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GRAY'S LESSONS IN BOTANY

REVISED EDITION




THE
ELEMENTS OF BOTANY

FOR BEGINNERS AND FOR SCHOOLS


By ASA GRAY




IVISON, BLAKEMAN, AND COMPANY
NEW YORK AND CHICAGO




_Copyright_,
By Asa Gray.
1887.




PREFACE.


This volume takes the place of the author's Lessons in Botany and
Vegetable Physiology, published over a quarter of a century ago. It is
constructed on the same lines, and is a kind of new and much revised
edition of that successful work. While in some respects more extended,
it is also more concise and terse than its predecessor. This should the
better fit it for its purpose now that competent teachers are common.
They may in many cases develop paragraphs into lectures, and fully
illustrate points which are barely, but it is hoped clearly, stated.
Indeed, even for those without a teacher, it may be that a condensed is
better than a diffuse exposition.

The book is adapted to the higher schools, "How Plants Grow and Behave"
being the "Botany for Young People and Common Schools." It is intended
to ground beginners in Structural Botany and the principles of vegetable
life, mainly as concerns Flowering or Phanerogamous plants, with which
botanical instruction should always begin; also to be a companion and
interpreter to the Manuals and Floras by which the student threads his
flowery way to a clear knowledge of the surrounding vegetable creation.
Such a book, like a grammar, must needs abound in technical words, which
thus arrayed may seem formidable; nevertheless, if rightly apprehended,
this treatise should teach that the study of botany is not the learning
of names and terms, but the acquisition of knowledge and ideas. No
effort should be made to commit technical terms to memory. Any term used
in describing a plant or explaining its structure can be looked up when
it is wanted, and that should suffice. On the other hand, plans of
structure, types, adaptations, and modifications, once understood, are
not readily forgotten; and they give meaning and interest to the
technical terms used in explaining them.

In these "Elements" naturally no mention has been made of certain terms
and names which recent cryptogamically-minded botanists, with lack of
proportion and just perspective, are endeavoring to introduce into
phanerogamous botany, and which are not needed nor appropriate, even in
more advanced works, for the adequate recognition of the ascertained
analogies and homologies.

As this volume will be the grammar and dictionary to more than one or
two Manuals, Floras, etc., the particular directions for procedure which
were given in the "First Lessons" are now relegated to those works
themselves, which in their new editions will provide the requisite
explanations. On the other hand, in view of such extended use, the
Glossary at the end of this book has been considerably enlarged. It will
be found to include not merely the common terms of botanical description
but also many which are unusual or obsolete; yet any of them may now and
then be encountered. Moreover, no small number of the Latin and Greek
words which form the whole or part of the commoner specific names are
added to this Glossary, some in an Anglicized, others in their Latin
form. This may be helpful to students with small Latin and less Greek,
in catching the meaning of a botanical name or term.

The illustrations in this volume are largely increased in number. They
are mostly from the hand of Isaac Sprague.

It happens that the title chosen for this book is that of the author's
earliest publication, in the year 1836, of which copies are rarely seen;
so that no inconvenience is likely to arise from the present use of the
name.

                              ASA GRAY.

                              Cambridge, Massachusetts,
                              _March, 1887_.




CONTENTS.


                                                                  Page
SECTION I. INTRODUCTORY                                              9


SECTION II. FLAX AS A PATTERN PLANT                                 11

  Growth from the Seed, Organs of Vegetation                        11
  Blossoming, Flower, &c.                                           14


SECTION III. MORPHOLOGY OF SEEDLINGS                                15

  Germinating Maples                                                15
  Cotyledons thickened, hypogaeous in germination                    18
  Store of Food external to the Embryo                              20
  Cotyledons as to number                                           22
  Dicotyledonous and Polycotyledonous                               23
  Monocotyledonous                                                  24
  Simple-stemmed Plants                                             26


SECTION IV. GROWTH FROM BUDS; BRANCHING                             27

  Buds, situation and kinds                                         27
  Vigorous vegetation from strong Buds                              28
  Arrangement of Branches                                           29
  Non-developed, Latent, and Accessory Buds                         30
  Enumeration of kinds of Buds                                      31
  Definite and Indefinite growth; Deliquescent and Excurrent        31


SECTION V. ROOTS                                                    33

  Primary and Secondary. Contrast between Stem and Root             34
  Fibrous and Fleshy Roots; names of kinds                          34
  Anomalous Roots. Epiphytic and Parasitic Plants                   36
  Duration: Annuals, Biennials, Perennials                          37


