
water vapor. It is this that has so often made them be described as
steaming forests. The water requirements of the plants are more than
supplied, nay, there is such a surfeit of available water in all these
forests, that there are numberless devices to get rid of the excess.
Dripping points to the leaves, already described in an earlier chapter,
are common. But in addition many plants have wonderfully colored leaves
such as Begonias, some relatives of our jack-in-the-pulpit belonging to
the Arum family, many orchids, and other plants. The colored leaves in
the predominantly dark green and gloomy rain forest, because of their
greater absorption of light and consequently higher transpiration rate,
are of decided advantage.

While there is thus very little or in fact almost no struggle for water
in the rain forest, the struggle for light is intense. In the deepest
and most luxuriant of them the gloom of the forest floor is notorious
and it was by no means a figure of speech for Stanley to describe his
trip through equatorial Africa as “Through the Dark Continent.” So dark
are most rain forests, and, as we have seen in a previous chapter, so
inexorable are the plants’ demands for light, that the various devices
to insure it are perhaps the one great difference between these forests
and those of temperate regions. One effect of the struggle for light is
the enormous production of vines often running hundreds of feet through
the tree tops. In India the _Calamus_, or rattan palms, with stems no
thicker than a walking-stick, will completely interlace the foliage of
the canopy. Thousands of slender whiplike roots and stems of such plants
descend from the topmost heights of the forest canopy, where the plants
to which they are attached make such an inextricable tangle among the
tree tops that orchid collectors have been known to travel considerable
distances over the matted vegetation, with, it must be confessed,
considerable danger. These vines or _lianes_ as they are called, are
however, often as thick as a man’s body and armed with great hooked
prickles, an obvious aid in catching some support to reach that
essential light for which all plants in such places are ever striving.

Besides the bewildering tangle caused by these lianes, the rain forest
is further impeded by hosts of epiphytes or plants that are mechanically
attached to tree trunks, branches, or anything else that will raise them
to the light. Of all the plants of such regions the epiphytes are the
most light-demanding. They must not be mistaken for parasites, as they
have roots of their own through which they absorb nourishment, mostly as
water vapor, but also as liquid water held in the bark and refuse in
which they grow. Thousands of orchids are epiphytes, also ferns, and,
only in the American tropics, thousands of different relatives of the
pineapple. Many of the latter are among the most gorgeously colored of
all plants, their superb foliage being much sought after and the
specimens largely grown in our greenhouses. In most rain forests every
available inch of space is covered by these epiphytes, so that no bark,
scarcely any branches, are to be seen but those clothed in this motley
array of plants that use the support to get the utmost possible light.
Many of these epiphytes have rosettes of leaves arranged for holding
water, and after a sharp thunder shower followed by fresh wind the
writer has seen the ground strewn with thousands of relatives of the
pineapple which, with the added supply of water, were unable to stand
the strain and were consequently wrenched from their lofty perch. So
enormous is the combined weight of these epiphytes, together with the
lianes, that many trees crash down under the strain long before their
time. Perhaps no sight of the rain forest so convinces one of the
struggle for light as to see one of these forest monarchs come crashing
down loaded with thousands of plants that have been using it for
support, and to escape which it has pushed its canopy to the utmost
limits of its growth. Such contests are common in a forest of which only
the barest outlines can be conveyed to those who have never seen it. To
those who have had that good fortune any description palls beside the
wonderful actuality.

It is scarcely to be wondered at that these steaming rain forests with
their gloom, and, as they were once described, “all hung about with
fever trees,” should be dreaded by many, and the subject of fabulous
tales to the credulous. The almost incredible difficulty of getting
through them, not to mention the savage animals that inhabit many of
them, have not lessened the tendency to exaggerate about these great
forests. But the truth about them is so far beyond belief, the strange
plants that intrepid explorers have brought out of them so almost
incredible, that it only excited a temporary wonderment when the largest
flower in the world was discovered in such a forest in the Malayan
Archipelago.

