First Studies of Plant Life

(i^acneU Hntuetaity Hibcati} 3ti(aca,

Kern ^atk

GEORGE FRANCIS ATKINSON BOTANICAL LIBRARY 1920

CORNELL UNIVERSITY LIBRARY

924 089 570 380

The tine

original of

tiiis

book

is in

Cornell University Library.

There are no known copyright

restrictions in

the United States on the use of the

text.

http://www.archive.org/details/cu31924089570380

FKONTrspiECE.

—A

Congenial Plant Society, Minnesota

(Photograph, by H. E. Murdock)

FIRST STUDIES OF

PLANT LIFE BY

GEORGE FRANCIS ATKINSON,

Ph.B.

PBOFESSOK OF BOTANY IN CORNELL UNIVERSITY

BOSTON,

U.S.A.

GINN & COMPANY, PUBLISHEES 1902

OOPYKIGHT,

GEORGE

1901,

PEAlirCIS

BV

ATKINSON

ALL RIGHTS RESERVED

(Ct3

^1 is-0

INTRODUCTION For

a long time botanical science, in the popular mind,

consisted

chiefly of pulling flowers to pieces

their Latin

names by the use

and finding

of the analytical key.

All

the careful descriptions of the habits of plants in the classic

books were viewed solely as conducive to accuracy in placing the proper label upon herbarium specimens.

Long

after the

study of botany in the universities had become biological rather than purely systematic, the old regime held

still

;

that pierced primeval darkness. cally passed away,

cesses

and

and

its

in

and perhaps, some of us to-day know working in the twilight of that first ray

our secondary schools of high schools

sway

and to-day

life

However, this has practiand its problems, its suc-

failures, absorb the attention of the botanist

The knowledge

zoologist.

of the

name

of the plant or

simply a convenience for discrimination and

animal

is

ence.

The systematic

refer-

relations of a plant or animal are used

showing present anatomical afiinities and past development. The absorbing themes of investigation and study are the life processes and the means by which the organisms living in the world to-day have climbed upward and placed in

themselves in the great realm of the "

When

the idea of nature study

tional world,

on which

it

it

first

fit."

dawned

in the educa-

was inevitably confused with the sciences

was based.

Hence

in earlier times

teach the nature study of plants by

we

tried to

making the children pull

;

INTEODUCTION

iv

names

the flowers to pieces and learn the

This was as bad nature study as

parts.

for

we were

of their different

it

was bad

science,

The

violating the laws of the child's nature.

child cares very little about the forms of things

;

he

far

is

more interested in what things do. To-day nature study and science, while they may deal with the same objects, view them from opposite standNature study

points.

natural

environment.

learns to

own

know

the

life

not synthetic;

is

central thought the child,

and for

The

child,

its field

it

takes for

work

its

,the child's

through nature study,

history of the violet growing in his

dooryard, and the fascinating story of the robin nesting

in the coinice of his

own

porch.

The

differences of this

and this robin from other violets and othet robins in the world he considers not at all. That the plant as well as the animal in nature study should be regarded a thing of life has long been recognized, and most of our nature study of plants begins with the planting and sprouting of the seed. Unfortunately, it mostly stops here the life processes of the plant have seemed too complex to be brought within the comprehension of the child. There is violet

much

of chemistry in operations of plant growth,

and we

find

very few things in chemistry that are simple enough to be properly a part of nature study. " First Studies of sole

view

Plant Life " has been written with the

of bringing the life processes of the plant within the

reach of the child and, with the aid of the competent teacher, it

will certainly be comprehensible to the pupil of

lower grades.

even the

In this book the plant stands before the child

as a living being

with needs like his own.

plant must be born,

must be nourished, must

To

live,

breathe,

the

must

INTRODUCTION

V

reproduce, and, after experiencing these things, must die.

Each plant that is grown room should reveal to the whole life. He fed; it must grow; of a

place

;

it is

it

ditions

and the story young plant must be no longer a matter of commonchild the secrets

it

is

;

How

It is of little

lanceolate or palmate

When

of a school-

replete with interest, because it is the struggle

grow?

for the plant

window box

realizes that the

of an individual to hve.

does

in the

;

it is

it

get

its

food ? its

How

leaves are

a question of what the leaves do

a matter of

it is

does

moment whether life

or death.

the child has once become acquainted with the con-

and

necessities of plant

world seem to him

life,

how

different will the

Every glance at forfest or field will tell him a new story. Every square foot of sod will be revealed to him as a battlefield in which he himself may count the victories in the struggle for existence, and he will walk henceforward in a world of miracle and of beauty, the miracle of adjustment to circumstances, and the beauty of !

—

obedience to law. BuKEATj OP Nature Study,

CoKNELL University.

ANNA BOTSFORD COMSTOCK.

AUTHOR'S PREFACE In presenting these "First Studies of Plant Life" the and pupil in the life and

object has been to interest the child

work

The chUd,

of plants.

ested in

life

or

young pupil, and active,

or something real

play, or play-work.

Things which are

is

primarily inter-

full of action, of

in action,

which rep-

resent states of action, or which can be used by the child in

imitating or

"staging" various

activities or

those which appeal most directly to forceful in impressing on his

mind

realities,

him and which

are

are

most

the fundamental things

on which his sympathies or interests can be built up. There is, perhaps, a too general feeling that young pupils should be taught things a thing

is so,

or

why

it

;

that the time for reasoning out

behaves as

it

ditions, belongs to a later period of life.

forget that during the

first

why

does under certain con-

We

are apt to

years of his existence the child

dependent largely on his own resources, his own actitity body and mind, in acquiring knowledge. He is preeminently an investigator, occupied with marvelous observations is

of

and explorations

Why

of his environment.

then should we not encourage a continuance of this

kind of knowledge-seeking on the part of the child ?

young pupil cannot, in

working out the relation and meaning

opportunities often present themselves

be encouraged to

The

of course, be left entirely to himself

make

when

of things.

But

the child should

the observations and from these learn

AUTHOE'S PEEFACE

viii

why

the result

No more

is so.

those which deal with the

life,

excellent opportunities are

The

afforded than in nature study.

topics

most suitable are and

or work, or the conditions

states of formation.

To

the child or

young pupil

a story, or the materials from

which a story can be constructed,

is

not only the most engag-

ing theme, but offers the best opportunity for constructive

thought and proper interpretation. In the studies on the work of plants some of the topics will have to be presented entirely by the teacher, and will serve as reference matter for the pupil, as will all of the book on

The chapter dealing with the chemical changes work of starch-making is recognized by the author as dealing with too technical a subject for young pupils, and is included chiefly to round out the part on the work of plants. Still it involves no difficult reasoning, and if young children can appreciate, as many of them do, the "Fairyland occasions.

in the

of Chemistry," the pupils eral notion of

what

is

may

be able to get at least a gen-

involved in the changes outlined in

this chapter.

The

chapters on Life Stories of Plants the author has

attempted to present in the form of biographies.