SECTION VI. STEMS                                                   38

  Those above Ground: kinds and modifications                       39
  Subterranean Stems and Branches                                   42
  Rootstock                                                         42
  Tuber                                                             44
  Corm                                                              45
  Bulb and Bulblets                                                 46
  Consolidated Vegetation                                           47


SECTION VII. LEAVES                                                 49

  Sec. 1. LEAVES AS FOLIAGE                                         49

    Parts and Venation                                              50
    Forms as to general outline                                     52
    As to apex and particular outline                               53
    As to lobing or division                                        56
    Compound, Perfoliate, and Equitant Leaves                       57
    With no distinction of Petiole and Blade, Phyllodia, &c.        61

  Sec. 2. LEAVES OF SPECIAL CONFORMATION AND USE                    62

    Leaves for storage                                              62
    Leaves as bud-scales                                            63
      Spines                                                        64
      and for Climbing                                              64
    Pitchers                                                        64
      and Fly-traps                                                 65

  Sec. 3. STIPULES                                                  66

  Sec. 4. THE ARRANGEMENT OF LEAVES                                 67

    Phyllotaxy                                                      67
    Of Alternate Leaves                                             69
    Of Opposite and Whorled Leaves                                  71
    Vernation or Praefoliation                                      71


SECTION VIII. FLOWERS                                               72

  Sec. 1. POSITION AND ARRANGEMENT, INFLORESCENCE                   73

    Raceme                                                          73
    Corymb, Umbel, Spike, Head                                      74
    Spadix, Catkin, or Ament                                        75
    Panicle: Determinate Inflorescence                              76
    Cyme, Fascicle, Glomerule, Scorpioid or Helicoid Cymes          77
    Mixed Inflorescence                                             78

  Sec. 2. PARTS OR ORGANS OF THE FLOWER                             79

    Floral Envelopes: Perianth, Calyx, Corolla                      79
    Essential Organs: Stamen, Pistil                                80
    Torus or Receptacle                                             81

  Sec. 3. PLAN OF THE FLOWER                                        81

    When perfect, complete, regular, or symmetrical                 81
    Numerical Plan and Alternation of Organs                        82
    Flowers are altered branches                                    83

  Sec. 4. MODIFICATIONS OF THE TYPE                                 85

    Unisexual or diclinous                                          85
    Incomplete, Irregular, and Unsymmetrical                        86
    Flowers with Multiplication of Parts                            88
    Flowers with Union of Parts: Coalescence                        88
    Regular Forms                                                   89
    Irregular Forms                                                 90
    Papilionaceous                                                  91
      Labiate                                                       92
      and Ligulate Corollas                                         93
    Adnation or Consolidation                                       94
    Position of Flower or of its Parts                              96

  Sec. 5. ARRANGEMENT OF PARTS IN THE BUD                           97

    AEstivation or Praefloration, its kinds                         97


SECTION IX. STAMENS IN PARTICULAR                                   98

  Androecium                                                        98
    Insertion, Relation, &c.                                        99
  Anther and Filament. Pollen                                      101


SECTION X. PISTILS IN PARTICULAR                                   105

  Sec. 1. ANGIOSPERMOUS OR ORDINARY GYNOECIUM                      105

    Parts of a complete Pistil                                     105
    Carpels, Simple Pistil                                         106
    Compound Pistil with Cells and Axile Placentae                 107
    One-celled with Free Central Placenta                          108
    One-celled with Parietal Placentae                             108

  Sec. 2. GYMNOSPERMOUS GYNOECIUM                                  109


SECTION XI. OVULES                                                 110

  Their Parts, Insertion, and Kinds                                111


SECTION XII. MODIFICATIONS OF THE RECEPTACLE                       112

  Torus, Stipe, Carpophore, Disk                                   113


SECTION XIII. FERTILIZATION                                        114

  Sec. 1. ADAPTATIONS FOR POLLINATION OF THE STIGMA                114

    Close and Cross Fertilization, Anemophilous and Entomophilous  115
    Dichogamy and Heterogony                                       116

  Sec. 2. ACTION OF THE POLLEN AND FORMATION OF THE EMBRYO         117


SECTION XIV. THE FRUIT                                             117

  Nature and kinds                                                 118
  Berry, Pepo, Pome                                                119
  Drupe and Akene                                                  120
  Cremocarp, Caryopsis, Nut                                        121
  Follicle, Legume, Capsule                                        122
  Capsular Dehiscence, Silique and Silicle                         123
  Pyxis, Strobile or Cone                                          124