Sir Stanford Raffles and Dr. Arnold, while exploring in Sumatra during
the year 1818, discovered what was called “the greatest prodigy of the
vegetable world,” and no flower since found equals its size. The plant,
without stem or leaves, consists wholly of one gigantic flower about
nine feet in circumference, and was subsequently called _Rafflesia
Arnoldii_. It aroused a sensation in England which was not abated by
knowledge of the fact that the flower is a parasite on the stems of
certain tropical plants related to the grape. That such a huge flower
should be the product of a parasitic mode of life is one more
illustration of how this and related irregularities occur in widely
separated families of plants, and under varying conditions. Relatives of
it have since been found in India, some parasitic on roots, others, as
in _Rafflesia Arnoldii_, on the stems of vines. The sticky seeds are in
all probability carried from place to place on the hoofs of elephants,
to which they have been known to cling. Only if they are deposited on a
bruised or otherwise exposed tissue of their future host can they grow.
These curious plants have been actually cultivated in the greatest
tropical botanical garden in the world, at Buitenzorg, Java.

The original collectors of _Rafflesia Arnoldii_ could scarcely credit
their senses when they saw for the first time this extraordinary plant,
whose whole life is spent in producing this great flower and fruit. As
one of them says: “Had I been alone, and had there been no witnesses, I
think I should have been fearful of mentioning the dimensions of this
flower, so much does it exceed every flower I have ever seen or heard
of.” The odor of the flower is repulsive, and, with its great size and
curious mode of growth in the dark rain forest, it is surely one of the
strangest productions of the vegetable world.

But as the utmost development of the plant world, and producing the
greatest profusion and richness of plant life, these rain forests are,
beyond the sporadic occurrence of such wonders as _Rafflesia_ and some
others, places of extraordinary interest. With every inch of space
occupied by plants, the very epiphytes often having on their leaves
still smaller plants, we see here what nature will produce when the
maximum conditions for plant growth are so nearly perfect. Theodore
Roosevelt in his book, “Through the Brazilian Wilderness,” gives a vivid
picture of the rain forest there, and it may well end our account of
those most interesting of all plant societies:

“In one grove the fig trees were killing the palms, just as in Africa
they kill the sandalwood trees. In the gloom of this grove there were no
flowers, no bushes; the air was heavy; the ground was brown with
moldering leaves. Almost every palm was serving as a prop for a fig
tree. The fig trees were in every stage of growth. The youngest ones
merely ran up the palms as vines. In the next state the vine had
thickened and was sending out shoots, wrapping the palm stem in a deadly
hold.

“Some of the shoots were thrown round the stem like the tentacles of an
immense cuttlefish. Others looked like claws that were hooked into every
crevice, and round every projection. In the stage beyond this the palm
had been killed, and its dead carcass appeared between the big, winding
vine trunks; and later the palm had disappeared and the vines had united
in a great fig tree. Water stood in black pools at the foot of the
murdered trees, and of the trees that had murdered them. There was
something sinister and evil in the dark stillness of the grove; it
seemed as if sentient beings had writhed themselves round and were
strangling other sentient beings.”

Many other forests in the tropics, where the rainfall is less, or less
regularly distributed, are not unlike our own, having rather regular
periods of leaf-fall that come with the dry season rather than with the
autumn. The trees are of course never the same as ours, but the general
aspect is not very different from that of temperate forests.

TEMPERATE FORESTS IN AMERICA

The transition from the tropical rain forest to our own woodlands is one
of the most interesting, as it is certainly the most gradual in nature.
Lack of space prevents our stopping to note those strategic points along
this pathway from a hot, steaming forest to the cool shade of our open
woods, where traveling, in at least a virgin forest, may be done easily
on horseback. As we come northward, and if we could travel continuously
through the forest, we should lose first the epiphytes, then most of the
lianes, and finally all the condition of vegetation crowding into every
inch of space suitable for it. While trees in our virgin forests are as
thick as they can be, the forest floor is open and on it grow only a few
herbs that will stand lack of sunshine.