They

sug-

gest that biographies are to be read from the plants themselves

by the pupils. In fact, this feature of reading the stories which plants have to tell forms the leading theme which runs through the book. The plants talk by a "sign language," which the pupil is encouraged to read and interpret. This method lends itself in a happy manner as an appeal to the child's power of interpretation of the things which it sees. Many older persons will, perhaps, be interested in some of these stories, especially in the Struggles of a White Pine.

AUTHOK'S PREFACE The

ix

story on the companionship of plants also affords a

topic of real interest to the pupil, suggesting social conditions

and relations of plants which can be read and

inter-

preted by the young.

Nearly

all

of the line drawings are original,

and were made

expressly for this book by Mr. Frank R. Rathbun, Auburn,

N.Y.

260 were reproduced from Bergen's "Botany," and Fig. 84, from Circular 86, United The States Department of Agriculture, by Mr. Chesnut. author desires to acknowledge his indebtedness to the following persons, who have kindly contributed photographs Mr. Figs. 64, 79, 215, 216,

:

H. E. Murdock, for the Frontispiece

Prof.

;

Conway Mac-

Millan, University of Minnesota, for Figs. 220, 249, 257

;

Professor Gifford, Cornell University, for Figs. 87, 183, 285, 290, 293, 295

Mr. Gifford Pinchot, Division of Forestry, Department of Agriculture, for Figs. 280, 282, United States 289, 292; Prof. W. W. Rowlee, Cornell University, for Miss A. V. Luther, for Figs. 200, 296, Figs. 279, 281, 304 302; Prof. P. H. Mell, for Fig. 278; Prof. William Trelease, ;

;

Missouri Botanical Garden, for Fig. 307

Yale University, for Fig. 306.

photographs by Mr. K. Miyake

by Mr. H. Hasselbring Dr.

W.

A. Murrill.

by the author. Some

;

Fig. 221 ;

;

Professor Tuomey, is

reproduced from

Fig. 77, from photograph

Figs. 76, 288,

from photographs by

The remaining photographs were made of the text-figures

were reproduced from

the author's " Elementarj' Botany," while the photographs of

mushrooms

are

from some of those published in Bulletins

138 and 168 of the Cornell University Agricultural Experiment Station, and from the author's " Mushrooms, Edible, Poisonous, etc. CoENELL University, March,

qj,q 1901.

^ ATKINSON.

CONTENTS PART

I;

THE GROWTH AND PARTS OF PLANTS

CHAPTER I.

II.

III.

IV.

V. VI.

VII.

VIII.

IX.

X.

PAGE

How How

Seedlings come up from the Ground

THE Seeds behave when germinating The Parts of the Seed Growth of the Root and Stem Direction of Growth of Root and Stem Buds and Winter Shoots The Full-Grown Plant and its Parts .

XII.

XIII.

XIV.

XV. XVI. XVII.

XVIII.

1

7

18

24 27 33

:

The Plant I. The Full-Grown Plant The Full-Grown Plant The Full-Grown Plant: :

:

PART XI.

.

How

THE

II:

40

The Stem III. The Root

II.

IV. Leaves

.

.

45

.

54

.

60

THE WORK OF PLANTS

Living

Plant

uses

Water

to

REMAIN Firm THE Root lifts Water in the Plant Plants give off Water The Water Path in Plants The Living Plant forms Starch The Work done by Plants in making Starch The Kind of Gas which Plants give off while making Starch How Plants breathe

How How

....

xi

74 87 94

105

109 115 121

126

CONTENTS

xu PART

III:

THE BEHAVIOR OF PLANTS PAQB

CHAPTER

XIX.

XX. XXI. XXII. XXIII.

XXIV.

The The The The

Sensitive Plant

XXVIII.

XXIX.

.

.

.

.

....

PART

XXV. XXVI. XXVII.

132

Behavior of Plants toward Light Behavior of Climbing Plants Behavior of Flowers How Fruits are formed How Plants scatter their Seed

IV:

136

150

166 168 176

LIFE STORIES OF PLANTS

Life Story of the Sweet Pea Life Story of the

185

Oak

194

Life Story of Ferns Life Story of the Moss

204 .

.

....

Life Story of Mushbooms

212 215

PART V: BATTLES OF PLANTS IN THE WORLD

XXX. XXXI. XXXII. XXXllI.

INDEX

The Struggles of a White Pine Struggles against

Wind

....

222 238

Struggles for Territory

244

Plant Societies

249 263

FIRST STUDIES OF PLANT LIFE Part

I

THE GROWTH AND PARTS OF PLANTS CHAPTER HOW The

SEEDLINGS COME UP FROM THE GROUND

life in

seeds of

I

a dry seed.

For

this study

we

shall use

beans, peas, corn, pumpkin, sunflower, and

You may

buckwheat.

use some other seeds

if

they

more convenient, but these are easy to get at feed If you did not know that they stores or seed stores. were seeds of plants, you would not believe tha,t these dry and hard objects had any life in them. They show no signs of life while they are kept for weeks or are

months in the packet But plant the seeds field

during the

or pot of

damp

days there

is

warm

soil

or bag in a dry room. in

damp

soil in

season, or plant

kept in a

the garden or

them

warm room.

no sign that any change

is

in a

box

For several taking place

THE GROWTH AND PARTS OF PLANTS in the seeds.

not too cold,

But in a few days or a week, if it is some of the surface earth above the buried seeds

surface

ing in the

young green life

disturbed, lifted, or

Rising through this open-

cracked.

has

is

We

plant.

now, because

the power to push

it

is

a

see that

it

there

soil

grows and has

its

way through

The dry seed was alive, but The plant life was could not grow. dormant in the dry seed. What made the plant life active when the seed the

soil.

was buried

How

Fig. 1. Bean seedlinge breaking through the

the ground.

soil.

in the soil

?

the corn seedling gets out of

One should watch

for

the earliest appearance of the seedlings

coming through the soil. The corn seedling seems to come up with little difficulty. It

comes up

object

straight, as a slender, pointed

which

pierces

through the

easily, unless the earth is

a clod or stone

lies

soil

very hard, or

above the seedling.

It looks like a

tender stem, but in a few

days more

unrolls, or

it

unwinds, and

long, slender leaves appear, so that

we took leaves

what

Fig.

2.

lings

Corn seedcoming up.

for a stem was not a stem at all, but delicate wrapped round each other so tightly as to push

HOW their

SEEDLINGS COME UP

way through the

soil

happened to the leaves

3

unharmed. What would have they had unfolded in the

if

ground ?

How the bean behaves in coming out of the ground. When we look for the bean seedling as it is coming up we

see that the

loop.

This loop forces

stem

is

its

bent into a

way through

the soU, dragging on one end the bean

Sometimes the outer ^Tiu^ZL'ZlI- that was buried. ''"^coat of the seed clings to the bean as it

comes from the ground, but usually

is

left in

it

As the bean

ground the outer coat see that the

is

and is

the bean

being raised above

into

split

two thick parts

[cot-y-le'dons),

which

spread farther

and

apart,

farther

lifts

Now

slips off.

bean

and

after the loop appears

straightens out

several inches high.

we

Soon

the ground.

above ground

this slips ofE

showing between them young green leaves,

which soon expand into well-

formed bean

leaves.

