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Full text of "Beginners botany"

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BEGINNERS' BOTANY 



THE MACMILLAN COMPANY 

NEW YORK • BOSTON • CHICAGO 
SAN FRANCISCO 

MACMILLAN & CO , Limited 

LONDON • BOMBAY • CALCUTTA 
MELBOURNE 

THE MACMILLAN CO. OF CANADA, Ltdw 

TORONTO 




BOUQUET OF BEARDED WHEAT 



BEGINNERS' BOTANY 



BY 

L. H. BAILEY 




AUTHORIZED BY THE MINISTER OF EDUCATION 
FOR ONTARIO 



TORONTO 
THE MACMILLAN CO. OF CANADA, LIMITED 

1921 



Copyright, 1921 
By the MACMILLAN CO. OF CANADA LTD. 



PREFACE 

In ail teaching of plants and animals to beginners, the 
plants themselves and the animals themselves should be 
made the theme, rather than any amount of definitions and 
of mere study in l)ooks. Books will be very useful m 
guiding the way, in arranging the subjects systematically, 
and in explaining obscure points ; but if the pupil does not 
know the living and growing plants when he has completed 
his course in botany, he has not acquired very much that 
is worth the while. 

It is well to acquaint the beginner at first with the main 
features of the entire plant rather than with details of its 
parts. He should at once form a mental picture of what 
the plant is, and what are some of its broader adaptations 
to the life that it leads. In this book, the pupil starts v/ith 
the entire branch or the entire plant. It is sometimes said 
that the pupil cannot grasp the idea of struggle for exist- 
ence until he knows the names and the uses of the different 
parts of the plant. This is an error, although well estab- 
lished in present-day methods of teaching. 

Another very important consideration is to adapt the 
statement of any fact to the understanding of a beginner. 
It is easy, for example, to fall into technicalities when dis 
cussing osmosis ; but the minute explanations would mean 
nothing to the beginner and their use would tend to con- 
fuse the picture which it is necessary to leave in the pupil's 
mind. Even the use of technical forms of expression would 
probably not go far enough to satisfy the trained physicist. 



Vi PREFACE 

It IS impossible ever to state the last thing about any 
proposition. All knowledge is relative. What is very 
elementary to one mind may be very technical and ad- 
vanced to another. It is neither necessary nor desirable 
to safeguard statements to the beginner by such qualifica- 
tions as will make them satisfactory to the critical expert 
in science. The teacher must understand that while 
accuracy is always essential, the degree of statement is 
equally important when teaching beginners. 

The value of biology study lies in the work with the 
actual objects. It is not possible to provide specimens for 
every part of the work, nor is it always desirable to do so ; 
for the beginning pupil may not be able to interest himself 
in the objects, and he may become immersed in details 
before he has arrived at any general view or reason of the 
subject. Great care must be exercised that the pupil is 
not swamped. Mere book work or memory stuffing is 
useless, and it may dwarf or divert the sympathies of 
active young minds. 

The present tendency in secondary education is away 
from the formal technical completion of separate subjects 
and toward the developing of a workable training in the 
activities that relate the pupil to his own life. In the 
natural science field, the tendency is to attach less im- 
portance to botany and zoology as such, and to lay greater 
stress on the processes and adaptations of life as expressed 
in plants and animals. Education that is not applicable, 
that does not put the pupil into touch with the living know- 
ledge and the affairs of his time, may be of less educative 
value than the learning of a trade in a shop. "We are begin- 
ning to learn that the ideals and the abilities should he 
developed out of the common surroundings and affairs of 



PREFACE 



VII 



life ratlier than imposed on the pupil as a matter of 
abstract unrelated theory 

It is much better for the beginning pupil to acquire a 
real conception of a few central principles and points of 
view respecting common forms that will enable him to tie 
his knowledge together and organize it and apply it, than 
to familiarize himself with any number of mere facts about 
the lower forms of life which, at the best, he can know 
only indirectly and remotely. If the pupil wishes to go 
farther in later years, he may then take up special groups 
and phases. 



CONTENTS 



CHAPTER 

I. No Two Plants or Parts are Alike 

II. The Struggle to Live 

III. Survival of the Fit 

IV. Plant Societies 
V. The Plant Body 

VI. Seeds and Germination 

VII. The Root — The Forms of Roots 

VIII. The Root — Function and Structure 

IX. The Stem — Kinds and Forms — Pruning 

X. The Stem — Its General Structure 

XI. Leaves — Form and Position . 

XII. Leaves — Structure and Anatomy 

XIII. Leaves — Function or Work 

XIV. Dependent Plants . 
XV. Winter and Dormant Buds 

XVI. Bud Propagation 

XVII. How Plants Climb . 

XVIII. The Flower — Its Parts and Forms 

XIX. The Flower — Fertilization and Poll 

XX. Flower-clusters 

XXI. Fruits 

XXII, Dispersal of Seeds . 

XXIII. Phenogams and Cryptogams 

XXIV. Studifis in Cryptogams 
Index 



BEGINNERS' BOTANY 



CHAPTER I 
NO TWO PLANTS OR PARTS ARE ALIKE 




Fig. I. — No Two Branches are Alike. 
(Hemlock.) 

If one compares any two plants of 
the same kind ever so closely, it will be 
found that they differ from each other. The 
;. difference is apparent in size, form, colour, mode 
of branching, number of leaves, number of flowers, vigour, 
season of maturity, and the like; or, in other words, all 
plants and animals vary from an assumed or sta^tdard type. 
If one compares any two brandies or twigs on a tree, it 
will be found that they differ in size, age, form, vigour, and 
in other ways (Fig. i). 

If one compares a7ty tivo leaves, it will be found that 
they are unlike in size, shape, colour, yeining, hairiness, 
markings, cut of the margins, or other small features. In 
some cases (as in Fig. 2) the differences are so great as to 
be readily seen in a small black-and-white drawing. 



BEGINNERS' BOTANY 



If the pupil extends his observation to animals, he 
will still find the same truth ; for probably no two living 
objects are exact duplicates. If any person finds two objects 
that he thinks to be exactly alike, let him set to work to 




Fig. 2. — No Two Leaves are Alike. 

discover the differences, remembering that nothing in 
nature is so small or apparently trivial as to be overlooked. 

Variation, or differences between organs and also be- 
tween organisms, is one of the most significant facts in 
nature. 

Suggestions. — The first fact that the pupil should acquire 
about plants is that no two are alike. The way to apprehend this 
great fact is to see a plant accurately and then to compare it with 



NO TWO PLANTS OR PARTS ARE ALIKE 3 

another plant of the same species or kind. In order to direct and 
concentrate the observation, it is well to set a certain number of 
attributes or marks or qualities to be looked for. 1. Suppose 
any two or more plants of corn are compared in the following 
points, the pupil endeavouring to determine whether the 
parts exactly agree. See that the observation is close and 
accurate. Allow no guesswork. Instruct the pupil to meas- 
ure the parts when size is involved. 

(1) Height of the plant. 

(2) Does it branch? How many secondary stems or "suckers' 
from one root? 

(3) Shade or colour. 

(4) How many leaves. 

(5) Arrangement of leaves on stem. 

(6) Measure length and breadth of six main leaves. 

(7) Number and position of ears; colour of silks. 

(8) Size of tassel, and number and size of its branches. 

(9) Stage of maturity or ripeness of plant. 

(10) Has the plant grown symmetrically, or has it been crowded 
by other plants or been obliged to struggle for light or room? 

(11) Note all unusual or interesting marks or features. 

(12) Always make note of comparative vigour of the plants. 

Note to Teacher. — The teacher should always insist on per- 
sonal work by the pupil. Every pupil should handle and study 
the object by himself. Books and pictures are merely guides and 
helps. So far as possible, study the plant or animal just where it 
grows naturally. 

Notebooks. — Insist that the pupils make full notes and preserve 
these notes in suitable books. Note-taking is a powerful aid in 
organizing the mental processes, and in insuring accuracy of obser- 
vation and record. The pupil should draw what he sees, even 
though he is not expert with the pencil. The drawing should not 
be made for looks, but to aid the pupil in his orderly study of the 
object ; it should be a means of self-expression. 



CHAPTER II 
THE STRUGGLE TO LIVE 

Every plant and animal is exposed to unfavourable con- 
ditions. It is obliged to contend with these conditions in 
order to live. 

No two plants or parts of plants are identically exposed 
to the conditions in which they live. The large branches 




Fig. 3. — a Battle for Life. 

in Fig. I probably had more room and a better exposure 
to light than the smaller ones. Probably no two of the 
leaves in Fig. 2 are equally exposed to light, or enjoy 
identical advantages in relation to the food that they re- 
ceive from the tree. 

Examine any tree to determine under what advantages 
or disadvantages any of the limbs may live. Examine 
similarly the different plants in a garden row (Fig. 3); or 
the different bushes in a thicket ; or the different trees in 
a wood. 

4 



THE STRUGGLE TO LIVE 



5 



The plant meets its conditions by succtmibing to them 
(that is, by dying), or by adapting itself to them. 

The tree meets the cold by ceasing its active growth, 
hardening its tissues, dropping its leaves. Many her- 
baceous or soft-stemmed plants meet the cold by dying 
to the ground and withdrawing all life into the root parts. 
Some plants meet the cold by dying outright and provid- 
ing abundance of seeds to perpetuate the kind next season. 




Fig. 4. — The Reach for Light of a Tree on the Edge of a Wood. 

Plants adapt themselves to light by growing toward it 
(Fig. 4); or by hanging their leaves in such position that 
they catch the light ; or, in less sunny places, by expand- 
ing their leaf surface, or by greatly lengthening their 
stems so as to overtop their fellows, as do trees and vines. 

The adaptations of plants will afford a fertile field of 
study as we proceed. 



6 BEGINNERS' BOTANY 

Struggle for existence and adaptation to conditions are 

among the most significant facts in nature. 

The sum of all the conditions in which a plant or an ani- 
mal is placed is called its environment, that is, its surround- 
ings. The environment comprises the conditions of climate, 
soil, moisture, exposure to light, relation to food supply, 
contention with other plants or animals. The organism 
adapts itself to its eiivironmcnt, or else it weakens or dies- 
Every weak branch or plant has undergone some hardship 
that it was not wholly able to withstand. 

Suggestions. — The pupil should study any plant, or branch of a 
plant, with reference to the position or condition under -which it 
grows, and compare one plant or branch with another. With animals, 
it is common knowledge that every animal is alert to avoid or to 
escape danger, or to protect itself. 2. It is well to begin with a 
branch of a tree, as in Fig. 1. Note that no two parts are alike (Chap. 
T). Note that some are large and strong and that these stand far- 
thest toward light and room. Some are very small and weak, barely 
able to live under the competition. Some have died. The pupil can 
easily determine which of the dead branches perished first. He should 
take note of the position or place of the branch on the tree, and 
determine whether the greater part of the dead twigs are toward the 
centre of the tree top or toward the outside of it. Determine whether 
accident has overtaken any of the parts. 3. Let the pupil examine 
the top of any thick old apple tree, to see whether there is any 
struggle for existence and whether any limbs have perished. 4. If 
the pupil has access to a forest, let him determine why there are no 
branches on the trunks of the old trees. Examine a tree of the 
same kind growing in an open field. 5. A row of lettuce or other 
plants sown thick will soon show the competition between plants. 
Any fence row or weedy place will also show it. Why does the 
farmer destroy the weeds among the corn or potatoes? TIoav does 
the florist reduce competition to its lowest terms? what is the result? 



CHAPTER III 



THE SURVIVAL OF THE FIT 



The plants that most perfectly meet their conditions are 
able to persist. They perpetuate themselves. Their off- 
spring are likely to inherit some of the attributes that 
enabled them successfully to meet the battle of life. The 
fit (those best adapted to their conditions) tend to survive. 

Adaptation to conditions depends on the fact of varia- 
tion; that is, if plants were perfectly rigid or invariable 
(all exactly aUke) they could not meet new conditions. 
Conditions are necessarily new for every organism. It is 
impossible to picture a perfectly inflexible and stable succes- 
sion of plants or animals. 

Breeding. — Man is able to modify plants and animals. 
A.11 our common domestic animals are very unlike their 
original ancestors. So all our common and long-culti- 
vated plants have varied 
from their ancestors. Even 
in some plants that have 
been in cultivation less than 
a century the change is 
marked : compare the com- 
mon black-cap raspberry 
with its common wild ances- 
tor, or the cultivated black- 
berry with the wild form. 

By choosing seeds from a plant that pleases him, the 
breeder may be able, under given conditions, to produce 

7 




Fig. 5. — Desirable and Undesirable 
Types of Cotton Plants. Why? 



BEGINNERS' BOTANY 




Fig. 6, — Flax Breeding. 

A '.s a plant grown for seed production 

/; f'i.r lil.iv iinMlur.tioii. Wl'.y? 



Suggestions. 
• — 6. Every pu- 
pil should un- 
dertake at least 
one simple ex- 
periment in se- 
lection of s6ed. He may select kernels from the 
best plant of corn in the field, and also from the 
poorest plant, — having reference not so much to 
mere incidental size and vigour of the plants that 
may be due to accidental conditions in the field, 
as to the apparently constitutional strength and 
size, number of ears, size of ears, perfectness of 
cars and kernels, habit of the plant as to sucker- 
ing, and the like. The seeds may be saved and 
sown the next year. Every crop can no doubt 
be very greatly improved by a careful process 
of selection extending over a series of years. 
Crops are increased in yield or efficiency in three 
ways: better general care; enriching the land in 
which they grow; attention to bre(>dinfT. 



numbers of plants with more 
or less of the desired quali- 
ties; from the best of these, 
he may again choose ; and so 
on until the race becomes 
greatly improved (Figs. 5, 6, 
7). This process of continu- 
ously choosing the most suita- 
ble plants is known as selec- 
tion. A some- 
what similar 
process pro- 
ceeds in wild 
nature, and it 
is then known 
as natural se- 
lection. 




Fig. 7. — Breed- 
ing. 

A, effect from breed- 
ing from smallest 
grains (after four 
years), average 
head; B, result 
from breeding from 
the plumpest and 
heaviest grains 
(after four years), 
average head. 



CHAPTER IV 
PLANT SOCIETIES 

In the long course of time in which plants have been 
accommodating themselves to the varying conditions in 
which they are obHged to grow, tJiey have become adapted 
to every different environment. Certain plants, therefore, 
may live together or near each other, all enjoying the 
same general conditions and surroundings. These aggre- 
gations of plants that are adapted to similar general con- 
ditions are known as plant societies. 

Moisture and temperature are the leading factors in 
determining plant societies. The great geographical 
societies or aggregations of the plant world may con- 
veniently be associated chiefly with the moisture supply, 
as : wet-7'egion societies^ comprising aquatic and bog 
vegetation (Fig. 8); arid-region societies ^ comprising desert 
and most sand-region vegetation ; mid-region societies^ 
comprising the mixed vegetation in intermediate regions 
(Fig. 9), this being the commonest type. Much of the 
characteristic scenery of any place is due to its plant 
societies. Arid-region plants usually have small and hard 
leaves, apparently preventing too rapid loss of water. 
Usually, also, they are characterized by stiff growth, hairy 
covering, spines, or a much-contracted plant-body, and 
often by large underground parts for the storage of water. 

Plant societies may also be distinguished with reference 
to latitude and temperature. There are tropical societies^ 
temperate-region societies^ boreal or cold-region societies. 

9 



lO 



BEGINNERS' BOTANY 



With reference to altitude, societies might be classified 
as lowland (which are chiefly wet-region), intennediaie 
(chiefly mid-region), stibalpijie or mid-moimtam (which are 
chiefly boreal), alpine or high-moimtain. 

The above classifications have reference chiefly to great 
geographical floras or societies. But there are societies 
within societies. There are small societies coming within 
the experience of every person who has ever seen plants 




Fig. 8. — a Wet-region Society. 

growing in natural conditions. There are roadside, fence- 
row, lawn, thicket, pasture, dune, woods, cliff, barn-yard 
societies. Every different place has its characteristic vegeta- 
tion. Note the smaller societies in Figs. 8 and 9. In the 
former is a water-lily society and a cat-tail society. In 
the latter there are grass and bush and woods societies. 

Some Details of Plant Societies. — Societies may be com- 
posed of scattered and iiitermingled plants^ or of dense 
chimps or groups of plants. Dense clumps or groups are 
usually made up of one kind of plant, and they are then 



PLANT SOCIETIES 



II 



called colonies. Colonies of most plants are transient: 
after a short time other plants gain a foothold amongst 
them, and an intermingled society is the outcome. Marked 
exceptions to this are grass colonies and forest colonies, in 
which one kind of plant may hold its own for years and 
centuries. 

In a large newly cleared area, plants usually ^n-/ estab- 
lish themselves in dense colonies. Note the great patches 




Fig. 9. — a Mid-region Society. 

of nettles, jewel-weeds, smart-weeds, clot-burs, fire-weeds 
in recently cleared but neglected swales, also the fire-weeds 
in recently burned areas, the rank weeds in the neglected 
garden, and the ragweeds and May-weeds along the re- 
cently worked highway. The competition amongst them- 
selves and with their neighbours finally breaks up the 
colonies, and a mixed and intei^mingled flora is generally 
the result. 

In many parts of the world the general tendency of neg- 
lected areas is to run into forest. All plants rush for the 



12 



BEGINNERS' BOTANY 



cleared area. Here and there bushes gain a foothold. 
Young trees come up ; in time these shade the bushes and 
gain the mastery. Sometimes the area grows to poplars 
or birches, and people wonder why the original forest trees 
do not return ; but these forest trees may be growing unob- 
served here and there in the tangle, and in the slow pro- 
cesses of time the poplars perish — for they are short-lived 
— and the original forest may be replaced. Whether one 
kind of forest or another returns will depend partly on the 
kinds that are most seedful in that vicinity and which, 
therefore, have sown themselves most profusely. Much 
depends, also, on the kind of undergrowth that first springs 
up, for some young trees can endure more or less shade 
than others. 

Some plants associate. They grow together. This is 
possible largely because they diverge or differ in charac- 
ter. Plants asso- 
ciate in two ways : 
by grvwing side by 
side ; by groiving 
above or beneath. 
In sparsely popu- 
lated societies, 
plants may grow 
alongside each 
other. In most 
cases, however, 
there is overgrowth 
and undergrowth: 
one kind grows beneath another. Plants that have be- 
come adapted to shade are usually undergrowths. In a cat- 
tail swamp, grasses and other narrow-leaved plants grow 
in the bottom, but they are usually unseen by the casual 




Fig. io. — Overgrowth and Undergrowth in 
Three Series, — trees, bushes, grass. 



PLANT SOCIETIES 1 3 

observer. Note the undergrowth in woods or under trees 
(Fig. 10). Observe that in pine and spruce forests there 
is almost no undergrowth, partly because there is very little 
light. 

On the same area the societies may differ at different 
times of the year. There are spring, summer, and fall soci- 
eties. The knoll which is cool with grass and strawber- 
ries in June may be aglow with goldenrod in September. 
If the bank is examined in May, look for the young plants 
that are to cover it in July and October; if in Septem- 
ber, find the dead stalks of the flora of May. What suc- 
ceeds the skunk cabbage, hepaticas, trilliums, phlox, violets, 
buttercups of spring } What precedes the wild sunflowers, 
ragweed, asters, and goldenrod of fall } 

The Landscape.— To a large extent the colour of the land- 
scape is determined by the character of the plant societies. 
Evergreen societies remain green, but the shade of green 
varies from season to season; it is bright and soft in 
spring, becomes dull in midsummer and fall, and assumes 
a dull yellow-green or a black-green in winter. Deciduous 
societies vary remarkably in colour — from the dull browns 
and grays of winter to the brown greens and olive-greens 
of spring, the staid greens of summer, and the brilliant 
colours of autumn. 

The autumn colours are due to intermingled shades of 
green, yellow and red. The coloration varies with the kind 
of plant, the special location, and the season. Even in the 
same species or kind, individual plants differ in colour ; and 
this individuality usually dstinguishes the plant year by 
year. That is, an oak which is maroon red this autumn is 
likely to exhibit that range of colour every year. The au- 
tumn colour is associated with the natural maturity and 
death of the leaf, but it is most brilliant in long and open 



14 BEGTNNEJiS' BOTANY 

falls — largely because the foliage ripens more gradually 
and persists longer in such seasons. It is probable that 
the autumn tints are of no utility to the plant. Autumn 
colours are not caused hy frost. Because of the long, dry 
falls and the great variety of plants, the autumnal colour of 
the American landscape is phenomenal. 

Ecology. — The study of the relationships of plants and 
animals to each other and to seasons and environments is 
known as ecology (still written cccology in the dictionaries). 
It considers the habits, habitats, and modes of life of liv- 
ing things — the places in which they grow, how they 
migrate or are disseminated, means of collecting food, 
their times and seasons of flowering, producing young, 
and the like. 

Suggestions. — One of the best of all subjects for school instruc- 
tion in botany is the study of plant societies. It adds definiteness 
and zest to excursions. 7. Let each excursion be confined to one 
or two societies. Visit one day a swamp, another day a forest, 
another a pasture or meadow, another a roadside, another a weedy 
field, another a cliff or ravine. Visit shores whenever possible. 
Each pupil should be assigned a bit of ground — say lo or 20 ft. 
square — for special study. He should make a list showing (i) 
how many kinds of plants it contains, (2) the relative abundance 
of each. The lists secured in different regions should be com- 
pared. It does not matter greatly if the pupil does not know all 
the plants. He may count the kinds without knowing the names. 
It is a good plan for the pupil to make a dried specimen of each 
kind for reference. The pupil should endoavour to discover why 
the plants grow as they do. Note what kinds of plants grow next 
each other ; and which are undergrowth and which overgrowth ; 
and which are erect and which wide-spreading. Challenge every 
plant society. 



CHAPTER V 
THE PLANT BODY 

The Parts of a Plant. — Our familiar plants are made up 
cf several distinct parts. The most prominent of these 
parts are root, stem, leaf, flower, fruit, and seed. Familiar 
plants differ wonderfully ift size a7td sJiape, — from fragile 
mushrooms, delicate waterweeds and pond-scums, to float- 
ing leaves, soft grasses, coarse weeds, tall bushes, slender 
climbers, gigantic trees, and hanging moss. 

The Stem Part. — In most plants there is a main central 
part or shaft on which the other or secondary parts are 
borne. This main part is the plant axis. Above ground, 
in most plants, the main plant axis bears the branches ^ 
leaves, diXidi flowers ; below ground, it bears the roots. 

The rigid part of the plant, which persists over winter 
and which is left after leaves and flowers are fallen, is the 
framework of the plant. The framework is composed of 
both root and stem. When the plant is dead, the frame- 
work remains for a time, but it slowly decays. The dry 
winter stems of weeds are the framework, or skeleton of 
the plant (Figs, ii and 12). The framework of trees is 
the most conspicuous part of the plant. 

The Root Part. — The root bears the stem at its apex, 
but otherwise it normally bears only root-branches. The 
stem, however, bears leaves, flowers, and fruits. Those 
Hving surfaces of the plant which are most exposed to 
light are green or highly coloured. The root tends to grow 
downward, but the stem tends to grow upward tozvard light 

lb 



i6 



BEGINNERS' BOTANY 



and air. The plant is anchored or fixed in the soil by the 
roots. Plants have been called "earth parasites." 

The Foliage Part. — The leaves precede the flowers in 
point of time or life of the plant. TJie flowers always 
preeede the fruits and seeds. Many plants die when the 
seeds have matured. The whole mass of leaves of any 

plant or any branch is 
known as its foliage. 
In some cases, as in 
crocuses, the flowers 
seem to precede the 
leaves; but the leaves 
that made the food for 
these flowers grew the 
preceding year. 

The Plant Generation. 
— The course of * a 
plant's life, with all the 
events through which 
the plant naturally 
passes, is known as 
the plant's life-history. 
The life-history em- 
braces various stages, 
or epochs, as dormant 
seed, gerin ination, grow thy flowering, fruiting. Some plan ts 
run their course in a few weeks or months, and some live 
for centuries. 

The entire life-period of a plant is called a generation. 
It is the whole period from birth to normal death, without 
reference to the various stages or events through which it 
passes. 

A generation begins with the young seed, not with germi- 




j&R. vt. — Plant of a 
Vhitib Sunflower. 



Fig. 12— Frame- 
work OF Fig. h. 



THE PLANT BODY 1/ 

nation. // ends with death — that is, when no life is left 
in any part of the plant, and only the seed or spore 
remains to perpetuate the kind. In a bulbous plant, as a 
lily or an onion, the generation does not end until the bulb 
dies, even though the top is dead. 

When the generation is of only one season's duration, 
the plant is said to be annual. When it is of two seasons, 
it is biennial. Biennials usually bloom the second year. 
When of three or more seasons, the plant is perennial. 
Examples of annuals are pigweed, bean, pea, garden sun- 
flower ; of biennials, evening primrose, mullein, teasel ; of 
perennials, dock, most meadow grasses, cat-tail, and all 
shrubs and trees. 

Duration of the Plant Body. — Plant structures which 
are more or less soft and which die at the close of the 
season are said to be herbaceous, in contradistinction to 
being ligneous or woody. A plant which is herbaceous to 
the ground is called an herb; but an herb may have a 
woody or perennial root, in which case it is called an 
herbaceous perennial. Annual plants are classed as herbs. 
Examples of herbaceous perennials are buttercups, bleed- 
ing heart, violet, waterlily, Bermuda grass, horse-radish, 
dock, dandelion, goldenrod, asparagus, rhubarb, many 
wild sunflowers (Figs. 11, 12). 

Many herbaceous perennials have short generations. 
They become weak with one or two seasons of flowering 
and gradually die out. Thus, red clover usually begins to 
fail after the second year. Gardeners know that the best 
bloom of hollyhock, larkspur, pink, and many other plants, 
is secured when the plants are only two or three years 
old. 

Herbaceous perennials which die away each season to 
bulbs or tubers, are sometimes called pseud-annuals (that 



I8 



BEGINNERS' BOTANY 



is, jalse annuals). Of such are lily, crocus, onion, potato, 
and bull nettle. 

True annuals reach old age the first year. Plants which 
are normally perennial may become annual in a shorter- 
season clhnate by being killed by frosty rather than by dying 
naturally at the end of a season of growth. They are cli- 
matic annuals. Such plants are called plur-annuals in the 
short-season region. Many tropical perennials are plur- 




Fig. 13. — a Shrub or Bush. Dogwood osier. 

annuals when grown in the north, but they are treated as 
true annuals because they ripen sufficient of their crop the 
same season in which the seeds are sown to make them 
worth cultivating, as tomato, red pepper, castor bean, 
cotton. Name several vegetables that are planted in 
gardens with the expectation that they will bear till frost 
comes. 

Woody or ligneous plants usually live longer than 
herbs. Those that remain low and produce several or 



THE PLANT BODY 



19 






many similar shoots from the 
base are called shrubs, as lilac, 
rose, elder, osier (Fig. 13). Low 
and thick shrubs are bushes. 
Plants that produce one main 
trunk and a more or less elevated 
head are trees (Fig. 14). All 
shrubs and trees are perennial. 
Every plant makes an effort 



to propagate^ or to perpetuate its :^-^i^'$4 
kind ; and, as far as we can Biff^f; 
see, this is the end for which 
the plant itself lives. The seed 
or spore is the final product of 
the plaftt. 




Fig. 14. — a Tree. 
birch. 



The weeping 



Suggestions. — 8. The teacher may assign each pupil to one 
plant in the school yard, or field, or in a pot, and ask him to bring 
out the points in the lesson. 9. The teacher may put on the 
board th€ names of many common plants and ask the pupils to 
classify into annuals, pseud-annuals, plur-annuals (or climatic 
annuals), biennials, perennials, herbaceous perennials, ligneous 
perennials, herbs, bushes, trees. Every plant grown on the farm 
should be so classified : wheat, oats, corn, buckwheat, timothy, 
strawberry, raspberry, currant, tobacco, alfalfa, flax, crimson clover, 
hops, cowpea, field bean, sweet potato, peanut, radish, sugar-cane, 
barley, cabbage, and others. Name all the kinds of trees you 
know. 




CHAPTER VI 

SEEDS AND GERMINATION 

The seed contains a miniature plant, or embryo. The 
embryo usually has three parts that have received 
names : the stemlet, or caulicle ; the seed-leaf, or cotyledon 
(usually I or 2) ; the bud, or plumule, lying between or 
above the cotyledons. These parts are well 
seen in the common bean (Fig. 15), particu- 
larly when the seed has been soaked for a 
few hours. One of the large cotyledons — 
OF THE Bean, comprising half of the bean — is shown at 
/?, cotyledon; <7, R. The cauliclc is at O, The plumule is 
mutf i^'fim shown at A, The cotyledons are attached 
nod*- to the caulicle at F: this point may be taken 

as the first node or joint. 

The Number of Seed-leaves. — All plants having two 
seed-leaves belong to the group called dicotyledons. Such 
seeds in many cases split readily in halves, e.g, a. bean. 
Some plants have only one seed-leaf in a seed. They 
form a group of plants called monocotyledons. Indian 
corn is an example of a plant with only one seed-leaf: 
a grain of corn does not split into halves as a bean does. 
Seeds of the pine family contain more than two cotyledons, 
but for our purposes they may be associated with the dicoty- 
ledons, although really forming a different group. 

These two groups — the dicotyledons and the mono- 
cotyledons — represent two great natural divisions of the 
vegetable kingdom. The dicotyledons contain the woody 

20 



SEEDS AXD GEI:MI NATION 21 

bark-bearing trees and bushes (except conifers), and most 
of the herbs of temperate climates except the grasses, 
sedges, rushes, lily tribes, and orchids. The flower-parts 
are usually in fives or multiples of five, the leaves mostly 
netted-veined, the bark or rind distinct, and the stem often 
bearing a pith at the centre. The monocotyledons usually 
have the flower-parts in threes or multiples of three, the 
leaves long and parallel-veined, the bark not separable, 
and the stem without a central pith. 

Every seed \^ provided zvith food \o support the germinat- 
ing plant. Commonly this food is starch. The food may 
be stored in the cotyledons^ as in bean, pea, squash ; or out- 
side the cotyledojiSf as in castor bean, pine, Indian corn. 
When the food is outside or around the embryo, it is 
usually called endosperm. 

Seed-coats; Markings on Seed. — The embryo and en- 
dosperm are inclosed within a covering made of two or 
more layers and known as the seed-coats. 
Over the point of the caulicle is a minute 
hole or a thin place in the coats known as 
the micropyle. This is the point at which fig.i6.— exter- 
the pollen-tube entered the forming ovule nal parts op 
and through which the caulicle breaks in 
germination. The micropyle is shown at M in Fig. i6. 
The scar where the seed broke from its funiculus (or stalk 
that attached it to its pod) is named the hilum. It occu- 
pies a third of the length of the bean in Fig. i6. The 
hilum and micropyle are always present in seeds, but they 
are not always close together. In many cases it is difficult 
to identify the micropyle in the dormant seed, but its loca- 
tion is at once shown by the protruding caulicle as germi- 
nation begins. Opposite the micropyle in the bean (at the 
other end of the hilum) is an elevation known as the raphe. 




22 BEGINNERS' BOTANY 

This is formed by a union of the funiculus, or seed-stalk, 
with the seed-coats, and through it food was transferred 
for the development of the seed, but it is now functionless. 

Seeds differ wonderfully in size, shape, colour, and other 
characteristics. They also vary in longevity. These 
characteristics are peculiar to the species or kind. Some 
seeds maintain life only a few weeks or even days, whereas 
others will "keep" for ten or twenty years. In special 
cases, seeds have retained vitality longer than this limit, 
but the stories that live seeds, several thousand years old, 
have been taken from the wrappings of mummies are un- 
founded. 

Germination. — The embryo is not dead ; it is only dor- 
mant. When supplied with moisture^ warmth^ and oxygen 
{air\ it awakes and grows : this growth is germination. 
The embryo lives for a time on the stored food, but gradu- 
ally the plantlet secures a foothold in the soil and gathers 
food for itself. When the plantlet is finally able to shift 
for its elf y germination is complete. 

Early Stages of Seedling. — The germinating seed first 
absorbs water ^ and swells. The starchy matters gradually 
become soluble. The seed-coats are ruptured, the caulicle 
and plumule emerge. During this process the seed 
respires freely, throwing off carbon dioxide (COo). 

The caulicle usually elongates, and from its lower end 
roots are emitted. The elongating caulicle is known as 
the hypocotyl ("below the cotyledons"). That is, the 
hypocotyl is that part of the stem of the plantlet lying 
between the roots and the cotyledon. The general direc- 
tion of the young hypocotyl^ or emerging caulicle, is down- 
wards. As soon as roots form, it becomes fixed and its 
subsequent growth tends to raise the cotyledons above the 
ground, as in the bean. When cotyledons rise into the 



SEEDS AND GERMINATION 



23 




Fig. 17. — Pea. Grotesque forms assumed 
when the roots cannot gain entrance to 
the soil. 



air, germination is said to be epigeal (" above the earth "). 
Bean and pumpkin are examples. When the hypocotyl 
does not elongate greatly 
and the cotyledons remain 
under ground, the germin- 
ation is hypogeal (''be- 
neath the earth"). Pea 
and scarlet runner bean 
are examples (Fig. 48). 
When the germinating 
seed lies on a hard sur- 
face, as on closely com- 
pacted soil, the hypocotyl 
and rootlets may not be able to secure a foothold and they 
assume grotesque forms (Fig. 17). Try this with peas and 
beans. 

The first internode (" between nodes ") above the coty- 
ledons is the epicotyl. It elevates the plumule into the 
air, and the plumule- leaves expand into the first true leaves 
of the plant. These first true leaves, however, may be 
very unlike the later leaves in shape. 