But the really great difference is the long, unfavorable season in
temperate regions where the forest must drop all its leaves, after, in
at least our own Eastern States, the most gorgeous foliage coloring of
any forest in the world. The winter months when the woody vegetation is
practically fully exposed to the elements, are particularly severe in
their effects. Leaf-fall, which is such a common sight as to arouse
scarcely any interest, is the only device by which the great bulk of our
forest trees survive, and only in the southern part of the region are
there found such woody plants as the mountain laurel, rhododendron,
American holly, and a few others which are evergreen but not
cone-bearing ones, and are the only reminders of the truly evergreen
forests of the tropics. The winter winds farther north and in the
central treeless part of the United States prove too much for many kinds
of trees, for instance, all the oaks and sassafras, none of which go
very far north.

There is sufficient rainfall to produce forests much farther north than
they are found, but lower temperatures prevent trees from growing just
as too little water stops their growth altogether. Toward the northern
limits, or upon high mountains, the upper limits of the forest, we get
the best idea of how persistent woody vegetation is in the general
forest area of the eastern United States. Stunted, wind-swept and
weather-beaten trees are often found only a couple of feet high and over
sixty years old. Sometimes they will be flattened out on the ground or
on bare rock, making great patches of bushy growth quite unlike their
lofty relations in the lowlands. The growth rate for such plants is so
slow that their annual rings are all but obscured. With such persistence
in the production of these elfin forests, high up on mountains under the
most unfavorable conditions, it is little wonder that below this are
trackless woods, and that the northeastern United States has one of the
finest developments of the temperate or summer forest in the world.

Nor are all our woods of this general type made up of the same species,
for everyone knows about the endless spruce and fir forests of the
north, exclusively evergreen, and in the summer nearly always moist.
This spruce belt stretches practically across the continent, where, in
the West, other and our most gigantic evergreens, replace the eastern
spruce and fir. A little farther south is the region of the white pine
now nearly unknown as a virgin forest type, as its great value led to
early and ruthless cutting. The white pine region is generally the area
from New England southward along the Alleghenies and westward to
Illinois. But the most characteristic of the temperate forest types is
our summer forest, so called from its general lack of evergreens and its
beautiful green foliage of summer and its bare branches in winter. Beech
and birch and maple, in different proportions according to local
conditions, predominate in such woods. These hard-wooded trees, with
many others that are scattered through them, have been among the most
valuable of all the natural plant products of our country and their
destruction has been upon such a scale that only in a few places may the
virgin forest be seen at the present time. Where it does occur we find
the forest floor often with nothing growing on it except a mass of
spring flowers which are half matured before the leaves of the forest
canopy close out nearly all the light and much water and put them to
rest until another year. The great preponderance of spring-flowering
herbs in Eastern North America is due to their early warming up before
the foliage of the trees cuts off their light. And in some virgin
forests of this sort, particularly where there is a large mixture of
oak, the writer has seen hundreds of square rods without undergrowth or
herbaceous vegetation of any kind. Such places, very rare indeed at the
present time due to senseless and wicked cutting, are rather dark,
perfectly open to view for hundreds of feet ahead, and dotted only with
the huge trunks of the trees that characterize this climax type of the
temperate or summer forest.

The absence of direct sunlight and interception of much rain under the
forest canopy has other effects besides stopping the growth of herbs and
shrubs which are common enough along the edges, or where openings are
made by the fall of old trees. It prevents the germination and growth of
nearly all the seeds falling from such trees, and in a really virgin
forest of this sort, almost no seedlings will be found. Upon cleared or
open land thousands of saplings will cover much of the ground, but
nearly all these will die off due to crowding, and leave as the climax
only enough trees to close over the forest canopy.