The pea seedling comes up la a The stem of the pea different way. also

comes up

straightens

m

.

a loop.

up we look

As

.

Germinating bean 4. shedding the seed coats.

fig.

it

in vain for the pea

on the end.

There are small green leaves, but no thick part of the pea which was buried in the ground.

This part of the

THE GEOWTH AND PAETS OF PLANTS pea, then,

must have been

we have

seen

how

left in

When

the ground.

come up, we

the other seedlings

can plant more seeds in such a

way

as to see just

how each

seed

germinates, and learn the reason for the different behavior of the

seedlings in

coming from

the ground.

The pumpkin seedling comes up in a loop,

also

and on one end loop, as

of

the

it is

being lifted

through the

we

soil,

see

two ratner

par

tnick

I

tj

s

.

Bean seedUngs straightening up the plumule and 5. spreading leaves showing from between the cotyledons.

fig.

m 0"

;

JL

gether they are about the

By

looking carefully shell, or

size of

the

we may sometimes

seed coat,

still

way down

over the Fig.

6.

lings

Pea seed-

empty

tips.

only,

seed.

find the old

clinging to the tips

of these parts of the seed

part

pumpkin

;

the shell

is split

and so pinches tightly

Usually, however,

it is left

in the ground.

coming up.

It

this little

will be interesting later to see

pumpkin plant

gets

out of

its

shell.

how It

HOW

SEEDLINGS COME UP

usually escapes while

As the loop

still

buried in the

straightens out, these

soil.

two thick

portions spread wide apart in the light and

become green. There are little

lines

on them resembling the

'

veins "on some

leaves.

Are these

two parts

pumpkin

of

J Fig.

7.

the

seed real leaves

where they

Pumpkin seedlings coming from the ground, showing loop and opening cotyledons. ?

join the stem.

Look down between them Very young leaves are

growing out from between them.

^^Sl-

The sunflower

..

seedling.

The sun-

flower seedling comes up with a loop, Fig. 8. Loop on stem of sunflower as it comes from the ground.

dragging the seed

The

on one end.

shell, or seed coat, is

sometimes

in the ground, because

it splits

through when the root wedges out.

But often the seed

left

farther its

way

coat

clings to the tips of the cotyle-

dons until the plant straight-

Then the cotyledons usually spread far apart. The ens.

seed coat of the

pumpkin Fig.

sometimes clings to the

tips

Seedlings of sunflower casting 9. seed coats as cotyledons open.

of the cotyledons until the sunlight pries

them

apart.

THE GROWTH AND FARTS OF PLANTS The buckwheat loop, is

This also comes up with a

seedling.

and we begin to see that

very

common among

this

seedlings.

seed coat of the buckwheat

is

way

of

coming up

The

often lifted

above ground on one end of the loop.

Through the

It is split nearly across. split

in the seed

^ ~ ..sj^juLoop of buckwheat seedlings coming

Pig.

10.

through the surface of the soil.

the lie.

we can

see that

are leaves

there

pac]jed inside very

differently from the

way

in

which

the cotyledons of

pumpkin and sunflower The buckwheat cotyle-

dons are twisted

or

round each other.

-r4ms^

rolled

As

the

Fig. H.

cotyledons of buckwheat seedand casting seed coats.

lings untwisting

seedling straightens

up they

untwist, and in doing this help to throw off the coat.

CHAPTER

II

HOW THE SEEDS BEHAVE WHEN GERMINATING To prepare the seeds see

how

for observation.

We

could not

the seeds planted in the ground behaved while

they were germinating, for they were

To watch the

hidden from sight. behavior of the

diflferent kinds, is

warmth

glass, or

they are

seeds are put where there

and moisture under

damp paper

covered with

which may be

lifted at

what is going on. grown in tumblers, or

or moss,

any time

to

They may be

see

sels

the

in shallow ves-

covered with glass, with wet moss

or paper inside.

The

best

way

to

them for easy observation is to put them in a lamp chimney filled plant

with wet peat moss or sawdust, as

shown in Fig. 12. Or a box may be made with glass doors on the side. This

may

be

filled

Corn seedlings growing in lamp chimney.

with wet moss or sawdust, the seeds

put in place, and the door then closed.

some

soft

manila paper

may

If

desired,

be placed on the moss or

THE GEOWTH AND PAETS OF PLANTS

8

sawdust, and the seed placed between this

and the

ney

is

If the

glass.

lamp chim-

used, roll the paper into a tube

smaller than the chimney and slip

Now

in.

not very

it

put the peat moss inside,

The

tight.

seeds

started between the glass

may

be

and paper,

and with a blunt wire may be pushed into

any position

The seeds swell.

desired.

first

absorb water and

Before the seeds are planted

for this study they should be soaked

from twelve to twenty-four hours

in

Then they may be placed in germiuator f Or obscrvation. Look

water. ria.13.

the

Pumpkin seedlings

growing

in

lamp chimney.

,

.

i

l

at the seeds

m the water several times *

j.1

i

j.

j_

•

during the day, and see what changes take place in them. All of

them become

ger.

After they have

lar-

been in the water for a day, cut one, and also

cut one

try to

dry seeds.

of

The

the

seeds

that have been soaked in

water are softer and

larger than the dry seed. ,-,,.,

Why IS this so o .

,

1

.

i

T it

^^'^- 1*,

must

^°^ ^'*^ S^^s

^''°^

growing seedlings.

°" side for

HOW THE

SEEDS BEHAVE

be that they have taken in water, or have absorbed water, as

we

This has increased their

say.

them wet

inside,

and

size,

made

soft.

How the pea and bean seeds swell. The pea and bean swell in a curious way, as can be seen by looking at them at short intervals after they Fig.

i5~Bean

seed before

soaking in water.

The water is taken in at first more rapidly by the coat The coat of the seed than by the other parts.

have been placed in the water.

becomes much wrinkled then, as if

it

were too big for the

seed.

First the wrinkles begin to appear

Then they

round one edge.

be-

come more numerous, and extend farther over the surface, until the entire coat is strongly wrinkled,

as

shown

in Fig. 16.

Fig. 16. Bean seeds with coats wrinkling as they soak in water.

This loosens the coat from the

bulk of the seed, and perhaps

why

loop of the stem

is

17

after

Bean seed soaking in

water] larger, and

now

first

Xhcv

fill

up water,

so that out the coat again °

it is

smooth, as shown in Fig. 17.

now smooth.

The

Finally the

i^^lde parts swell as they take •'

one reason

puUing the inside of

the seed out of the ground. Fie

is

this coat slips off so easily while the

sign of the seedling.

In a very few days,

that the seeds are thoroughly soaked with water,

the signs of

life

begin to appear.

The

root grows out

THE GROWTH AND PARTS OF PLANTS

10

of the seed as a small, white, slender, pointed object.

It

comes from

the same spot in every seed of one

In the sunflower, pumpkin,

kind. Fig. 18. Corn seeds germinating under glass, the left-

hand seed upside down.

