Elements of Structural and Systematic Botany

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ELEMENTS

OF

STRUCTURAL AND SYSTEMATIC BOTANY,

FOR
HIGH SCHOOLS AND ELEMENTARY
COLLEGE COURSES.

BY
DOUGLAS HOUGHTON CAMPBELL, PH.D.,
PROFESSOR OF BOTANY IN THE INDIANA UNIVERSITY.

BOSTON, U.S.A.:
PUBLISHED BY GINN & COMPANY.
1890.

COPYRIGHT, 1890,
BY DOUGLAS HOUGHTON CAMPBELL.

ALL RIGHTS RESERVED.

TYPOGRAPHY BY J. S. CUSHING & CO., BOSTON, U.S.A.
PRESSWORK BY GINN & CO., BOSTON, U.S.A.

PREFACE.

The rapid advances made in the science of botany within the last few
years necessitate changes in the text books in use as well as in
methods of teaching. Having, in his own experience as a teacher, felt
the need of a book different from any now in use, the author has
prepared the present volume with a hope that it may serve the purpose
for which it is intended; viz., an introduction to the study of botany
for use in high schools especially, but sufficiently comprehensive to
serve also as a beginning book in most colleges.

It does not pretend to be a complete treatise of the whole science,
and this, it is hoped, will be sufficient apology for the absence from
its pages of many important subjects, especially physiological topics.
It was found impracticable to compress within the limits of a book of
moderate size anything like a thorough discussion of even the most
important topics of _all_ the departments of botany. As a thorough
understanding of the structure of any organism forms the basis of all
further intelligent study of the same, it has seemed to the author
proper to emphasize this feature in the present work, which is
professedly an _introduction_, only, to the science.

This structural work has been supplemented by so much classification
as will serve to make clear the relationships of different groups, and
the principles upon which the classification is based, as well as
enable the student to recognize the commoner types of the different
groups as they are met with. The aim of this book is not, however,
merely the identification of plants. We wish here to enter a strong
protest against the only too prevalent idea that the chief aim of
botany is the ability to run down a plant by means of an "Analytical
Key," the subject being exhausted as soon as the name of the plant is
discovered. A knowledge of the plant itself is far more important than
its name, however desirable it may be to know the latter.

In selecting the plants employed as examples of the different groups,
such were chosen, as far as possible, as are everywhere common. Of
course this was not always possible, as some important forms, _e.g._
the red and brown seaweeds, are necessarily not always readily
procurable by all students, but it will be found that the great
majority of the forms used, or closely related ones, are within the
reach of nearly all students; and such directions are given for
collecting and preserving them as will make it possible even for those
in the larger cities to supply themselves with the necessary
materials. Such directions, too, for the manipulation and examination
of specimens are given as will make the book, it is hoped, a
laboratory guide as well as a manual of classification. Indeed, it is
primarily intended that the book should so serve as a help in the
study of the actual specimens.

Although much can be done in the study, even of the lowest plants,
without microscopic aid other than a hand lens, for a thorough
understanding of the structure of any plant a good compound microscope
is indispensable, and wherever it is possible the student should be
provided with such an instrument, to use this book to the best
advantage. As, however, many are not able to have the use of a
microscope, the gross anatomy of all the forms described has been
carefully treated for the especial benefit of such students. Such
portions of the text, as well as the general discussions, are printed
in ordinary type, while the minute anatomy, and all points requiring
microscopic aid, are discussed in separate paragraphs printed in
smaller type.

The drawings, with very few exceptions, which are duly credited, were
drawn from nature by the author, and nearly all expressly for this
work.

A list of the most useful books of reference is appended, all of which
have been more or less consulted in the preparation of the following
pages.

The classification adopted is, with slight changes, that given in
Goebel's "Outlines of Morphology and Classification"; while, perhaps,
not in all respects entirely satisfactory, it seems to represent more
nearly than any other our present knowledge of the subject. Certain
groups, like the Diatoms and _Characeae_, are puzzles to the botanist,
and at present it is impossible to give them more than a provisional
place in the system.

If this volume serves to give the student some comprehension of the
real aims of botanical science, and its claims to be something more
than the "Analysis" of flowers, it will have fulfilled its mission.

DOUGLAS H. CAMPBELL.

BLOOMINGTON, INDIANA,
October, 1889.