Forests may be found in all stages of succession from those just
beginning the process to those final forest monarchs which, having won
out in the race, are, until one of them falls, often slow to perpetuate
the type. For, as often as not, a new growth will spring up once a very
large tree falls, and a very different kind of growth from the climax
forest. At once a host of species, that one might almost say had been
waiting for the tragedy of the monarch’s fall, will rush in and convert
the opening into a nondescript brush patch, out of which will rise
another tree that means business. As it grows to maturity, it kills off
these smaller triflers one by one, until, when the canopy is finally
closed, all of them will have disappeared, or, as often happens,
retreated to other parts of the forest, where they wait for another
chance. This succession of different kinds of growth in a temperate
forest is so well known that in England they have for centuries
practiced it, for commercial or pleasure purposes. In their oak-hazel
copses they cut the trees enough to partly open the canopy, which
permits a dense growth of hazel bushes and other plants. Every twelve or
fifteen years the latter are cut down for various purposes, and will
gradually spring up again to renew the dense growth. The spacing of the
trees is sufficient for them to branch freely and yet not close the
canopy enough to kill off the hazel. The trees are cut off a few at a
time, not oftener than one or two hundred years in any one spot. By this
procedure the owner gets a regular crop of hazel once in twelve or
fifteen years, occasional big trees, and on many places a cover for
pheasants. Under the hazel there is a regular progression of herbs, very
plentiful just after the bushes are cut, and decreasing almost to
nothing when the end of the growth period of the bushes is near.

The English oak-hazel copse, now much less grown than formerly, and the
general lack of undergrowth in our own virgin forests, are both
responses of the forest to light and other factors that are related to
an open or closed canopy. As we stated a page or two back, it is not
impossible, it is even frequent in some parts of the country, for a
forest to produce, by its own growth, conditions inimical to its
perpetuation. Where the casual falling of a forest giant is the only
opportunity which that forest offers to perpetuate its type, it may well
be said to be a climax forest, incapable of further development. But in
some such woods a curious provision of nature insures an invasion of the
gloomy forests by trees less light-demanding than the dominant ones. And
often these trees that can get along with less light will capture
considerable parts of forests that light-demanding trees could never
conquer.

If the soil in which these temperate forests happen to grow is sandy or
otherwise poor in plant food, the broad-leaved trees that make our woods
such a delight in summer are replaced almost universally by pines. Along
the sandy stretches of the coastal plain from Long Island, New York, to
the Gulf, there are immense tracts of these pine forests, different
species often being locally dominant, such as the pitch pine in the pine
barrens of New Jersey and the long-leaf pine farther south. Almost
throughout the world there is this monopolization of the poorer and
drier forest sites by pines, which maintain the forest plant society in
regions where the broad-leaved rapidly transpiring trees could not grow.

No account of forests, however brief, can omit some mention of the
greatest agency for their protection in North America, the United States
Forest Service. With corporation and individual cutting and attendant
fire hazard upon a scale almost beyond belief in its ruthless disregard
of our chief natural plant product, the Government soon found that
Federal ownership or control of forests was the only policy that would
maintain even a partially adequate timber supply. National forests, set
aside either for pleasure or profit, now total more than the area of
France or than all the New England and most of the Middle Atlantic
States. These huge tracts, in every part of the country where forests
are found, are well managed, properly planted, and most important of
all, constantly guarded against fire. Forest fires not only destroyed
over $25,000,000 worth of timber annually, but leaving devastation
behind them, depleted the water supply in many parts of the country.
Nothing but forests will hold the rainfall, to release it slowly
through a thousand rivulets and springs that are the source of countless
rivers. With the forest cut or burned off these streams are dry most of
the summer and raging torrents for a few weeks in the spring, washing
out all the priceless accumulation of the ages which the forest has
conserved for its own and our benefit. While the reservation of these
great national forests has worked individual hardship, experience for
many years back in India and Germany shows Federal ownership or control
the only wise policy.

Forest covering, whether temperate or tropical, depends for its
occurrence all over the world upon an adequate rainfall. As we have seen
in the tropics, this may be so great that coupled with the heat it
produces a wealth of vegetation beyond the powers of description. Where
it is less and the country cooler, the forests are of a different type,
but even there the forest covering is, without interference, practically
complete. Where, as in parts of Chile, southeastern Australia, and of
Japan, there is a heavy rainfall but cool climate, there is a so-called
temperate rain forest. Such forests are cold, drab, wet woods of
peculiar aspect and extreme interest. For in them grow trees sometimes
related to our own, but, due to the special conditions, producing a
forest landscape quite unlike anything in America. It would seem as if
we might almost plot the distribution of forests in our own country with
a weather map showing rainfall, and such is actually the case. When the
rainfall becomes less than will maintain forest growth it stops, often
very abruptly. Generally speaking, the region west of the Mississippi,
and some just east of it, westward to the mountains, is entirely devoid
of forest, except in the river valleys. The forests give place to an
entirely different type of vegetation--the prairie or grassland.