,

^

Duckwheat, and ti

,-i

it

out ter

it

Later stage

j*

comes irom

tji

i

j_i

in the

As soon

which way the seed happens the seeds are

lamp chimney, or side,

position desired.

as the root

in a

to

placed

It will

be interesting to watch seeds

When

the roots have

more

or

in length,

sketch some of the different positions. Is

there

any

ad-

vantage to the plant in having this first root

downward?

the

they can be easily held in any

placed in different

grown an inch

in

lie.

box with a glass

that have been positions.

comes

grows directly downward, no mat-

When of Fig. 18.

_p

.,

it

comes out from the hollowed, or

concave, side.

19.

i

com

the smaller end oi the seed,

bean

Fig.

t

,

-i

grow Fi(j.20,

Stmiater stage of

Fig. 18.

HOW THE How the pumpkin

SEEDS BEHAVE

plant gets out of the seed coat.

the root grows out of the small end of the seed, like a

wedge and often

Fig.

21.

splits

it

little

it

As acts

the shell or seed coat part

Still later stage of Fig. 18.

way, but not enough for the

The

11

Note root

liairs in all.

rest of the plant to escape.

plant develops a curious contrivance to assist

in getting out.

There

is

formed on one side of the

THE GROWTH AND PAETS OF PLANTS

12

Fig.

22.

Pumpkin

seedlings casting the seed coats (note

stem a " peg " or " heel." side of the stem,

when

This

is

the seed

tlie

" peg

")•

formed on the under-

is

lying on

its side,

at

the point in the opening of

the seed.

This peg presses

against the end and helps to split Fig.

Bean

23.

open.

seeds ger-

the

seed

coat

further

The stem now

elon-

minating under glass.

gates above this peg, presses

against the other half of the seed

coat,

halves

far

and apart

pries

the

two

so

that

the

plant readily slips out, as

shown

in Fig. 22.

Germination of the bean.

After

the root comes out of the bean

on the concave side, the FIG.

25. sunflower seed germinating,

24.

Peas germinating under glass.

^^^^ ^"^^^^ ®° ^^^^ ^^^^ O^^^^r COat cracked and begins to slip off. We can

^^ ^^^ is

two halves

Fig.

HOW THE

SEEDS BEHAVE

13

then see

stem

is

that

the

a continua-

tion above

from the

root, joined to

one

end of the two thick parts or cotyledons.

This part of the stem

now grows

Fig.

26.

Beans with one cotyledon removed to see are raised up from the ground.

how tlie cotyledons

arches up in a loop,

and

the bean

lifts

upward.

The

The

pea.

pea germinates in a

way.

different

After the root begins to

grow the

pea swells, so that the thin coat the bean,

is

is

Fig.

27.

to see

Peas with one cotyledon remoyed

how

the cotyledons are left in the

^°""'^-

cracked.

The stem,

just as in

joined at one side to the two thick

cotyledons of the pea.

But

this part of the

rapidly,

THE GROWTH AND PAETS OF PLANTS

14

stem of the pea does not grow longer, so the pea is left The stem grows on from in position in the. ground.

between the two thick cotyledons, arches up in a loop, pulls out the

young Fig.

28.

White oak acorns germinating.

and tender leaves from the ground, and then straightens up. To compare the germination of the bean with This can be done very easily by

that of the pea.

iirst

soaking beans and peas for twenty-four hours in water.

With the

finger or with the knife split

the bean along the line of the convex side pm.29. Pumpkin

seeds

germinating under glass, turned in differen't positions.

and pull the halves apart.

youug embryo plant Pii 11 ouc 01

thesc

halves,

lies

^^^^ f^.^^ ^^^ ^^^^^ way and place the

beans in the same

The

attached to

having

11 broken

g^j.^

8QVeV&\

1

•

half

which has

the embryo bean plant under glass, in position as

shown

in Fig. 26.

Take one

of the peas and,

by a

slight

rubbing pressure between the fingers,

remove the thin outer between the halves

is

coat.

now

The

seen.

split

CareFig. 30.

fully

and

break away one of these halves

as Pig. 29,

more peas in the same way those which have the embryo attached should be planted

split several

pieces

Same

but later stage.

;

HOW THE

SEEDS BEHAVE

15

under glass near the beans, in position as shown in Fig. 27.

From day

That part

to

of the

day observe the growth in each

case.

bean stem below the cotyledon can be

seen to elongate, while in the pea

the stem above

it is

the attachment of the coty-

ledon which grows.

The oak seedling. The young oak plant comes out of the acorn in a curious

way.

It is easy to get the acorns

to

see

how they

Visit a white

behave.

oak tree

in late

October several weeks after the acorns have been falling

from the

tree.

If the tree is

by the roadside, or a field where there is some

^"'- ''

situated in

and shaded, many Or you may in the soil.

^^'^''

^'^«

°' ^'^-

which

loose earth

is

^

damp

of the acorns will be partially buried

bury them in a

cool,

collect the acorns

damp

soil,

and half

which should be

watered from time to time.

The root

is

the

first

to appear,

and

it

comes out

of

the small end of the acorn, splitting the short point on

The root the end of the seed in a star-shaped fashion. acorn is if the that immediately turns downward, so not buried the root will soon reach the be seen in Fig. 28.

soil.

This can

"

THE GROWTH AND PAETS OF PLANTS

16

How

the oak seedling escapes from the acorn.

look for sprouted acorns, you will find

Some with the

stages of growth.

found,

be

will

them

If

you

in different

root just emerging

and

others with the "tail

an inch or more long. In these larger ones

we can

see that the

part next the acorn

As

it

two

into

split

is

parts.

curves, this split

often widens, so that

we can see in between. In such cases a tiny

bud may be seen lying close

the fork of

in

the two parts.

bud

is

This

growing

the

end of the stem, and

we now

see that the

tiny plant backed out of the acorn.

The

root hairs.

In

this study of the seedlings

^'"^

''•

^""

'^''' ''"^^ "' ^'^-

grown under a glass, or is no soil for the root

a box or vessel where there

bury

itself,

covered, a

you

little

""

will see that the root soon

in to

becomes

distance back of the tip, with a dense

HOW THE

SEEDS BEHAVE

white woolly or fuzzy growth.

You

17

will see that these

are like very tiny hairs, and that the root bristles all

around with them. help the root to do study.

They its

are the root hairs.

work, as

we

They

shall see in a later

CHAPTER

III

THE PARTS OF THE SEED Are the parts of the seedling present in the seed? Since the root comes from the seed so soon after planting,

when

the

soil is

moist and the weather warm, and

the other parts quickly follow, one begins to suspect that these parts are already formed in the dry seed.

We

are curious to

know

examine the seeds and

if

this is so.

We

The dry

see.

examined, but they are easier to open

are eager to

seeds might be^ if

they are

soaked in water from twelve to twenty- four hours. they are ready,

The parts split, as

let

of the

first

When

us open them and read their story.