Germination of Bean. — The common bean, as we have 
seen (Fig. 15), has cotyledons that occupy all the space 
inside the seed-coats. When the hy- 
pocotyl, or elongated caulicle, emerges, 
the plumule-leaves have begun to en- 
large, and to unfold (Fig. 18). The 
hypocotyl elongates rapidly. One end 
of it is held by the roots. The other 
is held by the seed-coats in the soil. 
It therefore takes the form of a loop, 
and the central part of the loop " comes up " first {a. Fig. 
19). Presently the cotyledons come out of the seed-coats, 




Fig. 18. — Cotyledons 
OF Germinating 
Bean spread apart 

TO SHOW ELONGAT- 

ING Caulicle and 
Plumule. 



M 



BEGINNEKS* BOTAMY 




and the plant straightens and the 
cotyledons expand. These coty- 
ledons, or " halves of the bean," 
persist for some time {by Fig. 
19). They often become green 
and probably perform some 
function of foliage. Because of 
its large size, the Lima bean 
shows all these parts well. 

Germination of Castor Bean. — 
In the castor bean the hilum 
and micropyle are at the smaller end 
(Fig. 20). The bean " comes up " with a 
loop, which indicates that the hypocotyl 
greatly elongates. On examining germin- 
ating seed, however, it will be found 
that the cotyledons are contained inside a fleshy body, 
or sac {a, Fig. 2 1 ). This sac is the endosperm. Against 
its inner surface the thin, veiny coty- 
ledons are very closely pressed, ab- 



FiG. 19. — Germination of 
Bean. 



Fig. 20. — Sprout^ 
ING OF Castor 
Bean. 




Fig. 21.— Germina- 
tion OF Castor Bean. 

Endosperm at a. 



Fig. 22. — Castor 
Bean. 

Endosperm at a,n\ coty- 
ledons at b. 




Fig. 23. — Germination 
Complete in Castor 
Bean. 



sorbing its substance (Fig. 22). The cotyledons increase 
in size as they reach the air (Fig. 23), and become func- 
tional leaves. 



SEEDS AND GERMINATION 



25 



Germination of Monocotyledons. — Thus far we have stud- 
ied dicotyledonous seeds ; we may now consider the mono- 
cotyledonous group. Soak kernels of corn. Note that 
the micropyle and hilum are at the smaller end (Fig. 24). 
Make a longitudinal section through the 
narrow diameter; Fig. 25 shows it. The 





Fig. 24. — Sprout- 
ing Indian Corn. 

Hilum at h; micro* 
pyle at d. 



Fig. 25. — Kernel 
OF Indian Corn. 

Caulicle at b; cotyle- 
don at a; plumule 
at/. 




Fig. 26.— Indian 
Corn. 

Caulicle at c, roots emerging at 
ni; plumule at/. 



single cotyledon is at ^, the caulicle at b, the plumule 
at/. The cotyledon remains in the seed. The food is 
stored both in the cotyledon and as endosperm, chiefly the 
latter. The emerging shoot is the plumule, with a sheath- 
ing leaf (/, Fig. 26). The root is emitted from the tip of 
the caulicle, c. The caulicle is held in a sheath 
(formed mostly from the seed-coats), and some of 
the roots escape through the upper end 
of this sheath {m, Fig. 26). The 
^ yr epicotyl elongates, particularly if 
'Vfj^ the seed is planted 

deep or if it is 
kept for a time 
confined. In Fig. 
27 the epicotyl has 
elongated from n to p. The true plumule-leaf is at o, but 
other leaves grow from its sheath. In Fig. 28 the roots 
are seen emerging from the two ends of the caulicle- 




Fig. 27. — Indian Corn. 

o, plumule; n to/, epicotyl. 



26 



BEGINNERS' BOTANY 



sheath, r, m ; the epicotyl has grown to / ; the first plu- 
mule-leaf is at o. 

In studying corn or other fruits or seeds, the pupil should 
note how the seeds are arranged, as on the cob. Count the 

rows on a corn cob. Odd or 
even in number .-' Always the 
same number.'* The silk is 
the style: find where it was 
attached to the kernel. Did 
the ear have any coverings } 
Explain. Describe colours and 
markings of kernels of corn ; 
and of peas, beans, castor 
bean. 

Gymnosperms. — The seeds 
in the pine cone, not being 
inclosed in a seed-vessel, 
readily fall out when the cone 
dries and the scales separate. 
Hence it is difficult to find 
cones with seeds in them after 
autumn has passed (Fig. 29). 
The cedar is also a gymno- 
sperm. 

Remove a scale from a 
pine cone and draw it and 
the seeds as they lie in place 
on the upper side of the scale. 
Examine the seed, preferably with a magnifying glass. Is 
there a hilum } The micropyle is at the bottom or little 
end of the seed. Toss a seed upward into the air. Why 
does it fall so slowly ? Can you explain the peculiar whirl- 
ing motion by the shape of the wing } Repeat the ex- 




FiG. 28. — Germination is Com 

PLETE. 

/, top of epicotyl ; o, plumule-leaf; 
m, roots; c, lower roots. 



SEEDS AND GERMINATION' 



n 



periment in the wind. Remove the 
wing from a seed and toss it and an 
uninjured seed into the air together. 
What do you infer from these ex- 
periments "i 

Suggestions. — Few subjects con- 
nected with the study of plant-life are so 
useful in schoolroom demonstrations as 
germination. The pupil should prepare 
the soil, plant the seeds, water them, and 
care for the plants. 10. Plant seeds in 
pots or shallow boxes. The box should 
not be very wide or long, and not over 
four inches deep. Holes may be bored 
in the bottom so it will not hold water. 
Plant a number of squash, bean, corn, 
pine, or other seeds about an inch deep 
in damp sand or pine sawdust in this 
box. The depth of planting should be 
two to four times the diameter of the 
seeds. Keep the sand or sawdust moist 
but not wet. If the class is large, use 
several boxes, that the supply of speci- 
mens may be ample. Cigar boxes and 
chalk boxes are excellent for individual 
pupils. It is well to begin the planting 
of seeds at least ten days in advance of 
the lesson, and to make four or five differ- 
ent plantings at intervals. A day or two 
before the study is taken up, put seeds 
to soak in moss or cloth. The pupil 
then has a series from swollen seeds to 

complete germination, and all the steps can be made out. Dry 
seeds should be had for comparison. If there is no special room 
for laboratory, nor duplicate apparatus for every pupil, each ex- 
periment may be assigned to a committee of two pupils to watch 
in the schoolroom. 11. Good seeds for study are those detailed 
in the lesson, and buckwheat, pumpkin, cotton, morning glory, 
radish, four o'clock, oats, wheat. It is best to use familiar seeds 
of farm and garden. Make drawings and notes of all the events 
in the germination. Note the effects of unusual conditions, as 
planting too deep and too shallow and different sides up. For 
hypogeal germination, use the garden pea, scarlet-runner, or Dutch 




Fig. 29. — Cones of Hem- 
lock (above), White 
Pine, Pitch Pine. 



28 



BEGINNEL'S' BOTANV 



case-knife bean, acorn, horse-chestnut. Squash seeds are excellent 
for germination studies, because the cotyledons become green and 
leafy and germination is rapid. Onion is excellent , except that it 
germinates too slowly. In order to study the root development of 
germinating plantlets, it is well to provide a deeper box with a glass 
side against which the seeds are planted. 12- Observe the germina- 
tion of any common seed about the house premises. When elms, oaks, 
pines, or maples are abundant, the germination of their seeds may 
be studied in lawns and along fences. 13. When studying germina- 
tion the pupil should note the differences in shape and size between 
cotyledons and plumule leaves, and between plumule leaves and the 
normal leaves (Fig. 30). Make drawings. 14. Make the tests de- 
scribed in the introductory experiments with bean, corn, the castor 
bean, and other seed for starch and proteids. Test flour, oatmeal, 

rice, sunflower, four o'clock, 
various nuts, and any other 
seeds obtainable. "Record your 
results by arranging the seeds 
in three classes, 1. Much starch 
(colour blackish or purple). 2. 
Little starch (pale blue or 
greenish), 3. No starch (brown 
or yellow). 15- Bate of 
growth of seedlings as affect- 
ed by differences in tempera- 
ture. Pack soft wet paper to the depth of an inch in the bottom of 
four glass bottles or tumblers. Put ten soaked peas or beans into 
each. Cover each securely and set them in places having different 
temperatures that vary little. (A furnace room, a room with a stove, 
<i room without stove but reached by sunshine, an unheated room 
not reached by the sun). Take the temperatures occasionally , with the 
thermometer to find difference in temperature. The tumblers in 
vrarm places should be covered very tightly to prevent the germination 
from being retarded by drying out. Record the number of seeds 
which sprout in each tumbler within 1 day, 2 days, 3 days, 4 days, 
etc. 16. Ifi oir necessary for tJie germination and grorvth of seed- 
lings? Place damp blotting paper in the bottom of a bottle and 
fill it three-fourths full of soaked seeds, and close it tightly with a 
rubber stopper or oiled cork. Prepare a ''check experiment" by 
having another bottle -v^-ith all conditions the same except that it 
is covered loosely that air may have access to it, and set the bottles 
side by side (why keep the bottles together?). Record results as in the 




Fig. 30. — MusKMELON Seedlings, with 
the unlike seed-leaves and true leaves. 



HEEBS AND GERMINATION ^^ 

preceding experiment. 17- What is the nature of the gas given off 
by germinating seeds F Fill a tin box or large-necked bottle with 
dry beans or peas,then add water ; note how much they swell- Secure 
two fruit jars. Fill one of them a third full of beans and keep them 
moist. Allow the other to remain empty. In a day or two insert 
a lighted splinter or taper into each. In the empty jar the taper 
burns: it contains oxygen. In the seed jar the taper goes out: the 
air has been replaced by carbon dioxide. The air in the bottle may 
be tested for carbon dioxide by removing some of it with a rubber 
bulb attached to a glass tube (or a fountain-pen filler) and bubbling 
it through lime water. 18- Temperature. Usually there is a percep- 
tible rise in temperature in a mass of germinating seeds. This rise 
may be tested with a thermometer. 19. Interior of seeds. Soak 
seeds for twenty-four hours and remove the coat. Distinguish the 
embryo from the endosperm. Test with iodine. 20- Of ivhat utility 
is the food in seeds? Soak some grains of corn overnight and re- 
move the endosperm, being careful not to injure the fleshy cotyledon. 
Plant the incomplete and also some complete grains in moist sawdust 
and measure their growth at intervals. (Boiling the sawdust will 
destroy moulds and bacteria which might interfere with experiment.) 
Peas or beans may be sprouted on damp blotting paper; the coty- 
ledons of one may be removed, and this with a normal seed equally 
advanced in germination may be placed on a perforated cork floating 
in water in a jar so that the roots extend into the water. Their 
growth may be observed for several weeks. 21. Effect of darTcness on 
seeds and seedlings. A box may be placed mouth downward over 
a smaller box in which seedlings are growing. The empty box should 
rest on half-inch blocks to allow air to reach the seedlings. Note 
any effects on the seedlings of this cutting off of the light. An- 
other box of seedlings not so covered may be used as a check. Lay 
a plank on green grass and after a week note the c"hange that takes 
place beneath it. 22. Seedling of jtine- Plant pine seeds. Notice 
how they emerge. Do the cotyledons stay in the ground? How many 
cotyledons have they? When do the cotyledons get free from the 
seed-coat? What is the last part of the cotyledon to become free? 
Where is the growing point or plumule? How many leaves appear at 
once? Does the new pine cone grow on old w^ood or on wood formed 
the same spring with the cone? Can you always find partly grown 
cones on pine trees in winter? Are pine cones when mature on two- 
year-old wood? How long do cones stay on a tree after the seeds 
have fallen out? What is the advantage of the seeds falling before 
the cones? 23. Home experiments. If desired, nearly all of the fore- 




30 BEGINNEBS' BOTANY 

going experiments may be tried at home. The pupil can thus make 
the drawings for the notebook at home- A daily record of measure- 
ments of the change in size of the various parts of the seedliiig 
should also be made. 24. Seed-testing. — It is important that one 
know before planting whether seeds are good, or able to grow. A 
simple seed-tester may be made of two plates, one inverted over the 
other (Fig. 31). The lower plate is nearly filled with clean sand, 
which is covered with cheese cloth or blot- 
ting paper on which the seeds are placed. 
Canton flannel is sometimes used in place, 
of sand and blotting paper. The seeds are 
then covered with another blotter or piece 
of cloth, and water is applied until the 
sand and papers are saturated. Cover with 
the second plate. Set the plates where they 
will have about the temperature that the 
Fig. 31. — a Home-made given seeds would require out of doors, or 
Seed-tester. perhaps a slightly higher temperature. 

Place 100 or more grains of clover, corn, 
wheat, oats, rye, rice, buckwheat, or other seeds in the tester, and 
keep record of the number that sprout. The result will give a per- 
centage measure of the ability of the seeds to grow. Note whether 
all the seeds sprout with equal vigour and rapidity. Most seeds 
will sprout in a week or less. Usually such a tester must have fresh 
sand and paper after each test, for mould fungi are likely to breed 
in it. If canton flannel is used, it may be boiled. If possible, the 
seeds should not touch one another. 

Note to Teacher. — With the study of germination, the pupil 
will need to begin dissecting. 

For dissecting, one needs a lens for the examination of the 
smaller parts of plants and animals. It is best to have the lens- 
mounted on a frame, so that the pupil has both hands free for 
pulling the part in pieces. An ordinary pocket lens may be mount- 
ed on a wire in a block as in Fig. A. A cork is slipped on the 
top of the wire to avoid injury to the face. The pupil should be 
provided with two dissecting needles (Fig. B), made by securing 
an ordinary needle in a pencil-like stick. Another convenient ar- 
rangement is shown in Fig. C. A small tin dish is used for the 
base. Into this a stiff wire standard is soldered. The dish is filled 
with solder to make it heavy and firm. Into a cork slipped on the 
standard, a cross wire is inserted, holding on the end a jeweller's 



SEEDS AND GERMINATION 



31 



glass.* The lens can be moved up and down and sidewise. This 
outfit can be made for about seventy-five cents. Fig. D shows 
a convenient hand-rest or uissecting-stand to be used under this 
lens. It may be 16 in. long, 4 in. high, and 4 or 5 in. broad. 

Various kinds of dissecting microscopes are on the market, and 
these are to be recommended when they can be afforded. 




A— Dissecting Stand. 




5. — Dis- 
secting 
Needle 
% natural 
si2e. 





C — Dissecting Glass. 



^. — Improvised 
Stand for Lens, 



Instructions for the use of the compound microscope, with 
which some schools may be equipped, cannot be given in a brief 
space; the technique requires careful training. Such microscopes 
are not needed unless the pupil studies cells and tissues. 



CHAPTER VII 

THE ROOT — THE FORMS OF ROOTS 

The Root System. — The offices of the root are to hold 
the plant in place, and to gather food. Not all the food 
materials, however, are gathered by the roots. 




Fig. 32. — Tap-root 
System of Alfalfa. 




Tap-root of the Dandelion. 



Fig. 33. 

The entire mass of roots of any plant is called its root 
system. The root system may be annual, biennial or peren- 
nial, herbaceous or woody, deep or shallow, large or small. 

Kinds of Roots. — A strong leading central root, which 
runs directly downwards, is a tap-root The tap-root forms 



THE ROOT— THE FORMS OF ROOTS 



33 



an axis from which the side roots may branch. The side 
or spreading roots are usually smaller. Plants that have 
such a root system are said to be tap-rooted. Examples 
are red clover, alfalfa, beet, turnip, 
radish, burdock, dandelion, hickory 
(Figs. 32, 33). 

A fibrous root system is one that 
is composed of many nearly equal 
slender branches. The greater 
number of plants have fibrous roots. 
Examples are many common 
grasses, wheat, oats, corn. The 
buttercup in Fig. 34 has a fibrous 
root system. Many trees have a 
strong tap-root when very young, 
but after a while it ceases to ex- 
tend strongly and the side roots 
develop until finally the tap-root 
character disappears. 

Shape and Extent of the Root Sys- 
tem. — The depth to which roots 
extend depends on the kind of plant, and the natJire of the 
soil. Of most plants the roots extend far in all-directions 
and lie comparatively near the surface. The roots usually 
radiate from a common point just beneath the surface of 
the ground. 

The roots grow here and there in search of foody often 
extending much farther in all directions than the spread 
of the top of the plant. Roots tend to spread farther in 
poor soil than in rich soil, for the same size of plant. 
The root has no such defi^iite form as the stem has. Roots 
are usually very crooked, because they are constantly 
turned aside by obstacles. Examine roots in stony soil. 




Fig. 34. — a Buttercup 
Plant, with fibrous roots. 



34 



BEGINNERS* BOTANY 



The extent of root surface is usually very large, for the 
feeding roots are fine and very numerous. An ordinary 
plant of Indian corn may have a total length of root 
(measured as if the roots were placed end to end) of several 
hundred feet. 

The fine feeding roots are most abundant in the richest 
part of the soil. They are attracted by the food materials. 
Roots often will completely surround a bone or other 
morsel. When roots of trees are exposed, observe that 
most of them are horizontal and lie near the top of the 
ground. Some roots, as of willows, extend far in search 
of water. They often run into wells and drains, and into 
the margins of creeks and ponds. Grow plants in a long 
narrow box, in one end of which the soil is kept very dry 
and in the other moist : observe where the roots grow. 

Buttresses. — With the increase in diameter, the upper 
roots often protrude above the ground and become bracing 
buttresses. These buttresses are usually largest in trees 

which always have been 
exposed to strong winds 
(Fig. 35). Because of 
growth and thickening, 
the roots elevate part of 
their diameter, and the 
washing away of the soil 
makes them to appear as 
if having risen out of 
the ground. 

Aerial Roots. — Although roots usually grow underground, 
there are some that naturally grow above ground. These 
usually occur on climbing plants, the roots becoming stip- 
ports or fulfilling the office of tendrils. These aerial roots 
usually turn away from the light, and therefore enter the 




^a5s^^ 



Fig. 35. — The Bracing Base of a 
Field Pine. 



THE ROOT— THE EORMS OF ROOTS 



35 



crevices and dark places of the wall or tree over which the 



plant 



climbs. 




The trumpet creeper (Fig. 36), true or 
English ivy, and poison ivy climb by 
means of roots. 




Fig. 37. — Aerial Roots of an Orchid. 

In some plants all the roots are 
aerial ; that is, the plant grows above 
ground^ and the roots gather food 
from the air. Such plants usually 
grow on trees. They are known as 
epiphytes or air-plants. The most fam- 
iliar examples are some of the tropi- 
cal orchids which are grown in glass- 
houses (Fig. 37). Rootlike organs of dodder and other 
parasites are discussed in a future chapter. 



Fig. 36. — Aerial Roots 
OF Trumpet Creeper 
OR Tecoma. 



36 



BEGINNERS' BOTANY 



Some plants bear aerial roots, that may propagate the 
plant or may act as braces. They are often called prop-roots. 
The roots of Indian corn are familiar (Fig. 38). Many 
ficus trees, as the banyan of India, send out roots from 
their branches ; when these roots reach the ground they 
take hold and become great trunks, thus spreading the 
top of the parent tree over large 
areas. The mangrove tree of the 
tropics grows along seashores and 
sends down roots from the over- 
hanging branches (and from the 
fruits) into the shallow water, and 
thereby gradually marches into the 
sea. The tangled mass behind catch- 
es the drift, and soil is formed. 

Adventitious Roots. — Sometimes 
roots grow from the stem or other 
unusual places as the result of some 
accident to the plant, being located 
without known method or law. They 
are called adventitious (chance) 
roots. Cuttir!igs of the stems of 
roses, figs, geraniums, and other 
plants, when planted, send out ad- 
ventitious roots and form new 
plants. The ordinary roots, or soil roots, are of course not 
classed as adventitious roots. The adventitious roots arise 
on occasion, and not as a normal or regular course in the 
growth of the plant. 

No two roots are alike; that is, they vary among them- 
selves as stems and leaves do. Eacli JHnd of plant has its 




Fig. 38. — Indian Corn, 
showing the brace roots 
at 00. 



THE ROOT— THE FORMS OF ROOTS 



37 



own form or habit of root (Fig. 39). Carefully wash awa^ 
the soil from the roots of any two related plants, as oats 
and wheat, and note the differences in size, depth, direc- 
tion, mode of branching, num- 
ber of fibrils, colour, and other 





Fig. 39. — Roots of Bari.ey at A and Corn at B. 
Carefully trace the differences. 

features. The character of the root system often governs 
the treatment that the farmer should give the soil in which 
the plant or crop grows. 

Roots differ not only in their form and habit, but also in 
colour of tissue, character of bark or rind, and other fea- 
tures. It is excellent practice to fry to identify different 
plants by means of their roots. Let each pupil bring to 
school two plants with the roots very carefully dug up, as 
cotton, corn, potato, bean, wheat, rye, timothy, pumpkin, 
clover, sweet pea, raspberry, strawberry, or other common 
plants. 

Root Systems of Weeds. — Some weeds are pestiferous 
because they seed abundantly, and others because their 
underground parts run deep or far and are persistent. 
Make out the root systems in the six worst weeds in your 
locality. 



CHAPTER VIII 



THE ROOT. — FUNCTION AND STRUCTURE 



The function of roots is twofold, — to provide support or 
anchorage for the plant, and to collect and convey food ma- 
terials. The first function is considered in Chapter VII; 
we may now give attention in more detail to the second. 

The feeding surface of the roots 
is near their ends. As the roots 
become old and hard, they serve 
only as channels through which 
food passes and as holdfasts or 
supports for the plant. The root- 
hold of a plant is very strong. 
Slowly pull upwards on some plant, 
and note how firmly it is anchored 
in the soil. 

Roots have power to choose their 
food; that is, they do not absorb 
all substances with which they 
come in contact. They do not take 
up great quantities of useless or 
harmful materials, even though 
these materials may be abundant in the soil ; but they 
may take up a greater quantity of some of the plant-foods 
than the plant can use to advantage. Plants respond very 
quickly to liberal feeding, — that is, to the application of 
plant-food to the soil (Fig 40). The poorer the soil, the 
more marked are the results, as a rule, of the application 

38 




Fig. 40.-— Wheat growing 
under diffkkent soil 
Treatments. Soil defi- 
cient in nitrogen; com- 
mercial nitrogen applied 
to pot 3 (on right). 



THE ROOT— FUNCTION AND STRUCTURE 39 

of fertilizers. Certain substances, as common salt, will kill 
the roots. 

Roots absorb Substances only in Solution. — Substances 
cannot be taken in solid particles. These materials are 
in solution in the soil water, and the roots themselves 
also have the power to dissolve the soil materials to some 
extent by means of substances that 
they excrete. The materials that 
come into the plant through the 
roots are water and mostly the min- 
eral substances^ as compounds of po- 
tassium, iron, phosphorus; calcium, 
magnesium, sulphur, and chlorine. 
These mineral substances compose 
the ash when the plant is burned. 
The carbon is derived from the air 
through the green parts. Oxygen 
is derived from the air and the soil 
water. 

Nitrogen enters through the Roots. 

— All plants must have nitrogen; 

yet, although about four-fifths of F1G.41. — Nodules on roots 
., . . .^ , ^ ^ OF Red /Clover. 

the air is nitrogen, plants are not 

able, so far as we know, to take it in through their leaves. 
It enters through the roots in combination with other ele- 
ments, chiefly in the form of nitrates (certain combinations 
with oxygen and a mineral base). The great family of 
leguminous plants, however (as peas, beans, cowpea, 
clover, alfalfa, vetch), use the nitrogen contained in the air 
in the soil. They are able to utilize it through the agency 
of nodules on their roots (Figs. 41, 42). These nodules 
contain bacteria, which appropriate the free or uncom- 
bined nitrogen and pass it on to the plant. The nitrogen 




40 



BEGIJVNEKS' BOTANY 




Fig. 42.— Nodules on Vetch. 



becomes incorporated in the plant tissue, so that these 
crops are high in their nitrogen content. Inasmuch as 

nitrogen in any form is 
expensive to purchase in 
fertiUzers, the use of legu- 
minous crops to plough un- 
der is a very important ag- 
ricultural practice in pre- 
paring the land for other 
crops. In order that legum- 
inous crops ma}' acquire at- 
mospheric nitrogen more 
freely and thereby thrive 
better, ihe land is sometimes 
soivn or inoculated icith the 
nodule-forming hacteria. 

Roots require moisture in order to serve the plant. The 
soil water that is valu- 
able to the plant is not 
the free water, but the 
t/iin film of moisture 
which adheres to each 
little particle of soil. The 
finer the soil, the greater 
the number of particles, 
and therefore the greater 
is the quantity of film 
moisture that it can hold. 
This moisture surround- 
ing the grains may not 
be perceptible, yet the 
plant can use it. Root absorption may continue in a soil 
which seems to be dust dry. Soils that are very hard and 




Fig. 43. — Two Kinds of Soil that have 
BEEN Wet and then Dried. The 
loamy soil above remains loose and capa- 
ble of growing plants; the clay soil below 
has baked and cracked. 



THE ROOT— FUNCTION AND STRUCTURE 



41 



"baked" (Fig. 43) contain very little moisture or air, — 
not so much as similar soils that are granular or mellow. 

Proper Temperature for Root Action. — The root must be 
warm in order to perform its functions. Should the soil of 
fields or greenhouses be much colder than the air, the 
plant suffers. When in a warm atmosphere, or in a dry- 
atmosphere, plants need to absorb much water from the 
soil, and the roots must be warm if the root-hairs are to 
supply the water as rapidly as it is needed. If the roots are 
chilled^ the plant may wilt or die. 

Roots need Air. — Corn on land that has been flooded by 
heavy rains loses its green colour and turns yellow. Besides 
diluting plant-food^ the water drives the air from the soily and 
this suffocation of the roots is very soon ap- 
parent in the general ill health of the plant. 
Stirring or tilling the soil aerates it. Water 
plants and bog plants have adapted them- 
selves to their particular conditions. They 
get their air either by special surface roots, 
or from the water through stems and leaves. 

Rootlets. — Roots divide into the thinnest 
and finest fibrils : there are roots and there 
are rootlets. The smallest rootlets are so 
slender and delicate that they break off 
even when the plant is very carefully lifted 
from the soil. 

The rootlets^ or fi7te divisions^ ai^e clothed with the root- 
hairs (Figs. 44, 45, 46). These root-hairs attach to the 
soil particles y and a great amount of soil is thus brought 
into actual contact with the plant. These are very deli- 
cate prolonged surface cells of the roots. They are borne 
for a short distance just back of the tip of the root. 

Rootlet and root-hair differ. The rootlet is a compact 




Fig. 44. — Root- 
hairs OF THE 
Radish. 



42 



1, 



y 



BEGINNERS' BOTANY 




Fig. 45, — Cross-section of Root, 
enlarged, showing root-hairs. 



cellular structure. The root-hair is a delicate tub7ilaf 
cell (Fig. 45), within which is contained livifig- matter 

(protoplasm) ; and the protoplasmic lining niembrane of the 

wall governs the entrance of 
water and substances in solu- 
tion. Being long and tube- 
like, these root-hairs are 
especially adapted for tak- 
ing in the largest quantity 
of solutions; and they are 
the principal means by which 
plant-food is absorbed from 
the soil, although the sur- 
faces of the rootlets them- 
selves do their part. Water 
plants do not produce an 

abundant system of root-hairs, and such plants depend 

largely on their rootlets. 

The root-hairs are very small, often invisible. They, 

with the young roots, are usually broken off when the 

plant is pulled up. They are 

best seen when seeds are germin- 
ated between layers of dark 

blotting paper or flannel. On 

the young roots they will be 

seen as a mould-like or gossamer- 
like covering. Root-hairs soon 

die : they do not grow into roots. 

New ones form as the root grows. 
Osmosis. — The water with its 

nourishment goes through the 

thin walls of the root-hairs and rootlets by the process 

of osmosis. If there are two liquids of different density 




Fig. 46. — RooT-HAiR, much en- 
larged, in contact with the soil 
particles (j) . Air-spaces at a \ 
water-films on the particles, as 
at w. 



THE ROOT— FUNCTION AND STRUCTURE 43 

on the inside and outside of an organic (either vegetable 
or animal) membrane, the liquids tend to mix through the 
membrane. The law of osmosis is that the most rapid 
flow is toward the denser solution. The protoplasmic lin- 
ing of the cell wall is such a membrane. The soil water 
being a weaker solution than the sap in the roots, the 
flow is into the root. A strong fertilizer sometimes causes 
a plant to wither, or "burns it." Explain. 

Structure of Roots. — The root that grows from the lower 
end of the caulicle is the first or primary root. Secondary 
roots branch from the primary root. Branches of second- 
ary roots are sometimes called tertiary roots. Do the sec- 
ondary roots grow from the cortex, or from the central 
cylinder of the primary root.^ Trim or peel the cortex 
from a root and its branches and determine whether the 
branches still hold to the central cylinder of the main root. 

Internal Structure of Roots. — A section of a root shows 
that it consists of a central cylinder (see Fig. 45) sur- 
rounded by a layer. This layer is called the cortex. The 
outer layer of cells in the cortex is called the epidermis, 
and some of the cells of the epidermis are prolonged 
and form the delicate root-hairs. The cortex resembles 
the bark of the stem in its nature. The central cylinder 
contains many tube-Hke canals, or " vessels " that convey 
water and food (Fig. 45). Cut a sweet potato across (also 
a radish and a turnip) and distinguish the central cylin- 
der, cortex, and epidermis. Notice the hard cap on the tip 
of roots. Roots differ from stems in having no real pith. 

Microscopic Structure of Roots. — Near the end of any 
young root or shoot the cells are found to differ from one an- 
other more or less, according to the distance from the 
point. This diffei'entiation takes place in the region just 
back of the growing point. To study growing points, use 



44 



BEGINNERS* BOTANY 



the hypocotyl of Indian corn which has grown about one- 
half inch. Make a longitudinal section. Note these points 
(Fig. 47): {a) the tapering root-cap beyond the growing 
point ; {b) the blunt end of the root proper and the rec- 
tangular shape of the cells found there; {c) the group 
of cells in the middle of the first layers beneath the root- 
cap, — this group is the growing 
point; {d) study the sUght differ- 
ences in the tissues a short dis- 
tance back of the growing point. 
There are four regions : the central 
cylinder, made up of several rows 
of cells in the centre (//); the en- 
dodermis, (e) composed of a single 
layer on each side which separates 
the central cylinder from the bark ; 
the cortex, or inner bark, {e) of sev- 
eral layers outside the endodermis ; 
and the epidermis, or outer layer of 
bark on the outer edges {d). Make 
a drawing of the section. If a 
series of the cross-sections of the 
hypocotyl should be made and stud- 
ied by the pupil beginning near 
the growing point and going up- 
ward, it would be found that these four tissues become more 
distinctly marked, for at the tip the tissues have not yet 
assumed their characteristic form. The central cylinder 
contains the ducts and vessels which convey the sap. 

The Root-cap. — Note the form of the root-cap shown in 
the microscopic section drawn in Fig. 47. Growing cells, 
and especially those which are forming tissue by sub- 
dividing, are very deHcate and are easily injured. The 




Fig. 47. — Growing Point 
OF Root of Indian Corn. 

d, d, cells which will form the 
epidermis; /, /, cells that 
will form bark; <», ^, endoder- 
mis; //, cells which will form 
the axis cylinder; /, initial 
group of cells, or growing 
point proper; c, root-cap. 



THE ROOT-- FUNCTION AND STRUCTURE 



45 



cells forming the root-cap are older and 
tougher and are suited for pushing 
aside the soil that the root may pene- 
trate it. 

Region of most Rapid Growth. — The 
roots of a seedling bean may be marked 
at equal distances by waterproof ink or 
by bits of black thread tied moderately 
tight. The seedling is then replanted 
and left undisturbed for two days. 
When it is dug up, the region of most 
rapid growth in the 





Fig. 48. —The Mark- 
ing OF THE Stem 
AND Root. 



Fig. 49.— The Result 



root can be deter- 
mined. Give a reason why a root 
cannot elongate thfoiighoiit its length, 
— whether there is anything to pre- 
vent a young root from doing so. 

In Fig. 48 is shown a germinating 
scarlet runner bean with a short root 
upon which are marks made with 
waterproof ink; and the same root 
(Fig. 49) is shown after it has 
grown longer. Which part of it 
did not lengthen at all } Which 
part lengthened slightly .? Where 
is the region of most rapid growth.!* 
Geotropism. — Roots turn to- 
ward the earth, even if the seed 
is planted with the micropyle up. 
This phenomenon is called posi- 
tive geotropism. Stems grow away 
from the earth. This is negative 
geotropism. 



46 



BEGINNERS' BOTANY 



Suggestions (Chaps. VII and VIII). — 25. Tests for food. Ex- 
amine a number of roots, including several fleshy roots, for the 
presence of food material, making the tests used on seeds. 26. 
Study of root-hairs. Carefully germinate radish, turnip, cabbage, 
or other seed, so that no delicate parts of the root will be injured. 
For this purpose, place a few seeds in packing-moss or in the folds 
of thick cloth or of blotting paper, being careful to keep them moist 
and warm. In a few days the seed has germinated, and the root 
has grown an inch or two long. Notice that, except at a dis- 
tance of about a quarter of an inch behind the tip, the root is 
covered with minute hairs (Fig. 44). They are actually hairs; 
that is, root-hairs. Touch them and they collapse, they are so 
delicate. Dip one of the plants in water, and when removed the 
hairs are not to be seen. The water mats them together along 
the root and they are no longer evident. Root-hairs are usually 
destroyed when a plant is pulled out of the soil, be it done 
ever so carefully. They cling to the minute particles of soil 
(Fig. 46). The hairs show best against a dark background. 
27. On some of the blotting papers, sprinkle sand ; observe how 
the root-hairs cling to the grains. Observe how they are flat- 
tened when they come in contact with grains of sand. 28. Root 

hold of plant. The 
pupil should also 
study the root hold. 
Let him carefully pull 
up a plant. If a plant 
grow alongside a 
fence or other rigid 
object, he may test 
the root hold by se- 
curing a string to 
the plant, letting the 
string hang over the 
fence, and then add- 
ing weights to the 
string. Will a stake 
of similar size to the 
plant and extending 
no deeper in the 
ground have such 
firm hold on the soil? 
What holds the ball 
of earth in Fig. 50? 
29. Roots exert pressure. Place a strong bulb of hyacinth or 
daffodil on firm-packed earth in a pot ; cover the bulb nearly to 
the top with loose earth j place in a cool cellar ; after some days 




Fig, 50.— Th^ Grasp of a Plant on the Parti- 
cles OF Earth. A grass plant pulled in a garden. 