THE PRAIRIE OR GRASSLANDS

In nearly every region in the world there is an absence of forests and a
replacement of them by grasslands, where the rainfall is less than about
twenty-five inches a year, and where the winter winds, often far below
the freezing point, are hostile to trees. The distribution of the rain
mostly through the growing season also makes a condition peculiarly
unfavorable for trees during the winter. Someone has said that the
nations have fought since the days of the Romans for the belt of
grassland which these climatic conditions have produced all round the
world, and it is certainly true that these naturally grass-covered areas
have produced the cereals of the world, all of which, except rice, grow
to best advantage in such regions.

With of course different species of grass and quite different associated
herbs, these grasslands are now found in our own prairies, the steppes
of Russia, the plains of Hungary, the pampas of southern South America,
the grasslands of Australia, the veld in Natal and in many other but
mostly less extensive developments. Some of the grassland regions are
warm, but without more rainfall than characterizes such areas the
greater heat does not produce a forest. Usually, but not always, these
grasslands are not found near the coast, where, as in America, the
rainfall is double that of the plains and produces the forests that
clothe the Atlantic and Pacific sections of the country. From the east
westward there is a gradual decrease in the rainfall, until from about
the Mississippi to the mountains it falls below the point where trees
can compete with the prairie.

Another characteristic of prairies that once they have started tends to
keep out trees is their almost annual firing. Tree seedlings cannot
survive this, and we know that the Indians fired huge tracts of prairie
every year, not to mention fires started by lightning which may set fire
to grasslands and actually does set fire to forests every year.

The prairies in the United States--perhaps the most extensive in the
world--are characterized chiefly by several grasses, buffalo grass
(_Buchloë dactyloides_), gama grass (_Bouletoua oligostachya_), and
several prairie grasses, such as _Sporobolus asperifolius_, _Koeleria
cristata_, and some others. Among these, depending on the soil, are
hundreds of prairie flowers which, during different parts of a single
season, give quite different aspects to the region. Both the grasses and
their associated herbs are well protected against too violent
transpiration which their exposure to nearly continuous sunshine, high
summer heat, and very considerable winds makes particularly active. In
many places where the country is rolling, the lower and moister sites,
besides developing more luxuriant growth of prairie plants, permits low
shrubs, and in river bottoms even trees to flourish. But climatic
conditions of small rainfall, high winds, and bitter winters make
anything like a forest development out of the question.

In some regions, both in America and central Europe, a rainfall that is
high enough to permit trees to exist and low enough to favor at the same
time a grassland formation has resulted in the parklike landscape that
creates the most beautiful scenic features of the regions where it
occurs. In such places there are irregular patches of forest and
grassland, and the struggle for supremacy as between the different types
depends, not upon the general climatic conditions to which they both
respond, but to local conditions of available water supply and soil
conditions and often upon fires. Naturally such regions are places of
intense strife for dominance, and in them some remarkable collections of
plants have been found.

One of the most interesting of these struggles between grassland and
woody vegetation in a region climatically able to produce both, is in
Natal. Large sections of that country are grasslands or veld, as the
people there call it. Scattered through the veld are various species of
acacia trees, locally called thorn, with feathery compound leaves. These
do not shut out enough light to prevent the development of grasses
directly under their shade, yet the annual firing of the veld prevents,
except accidentally, the production of the acacias. But the seeds of
this tree, whether from long usage to this burning or not, are actually
hastened in their germination by the firing, and it is a common practice
in that country to roast or partly boil the seeds of the tree to hasten
germination. The presence of the climatically favorable environment for
both trees and grassland results in the latter being the dominant type
of vegetation over large tracts of the country, largely because fires
destroy tree seedlings, and yet the tree seeds, by a quite extraordinary
fitness for their peculiar environment, offer a measure of insurance
against the total destruction of woody vegetation by the grassland.