TABLE OF CONTENTS.

PAGE
CHAPTER I.--INTRODUCTION 1

Composition of Matter; Biology; Botany; Zooelogy; Departments
of Botany; Implements and Reagents; Collecting
Specimens.

CHAPTER II.--THE CELL 6

Parts of the Cell; Formation of New Cells; Tissues.

CHAPTER III.--CLASSIFICATION OF PLANTS 9

Protophytes; Slime-moulds; Schizophytes; Blue-green Slimes,
_Oscillaria_; Schizomycetes, _Bacteria_; Green Monads,
_Euglena_, _Volvox_.

CHAPTER IV.--ALGAE 21

Classification of Algae; Green Algae; _Protococcaceae_,
_Protococcus_; _Confervaceae_, _Cladophora_, _OEdogonium_,
_Coleochaete_.

CHAPTER V.--GREEN ALGAE (_Continued_) 30

Pond-scums, _Spirogyra_; _Siphoneae_, _Vaucheria_; _Characeae_,
_Chara_.

CHAPTER VI.--BROWN SEAWEEDS 41

_Diatomaceae_; True Brown Algae, _Fucus_; Classification of
Brown Algae.

CHAPTER VII.--RED ALGAE 49

Structure of Red Algae; _Callithamnion_; Fresh-Water Forms.

CHAPTER VIII.--FUNGI 54

_Phycomycetes_, _Mycomycetes_; _Phycomycetes_, Black Moulds,
_Mucor_; White Rusts and Mildews, _Cystopus_; Water Moulds.

CHAPTER IX.--TRUE FUNGI 63

Yeast; Smuts; _Ascomycetes_; Dandelion Mildew; Cup Fungi,
_Ascobolus_; Lichens; Black Fungi.

CHAPTER X.--TRUE FUNGI (_Continued_) 77

_Basidiomycetes_; Rusts; _Coprinus_; Classification.

CHAPTER XI.--BRYOPHYTES 86

Classification; Liverworts, _Madotheca_; Classification of
Liverworts; Mosses, _Funaria_; Classification of Mosses.

CHAPTER XII.--PTERIDOPHYTES 102

Bryophytes and Pteridophytes; Germination and Prothallium;
Structure of Maiden-hair Fern.

CHAPTER XIII.--CLASSIFICATION OF PTERIDOPHYTES 116

Ferns; Horse-tails; Club Mosses.

CHAPTER XIV.--SPERMAPHYTES 128

General Characteristics; Gymnosperms and Angiosperms,
Scotch-pine; Classification of Gymnosperms.

CHAPTER XV.--SPERMAPHYTES (_Continued_) 143

Angiosperms; Flowers of Angiosperms; Classification of
Angiosperms; Monocotyledons, Structure of _Erythronium_.

CHAPTER XVI.--CLASSIFICATION OF MONOCOTYLEDONS 153

_Liliiflorae_; _Enantioblastae_; _Spadiciflorae_; _Glumaceae_;
_Scitamineae_; _Gynandrae_, _Helobiae_.

CHAPTER XVII.--DICOTYLEDONS 170

General Characteristics; Structure of Shepherd's-purse.

CHAPTER XVIII.--CLASSIFICATION OF DICOTYLEDONS 181

_Choripetalae_: _Iuliflorae_; _Centrospermae_; _Aphanocyclae_;
_Eucyclae_; _Tricoccae_; _Calyciflorae_.

CHAPTER XIX.--CLASSIFICATION OF DICOTYLEDONS
(_Continued_) 210

_Sympetalae_: _Isocarpae_, _Bicornes_, _Primulinae_, _Diospyrinae_;
_Anisocarpae_, _Tubiflorae_, _Labiatiflorae_, _Contortae_,
_Campanulinae_, _Aggregatae_.

CHAPTER XX.--FERTILIZATION OF FLOWERS 225

CHAPTER XXI.--HISTOLOGICAL METHODS 230

Nuclear Division in Wild Onion; Methods of Fixing, Staining,
and Mounting Permanent Preparations; Reference Books.

INDEX 237

BOTANY.

CHAPTER I.

INTRODUCTION.

All matter is composed of certain constituents (about seventy are at
present known), which, so far as the chemist is concerned, are
indivisible, and are known as elements.