THE ROOT-^ FUNCTION AND STRUCTURE 



47 




Fig. 51.— 
Plant grow- 
ing IN In- 
verted Pot. 



or weeks, note that the bulb has been raised out of the earth by 
the forming roots. All roots exert pressure on the soil as they grow. 
Explain. 30. Response of roots and stems to the force of gravity^ 
or geotropism. Plant a fast-growing seedling in a 
pot so that the plumule extends through the drain 
hole and suspend the pot with mouth up {i.e. in 
the usual position). Or use a pot in which a plant 
is already growing, cover with cloth or wire gauze 
to prevent the soil from falling, and suspend the 
pot in an inverted position (Fig. 51). Notice the 
behaviour of the stem, and after a few days remove 
the soil and observe the position of the root. 31. If 
a pot is laid on one side, and changed every two 
days and laid on its opposite side, the effect on the 
root and stem will be interesting. 32. If a fleshy 
root is planted wrong end up, what is the result ? 
Try it with pieces of horse-radish root. 33. By 
planting radishes on a slowly revolving wheel the 
effectofgravity may be neutralized. 34. Region of 
root most sensitive to gravity. Lay on its side a pot containing a 
growing plant. After it has grown a few days, wash away the earth 
surrounding the roots. Which turned downward most decidedly, 
the tip of root or the upper part? 25. Soil texture. Carefully turn 
up soil in a rich garden or field so that you have unbroken lumps 
as large as a hen's tgg. Then break these lumps apart carefully 
^^^^^^^^^__^^____^^^_^_^______^_^^^^ with the fingers and 

/^^IS^^^^Sc^^lt^^^^^^l^'^r^^TT^ determine whether 

there are any traces 
or remains of roots 
(Fig. 52). Are there 
any pores, holes, or 
channels made by 
roots ? Are the roots 
in them still living? 
36. Compare an- 
other lump from a 
clay bank or pile 
where no plants 
have been growing. 
Is there any differ- 
ence in texture ? 37. Grind up this clay lump very fine, put it in 
a saucer, cover with water, and set in the sun. After a time it 
will have the appearance shown in the lower saucer in Fig. 43. 
Compare this with mellow garden soil. In which will plants grow 
best, even if the plant- food were the same in both ? Why ? 38. To 
test the effect of moisture on the plant, let a plant in a pot or box dry 




Fig. 52. — Holes in Soil made by Roots, now 
decayed. Somewhat magnified. 



48 BEGINNERS* BOTANY 

out till it wilts ; then add water and note the rapidity with which 
it recovers. Vary the experiment in quantity of water appUed. 
Does the plant call for water sooner when it stands in a sunny win- 
dow than when in a cool shady place? Prove it. 39. Immerse 
a potted plant above the rim of the pot in a pail of water and let 
it remain there. What is the consequence ? Why ? 40. To test 
the effect of temperature on roots. Put one pot in a dish of ice 
water, and another in a dish of warm water, and keep them in a 
warm room. In a short time notice how stiff and vigorous is the 
one whose roots are warm, whereas the other may show signs of 
wilting. 41. The process of osmosis. Chip away the shell from 
the large end of an egg so as to expose the uninjured membrane 
beneath for an area about as large as a ten-cent piece. With sealingr- 
wax, chewing-gum, or paste, stick a quill about three inches long to 
the smaller end of the ^^g. After the tube is in place, run a 
hat pin into it so as to pierce both shell and membrane ; or use 
a short glass tube, first scraping the shell thin with a knife and 
then boring through it with the tube. Now set the egg upon the 
mouth of a pickle jar nearly full of water, so that the large end 
with the exposed membrane is beneath the water. After several 
hours, observe the tube on top of the egg to see whether the water 
has forced its way into the egg and increased its volume so that 
part of its contents are forced up into the tube. If no tube is at 
hand, see whether the contents are forced through the hole which 
has been made in the small end of the egg. Explain how the law 
of osmosis is verified by your result. If the eggshell contained 
only the membrane, would water rise into it? If there were no 
water in the bottle, would the egg-white pass down into the bot- 
tle? 42. The region of most rapid growth. The pupil should 
make marks with waterproof ink (as Higgins' ink or indelible 
marking ink) on any soft growing roots. Place seeds of bean, 
radish, or cabbage between layers of blotting paper or thick cloth. 
Keep them damp and warm. When stem and root have grown 
an inch and a half long each, with waterproof ink mark spaces 
exactly one-quarter inch apart (Figs. 48, 49). Keep the plantlets 
moist for a day or two, and it will be found that on the stem some 
or all of the marks are more than one-quarter inch apart; on the 
root the marks have not separated. The root has grown beyond 
the last mark. 



CHAPTER IX 
THE STEM — KINDS AND FORMS; PRUNING 

The Stem System. — The stem of a plant is the part 
that bears the btids^ leaves^ flowers^ and fruits. Its office 
is io hold these parts up to the light and the air; and 
through its tissues the various food-materials and the life- 
giving fluids are distributed to the growing and working 
parts. 

The entire mass or fabric of stems of any plant is called 
its stem system. It comprises the trunk, branches, and 
twigs, but not the stalks of leaves and flowers that die and 
fall away. The stem system may be herbaceous or woody, 
annual, biennial, or perennial ; and it may assume many 
sizes and shapes. 

Stems are of Many Forms. — The general way in which 
a plant grows is called its habit. The habit is the appear- 
ance or general form. Its habit may be open or loose, 
dense, straight, crooked, compact, straggling, climbing, 
erect, weak, strong, and the like. The roots and the leaves 
are the important functional or ivoi'king parts ; the stem 
merely connects them, and its form is exceedingly variable. 

Kinds of Stems. — The stem may be so short as io be 
scarcely distinguishable. In such cases the crown of the 
plant — that part just at the surface of the ground — bears 
the leaves and the flowers ; hut this crown is really a very 
short stem. The dandelion, Fig. 33, is an example. Such 
plants are often said to be stemless, however, in order to 
distinguish them from plants that have long or conspic- 
E 49 



so 



BEGINNERS' BOTANY 



uous Stems. These so^alled stemless plants die to the 
ground every year. 

Stems are erect when they grow straight up (Figs. 53, 
54). They are trailing when they run along on the ground, 





Fig. 53. — Strict Simple 
Stem of Mullein. 



Fig. 54. — Strict Upright Stem 
OF Narrow-leaved Dock. 



as melon, wild morning-glory (Fig. 55). They are creep- 
ing when they run on the ground and take root at places, 




Fig. 55.— Trailing Stem of Wild Morning Glory {Convolvulus arvensis). 



as the strawberry. They are decumbent when they lop 
over to the ground. They are ascending when they lie 
mostly or in part on the ground but stand more or less 
upright at their ends; example, a tomato. They are 



THE STEMS— KINDS AND FORMS; PRUNING 



51 



climbiiig when they cling to other objects 
for support (Figs. 36, 56). 

Trees in which the main trunk or the 
** leader'* continues to grow from its tip 
are said to be excurrent in growth. The 
branches are borne along the sides of the 
trunk, as in common pines (Fig. 57) and 
spruces. Excurrent means running out or 
running up. 

Trees in which the main trunk does 
not continue are said to be deliques- 
cent. The brandies arise from 07ie 
common point or from each other. The 
stem is lost in the branches. The apple 
tree, plum (Fig. 58), maple, elm, oak, China 
tree, are familiar examples. Deliquescent 
means dissolving or melting away. 

Each kind of plant has its own peculiar 

habit or direction of growth. Spruces al- 

'ways grow to a single stem or trunk, pear 




Fig. 56. — a 

Climbing Plant 

(a twiner). 





Fig. 57. — Excurrent 
Trunk. A pine. 



Fig. 58. — Deliquescent Trunk 
OF Plum Tree. 



52 BEGINNERS' BOTANY 

trees are always deliquescent, morning-glories are always 
trailing or climbing, strawberries are always creeping. 
We do not know why each plant has its own habit, but 
the habit is in some way associated with the plant's gene- 
alogy or with the way in which it has been obliged to live. 

The stem may be simple or branched. A simple stem 
usually grows from the terminal bud, and side branches 
either do not start, or, if they start, they soon perish. 
Mulleins (Fig. 53) are usually simple. So are palms. 

Branched stems may be of very different habit and shape. 
Some stem systems are narrow and erect ; these are said 
to be strict (Fig. 54). Others are diffuse, open, branchy, 
twiggy. 

Nodes and Internodes. — The parts of the stem at which 
buds grow are called nodes or joints and the spaces be- 
tween the buds are internodes. The stem at nodes is 
usually enlarged, and the pith is usually interrupted. The 
distance between the nodes is influenced by the vigour of 
the plant : how } 




Fig. 59.— Rhizome or Rootstock. 

Stems vs. Roots. — Roots sometimes grow above ground 
(Chap. VII); so, also, stems sometimes gtoiv underground, 
and they are then known as subterranean stems, rhizomes, 
or rootstocks (Fig. 59). 

Stems normally bear leaves and buds, and thereby are 
they distinguished from roots; usually, also, they contain 
a pith. The leaves, however, may be reduced to mere 
scales, and the buds beneath them may be scarcely visible. 




THE STEMS— KINDS AND FORMS; PRUNING 53 

Thus the " eyes " on a white potato are cavities with a 
bud or buds at the bottom (Fig. 60). Sweet potatoes have 
no evident " eyes " when first dug, (but they may develop 
adventitious buds before the next grow- 
ing-season). The white potato is a stem : 
the sweet potato is probably a root. 

How Stems elongate. — Roots elongate 
by growing near the tip. Stems elon- 
gate by growijtg more or less throusrh- ^^^"' ^- ~ Sprouts 

^ -^ <^ ^ o ARISING FROM THE 

out the young or soft part or " between buds, or eyes, of a 
joints " (Figs. 48, 49). But any part P°'^'° '"^^'■• 
of the stem soon reaches a limit beyond which it cannot 
grow, or becomes "fixed"; and the new parts beyond 
elongate until they, too, become rigid. When a part of 
the stem once becomes fixed or hard, it never increases in 
length : that is, tJie trunk or woody parts never grow longer 
or higher ; branches do not become farther apart or higher 
from the ground. 

Stems are modified in form by the particular or incidental 
conditions under which they grow. The struggle for light 
is the chief factor in determining the shape and the direc- 
tion of any limb (Chap. II). This is well illustrated in any 
tree or bush that grows against a building or on the mar- 
gin of a forest (Fig. 4). In a very dense thicket the 
innermost trees shoot up over the others or they perish. 
Examine any stem and endeavour to determine why it took 
its particular form. 

The stem is cylindrical, the outer part being bark and 
the inner part being wood or woody tissue. In the dicoty- 
ledonous plants, the bark is usually easily separated from 
the remainder of the cyHnder at some time of the year ; in 
monocotyledonous plants the bark is not free. Growth in 
thickness takes place inside the covering and not on the very 



54 



BE G INNER S' BOTANY 




outside of the plant cylinder. It is evident, then, that the 
covering of bark must expandin order to allow of the expan- 
sion of the woody cylinder within it. The tis- 
sues, therefore, must be under constant pressure 
or tension. It has been determined that the 
pressure within a growing trunk is often as 
much as fifty pounds to the square inch. The 
lower part of the limb in Fig. 6i shows that 
the outer layers of bark (which are long since 
dead, and serve only as protective tissue) have 
reached the Hmit of their expanding capacity 
and have begun to split. The pupil will now 
be interested in the bark on the body of an old 
elm tree (Fig. 62); and he should be able to 
suggest one reason why stems remain cylindri- 
cal, and why the old bark becomes marked 
with furrows, scales, and plates. 

Most woody plants increase in diameter by the 
addition of an annual layer or *'ring'' on the 
Branch. outside of the woody cylinder, 
underneath the bark. The monocotyledo- 
nous plants comprise very few trees and 
shrubs in temperate climates (the palms, 
yuccas, and other tree-like plants are of 
this class), and they do not increase 
greatly in diameter and they rarely branch 
to any extent. 

Bark-bound Trees. — If, for any rea- 
son, the bark should become so dense 
and strong that the trunk cannot ex- 
pand, the tree is said to be ' 'bark-bound." 
Such condition is not rare in orchard trees tliat have been 
neglected. When good tillage is given tc such trees, they 




Fig. 62. — Piece of 
Bark from an 
Old Elm Trunk. 



THE STEMS— KINDS AND FORMS; TRUNIN G 



55 



may not be able to overcome the rigidity of the old bark, 
and, therefore, do not respond to the treatment. Sometimes 
the parts with thinner bark may outgrow in diameter the 
trunk or the old branches below them. The remedy is 
to release the tension. This may be done either by soften- 
ing the bark (by washes of soap or lye), or by separating 
it. The latter is done by slitting the bark-bound part 
(in spring), thrusting the point of a knife through the 
bark to the wood, and then drawing the blade down the 
entire length of the bark- 
bound part. The slit is 
scarcely discernible at first, 
but it opens with the growth 
of the tree, filHng up with 
new tissue beneath. Let the 
pupil consider the ridges 
which he now and then finds 
on trees, and determine 
whether they have any sig- 
nificance — whether the tree 
has ever been released, or in- 
jured by natural agencies. 

The Tissue covers the 
Wounds and "heals" them. 
— This is seen in Fig. 63, in which a ring of tissue rolls out 
over the wound. This ring of healing tissue forms most 
rapidly and uniformly when the wound is smooth and regu- 
lar. Observe the healing on broken and splintered limbs; 
also the difference in rapidity of healing between wounds 
on strong and weak limbs. There is a diflPerence in the 
rapidity of the healing process in different kinds of trees. 
Compare the apple tree and the peach. This tissue may in 




Fig. 63. — Proper Cuthng of a 
Branch. The wound will soon be 
"healed." 



56 



BE GINNKRS ' BOTANY 




Fig. 64. — Erroneous 
Pruning. 



turn become bark-bound, and the healing may stop. On 
large wounds it progresses more rapidly the first few years 

than it does later. This roll or 
ring of tissue is called a callus. 

The callus grows from the liv- 
ing tissue of the stem just about 
the wound. It cannot cover long 
dead stubs or very rough broken 
branches (Fig. 64). Therefore, 
in pruning the brandies should be 
cut close to the trunk and made 
even and smooth ; all long stubs 
must be avoided. The seat of 
the wound should be close to the 
living part of the trunk, for the 
stub of the limb that is severed 
has no further power in itself 
of making heaUng tissue. The 
end of the remaining stub is 
merely covered over by the 
callus, and usually remains a 
dead piece of wood sealed in- 
side the trunk (Fig. 65). If 
wounds do not heal over speed- 
ily, germs and fungi obtain 
foothold in the dying wood 
and rot sets in. Hollow trees 
are those in which the decay- 
fungi have progressed into the 
inner wood of the trunk ; they 
have been infected {¥\g. 66). 

Large wounds should be protected with a covering of 
paint, melted wax, or other adhesive and lasting material, 




Fig. 65. — Knot in a Hemlock 
Log. 



THE STEMS— KINDS AND FORMS; PRUNING 



57 




Fig. 66.— a Knot Hole, 
and the beginning of a 
hollow trunk. 



to keep out the germs and fungi. 
A covering of sheet iron or tin may- 
keep out the rain, but it will not ex- 
clude the germs of decay ; in fact, 
it may provide tlie very moist con- 
ditions that such germs need for 
their growth. Deep holes in trees 
should be. treated by having all the 
decayed parts removed down to the 
clean wood, the surfaces painted or 
otherwise sterilized, and the hole 
filled with wax or cement. 
Stems and roots are living, and 

they should not be wounded or 

mutilated unnecessarily. Horses 

should never be hitched to trees. 

Supervision should be exercised 

over persons who run telephone, 

telegraph, and electric light wires, 

to see that they do not mutilate 

trees. Electric light wires and trol- 
ley wires, when carelessly strung 

or improperly insulated, may kill 

trees (Fig. 6'j). 

Suggestions. — Forms of stems. 

43. Are the trunks of trees ever per- 
fectly cylindrical? If not, what may 
cause the irregularities ? Do trunks often 
grow more on one side than the other? 

44. SHt a rapidly growing limb, in spring, 



with a knife blade, and watch the result 
during the season. 45. Examine the 
w«odpile, and observe the variations in 
thickness of the annual rings, and especi- 
ally of the same ring at different places 
in the circumference. Cross-sections of 



\ \ 


XA/^ 


^V*Pt/v /^ 


\k Jr 


r^^^ f 


V L- 




\ n /" 




-i/ 




^^ 




vll^^^^^ 


^ir- — 


13 




l^fl 




,^hh 




lifll^^p 


^^SHWB 


w^^^^^. 


" '.^0^\L-'^ 


^^&*" 



Fig. 67. — Elm Tree killed 
BY A Direct Current 
FROM AN Electric 
Railroad System. 



58 



BEG/NNEKS' BOTANY 



horizontal branches are interesting in this connection. 46. Note 
the enlargement at the base of a branch, and determine whether 
this enlargement or bulge is larger on long, horizontal limbs than 
on upright ones. Why does this bulge develop? Does it serve 
as a brace to the limb, and is it developed as the result of constant 
strain? 47. Strength of stems. The pupil should observe the 
fact that a stem has wonderful strength. Compare the propor- 
tionate height, diameter, and weight of a grass stem with those of 
the slenderest tower or steeple. Which has the greater strength? 
Which the greater height? Which will withstand the most wind? 
Note that the grass stem will regain its position even if its top is 
bent to the ground. Note how plants are weighted down after a 
heavy rain and how they recover themselves. 48. Split a corn- 
stalk and observe how the joints are tied together and braced with 
fibres. Are there similar fibres in steins of pigweed, cotton, sun- 
flower, hollyhock? 




Fig. 68. — Potato. What are roots, and what stems ? Has tlie plant more than 
one kind of stem ? more than two kinds ? Explain. 



CHAPTER X 



THE STEM — ITS GENERAL STRUCTURE 



There are two main types of stem structure in flowering 
plants, the differences being based on the arrangement ot 
bundles or strands of tissue. These types are endogenous 
and exogenous (page 20). It will require patient laboratory 
work to understand what these types and structures are. 

Endogenous, or Monocotyledonous Stems. — Examples of 
endogenous stems are all the grasses, cane-brake, sugar- 
cane, smilax or green-brier, 
palms, banana, canna, bam- 
boo, lilies, yucca, aspara- 
gus, all the cereal grains. 
For our study, a cornstalk 
may be used as a type. 

A piece of cornstalk^ 
either green or dead, should 
be in the hand of each 
pupil while studying this 
lesson. Fig. 69 will also 
be of use. Is there a swelling at the nodes.!* Which 
part of the internode comes nearest to being perfectly 
round } There is a grooved channel running along one 
side of the internode : how is it placed with reference to 
the leaf ? with reference to the groove in the internode 
below it ? What do you find in each groove at its lower 
end? (In a dried stalk only traces of this are usually 
seen.) Does any bud on a cornstalk besides the one at 

59 




Fig. 69. — Cross-section of Corn- 
stalk, showing the scattered fibro- 
vascular bundles. Slightly enlarged. 



6o 



BEGINNERS' BOTANY 



the top ever develop ? Where do suckers come from ? 
Where does the ear grow ? 

Cut a cross-section of the stalk between the nodes (Fig. 
69). Does it have a distinct bark ? The interior consists 
of soft **pith" and tough woody parts. The wood is found 
in strands or fibres. Which is more abundant? Do the 
fibres have any definite arrangement ? Which strands are 
largest.? Smallest."* The firm smooth rind {which cannot 
properly be called a bark) consists of small wood strands 
packed closely together. Grass stems are hollow cylinders ; 
and the cornstalk, because of the lightness of its contents, 
is also practically a cylinder. Stems of this kind are ad- 
mirably adapted for providing a strong support to leaves 
and fruit. This is in accordance with the well-known law 
that a hollow cylinder is much stronger than a solid 
cylinder of the same weight of material. 
Cut a thin slice of the inner soft part and 
hold it up to the light. Can you make out 
a number of tiny compartments or cells.? 
These cells consist of a tissue called paren- 
chyma^ the tissue from which when young all 
the other tissues arise and differentiate. The 
numerous walls of these cells may serve to 
brace the outer wall of the cylinder ; but their 
chief function in the young stalk is to give 
origin to other cells. When alive they are 
filled with cell sap and protoplasm. 

Trace the woody strands through the nodes. 
Do they ascend vertically } Do they curve 
toward the rind at certain places ? Compare 
their course with the strands shown in Fig. 70. The woody 
strands consist chiefly of tough fibrous cells that give rigidity 




Fig. 70. — Dia- 
gram TO SHOW 
THE Course of 

FiBRO- VASCU- 
LAR Bundles 
IN Monocoty- 
ledons. 



THE STEM— ITS GENERAL STRUCTURE 



6l 




Fig. 71.— Diagram of 
Wood Strands or 

FiBRO-VASCULAR 

Bundles in a 
Root, showing the 
wood (jr) and bast 
(/) separated. 



and strength to the plant, and of long tubular interrupted 

canals that serve to convey sap upward from the root and to 

convey food downward from the leaves to the stem and the 

roots. 

Monocotyledons, as shown by fossils, existed before 

dicotyledons appeared, and it is thought that the latter 

were developed from ancestors of the 

former. It will be interesting to trace 

the relationship in stem structure. It 

will first be necessary to learn something 

of the structure of the wood strand. 
Wood Strand in Monocotyledons and 

Dicotyledons. — Each wood strand (or 

fibro-vascular bundle) consists of two 

parts — the bast and the wood proper. 

The wood is on the side of the strand 

toward the centre of the stem and con- 
tains large tubular canals that take the watery sap upward 

from the roots. The bast is on the side toward the bark, 

and contains fine tubes 
through which diffuses 
the dense sap contain- 
ing digested food from 
the leaves. In the root 
(Fig. 71) the bast and 
the wood are separate, 
so that there are two 
kinds of strands. 

In monocotyledons, 
as already said, the 
strands (or bundles) are 
usually scattered in the 

stem with no definite arrangement (Figs. 72, 73). In 

dicotyledons the strands, or bundles, are arranged in a 




Fig. 72. — Part of Cross-section of Root- 
stock OF Asparagus, showing a few fibro- 
vascular bundles. An endogenous stem. 



62 



BRCrNNERS* BOTANY 






Scattered 
Bundles or 
Strands, in 
monocotyledons 
at a, and the bun- 
dles in a circle in 
dicotyledons at b. 



Fio. 74. —Dicotyledonous Stem of One Year at Left 

WITH Five Bundles, and a two-year stem at right. 
<7, the pith; c, the wood part ; ^, the bast part; a, one year's growth. 

ring. As the dicotyledonous seed germi- 
Fio. 73. — The nates, five bundles are usually formed in 

its hypocotyl (Fig. 74); soon five more are 

interposed 

between 

them, and 

the multi- 
plication continues, in 
tough plants, until the 
bundles touch (Fig. 74, 
right). The inner parts 
thus form a ring of wood 
and the outer parts form 
the inner bark or bast. A 
new ring of wood or bast 
is formed on stems of di- 
cotyledons each year, and 

the age of a cut stem is 

„ ., J . . J Fig. 75. — Fibro-vascular Bundle of 

easily determmed. i.,^,^^, corn, much magnified. 

When cross-sections of ^, annular vessel ; ^', annular or spiral vessel ; 
♦^^^^^^4. 1 J IT ^^» thick-walled vessels; W, tracheids or 

mOnOCOtyledonOUS and dl- ^^ody tissue ; F, sheath of fibrous tissue sur- 

rounding the bundle ; FT, fundamental tissue 
or pith ; S, sieve tissue ; P, sieve plate ; C, 
companion cell ; /, intercellular space, formed 
by tearing down of adjacent cells ; VV , wood 
parenchyma. 




cotyledonous bundles are 
examined under the mi- 
croscope, it is readily seen 



THE STEM— ITS GENERAL STRUCTURE 



63 



why dicotyledonous bundles form rings of wood and mono- 
cotyledonous cannot (Figs. 75 and 'j^). The dicotyledon- 
ous bundle (Fig. ^6) has, running across it, a layer of brick- 
shaped cells called cambium, which cells are a specialized 
form of the parenchyma cells and retain the power of 




Fig. 76. — The Dicotyledonous Bundle or Wood Strand. Upper figure 
is of moonseed : 

r, cambium ; </, ducts ; i, end of first year's growth ; 2, end of second year's growth ; bast 
part at left and wood part at right. Lower figure (from Wettstein) is sunflower: h, wood- 
cells; ^.vessels; <:, cambium; /.fundamental tissue or parenchyma; ^, bast; ^/, bast 
parenchyma; s, sieve-tubes. 

growing and multiplying. The bundles containing cam- 
bium are called open bundles. There is no cambium in 
monocotyledonous bundles (Fig. 75) and the bundles are 
called closed bundles. Monocotyledonous stems soon cease 
to grow in diameter. The stem of a palm tree is almost 



64 BEGINNERS' BOTANY 

as large at the top as at the base. As dicotyledonous 
plants grow, the sterns become thicker each year, for the 
delicate active cambium layer forms new cells from early 
spring until midsummer or autumn, adding to the wood 
within and to the bark without. As the growth in spring 
is very rapid, the first wood-cells formed are much larger 
than the last wood-cells formed by the slow growth of the 




Fig. 77. —-White Pine Stem, s years old. The outermost layer is bark. 

late season, and the spring wood is less dense and of a 
lighter colour than the summer wood; hence the time 
between two years' growth is readily made out (Figs. 77 
and 78). Because of the rapid growth of the cambium in 
spring and its consequent soft walls and fluid contents, the 
bark of trees ''peels" readily at that season. 

Medullary Rays. — The first year's growth in dicotyle- 
dons forms a woody ring which almost incloses the pith, 
and this is left as a small cylinder which does not grow 



THE STEM— ITS GENERAL STRUCTURE 



65 



larger, even if the tree should Hve a century. It is not 
quite inclosed, however, for the narrow layers of soft cells 
separating the bundles remain be- 
tween them (Fig. 78), forming ra- 
diating lines called medullary rays 
or pith rays. 

The Several Plant Cells and their 
Functions* — In the wood there are 
some parenchyma cells that have 
thin walls still, but have lost 
the power of di- 
vision. They are 
now storage cells. 
Therie are also 

wood fibres which /, pith; /, parenchyma 

are thick-walled 







AIX 


^ 






s 




^ 


^ 




V^ 


^ 




S 


H 







SO 




Fig. 78. — Arrangement of 
Tissues in Two - yea r- 
OLD Stem of Moonseed. 



The fibro- 
vascular bundles, or wood 
strands, are very prominent, with 
Fig. 79. — Markings and rigid (h, Fig. thin medullary rays between. 

IN Cell Walls rr/^N i . . xi i 

OF Wood Fibre '^h ^nd servc to support the sap-canals 



j/, spiral ; an, annular 
sc, scalariform. 



or wood vessels (or tracheids) that are 
formed by the absorption of the end 

walls of upright rows of cells ; the canals 

pass from the roots to the twigs and even 

to ribs of the leaves and serve to transport 

the root water. They are recognized (Fig. 

79) by the pecuHar thickening of the wall 

on the inner surface of the tubes, occur- 
ring in the form of spirals. Sometimes the 

whole wall is thickened except in spots 

called pits (,^, Fig. 76). These thin spots 

(Fig. 80) allow the sap to pass to other p^^ g^ 

cells or to neighbouring vessels. 
The cambium, as we have seen, consists '^t^ttThtlt 

of cells whose function is growth. These pit borders at o, *, 




Pits in 
THE Cell Wall. 



66 



BEGINNERS* BOTANY 




cells are thin-walled and filled with protoplasm. During 

the growing season they are continually adding to the 

wood within and the bark with- 
out ; hence the layer moves out- 
ward as it deposits the new 
woody layer within. 

The bark consists of inner or 
fibrous bark or new bast (these 
fibres in flax become linen), the 
green or middle bark which func- 
tions somewhat as the leaves, 
and the corky or outer bark. 
The common word " bark " is 
seen, therefore, not to represent 
a homogeneous or simple struc- 
ture, but rather a collection of 
several kinds of tissue, all sepa- 
rating from the wood beneath 
by means of cambium. The new 
bast contains (i) the sieve-tubes 
(Fig. 8i) which transport the 

sap containing organic substances, as sugar 

and proteids, from the leaves to the parts 

needing it {s, Fig. j6\ These tubes have 

been formed like the wood vessels, but 

they have sieve-plates to allow the dense 

organic-laden sap to pass with sufficient 

readiness for purposes of rapid distribu- 
tion. (2) There are also thick-walled bast 

fibres (Fig. 82) in the bast that serve 

for support. (3) Tlioro is also some 

parenchyma in the new l;ast; it is Fig. 82.— thick- 

, , , . ei WALLED BaST 

now m part a storage tissue. borne- cells. 



Fig. 81. — Sieve-tubes, j, j; 

/ shows a top view of a sieve-plate, 
with a companion cell, c, at the 
side; o shows sieve-plates in the 
side of the cell. In s, s the proto- 
plasm is shrunken from the walls 
by reagents. 






THE STEM— ITS GENERAL STRUCTURE 6/ 

times the walls of parenchyma cells in the cortex thicken 
at the corners and form brace cells (Fig. 83) (collenchyma) 
for support ; sometimes the whole wall is thickened, form- 
ing grit cells or stone cells (Fig. 

84 ; examples in 

tough parts of 

pear, or in stone 

of fruits). Some 

parts serve for 
FIG. 83. - COLL EN- secretions (milk, 
CHYMA IN Wild rosin, etc.) and 

TEWELWEED or 11 1 r 

TOUCH-ME-NOT (IM- ^^^ Callcd lutCX 

PATIENS). tubes. ^'''- ^'*- -^^'"^ ^'^''^'• 

The outer bark of old shoots consists of corky cells that 
protect from mechanical injury, and that contain a fatty sub- 
stance (suberin) impermeable to water and of service to 
keep m moisture. There is sometimes a cork cambium (or 
phellogen) in the bark that serves to extend the bark and 
keep it from splitting, thus increasing its power to protect. 

Transport of the <*Sap." — We shall soon learn that the 
common word " sap " does not represent a single or simple 
substance. We may roughly distinguish two kinds of more 
or less fluid contents: (i) the root zvater, sometimes called 
mineral sap, that is taken in by the root, containing its 
freight of such inorganic substances as potassium, calcium, 
iron, and the rest ; this root water rises, we have found, ifi 
the ivood vessels, — that is, in the young or "sapwood " (p. 
96); (2) Xho, elaborated or oi'gani:;ed materials Y^^iSsmghdick 
and forth, especially from the leaves, to build up tissues 
in all parts of the plant, some of it going down to the roots 
and root-hairs ; this organic material is transported, as we 
have learned, in the sieve-tubes of the inner bast, — that is, 
in the ** inner bark." Removing the bark from a trunk in 



6S 



BEGINNERS' BOTANY 



a girdle will not stop the upward rise of the root water so 
long as the wood remains alive ; but it will stop the passage 
of the elaborated or food-stored materials to parts below 
and thus starve those parts ; and if the girdle does not 
heal over by the deposit of new bark, the tree will in time 
starve to death. It will now be seen that the common 
practice of placing wires or hoops about trees to hold 
them in position or to prevent branches from falling is 
irrational, because such wires interpose barriers over which 

the fluids cannot pass ; in 
time, as the trunk increases 
in diameter, the wire girdles 
the tree. It is much better 
to bolt the parts together by 
rods extending through the 
branches (Fig. 85). These 
bolts should fit very tight in 
their holes. Why? 

Wood. — The main stem 
or trunk, and sometimes 
the larger branches, are the 
sources of lumber and tim- 
ber. Different kinds of wood have value for their special 
qualities. The business of raising wood, for all purposes, 
is known as forestry. The forest is to be considered as a 
crop, and the crop must be harvested, as much as corn or 
rice is harvested. Man is often able to grow a more pro- 
ductive forest than nature does. 

Resistance to decay gives value to wood used for shingles 
{cypress^ heart of yellow pine) and for fence posts (mul- 
berry^ cedar^ post oak^ bois d'arCy mesqtiite). 

Hardness and strength are qualities of great value in 
building. Live oak is used in ships. Red oaky rock maple^ 




Fig. 85.— The Wrong Way to 
BRACE A Tree. (See Fig. iiS;. 



THE STEM— ITS GENERAL STRUCTURE 69 

and yellow pine are used for floors. The best flooring is 
sawn with the straight edges of the annual rings upward ; 
tangential sawn flooring may splinter. Chestnut is common 
in some parts of the country, being used for ceiling and 
inexpensive finishing and furniture. Locust and bois d'arc 
(osage orange) are used for hubs of wheels; bois d'arc 
makes a remarkably durable pavement for streets. Ebony 
is a tropical wood used for flutes, black piano keys, and 
fancy articles. Ash is straight and elastic ; it is used 
for handles for Hght implements. Hickory is very strong 
as well as elastic, and is superior to ash for handles, spokes, 
and other uses where strength is wanted. Hickory is 
never sawn into lumber, but is split or turned. The 
"second growth," which sprouts from stumps, is most 
useful, as it splits readily. Fast-growing hickory in rich 
land is most valuable. The supply of useful hickory is 
being rapidly exhausted. 