The pampas of the Argentine have been vividly described by P. G.
Lorentz, who, in writing of the drier parts of it, says: “Viewed from a
distance, these grasses seem to form a close grassy covering, and the
pampa presents the appearance of extensive grassy tracts whose coloring
varies with the seasons: coal black in the spring, when the old grass
has been burned; bright green, the color of the mature grass;
finally--at flowering time--when the silvery white spikes overtop the
grass, over wide tracts it seems like a rolling, waving sea of liquid
silver.

“After the Gramineæ (grasses), the family of plants that is represented
in the pampas by the greatest number of individuals is that of Compositæ
(daisy family); usually twiggy undershrubs with inconspicuous flowers, a
bright yellow _Solidago_ (golden-rod) alone gleams out from among the
others.”

Here, as in the other grasslands of the world, if a local water supply
above the general requirements of the grass exists, there is always a
small element of woody plants, low, thick-leaved shrubs usually, but
where water is more plentiful, trees, as in the region in Natal, already
mentioned, and in many other parts of the world, notably parts of
Australia, China, Brazil, and many sections of the western part of the
United States.

We see in grasslands a plant response to rainfall and other climatic
conditions which, with a little more rainfall, or in locally wet places,
always produces woody growth, either as tongues of woods in river
bottoms or the parklike landscape, already mentioned. If, however, the
rainfall is too low to produce even the grasses and their associated
herbs, an entirely different type of vegetation usurps these still more
dry regions, resulting in some of those strange plants of the deserts,
among which water storage is practically universal, as is the ability to
live for long periods without rainfall.

DESERTS

Of absolute deserts there are none in North America, for no part of it
is so dry that plants of some sort do not grow, and in fact in hardly
any part of the world are there regions of any considerable extent where
plant life of any kind is lacking. There is a small section of northern
Chile and adjacent regions on the western slopes of the Andes where
nothing grows, and the traveler is met with a cheerless landscape of
bare ground and sandy or stony soil. There is no record of it ever
having rained in such places, and if there be only a single rain
consisting of a fraction of an inch a year, a few plants, usually
scraggly low herbs with thick leaves or else quick-flowering annuals
will be found.

But there are hundreds of thousands of square miles of the earth’s
surface where the rainfall is sufficient to produce plant life, but
where it hardly exceeds five or at most six inches in a year, and in
some regions is less than two inches. From several different stations in
the desert area of our own Southwest the average annual rainfall is
about five and a half inches. Such regions produce a desert type of
vegetation and are popularly, if not properly, called deserts. The
largest is of course the Sahara in Africa, but there are huge tracts in
Arabia, China, Thibet, Australia, South Africa, and in some other
countries where the conditions for plant life are so unfavorable that
only in the better sites are plants found at all. In all deserts there
are very large areas entirely without plants, due to shifting sand or
other local conditions, which, added to the generally unfavorable
climate, make plant life impossible.

With rainfall so low and in most of the regions the temperature so high,
the vegetation must be insured against too rapid transpiration. Perhaps
the best illustration of how high transpiration both in plants and in
man may be in such regions is gained by a statement of D. T. MacDougal,
who writes of man traveling in the desert that “the amount (of water)
thrown off the skin is correspondingly great, and if the loss is not
made good, thirst ensues and ten hours’ lack of water may thicken the
tongue so that speech is impossible.”

Under such conditions it is not surprising that desert plants are among
the most curious and weird members of the plant world. Every device both
to retard transpiration and to store up water to last over a completely
rainless period, may be found. In America, to which all the hundreds of
different species of cactus are practically confined, we find giant
forms, often covered with spines and prickles which prevent their
destruction by cattle, and many others that hug the dry sandy soil with
curious tortuous branches. None of them have leaves such as plants of
the forest or grassland possess, for desert plants cannot afford the
luxury of foliage that, because of too rapid water loss, would destroy
their chance to survive. Cacti do produce tiny leaves at the ends of
their joints, but as if recognizing the inhospitable world into which
they are born, practically all of them drop off, so that for the great
bulk of the life of most cacti only the bare branches are evident. In
most kinds these branches are green, assume the functions of leaves,
such as transpiration and the manufacture of food by photosynthesis.