Of the innumerable combinations of these elements, two general classes
may be recognized, organic and inorganic bodies. While it is
impossible, owing to the dependence of all organized matter upon
inorganic matter, to give an absolute definition, we at once recognize
the peculiarities of organic or living bodies as distinguished from
inorganic or non-living ones. All living bodies feed, grow, and
reproduce, these acts being the result of the action of forces
resident within the organism. Inorganic bodies, on the other hand,
remain, as a rule, unchanged so long as they are not acted upon by
external forces.

All living organisms are dependent for existence upon inorganic
matter, and sooner or later return these elements to the sources
whence they came. Thus, a plant extracts from the earth and air
certain inorganic compounds which are converted by the activity of the
plant into a part of its own substance, becoming thus incorporated
into a living organism. After the plant dies, however, it undergoes
decomposition, and the elements are returned again to the earth and
atmosphere from which they were taken.

Investigation has shown that living bodies contain comparatively few
elements, but these are combined into extraordinarily complex
compounds. The following elements appear to be essential to all living
bodies: carbon, hydrogen, oxygen, nitrogen, sulphur, potassium.
Besides these there are several others usually present, but not
apparently essential to all organisms. These include phosphorus, iron,
calcium, sodium, magnesium, chlorine, silicon.

As we examine more closely the structure and functions of organic
bodies, an extraordinary uniformity is apparent in all of them. This
is disguised in the more specialized forms, but in the simpler ones is
very apparent. Owing to this any attempt to separate absolutely the
animal and vegetable kingdoms proves futile.

The science that treats of living things, irrespective of the
distinction between plant and animal, is called "Biology," but for
many purposes it is desirable to recognize the distinctions, making
two departments of Biology,--Botany, treating of plants; and Zooelogy,
of animals. It is with the first of these only that we shall concern
ourselves here.

When one takes up a plant his attention is naturally first drawn to
its general appearance and structure, whether it is a complicated one
like one of the flowering plants, or some humbler member of the
vegetable kingdom,--a moss, seaweed, toadstool,--or even some still
simpler plant like a mould, or the apparently structureless green scum
that floats on a stagnant pond. In any case the impulse is to
investigate the form and structure as far as the means at one's
disposal will permit. Such a study of structure constitutes
"Morphology," which includes two departments,--gross anatomy, or a
general study of the parts; and minute anatomy, or "Histology," in
which a microscopic examination is made of the structure of the
different parts. A special department of Morphology called
"Embryology" is often recognized. This embraces a study of the
development of the organism from its earliest stage, and also the
development of its different members.

From a study of the structure of organisms we get a clue to their
relationships, and upon the basis of such relationships are enabled to
classify them or unite them into groups so as to indicate the degree
to which they are related. This constitutes the division of Botany
usually known as Classification or "Systematic Botany."

Finally, we may study the functions or workings of an organism: how it
feeds, breathes, moves, reproduces. This is "Physiology," and like
classification must be preceded by a knowledge of the structures
concerned.

For the study of the gross anatomy of plants the following articles
will be found of great assistance: 1. a sharp knife, and for more
delicate tissues, a razor; 2. a pair of small, fine-pointed scissors;
3. a pair of mounted needles (these can be made by forcing ordinary
sewing needles into handles of pine or other soft wood); 4. a hand
lens; 5. drawing-paper and pencil, and a note book.

For the study of the lower plants, as well as the histology of the
higher ones, a compound microscope is indispensable. Instruments with
lenses magnifying from about 20 to 500 diameters can be had at a cost
varying from about $20 to $30, and are sufficient for any ordinary
investigations.

Objects to be studied with the compound microscope are usually
examined by transmitted light, and must be transparent enough to allow
the light to pass through. The objects are placed upon small glass
slips (slides), manufactured for the purpose, and covered with
extremely thin plates of glass, also specially made. If the body to be
examined is a large one, thin slices or sections must be made. This
for most purposes may be done with an ordinary razor. Most plant
tissues are best examined ordinarily in water, though of course
specimens so mounted cannot be preserved for any length of time.[1]

[1] For the mounting of permanent preparations, see Chapter XIX.

In addition to the implements used in studying the gross anatomy, the
following will be found useful in histological work: 1. a small
camel's-hair brush for picking up small sections and putting water in
the slides; 2. small forceps for handling delicate objects; 3.
blotting paper for removing superfluous water from the slides and
drawing fluids under the cover glass; 4. pieces of elder or sunflower
pith, for holding small objects while making sections.