Softness is oftejz important. White pine and sweet gum 
because of their softness and lightness are useful in box- 
making. " Georgia " or southern pine is harder and stronger 
than white pine ; it is much used for floors, ceilings, and 
some kinds of cabinet work, y^laiie pine is used for window- 
sash, doors, and moulding, and cheaper grades are used for 
flooring. Hemlock is the prevailing lumber in the east for 
the framework and clapboarding of buildings. Redwood 
and Douglas spruce are common building materials on the 
Pacific coast. Cypress is soft and resists decay and is 
superior to white pine for sash, doors, and posts on the 
outside of houses. Cedar is readily carved and has a 
unique use in the making of chests for clothes, as its odour 
repels moths and other insects. Willow is useful for bas- 
kets and light furniture. Basswood or linden is used for 
light ceiling and sometimes for cheap floors. Whitewood 



70 



BEGINNERS' BOTANY 



(incorrectly called poplar) is employed for wagon bodies 
and often for house finishing. It often resembles curly 
maple. 

Beauty of grain and polish gives wood value for furni- 
ture,- pianos, and the like. Mahogany and white oak are 
most beautiful, although red oak is also used. Oak logs 
which are first quartered and then sawn radially expose the 
beautiful silver grain (medullary rays). Fig. Z6 shows one 

mode of quartering. 
The log is quartered 
on the lines a, a, byb \ 
then succeeding 
boards are cut from 
each" quarter at i, 
2, 3, etc. The nearer 
the heart the better 
the "grain" : why? 
Ordinary boards are 
sawn tangentially, 
as c^ c. Curly pine, 
curly walnut, and 
bird's-eye maple are 
woods that owe their 
beauty of grain to wavy lines or buried knots. A mere 
stump of curly walnut is worth several hundred dollars. 
Such wood is sliced very thin for veneering and glued 
over oilier woods in luakiiijj^ pianos and furniture. If 
the cause of wavy grain could be found out and such wood 
grown at will, the discovery would be very useful. Maple is 
much used for furniture. Birch may be coloured so as very 
closely to represent mahogany, and it is useful for desks. 

Special Products of Trees. — Cork from llic hark of tJic 
cork oak in Spain, latex from the rubber, and sap from the 




Fig. 86. — The Making of Ordinary Boards, 
AND One V^ay of Making " Quartered " 
Boards. 



THE STEM— ITS GENERAL STRUCTURE *J\ 

sugar-maple trees, turpentine from pine, tannin from oak 
bark, Peruvian bark from cinchona, are all useful products. 

Suggestions. — Parts of a root and stem through which liquids 
rise. 49. Pull up a small plant with abundant leaves, cut off the 
root so as to leave two inches or more on the plant (or cut a leafy 
shoot of squash or other strong-growing coarse plant), and stand it 
in a bottle with a little water at the bottom which has been coloured 
with red ink (eosine). After three hours examine the root; make 
cross sections at several places. Has the water coloured the axis 
cylinder? The cortex? What is your conclusion? Stand some 
cut flowers or a leafy plant with cut stem in the same solution and 
examine as before : conclusion ? 50. Girdle a twig of a rapidly 
growing bush (as willow) in early spring when growth begins {a) 
by very carefully removing only the bark, and {U) by cutting away 
also the sapwood. Under which condition do the leaves wilt? 
Why ? 51. Stand twigs of willow in water ; after roots have formed 
under the water, girdle the twig (in the two ways) above the roots. 
What happens to the roots, and why? 52. Observe the swellings 
on trees that have been girdled or very badly injured by wires or 
otherwise : where are these swellings, and why ? 53. Kinds of 
wood. Let each pupil determine the kind of wood in the desk, 
the floor, the door and window casings, the doors themselves, the 
sash, the shingles, the fence, and in the small implements and 
furniture in the room ; also what is the cheapest and the most 
expensive lumber in the community. 54. How many kinds of 
wood does the pupil know, and what are their chief uses? 

Note to Teacher. — The work in this chapter is intended to be 
mainly descriptive, for the purpose of giving the pupil a rational 
conception of the main vital processes associated with the stem, 
in such a way that he may translate it into his daily thought. It 
is not intended to give advice for the use of the compound micro- 
scope. If the pupil is led to make a careful study of the text, draw- 
ings, and photographs on the preceding and the following pages, 
he will obtain some of the benefit of studying microscope sections 
without being forced to spend time in mastering microscope 
technique. If the school is equipped with compound microscopes, 
a teacher is probably chosen who has the necessary skill to 
manipulate them and the knowledge of anatomy and physiology 
that goes naturally with such work ; and it would be useless to 
give instruction in such work in a text of this kind. The writer is 
of the opinion that the introduction of the compound microscope 
into first courses in botany has been productive of harm. Good 
and vital teaching demands first that the pupil have a normal, 



72 



BEGINNERS* BOTANY 



direct, and natural relation to his subject, as he commonly meets 
it, that the obvious and significant features of the plant world be 
explained to him and be made a means of training him. The 
beginning pupil cannot be expected to know the fundamental 
physiological processes, nor is it necessary that these processes 
should be known in order to have a point of view and trained 
intelligence on the things that one customarily sees. Many a 
pupil has had a so-called laboratory course in botany without 
having arrived at any real conception of what plants mean, or 
without having had his mind opened to any real sympathetic 
touch with his environment. Even if one's knowledge be not 
deep or extensive, it may still be accurate as far as it goes, and 
his outlook on the subject may be rational. 




Fig. 87. — The Many-stemmed Thickets of Mangrove of Southern- 
most Seacoasts, many of the trunks being formed of aerial roots. 



CHAPTER XI 

LEAVES — FORM AND POSITION 

Leaves may be studied from four points of view, — with 
reference to (1) their kinds and shapes; {2) their position, or 
arrangemefit on the plant; (3) their anatomy , or structure ; 




Fig. 88. — a Simple Netted-veined Leaf. 

(4) their functiouy or the work they 
perform. This chapter is concerned 
with the first ,4t two categories. 





Fig. 90. — Compound or Branched Leaf 
OF Brake (a common fern). 



Fig. 89. — a Simple Par- 
allel-veined Leaf. 

Kinds. — Leaves 
are simple or un- 
branchcd (Figs. ^Z, 
89), and compound or 
branched (Fig. 90), 



73 



H 



BEGINNERS* BOTANY 



The method of compounding or branching follows the 
mode of veining. The veining, or venation, is of two gen- 
eral kinds. In some plants the main veins 
diverge, and there is a conspicuous net- 
work of smaller veins ; such leaves are 
netted-veined. They are characteristic of 
the dicotyledons. In other plants the 
main veins are parallel, or nearly so, and 
there is no conspicuous network ; these 
are parallel-veined leaves (Figs. 89, 102). 
These leaves are the rule in monocoty- 
ledonous plants. The venation of netted- 
veined leaves is pinnate or feather-like 
when the veins arise from the side of a 
continuous midrib (Fig. 91); palmate or 
digitate (hand-like) when the veins arise 
from the apex of the petiole (Figs. Z^, 92). If leaves were 
divided between the main veins, the former would be 
pinnately arid the latter digitately compound. 

It is customary to speak of a leaf as compound only 
when the parts or branches are completely separate blades, 




Fig. 91. — Com- 
plete Leaves of 
Willow. 





Fig. 92. — Digitate-veined Pel- 
tate Leaf of Nasturtium. 



Fig. 93. — Pinnately Compound 
Leaf of Ash. 



as when the division extends to the midrib (Figs. 90, 93, 
94,95). The parts or branches are known as leaflets. 



LEAVES— FORM AND POSITION 



n 



Sometimes the leaflets themselves are compound, and the 
whole leaf is then said to be bi-compound or twice-com- 




FlG. 94, — DlGI- 

TATELY Compound 
Leaf of Rasp- 
berry. 



Fig. 95. — Poison Ivy. Leaf and Fruit. 

pound (Fig. 90). Some leaves are three-compound, four- 
compound, or five-compound. Decompound is a general 
term to express any degree of 
compounding beyond twice-com- 
pound. 

Leaves that are not divided as 
far as to the midrib are said to 
be: 

lobed, if the openings or sinuses 
are not more than half the depth 
of the blade (Fig. 96); 

cleft, if the sinuses are deeper pio. 96. - Lobed leaf of 
than the middle ; Sugar Maple. 




76 



BEGINNERS* BOTANY 




Fig. 97. — Digitately Parted Leaves 
OF Begonia. 



parted, if the sinuses 
reach two thirds or more 
to the midrib (Fig. 97); 

divided, if the sinuses 
reach nearly or quite to 
the midrib. 

The parts are called 
lobes, divisions, or seg- 
ments, rather than leaf- 
lets. The leaf may be 
pinnately or digitately 
A pinnately parted or 



lobed, parted, cleft, or divided. 

cleft leaf is sometimes said to be pinnatifid. 

Leaves may have 
one or all of three 
parts — blade, or 
expanded part ; pe- 
tiole, or stalk ; stip- 
ules, or 
appendages 
at the base of the 
petiole. A leaf that 
has all three of these 
parts is said to be 
complete (Figs. 91, 
106). The stipules 
are often green and 
leaflike and per- 
form the function fig. 98 
of foliage as in the 
pea and the Japanese quince (the latter common in yards). 

Leaves and leaflets that have no stalks are said to be 
sessile (Figs. 98, 103), i,e. sitting. Find several examples. 




Oblong 



ovate Sessile Leaves of 
Tea. 



LEAVES'- FORM AND POSITION 



77 




Fig. 99.— Clasp- 
ing Leaf of a 
"Wild Aster. 



The same is said of flowers and fruits. 
The blade of a sessile leaf may partly or 
wholly surround the stem, when it is said 
to be clasping. Examples : aster (Fig. 99), 
corn. In some cases the leaf runs down 
the stem, forming a wing ; such leaves are 
said to be decurrent (Fig. 100). When 
opposite sessile leaves are joined by their 
bases, they are said to be connate (Fig. loi). 
Leaflets may have one or all of these 

three parts, but the stalks of 
leaflets are called petiolules 
and the stipules of leaflets are 
called stipels. The leaf of the 
garden bean has leaflets, peti- 
olules, and stipels. 

The blade is usually attached 
to the petiole by its lower edge. 
In pinnate-veined leaves, the petiole seems to 
continue through the leaf as a midrib (Fig. 91). 
In some plants, however, the petiole joins 
the blade inside or beyond the margin (Fig. 92). Such 
leaves are said to be pel- 
tate or shield-shaped. This 
mode of attachment is par- 
ticularly common in float- 
ing leaves {e.g. the water 
lilies). Peltate leaves are 
usuafly digitate-veined. 

How to Tell a Leaf.— It 
is often difficult to distin- 

guishcompound leaves from ^^^ ,01. -Two Pairs of Connate 
leafy branches, and leaflets Leaves of Honeysuckle. 




Fig. 100. — De- 
current 
Leaves of 
Mullein. 




78 



BEGINNERS' BOTANY 



from leaves. As a rule leaves can be distinguished by 
the following tests : ( i ) Leaves are temporary strjictures^ 
sooner or later falling. (2) Usually buds are borne in their 
axils, (3) Leaves are usually borne at joints or 
nodes. (4) They arise on wood of the curre7it 
year's growth. (5) They have a more or less 
defiiiite arrangement. When leaves fall, the twig 
that bore them remains; when leaflets fall, the 
main petiole or stalk that bore them also falls. 

Shapes. — Leaves and leaflets are infinitely 
variable in shape. Names have been given to 
some of the more definite or regular shapes. 
These names are a part of the language of bot- 
any. The names represent ideal or 
typical shapes ; there are no two 
leaves alike and very 
few that perfectly con- 
form to the definitions. 
The shapes are likened 
to those of famihar ob- 
jects or of geometrical 
figures. Some of the 
commoner shapes are as 
follows (name original 
examples in each class): 
Linear, several times longer than broad, with the sides 

\ nearly or quite parallel. Spruces and most grasses 
are examples (Fig. 102). In linear leaves, the main 
veins are usually parallel to the midrib. 
Oblong, twice or thrice as long as broad, with the sides 

\ parallel for most of their length. Fig. 103 shows the 
short-oblong leaves of the box, a plant that is used 
for permanent edgings in gardens. 



Fig. 102.— 
Linear- 
acuminate 
Leaf of 
Grass. 




Fig. 103. — Short-oblong 
Leaves of Box. 



LEAVES— FORM AND POSITION 



79 



Elliptic differs from the oblong in having the sides gradu- 
ally tapering to either end from the middle. The 

^k European beech (Fig. 104) has elliptic 

^^ leaves. (This tree is often planted in 
this country.) 

Lanceolate, four to six times longer than 
broad, widest below the middle, and 

V tapering to either end. Some of the 
narrow-leaved willows are examples. 
Most of the willows and the peach 
have oblong-lanceolate leaves. 
Spatulate, a narrow leaf that is broadest 

\ toward the apex. The top is usually 
rounded. 




104. — 



Elliptic Leaf 

OF Purple 

Beech. 




Fig. 105. — Ovate 
Serrate Leaf of 
Hibiscus. 



Fig. 106. — Leaf of Apple, showing blade, 
petiole, and small narrow stipules. 

Ovate, shaped somewhat like the longitudinal section of an 
^ Q^gg\ about twice as long as broad, tapering from near 
^ the base to the apex. This is one of the commonest 
^ leaf forms (Figs. 105, 106). 



8o 



BEGINNERS' BOTANY 



Obovate, ovate inverted, — the wide part towards the apex. 

Leaves of mullein and leaflets of horse-chestnut and 
S false indigo are obovate. This form is commonest 

in leaflets of digitate leaves : why ? 
Reniform, kidney-shaped. This form is sometimes seen in 
^^ wild plants, particularly in root-leaves. Leaves of 
^^ wild ginger are nearly reniform. 
Orbicular, circular in general outline. Very few leaves are 

# perfectly circular, but there are many that are 
nearer circular than of any other shape. (Fig. 107). 





Fig. 107. — Orbicular 
LoBED Leaves. 



Fig. 108.— Truncate 
Leaf of Tulip Tree. 



The shape of many leaves is described in combinations 
of these terms : as ovate-lanceolate, lanceolate-oblong. 

The shape of the base and the apex of the leaf or leaflet 
is often characteristic. The base may be rounded (Fig. 
104), tapering (Fig. 93), cordate or heart-shaped (Fig. 105), 
truncate or squared as if cut off. The apex may be blunt 
or obtuse, acute or sharp, acuminate or long-pointed, trun- 
cate (Fig. 108). Name examples. 

The shape of the margin is also characteristic of each 
kind of leaf. The margin is entire when it is not in- 
dented or cut in any way (Figs. 99, 103). When not 



LEAVES — FORM AND POSITION 



8i 



entire, it may be undulate or wavy (Fig. 92), serrate or 
saw-toothed (Fig. 105), dentate or more coarsely notched 
(Fig. 95), crenate or round-toothed, lobed, and the like. 
Give examples. 

Leaves on the same plant often differ greatly in form. 
Observe the different shapes of leaves on the young 
growths of mulberries (Fig. 2) and wild grapes ; also 
on vigorous squash and pumpkin vines. In some cases 
there may be simple and 
compound leaves on the 
same plant. This is 
marked in the so-called 
Boston ivy or ampelop- 
5is (Fig. 109), a vine 
ihat is used to cover 
brick and stone build- 
ings. Different degrees 
of compounding, even 
in the same leaf, may 
often be found in honey 
locust. Remarkable dif- 
ferences in forms are 
seen by comparing seed-leaves with mature leaves of any 
plant (Fig. 30). 

The Leaf and its Environment. — The form and shape 
of the leaf often have direct relation to the place in which 
the leaf grozvs. Floati7tg leaves are usually expanded and 
flaty and the petiole varies in length with the depth of 
the water. Submerged leaves are usually linear or thread- 
likCf or are cut into very narrow divisions: thereby 
more surface is exposed, and possibly the leaves are less 
injured by moving water. Compare the sizes of the leaves 
on the ends of branches with those at the base of the 




Fig. 109. — Different Forms of Leaves 
FROM one Plant of Ampelopsis. 



82 BEGINNERS* BOTANY 

branches or in the interior of the tree top. In dense 
foliage masses, the petioles of the lowermost or under- 
most leaves tend to elongate — to push the leaf to the light. 

On the approach of winter the leaf usually ceases to 
work, and dies. It may drop, when it is said to be decidu- 
ous; or it may remain on the plant, when it is said to be 
persistent. If persistent leaves remain green during the 
winter, the plant is said to be evergreen. Give examples 
in each class. Most leaves fall by breaking off at the 
lower end of the petiole with a distinct joint or articula- 
tion. There are many leaves, however, that wither and 
hang on the plant until torn off by the wind; of such 
are the leaves of grasses, sedges, lilies, orchids, and other 
plants of the monocotyledons. Most leaves of this char- 
acter are parallel-veined. 

Leaves also die and fall from lack of light. Observe the 
yellow and weak leaves in a dense tree top or in any 
thicket. Why do the lower leaves die on house plants } 
Note the carpet of needles under the pines. All ever- 
greens shed their leaves after a time. Counting back from 
the tip of a pine or spruce shoot, determine how many 
years the leaves persist. In some spruces a few leaves 
may be found on branches ten or more years old. 

Arrangement of Leaves. — Most leaves have a regular 
position or arrangement on the stem. TJiis position or 
directio7t is determined largely by exposure to sunlight. In 
temperate chmates they usually hang in such a way that 
they receive the greatest amount of light. One leaf shades 
another to the least possible degree. If the plant were 
placed in a new position with reference to light, the leaves 
would make an effort to turn their blades. 

When leaves are opposite the pairs usually alternate. 
That is, if one pair stands north and south, the next pair 



LEAVES— FORM AND POSITION 



83 



stands east and west. See the box-elder shoot, on the 
left in Fig. 1 10. O^te pair does not shade the pair beneath. 
The leaves are in four vertical ranks. 

There are several kinds of alternate arrangement. In the 
elm shoot, in Fig. no, the third bud is vertically above the 
first. This is true no 
matter which bud is taken 
as the starting point. 
Draw a thread around 
the stem until the two 
buds are joined. Set a 
pin at each bud. Ob- 
serve that two buds are 
passed (not counting the 
last) and that the thread 
makes one circuit of the 
stem. Representing the 
number of buds by a de- 
nominator, and the num- 
ber of circuits by a 
numerator, we have the 
fraction \y which expresses 
the part of the circle that lies between any two buds. 
That is, the buds are one half of 360 degrees apart, or 
180 degrees. Looking endwise at the stem, the leaves 
are seen to be 2-ranked. Note that in the apple shoot 
(Fig. 1 10, right) the thread makes two circuits and five 
buds are passed : two fifths represents the divergence 
between the buds. The leaves are 5-ranked. 

Every plant has its own arrangement of leaves. For 
opposite leaves, see maple, box elder, ash, lilac, honey- 
suckle, mint, fuchsia. For 2-ranked arrangement, see 
all grasses, Indian corn, basswood, elm. For 3-ranked 




Fig, iio. — Phyij.otaxy of Box Elder, 
EiM. Apple. 



84 



BEGINNERS* BOTANY 



arrangement, see all sedges. For 5-ranked (which is one 
of the commonest), see apple, cherry, pear, peach, plum, 
poplar, willow. For 8-ranked, see holly, osage orange, 
some willows. More complicated arrangements occur in 
bulbs, house leeks, and other condensed plants. The buds 
or "eyes" on a potato tuber, which is an underground stem 
(why .?), show a spiral arrangement (Fig. 1 1 1). 
The arrange^nent of leaves on the stem is 
known as phyllotaxy (literally, '* leaf arrange- 
ment "). Make out the phyllotaxy on six 
different plants nearest the schoolhouse door. 
In some plants, several leaves occur at one 
level, being arranged in a circle around the 
stem. Such leaves are said to be verticillate, 
or whorled. Leaves arranged in this way are 
usually narrow : why } 

Although a definite arrangement of leaves 

is the rule in most plants, it is subject to 

modification. On shoots that receive the 

Fig. III. — light only from one side or that grow in dif- 

^Tthe^po^ ficult positions, the arrangement may not be 

TATo Tuber, definite, Examine shoots that grow on the 

w^ork It out under side of dense tree tops or in other par- 

on a fresh *^ * 

long tuber. tially lighted positions. 




Suggestions. — 55. The pupil should match leaves to determine 
whether any two are alike. Why ? Compare leaves from the 
same plant in size, shape, colour, form of margin, length of petiole, 
venation, texture (as to thickness or thinness), stage of maturity, 
smoothness or hairiness. 56. Let the pupil take an average 
leaf from each of the first ten different kinds of plants that 
he meets and compare them as to the above points (in Exer- 
cise 55), and also name the shapes. Determine how the various 
leaves resemble and differ. 57. Describe the stipules of rose, 
apple, fig, willow, violet, pea, or others. 58. In what part of 
the world are parallel- veined leaves the more common ? 59. Do 



LEAVES— FORM AND POSITION 8$ 

you know of parallel-veined leaves that have lobed or dentate mar- 
gins ? 60. What becomes of dead leaves ? 61. Why is there 
no grass or other undergrowth under pine and spruce trees ? 
62. Name several leaves that are useful for decorations. Why 
are they useful ? 63. What trees in your vicinity are most 
esteemed as shade trees ? What is the character of their foliage ? 

64. Why are the internodes so long in water- sprouts and suckers ? 

65. How do foliage characters in corn or sorghum differ when the 
plants are grown in rows or broadcast ? Why ? 66. Why may 
removal of half the plants increase the yield of cotton or sugar- 
beets or lettuce ? 67. How do leaves curl when they wither ? 
Do different leaves behave differently in this respect? 68. What 
kinds of leaves do you know to be eaten by insects ? By cattle ? 
By horses ? What kinds are used for human food ? 69. How 
would you describe the shape of leaf of peach? apple? elm? 
hackberry? maple? sweet-gum? corn? wheat? cotton? hickory? 
cowpea? strawberry? chrysanthemum? rose? carnation? 70. Are 
any of the foregoing leaves compound ? How do you describe the 
shape of a compound leaf ? 71. How many sizes of leaves do you 
find on the bush or tree nearest the schoolroom door ? 72. How 
many colours or shades? 73. How many lengths of petioles? 
74. Bring in all the shapes of leaves that you can find. 




CHAPTER XII 



LEAVES — STRUCTURE OR ANATOMY 

Besides the framework, or system of veins found in 
blades of all leaves, there is a soft cellular tissue called 
mesophyll, or leaf parenchyma, and an epidermis or skin 
that covers the entire outside part. 

Mesophyll. — The mesophyll is not all alike or homoge- 
neous. The upper layer is composed of elongated cells 
placed perpendicular to the surface of the leaf. These 
are called palisade cells. These cells are usually filled 

with green bod- 
ies called chlo- 
rophyll grains. 
The grain con- 
tains a great 
number of chlo- 
rophyll drops 
imbedded in 
the protoplasm. 
Below the pali- 
sade cells is the 




Fig. 113. — Section of a Leaf, showing the airspaces. 

Breathing- pore or stoma at a. The palisade cells which chiefly 
conuin the chlorophyll are at b. Epidermal cells at c. 



spongy parenchyma, composed of cells more or less spher- 
cal in shape, irregularly arranged, and provided with many 
intercellular air cavities (Fig. 113). In leaves of some 
plants exposed to strong light there may be more than one 
layer of palisade cells, as in the India-rubber plant and 
the oleander. Ivy when grown in bright light will develop 
two such layers of cells, but in shaded places it may be 

S6 



LEAVES— STRUCTURE OR ANATOMY 8/ 

found with only one. Such plants as iris and compass 
plant, which have both surfaces of the leaf equally exposed 
to sunlight, usually have a palisade layer beneath each 
epidermis. 

Epidermis. — The outer or epidermal cells of leaves do 
not bear chlorophyll, but are usually so transparent that 
the green mesophyll can be seen through them. They 
often become very thick-walled, and are in most plants 
devoid of all protoplasm except a thin layer lining the 
walls, the cavities being filled with cell sap. This sap is 
sometimes coloured, as in the under epidermis of begonia 
leaves. It is not common to find more than one layer of 
epidermal cells forming each surface of a leaf. The epi- 
dermis serves to retain moisture in the leaf and as a general 
protective covering. In desert plants the epidermis, as a 
rule, is very thick and has a dense cuticle, thereby pre- 
venting loss of water. 

There are various outgrowths of the epidermis. Hairs 
are the chief of these. They may be (i) simple, as on 
primula, geranium, naegelia; (2) once branched, as on wall- 
flower; (3) compound, as on verbascum or mullein; (4) 
disk-like, as on shepherdia; (5) stellate, or star-shaped, as 
in certain crucifers. In some cases the hairs are glandular, 
as in Chinese primrose of the greenhouses {^Primula 
Sinensis) and certain hairs of pumpkin flowers. The hairs 
often protect the breathing pores, or stomates, from dust 
and water. 

Stomates (sometimes called breathing -pores) are small 
openiftgs or pores in the epidermis of leaves and soft stems 
that allow the passage of air and other gases and vapourr, 
{stomate or stoma, singular ; stomates or stomata, plural). 
They are placed 7iear the large intercellular spaces of the 
mesophyll, usually in positions least affected by direct 




SS BEGINNERS' BOTANY 

sunlight. Fig. 114 shows the structure. There are two 
guard-cells at the mouth of each stomate, which may in 
most cases open or close the passage as the conditions 
of the atmosphere may require. The guard-cells contain 

Fig. 114. — Diagram OF Stomate Fig. 115. — Stomate of Ivy, 

OF Iris (Oslerhout). showing compound guard-cells. 

chlorophyll. In Fig. 1 1 5 is shown a case in which there 
are compound guard-cells, that of ivy. On the margins 
of certain leaves, as of fuchsia, impatiens, cabbage, are 
openings known as water-pores. 

Stomates are very numerous ^ as will be seen from the num- 
bers showing the pores to each square inch of leaf surface : 

Lower surface Upper surface 

Peony I3j790 None 

Holly 63,600 None 

Lilac 160,000 None 

Mistletoe 200 200 

Tradescantia 2,000 2,000 

Garden Flag (iris) iIjS72 ii>572 

The arrangement of stomates on the leaf differs with 

each kind of plant. Fig, 116 shows stomates and also the 

outlines of contiguous epidermal cells. 

The function or work of the stomates 

is to regulate the passage of gases into 

and out of the plant. The directly 

active organs or parts are guard-cells, 

^ , ^ on either side the opening. One 

Fig. 116. — Stomates ^ ^ 

OF GERANIUM LEAF, mcthod of Opening is as follows : The 




LEAVES— STKUCTURE OR ANATOMY 



89 



P 



% 



thicker walls of the guard-cells (Fig. 114) absorb water 
from adjacent cells, these thick walls buckle or bend and 
part from one another at their middles on either side the 
opening, causing the stomate to open, when the air gases 
may be taken in and the leaf gases may pass out. When 
moisture is reduced in the leaf tissue, the guard-cells part 
with some of their contents, the thick walls 
straighten, and the faces of the two opposite 
ones come together, thus closing the stomate 
and preventing any water vapour from pass- 
ing out. When a leaf is actively at work 
making new organic compounds, the stomates 
are usually open; when unfavourable condi- 
tions arise, they are usually closed. They 
also commonly close at night, when growth 
(or the utilizing of the new materials) is most 
likely to be active. It is sometimes safer to 
fumigate greenhouses and window gardens 
at night, for the noxious vapours are less 
likely to enter the leaf. Dust may clog or 
cover the stomates. Rains benefit plants 
by washing the leaves as well as by provid- 
ing moisture to the roots. 

Lenticels. — On the young woody twigs 
of many plants (marked in osiers, cherry, 
birch) there are small corky spots or eleva- 
tions known as lenticels ( Fig. 117). They mark the loca- 
tion of some loose cork cells that function as stomates, 
for greeji shoots, as well as leaves, take in and discharge 
gases; that is, soft green twigs function as leaves. Under 
some of these twig stomates, corky material may form 
and the opening is torn and enlarged: the lenticels are 
successors to the stomates. The stomates lie in the epi- 



FiG. 117. — Len- 
ticels on 
Young Shoot 
OF Red Osier 

(CORNUS). 



$6 BEClNNEJiS* BOTANY 

dermis, but as the twig ages the epidermis perishes and 
the bark becomes the external layer. Gases continue to 
pass in and out through the lenticels, until the branch be- 
comes heavily covered with thick, corky bark. With the 
growth of the twig, the lenticel scars enlarge lengthwise 
or crosswise or assume other shapes, often becoming char- 
acteristic markings. 

Fibro-vascular Bundles. — We have studied the fibro- 
vascular bundles of stems (Chap. X). These stem bun- 
dles continue into the leaves^ ramifying into the veins, 
carrying the soil water inwards and bringing, by diffusion, 
the elaborated food out through the sieve-cells. Cut 
across a petiole and notice the hard spots or areas in it ; 
strip these parts lengthwise of the petiole. What are they } 

Fall of the Leaf. — In most common deciduous plants, 
when the season's work for the leaf is ended, the nutritious 
matter may be withdrawn, and a layer of corky cells is com- 
pleted over the surface of the stem where the leaf is attached. 
The leaf soon falls. It often falls even before it is killed 
by frost. Deciduous leaves begin to show the surface line 
of articulation in the early growing season. This articula- 
tion may be observed at any time during the summer. The 
area of the twig once; covered by the petioles is called the 
leaf-scar after the leaf has fallen. In Chap. XV are shown 
a number of leaf-scars. In the plane tree (sycamore or 
buttonwood), the leaf-scar is in the form of a ring surround- 
ing the bud, for the bud is covered by the hollowed end of. 
the petiole ; the leaf of sumac is similar. Examine with a 
hand lens leaf-scars of several woody plants. Note the 
number of bundle-scars in each leaf-scar. Sections may 
be cut through a leaf-scar and examined with the micro- 
scope. Note the character of cells that cover the leaf- 
scar surface. 



LEAVES--- STRUCTURE OR ANATOMY 9I 

Suggestions. — To study epidermal hairs : 75. For this study, 
use the leaves of any hairy or woolly plant. A good hand lens will 
reveal the identity of many of the coarser hairs. A dissecting micro- 
scope will show them still better. For the study of the cell structure, 
a compound microscope is necessary. Cross-sections may be made 
so as to bring hairs on the edge of the sections; or in some 
cases the hairs may be peeled or scraped from the epidermis and 
placed in water on a slide. Make sketches of the different kinds of 
hairs. 76. It is good practice for the pupil to describe leaves in 
respect to their covering : Are they smooth on both surfaces ? Or 
hairy? Woolly? Thickly or thinly hairy? Hairs long or short? 
Standing straight out or lying close to the surface of the leaf? 
Simple or branched? Attached to the veins or to the plane surface? 
Colour? Most abundant on young leaves or old? 77- Place a 
hairy or woolly leaf under water. Does the hairy surface appear 
silvery ? Why ? Other questions : 78. Why is it good practice 
to wash the leaves of house plants? 79. Describe the leaf-scars 
on six kinds of plants : size, shape, colour, position with reference 
to the bud, bundle-scars. 80. Do you find leaf-scars on mono- 
cotyledonous plants — corn, cereal grains, lilies, canna, banana, 
palm, bamboo, green brier? 81. Note the table on page 88. 
Can you suggest a reason why there are equal numbers of stomates 
on both surfaces of leaves of tradescantia and flag, and none on 
upper surface of other leaves ? Suppose you pick a leaf of lilac 
(or some larger leaf), seal the petiole with wax and then rub 
the under surface with vaseline ; on another leaf apply the vaseline 
to the upper surface ; which leaf withers first, and why? Make a 
similar experiment with iris or blue flag. 82. Why do leaves and 
shoots of house plants turn towards the light? What happens 
when the plants are turned around ? 83. Note position of leaves 
of beans, clover, oxalis, alfalfa, locust, at night 



CHAPTER XIII 
LEAVES — FUNCTION OR WORK 

We have discussed (in Chap. VIII) the work or function 
of roots and also (in Chap. X) the function of stems. 
We are now ready to complete the view of the main vital 
activities of plants by considering the function of the 
green parts (leaves and young shoots). 

Sources of Food. — The ordinary green plant has but two 
sources from which to secure food, *— the air and the soil. 
When a plant is thoroughly dried in an oven, the water 
passes off ; this water came from the soil. The remaining 
part is called the dry substance or dry matter. If the dry 
matter is burned in an ordinary fire, only the ash remains; 
this ash came from the soil. The part that passed off as 
gas in the burning cojttained the elements that came from 
the air ; it also contained some of those that came from 
the soil — all those (as nitrogen, hydrogen, chlorine) that 
are transformed into gases by the heat of a common fire. 
The part that comes from the soil (the ash) is small in 
amount, being considerably less than lo per cent and 
sometimes less than i per cent. Water is the most 
abundant single constituent or substance of plants. In a 
corn plant of the roasting-ear stage, about 80 per cent of 
the substance is water. A fresh turnip is over 90 per 
cent water. Fresh wood of the apple tree contains about 
45 per cent of water. 

Carbon. — Carbon enters abundantly into the composition 
of all plants. Note what happens when a plant is burned 

92 



LEAVES— FUNCTION OR WORK 93 

without free access of air, or smothered, as in a charcoal 
pit. A mass of charcoal remains, almost as large as the 
body of the plant. Charcoal is almost pure carbon, the ash 
present being so small in proportion to the large amount 
of carbon that we look on the ash as an impurity. Nearly 
half of the dry substance of a tree is carbon. Carbon 
goes off as a gas when the plant is bii7'ned in air. It does 
not go off alone, but in combination with oxygen in the 
form of carbon dioxide gas, COo. 

The green plant secures its carbon from the air. In 
other words, much of the solid ynatter of the plant comes 
from one of the gases of the air. By volume, carbon dioxide 
forms only a small fraction of 1 per cent, of the air. 
It would be very disastrous to animal life, however, if this 
percentage were much increased, for it excludes the life- 
giving oxygen. Carbon dioxide is often called ''foul gas." 
It may accumulate in old wells, and an experienced person 
will not descend into such wells until they have been tested 
with a torch. If the air in the well will not support com- 
bustion, — that is, if the torch is extinguished, — it usually 
means that carbon dioxide has drained into the place. The 
air of a closed schoolroom often contains far too much of 
this gas, along with little solid particles of waste matters. 
Carbon dioxide is often known as carbonic acid gas. 