SECTION XV. THE SEED                                               125

  Seed-coats and their appendages                                  125
  The Kernel or Nucleus, Embryo and its parts, Albumen             127


SECTION XVI. VEGETABLE LIFE AND WORK                               128

  Sec. 1. ANATOMICAL STRUCTURE AND GROWTH                          129

    Nature of Growth, Protoplasm                                   129
    Cells and Cell-walls. Cellular Structure or Tissue             130
    Strengthening Cells. Wood, Wood-cells, Vessels or Ducts        132

  Sec. 2. CELL-CONTENTS                                            136

    Sap, Chlorophyll, Starch                                       136
    Crystals, Rhaphides                                            137

  Sec. 3. ANATOMY OF ROOTS AND STEMS                               138

    Endogenous and Exogenous Stems                                 139
    Particular structure of the latter                             140
    Wood, Sapwood and Heart-wood. The living parts of a Tree       141

  Sec. 4. ANATOMY OF LEAVES                                        142

    Epidermis, Stomata or Breathing pores                          143

  Sec. 5. PLANT FOOD AND ASSIMILATION                              144

  Sec. 6. PLANT WORK AND MOVEMENT                                  149

    Movements in Cells or Cyclosis                                 149
    Transference from Cell to Cell                                 150
    Movements of Organs, Twining Stems, Leaf-movements             150
    Movements of Tendrils, Sensitiveness                           152
    Movements in Flowers                                           153
    Movements for capture of Insects                               154
    Work costs, using up Material and Energy                       155


SECTION XVII. CRYPTOGAMOUS OR FLOWERLESS PLANTS                    156

  Vascular Cryptogams, Pteridophytes                               156
  Horsetails (Equisetaceae), Ferns                                 157
  Club-Mosses (Lycopodium), &c.                                    161
  Quillworts (Isoetes), Pillworts (Marsilia)                       161
  Azolla. Cellular Cryptogams                                      162
  Bryophytes. Mosses (Musci)                                       163
  Liverworts (Hepaticae)                                           164
  Thallophytes                                                     165
  Characeae                                                        167
  Algae, Seaweeds, &c.                                             168
  Lichenes or Lichens                                              171
  Fungi                                                            172


SECTION XVIII. CLASSIFICATION AND NOMENCLATURE                     175

  Sec. 1. KINDS AND RELATIONSHIP                                   175

    Species, Varieties, Individuals                                176
    Genera, Orders, Classes, &c.                                   177

  Sec. 2. NAMES, TERMS AND CHARACTERS                              178

    Nomenclature of Genera, Species, and Varieties                 179
    Nomenclature of Orders, Classes, &c. Terminology               180

  Sec. 3. SYSTEM                                                   181

    Artificial and Natural                                         182
    Synopsis of Series, Classes, &c.                               183


SECTION XIX. BOTANICAL WORK                                        184

  Sec. 1. COLLECTION OR HERBORIZATION                              184

  Sec. 2. HERBARIUM                                                186

  Sec. 3. INVESTIGATION AND DETERMINATION OF PLANTS                187

  Sec. 4. SIGNS AND ABBREVIATIONS                                  188


ABBREVIATIONS OF THE NAMES OF BOTANISTS                            190


GLOSSARY COMBINED WITH INDEX                                       193




ELEMENTS OF BOTANY.




Section I. INTRODUCTORY.


1. BOTANY is the name of the science of the vegetable kingdom in
general; that is, of plants.

2. Plants may be studied as to their kinds and relationships. This study
is SYSTEMATIC BOTANY. An enumeration of the kinds of vegetables, as far
as known, classified according to their various degrees of resemblance
or difference, constitutes a general _System of plants_. A similar
account of the vegetables of any particular country or district is
called a _Flora_.

3. Plants may be studied as to their structure and parts. This is
STRUCTURAL BOTANY, or ORGANOGRAPHY. The study of the organs or parts of
plants in regard to the different forms and different uses which the
same kind of organ may assume,--the comparison, for instance, of a
flower-leaf or a bud-scale with a common leaf,--is VEGETABLE MORPHOLOGY,
or MORPHOLOGICAL BOTANY. The study of the minute structure of the parts,
to learn by the microscope what they themselves are formed of, is
VEGETABLE ANATOMY, or HISTOLOGY; in other words, it is Microscopical
Structural Botany. The study of the actions of plants or of their parts,
of the ways in which a plant lives, grows, and acts, is the province of
PHYSIOLOGICAL BOTANY, or VEGETABLE PHYSIOLOGY.