In addition to these implements, a few reagents may be recommended for
the simpler histological work. The most important of these are
alcohol, glycerine, potash (a strong solution of potassium hydrate in
water), iodine (either a little of the commercial tincture of iodine
in water, or, better, a solution of iodine in iodide of potassium),
acetic acid, and some staining fluid. (An aqueous or alcoholic
solution of gentian violet or methyl violet is one of the best.)

A careful record should be kept by the student of all work done, both
by means of written notes and drawings. For most purposes pencil
drawings are most convenient, and these should be made with a
moderately soft pencil on unruled paper. If it is desired to make the
drawings with ink, a careful outline should first be made with a hard
pencil and this inked over with India-ink or black drawing ink. Ink
drawings are best made upon light bristol board with a hard,
smooth-finished surface.

When obtainable, the student will do best to work with freshly
gathered specimens; but as these are not always to be had when wanted,
a few words about gathering and preserving material may be of service.

Most of the lower green plants (_algae_) may be kept for a long time in
glass jars or other vessels, provided care is taken to remove all
dead specimens at first and to renew the water from time to time. They
usually thrive best in a north window where they get little or no
direct sunshine, and it is well to avoid keeping them too warm.

Numbers of the most valuable fungi--_i.e._ the lower plants that are
not green--grow spontaneously on many organic substances that are kept
warm and moist. Fresh bread kept moist and covered with a glass will
in a short time produce a varied crop of moulds, and fresh horse
manure kept in the same way serves to support a still greater number
of fungi.

Mosses, ferns, etc., can be raised with a little care, and of course
very many flowering plants are readily grown in pots.

Most of the smaller parasitic fungi (rusts, mildews, etc.) may be kept
dry for any length of time, and on moistening with a weak solution of
caustic potash will serve nearly as well as freshly gathered specimens
for most purposes.

When it is desired to preserve as perfectly as possible the more
delicate plant structures for future study, strong alcohol is the best
and most convenient preserving agent. Except for loss of color it
preserves nearly all plant tissues perfectly.

CHAPTER II.

THE CELL.

If we make a thin slice across the stem of a rapidly growing
plant,--_e.g._ geranium, begonia, celery,--mount it in water, and
examine it microscopically, it will be found to be made up of numerous
cavities or chambers separated by delicate partitions. Often these
cavities are of sufficient size to be visible to the naked eye, and
examined with a hand lens the section appears like a piece of fine
lace, each mesh being one of the chambers visible when more strongly
magnified. These chambers are known as "cells," and of them the whole
plant is built up.

[Illustration: FIG. 1.--A single cell from a hair on the stamen of the
common spiderwort (_Tradescantia_), x 150. _pr._ protoplasm; _w_, cell
wall; _n_, nucleus.]

In order to study the structure of the cell more exactly we will
select such as may be examined without cutting them. A good example
is furnished by the common spiderwort (Fig. 1). Attached to the base
of the stamens (Fig. 85, _B_) are delicate hairs composed of chains
of cells, which may be examined alive by carefully removing a stamen
and placing it in a drop of water under a cover glass. Each cell
(Fig. 1) is an oblong sac, with a delicate colorless wall which
chemical tests show to be composed of cellulose, a substance closely
resembling starch. Within this sac, and forming a lining to it, is
a thin layer of colorless matter containing many fine granules.
Bands and threads of the same substance traverse the cavity of the
cell, which is filled with a deep purple homogeneous fluid. This
fluid, which in most cells is colorless, is called the cell sap, and
is composed mainly of water. Imbedded in the granular lining of the
sac is a roundish body (_n_), which itself has a definite membrane,
and usually shows one or more roundish bodies within, besides an
indistinctly granular appearance. This body is called the nucleus of
the cell, and the small one within it, the nucleolus.

The membrane surrounding the cell is known as the cell wall, and in
young plant cells is always composed of cellulose.

The granular substance lining the cell wall (Fig. 1, _pr._) is
called "protoplasm," and with the nucleus constitutes the living
part of the cell. If sufficiently magnified, the granules within the
protoplasm will be seen to be in active streaming motion. This
movement, which is very evident here, is not often so conspicuous,
but still may often be detected without difficulty.