While in cacti and in the giant cactuslike spurges of South Africa the
ability to store water is tremendously developed--our giant cereus or
saguaro often holding 125 gallons--most desert plants rely upon
retarding transpiration for their existence. Leafless shrubs and trees
whose often spiny branches are green and perform, on a much-reduced
scale, the function of leaves, are among the most common characteristics
of desert plants. Some, as _Parkinsonia microphylla_ or paloverde, have
tiny leaves which they put out during the spring showers, but quickly
lose them as it gets hotter and drier toward midsummer. Many of the
plants that do produce leaves regularly have the surface of them so
shiny as to appear varnished, or so thickly coated with hairs as to
simulate cotton or wool, both of which reduce transpiration. There are
many plants, some of which do not even live in a desert but in a locally
dry habitat, that also have the utmost development of structure to
prevent transpiration. One of the most extraordinary is the vegetable
sheep in New Zealand. An inhabitant of dry rocky places, its water
supply, although rainfall is fairly abundant, is precarious due to
drainage and the failure of the rock to prevent run-off. The different
species of _Raoulia_, of which _R. eximia_ is one of the best known, are
admirably adapted to exist under such conditions. L. Cockayne, an
authority on the flora of that island, writes of these strange plants:
“Perhaps the most striking denizens of rocks are the various kinds of
vegetable sheep (species of _Raoulia_), which form hard cushions, mostly
white, but occasionally green--and of enormous size. The raoulia
cushions are all constructed on the same plan. Above, the stems branch
again and again, and toward their extremities are covered with small
woolly leaves, packed as tightly as possible. Finally stems, leaves, and
all are pressed into a dense hard convex mass, making, in the case of
_Raoulia eximia_, an excellent and appropriate seat for a tired
botanist. Within the plant is a peat made of rotting leaves and
branches, which holds water like a sponge, and into which the final
branchlets send roots. Thus the plant lives in great measure on its own
decay, and the woody main root serves chiefly as an anchor. The
vegetable sheep are not inaptly named, for at a distance a shepherd
might be misled.” The genus _Raoulia_ belongs to the daisy family, and
furnishes another illustration of the remarkable diversity of this
largest and probably most recent of the families of flowering plants,
which appears to have originated in the Andes and now covers the world.

In Damaraland, Southwest Africa, the most remarkable desert plant was
discovered years ago, growing in a sandy and stony plain where the
rainfall for fourteen years has not averaged more than two and a quarter
inches annually. There are sea fogs, however, upon the condensation of
which upon sheets of glass the discoverers of _Welwitschia mirabilis_
relied for some of their scanty water supply. The plant, whose woody
stem is deep buried in the ground with only the top appearing above the
surface, looks not unlike “the burnt crust of a loaf of bread.” To this
only two large leaves are attached. These are many feet long and split
into several sections which undulate over the ground very like the
tentacles of an octopus. With such strange products of the desert
scattered over the plains it is little wonder that _Welwitschia_ caused
a sensation only equaled by the discovery of _Rafflesia_ in the rain
forest of Sumatra.

While deserts seem to be the most unfavorable places in which plants can
exist, and their very existence in many deserts is often a precarious
affair, it should be kept in mind that the soil of such places is often
by no means sterile. As we found in the section of this book on “How
Plants Get Their Food,” water is absolutely necessary for the absorption
of food through the root hairs. Where, as in an oasis in the desert,
water is locally plentiful a luxuriant vegetation springs up, and one of
the most fertile parts of our Southwest was transformed from a desert by
irrigation. Then, too, in many deserts there is a pronounced rainy
season during which there is a marvelous development of showy flowering
herbs that die down as rain ceases or becomes too slight, to wait for
another opportunity to make the desert blossom into often gorgeous
coloring.

Rain forests, temperate forests, grassland, and deserts--all are immense
developments of plant societies depending upon climatic differences for
their occurrence. There are some other plant communities which also
depend for their development on still other differences of climate. Two
such are the vegetation of mountain tops in the tropics, and that
strange tundra vegetation near the poles which lives all its life on the
ice, only the roots and soil in which it grows thawing out during the
brief summer. Temperature rather than rainfall is the cause of these and
some other plant societies of more local occurrence.