The bean seed can be by cutting

bean seed.

described on page 14, into halves

through the thin coat along the ridge on the rounded or convex side. flat

Spread the two parts out

and study them.

fleshy objects

The two

large white

which are now exposed we

recognize as the two cotyledons which were fk;.

33.

showing

Bean scar.

lifted

pQat

from the

wMch

soil

by the

eucloscd

them

The

thin

the seed

coat.

loop. is

Lying along the edge near the end of one of the cotyledons

is

a small object which looks like a tiny plant. 18

THE PARTS OF THE SEED this the

Is

end

embryo

the root, and

is

that

bean plant

of the

?

19

The pointed

we see that it hes in such a position when it begins to grow it will come

through the seed coat near the scar on the bean.

FiG.

34.

split

Bean seed

open to shoAv

plantlet.

At the other end of the plantlet are two tiny leaves, pointed, and set someWe know that thing like the letter V. xi

there are veins they are leaves i,because xl, i

on them like the veins on the

is

short and stout, and there

dividing line between

mid stem in cle.

the

it

and

embryo are

The upper end

is

Between these

leaf.

leaves and the pointed end or root

lies

the stem.

It

no distinct

the root.

Root

called the cau-li-

of the

stem just below

no-

33.

cioss

section of bean

the tiny leaves

joined to the cotyledon,

is

-

showing situation of plantlet,

.

one cotyledon breaking away as the bean

was

split open.

ledons, that

is,

The part of the

the

stem

beloio the coty-

part between them and

the root, is

called the hy'po-cot-yl.

The parts

of the pea seed.

The

position of

the plantlet can be seen on one side of the

rounded pea, below the Fig.

3G.

been soaked in water.

scar, after the

By

pea has

a slight rubbing

pj.ggg^j,g betwecu the thumb and finger the The two thick seed coat can be slipped off.

Pumpkin seed.

thin

cotyledons

can

now

be

separated.

If this

is

done

"

THE GEOWTH AND PAETS OF PLANTS

20

embryo plant remains attached to one of Sketch this, as well as the embryo of the bean

carefully, the

them.

;

compare them and indicate in the drawings the

names

The parts

of the parts.

on the pumpkin seed

scar

is

found on

coat can be

;

split

right-hand half the papery covering

shown which

is

cutting

sur-

and then prying

we

see, in

shown by a "

to the point

is

The " meat papery layer. The

the caulicle (root and stem).

the small pointed end

The meat

of the seed coat. as

way

open.

it

covered with a very thin

pointed end of the meat It lies, as

part

carefully

around the edge of the flattened seed

rounds the " meat."

inside

by

The

seed.

The seed

the smaller end.

Pumpkin Fia. 37. seed split open in

pumpkin

of the

split "

is

in halves,

which runs through

where they seem to be

joined.

These halves of the meat are the cotyledons

Fig. 38. " Meat," the embryo, with one cotyledon

turned to

Pry them apart

of the joumpMn.

one

is

broken

free.

so that

At

one

side.

this junction of the

cotyledons will be found a tiny bud on the

end

of

the

stem

attached

ledon after the other Fig. 39.

Long

section through

a pumpkin seed.

So

it

stcm

We lies

is

is

to

broken

one cotyoff.

The

vcry short in the pumpkin plantlet.

have found

in the pea and bean that it between the cotyledon and the root.

does in the pumpkin.

Is it so in all seeds? -

Cut a pumpkin seed through the cotyledons, but

THE PARTS OF THE SEED

21

a sketch of

M

one part showing the seed coat, the position

iifl

lengthwise of the seed.

of the

papery

Make

lining, the cotyledons as well as

the short root and stem.

Cut a seed in two, n crosswise, and sketch, showing all the parts. .

The sunflower

T

section of

pumpkin

The sunflower seed can be

seed.

seed.

split

remove the seed coat in the same way as the pumpkin seed. The meat occupies much the same open to

position,

and

While

covered with a papery layer.

is

the proportions are different, the general

shape of the plantlet reminds one of that

pumpkin or squash. The root and ^tcm are more prominent. There are two ^^^ cotyledous. As wc spread them apart ^

of the FIG. 41.

Sunflower

seed split open showing

"meat,"

the embryo in right and papery covering in left half of

*^

^g

*•

ggg i^gji they are loinsd to the ''

the stcm J

We cau

the tiny bud. as

we

did the

pumpkin

relation of the parts

is

seed,

much

Structure of the corn seed.

the corn

we have

If

end of

•>

also see

we we

between them

cut the seed in two, shall see that the

the same.

In the germination of

seen that the root comes out at the

small end of the kernel in the groove on one side, while the leaves first appear on the same side at the other end of this groove. If the tiny plant is present in the seed,^ then

it

should be found in the ,

groove.

Split the soft kernel lengthwise

^^^

^ ^^^^^

of sunflower with

one cotyledon moved.

re-

THE GROWTH AND PARTS OF PLANTS

:>2

through

Just underneath the seed coat at

this groove.

the small end will be seen the end of the root and stem

SO

Near the other end

(caulicle).

may

groove there

Hon

These

of sunfloiver

seed at left

;

embryo

running as shown in Fig. O 44. represent

lines

several

leaves

cut

leugthwlse while they are rolled round t i The stem lies between the each othcr.

taken

seed.

leaves

be seen several converg-

at

right, side view of

from

lines

ina;

Cross sec-

Fifj. 43.

the

of

and root;

it

is

now very short, and cannot be On the opposite side of

distinguished from the root.

the stem from the groove

a small curved object. is the

m

•

7

.77

,

is

the

f

V^^j.

Section of corn seed ; at upper is the plantlet, next the cotyledon, at left the endosperm.

Fig.

only one cotyledon 7

corn seed,

7 -7

The meat

44,

right of each

•

while in

the other seeds studied

kin,

^\I3^

4

This

cotyledon cut through. .

^jjf

I here

______

is

there are two.

In the pea, bean, pump-

in the corn seed.

and sunflower seeds the cotyledons form nearly the meat inside the seed coats. the

""of^Tu'ct embryo,

except

endosperm.

part of

the

the

papery

lining,

is

the

for the cotyledons, being the first

l^^^^^' ^^^ rho:i:gon:;i:w embryo Burrounded by the

fact,

whole seed inside the seed coat in these

plants,

of

In

all

P^^

of the tiny

embryo

plant.

"^e have fouud Something ^ very different in the com. Thc embryo is only a small '^

of the seed. After the seed has germinated, the food substance is still there. Did you inside

THE PARTS OF THE SEED

23

ever examine a kernel of corn after the seedling liad

been growing some time?

There

is

scarcely anything

but the old and darkened seed coat.

left

hollow within.

It is nearly

The meat which formed most

of the inside of the kernel has disappeared.

What has become of it ? I who has examined the corn

think every one in this

way can

It has ^gone to 'form, food "^for the J vouna V plant. The substance which is used by the

tell.

com

embryo for food Is

is called

endosperm

there

endosperm.

in

p.^

another view

tucicwheatin

the seeds of the

pumpkin, the bean, the pea, and the sunflower? is

perhaps a hard question for you to answer.

difficult

tions, ^sectfon of'^buokwheat seed showcoiled

coty-

ledons.

the

If

But

It is a

ask a few more quesguess,

does the germinating pumpkin, sun-

seedling flgwer,p bcau,y or pea £r o find its food it

can get a

sufficient

from the cotyledons, or

did they obtain the food to

What

I will

and then perhaps you can

Where before

soil ?