4. This book is to teach the outlines of Structural Botany and of the
simpler parts of the physiology of plants, that it may be known how
plants are constructed and adapted to their surroundings, and how they
live, move, propagate, and have their being in an existence no less
real, although more simple, than that of the animal creation which they
support. Particularly, this book is to teach the principles of the
structure and relationships of plants, the nature and names of their
parts and their modifications, and so to prepare for the study of
Systematic Botany; in which the learner may ascertain the name and the
place in the system of any or all of the ordinary plants within reach,
whether wild or cultivated. And in ascertaining the name of any plant,
the student, if rightly taught, will come to know all about its general
or particular structure, rank, and relationship to other plants.

5. The vegetable kingdom is so vast and various, and the difference is
so wide between ordinary trees, shrubs, and herbs on the one hand, and
mosses, moulds, and such like on the other, that it is hardly possible
to frame an intelligible account of plants as a whole without
contradictions or misstatements, or endless and troublesome
qualifications. If we say that plants come from seeds, bear flowers, and
have roots, stems, and leaves, this is not true of the lower orders. It
is best for the beginner, therefore, to treat of the higher orders of
plants by themselves, without particular reference to the lower.

6. Let it be understood, accordingly, that there is a higher and a lower
series of plants; namely:--

PHANEROGAMOUS PLANTS, which come from seed and bear _flowers_,
essentially stamens and pistils, through the co-operation of which seed
is produced. For shortness, these are commonly called PHANEROGAMS, or
_Phaenogams_, or by the equivalent English name of FLOWERING PLANTS.[1]

CRYPTOGAMOUS PLANTS, or CRYPTOGAMS, come from minute bodies, which
answer to seeds, but are of much simpler structure, and such plants have
not stamens and pistils. Therefore they are called in English FLOWERLESS
PLANTS. Such are Ferns, Mosses, Algae or Seaweeds, Fungi, etc. These
sorts have each to be studied separately, for each class or order has a
plan of its own.

7. But Phanerogamous, or Flowering, Plants are all constructed on one
plan, or _type_. That is, taking almost any ordinary herb, shrub, or
tree for a pattern, it will exemplify the whole series: the parts of one
plant answer to the parts of any other, with only certain differences in
particulars. And the occupation and the delight of the scientific
botanist is in tracing out this common plan, in detecting the likenesses
under all the diversities, and in noting the meaning of these manifold
diversities. So the attentive study of any one plant, from its growth
out of the seed to the flowering and fruiting state and the production
of seed like to that from which the plant grew, would not only give a
correct general idea of the structure, growth, and characteristics of
Flowering Plants in general, but also serve as a pattern or standard of
comparison. Some plants will serve this purpose of a pattern much better
than others. A proper pattern will be one that is perfect in the sense
of having all the principal parts of a phanerogamous plant, and simple
and regular in having these parts free from complications or disguises.
The common Flax-plant may very well serve this purpose. Being an annual,
it has the advantage of being easily raised and carried in a short time
through its circle of existence, from seedling to fruit and seed.


FOOTNOTES:

[1] The name is sometimes _Phanerogamous_, sometimes _Phaenogamous_
(_Phanerogams_, or _Phaenogams_), terms of the same meaning
etymologically; the former of preferable form, but the latter shorter.
The meaning of such terms is explained in the Glossary.




Section II. FLAX AS A PATTERN PLANT.


8. =Growth from the Seed.= Phanerogamous plants grow from seed, and
their flowers are destined to the production of seeds. A seed has a
rudimentary plant ready formed in it,--sometimes with the two most
essential parts, i. e. stem and leaf, plainly discernible; sometimes
with no obvious distinction of organs until germination begins. This
incipient plant is called an EMBRYO.

9. In this section the Flax-plant is taken as a specimen, or type, and
the development and history of common plants in general is illustrated
by it. In flax-seed the embryo nearly fills the coats, but not quite.
There is a small deposit of nourishment between the seed-coat and the
embryo: this may for the present be left out of the account. This embryo
consists of a pair of leaves, pressed together face to face, and
attached to an extremely short stem. (Fig. 2-4.) In this rudimentary
condition the real nature of the parts is not at once apparent; but when
the seed grows they promptly reveal their character,--as the
accompanying figures (Fig. 5-7) show.

[Illustration: Fig. 1. Pod of Flax. 2. Section lengthwise, showing two
of the seeds; one whole, the other cut half away, bringing contained
embryo into view. 3. Similar section of a flax-seed more magnified and
divided flatwise; turned round, so that the stem-end (caulicle) of the
embryo is below: the whole broad upper part is the inner face of one of
the cotyledons; the minute nick at its base is the plumule. 4. Similar
section through a seed turned edgewise, showing the thickness of the
cotyledons, and the minute plumule between them, i. e. the minute bud on
the upper end of the caulicle.]