Appropriation of the Carbon. — The carbon dioxide of the 
air readily diffuses itself into the leaves and other green 
parts of the plant. The leaf is delicate in texture, and when 
very young the air can diffuse directly into the tissues. 
The stomates, however, are the special inlets adapted for 
the admission of gases into the leaves and other green 
parts. Through these stomates, or diffusion-pores, the out- 
side air enters into the air-spaces of the plant, and is finally 
absorbed by the little cells containing the Hving matter. 



94 



BEGINNERS ' . BOTA NY 



Chlorohyll ("leaf green") is the agent that secures 
the energy by means of which carbon dioxide is utilized. 
This material is contained in the leaf cells in the form of 
grains (p. 86) ; the grains themselves are protoplasm, only 
the colouring matter being chlorophyll. The chlorophyll 
bodies or grains are often most abundant near the upper 
surface of the leaf, where they can secure the greatest 
amount of light. Without this green colouring matter, 
there would be no reason for the large flat surfaces which 
the leaves possess, and no reason for the fact that the 
leaves are borne most abundantly at the ends of branches, 
where the light is most available. Plants with coloured 
leaves as coleus, have chlorophyll, but it is masked by 
other colouring matter. This other colouring matter is 
usually soluble in hot water: boil a coleus leaf and notice 
that it becomes green and the water becomes coloured. 

Plants groivn in darkness are yellow and slender, and 
do not reach maturity. Compare the potato sprouts that 
have grown from a tuber lying in a dark cellar with 
those that have grown normally in the bright light. 
The shoots have become slender, and are devoid of chloro- 
phyll; and when the food that is stored in the tuber is 
exhausted these shoots will have lived useless lives. A 
plant that has been grown in darkness from the seed will 
soon die, although for a time the little seedling will grow 
very tall and slender. Why ? Light favours the production 
of chlorophyll, and the chlorophyll is the agent in the mak- 
ing of the organic carbon compounds. Sometimes chloro- 
phyll is found in buds and seeds, but in most cases these 
places are not perfectly dark. Notice how potato tubers de- 
velop chlorophyll, or become green, when exposed to light. 

Photosynthesis. — Carbon dioxide diffuses into the leaf; 
during sunlight it is used, and oxygen is given off. How 



LEAVES-^FUNCTION OB WOBK 95 

the carbon dioxide which is thus absorbed may be used in 
making an organic food is a complex question, and need not 
be studied here; but it may be stated that carbon dioxide 
and water are the constituents. Complex compounds are 
built up out of simpler ones. 

Chlorophyll absorbs certain light rays, and the energy 
thus directly or indirectly obtained is used by the living 
matter in uniting the carbon dioxide absorbed from the air 
with some of the water brought up from the roots. The 
idtimate result usually is starch. The process is obscure, 
but sugar is generally one step; and our first definite 
knowledge of the product begins when starch is deposited 
in the leaves. The process of using the carbon dioxide of 
the air has been known as carbon assimilation, but the 
term now most used is photosynthesis (from two Greek 
words meaning light and placing together.) 

Starch and Sugar. — All starch is composed of carbon, 
hydrogen, and oxygen {CqH.iqOq)„. The sugars and the 
substance of cell walls are very similar to it in composition. 
All these substances are called carbohydrates. In making 
fruit sugar from the carbon and oxygen of carbon dioxide 
and from the hydrogen and oxygen of the water, there 
is a surplus of oxygen (6 parts COg + 6 parts H.O 
== CeH^g^e + 6 Oo). It is this oxygen that is given off 
into the air during sunlight. 

Digestion. — Starch is in the form of insoluble granules. 
When such food material is carried from one part of the 
plant to another for purposes of growth or storage, it is 
made soluble before it can be transported. "When this 
starchy material is transferred from place to place, it is 
usually changed into sugar by the action of a diastase. 
This is a process of digestion. It is much like the change 
of starchy foodstuffs to sugary foods effected by the saliva. 



96 



BEGINNERS' BOTANY 



Distribution of the Digested Food. — After being changed 
to the sohible form, tJiis luatcrial is ready to be used in 
growth, either in tlie leaf, in the stem, or in the roots. 
With other more complex products it is then distributed 
throughojit all the growing parts 
. of the plant ; and when passing 

' ; down to the root, it seems to pass 

more readily through the inner 
bark, in plants which have a defi- 
nite bark. This gradual down- 
ward diffusion through the inner 
bark of materials suitable for 
growth is the process referred to 
when the ** descent of sap " is men- 
tioned. Starch and other products 
are often stored in one grozving 
season to be nsed in the next sea- 
son. If a tree is constricted or 
strangled by a wire around its 
trunk (Fig. ii8), the digested food 
cannot readily pass down and it is stored above the girdle, 
causing an enlargement. 

Assimilation. — TJie food from the air and that from the 
soil unite in the living tissues. The *'sap" that passes 
upwards from the roots in the growing season is made up 
largely of the soil water and the salts which have been 
absorbed in the diluted solutions (p. ^'jy This upward- 
moving water is conducted largely through certain tubular 
canals of the young luood. These cells are never continu- 
ous tubes from root to leaf; but the water passes readily 
from one cell or canal to another in its upward course. 

The upward-moving water gradually passes to the grow- 
ing parts, and everywhere in the living tissues, it is, of 




Fig, I i8. — Trunk Girdled 
BY A Wire. See Fig. 85. 



LEAVES— FUNCTION OR WORK 97 

course, in the most intimate contact with the soluble carbo- 
hydrates and products of photosynthesis. In the build- 
ing up or reconstructive and other processes it is therefore 
available. We may properly conceive of certain of the 
simpler organic molecules as passing through a series of 
changes, gradually increasing in complexity. There will 
be formed substances containing nitrogen in addition to 
carbon, hydrogen, and oxygen. Others will contain also 
sulphur and phosphorus, and the various processes may 
be thought of as culminating in protoplasm. Protoplasm 
is the living matter in pla7its. It is in the cells, and is 
usually semifluid. Starch is not living matter. The" 
complex process of building up the protoplasm is called 
assimilation. 

Respiration. — Plants need oxygen for respiration^ as 
anifnals do. We have seen that plants need the carbon 
dioxide of the air. To most plants the nitrogen of the air 
is inert, and serves only to dilute the other elements ; but 
the oxygen is necessary for all life. We know that all 
animals need this oxygen in order to breathe or respire. 
In fact, they have become accustomed to it in just the 
proportions found in the air; and this is now best for 
them. When animals breathe the air once, they make it 
foul, because they use some of the oxygen and give off 
carbon dioxide. Likewise, all living parts of the plant must 
have a constant supply of oxygen. Roots also need it, for 
they respire. Air goes in and out of the soil by diffusion, 
and as the soil is heated and cooled, causing the air to 
expand and contract. 

The oxygen passes into the air-spaces and is absorbed 
by the moist cell membranes. In the living cells it makes 
possible the formation of simpler compounds by which 
energy is released. This energy enables the plant to 



98 BEGINNERS' BOTANY 

work and grow, and the final products of this action are 
carbon dioxide and water. As a result of the use of this 
oxygen by night and by day, plants give off carbon dioxide. 
Plants respire; hut since they are stationary, and more or 
less inactive, they do not need so much oxygen as animals do, 
and they do not give off so much carbon dioxide. A few 
plants in a sleeping room need not disturb one more than a 
family of mice. It should be noted, however, that germina- 
ting seeds respire vigorously, hence they consume much oxy- 
gen; and opening buds and flowers are likewise active. 

Transpiration. — Much more water is absorbed by the 
roots than is used in growth, attd this surplus water passes 
from the leaves into the atmosphere by an evaporation process 
known as transpiration. Transpiration takes place more 
abundantly from the under surfaces of leaves, and through 
the pores or stomates. A sunflower plant of the height 
of a man, during an active period of growth, gives off a 
quart of water per day. A large oak tree may transpire 
150 gallons per day during the summer. For every ounce 
of dry matter produced, it is estimated that 15 to 25 pounds 
of water usually passes through the plant. 

When the roots fail to supply to the plant sttfficient water 
to equalize that transpired by the leaves, the plant wilts. 
Transpiration from the leaves and delicate shoots is in- 
creased by all the conditions which increase evapora- 
tion, such as higher temperature, dry air, or wind. The 
stomata open and close, tending to regulate transpiration 
as the varying conditions of the atmosphere affect the 
moisture content of the plant. However, in periods of 
drought or of very hot weather, and especially during a 
hot wind, the closing of these stomates cannot sufficiently 
prevent evaporation. The roots may be very active and 
yet fail to absorb sufficient moisture to equalize that given 



LEAVES -- FUNCTION OR WORK 99 

off by the leaves. The plant shows the effect (how ?). 
On a hot dry day, note how the leaves of corn '* roll " tow- 
ards afternoon. Note how fresh and vigorous the same 
leaves appear early the following morning. Any injury to 
the roots, such as a bruise, or exposure to heat, drought, or 
cold may cause the plant to wilt. 

Water is forced up by root pressure or sap pressure. 
(Exercise 99.) Some of the dew on the grass in the morn- 
ing may be the water forced up by the roots ; some of it is 
the condensed vapour of the air. 

The wilting of a plant is due to the loss of water from 
the cells. The cell walls are soft, and collapse. A toy 
balloon will not stand alone until it is inflated with air 
or liquid. In the woody parts of the plant the cell walls 
may be stiff enough to support themselves, even though 
the cell is empty. Measure the contraction due to wilt- 
ing and drying by tracing a fresh leaf on page of note- 
book, and then tracing the same leaf after it has been 
dried between papers. The softer the leaf, the greater 
will be the contraction. 

Storage. — We have said that starch may be stored in 
tv/igs to be used the following year. The very early flowers 
on fruit trees, especially those that come before the leaves, 
and those that come from bulbs, as crocuses and tulips, 
are supported by the starch or other food that was organ- 
ized the year before. Some plants have very special stor- 
age reservoirs, as the potato, in this case being a thickened 
stem although growing underground. (Why a thickened 
stem.!* p. 84.) It is well to make the starch test on winter 
twigs and on all kinds of thickened parts, as tubers and bulbs. 

Carnivorous Plants. — Certain plants capture insects and 
other very small animals and utilize them to some extent 
as food. Such are the sundew, which has on the leaves 



lOO 



BE GINNEKS' B O TAN Y 




sticky hairs that close over :he insect; the Venus 's fly-trap 
of the Southern States, in which the halves of the leaves 

close over the prey like the jaws 
of a steel trap ; and the various 
kinds of pitcher plants that col- 
lect insects and other organic 
matter in deep, water-filled, flask- 
like leaf pouches (Fig. 1 19). 

The sundew and the Venus 's 
fly-trap are sensitive to contact. 
Other plants are sensitive to the 
touch without being insectivo- 
rous. The common cultivated 
sensitive plant is an example. 
This is readily grown from seeds 
(sold by seedsmen) in a warm 
place. Related wild plants in 
the south are sensitive. The 
utility of this sensitiveness is not understood. 

Parts that Simulate Leaves. — We have learned that 
leaves are endlessly modified to suit the conditions in which 
the plant is placed. The most marked modifications are in 
adaptation to light. On the other hand, other organs often 
perform the fmtctions of leaves. Green shoots function as 
leaves. These shoots may look like leaves, in which case 
they are called cladophylla. The foliage of common 
asparagus is made up of fine branches : the real morpho- 
logical leaves are the minute dry functionless scales at the 
bases of these branchlets. (What reason is there for calling 
them leaves!*) The broad ** leaves" of the florist's smilax 
are cladophylla. Where are the leaves on this plant } In 
most of the cacti, the entire plant body performs the func- 
tions of leaves until the parts become cork-bound. 



Fig. 119. —The Common 
Pitcher Plant {Sarracenia 

purpurea) showingr the tubular 
leaves and the odd, longp-stalked 
flowers. 



LEAVES— FUNCTION OR WORK 



lOI 



Leaves are sometimes modified to perform other functions 
than the vital processes: they may be tendrils, as the 
terminal leaflets of pea and sweet pea; or spines, as in 
barberry. Not all spines and thorns, however, represent 
modified leaves: some of them (as of hawthorns, osage 
orange, honey locust) are branches. 

Suggestions. — To test for chlorophyll. 84. Purchase about a 
gill of wood alcohol. Secure a leaf of geranium, clover, or other 
plant that has been exposed to sunlight for a few hours, and, after 
dipping it for a minute in boiling water, put it in a white cup with 
sufficient alcohol to cover. Place the cup in a shallow pan of 
hot water on the stove where it is not hot enough for the alcohol 
to take fire. After a time the chlorophyll is dissolved by the 
alcohol which has become an intense green. Save this leaf for 
the starch experiment (Exercise 85). Without chlorophyll, the 
plant cannot appropriate the carbon dioxide of the air. Starch 
and photosynthesis. 85- Starch is present in the green leaves 
which have been exposed to sunlight; but in the dark no starch 
can be formed from carbon dioxide. Apply iodine to the leaf from 
which the chlorophyll was dissolved in the previous experiment. 
Note that the leaf is coloured purplish-brown throughout. The leaf 
contains starch. 86- Se- 
cure a leaf from a plant 
which has been in the 
dark for about two days. 
Dissolve the chlorophyll as 
before, and attempt to stain 
this leaf with iodine. No 
purplish-brown colour is pro- 
duced. This shows that 
the starch manufactured in 
the leaf may be entirely 
removed during darkness. 
87. Secure a plant which 
has been kept in darkness 
for twenty-four hours or 
more. Split a small cork 
and pin the two halves on opposite sides of one of the leaves, as 
shown in Fig. 120. Place the plant in the sunlight again. After 
a morning of bright sunshine dissolve the chlorophyll in this leaf 
with alcohol; then stain the leaf with the iodine. Notice that the 
leaf is stained deeply except where the cork was; there sunlight and 
carbon dioxide were excluded, Fig. 121. There is no starch in the 




Fig. I20. — Exclud- 
ing Light and 
CO2 FROM Part 
OF A Leaf. 




Fig. 121.— The 
Result. 



I02 



BEGINNERS' BOTANY 



covered area. 88. Plants or parts of plants that have developed 
no chlorophyll can form no starch. Secure a variegated leaf of 
coleus, ribbon grass, geranium, or of any plant showing both white 
and green areas. On a day of bright sunshine, test one of these 
leaves by the alcohol and iodine method for the presence of starch. 
Observe that the parts devoid of green colour have formed no 
starch. However, after starch has once been formed in the leaves, 



it may be 
to be again 
the living 



changed into soluble substances and removed, 
converted into starch in certain other parts of 
tissues. To test the gnmig off of oxygen by day. 
89. Make the experiment illus- 
trated in Fig. 12 2. Under a fun- 
nel in a deep glass jar containing 
fresh spring or stream water place 
fresh pieces of the common 
waterweed elodea (or anacharis). 
Have the funnel considerably 
smaller than the vessel, and sup- 
port the funnel well up from the 
bottom so that the plant can more 
readily get all the carbon dioxide 
available in the water. Why would 
boiled water be undesirable in this 
experiment? For a home-made 
glass funnel, crack the bottom off 
a narrow-necked bottle by press- 
ing a red-hot poker or iron rod 
against it and leading the crack 
around the bottle. Invert a test- 
tube over the stem of the fun- 
nel. In sunlight bubbles of 
oxygen will arise and collect in 
the test-tube. If a sufficient 
quantity of oxygen has collected, 
a lighted taper inserted in the 
tube will glow with a brighter flame, showing the presence of 
oxygen in greater quantity than in the air. Shade the vessel. 
Are bubbles given off? For many reasons it is impracticable 
to continue this experiment longer than a few hours. 90. A 
simpler experiment may be made if one of the waterweeds 
Cabomba (water-lily family) is available. Tie a imniber of branches 
together so that the basal ends shall make a smdll bundle. Place 
these in a large vessel of spring water, and insert a test-tube of 
water as before over the bundle. The bubbles will arise from the 
cut surfaces. Observe the bubbles on pond scum and water- 
weeds on a bright day. To illustrate the results of respiration 




Fig. 122. — To show the Escape 
OF Oxygen. 



LEAVES— FUNCTION OR WORK 



103 




Fig. 123. — To ILLUS- 
TRATE A Product 
OF Respiration. 




Fig. 124. — Respira- 
tion OF Thick 
Roots. 



(CO2). 91. In a jar of germinating seeds (Fig. 123) place carefully 
a small dish of limewater and cover tightly. Put a similar dish in 

another jar of about the 

same air space. After a few 

hours compare the cloudi- 
ness or precipitate in the 

two vessels of limewater. 

92. Or, place a growing 

plant in a deep covered 

jar away from the Hght, 

and. after a few hours in- 
sert a lighted candle or 

splinter. 93. Or, perform 

a similar experiment with 

fresh roots of beets or 

turnips (Fig. 124) from 

which the leaves are mostly 

removed. In this case, 
the jar need not be kept dark ; why ? 
To test transpiration. 94. Cut a succulent 
shoot of any plant, thrust the end of it through a hole in a cork, 
and stand it in a small bottle of water. Invert over this a fruit 
jar, and observe 
that a mist soon 
accumulates on 
the inside of the 
glass. In time 
drops of water 
form. 95. The ex- 
periment may be 
varied as shown in 
Fig. 125. 96. Or, 
invert the fruit 
jar over an entire 
plant, as shown in 
Fig. 126, taking 
care to cover the 
soil with oiled 
paper or rubber 
cloth to prevent 
evaporation from 
the soil. 97. The 
test may also be 
made by placing 
the pot, properly 
protected, on bal- Fig. 121;. —To illusprate Transpiration, 




I04 



BEGINNERS' BOTANY 




ances, and the loss of weight will be noticed (Fig. 127). 98. Cut 
a winter twig, seal the severed end with wax, and allow the twig 
to lie several days. It shrivels. There must be some upward 
movement of water even in winter, else plants would shrivel 
and die. 99. To illustrate sap pressure. 
The upward movement of sap water often 
takes place under considerable force. The 
cause of this force, known as root pressure^ 
is not well understood. The pressure varies 
with different plants and under different 
conditions. To illustrate : 
cut off a strong-growing ^:;^^ 

small plant near 
the ground. By 
means of a bit of 
rubber tube attach 
a glass tube with 
a bore of approxi- 
mately the diame- 
ter of the stem. 
Pour in a little 
water. Observe 
the rise of the 
water due to the 
pressure from be- 
low (Fig 128). Some plants yield a large 
amount of water under a pressure sufficient 
to raise a column several feet ; others force 
out Httle, but under consider- 
able pressure (less easily de- 
monstrated). The vital pro- 
cesses {i.e., the life processes). 
100. The pupil 
having studied 
roots, stems, 
and leaves, 
should now 
be able to de- 
scribe the main 
vital functions 
of plants : what 
is the root func- 
tion? stem function? leaf function? 101. What 
is meant by the "sap"? 102. Where and how 
does the plant secure its water? oxygen? car- yig. 128. —To snov; 
bonf hydrogen i nitrogcMi ? sulpWur .^ potassium^ Sap PREiJSURE. 



Fig. 126. — To illustrate 
Transpiration. 




ITG. 127 — Loss OF Water. 



LEAVES— FUNCTION OR WORK 



los 



.alcium? iron? phosphorus? 103. Where is all the starch in the 
world made? What does a starch-factory establishment do? 
Where are the real starch factories ? 104. In 
what part of the twenty-four hours do 
plants grow most rapidly in length? When 
is food formed and stored most rapidly? 
105. Why does corn or cotton turn yellow 
in a long rainy spell? 106. If stubble, 
corn stalks, or cotton stalks are burned 
in the field, is as much plant-food returned 
to the soil as when they are ploughed 
under? 107. What process of plants is 
roughly analogous to perspiration of ani- 
mals? 108. What part of the organic 
world uses raw mineral for food ? 109. Why 
is earth banked over celery to blanch it? 
110. Is the amount of water transpired 
equal to the amount absorbed? HI. Give 
some reasons why plants very close to a 
house may not thrive or may even die. 
112. Why are fruit-trees pruned or thinned 
out as in Fig. 129? Proper balance be- 
tween fop and roof, 113. We have learned 
that the leaf parts and the root parts work 
together. They may be said to balance 
each other in activities, the root supplying pjQ^ ^^^ _ p^^ Apple 
the top and the top supplying the root tree, with suggestions 
(how?). If half the roots were cut from as to pruning when it 
a tree, we should expect to reduce the top is set in the orchard. At 
also, particularly if the tree is being trans- ''J^ "^^°^^ * P'^""^'^ 
planted. How would you prune a tree or °^* 
bush that is being transplanted? Fig. 130 may be suggestive. 






Fig. 129. — Before and after Pruning. 



CHAPTER XIV 

DEPENDENT PLANTS 

Thus far we have spoken of plants that have roots and 
foliage and that depend on themselves. They collect the 
raw materials and make them over into assimilable food. 
They are independent. Plants without green foliage can- 
not make food ; they 
must have it made for 
them or they die. 
They are dependent. A 
sprout from a potato 
tuber in a dark cellar 
cannot collect and elab- 
orate carbon dioxide. It 
lives on the food stored 
. ,, , r in the tuber. 

Fig. 131. — A Mush ROOM, example of a sapro- 
phytic plant. This is the edible cultivated All plmits witJl fiatU- 

"^"'^'^°°"^- rally white or blanched 

parts are dependent. Their leaves do not develop. They 
live on organic matter — that which has been made by a 
plant or elaborated by an animal. The dodder, Indian 
pipe, beech drop, coral root among flower-bearing plants, 
also mushrooms and other fungi (Figs. 131, 132) are exam- 
ples. The dodder is common in swales, being conspicuous 
late in the season from its thread-Uke yellow or orange 
stems spreading over the herbage of other plants. One 
kind attacks alfalfa and is a bad pest. The seeds germin- 
ate in the spring, but as soon as the twining stem a:- 

106 




DEPENDENT PLANTS 



107 




Fig. 132.— a Parasitic 
Fungus, magnified. 
The mycelium, or 
vegetative part, is 
shown by the dotted- 
shaded parts ramify- 
ing in the leaf tissue. 
The rounded haus- 
toria projecting into 
the cells are also 
shown. The long 
fruiting parts of the 
fungus hang from the 
under surface of the 
leaf. 



taches itself to another plant, the dod- 
der dies away at the base and becomes 
wholly dependent. It produces flowers 
in clusters and seeds itself freely 
(Fig. 133). 

Parasites and Saprophytes. — A plant 
that is dependent on a living plant or 
animal is a parasite, and the plant or 
animal on which it lives is the host. 
The dodder is a true parasite ; so are 
the rusts, mildews, and other fungi that 
attack leaves and shoots and injure 
them. 

The threads of a parasitic fungus 
usually creep through the intercellular 
spaces in the leaf or the stem and send 
suckers (or haustoria) into the cells 
(Fig. 132). The threads (or the hy- 
phae) clog the air-spaces of the leaf 
and often plug the stomates, 
and they also appropriate and 
disorganize the cell fluids ; thus 



they injure or kill their host. The mass of hyphae 
of a fungus is called mycelium. Some of the 
hyphae finally grow out of the leaf and produce 
spores or reproductive cells that an- 
swer the purpose of seeds in distrib- 
uting the plant (b, Fig. 132). 

A plant that lives on dead or de- 
caying matter is a saprophyte. Mush- 
rooms (Fig. 131) are examples; they 
live on the decaying matter in the dodder in 
soil. Mould on bread and cheese is an Fruit. 




io8 



BEGINNERS' BOTANY 



example. Lay a piece of moist bread on a plate and 
invert a tumbler over it. In a few days it will be mouldy. 
The spores were in the air, or perhaps they had already 
fallen on the bread but had not had opportunity to grow. 
Most green plants are unable to make any direct use of 
the humus or vegetable mould in the soil, for they are not 

saprophytic. The shelf- 
fungi (Fig. 134) are sap- 
rophytes. They are com- 
mon on logs and trees. 
Some of them are perhaps 
partially parasitic, extend- 
ing the mycelium into the 
wood of the living tree 
and causing it to become 
black-hearted (Fig. 134). 
Some parasites spring 
from the ground, as other 
plants do, but they are 
parasitic on the roots of 
their hosts. Some para- 
sites may be partially 
parasitic and partially 
sap7'opJiytic. Many (per- 
haps most) of these 
ground saprophytes are 
aided in securing their 
food by soil fungi, which spread their delicate threads over 
the root-like branches of the plant and act as intermedi- 
aries between the food and the saprophyte. These fungus- 
covered roots are known as mycorrhizas (meaning " fungus 
root"). Mycorrhizas are not peculiar to saprophytes. 
They are found on many wholly independent plants, as, 




Fig. 134. — Tinder Fungus {Pofyporus 
igniarius) on beech log. The external 
part of the fungus is shown below ; the 
heart-rot injury above. 



DEPENDENT PLANTS 



109 




Fig. 135. — Bacteria of Several 
Forms, much magnified. 



for example, the heaths, oaks, apples, and pines. It is 
probable that the fungous threads perform some of the 
offices of root-hairs to the 
host. On the other hand, 
the fungus obtains some 
nourishment from the 
host. The association 
seems to be mutual. 

Saprophytes break 
down or decompose or- 
ganic substances. Chief 
of these saprophytes are 
many microscopic organ- 
isms known as bacteria (Fig. 135). These innumerable 
organisms are immersed in water or in dead animals and 

plants, and in all manner of 
moist organic products. By 
breaking down organic 
combinations, they produce 
decay. Largely through 
their agency, and that of 
many true but microscopic 
fungi, all things pass i?ito 
soil and gas. Thus are the 
bodies of plants and animals 
removed and the continuing 
round of life is maintained. 
Some parasites are green- 
leaved. Such is the mistle- 
toe (Fig. 136). They anchor 
themselves on the host and 
absorb its juices, but they 
also appropriate and use 




Fig. 136. — American Mistletoe 
growing on a Walnut Branch. 



no BEGINNERS' BOTANY 

the carbon dioxide of the air. In some small groups of 
bacteria a process of organic synthesis has been shown to 
take place. 

Epiphytes. — To be distinguished from the dependent 
plants are those that grow on other plants without taking 
food from them. These are green-leaved plants whose 
roots burrow in the bark of the host plant and perhaps 
derive some food from it, but which subsist chiefly on 
materials that they secure from air dust, rain water, and 
the air. These plants are epiphytes (meaning "upon 
plants") or air plants. 

Epiphytes abound in the tropics. Certain orchids are 
among the best known examples (Fig. 37). The Spanish 
moss or tillandsia of the South is another. Mosses and 
lichens that grow 6n trees and fences may also be called 
epiphytes. In the struggle for existence, the plants 
probably have been driven to these special places in which 
to find opportunity to grow. Plants grow where they 
must, not where they will. 

Suggestions. — 114. Is a puffball a plant ? Why do you 
think so? 115. Are mushrooms ever cultivated, and where 
and how? 116. In what locations are mushrooms and toadstools 
usually found? (There is really no distinction between mush- 
rooms and toadstools. They are all mushrooms.) 117. What 
kinds of mildew, blight, and rust do you know? 118. How do 
farmers overcome potato blight? Apple scab? Or any other 
fungous "plant disease"? 119. How do these things injure 
plants? 120. What is a plant disease? 121. The pupil should 
know that every spot or injury on a leaf or stem is caused by 
something, — as an insect, a fungus, wind, hail, drought, or other 
agency. How many uninjured or perfect leaves are there on 
the plant growing nearest the schoolhouse steps? 122. Give 
formula for Bordeaux mixture and tell how and for what it is used. 



CHAPTER XV 



WINTER AND DORMANT BUDS 



A bud is a growing point, terminating an axis either long 
or short, or being the starting point of an axis. All 
branches spring from buds. In the growing season the 
bud is active ; later in the season it ceases to increase the 
axis in length, and as winter approaches the growing 
point becomes more or less thickened and covered by pro- 
tecting scales, in preparation for the long resting season. 
This resting, dormant, or winter body is what is commonly 
spoken of as a "bud." A winter bud may be defined 
as an inactive covered growing pointy waiting for spring. 

Structurally, a dormant bud is a shortened axis or branch, 
bearing miniature leaves or flowei's or bothy and protected 
by a covering. Cut in two, lengthwise, a 
bud of the horse-chestnut or other plant 
that has large buds. With a pin separate 

the tiny leaves. Count them. 

Examine the big bud of the 

rhubarb as it Hes under the 

ground in late winter or early 

spring ; or the crown buds of 

asparagus, hepatica, or other 

early spring plants. Dis- 
sect large buds of the apple 

and pear (Figs. 137, 138). 
The bud is protected by firm and dry scales. These 
scales are modified leaves. The scales fit close. Often 





Fig. 137. — Bud 
OF Apricot, 
showing the 
miniature 
leaves. 



Fig. 138.- Bud OF 
Pear, showing 
both leaves and 
flowers. The 
latter are the lit- 
tle knobs in the 
centre. 



Ill 



112 



BEGINNERS* BOTANY 



the bud is protected by varnish (see horse-chestnut and 
the balsam poplars). Most winter buds are more or less 
woolly. Examine some of them under a lens. As we might 
expect, bud coverings are most prominent in cold and dry 
cHmates. Sprinkle water on velvet or flannel, and note 
the result and give a reason. 

All winter buds give rise to branches, not to leaves alone; 
that is, the leaves are borne on the lengthening axis. 
Sometimes the axis, or branch, remains very short, — so 
short that it may not be noticed. Sometimes it grows 
several feet long. 

Whether the bra7ich grows large or not depends on the 
chance it has, — position on the plant, soil, rainfall, and 
many other factors. The new shoot is the 
unfolding and enlarging of the tiny axis 
and leaves that we saw in the bud. If the 
conditions are congenial, the shoot may 
form more leaves than were tucked away 
in the bud. The length of the shoot usu- 
ally depends more on the length of the 
internodes than on the number of leaves. 

Where Buds are. — Buds are borne in the 
axils of the leaves, — in the acute angle 
that the leaf makes with the stem. When 
the leaf is growing in the summer, a bud 
is forming above it. When the leaf falls, 
the bud remains, and a scar marks the 
place of the leaf. Fig. 139 shows the large leaf-scars of 
ailanthus. Observe those on the horse-chestnut, maple, 
apple, pear, basswood, or any other tree or bush. 

Sometimes two or more buds are borne in one axil ; the 
extra ones are accessory or supernumerary buds. Observe 
them in the Tartarian honeysuckle (common in yards), 




Fig. 139. — Leaf- 
scars. — Ailanthus 



WINTER AND DORMANT BUDS 



113 



walnut, butternut, red maple, honey locust, and sometimes 
in the apricot and peach. 

If the bud is at the end of a shoot, however short the 
shoot, it is called a terminal bud. It continues the growth 
of the axis in a direct line. Very often 
three or more buds are clustered at the tip 
(Fig. 140); and in this case there may be 
more buds than leaf scars. Only one of 
them, however, is strictly terminal. 

A bud in the axil of a leaf is an axillary 
or lateral bud. Note that there is normally 
at least one bud in the axil of every leaf on 
a tree or shrub in late summer and fall. The 
axillary buds, if they grow, are the starting 
points of new shoots the following season. If 
a leaf is pulled off early in summer, what 
will become of the young bud in its axil.? 
Try this. 

Bulbs and cabbage heads may be likened to buds ; that is, 
they are condensed stems, with scales or modified leaves 

densely overlapping 
and forming a 
rounded body (Fig. 
141). They differ 
from true buds, how- 
ever, in the fact 
that they are con- 
densations of whole 
main stems rather 

than embryo stems 
Fig. 141. — a Gigantic Bud. — Cabbage. . Mr 

borne m the axils of 

leaves. But bulblets (as of tiger lily) may be scarcely dis- 
tinguishable from buds on the one hand and from bulbs 



Fig. 140. — TER- 
MINAL Bud 
BETWEEN TWO 

OTHER Buds. 
— Currant. 




114 



BEGINNERS' BOTANY 




on the other. Cut a cabbage head in two, lengthwise, 
and see what it is like. 

The buds that appear on roots are unusual or abnormal, 

— they occur only occasionally and in no definite order. 

Buds appearing in unusual places on any part of the plant 

are called adventitious buds. Such usually are the buds 

that arise when a large limb is cut off, and 

from which suckers 

or water sprouts 

arise. 

How Buds Open. 
— When the bud 
swells, the scales 
are pushed apart, 
the little axis elon- 
gates and pushes 
out. In most plants 
the outside scales 
fall very soon, leaving a little ring of scars. 
With terminal buds, this ring marks the end 
of the year's growth. How? 
Notice peach, apple, plum, 
willow, and other plants. In 
some others, all the scales grow for a time, 
as in the pear (Figs. 142, 143, 144). In 
other plants the inner bud scales become 
green and almost leaf-like. See the maple 
and hickory. 

Sometimes Flowers come out of the 
Buds. — Leaves may or may not accompany 
the flowers. We saw the embryo flowers in 
Fig. 138. The bud is shown again in Fig. 
142. In Fig. 143 it is opening. In Fig. 145 



Fig. 142. — 
Fruit-bud 
OF Pear. 



Fig. 143. — The 
opening of 
THE Pear 
Fruit-bud. 





Fig. 144.— Open- 
ing Pear 
Leaf-bud. 



Fig. 145. — Open- 
ing OF THE 

Pear-bud. 



WINTER AND DORMANT BUDS 



115 



it is more advanced, and the woolly unformed flowers are 
appearing. In Fig. 146 the growth is more advanced. 




Fig. 146.— a sin- 
gle Flower 
IN THE Pear 

CLUSTER, as 
seen at 7 A.M. 
on the day of 
its opening. At 
10 o'clock it 
will be fully ex- 
panded. 




Fig. 147. — The 
opening of 
THE Flower- 
bud OF 
Apricot. 




Fig. /i4^ ^ Apricot 
FLOwfelf-BUD, enlarged. 



leaf-buds. 



Buds that contain or 
produce only leaves are 
Those which contain only flowers are flower 



buds or fruit-buds. The latter occur on 
peach, almond, apricot, and many very 
early spring-flowering plants. The 
single flower is emerging from the 
apricot bud in Fig. 147. A longi- 
tudinal section of this bud, enlarged, is 
shown in Fig. 148. Those that contain 
both leaves and flowers are mixed buds, 
as in pear, apple, and most late spring- 
flowering plants. 