That

matter to explain without taking a good deal of time.

mg

43.

Another section showing

become

amount from

first leaves,

where

so big in the seed

?

about the papery lining in the squash and sun-

flower seed

?

CHAPTER IV GROWTH OF THE ROOT AND STEM The part

of

One

the root which lengthens.

interesting things about the root

is

We

in length.

way it grows know that as the the

root becomes longer the tip

But does

along.

the

of

moves

take place by

this

a constant lengthening of the ex-

treme tip

tip of the root

Or

is

the

pushed along through the

soil

?

by the growth or stretching of some other part of

answer lings

this

if

the root

which are growing

We

?

we examine

in germina-

the lamp chimney, where

tors, as in

the roots are not covered with

To

where the

tell

Take a

fine

or water-proof ink.

Pumpkin seedlings, the root marked "in ]eft. Eight one showing where growth took place in twenty-four hours.

side

Beginning at

mark

off

on one

Very short spaces, as close

gether as possible, the •

soil.

root elongates.

pen and some indelible

the tip of the root, pia.48,

can

the seed-

.

i

irom thc 24

;

•

tip,

i

,

i

first

1

i

aud the others

1

to-

mm. mm.

GROWTH OF THE ROOT AND STEM apart, as

shown

back in the germinator in

downward.

Now

in Fig. 48.

place the seedling

position, the root pointing

In twenty-four hours see the

spaces between the

25

marks are no longer

The

result.

equal,

showing

that stretching of the root takes place over a limited area. Figs.

48 and 49 show the result with corn and pumpkin

seedlings.

The

grown permarked

root has not

ceptibly at the tip, for the space

by the first line does not appear to be any greater than it was twenty-four hours Growth in length occurs in a region ago. The a short distance tack of the tip.

off

spaces between the tip,

especially those

marks back between the

of the third, Corn seed-

Pig. 49.

and sixth marks, are much fourth, This is the place, then, where wider. fifth,

the

root stretches or grows in length.

The stretching

is

lings

marked

to

show where growth takes place in the roots.

greatest in the middle of this region.

The

Direction of the roots of seedlings.

first

root

from the seedling grows downward, as we have seen. In the germinating seed, what advantage is there to

downward direction of the first root ? which grow out from this first or primary

the plant in this

The

roots

root are called lateral roots.

take?

What advantage

direction

which the

is

"What direction do they

there to the plant in the

lateral roots take

?

Look

root system, as a whole, of the seedling

at the

when

well

THE aROWTH AND PARTS OF PLANTS

26

What

developed.

are the advantages to the plant of

the distribution of the roots which you observe

Growth

the stem.

of

In a similar

?

way

the

re-

gion over which growth

extends in the stem be shown. the seedlings

may

As soon as come above

the ground, or as soon as a

new

portion of the

shoot begins to elongate

above the leaves, mark ofi

the stem with cross

The lines on the stem may be plaCcd

lines. Fig,

50.

Stems of bean marked to show where growth takes place in stem.

farther apart than those

on the

root.

A

may

rule

and then,

They may be put

be used to locate the marks on the stem,

after several days,

the side of the stem, the determined.

as indicated in Fig. 50.

if

the rule

amount

of

is

placed by

growth

will be

CHAPTER V GROWTH

DIRECTION OF

OF ROOT AND STEM

In our studies of the seedlings

we cannot

fail to

observe

that the^^rs^ root grows doivnward and the stem upward.

No matter which way it

the earth, or

it is

Fig. 51.

in the

earth, or

eairth,

To

see

how

it

It

grows toward

grows toward the

in a horizontal position.

So we say that the root grows

while the stem grows

away from the

It is interesting to notice

upward.

sistently the root

turned, as soon as the

ground

Corn seedling pinned

center of the earth.

toward the

is

turns downward.

root conies out if

the seed

and stem grow

how

per-

in these directions.

persistent they are in this, change the posi-

tions of the seedlings after they

Downward growth

of the root.

seedlings germinated

in

moss 27

have begun to grow.

Take any one

of the

or sawdust or behind

,

THE GROWTH AND PAETS OF PLANTS

28 glass.

Place

in a horizontal position.

it

This

be done behind a pane of glass in a box, or a pin be thrust through the kernel into a cork which

then placed as in Fig. 51, with a tle

may may

is

lit-

water in the bottom of the vessel

to keep the air moist.

In several hours, or on the following day, ob-

Fia.

root.

The greater part

position, but the

Same corn

seedling as

shown

of

remains in a horizontal

it

end of the root has turned straight

downward again. What part of the horizontal position?

part of the root

52.

in Fig. 51, twenty-four hours later.

serve the position of the

it is

root bends

We

when

should

now determine what

which bends when

ward do

turns from the

it

it

grows down-

in this fashion.

To

this the root of another

seedling should be

marked

and placed in a horizontal

With a fine pen and India ink, mark spaces

position.

as close together as possible,

„

„

.,, ij,, T, FiG. 53. Pumpkin seedling placed,,horizontally and marked to show where the root bends when turning downward. ,

.

about 1

apart, beginr o ^

nlug at the tip of the TOOt.

Mark shown

mm.

off

ten such spaces, as

and leave the root in a horizontal position for a day. Now observe where the curve has in Fig. 53,

GROWTH OF ROOT AND STEM taken place.

It

has not taken place at the

mark made near

the tip

is still

taken place back from the 4, or 5, first.

probably,

the region of

mark

3,

the marks were close together at

that

where growth

the

the

These marks on the bent region of the root are

now far apart. You remember see

if

tip, for

The curve has

there.

tip, in

29

grew

root

same region, of the tip.

when

the root was measured to

in length took place,

we found

that

in this

back

just

This

an

is

interesting observation,

and I think you can understand

why

the root

can bend easier in the

region

where

it

is

stretching than in the

region where

tion has ceased.

54. Bean seedling placed horizontally and marked to show where the root bends.

Fig.

elonga-

The region

the motor zone, because this

What

is

causes the root to turn

question that

your

of elongation

is

difficult,

satisfaction.

It

is

called

where the root moves.

downward ?

This

is

a

perhaps, to demonstrate to

can be shown, however, that

gravity influences the root to turn toward the earth. Gravity, you know,

is

the force which pulls an apple

or a stone toward the earth

when

either

is

let fall.