But what of such well-known plant societies as bogs, in which peat is
formed, or the plants growing along the sea beaches all over the world?
These, and scores of other plant communities play their part in the
distribution of plants, but nearly all of them depend not upon climate,
but upon usually purely local conditions of soil. Sandy, actually nearly
sterile soil, the acidity of cranberry bogs, the alkaline regions in our
own West, the salt lakes and inland seas, regions below sea level, the
serpentine outcrops, all the hundred and one differences which local
conditions exhibit--all these have a very direct bearing upon plant
distribution. It is impossible here to go into the details of the
different sorts of plant societies which inhabit such specialized
places, nor into the truly wonderful adaptations of certain species to
peculiar conditions. But in looking at the vegetation of regions through
which one travels it must never be forgotten that its general type, such
as forest, or grassland, or desert, or what not, is the result of
usually widely operating climatic forces, while many, often quite
extensive, plant societies in the region are the result of the local
environment. There is often an active struggle as to the dominance of
the type dictated by the climate of the place, and the local conditions
of soil that tend to nullify general response to it. On Long Island, New
York, for instance, there are areas which climatically should produce
dense woods of the summer forest type so general all through the
Northeastern States. Actually the water-worn sands and gravels that
covered the south side of the island in glacial times, are so poor in
plant food, that many square miles of this region are now covered only
by low scrub oaks and other plants suited to poor soils.

A final word of caution is necessary to those who see in the foregoing
brief account of some of the chief causes of plant distribution an
answer to questions that many of us ask about why plants or vegetation
are of such and such a kind in a particular locality. It has been
convenient--nay, it has been necessary--to consider these various
factors one by one, but the distribution of almost no individual, and
certainly of no widely spread plant community, is the result of any one
of these factors operating singly.

The geological history of the region, the links with the past of the
species composing the vegetation, the climate, the cooperation of
various outside agencies in seed dispersal, the conflict of different
species, and of different vegetation types, these and scores of other
factors, operating to-day, or having operated in the past--it is all
these that are reflected in the plant covering of the earth. The variety
and beauty of that covering are too well understood to need further
mention here. The extraordinary efforts that the plant world makes to
keep all but a minute fraction of the earth clothed with some sort of
vegetation we have seen in the pages just turned. No other phase of the
study of plant life is so replete with interest as plant distribution.
Rightly understood, it is a study, “the cultural, esthetic and practical
value of which may well outweigh any other.”

GENERAL CONCLUSION

We have now traced, all too briefly and with the many omissions that
such a general account as this makes necessary, the broad outlines of
plant life. From the architecture of their outer characteristics, which
takes up the first chapter, we have gone step by step into the story of
what goes on within the plant, and how it reproduces its kind. These
actions or behavior of plants have resulted in many things of great
practical importance as well as being of absorbing interest in
themselves. What some of these results have been, we see reflected in
the uses of plants to man, in the history of their development, and,
most of all, in the way they are distributed over the earth to-day.

If plants are still “just plants” to most readers, this book has been
written in vain. Those who have gleaned from its pages some conception
of what a fundamental thing plant life is, will doubtless want more
information than could be included here.

If any considerable proportion of the readers of this volume feel that
they have already outgrown it, and that they have many questions about
the plant world for which they will have to go to more specialized works
for the answer, then this book has more than fulfilled its mission.

FOOTNOTES:

[1] After living probably as long as the Big Trees of California, the
most famous dragon tree in the world was destroyed by a great storm.
It has been replaced by seedlings.

[2] A process recently discovered in England for extracting the fiber
of this rush by a chemical bath has greatly increased the fiber
possibilities of this common rush. Heretofore it has been used only
for coarse weaving of rugs and mattings in Japan. By the new process
a fine fiber capable of spinning is extracted that may eventually
compete with jute.

[3] Copyright, 1912. Doubleday, Page & Company.

[4] The term “indifferent” in this connection is used to signify that
the plant will adapt itself to average conditions.

[5] Plants marked thus belong to the heath family and require special
conditions as indicated in text.

*** End of this LibraryBlog Digital Book "Botany - The Science of Plant Life" ***

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