Fruit buds are usually thicker or 
stouter than leaf-buds. They are borne 
in different positions on different plants. 
In some plants (apple, pear) they are 
on the ends of short branches or spurs; 
in others (peach, red maple) they are 

along the sides of the last year's 

° ^ Fig. 149. —Fruit-buds 

growths. In Fig. 149 are shown and Leaf-buds of pear. 




Ii6 



BEGINNERS' BOTANY 



three fruit-buds and one leaf-bud on E, and leaf-buds on 
A, See also Figs. 150, 151, 152, 153, and explain. 





Fig. 150. — Fruit-buds of Apple 
ON Spurs: a dormant bud at 
the top. 



Fig. 151. — Clus- 
ter OF Fruit- 
buds OF SWEET 

Cherry, with 
one pointed 
leaf-bud in cen- 
tre. 




Fig. 152. — Two 
Fruit-buds 
OF Peach 
with a leaf- 
bud between. 




Fig. 153. — Opening of Leaf-buds and Flower-buds of Apple. 

^^The burst of spring'' means in large part the opening of 
the buds. Everything was made ready the fall before. The 
embryo shoots and flowers were tucked aivay, and the food 
was stored. The warm rain falls, and the shutters open 
and the sleepers wake. 

Arrangement of Buds. — We have found that leaves are 
usually arranged in a definite order ; buds are borne in the 
axils of leaves : therefore buds miist exhibit phyllotaxy. 



WINTER AND DORMANT BUDS WJ 

Moreover, branches grow from buds: branches, therefore, 
should show a definite arrangement. Usually, however, they 
do not show this arrangement because not all the buds grow 
and not all the branches live. (See Chaps. II and III.) 
It is apparent, however, that the mode of arrangement of 
buds determines to some extent the form of the tree. Com- 
pare bud arrangement in pine or fir with that in maple or 
apple. 




Fig. 154, — Oak Spray. How are the leaves borne with reference to 
the annual growths ? 

The uppermost buds on any twig, if they are well 
matured, are usually the larger and stronger and they are 
the most likely to grow the next spring; therefore, branches 
tend to be arranged in tiers (particularly well marked in 
spruces and firs). See Fig. 154 and explain it. 

Winter Buds show what has been the Effect of Sunlight. — 
Buds are borne in the axils of the leaves, and ihe si&e or the 
vigour df the leaf determines to a large extent the size of the 
hud. Notice that, in most instances, the largest buds are 
nearest the tip (Fig. 157). If • the largest buds are not 
near the tip, there is some special reason for it. Can you 
state it ? Examine the shoots on trees and bushes. 



Il8 BEGINNERS' BOTANY 

Suggestions. — Some of the best of all observation lessons are 
those made on dormant twigs. There are many things to be 
learned, the eyes are trained, and the specimens are everywhere 
accessible. 123. At whatever time of year the pupil takes up the 
study of branches, he should look for three things : the ages of 
the various parts, the relative positions of the buds and the leaves, the 
different sizes of similar or comparable buds. If it is late in 
spring or early in summer, he should watch the development of 
the buds in the axils, and he should determine whether the 
strength or size of the bud is in any way related to the size and 
the vigour of the subtending (or supporting) leaf. The sizes of buds 
should also be noted on leafless twigs, and the sizes of the former 
leaves may be inferred from the size of the leaf-scar below the 
bud. The pupil should keep in mind the fact of the struggle 
for food and light, and its effects on the developing buds. 
124. The bud and the branch. A twig cut from an apple tree 
in early spring is shown in Fig. 155. The most hasty obser- 
vation shows that it has various parts, or members. It seems to 
be divided at the point / into two parts. It is evident that the 
part from/ to h grew last year, and that the part below/ grew 
two years ago. The buds on the two parts are very unlike, 
and these differences challenge investigation. — In order to under- 
stand this seemingly lifeless twig, it will be necessary to see it as 
it looked late last summer (and this condition is shown in Fig. 
156). The part from / to h, — which has just completed its 
growth, — is seen to have its leaves growing singly. In every axil 
(or angle which the leaf makes when it joins the shoot) is a bud. 
The leaf starts first, and as the season advances the bud forms in 
its axil. When the leaves have fallen, at the approach of winter, 
the buds remain, as seen in Fig. 155. Every bud on the last 
year's growth of a winter twig, therefore, marks the position 
occupied by a leaf when the shoot was growing. — The part below 
/, in Fig. 156, shows a wholly different arrangement. The leaves 
are two or more together {aaaa)y and there are buds without 
leaves {bbbb) . A year ago this part looked like the present shoot 
from f to hy — that is, the leaves were single, with a bud in the 
axil of each. It is now seen that some of these bud-like parts 
are longer than others, and that the longest ones are those which 
have leaves. It must be because of the leaves that they have 
increased in length. The body c has lost its leaves through some 
accident, and its growth has ceased. In other words, the parts 
at aaaa are like the shoot ///, except that they are shorter, and 
they are of the same age. One grew from the end or terminal 
bud of the main branch, and the others from the side or lateral 
buds. Parts or bodies that bear leaves are, therefore, branches. 
«— Tb^ buds at bbbb have no leaves, and they remain the same 



WINTER AND DORMANT BUDS 



119 



size that they were a year ago. They are dormant. The only way 
for a mature bud to grow is by making leaves for itself, for a leaf 



Fig. 155. — An 
Apple Twig. 




Fig. 156.— - Same twig before leaves fell. 



will never stand below it again. The twig, therefore, has buds of 
two ages, — those at M^ s^re two seasons old, and those on th^ 



120 BEGINNERS' BOTANY 

tips, of all the branches {aaaa, h), and in the axil of every leaf, 
are one season old. It is only the terminal buds that are not 
axillary. When the bud begins to grow and to put forth leaves, 
it gives rise to a branch, which, in its turn, bears buds. — It will 
now be interesting to determine why certain buds gave rise to 
branches and why others remained dormant. The strongest 
shoot or branch of the year is the terminal one {fh). The 
next in strength is the uppermost lateral one, and the weakest 
shoot is at the base of the twig. The dormant buds are on the 
under side (for the twig grew in a horizontal position). All this 
suggests that those buds grew which had the best chance, — the 
most sunlight and room. There were too many buds for the space, 
and in the struggle for existence those that had the best oppor- 
tunities made the largest growth. This struggle for existence 
began a year ago, however, when the buds on the shoot below/ 
were forming in the axils of the leaves, for the buds near the tip 
of the shoot grew larger and stronger than those near its base. 
The growth of one year, therefore, is very largely determined by 
the conditions under which the buds were formed the previous 
year. Other dud characters. 125. It is easy to see the swelling 
of the budr in a room in winter. Secure branches of trees and 
shrubs, two to three feet long, and stand them in vases or jars, 
as you would flowers. Renew the water frequently and cut off 
the lower ends of the shoots occasionally. In a week or two the 
buds will begin to swell. Of red maple, peach, apricot, and other 
very early-flowering things, flowers may be obtained in ten to 
twenty days. 126. The shape, size, and colour of the winter buds 
are different in every kind of plant. By the buds alone botanists 
are often able to distinguish the kinds of plants. Even such 
similar plants as the different kinds of willows have good bud 
characters. 127. Distinguish and draw fruit-buds of apple, pear, 
peach, plum, and other trees. If different kinds of maples grow 
in the vicinity, secure twigs of the red or swamp maple, and the 
soft or silver maple, and compare the buds with those of the sugar 
maple and the Norway maple. What do you learn? 




Fig. 157. — Buds of the Hickory, 



CHAPTER XVI 
BUD PROPAGATION 

We have learned (in Chap. VI) that plants propagate 
by means of seeds. They also propagate by means of bud 
parts ^ — as roots toe ks {rhizomes)y roots y runners ^ layers ^ bulbs. 
The pupil should determine how any plant in which he is 
interested naturally propagates itself (or spreads its kind). 
Determine this for raspberry, blackberry, strawberry, June- 
grass or other grass, nut-grass, water hly, May apple or 
mandrake, burdock, Irish potato, sweet potato, buckwheat, 
cotton, pea, corn, sugar-cane, wheat, rice. 

Plants may be artificially propagated by similar means, 
as by layerSy cuttingSy and grafts. The last two we may 
discuss here. 

Cuttings in General. — A bit of a plant stuck into the 
grotmd stands a cJiance of growing ; and this bit is a cutting. 
Plants have preferences, however, as to the kind of bit 
which shall be used, but tJicre is no way of telling what this 
preference is except by trying. In some instances this prefer- 
ence has not been discovered, and we say that the plant 
cannot be propagated by cuttings. 

Most plants prefer that the cutting be made of the soft 
or growing parts (called "wood" by gardeners), of which 
the "slips" of geranium and coleus are examples. Others 
grow equally well from cuttings of the hard or mature parts 
or wood, as currant and grape; and in some instances this 
mature wood may be of roots, as in the blackberry. In 
some cases cuttings are made of tubers, as in the Irish 

121 



122 



BEGINNERS' BOTANY 



potato (Fig. 60). Pupils should make cuttings now and 
then. If they can do nothing more, they can make cut 
tings of potato, as the farmer does; and they can plant 
them in a box in the window. 

The Softwood Cutting. — The softwood cutting is made 
from tissue that is still growing, or at least from that 
which is not dormant. It comprises one or two joints ^ with 





Fig. 158. — Geranium Cutting. 



Fig. 159. — Rose Cutting. 



a leaf attached (Figs. 158, 159). It must not be allowed 
to wilt. Therefore, it must be protected fro^n direct sun- 
light and dry air until it is ivell established ; and if it has 
many leaves ^ some of them shotdd be removed, or at least cut 
in twOy in order to reduce the evaporating sjcrface. The 
soil should be uniformly moist. The pictures show the 
depth to which the cuttings are planted. 

For most plants, the proper age or maturity of wood for 
the making of cuttings may be determined by giving the 
twig a quick bend: if it snaps and hangs by the bark, it is in 
proper condition; if it bends without breaking, it is too 
young and soft or too old ; if it splinters, it is too old and 
woody. The tips of strong upright shoots usually make 
the best cuttings. Preferably, each cutting should have a 
joint or node near its base; and if the internodes are very 
short it may comprise two or three joints. 



BUD PROPAGATION 



123 




Fig. 160. — Cutting-box. 



Tlie st£m of the cutting is inserted one third or more of its 
lengtJi in clean sand or gravel, and the earth is pressed firmly 
about it. A newspaper may be laid over the bed to ex- 
clude the light — if the sun strikes it — and to prevent too 
rapid evaporation. The soil should be moist clear through, 
not on top only. 

Loose sandy or gravelly soil is nsed. Sand used by 
masons is good material in which to start most cuttings; or 
fine gravel — sifted of most 
of its earthy matter — may 
be used. Soils are avoided 
which contain much decay- 
ing organic matter, for these 
soils are breeding places of 
fungi, which attack the soft 
cutting and cause it to " damp 
off," or to die at or near the surface of the ground. If the 
cuttings are to be grown in a window, put three or four 
inches of the earth in a shallow box or a pan. A soap 
box cut in two lengthwise, so that it makes a box four or 
five inches deep — as a gardener's fiat — is excellent (Fig. 
160). Cuttings of common plants, as geranium, coleus, 

fuchsia, carnation, are kept at a 
living-room temperature. As long 
as the cuttings look bright and 
green, they are in good condition. 
It may be a month before roots 
form. When roots have formed, 
the plants begin to make new 
leaves at the tip. Then they may 
be transplanted into other boxes 
or into pots. The verbena in Fig, 161 is just ready for 
transplanting. 




Fig. 161. — Verhena Cutting 
ready for transplanting. 



124 



BEGINNERS* BOTANY 




Fig. 162.— Old Geranium Plant 
cut back to make it throw out 
Shoots from which Cuttings 
can be made. 

dow plants are those which 
old. The geranium 
aiid fuchsia cut- 
tings which are 
made in Januaryy 
February y or MarcJi 
will give compact 
blooming plants for 
the 7text winter; 
and thereafter 7iew 
ones should take 
their places (Fig. 

163). 

The Hardwood 
Cutting. — Best re- 
sults with cuttings 
of mature wood are 



It is not always easy to 
find growing shoots from 
which to make the cut- 
tings. The best practice, 
in that case, is to cut back 
an old pi ant y then keep it 
wann and well watered^ 
and thereby force it to throw 
out new shoots. The old 
geranium plant from the 
window garden, or the one 
taken up from the lawn 
bed, may be treated this 
way (see Fig. 162). The 
best plants of geranium 
and coleus and most win- 
are not more than one year 




Fig. 163.- 



Early Winter Geranium, from 
a spring cutting. 



BUD PROPAGATION 



125 



secured when the cuttings are made in the fall and then 
buried until spring in sand ift the cellar. These cuttings 
are usually six to ten inches long. They are not idle while 
they rest. The lower end calluses or heals, and the roots 
form more readily when the cutting is planted in the 
spring. But if the proper season has passed, take cuttings 
at any time in winter, plant them in a deep 
box in the window, and watch. They will 
need no shading or special care. Grape, 
currant, gooseberry, willow, and poplar 
readily take root from the hardwood. 
Fig. 164 shows a currant cutting. It has 
only one bud above the ground. 

The Graft. — When the cutting is inserted 
in a plant rather than in the soil, it is a 
graft ; and the graft may grow. In this 
case the cutting grows fast to the other 
plant, and the two become one. When 
the cutting is inserted in a plant, it is no 
longer called a cutting but a scion ; and the 
plant in which it is inserted is called the 
stock. Fruit trees are grafted in order 
that a ce7'tain variety or kind may be per- 
petuated, as a Baldwin or Ben Davis vari- 
ety of apple, Seckel or Bartlett pear, Navel 
or St. Michael orange. 

Plants have preferences as to the stocks on which they 
will grow ; but zve can find out ivJiat their choice is only 
by making the experiment. The pear grows well on the 
quince, but the quince does not thrive on the pear. 
The pear grows on some of the hawthorns, but it is an 
unwilling subject on the apple. Tomato plants will grow 
on potato plants and potato plants on tomato plants. 



I 



I 



Fig. 164. — Cur- 
rant CUTIING. 



126 BEGINNERS* BOTANY 

When the potato is the root, both tomatoes and potatoes 
may be produced, although the crop will be very small; 
when the tomato is the root, neither potatoes nor tomatoes 
will be produced. Chestnut will grow on some kinds of 
oak. In general, one species or kind is grafted on the 
same species, as apple on apple, pear on pear, orange on 
orange. 

The forming, growing tissue of the stem (on the plants 
we have been discussing) is the cambium (Chap. X), lying 
on the ontside of the woody cy Haider beneath the bark. In 
order that union may take place, the camhium of the scion 
and of the stock must come together. Therefore the scion 
is set in the side of the stock. There are many ways of 
shaping the scion and of preparing the stock to receive it. 
These ways are dictated largely by the relative sizes of 
scion and stock, although many of them are matters of 
personal preference. The underlying principles are two: 
securing close contact between the cambiums of scion and 
stock; covering the ivounded surfaces to prevent evapora- 
tion and to protect the parts from disease. 

On large stocks the commonest form of grafting is the 
cleft-graft. The stock is cut off and split; and in one or 
both sides a wedge-shaped scion is firmly inserted. Fig. 
165 shows the scion; Fig. 166, the scions set in the stock; 
Fig. 167^ the stock waxed. It wall be seen that the lower 
bud — that lying in the wedge — is covered by the wax; 
but being nearest the food supply and least exposed to 
weather, it is the most likely to grow : it will push through 
the wax. 

Cleft-grafting is practised in spring, as growth begins. 
The scions are cut previously, when perfectly dormant, and 
from the tree which it is desired to propagate. The scions 
are kept in sand or moss in the cellar. Limbs of various 



BUD PROPAGATION 



127 



sizes may be cleft-grafted, — from a half inch up to four 
inches in diameter; but a diameter of one to one and a 
half inches is the most convenient size. All the leading 
or main branches of a tree top may be grafted. If the 
remaining parts of the top are gradually cut away and 
the scions grow well, the entire top will be changed over to 
the new variety. 



Fig. 165.— 

SciOIsf OF 

Apple. 





Fig. 166.— The 
Scion Inserted. 



Fig. 167.— The 
Paris Waxed. 



Another form of grafting is known as budding. In this 
case a single bud is used, and it is sHpped underneath the 
bark of the stock and securely tied (not waxed) with soft 
material, as bass bark, corn shuck, yarn, or raffia (the last 
a commercial palm fibre). Budding is performed when the 
bark of the stock will slip or peel (so that the bud can be 
inserted), and when the bud is mature ejiougJi to grow. 
Usually budding is performed in late summer or early 
fall, when the winter buds are well formed ; or it may be 
practised in spring with buds cut in winter. In ordinary 
summer budding (which is the usual mode) the *'bud" or 
scion forms a union with the stock, and then lies dormant 
till the following spring, as if it were still on its own twig. 



128 



BEGINNERS' BOTANY 



Budding is mostly restricted to young trees in the nursery. 
In the spring following the budding, the stock is cut off 
just above the bud, so that only the shoot from the bud 
grows to make the future tree. This prevailing form of 
J budding (shield-budding) is shown in Fig. 

\i 168. 

^ t Suggestions. — 128. Name the plants that the 

■ I gardener propagates by means of cuttings. 

I 129. By means of grafts. 130. The cutting-box 

I may be set in the window. If the box does not 

' receive direct sunlight, it may be covered with a 

pane of glass to prevent evaporation. Take care 
that the air is not kept too close, else the daraping- 
off fungi may attack the cuttings, and they will 
rot at the surface of the ground. See that the 
pane is raised a little at one end to afford ventila- 
tion ; and if the water collects in drops on the 
under side of the glass, remove the pane for a 
time. 131. Grafting wax is made of beeswax, 
resin, and tallow. A good recipe is one part (as 
one pound) of rendered tallow, two parts of bees- 
wax, four parts of resin; melt together in a kettle ; 
pour the liquid into a pail or tub of water to so- 
lidify it; work with the hands until it has the 
colour and " grain" of taffy candy, the hands being 
greased when necessary. The wax will keep any 
length of time. For the little grafting that any 
pupil would do, it is better to buy the wax of a 
seedsman. 132. Grafting is hardly to be recom- 
mended as a general school diversion, as the mak- 
ing of cuttings is ; and the account of it in this 
chapter is inserted chiefly to satisfy the general 
curiosity on the subject. 133. In Chap. V we had 
a definition of a plant generation : what is " one 
generation '* of a grafted fruit tree, as Le Conte 
pear, Baldwin, or Ben Davis apple? 134. The 
Elberta peach originated about i88o : what is 
meant by " originated " ? 135. How is the grape 
propagated so as to come true to name (explain 
what is meant by "coming true")? currant? 
strawberry? raspberry? blackberry? peach? 
pear? orange? fig? plum? cherry? apple? chest- 
nut? pecan? 




rrC. l68. — BUD- 
DING. The 
"bud"; the 
opening to re- 
ceive it ; the 
bud tied. 



CHAPTER XVII 
HOW PLANTS CLIMB 

We have found that plants struggle or contend for a 
place in which to live. Some of them become adapted to 
grow in the forest shade, others to grow on other plants, 
as epiphytes, others to climb to the light. Observe how 
woods grapes, and other forest climbers, spread their foli- 
age on the very top of the forest tree, while their long 
flexile trunks may be bare. 

There are several ways by which plants climb, but most 
climbers may be classified into four groups : ( i ) scramblers, 
(2) root climbers, (3) tendril climbers, (4) twiners. 

Scramblers. — Some plants rise to light and air by rest- 
ing their long and weak stems on the tops of bushes and 
quick-growing herbs. Their stems may be elevated in part 
by the growing twigs of the plants on which they recline. 
Such plants are scramblers. Usually they are provided 
with prickles or bristles. In most weedy swamp thickets, 
scrambling plants may be found. Briers, some roses, bed- 
straw or galium, bittersweet {Solanum Dulcamara^ not the 
Celastrus\ the tear-thumb polygonums, and other plants are 
familiar examples of scramblers. 

Root Climbers. — Some plants climb by means of true 
roots. These roots seek the dark places and therefore 
enter the chinks in walls and bark. The trumpet creeper 
is a famiHar example (Fig. 36). The true or English 
ivy, which is often grown to cover buildings, is another 
instance. Still another is the poison ivy. Roots are 
K 129 



I30 



BEGINNERS' BOTANY 



J'^\y\^^ The fr< 

'% ^vl until it 

' *-k // it attac 

1 ■ 



distinguished from stem tendrils by their irregular of 
indefinite positio7t as well as by their mode of growth. 

Tendril climbers. — A slender coiling part that serves to 
hold a climbing plant to a support is known as a tendril. 

The free end swings or curves 
strikes some object, when 
attaches itself and then coils 
and draws the plant close to the 
support. The spring of the coil 
Fig. 169. — Tendril, to show also allows the plant to move in 
where the coil is changed. ^j^^ ^^y^^^ thereby enabUng the 

plant to maintain its hold. Slowly pull a well-matured 
tendril from its support, and note how strongly it holds 
on. Watch the tendrils in a wind-storm. Uisually the ten- 
dril attaches to the support by coiling about it, but the Vir- 
ginia creeper and the Boston ivy (Fig. 170) attach to walls 
by means of disks 
on the ends of the 
tendrils. 

Since both ends 
of the tendril are 
fixed, when it finds 
a support, the coil- 
ing would tend to 
twist it in two. It 
will be found, how- 
ever, that the tendril 
coils in different di- 
rections in different parts of its length. In Fig. 169, show- 
ing an old and stretched-out tendril, the change of direction 
in the coil occurred at a. In long tendrils of cucumbers 
and melons there may be several changes of direction. 

Tendrils may represent either branches or leaves. In the 




70.— Tendril 
Boston Ivy. 



HOW PLANTS CLIMB 



131 




Virginia creeper and the grape they are branches; they 
stand opposite the leaves in the position of fruit clusters, 
and sometimes one branch of a fruit cluster is a tendril. 
These tendrils are therefore homologous with fruit-clusters, 
and fruit clusters are branches. 

In some plants tendrils are leaflets (Chap. XI). Ex- 
amples are the sweet pea and the common garden pea. In 
Fig. 171, observe the leaf with its two great 
stipules, petiole, six normal leaflets, and two 
or three pairs of leaflet tendrils and a termin- 
al leaflet tendril. The cobea, a common 
garden climber, has a similar arrangement. 
In some cases tendrils are stipules^ as prob- 
ably in the green briers 
(smilax). 

The petiole or midrib 
may act as a tendril, as 
in various kinds of clem- 
atis. In Fig. 172, the 
common wild clematis 
or *' old man vine," this 
mode is seen. 

Twiners. — The entire 
plant or shoot may wind about a support. Such a plant is 
a twiner. Examples are bean, hop, morning-glory, moon- 
flower, false bittersweet or waxwork {Celastriis), some 
honeysuckles, wistaria, Dutchman's pipe, dodder. The 
free tip of the twining branch sweeps about in curves, much 
as the tendril does, until it finds support or becomes old 
and rigid. 

Each kind of plant usually coils in only one direction. 
Most plants coil against the sun, or from the observer's 
left across his front to his right as he faces the plant. 



w"^ 

&(>. 



Fig. 171. — Leaves of Pea, 
— very large stipules, op- 
posite leaflets, and leaflets 
represented by tendrils. 



132 



BEGINNERS' BOTANY 



Examples are bean, morning-glory. The hop twines from 
the observer's right to his l\ left, or with the sun. 




Fig. 172. - Clematis climbing by Leaf-tendril. 

Suggestions. — 136. Set the pupil to watch the behaviour of any 
plant that has tendrils at different stages of maturity. A vigorous 
cucumber plant is one of the best. Just beyond the point of a young 
straight tendril set a stake to compare the position of it. Note 
whether the tendril changes position from hour to hour or day 
to day. 137. Is the tip of the tendril perfectly straight? Why? 
Set a small stake at the end of a strong straight tendril, so that the 
tendril will just reach it. Watch and make drawing. 138- If a 
tendril does not find a support what does it do? 139. To test the 
movement of a free tendril draw an ink line lengthwise of it, and 
note whether the line remains always on the concave side or the 
convex side. 140- Name the tendril-bearing plants that you know. 
141. Make similar observations and experiments on the tips of 
twining stems. 142. What twining plants do you know, and which 
way do they twine? 143. How does any plant that you know 
shoot up? 144. Does the stem of a climbing plant contain more 
or less substance (weight) than an erect self-supporting stem of 
the same height? Explain. 



CHAPTER XVIII 
THE FLOWER — ITS PARTS AND FORMS 

The function of the flower is to produce seed. It is 
probable that all its varied forms and colours contribute 
to this supreme end. These forms and colours please the 
human fancy and add to the joy of living, but the flower 
exists for the good of the plant, not for the good of man. 
The parts of the flower are of two general kinds — those 
that are directly concerned in the production of seedSy and 
those that act as covering atid protecting organs. The 
former parts are known as the essential organs ; the latter 
as the floral envelopes. 

Envelopes. — The floral envelopes usually bear a close 
resemblance to leaves. These envelopes are very com- 
monly of two series or kinds — the 
outer and the inner. The outer series, 
known as the calyx, is usually smaller 
and green. It usually comprises the 
outer cover of the flower bud. The 
calyx is the lowest whorl in Fig. 173. f^^ 173. -flower of 

The inner series, known as the a buttercup in sec- 
corolla, is usually coloured and more 
special or irregular in shape than the calyx. It is the 
showy part of the flower, as a rule. The corolla is the 
second or large whorl in Fig. 173. 

The calyx may be composed of several leaves. . Each 
leaf is a sepal. If it is of one piece, it may be lobed or 
divided, in which case the divisions are called calyx -lobes. 




134 



BEGINNERS' BOTANY 



In like manner, the corolla may be composed of petals, or 
it may be of one piece and variously lobed. A calyx of 
one piece, no matter how deeply lobed, is gamosepalous. 
A corolla of one piece is gamopetalous. When these 
series are of separate pieces, as in Fig. 173, the flower is 
said to be polysepalous and polypetalous. Sometimes both 

series are of separate parts, and 
sometimes only one of them is so 
formed. 

The floral envelopes are ho- 
mologous with leaves. Sepals and 
petals, at least when more than 
three or five, are in more than 
one whorl, and on^ whorl stands 
below another so that the parts 
overlap. They are borne on the 
expanded or thickened end of the 
flower stalk ; this end is the torus. 
In Fig. 173 all the parts are seen 
as attached to the torus. This 
part is sometimes called the re- 
ceptacle, but this word is a common-language term of 
several meanings, whereas torus has no other meaning. 
Sometimes one part is attached to another part, as in the 
fuchsia (Fig. 174), in which the petals are borne on the 
calyx-tube. 

Subtending Parts. — Sometimes there are leaf-like parts 
jusf below the calyx, looking like a second calyx. Such 
parts accompany the carnation flower. These parts are 
bracts (bracts are small specialized leaves); and they form 
an involucre. We must be careful that we do not mistake 
them for true flower parts. Sometimes the bracts are 
large and petal-like, as in the great white blooms of the 




Fig. 174. — Flower of 
Fuchsia in Section. 



THE FLOWER — ITS PARTS AND FORMS 



135 



flowering dogwood : here the real flowers are several, 
small and greenish, forming a small cluster in the centre. 

Essential Organs. — The essential organs are of two 
series. The outer series is composed of the stamens. The 
inner series is composed of the pistils. 

Stamens bear the pollen, which is made up of grains or 
spores, each spore usually being a single plant cell. The 
stamen is of two parts, as is readily seen in Figs. 173, 
174, — the enlarged terminal part or anther, and the stalk 
or filament. The filament is often so short as to seem to 
be absent, and the anther is then said to be sessile. The 
anther bears the pollen spores. It is made up of two or 
four parts (known as sporangia or spore-cases), which 
burst and discharge the 
pollen. When the pollen is 
shedy the stamen dies. 

The pistil has three 




parts : the lowest, or seed- 
bearing part, which is the 
ovary; the stigma at the 
upper extremity, which is 
a flattened or expanded 
surface, and usually rough- 
ened or sticky; the stalk- 
like part or style, connect- 
ing the ovary and the stig- 
ma. Sometimes the style is apparently wanting, and the 
stigma is said to be sessile on the ovary. These parts are 
shown in the fuchsia (Fig. 174). The ovary or seed vessel 
is at a. A long style, bearing a large stigma, projects from 
the flower. See also Figs. 175 and 176. 

Stamens and pistils probably are homologous with leaves. 
A pistil is sometimes conceived to represent anciently a 



Fig. 175.— The Structure of a 
Plum Blossom. 

j«, sepals; f>, petals; sta, stamens; o, ovary; 
s, style; 5^, tig^ma. The pistil consists of 
the ovary, the styl« and the stigma. It 
contains the seed part. The stamens are 
tipped with anthers, in which the pollen is 
borne. The ovary, o, rip*ns into the fruit. 



136 



BEGINNERS' BOTANY 




Fig. 176. — Simple 
Pistils of But- 
tercup, one in 
longitudinal sec- 
tion. 



leaf as if rolled into a tube ; and an anther, a leaf of which 
the edges may have been turned in on the midrib. 

The pistil may be of one part or com- 
partment^ or of many parts. The different 
units or parts of which it is composed are 
carpels. Each carpel is homologous with 
a leaf. Each carpel bears one or more 
seeds. A pistil of one carpel is simple; 
of two or more carpels, compound. Usu- 
ally the structure of the pistil may be de- 
termined by cutting horizontally across the lower or seed- 
bearing part, as Figs. 177, 178 explain. A flower may 
contain a simple pistil (one carpel), as 

the pea (Fig. 177); several simple pis- . ^ 

tils (several separate carpels), as the ^^^^^ If 
buttercup (Fig. 176); or a componnd "^ ^ 

pistil with carpels united, as the Saint 

John's wort (Fig. 1 78) and apple. How fig. 177. - Pistil of 
- . 1 •> A 1 ■» Garden Pea, the 

many carpels m an apple .'' A peach t 

An okra pod ? A bean pod } The 

seed cavity in each carpel is called a 

locule (Latin locus, a place). In these 

l6cules the seeds are boi-ne. 

Conformation of the Flower. — A 
flower that has calyx, corolla, stamens, 
and pistils is said to be complete (Fig. 
173); all others are incomplete. In 
some flowers both the floral envelopes 
are wanting : such are naked. When 
one of the floral envelope series is 

Fig. 178.— Compound wanting, the remaining series is said 
joHiI.^ wort. ^li to be calyx, and the flower is therefore 

has 5 carpels. apCtalOUS (without petals). The knot- 




stamens being pulled 
down in order to dis- 
close it ; also a section 
showing the single 
compartment (com- 
pare Fig. 188). 




THE FLOWER — ITS PARTS AND FORMS 



n? 



weed (Fig. 179), smartweed, buckwheat^ elm are 
examples. 

Some flowers lack the pistils : these are stami- 
nate, whether the envelopes are missing or not. 
Others lack the stamens : these are pistillate. 
Others have neither stamens nor pistils: these 
are sterile (snowball and hydrangea). Those 
that have both stamens and pistils are per- 
fect, whether or not the envelopes are missing. 

Those that lack 
either stamens or 
pistils are imper- 
fect or diclinous. 
Staminate and 
pistillate flowers 
are imperfect or 
diclinous. 

When staminate and pistillate flowers are borne on the 
same plant, e.g. oak (Fig. 180), corn, 
beech, chestnut, hazel, walnut, hickory, 
pine, begonia (Fig. 181), watermelon, 





Fig. 179. — Knotweed, a very common but inconspicu- 
ous plant along hard walks and roads. Two flowers, 
enlarged, are shown at the right. These flowers are 
very small and borne in the axils of the leaves. 




Fig, 180. — Staminate Catkins of 
Oak. The pistillate flowers are in the 
leaf axils, and not shown in this pic- 
ture. 




Fig. 181.— Begonia 
Flowers. 

Staminate at A ; pistil- 
late below, with the 
winged ovary at B. 



138 



BEGINNERS' BOTANY 






gourd, pumpkin, the plant is monoecious (" in one house ") 
When they are on different plants, e.g. poplar, cottonwood, 

bois d'arc, willow (Fig. 182), 
the plant is dioecious (** in two 
houses "). Some varieties of 
strawberry, grape, and mul- 
berry are partly dioecious. Is 
the rose either monoecious 
or dioecious } 

Flowers in which the parts 
of each series are alike are 
said to be regular (as in Figs. 
173, 174, 175). Those in 
which some parts are unlike 
other parts of the same series 
are irregular. Their regularity may be in calyx, as in 
nasturtium (Fig. 183); in corolla (Figs. 184, 185); in the 
Q^ i| stamens (compare nasturtium, catnip, 

Fig. 185, sage); in the pistils. Irregu- 
larity is most frequent in the corolla. 




s 
Fig. 182. — Catkins of a Willow. 

A staminate flower is shown at s, and a 
pistillate flower at /. The staminate 
and pistillate are on different plants. 




Fig. 183. — Flower of 
Garden Nasturtium. 

Separate petal at a. The 
calyx is produced into a 
spur. 




Fig. 185.— 

Flower of 

Catnip. 



Fig. 184. — The Five Pktals 
of the Pansy, detached to 
show the form. 



THE FLOWER — ITS PARTS AND FORMS 1 39 

Various Forms of Corolla. — The corolla often assumes 
very definite or distinct forms, especially when gamopet- 
alous. It may have a long tube with a wide-flaring limb, 
when it is said to be funnelform, as in morning-glory 
and pumpkin. If the tube is very narrow and the limb 
stands at right angles to it, the corolla is salverform, as 
in phlox. If the tube is very short and the limb wide- 
spreading and nearly circular in outline, the corolla is 
rotate or wheel-shaped, as in potato. 