[Illustration: FIG. 2.--An _Amoeba_. A cell without a cell wall. _n_,
nucleus; _v_, vacuoles, x 300.]

The cell may be regarded as the unit of organic structure, and of
cells are built up all of the complicated structures of which the
bodies of the highest plants and animals are composed. We shall find
that the cells may become very much modified for various purposes, but
at first they are almost identical in structure, and essentially the
same as the one we have just considered.

[Illustration: FIG. 3.--Hairs from the leaf stalk of a wild geranium.
_A_, single-celled hair. _B_ and _C_, hairs consisting of a row of
cells. The terminal rounded cell secretes a peculiar scented oil that
gives the plant its characteristic odor. _B_, x 50; _C_, x 150.]

Very many of the lower forms of life consist of but a single cell
which may occasionally be destitute of a cell wall. Such a form is
shown in Figure 2. Here we have a mass of protoplasm with a nucleus
(_n_) and cavities (vacuoles, _v_) filled with cell sap, but no cell
wall. The protoplasm is in constant movement, and by extensions of a
portion of the mass and contraction of other parts, the whole creeps
slowly along. Other naked cells (Fig. 12, _B_; Fig. 16, _C_) are
provided with delicate thread-like processes of protoplasm called
"cilia" (sing. _cilium_), which are in active vibration, and propel
the cell through the water.

[Illustration: FIG. 4.--_A_, cross section. _B_, longitudinal section
of the leaf stalk of wild geranium, showing its cellular structure.
_Ep._ epidermis. _h_, a hair, x 50. _C_, a cell from the prothallium
(young plant) of a fern, x _150_. The contents of the cell contracted
by the action of a solution of sugar.]

On placing a cell into a fluid denser than the cell sap (_e.g._ a
ten-per-cent solution of sugar in water), a portion of the water
will be extracted from the cell, and we shall then see the
protoplasm receding from the wall (Fig. 4, _C_), showing that it is
normally in a state of tension due to pressure from within of the
cell sap. The cell wall shows the same thing though in a less
degree, owing to its being much more rigid than the protoplasmic
lining. It is owing to the partial collapsing of the cells,
consequent on loss of water, that plants wither when the supply of
water is cut off.

As cells grow, new ones are formed in various ways. If the new cells
remain together, cell aggregates, called tissues, are produced, and
of these tissues are built up the various organs of the higher plants.
The simplest tissues are rows of cells, such as form the hairs
covering the surface of the organs of many flowering plants (Fig. 3),
and are due to a division of the cells in a single direction. If the
divisions take place in three planes, masses of cells, such as make up
the stems, etc., of the higher plants, result (Fig. 4, _A_, _B_).

CHAPTER III.

CLASSIFICATION OF PLANTS.--PROTOPHYTES.

For the sake of convenience it is desirable to collect into groups
such plants as are evidently related; but as our knowledge of many
forms is still very imperfect, any classification we may adopt must be
to a great extent only provisional, and subject to change at any time,
as new forms are discovered or others become better understood.

The following general divisions are usually accepted: I. Sub-kingdom
(or Branch); II. Class; III. Order; IV. Family; V. Genus; VI. Species.

To illustrate: The white pine belongs to the highest great division
(sub-kingdom) of the plant kingdom. The plants of this division all
produce seeds, and hence are called "spermaphytes" ("seed plants").
They may be divided into two groups (classes), distinguished by
certain peculiarities in the flowers and seeds. These are named
respectively "gymnosperms" and "angiosperms," and to the first our
plant belongs. The gymnosperms may be further divided into several
subordinate groups (orders), one of which, the conifers, or
cone-bearing evergreens, includes our plant. This order includes
several families, among them the fir family (_Abietineae_), including
the pines and firs. Of the sub-divisions (_genera_, sing. _genus_) of
the fir family, one of the most familiar is the genus _Pinus_, which
embraces all the true pines. Comparing different kinds of pines, we
find that they differ in the form of the cones, arrangement of the
leaves, and other minor particulars. The form we have selected differs
from all other native forms in its cones, and also in having the
leaves in fives, instead of twos or threes, as in most other kinds.
Therefore to distinguish the white pine from all other pines, it is
given a "specific" name, _strobus_.

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