10. Before the nature of these parts in the seed was altogether
understood, technical names were given to them, which are still in use.
These initial leaves were named COTYLEDONS. The initial stem on which
they stand was called the RADICLE. That was because it gives rise to the
first root; but, as it is really the beginning of the stem, and because
it is the stem that produces the root and not the root that produces the
stem, it is better to name it the CAULICLE. Recently it has been named
_Hypocotyle_; which signifies something below the cotyledons, without
pronouncing what its nature is.

[Illustration: Fig. 5. Early Flax seedling; stem (caulicle), root at
lower end, expanded seed-leaves (cotyledons) at the other: minute bud
(plumule) between these. 6. Same later; the bud developed into second
pair of leaves, with hardly any stem-part below them; then into a third
pair of leaves, raised on a short joint of stem; and a fifth leaf also
showing. 7. Same still older, with more leaves developed, but these
singly (one after another), and with joints of stem between them.]

11. On committing these seeds to moist and warm soil they soon sprout,
i. e. _germinate_. The very short stem-part of the embryo is the first
to grow. It lengthens, protrudes its root-end; this turns downward, if
not already pointing in that direction, and while it is lengthening a
root forms at its point and grows downward into the ground. This root
continues to grow on from its lower end, and thus insinuates itself and
penetrates into the soil. The stem meanwhile is adding to its length
throughout; it erects itself, and, seeking the light, brings the seed up
out of the ground. The materials for this growth have been supplied by
the cotyledons or seed-leaves, still in the seed: it was the store of
nourishing material they held which gave them their thickish shape, so
unlike that of ordinary leaves. Now, relieved of a part of this store of
food, which has formed the growth by which they have been raised into
the air and light, they appropriate the remainder to their own growth.
In enlarging they open and throw off the seed-husk; they expand, diverge
into a horizontal position, turn green, and thus become a pair of
evident leaves, the first foliage of a tiny plant. This seedling,
although diminutive and most simple, possesses and puts into use, all
the ORGANS of VEGETATION, namely, root, stem, and leaves, each in its
proper element,--the root in the soil, the stem rising out of it, the
leaves in the light and open air. It now draws in moisture and some
food-materials from the soil by its root, conveys this through the stem
into the leaves, where these materials, along with other crude food
which these imbibe from the air, are assimilated into vegetable matter,
i. e. into the material for further growth.

12. =Further Growth= soon proceeds to the formation of new
parts,--downward in the production of more root, or of branches of the
main root, upward in the development of more stem and leaves. That from
which a stem with its leaves is continued, or a new stem (i. e. branch)
originated, is a BUD. The most conspicuous and familiar buds are those
of most shrubs and trees, bearing buds formed in summer or autumn, to
grow the following spring. But every such point for new growth may
equally bear the name. When there is such a bud between the cotyledons
in the seed or seedling it is called the PLUMULE. This is conspicuous
enough in a bean (Fig. 29.), where the young leaf of the new growth
looks like a little plume, whence the name, _plumule_. In flax-seed this
is very minute indeed, but is discernible with a magnifier, and in the
seedling it shows itself distinctly (Fig. 5, 6, 7).

13. As it grows it shapes itself into a second pair of leaves, which of
course rests on a second joint of stem, although in this instance that
remains too short to be well seen. Upon its summit appears the third
pair of leaves, soon to be raised upon its proper joint of stem; the
next leaf is single, and is carried up still further upon its supporting
joint of stem; and so on. The root, meanwhile, continues to grow
underground, not joint after joint, but continuously, from its lower
end; and commonly it before long multiplies itself by branches, which
lengthen by the same continuous growth. But stems are built up by a
succession of leaf-bearing growths, such as are strongly marked in a
reed or corn-stalk, and less so in such an herb as Flax. The word
"joint" is ambiguous: it may mean either the portion between successive
leaves, or their junction, where the leaves are attached. For precision,
therefore, the place where the leaf or leaves are borne is called a
NODE, and the naked interval between two nodes, an INTERNODE.

[Illustration: Fig. 8. Upper part of Flax-plant in blossom.]

14. In this way a simple stem with its garniture of leaves is developed
from the seed. But besides this direct continuation, buds may form and
develop into lateral stems, that is, _into branches_, from any node. The
proper origin of branches is from the AXIL of a leaf, i. e. the angle
between leaf and stem on the upper side; and branches may again branch,
so