A gamopetalous corolla or gamosepalous calyx is often 
cleft in such way as to make two prominent parts. Such 
parts are said to be lipped or labiate. Each of the lips or 
lobes may be notched or toothed. In 5-membered flowers, 
the lower lip is usually 3-lobed and the upper one 2-lobed. 
Labiate flowers are characteristic of the mint family (Fig. 
185), and the family therefore is called the Labiatae. (Lit- 
erally, labiate means merely "hpped," without specifying the 
number of lips or lobes ; but it is commonly used to desig- 
nate 2-lipped flowers.) Strongly 2-parted polypetalous 
flowers may be said to be labiate ; but the term is of ten- 
est used for gamopetalous co- 
rollas. 

Labiate gamopetalous flowers 
that are closed in the throat (or 
entrance to the tube) are said to 
be grinning or personate (per- 
sonate means masked). Snap- fig. 186. -personate flower 

. y f QP Toadflax. 

dragon is a typical example; 

also toadflax or butter-and-eggs (Fig. 186), and many 
related plants. Personate flowers usually have defin- 
ite relations to insect pollination. Observe how an 
insect forces his head into the closed throat of the toad- 
flax. 




140 



BEGINNERS' BOTANY 



The peculiar flowers of the pea tribes are explained in 
Figs. 187, 188. 

Spathe Flowers. — In many plants, very simple (often 
naked) flowers are borne in dense, more or less fleshy 
spikes, and the spike is niclosed in or attended by a leaf, 
sometimes corolla-like, known as a spathe. The spike of 
flowers is technically known as a spadix. This type of 
flower is characteristic of the great arum family, which is 




Fig. 187. — Flowers of the 
Common Bean, with one 
flower opened (a) xo show 
the structure. 



Fig. 188. — Diagram of Alfalfa Flower 
IN Section: 

C, calyx, Z), standard; W, wing; K, keel; T, sta- 
men-tube; F, filament of tenth stamen; X^ 
stigma; K, style; <9, ovary; the dotted lines at 
E show position of stamen-tube, when pushed 
upward by insects. Enlarged. 



chiefly tropical. The commonest wild representatives are 
Jack-in-the-pulpit, or Indian turnip, and skunk cabbage. In 
the former the flowers are all diclinous and naked. In the 
skunk cabbage all the flowers are perfect and have four se- 
pals. The common calla is a good example of this type of 
inflorescence. 

Composite Flowers. — The head (anthodium) or so- 
called "flower" of sunflower (Fig. 189), thistle, aster, 
dandelion, daisy, chrysanthemum, goldenrod, is com- 
posed of several or many little flowers^ or florets. These 



THE FLOWER — ITS PARTS AND FORMS 



141 




Fig. 189. — Head of Sunflower, 



florets are inclosed in a more or less dense and usually 
green involucre. In the thistle (Fig. 1 90) this involucre is 
prickly. A longitudinal 
section discloses the flo- 
rets, all attached at bot- 
tom to a common torus, 
and densely packed in 
the involucre. The pink 
tips of these florets con- 
stitute the showy part of 
the head. 

Each floret of the this- 
tle (Fig. 190) is a com- 
plete flower. At a is the ovary. At ^ is a much-divided 
plumy calyx, known as the pappus. The corolla is long- 
tubed, rising above the pappus, and is enlarged and 5-lobed 

at the top, c. The style pro- 
jects at e. The five anthers 
are united about the style in 
a ring at d. Such anthers 
are said to be syngenesious. 
These are the various parts 
of the florets of the Com- 
positae. In some cases the 
pappus is in the form of 
barbs, bristles, or scales, and 
sometimes it is wanting. 
The pappus, as we shall see 
later, assists in distributing 
the seed. Often the florets 
are not all alike. The corolla 
of those in the outer circles may be developed into a long, 
straplike, or tubular part, and the head then has the ap- 




FiG, 190. — Longitudinal Section 
OF Thistle Head; also a Floret 
OF Thistle. 



142 



BEGINNERS' BOTANY 



pearance of being one flower with a border of petals. Of 
such is the sunflower (Fig. 189), aster, bachelor's button or 
cornflower, and field daisy (Fig. 211). These long corolla- 
limbs are called rays. In some cultivated composites, all 
the florets may develop rays, as in the dahlia and the chry- 
santhemum. In some species, as dandelion, all the florets 
naturally have rays. Syngenesious arrangement of an- 
thers is the most characteristic single feature of the 
composites. 

Double Flowers. — Under the stimulus of cultivation and 
increased food supply, flowers tend to become double. 

True doubling arises 
in two ways, mor- 
phologically : (i)j/'<2- 
mcjis or pistils may 
produce petals (Fig. ■ 
191) ; (2) adventi- 
tious or accessory 
petals may arise in 
the circle of petals. 
Both these cate- 
gories may be pres- 
ent in the same 
flower. In the full 
double hollyhock the petals derived from the staminal col- 
umn are shorter and make a rosette in the centre of the 
flower. In Fig. 192 is shown the doubling of a daffodil 
by the modification of stamens. Other modifications of 
flowers are sometimes known as doubling. For example, 
double dahlias, chrysanthemums, and sunflowers are forms 
in which the disk flowers have developed rays. The snow- 
ball is another case. In the wild snowball the external 
flowers of the cluster are large and sterile. In the culti- 




FiG. 191. — Petals arising from the Stami- 
nal Column of Hollyhock, and accessory 
petals in the corolla-whorl. 



THE FLOWER — ITS PARTS AND FORMS 1 43 

vated plant all the flowers have become large and sterile^ 
Hydrangea is a similar case. 




Fig. 192. — Narcissus or Daffodil. Single flower at the right. 

Suggestions. — 14S. If the pupil has been skilfully conckieted 
through this chapter by jneans of careful study of specimens rather 
than as a mere memorizing process, he will be in mood to chal- 
lenge any flower that he sees and to make an effort to understand 
it. Flowers are endlessly modified in form; but they can be 
understood if the pupil looks first for the anthers and ovaries. 
How may anthers and ovaries always be distinguished? 146. It is 
excellent practice to find the flowers in plants that are commonly 
known by name, and to determine the main points in their struc- 
ture. What are the flowers in Indian corn? pumpkin or squash? 
celery? cabbage? potato? pea? tomato? okra? cotton? rhubarb? 
chestnut? wheat? oats? 147. Do all forest trees have flowers? 
Explain. 148. Name all the monoecious plants you know. 
Dioecious. 149. What plants do you know that bloom before 
the leaves appear? Do any bloom after the leaves fall? 150. Ex- 
plain the flowers of marigold, hyacinth, lettuce, clover, asparagus, 
garden calla, aster, locust, onion, burdock, lily-of-the-valley, crocus. 
Golden Glow, rudbeckia, cowpea. 151. Define a flower. 

Note to the Teacher. — It cannot be urged too often that 
the specifnens thefnselves be studied. If this chapter becomes a 
mere recitation on names and definitions, the exercise will be 
worse than useless. Properly taught by means of the flowers 
themselves, the names become merely incidental and a part of 
the pupil's language, and the subject has living interest. 



CHAPTER XIX 



THE FLOWER — FERTILIZATION AND POLLINATION 




Fertilization. — Seeds result from the union of two ele- 
ments or parts. One of these elements is a cell-nucleus 
of the pollen-grain. The other ele- 
ment is the cell-nucleus of an egg- 
cell, borne in the ovary. The 
pollen-grain falls on the stigma 
(Fig. 193). It absorbs the juices 
exuded by the stigma, and grows 
by sending out a tube (Fig. 194). 
This tube grows downward through 
the style, absorbing food as it goes, 
and finally reaches the egg-cell in 
the interior of an ovule in the 
ovary (Fig. 195), and fertilization, 
or union of a nucleus of the pollen and the 
nucleus of the egg-cell in the ovule, takes place. 
The ovule and embryo within then develops 
into a seed. The growth of the pollen-tube is 
often spoken of as germination of the pollen, 
but it is not germination in the sense in which 
the word is used when speaking of seeds. 

Better seeds — that is, those that produce 
stronger and more fruitful plants — often re- 
sult when thQ pollen comes from another flower. 
Fertilization effected between different flowers 
is cross -fertilization ; that resulting from the 

144 



Fig. 193. — B, Pollen escap- 
ing from anther ; A, pollen 
germinating on a stigma. 
Enlarged. 




Fig. 194.— 
A Pollen- 
grain AND 
THE Grow. 
iNG Tube. 



THE FLO WER — PER TILIZA TION AND POLLINA TION 145 




application of pollen to pistils in the same flower is close- 
fertilization or self-fertilization. It will be seen that the 
cross-fertilization relationship may be of many degrees — 
between two flowers in the same cluster, between those 
in different clusters on the same 
branch, between those on different 
plants. Usually fertilization takes 
place only between plants of the 
same species or kind. 

In many cases there is, in effect, 
an apparent selection of pollen when 
pollen from two or more sources is 
applied to the stigma. Sometimes 
the foreign pollen, if from the same 
kind of plant, grows, and fertiliza- 
tion results, while pollen from the 
same flower is less promptly effec- 
tive. If, however, no foreign pol- 
len is present, the pollen from the 
same flower may finally serve the 
same purpose. 

In order that the pollen may grow, the stigma must be 
ripe. At this stage the stigma is usually moist and some- 
times sticky. A ripe stigma is said to be receptive. The 
stigma may remain receptive for several hours or even 
days, depending on the kind of plant, the weather, and how 
soon pollen is received. Watch a certain flower every day 
to see the anther locules open and the stigma ripen. When 
fertilization takes place, the stigma dies. Observe, also, 
how soon the petals wither after the stigma has received 
pollen. 

Pollination. — The transfer of the pollen from anther 
to stigma is known as pollination. The pollen may 



Fig. 195. — Diagram to 
represent fertiliza- 
TION. 

J, stigma; j/, style; <»z', ovary; o, 
ovule; p, pollen-grain; pt, 
pollen-tube; e, egg-cell; tn, 
micropyle. 



146 BEGINNERS* BOTANY 

fall of its own weight on the adjacent stigma, or it 
may be carried from flower to flower by wind, insects, or 
other agents. There may be self-pollination or cross-pol- 
lination, and of course it must always precede fertilization. 
Usually the pollen is discharged by the burst- 
ing of the anthers. The commonest method of 
discharge is through a slit on either side of the 
anther (Fig. 193). Sometimes it discharges 
through a pore at the apex, as in azalea (Fig. 
Anther OF 196), rhododendron, huckleberry, wintergreen. 
Azalea, Jj^ some plants a part of the anther wall raises 

opening by 

terminal or falls as a Udy as in barberry (Fig. 197), blue 

pores. cohosh. May apple. The opening of an anther 

(as also of a seed-pod) is known as dehiscence {de^ from ; 

hisco, to gape). When an anther or seed pod opens, it is 

said to dehisce. 

Most flowers are so constructed as to increase the chances 
of cross-pollination. We have seen that the stigma may 
have the power of choosing foreign pollen. The 
commonest means of necessitating cross-pollina- 
tion is the different times of maturing of stamens 
and pistils in the same flower. In most cases 
the stamens mature first: the flower is then 
proterandrous. When the pistils mature first, 
the flower is proterogynous. {Ancr, andr, is a 
Greek root often used, in combinations, for sta- barherry 
men, and jrytte for pistil.) The difference in stamen, 

' ^-^ ^ ^ ^ with anther 

time of ripenmg may be an hour or two, or it opening by 
may be a day. The ripening of the stamens "^• 
and the pistils at different times is known as dichogamy, and 
flowers of such character are said to be dichogamous. 
There is little chance for dichogamous flowers to pollinate 
themselves. Many flowers are imperfectly dichogamous — 




THE FLO WER — FER TILlZA TTON AND POLLINA TION 147 

some of the anthers mature simultaneously with the pistils, 
so that there is chance for self-pollination in case for- 
eign pollen does 
not arrive. Even 
when the stigma 
receives pollen 
from its own 
flower, cross-fer- 
tilization may 
result. The hol- 
lyhock is proter- 
androus. Fig. 
198 shows a 

flower recently fig. 198. — flower of hollyhock; proterandrous. 

expanded. The centre is occupied by the column of sta- 
mens. In Fig. 199, showing an older flower, the long 
styles are conspicuous. 

Some flowers are so constructed as to prohibit self-polli- 
nation. Very irregular flowers are usually of this kind. 

With some of them, 
the petals form a 
sac to inclose the 
anthers and the pol- 
len cannot be shed 
on the stigma but is 
retained until a bee 
forces the sac open ; 
the pollen is rubbed 
on the hairs of the 

bee and transported. 

Fig. 199. — Older Flower OF Hollyhock. -d ^ i a 

^ Regular flowers usu- 

ally depend mostly on dichogamy and the selective power 
of the pistil to insure crossing Flowers that are very 




148 



BEGINNERS' BOTANY 




irregular and provided with nectar and strong perfume are 
usually pollinated by insects. Gaudy colours probably at- 
tract insects in many cases, but perfume appears to be a 
greater attraction. 

The insect visits the flower for the 
nectar (iox the making of honey) and 
may unknowingly carry the pollen. 
Spurs and sacs in the flower are necta- 
ries (Fig. 200), but in spurless flowers 
the nectar is usually secreted in the 
bottom of the flower cup. This compels 
the insect to pass by the anther and 
Fig. 200.— Flower of rub against the pollen before it reaches 
ARKSPUR. ^j^^ nectar. Sometimes the anther is a 

long lever poised on the middle point and the insect 
bumps against one end and lifts 
it, thus bringing the other end 
of the lever with the pollen sacs 
down on its back. Flowers that 
are pollinated by insects are said 
to be entomophilous (" insect lov- 
ing "). Fig. 200 shows a larkspur. 
The envelopes are separated in 
Fig. 201. The long spur at once 
suggests insect pollination. The 
spur is a sepal. Two hollow 
petals project into this spur, ap- 
parently serving to guide the 
bee's tongue. The two smaller 
petals, in front, are peculiarly 
coloured and perhaps serve the bee in locating the nectary. 
The stamens ensheath the pistils (Fig. 202). As the insect 
stands on the flower and thrusts its head into the centre, 




Fig. 201. — Envelopes of a 
Larkspur. There are five 
wide sepals, the upper one be- 
ing spurred. There arc four 
small petals. 



THE FL O WER— FER TILIZA TION AND POLLINA TION 149 



the envelopes are pushed downward and outward and 
the pistil and stamens come in contact with its abdomen. 
Since the flower is proterandrous, the 
pollen that the pistils receive from the 
bee's abdomen must come from another 
flower. Note a somewhat similar ar- 
rangement in the toadflax or butter-and- 
eggs. 

In some cases (Fig. 203) the stamens 
are longer than the pistil in one flower 
and shorter in another. If the insect 
visits siich flowers, it gets pollen on its 
head from the long-stamen flower, and 
deposits this pollen on the stigma in the 
long-pistil flower. Such flowers are di- 
morphous (of two forms). If pollen from its own flower 
and from another flower both fall on the stigma, the proba- 
bilities are that the stigma will choose the foreign pollen. 




Fig. 202. — Stamens 
OF Larkspur, sur- 
rounding the pistils. 




Fig. 203.— Dimorphic Flowers of Primrose. 

Many flowers are pollinated by the wind. They are said 
to be anemophilous ('^wind loving"). Such flowers pro- 



ISO 



BEGINNEJ^S' BOTANY 



duce great quantities of pollen, for much of it is wasted. 
They usually have broad stigmas, which expose large 
surfaces to the wind. They are usually lacking in gaudy 
colours and in perfume. Grasses and pine trees are typical 
examples of anemopliilous plants. 

In many cases cross-pollination is assured because the 

stamens and the pistils are in different flowers (diclinous). 

. Monoecious and 

, , /A. >v 1 A.- 



I'lt 




dioecious plants 
may be polli- 
nated by wind or 
insects, or other 
agents (Fig. 204). 
They are usually 
wind - pollinated, 
although willows 
are often, if not 
mostly, insect- 
pollinated. The 
Indian corn is a 
monoecious plant. 
The staminate 
flowers are in a 
terminal panicle 
(tassel). The pistillate flowers are in a dense spike (ear), 
inclosed in *a sheath or husk. Each " silk " is a style. 
Each pistillate flower produces a kernel of corn. Some- 
times a few pistillate flowers are borne in the tassel and a 
few staminate flowers on the tip of the ear. Is self-fertili- 
zation possible with the corn ? Why does a " volunteer " 
stalk standing alone in a garden have only a few grains 
on the ear } What is the direction of the prevailing wind 
in summer? If only two or three rows of. corn are 






Fig. 204. — Flowers of Black Walnut : two pis- 
tillate flowers at ^, and staminate catkins at B. 



THE FL O WER — PER T I LIZA TION AND POLLINA TION 1 5 1 



planted in a garden where prevailing winds occur, in which 
direction had they better run? 

Although most flowers are of such character as to insure 
or increase the chances of cross-pollination, there are some 
that absolutely forbid crossing. These flowers are usually 
borne beneath or on the 
ground, and they lack 
showy colours and per- 
fumes. They are known 
as cleistogamous flowers 
( meaning self -fertilizing 
flowers). The plant has 
normal showy flowers 
that may be insect-pol- 
linated, and in addition 
is provided with these 
simplified flowers. Only 
a few plants bear cleis- 
togamous flowers. Hog- 
peanut, common blue 
violet, fringed winter- 
green, and dalibarda are 
the best subjects in 
this country. Fig. 

205 shows a cleistoga- 
mous flower of the blue 
violet at a. Above the 
true roots, slender stems bear these flowers, that are 
provided with a calyx, and a curving corolla which does 
not open. Inside are the stamens and the pistils. Late in 
the season the cleistogamous flowers may be found just 
underneath the mould. They never rise above ground. 
The following summer one may find a seedling plant, in 




Fig. 205. — Common Blue Violet. The 
familiar flowers are shown, natural size. 
The corolla is spurred. Late in the season, 
cleistogamous flowers are often borne on 
the surface of the ground. A small one is 
shown at a. A nearly mature pod is shown 
at b. Both a and b are one third natural 
size. 



152 



BEGINNERS* BOTANY 



some kinds of plants, w;th the remains of the old cleistog- 
amous flower still adhering to the root. Cleistogamous 
flowers usually appear after the showy flowers have 




Fig. 206. — Pods of Peanuts ripening underground. 

passed. They seem to insure a crop of seed by a 
method that expends little of the plant's energy. The 
pupil will be interested to work out the fruiting of the pea- 
nut (Fig. 206). 
Unbaked fresh 
peanuts grow 
readily and can 
easily be raised 
in Canada, in 
a warm sandy 
garden. 

Suggestions. — 
152. Not all the 
flowers produce 
seeds. Note that 
an apple tree may 
bloom very full, 
but that only rela- 
tively few apples 
may result (Fig. 207). More pollen is produced than is needed to 
fertilize the flowers; this increases the chances that sufficient 




Fig. 207. 



-Struggle for Existence among the 
Apple Flowers. 



THE FLOWER^ FERTILIZA TION AND POLLINA TION 1 53 

Stigmas will receive acceptable pollen to enable the plant to 
perpetuate its kind. At any time in summer, or even in fall, 
examine the apple trees carefully to determine whether any dead 
flowers or flower stalks still remain about the apple ; or, examine 
any full-blooming plant to see whether any of the flowers fail. 
153. Keep watch on any plant to see whether insects visit it. 
What kind? When? What for? 154. Determine whether the 
calyx serves any purpose in protecting the flower. Very carefully 
remove the calyx from a bud that is normally exposed to heat 
and sun and rain, and see whether the flower then fares as well as 
others. 155. Cover a single flower on its plant with a tiny paper 
or muslin bag so tightly that no insect can get in. If the flower 
sets fruit, what do you conclude? 156. Remove carefully the 
corolla from a flower nearly ready to open, preferably one that has 
no other flowers very close to it. Watch for insects. 157. Find 
the nectar in any flower that you study. 158. Remove the stigma. 
What happens ? 159. Which of the following plants have perfect 
flowers : pea, bean, pumpkin, cotton, clover, buckwheat, potato, 
Indian corn, peach, chestnut, hickory, watermelon, sunflower, cab- 
bage, rose, begonia, geranium, cucumber, calla, willow, cotton- 
wood, cantaloupe ? What have the others ? 160. On wind- 
pollinated plants, are either anthers or stigmas more numerous ? 
161. Are very small coloured flowers usually borne singly or in 
clusters ? 162. Why do rains at blooming time often lessen 
the fruit crop ? 163. Of what value are bees in orchards ? 
164. The crossing of plants to improve varieties or to obtain new 
varieties. — It may be desired to perform the operation of polli- 
nation by hand. In order to insure the most definite results, 
every effort should be made rightly to apply the pollen which it 
is desired shall be used, and rigidly to exclude all other pollen. 
{a) The first requisite is to remove the anthers from the flower 
which it is proposed to cross, and they must be removed before the 
pollen has been shed. The flower-bud is therefore opened and the 
anthers taken out. Cut ofl* the floral envelopes with small, sharp- 
pointed scissors, then cut out or pull out the anthers, leaving only 
the pistil untouched ; or merely open the corolla at the end and 
pull out the anthers with a hook or tweezers ; and this method is 
often the best one. It is best to delay the operation as long as 
possible and yet not allow the bud to open (and thereby expose 
the flower to foreign pollen) nor the anthers to discharge the 
pollen, (^b) The flower must next be covered with a paper bag to 
prevent the access of pollen (Figs. 208, 209). If the stigma is not 
receptive at the time (as it usually is not), the desired pollen is 
not applied at once. The bag may be removed from time to time 
to allow of examination of the pistil, and when the stigma is 
mature, which is told by its glutinous or roughened appearance, 



154 



BEGINNERS* BOTANY 



the time for" pollination has come. If the bag is slightly moist- 
ened, it can be puckered more tightly about the stem of the plant. 
The time required for the stigma to mature varies from several 
hours to a few days, {c) When the stigma is ready, an unopened 
anther from the desired flower is crushed on the finger nail or a 
knife blade, and the pollen is rubbed on the stigma by means of a 
tiny brush, the point of a knife blade, or a sliver of wood. The 





Fig. 208.— a Paper Bag, 
with string inserted. 



Fig. 209. — The Bag tied 
OVER A Flower. 



flower is again covered with the bag, which is allowed to remain 
for several days until all danger of other pollination is past. Care 
must be taken completely to cover the stigmatic surface with 
pollen, if possible. The seeds produced by a crossed flower pro- 
duce hybrids^ or plants having parents belonging to diff'erent 
varieties or species. 165. One of the means of securing new 
forms of plants is by making hybrids. Why ? 




Fig. 210. The figr «" ^ hollow torus with flowers borne on th« inside, 

and pollinated hy insects ihat enrer at the apex. 



CHAPTER XX 



FLOWER-CLUSTERS 



have seen that 
Sometimes the 



Origin of the Flower-cluster. — We 

branches arise from the axils of leaves, 
leaves may be reduced to bracts 
and yet branches are borne in 
their axils. Some of the branches 
grow into long limbs ; others be- 
come short spurs; others bear 
flowers. In fact, a flower is it- 
self a specialized branch. 

Flowers are usually borne 
near the top of the plant. Often 
they are produced in great num- 
bers. It results, therefore, that 
flower branches usually stand 
close together, forming a clus- 
ter. The shape and the arrange- 
ment of the flower-cluster differ 
with the kind of plants since 
each plant has its own mode of 
branching. 

Certain definite or well-marked 
types of flower-clusters have re- 
ceived names. Some of these 
names we shall discuss, but the 
flower-clusters that perfectly match the definitions are the 
exception rather than the rule. The determining of the 

XS5 




Fig. 211. —Terminal Flowers 

OF THE WHITEWEED (in some 
places called ox-eye daisy). 



ise 



BEGLWNERS* BOTANY 



kip is of flower-clusters is one of the most perplexing sub- 
jects in descriptive botany. We may classify the subject 
aronnd three ideas : solitary flowers, centrifugal or deter- 
minnte clusters, centripetal or indeterminate clusters. 

Solitary Flowers. — In many cases flowers are borne 
singly; they are separated from other flowers by leaves. 
Tbey are then said to be solitary. The solitary flower may 

be either at the end of the 
main shoot or axis (Fig. 2\\\ 
when it is said to be terminal ; 
or from the side of the shoot 
(Fig. 212), when it is said to 
be lateral or axillary. 

Centripetal Clusters. — If 
the flower-bearing axils were 
rather close together, an open 
or leafy flower-cluster might 
result. If the plant continues 
to grow from the tip, the 
older flowers are left farther 
and farther behind. If the 
cluster were so short as to be 
flat or convex on top, the out- 
ermost flowers would be the 
older. A flower-cluster in which the lower or outer flowers 
open first is said to be a centripetal cluster. It is some- 
times said to be an indeterminate cluster, since it is the 
result of a type of growth which may go on more or less 
continuously from the apex. 

The simplest form of a definite centripetal cluster is a 
raceme, which is an open elongated cluster in which the 
flowers are boi-ne singly on very short branches and open 
from below (that is, from the older part of the shoot) 




Fig. 212, — Lateral Flower of 
AN Abutilon. a greenhouse 
plant. 



FLOWER-CLUSTERS 



157 



upwards (Fig. 213). The raceme may be terminal to the 
main branch; or it may be lateral to it, as in Fig. 214^ 

Racemes often bear the 
flowers on one side of 
the stem, thus form- 
ing a single row. 
When a cen- 
tripetal flower- 
cluster is long 
and dense and 
the fl9wers are 
sessile or nearly so, 
it is called a spike 
(Fig. 215). Common 
examples of spikes 
are plantain, migno- 
nette, mullein. 

A very short and 
dense spike ^s a. head. 
Clover (Fig. 216) is 
a good example. The 
sunflower and related 
plants bear many 
small flowers in a 
very dense and often flat head. Note that in the 
sunflower (Fig. 189) the outside or exterior flowers 



Fig. 215.— 
Spike of 
Plantain. 




Fig. 213.— Raceme of Currant. 
Terminal or lateral ? 




Fig. 214. — Lateral Racemes (in fruit) of Barberry. 



158 



BEGINNERS' BOTANY 



open first. Another special form of spike is the catkin, 
which usually has scaly bracts, the whole cluster being 
deciduous after flowering or fruiting, and the flowers (in 
typical cases) having only stamens or pistils. Examples 

are the "pussies" of willows (Fig. 

182) and flower-clusters of oak (Fig. 

180), walnuts (Fig. 204), poplars. 





Fig. 216. — Head of Clo- 
ver Blossoms. 



Fig. 217. — Corymb of Candy- 
tuft. 



When a loose, elongated centripetal flower-cluster has 
some primary branches simple, and others irregularly 
branched, it is called a panicle. It is a branching raceme. 
Because of the earlier growth of the lower branches, the 
panicle is usually broadest at the base or conical in outline. 
True panicles are not very common. 

When an indeterminate flower-cluster is short, so that 



FLOWER^CLUSTERS 1 59 

the top is convex or flat ^ it is a corymb (Fig. 217). The 
outermost flowers open first Centripetal flower-clusters 
are sometimes said to be corymbose in mode. 

When the branches of an indeterminate cluster arise from 
a common pointy like the frame of an umbrella, the cluster 
is an umbel (Fig. 218). Typical umbels occur in carrot, 
parsnip, caraway, and other plants of the parsley family : 
the family is known as the Umbelliferae, or umbel-bearing 




Fig. 218. — Remains of a Last Year's Umbel of Wild Carrot. 

family. In the carrot and many other Umbelliferae, there 
are small or secondary umbels, called umbellets, at the end 
of each of the main branches. (In the centre of the wild 
carrot umbel one often finds a single, blackish, often 
aborted flower, comprising a i -flowered umbellet.) 

Centrifugal or Determinate Clusters. — When the ter- 
minal or central flower opens first, the cluster is said to be 
centrifugal. The growth of the shoot or cluster is deter- 
minate, since the length is definitely determined or stopped 
by the terminal flower. Fig. 219 shows a determinate or 
centrifugal mode of flower bearing. 



i6o 



BEGINNERS* BOTANY 




Dense centrifugal clusters are 
usually flattish on top because of 
the cessation of growth in the 
main or central axis. These com- 
pact flower-clusters are known 
as cymes. Centrifugal clusters 
are sometimes £aid to be cymose 
in mode. Apples, pears (Fig. 
220), and elders bear flowers in 
cymes. Some cyme-forms are 
like umbels in general appear- 
ance. A head-like cymose clus- 
ter is a glomerule ; it blooms from 
the top downwards rather than 
from the base upwards. 

Mixed Clusters. — Often the 
cluster is mixed, being determi- 
nate in one part and indeterminate 
in another part of the same clus- 
ter. The main cluster may be indeterminate, but the 
branches determinate. The cluster has the appearance of 
a panicle, and is usually so called, but it is really a thyrse. 
Lilac is a familiar example of a 
thyrse. In some cases the main 
cluster is determinate and the 
branches are indeterminate, as in 
hydrangea and elder. 

Inflorescence. — The mode or 
method of flower arrangement is 
known as the inflorescence. That 
is, the inflorescence is cymose, co- 
rymbose, paniculate, spicate, solitary, determinate, inde- 
terminate. By custom, however, the word " inflorescence " 



Fig. 219. — Determinate or 
Cymose Arrangement.— 
Wild geranium. 




Fig. 220. — Cyme of Pear. 
Often imperfect. 



FLO WER-CL USTERt, 



i6i 





M 


\ 


3 . 


\ 


2 


\ 






1 2 3 t* !♦ 3 2 . '^ 




Fig. 221. — Forms of Centripetal Flower-clusters. 

Z* raceme; 2, spike; 3, umbel; 4, head or anthodium ; 5, corymb. 




Fig. 222. — Centripetal iNFLORESCEfiCE, continued. 

6, spadix ; 7, compound umbel ; 8, catkin. 



WW 




./^ 



?/ 



Fig. 223. — Centrifugal Inflorescence. 

I, cyme; 2, scirpioid raceme (or half cyme). 



1 62 BEGINNERS' BOTANY 

has come to be used in works on descriptive botany for 
the flower-cluster itself. Thus a cyme or a panicle may be 
called an inflorescence. It will be seen that even solitary 
flowers follow either indeterminate or determinate methods 
of branching. 

The flower-stem. — The stem of a solitary flower is 
known as a peduncle; also the general stem of 2i flower- 
cluster. The stem of the individual flower in a cluster is 
a pedicel. In the so-called stemless plants the peduncle 
may arise directly from the ground, or crown of the plant, 
as in dandelion, hyacinth, garden daisy ; this kind of 
peduncle is called a scape. A scape may bear one or 
many flowers. It has no foliage leaves, but it may have 
bracts. 

Suggestions. — 166. Name six columns in your notebook as 
follows : spike, raceme, corymb, umbel, cyme, solitary. Write 
each of the following in its appropriate column : larkspur, grape, 
rose, wistaria, onion, bridal wreath, banana, hydrangea, phlox, 
China berry, lily-of-the-valley, Spanish dagger (or yucca), sorghum, 
tuberose, hyacinth, mustard, goldenrod, peach, hollyhock, mul- 
lein, crepe myrtle, locust, narcissus, snapdragon, peppergrass, 
shepherd's purse, coxcomb, wheat, hawthorn, geranium, carrot, 
elder, millet, dogwood, castor bean ; substitute others for plants 
that do not grow in your region. 167. In the study of flower- 
clusters, it is well to choose first those that are fairly typical of the 
various classes discussed in the preceding paragraphs. As soon 
as the main types are well fixed in the mind, random clusters 
should be examined, for the pupil must never receive the impres- 
sion that all flower-clusters follow the definitions in books. Clus- 
ters of some of the commonest plants are very puzzling, but the 
pupil should at least be able to discover whetljer the inflorescence 
is determinate or indeterminate. Figures 221 to 223 illustrate the 
theoretical modes of inflorescence. The numerals indicate the order 
of opening. 



CHAPTER XXI 
FRUITS 

The ripened ovary, with its attachments, is known as the 
fruit. It contains the seeds. If the pistil is simple, or of 
one carpel, the fruit 
also will have one com- 
partment. If the pistil 
is compound, or of 
more than one carpel, 
the fruit usually has an 
equal number of com- 
partments. The com- 
partments in pistil and 
fruit are known as lo- 
cules (from Latin locus^ 
meaning "a place"). 

The simplest kind 
of fruit is a ripened 
\-loculed ovary. The 
first stage in complex- fig. 224.. 
ity is a ripened 2- or 
many-loculed ovary. Very complex forms may arise by the 
attachment of other parts to the ovary. Sometimes the style 
persists and becomes a beak (mustard pods, dentaria, 
Fig. 224), or a tail as in clematis ; or the calyx may be 
attached to the ovary ; or the ovary may be embedded in 
the receptacle, and ovary and receptacle together consti- 
tute the fruit ; or an involucre may become a part of the 

16^ 




Dentaria, or Tooth-wort, in 

fruit. 



164 



^EGINNEIiS' BOTANY 



fruit, as possibly in the walnut and the hickory (Fig. 225), 
and the cup of the acorn (Fig. 226). The chestnut and the 
beech bear a prickly involucre, but the nuts, 




Fig. 225. — Hickory-nut. 
The nut is the fruit, con- 
tained in a husk. 




Fig. 226. — Live-oak Acorn. 
The fruit is the " seed " part ; 
the involucre is the " cup." 



or true fruits, are not grown fast to it, and the involucre 
can scarcely be called a part of the fruit. A ripened ovary 
is a pericarp. A pericarp to which other parts adhere has 
been called an accessory or reenforced fruit. (Page 169.) 
Some fruits are dehiscent, or split open at maturity and 
liberate the seeds ; others are indehiscent, or do not open. 
A dehiscent pericarp is called a / pod 
The parts into which such 
a pod breaks or splits are 
known as valves. In inde- 
hiscent fruits the seed is 
hberated by the decay of 
the envelope, or by the 
rupturing of the envelope 
by the germinating seed. 
Indehiscent winged peri- 
carps are known as samaras or key fruits. 





Fig. 227. — Key of 
Sugar Maple. 



Fig. 228. — Key 

of Common 
American Elm. 



Maple (Fig. 



227), elm (Fig. 228), and ash (Fig. 93) are examples. 