"We must bear in mind, however, that gravity does not

THE GROWTH AND PARTS OF PLANTS

30

pull the root

down

on the stone or apple.

we

same way in which

in the

it

acts

It only influences or stimulates, (If desirable

say, the root to turn.

the teacher can

explain or demonstrate for the

pupils, when the

that influ-

ence of gravity Pumpkin cut oft" to show

Fig. 55.

seedling ijlaced horizontally and root tip that without the I'oot tip the root will

not bend.

turn in

it

was

placed.

to

Bean seedling treated

be demonstrated by

fastening, in different

pumpkin

as the

disk which revolves slowly.

with reference to the earth the influence of gravity

in the direction

on a perpendicular wheel or

positions, several seedlings

56.

grow

may

This

the well-known experiment of

IOg.

neutralized,

the root does not

downward but continues

which

is

is

The is

seedling in Fig. 55.

position of the root

constantly altered, and

neutralized.)

GROWTH OF ROOT AND STEM If the tip is

removed, will the root turn

31

Now

?

place

some more seedlings with the roots in a horizontal position, or, if you choose, this experiment can be carried on along with the others. With sharp scissors, or a very sharp knife, cut

off

the extreme tip of the root.

In twenty-four hours afterwards observe the roots. They have elongated, hut they have not turned down-

They have continued

ward.

to

grow

in

the horizontal position in which they were

motor zone was not this? It must be that

placed, although the

cut away.

Why

is

the tip of the root

the part which

is

sen-

is

sitive to the influence or stimulus of gravity.

For this reason the

tip of the root is called

the perceptive zone.

The upward growth stem

is

of the stem.

If the

well developed in any of the seed-

lings placed in a horizontal position,

we

see

that the stem turns up while the root turns

Fig.

57.

sunflower seedlings turning upward.

The corn seedling shows this well in Fig. 52. It is more convenient in studying stems to take seedlings grown in pots. Squash, pumpkins, corn, down.

bean, sunflower,

the pot on plants.

shown

etc.,

its side.

are excellent for this study. Place

In twenty-four hours observe the

They have turned in Figs. 57

and

the part which turns

58. is

straight

upward

again, as

In the case of the stems

at a

much

greater distance

THE GROWTH AND PAETS OF PLANTS

32

from the end than in the

This

root.

is

because the

region of elongation or motor zone in the stem is farther

from

the tip than in the root.

may seem

re-

markable that gravity, which influences the root

to

Kow

gravity influences the stem.

grow downward, upward.

It

is

influences

also

nevertheless true.

and

It

the

stem to grow

The

lateral

roots

lateral stems are influenced differ-

What

ently.

are the advantages to ger-

minating seeds from this influence of gravity on root and stem?

Behavior of the roots toward moisture.

Test this by planting seeds in a long box,

keeping the

soil in

one end dry and in

the other end moist. The root grows P umpkin toward moist places in the soil. If the ^ seedlings tturning

Fig.

58.

upward.

soil is

grow away from

surface of the soil

cannot get

if

too wet, the roots of

many

plants

Sometimes they grow out on the where they can get air, which they

it.

the soil

is

too wet.

CHAPTER VI BUDS AND WINTER SHOOTS Do buds have life? When the leaves have fallen from the trees and shrubs in the fall the forest looks bare and dead, except for the pines, spruces, cedars, and other evergreens.

'

Fig.

The bare

tree or shrub in the

Winter condition of trees and shrubs,

59.

yard looks dead in winter.

But examine

The

it.

slender tips of the branches are fresh and green.

we

cut or break a twig,

It is moist.

It

it is

not dry like a dead

If

stick.

seems just as much alive as in the

summer, when the

trees are covered with green leaves. 33

!

THE GROWTH AND PARTS OF PLANTS and on the

But look

at the tip of the twigs,

sides, just

above where the leaves were

do the buds mean

How of

horse-chestnut

the

one

how On

Observe the bud.

they are

the

are

the next

another.

after

seated

this side is one,

on the opposite

And

Take a pin and

on the bud.

move them

?

side

They

in

and

another.

is

two

next

the shoot

overlapping

the

see

seated

?

are not very

easy to remove, and our hands are " stuck

up "

if

we handle them.

This sticky substance helps to hold the scales close together and keeps

out water.

When shoot of horse- moved, c estnut.

rp^gj^

woolly hairs.

the

brown

scales are re-

See the thin chaff-like ones

come

scalcs covered

These scales

are

green in

and

They

are alive even in the fall or winter

in shape are like miniature leaves

are they kept

from being

!

with long

color,

How

What

life ?

On

the buds look inside.

" scales "

How

Do they have

?

!

killed

?

!

The

long woolly hairs are folded round them like a scarf, and all are packed so tightly and

snugly under the close-fitting brown scales

re-

BUDS AND WINTEE SHOOTS

35

that they are well protect-

ed from loss of water during dry or cold weather,

They

or after freezing. lie

" asleep," as

all

winter.

it

were,

In spring

we

know they awake

How the bud looks when split.

we

With a sharp knife

will split the

bud down through

the end Fig.

62.

Opening bud of hickory.

closely all the scales

,

stem.

of the

-ttt

We see how i

Near the center they

fit.

become smaller and smaller,

iintil

there

is

the

end of the stem,

soft

which seems

much

alive

be as

to

as

in

the

summer, but it is resting now. The leaves in the Fig. 6 Long section

bud

winter leaves,

are

HoW

convenient

it

is

of horse-

the

tree

or

ciiestnutbud

for

woolly scale

that in the fall

leaves inside.

,

-,

.

put on this ,

it

armor

can /.

oi

and wax to protect the tender end of the stem

brown

scales

;

shrub

Pig.

64.

Bud

in section,

of European elm showing overlap-

ping of scales.

THE GROWTH AND PAETS OF PLANTS

36

The

buds.

lateral

There

several large buds on the

are

side of

the shoot, larger near the terminal bnd.

If

we examine

these,

we

find that they look the

same

inside

as the terminal bud.

The

lateral

buds are smaller, perhaps.

Where

are the buds seated on the shoot?

The

lateral

seated just scar left leaf.

We

buds

are

above the

by the

falling

say that they

are in the axils of the

began

leaves, for they to

form

here

in

the

summer, before the leaves

fell.

Are there

buds in the axils of

all

the leaves of the

shoot which Fig.

65.

Slioot

and buds of

you have

?

liorse-cliestnut.

Which buds will

form branches next spring

What

?

will the terminal

bud do

?

Why

is

the

terminal bud larger than the lateral buds

?

66. Branched shoot of horse-chestnut with three

Fig.

years' growth.

BUDS AXD WINTER SHOOTS The winter

37 shoot.

You

should have a shoot two or three feet long, branched,

See

possible.

if

marked.

how

The

leaf scars. These are very

and are in pairs opposite each other, large,

just as the

scales are

seated in the bud, only

the different pairs are farther

Who

apart on

the stem.

what the row of pin holes in the scar means ? Perhaps you can tell better can

tell

What

later on.

see PIG.

67.

Shoot of ash three

years old, and

section

showing annual

rings.

on the shoot

^^« s^aZg scars, OT

What

else

do you

Ihere are

?

girdU scars.

do they mean

?

•'

When

thB bud begins to grow m. the

spring,

thrown

off.

the winter scales and leaves are

Each tiny

scale

and winter

leaf

leaves a scar on the shoot just as the large sum-

mer

leaves do, only

it

is

a tiny Fig.

scar.