FRUITS 



165 





Fig. 229.— 
Akenes of 
Buttercup. 



Fig. 230. — Akenes 
OF Buttercup, 
one in longitudi- 
nal section. 



Pericarps. — The simplest pericarp is a dry, one- 
seeded, indehiscent body. It is known as an akene. A 
head of akenes is shown in Fig. 229, and the 
structure is explained in Fig. 
230. Akenes may be seen in 
buttercup, hepatica, anemone, 
smartweed, buckwheat. 

A i-loculed pericarp which 
dehisces along the front edge 
(that is, the inner edge, next 
the centre of the flower is a follicle. The fruit of the 
larkspur (Fig. 231) is a follicle. There are usually five of 
these fruits (sometimes three or 
four) in each larkspur flower, each 
pistil ripening into a follicle. If 
these pistils were united, a single 
compound pistil would be formed. 
Columbine, peony, ninebark, milk- 
weed, also have folHcles. 

A i-loculed pericarp that de- 
hisces on both edges is a legume. 
Peas and beans are typical exam- 
ples (Fig. 232); in fact, this character gives 
name to the pea family, — Leguminosae. 
Often the valves of the 
legume twist forcibly and 
expel the seeds, throwing 
them some distance. The 
word " pod " is sometimes restricted to 
legumes, but it is better to use it generi- 
cally /or all dehiscent pericarps. 

A compound pod — dehiscing peri- 
carp of two or more carpels — is a capsule (Figs. 233, 234,* 




Fig. 231.— 
Follicle 
OF Lark- 
spur. 





Fig. 232.— a 
Bean Pod. 



Fig. 233. — Capsule of 
Castor - oil Bean 
AFTER Dehiscence. 



i66 



BEGINNERS' BOTANY 




Fig. 234. — Cap- 
sule OF Morn- 
ing Glory. 



236, 237). Some capsules are of one 
locule, but they may have been compound 
when young (in the ovary stage) and the 
partitions may have vanished. Sometimes 
one or more of the carpels are uniformly 
crowded out by the exclusive growth of 
other carpels (Fig. 235). The seeds or 
parts which are crowded out are said to 
be aborted. 

There are several ways in which cap- 
sules dehisce or open. When they break 
along the partitions (or septa), the mode is known as septi- 
cidal dehiscence (Fig. 236); 
In septicidal dehiscence the 
fruit separates into parts 
representing the original 
carpels. These carpels 
may still be entire, and 
they then dehisce individu- 
ally, usually along the inner 
edge as if they were follicles. When the compartments 

split ill the middle^ between the 
partitions, the mode is loculicidal 
dehiscence (Fig. 237). In some 
cases the dehiscence is at the top, 
when it is said to be apical (al- 
though several modes of dehis- 
cence are here included). When 
the luhole top comes off, as in purs- 
lane and garden portulaca (Fig. 
238), the pod is known as a pyxis. In some cases apical 
dehiscence is by means of a hole or clefts. 

The peculiar capsule of the mustard family, or Cruci- 




Fig. 235. — Three-carpeled Fruit 
OF Horse-chestnut. Two locules 
are closing by abortion of the ovules. 





Fig. 236. — 
St. John's 
Wort. Sep- 
ticidal. 



Fig. 237. — 
Loculici- 
dal Pod of 
Day-lily. 



FRUITS 



167 



ferae, is known as a silique when it is distinctly longer than 
broad (Fig. 224), and a silicle when its breadth nearly 





Fig. 238. — Pyxis of Poktu- 
LACA OR Rose-moss. 



Fig. 239. — Berries of Goose- 
berry. Remains of calyx at c^ 



equals or exceeds its length. A cruciferous capsule is 
2-carpeled, with a thin partition, each locule containing 
seeds in two rows. The two valves detach from below 
upwards. Cabbage, turnip, mustard, water-cress, radish, 

rape, shepherd's purse, 
sweet alyssum, wall- 
flower, honesty, are 
examples. 




Fig. 240.— Berry of the Ground Cherry 
or Husk Tomato, contained in the inflated 
calyx. 

The pericarp may h^ fleshy and 
indehiscent. A pulpy pericarp 
with several or many seeds is a 
berry (Figs. 239, 240, 241). To 
the horticulturist a berry is a 
small, soft, edible fruit, without 




Fig. 241.— Orange; example 
of a berry. 



1 68 



BEGINNERS' BOTANY 




particular reference to its structure. The botanical and 
horticultural conceptions of a berry are, therefore, unlike. 
In the botanical sense, gooseberries, currants, grapes, to- 
matoes, potato-balls, and even eggplant fruits and oranges 
(Fig. 241) are berries; strawberries, raspberries, black- 
berries are not. 

A fleshy pericarp containing one relatively large seed 
or stone is a drupe. Examples are plum (Fig. 242), peach, 
cherry, apricot, olive. The walls of 
the pit in the plum, peach, and cherry 
are formed from the inner coats of 
the ovary, and the flesh from the 
outer coats. Drupes are also known 
as stone-fruits. 

Fruits that are formed by the sub- 
sequent union of separate pistils are 
aggregate fruits. The carpels in 
aggregate fruits are usually more or less fleshy. In the rasp- 
berry and the blackberry flower, the pistils are essentially 
distinct, but as the 
pistils ripen they co- 
here and form one 
body(Figs. 243, 244). 






Fig. 243. — Fruit of Rasp- 
berry. 



Each of the carpels or pistils in the 
raspberry and the blackberry is a 
little drupe or drupelet. In the 
raspberry the entire fruit separates 
from the torus, leaving the torus on 
the plant. In the blackberry and 



Fig. 242. — Plum; exam- 
ple of a drupe. 





Fig. 244. — Aggregate 

Fruit of Mulberry; 

and a separate fruit. 



FRUITS 



169 



the dewberry the fruit adheres to the torus, and the two are 

removed together when the fruit is picked. 
Accessory Fruits. — When the pericarp and some other 

part grow together, the fruit is said to be accessory or 
reenforced. An example is the straw- 
berry (Fig. 245). The edible part is a 
greatly ett large d tonis, and the pericarps 
are akenes embedded in it. These akenes 
are commonly called seeds. 

Various kinds of reenforced fruits have 
received special names. One of these is 
the hip, characteristic of roses. In this 
case, the torus is deep and hollow, like an 
urn, and the separate akenes are borne 
inside it. The mouth of the receptacle 

may close, and the walls sometimes become fleshy ; the 

fruit may then be mistaken for a berry. The fruit of the 

pear, apple, and quince is known as a 




{i'lG. 245. — Straw- 
berry; fleshy 

torus in which akenes 
are embedded. 





Fig. 246. — Section of 
AN Apple. 



Fig. 247. — Cross-section 
OF AN Apple. 



pome. In this case the five united carpel? are completely 
buried in the hollow torus, and the torus makes most of 
the edible part of the ripe fruit, while the pistils are repre- 
sented by the core (Fig. 246). Observe the sepals on the 
top of the torus (apex of the fruit) in Fig. 246. Note 
the outUnes of the embedded pericarp in Fig. 247. 



I70 BEGINNERS' BOTANY 

Gymnospermous Fruits. — In pine, spruces, and their kin, 
there is no fruit in the sense in which the word is used 
in the preceding pages, because the^-e is 7to ovary. The 
ovules are naked or uncovered, in the axils of the scales of 
the young cone, and they have neither style nor stigma. 
The pollen falls directly on the mouth of the ovule. The 
ovule ripens into a seed, which is usually winged. Because 
the ovule is not borne in a sac or ovary, these plants are 
called gymnosperms (Greek for "naked seeds"). All the 
true cone-bearing plants are of this class; also certain 
other plants, as red cedar, juniper, yew. The plants are 
monoecious or sometimes dioecious. The staminate flowers 
are mere naked stamens borne beneath scales, in small 
yellow catkins which soon fall. The pistillate flowers are 
naked ovules beneath scales on cones that persist (Fig. 
29). Gymnospermous seeds may have several cotyledons. 

Suggestions. — 168. Study the following fruits, or any five fruits 
chosen by the teacher, and answer the questions for each: Apple, 
peach, bean, tomato, pumpkin. What is its form? Locate the 
scar left by the stem. By what kind of stem was it attached? 
Are there any remains of the blossom at the blossom end? De- 
scribe texture and colour of surface. Divide the fruit into the seed 
vessel and the surrounding part. Has the fruit any pulp or flesh? 
Is it within or without the seed vessel? Is the seed vessel simple 
or sub-divided? What is the number of seeds? Are the seeds 
free, attached to the wall of the vessel, or to a support in the 
centre? Are they arranged in any order? What kind of wall has 
the seed vessel? What is the difference between a peach stone 
and a peach seed? 169. The nut fruits are always available for 
study. Note the points suggested above. Determine what the 
meat or edible part represents, whether cotyledons or not. Figure 
248 is suggestive. 170- Mention all the fleshy fruits you know, 
tell where they come from, and refer them to their proper groups. 
171. What kinds of fruit can you buy in the market, and to what 
groups or classes do they belong? Of which fruits are the seeds 
only, and not the pericarps, eaten? 172. An ear of corn is always 
available for study. What is it— a fruit or a collection of fruits? 
How are the grains aranged on the cob? How many rows do 
you count on each of several ears? Are all the rows on an ear 



FRUITS 17, 

equally close together? Do you find an ear with an odd number 
of rows? How do the parts of the husR overlap? Does the 
husk serve as protection from rain? Can birds pick out the grains? 
How do insect enemies enter the ear? How and when do weevils 
lay eggs on corn? 173. Study a grain of corn. Is it a seed? 
Describe the shape of a grain. Colour. Size. Does its surface 
show any projections or depressions! Is the seed-coat thin or 
thick? Transparent or opaque? Locate the hilum. Where is 
the silk scar? What is the silk? Sketch the grain from the two 
points of view that show it best. Where is the embryo? Does 
the grain have endosperm ? What is dent corn? Flint corn? 
How many kinds of corn do you know? For what are they used? 





Fig. 248. — Pecan 
Fruit. 




Note to Teacher. — There are few more interesting subjects 
to beginning pupils than fruits, — the ■j)ods of many kinds, forms, 
and colours, the berries, and nuts. This interest may well be 
utilized to make the teaching alive. All common edible fruits 
of orchard and vegetable garden should be brought into this dis- 
cussion. Of dry fruits, as pods, burs, nuts, collections may be 
made for the school museum. Fully mature fruits are boat for 
study, particularly if it is desired to see dehiscence. For com- 
parison, pistils and partially grown fruits should be had at the 
same time. If the fruits are not ripe enough to dehisce, they 
may be placed in the sun to dry. In the school it is well to have 
a collection of fruits for study. The specimens may be kept in 
glass jars. Always note exterior of fruit and its parts; interior 
of fruit with arrangement and attachment of contents. 



CHAPTER XXII 



DISPERSAL OF SEEDS 



It is to the plant's advantage to have its seeds distributed 
as widely as possible. // has a better chance of sjirviving 
in the struggle for existence. It gets away from competi- 
tion. Many seeds and fruits are of such character as to 
increase their chances of wide dispersal. The commonest 
means of dissemination may be classed under four heads : 
explosive fruits ; transportation by wind ; transportation by 
birds ; burs. 





Fig. 249. -^ Explosion of 
THE Balsam Pod. 



Fig. 250. — Explosive 
Fruits of Oxalis. 

An exploding pod is shown 
at c. The dehiscence is 
shown at l>. The structure 
of the pod is seen at a. 



Explosive Fruits. — Some pods open with explosive force 
and discharge the seeds. Even beans and everlasting peas 
do this. More marked examples are the locust, witch 
hazel, garden balsam (Fig. 249), wild jewel-weed or impa- 
tiens (touch-me-not), violet, crane's-bill or wild geranium, 
bull nettle, morning glory, and the oxalis (Fig. 250). The 

172 



DISPERSAL OF SEEDS 



173 



oxalis is common in several species in the wild and in 
cultivation. One of them is known as wood sorrel. Figure 
250 shows the common yellow oxaHs. The pod opens 
loculicidally. The elastic tissue suddenly contracts when 
dehiscence takes place, and the seeds are thrown violently. 
The squirting cucumber is easily grown in a garden (pro- 
cure seeds of seedsmen), and the fruits discharge the seeds 
with great force, throwing them many 
feet. 

Wind Travelers. — Wind -transported 
seeds are of two general kinds : those 
that are provided with wingSy as the flat 
seeds of catalpa (Fig. 251) and cone-bear- 
ing trees and the samaras of ash, elm, 
tulip-tree, ailanthus, and maple; and 
those which have feathery buoys or para- 
chutes to enable them to float in the air. 
Of the latter kind are the fruits of many 
composites, in which the pappus is 
copious and soft. Dandelion and thistle 
are examples. The silk of the milkweed 
and probably the hairs on the cotton seed 
have a similar office, and also the wool of 
the cat-tail. Recall the cottony seeds of 
the willow and the poplar. 

Dispersal by Birds. — Seeds of berries and of other 
small fle&hy fruits are carried far and wide by birds. The 
pulp is digested, but the seeds are not injured. Note how 
the cherries, raspberries, blackberries, June-berries, and 
others spring up in the fence rows, where the birds rest. 
Some berries and drupes persist far into winter, when they 
supply food to cedar birds, robins, and the winter birds. 
Red cedar is distributed by birds. Many of these pulpy 




Fig. 251. — Winged 
Seeds of Catalpa. 



174 



BEGINNERS' BOTANY 



fruits are agreeable as human food, and some of them 
have been greatly enlarged or " improved " by the arts of 
the cultivator. The seeds are usually indigestible. 

Burs. — Many seeds and fruits bear spines, hooks, and 
hairs, which adhere to the coats of animals a7id to clothing. 
The burdock has an involucre with hooked scales, contain- 
ing the fruits inside. The clotbur is also an involucre. 
Both are composite plants, allied to thistles, but the 
whole head, rather than the separate 
fruits, is transported. In some com- 
posite fruits the pappus takes the 
form of hooks and spines, as in the 
" Spanish bayonets " and " pitch- 
forks." Fruits of various kinds are 
known as "stick tights," as of the 
agrimony and hound's-tongue. Those 
who walk in the woods in late sum- 
mer and fall are aware 
that plants have means 
of disseminating them- 
selves (Fig. 252). If it 
is impossible to iden- 
tify the burs which one 
finds on clothing, the seeds may be planted and specimens 
of the plant may then be grown. 




Fig. 252. — Stealing a Ride. 



Suggestions. — 174. What advantage is it to the plant to have 
its seeds widely dispersed? 175. What are the leading ways in 
which fruits and seeds are dispersed? 176. Name some explosive 
fruits. 177. Describe wind travelers. 178. What seeds are car- 
ried by birds? 179. Describe some bur with which you are 
familiar. 180. Are adhesive fruits usually dehiscent or indehis- 
cent? 181. Do samaras grow on low or tall plants, as a rule? 
182. Are the cotton fibres on the seed or on the fruit? 183. 
Name the ways in which the common weeds of your region are 
disseminated. 184. This lesson will suggest other ways in which 



DISPERSAL OF SEEDS 



175 



seeds are transported. Nuts are buried by squirrels for food ; but 
if they are not eaten, they may grow. Tiie seeds of many plants 
are blown on the snow. The old stalks of weeds, standing through 
the winter, may serve to disseminate the plant. Seeds are carried 
by water down the streams and along shores. About woollen mills 
strange plants often spring up from seed brought in the fleeces. 
Sometimes the entire plant is rolled for miles before the winds. 
Such plants are " tumbleweeds." Examples are Russian thistle, 
hair grass or tumblegrass {Panicu7n capillare), cyclone plant 
{Cycioloma platyphyllujti)^ and white amaranth {Amaranti4s 
albus). About seaports strange plants are often found, having 
been introduced in the earth that is used in ships for ballast. 
These plants are usually known as " ballast plants." Most of them 
do not persist long. 185. Plants are able to spread themselves by 
means of the great numbers of seeds that they produce. How 
many seeds may a given elm tree or apple tree or raspberry bush 
produce ? 




Fig. 253. — The Fruits 
OF THE Cat-tail are 

LOOSENED BY WiND 

AND Weather. 



CHAPTER XXIII 



PHENOGAMS AND CRYPTOGAMS 




Fig. 254. — Christmas Fern. 
— Dryopteris acrostichoides ; 
known also as Aspidium. 



The plants thus far studied produce flowers; and the 

flowers produce seeds by means of which the plant is prop- 
agated. There are other plants, 
however, that produce no seeds, 
and these plants (including bac- 
teria) are probably more numer- 
ous than the seed-bearing plants. 
These plants propagate by means 
of spores, which are generative cells ^ 
tisiially simple y containing no em- 
bryo. These spores are very small, 
and sometimes are not visible to 
the naked eye. 
Prominent among the spore- 
propagated plants are ferns. The 

common Christmas fern (so called 

because it remains green during 

winter) is shown in Fig. 254. The 

plant has no trunk. The leaves 

spring directly from the ground. 

The leaves of ferns are called 

fronds. They vary in shape, as 

other leaves do. Some of the 

fronds in Fig. 254 are seen to be F'«- ^55- fruiting frond 

OF Christmas Fern. 

narrower at the top. If these are „ , ^ . ^ . , 

Son at a. One sorus with its in- 

examined more closely (Fig. 255), dusiumat^. 

176 




PHENOGAMS AND CRYPTOGAMS 



177 



it will be seen that the leaflets are contracted and are 
densely covered beneath with brown bodies. These bodies 
are collections of sporangia or spore-cases. 





Fig. 256. — Common Polypode Fern. 
Polypodium vulgare. 



Fig. 257. — Sori and Spo- 
rangium of Polypode. 
A chain of cells lies along 
the top of the sporangium, 
which springs back elasti- 
cally on drying, thus dis- 
seminating the spores. 




Fig. 258. — The Brake 
Fruits underneath 
THE Revolute 
Edges of the Leaf. 



The sporangia are collected into little groups, known as 
sori (singular, sorus) or fruit-dots. Each sorus is covered 
with a thin scale or shield, known as 
an indusium. This indusium sepa- 
rates from the frond at its edges, and 
the sporangia are exposed. Not all 
ferns have indusia. The polypode 
(Figs. 256, 257) does not; the sori 
are naked. In the brake (Fig. 258) 

and maidenhair (Fig. 259) the 
edge of the frond turns over 
and forms an indusium. The 
nephrolepis or sword fern of 
greenhouses is allied to the 
polypode. The sori are in a 
single row on either side the 
midrib (Fig. 260). The indu- 
sium is circular or kidney- 
Fig. 259.— Fruiting Pinnules 

OF Maidenhair Fern. shaped and open at one edge 




1/8 



BEGINNERS' BOTANY 




Fig. 260. — Part of Frond of 
Sword Fern. To the pupil : Is 
this illustration right side up ? 



or finally all around. The 
Boston fern, Washington fern, 
Pierson fern, and others, are 
horticultural forms of the 
common sword fern. In some 
ferns (Fig. 261) an entire 
frond becomes contracted to 
cover the sporangia. • 
The sporangium or spore-case of a fern is a more or less 
globular body and usually with a stalk (Fig. 257). // con- 
tarns the spoi'es. When ripe it 
bursts and the spores are set free. 
In a moist, warm place the spores 
germinate. They produce a small, 
flat, thin, green, more or less heart- 
shaped membrane (Fig. 262). This 
is the prothallus. Sometimes the 
prothallus is an inch or more across, 
but oftener it is less than a ten cent 
piece in size. Although easily 
seen, it is commonly unknown ex- 
cept to botanists. Prothalli may 
often be found in greenhouses where ferns are grown. 

Look on the moist stone or 
brick walls, or on the firm soil 
of undisturbed pots and beds ; 
or spores may be sown in a 
damp, warm place. 

On the under side of the 
prothallus two kinds of organs 

are borne. These are the 
Fig. 262. — Prothallus of a , . / . • • 

FERN. Enlarged. archegonium (contammg ^gg- 

Archegonia at a ; antheridia at b. CcUs) and the anthcridium (COU- 




FiG. 261.— Fertile and 

Sterile Fronds of the 

Sensitive Fern. 




PHENOGAMS AND CRYPTOGAMi> 179 

taining sperm-cells). These organs are minute specialized 
parts of the prothallus. Their positions on a particular 
prothallus are shown at a and b in Fig. 262, but in some 
ferns they are on separate prothalli (plant dioecious). The 
sperm-cells escape from the a7itheridinm and in the water 
that collects on the prothallus are carried to the archegoniumy 
where fertilizatiori of the egg takes place. From the ferti- 
lized egg-cell a plant grows, becoming a "fern." In 
most cases the prothallus soon dies. The prothallus is the 
gametophyte (from Greek, signifying the fertilized plant). 

The fern plant, arising from the fertilized 0,^^ in the 
archegonium, becomes a perennial plant, each year pro- 
ducing spores from its fronds (called the sporophyte) ; but 
these spores — which are merely detached special kinds of 
cells — produce the prothallic phase of the fern plant, 
from which new individuals arise. A fern is fertilized but 
once in its lifetime. The "fern" bears the spore, the 
spore gives rise to the prothallus, and the egg-cell of the 
prothallus (when fertilized) gives rise to the fern. 

A similar alternation of generations runs all through the 
vegetable kingdom, although there are some groups of 
plants in which it is very obscure or apparently wanting. 
It is very marked in ferns and mosses. In algae (includ- 
ing the seaweeds) the gametophyte is the " plant," as 
the non-botanist knows it, and the sporophyte is incon- 
spicuous. There is a general tetidency, in the evolution of 
the vegetable kingdo^n^ for the gametophyte to lose its rela- 
tive importance a7id for the sporophyte to become larger and 
more highly developed. In the seed-bearing plants the 
sporophyte generation is the only one seen by the non- 
botanist. The gametophyte stage is of short duration and 
the parts are small ; it is confined to the time of fertiliza« 
tion. 



l80 BEGINNERS' BOTANY 

The sporophyte of seed plants, or the ** plant" as we 
know it, produces two kinds of spores — one kind becom- 
ing pollen -grains and the other kind embryo-sacs. The 
pollen-spores are borne in sporangia, which are united into 
what are called anthers. The embryo-sac, which contains 
the egg-cell, is borne in a sporangium known as an ovule. 
A gametophytic stage is present in both pollen and embryo 
sac : fertilization takes place^ and a sporophyte arises. Soon 
this sporophyte becomes dormant, and is then known as att 
embryo. The embryo is packed away within tight-fitting 
coats, and the entire body is the seed. When the condi- 
tions are right the seed grows, and the sporophyte grows 
into herb, bush, or tree. The utility of the alternation of 
generations is not understood. 

The spores of ferns are borne on leaves ,- the spores of 
seed-bearing plants are also borne amongst a mass of 
specially developed conspicuous leaves known as flowers ; 
therefore these plants have been known as the flowering 
plants. Some of the leaves are developed as envelopes 
(calyx, corolla), and others as spore-bearing parts, or spo- 
rophyllff (stamens, pistils). But the spores of the lower 
plants, as of ferns and mosses, may also be borne in spe- 
cially developed foliage, so that the line of demarcation 
between flowering plants and flowerless plants is not so 
definite as was once supposed. The one definite distinction 
between these two classes of plants is the fact that 07te class 
produces seeds and the other does not. The seed-plants are 
now often called spermaphytes, but there is no single 
coordinate term to set off those which do not bear seeds. 
It is quite as well, for popular purposes, to use the terms 
phenogams for the seed-bearing plants and cryptogams for 
the others. These terms have been objected to in recent 
years because their etymology does not express literal facts 



PHENOGAMS AND CRYPTOGAMS 



i8i 



{phenogam signifying "showy flowers," and cryptogam 
"hidden flowers"), but the terms represent distinct ideas 
in classification. The cryptogams include three great 
series of plants — the Thallophytes or algae, lichens, and 
fungi ; the Bryophytes or mosslike plants; the Pteridophytes 
or fernlike plants. 

Suggestions. — 186. The parts of a fern leaf The primary 
complete divisions of a frond are called pinnae, no matter whether 
the frond is pinnate or not. In 
ferns the word "pinna" is used in 
essentially the same way that leaf- 
let is in the once-compound leaves 
of other plants. The secondary 
leaflets are called pinnules, and in 
thrice, or more, compound fronds, 
the last complete parts or leaflets 
are ultimate pinnules. The dia- 
gram (Fig. 263) will aid in making 
the subject clear. If the frond 
were not divided to the midrib, it 
would be simple, but this diagram 
represents a compound frond. 
The general outline of the frond, 
as bounded by the dotted line, is 
ovate. The stipe is very short. 
The midrib of a compound frond 
is known as the rachis. In a de- 
compound frond, this main rachis 
is called the primary rachis. Seg- 
ments (not divided to the rachis) 
are seen at the tip, and down to 
h on one side and to m on the 
other. Pinnae are shown at /, k, /, Oy n. The pinna is entire ; 
n is crenate-dentate ; / is sinuate or wavy, with an auricle at the 
base ; k and /are compound. The pinna k has twelve entire pin- 
nules. (Is there ever an even number of pinnules on any pinna?) 
Pinna / has nine compound pinnules, each bearing several entire 
ultimate pinnules. The spores. — 187. Lay a mature fruiting frond 
of any fern on white paper, top side up, and allow it to remain in 
a dry, warm place. The spores will discharge on the paper. 
188. Lay the full-grown (but not dry) cap of a mushroom or 
toadstool bottom down on a sheet of clean paper, under a venti- 
lated box in a warm, dry place. A day later raise the cap. 




Fig. 263. — Diagram to explain 
THE Terminology of the 
Frond. 



CHAPTER XXIV 

STUDIES IN CRYPTOGAMS 

The pupil who has acquired skill in the use of the com- 
pound microscope may desire to make more extended ex- 
cursions into the cryptogamous orders. The following 
plants have been chosen as examples in various groups. 
Ferns are sufficiently discussed in the preceding chapter. 

Bacteria 

If an infusion of ordinary hay is made in water and allowed to 
stand, it becomes turbid or cloudy after a few days, and a drop 
under the microscope will show the presence of minute oblong 
cells swimming in the water, perhaps by means of numerous hair- 
like appendages, that project through the cell wall from the pro- 
toplasm within. At the surface of the dish containing the infusion 
the cells are non-motile and are united in long chains. Each 
of these cells or organisms is a bacterium (plural, bacterid), 

(Fig. 135.) 

Bacteria are very minute organisms, — the smallest known, — 
consisting either of separate oblong or spherical cells, or of 
chains, plates, or groups of such cells, depending on the kind. 
They possess a membrane-like wall which, unlike the cell walls of 
higher plants, contains nitrogen. The presence of a nucleus has 
not been definitely demonstrated. Multiplication is by the fission 
of the vegetative cells ; but under certain conditions of drought, 
cold, or exhaustion of the nutrient medium, the protoplasm of the 
ordinary cells may become invested with a thick wall, thus form- 
ing an endospore which is very resistant to extremes of environ- 
ment. No sexual reproduction is known. 

Bacteria are very widely distributed as parasites and saprp- 
phytes in almost all conceivable places. Decay is largely' caused 
by bacteria, accompanied in animal tissue by the liberation of 
foul-smelling gases. Certain species grow in the reservoirs and 
pipes of water supplies, rendering the water brackish and often 
undrinkable. Some kinds oi fermentation (the breaking down or 
decomposing of organic compounds, usually accompanied by the 

182 



STUDIES IN CRYPTOGAMS ^ 1 83 

formation of gas) are due to these organisms. Other bacteria 
oxidize alcohol to acetic acid, and produce lactic acid in milk and 
hutyric acid in butter. Bacteria live in the mouth, the stomach, the 
intestines, and on the surface of the skins of animals. Some secrete 
gelatinous sheaths around themselves; others secrete sulphur or 
iron, giving the substratum a vivid colour. 

Were it not for bacteria, man could not live on the earth, for 
not only are they agents in the process of decay, but they are 
concerned in certain healthful processes of plants and animals. 
We have learned in Chapter VITT how bacteria are related to nitro- 
gen-gathering. 

Bacteria are of economic importance not alone because of their 
effect on materials used by man, but also because of the disease- 
producing power of certain 'species. Pus is caused by a spherical 
form, tetanus or lock-jaw by a rod-shaped form, diphtheria by 
short oblong chains, tuberculosis or ^^ consumption^' 'hy more slen- 
der oblong chains, and typhoid fever ^ cholera^ and other diseases 
by other forms. Many diseases of animals and plants are 
caused by bacteria. Disease-producing bacteria are said to be 
pathogenic. 

The ability to grow in other nutrient substances than the natu- 
ral one has greatly facilitated the study of these minute forms 
of hfe. By the use of suitable culture media and proper precau- 
tions, pure cultures of a particular disease-producing bacterium 
may be obtained with which further experiments may be con- 
ducted. 

Milk provides an excellent collecting place for bacteria coming 
from the air, from the coat of the cow and from the milker. Dis- 
ease germs are sometimes carried in milk. If a drop of milk is 
spread on a culture medium (as agar), and provided with proper 
temperature, the bacteria will multiply, each one forming a colony 
visible to the naked eye. In this way, the number of bacteria 
originally contained in the milk may be counted. 

Bacteria are disseminated in water, as the germ of typhoid fever 
and cholera; in milk and other fluids; in the air; and on the 
bodies of flies, feet of birds, and otherwise. 

Bacteria are thought by many to have descended from algae by 
the loss of chlorophyll and decrease in size due to the more 
specialized acquired saprophytic and parasitic habit. 

ALGiE 

The algae comprise most of the green floating " scum*" which 
covers the surfaces of ponds and other quiet waters. The masses 
of plants are often called '' frog spittle." Others are attached to 
stones, pieces of wood, and other objects submerged in streams 



1 84 



BEGINNERS' BOTANY 



and lakes, and many are found on moist ground and on dripping 
rocks. Aside from these, all the plants commonly known as seaweeds 
belong to this category ; these latter are inhabitants of salt water. 
The simplest forms of algae consist of a single spherical cell, 
which multiplies by repeated division or fission. • Many of the 
forms found in fresh water are filamentous, i.e. the plant body 
consists of long threads, either simple or branched. Such a plant 
body is termed a ihallus. This term applies to the vegetative 
body of all plants that are not differentiated into stem and leaves. 
Such plants are known as thallophytes (p. i8i). All algae contain 
chlorophyll, and are able to assimilate carbon dioxide from the air. 
This distinguishes them from the fungi. 

Nostoc. — On wet rocks and damp soil dark, semitransparent 
irregular or spherical gelatinous masses about the size of a pea are 
often found. These consist of a colony of contorted filamentous 
algae embedded in the jelly-like mass. The chain of cells in the 
filament is necklace-like. Each cell is homogeneous, without 
apparent nucleus, and blue-green in colour, except one cell which 
is larger and clearer than the rest. The plant therefore belongs 
to the group of blue-green algce. The jelly probably serves to 
maintain a more even moisture and to provide mechanical protec- 
tion. Multiplication is wholly by the breaking 
up of the threads. Occasionally certain cells 
of the filament thicken to become resting- 
sporesy but no other spore formation occurs. 

Oscillatoria. — The blue-green coatings 
found on damp soil and in water frequently 
show under the microscope the presence of 
filamentous algae composed of many short 



Fig. 264. —Filament of Oscillatoria, showing one 
dead cell where the strand will break. 

homogeneous cells (Fig. 264). If watched 
closely, some filaments will be seen to wave 
back and forth slowly, showing a peculiar power 
of movement characteristic of this plant. 
Multiplication is by the breaking up of the 
threads. There is no true spore formation. ' 

Spirogyra. — One of the most common forms 
of the green algae is spirogyra (Fig. 265). This 



Fig. 265. — Strand 
OF Spirogyra, 
showing the chlo- 
rophyll bands. 
There is a nu- 
cleus at a. How 
many cells, or 
parts of cells, are 
shown in this fig- 
ure? 



STUDIES IN CRYPTOGAMS 



185 




plant often forms the greater part of the floating green mass (or 

" frog spittle ") on ponds. The threadlike character of the thallus 

can be seen with the naked eye or with a hand 

lens, but to study it carefully a microscope 

magnifying two hundred diameters or more 

must be used. The thread is divided into long 

cells by cross walls which, according to the 

species, are either straight or curiously folded 

(Fig. 266). The chlorophyll is arranged in 

beautiful spiral bands near the wall of each cell. 

From the character of these bands the plant 

takes its name. Each cell is provided with a 

nucleus and other protoplasm. The nucleus is 

suspended near the centre of the cell («, Fig. 

265) by delicate strands of protoplasm radiat- 
ing toward the wall and terminating at certain 

points in the chlorophyll band. The remainder 

of the protoplasm forms a thin layer lining the 

wall. The interior of the cell is filled with 

cell-sap. The protoplasm and nucleus cannot 

be easily seen, but if the plant is stained with 

a dilute alcoholic solution of eosine they become 

clear. 

Spirogyra is propagated vegetatively by the 

breaking off of parts of the threads, which con- 
tinue to grow as new plants. Resting-spores, 

which may remain dormant for a time, are formed by a process 
known as conjugation. Two threads lying side 
by side send out short projections, usually from 
all the cells of a long series (Fig. 266). The 
projections or processes from opposite cells 
grow toward each other, meet, and fuse, form- 
ing a connecting tube between the cells. The 
protoplasm, nucleus, and chlorophyll band of 
one cell now pass through this tube, and unite 
with the contents of the other cell. The en- 
tire mass then becomes surrounded by a thick 
cellulose wall, thus completing the resting- 
sporCy or iy go spore (z, Fig. 266). 



Fig. 266. —Con- 
jugation OF 
Spirogyra. 
Ripe zygospores 
on the left; a, 
connecting 
tubes. 



Fig, 267. — Strand, 
OR Filament of 
Zygnema, freed 
from its gelatinous 
covering. 



Zygnema is an alga closely related to spiro- 
gyra and found in similar places. Its life 
history is practically the same, but it differs 
from spirogyra in having two star-shaped 
chlorophyll bodies (Fig. 267) in each cell, in- 
stead of a chlorophyll-bearing spiral band.