But there are many

close together all

scars

round the shoot,

68.

Shoot of

tuttemut showand buds.

it is

THE GKOWTH AND PARTS OF PLANTS

38

for,

we have

as

scales

seen, the winter

and leaves are seated so

the bud.

Each

of scale scars

is

in

year, then, a girdle

formed on the shoot.

How

old

is

the

branch you have ?

Get a shoot which has several girdle scars it

on

Cut

it.

through,

tween the

be-

girdle

Fio. 71

Shoot of butternut showing leaf scars, axillary huds, and adventitious buds (buds coining from above the axils).

Fig.

69.

Fig. 70.

Shoot and bud of white

oali.

Two-year old shoot of white oak showing where the greater number of branches

Fig. Fig.

(

71.

arise.

BUDS AND WINTER SHOOTS

How many

scars.

wood

?

What

rings

does this

show

mean

Other buds and shoots.

study the buds, the leaf

in the cut surface of the ?

Gather other

scars,

39

and

shoots

and

their arrangement.

Good ones

to study are the ash, ailanthus, walnut or

butternut,

oak,

elm,

birch,

dogwood,

peach,

apple,

willow, poplar, etc.

Some buds may be made

to

open

in

the winter.

Bring in shoots of dogwood, willow, poplar, ash, oak, etc.

Rest the cut ends in water and see what will

happen after several weeks or months.

CHAPTER

VII

THE FULL-GROWN PLANT AND ITS PARTS

THE PLANT

I.

The plant has

stem, and leaves. parts.

But the

roots, of course, are larger, longer,

and the stem

and the

fruit,

and

?

There are the flowers, you

and some plants have

tendrils.

and

many more leaves much branched. Are

There are

often very

is

there any other parts

hairs,

seedling has roots,

The full-grown plant has the same

much more branched. also,

Tke

different parts.

Yes, but

many

plants have just

the root, stem, leaves, flowers, and fruit. different they are in different plants

say,

thorns, spines,

!

And how

Did you ever

notice that the form of the stem, and the shape and

arrangement of the leaves and flowers mark the ent kinds of plants so that you can

The form habit.

of the entire plant

The

seeds of each

we

tell

call its

differ-

them apart? appearance or

kind of plant make new plants

of the same kind and shape.

The sunflower is tall and slender. Tall, erect plants. At first there is a simple, straight, tall, shaft-like stem, and large, spreading leaves pointing in different directions. 40

rULL-GEOWN PLANT AND At

ITS

PAETS

41

the top of the stem the

first and largest flower head formed, and others come on later from short branches in the axils of the upper

is

The full-grown

leaves.

plant has a golden crown of flower heads held

the

tall

stem

up by

shaft.

The mullein is also tall and slender,

with rough, woolly

and a long spike

leaves

yellow flowers.

of

The plants

and slender because main stem is so prominent and branches not at are tall

the

all,

or but

little.

In the

sunflower and mullein the habit

is

cylindrical.

Tall larches, spruces, and

These trees branch

pines.

very much. But observe how small the branches are com-

pared with the main shaft,

which extends straight through to the top. habit

is

The

like that of a cone.

^i«-

72-

cylindrical stem of mulleln.

The oaks and birches have a more or less oval habit. The elms have a spreading habit, and so on. Is a pine,

THE GROWTH

42

PARTS OF PLANTS

Al^B

form when

or oak, or other tree different in

alone in

a

from what

field

Can you

forest?

tell

it

grows

when grown

is

in a

why?

The strawberry,

Prostrate plants.

it

trailing arbutus,

You can find and others are prostrate or creeping. other plants which show all forms between the prostrate

and the erect

habit.

The Duration of Plants

Many

Annuals. field

and garden

new

ripen a

Then the plant

clear to us that a plant

embryo

and weeds of the

the flowers

from seeds

in the springtime

It

must be very

starts

from the tiny

dies.

which

in the seed, forms the full-grown plant, flowers,

ripens its seed in a single

growing season, and then

has spent

main purpose

seed.

and

crop of seeds in late spring, in summer, or

autumn.

in

of

start

its life

for the

of

dies,

forming the

The seed can dry without harming the young

plantlet within.

Do you know the

frozen

embryo form

?

that the seeds of

ground

all

These plants

many

plants

winter without

lie

killing

and grow, therefore,

live

may

seed, so that their kind

Plants which live for a single season

call annuals.

Beans,

morning-glory, ragweed,

corn, buckwheat,

etc.,

to

be perpetuated from

year to year.

peas,

in

the

are annuals.

we

wheat,

FULL-GEOWN PLANT AND When you

Biennials.

PARTS

ITS

plant seeds

of the

43 turnip,

radish, beet, carrot, cabbage, etc., a very short stem

formed the

is

season, with a large rosette of leaves

first

No

close to the ground.

flowers or seeds are formed

the

first

But

season.

if

these plants are protected

from the cold

of the winter,

the following season

tall,

branched stems are formed

which

bear

flowers

Then the

seed.

plants

and die.

The purpose of these plants, also, is to form seed and perpetuate their kind.

It

takes two seasons, however, to

form the

we

plant

seed.

Such a

a

biennial.

Fig.

call

The mullein

is

The

a biennial.

73.

Yfliite oak, oval type.

short stem and the

roots live during the first winter.

Perennials.

number

for a

We know

that trees and shrubs grow

of years.

All but the evergreens shed

their leaves in the autumn, or the leaves

leaves like

come forth

trillium,

in the spring.

golden-rod,

produce flowers and

stem above ground

aster,

Some Indian

seed each season.

dies

down

die.

But new

of the herbs,

turnip,

The part

etc.,

of the

at the close of the season,

THE GROWTH AND PARTS OF PLANTS

44

but the short stem under ground, or at the surface of

When

the ground^ lives on from year to year. seed germinates, the plant

so small at

is

for several seasons, that for the first ers

we know,

the

main purpose

plant's point of view,

kind.

few years no

is

to

of

flow-

live for

and the shrubs, we

In these plants,

perennial plants.

the

and even

Those herbs which

and seed are formed.

several years, as well as the trees call

first,

also, so far as

the plant, from the

form seed and perpetuate

its

Plants like the cotton, castor-oil bean, etc., are

perennial in the tropics but become annual in temperate zones, because the cold

weather

duce one crop of seed the

Woody

first

kills

which we

;

they pro-

season.

plants and herbaceous plants.

roots of trees

them

The stems and

and shrubs are mostly of a hard substance

call

wood.

plants, while the herbs,

They

are often called

whether annual,

perennial, are herbaceous plants.

woody

biennial, or

CHAPTER

VIII

THE FULL-GROWN PLANT, II.

What

ETC. (Continued)

THE STEM

are some of the different kinds of

stems that you can find in the

garden or greenhouse

in the

many forms and sunflower

is

long

wood,

?

There are

Tlie

stem of the

straight.

There are

shapes.

and

field or

short branches at the top where the plant

bears a cluster of large flower heads, the largest one

on the end of the main stem.

Did you ever

see a sunflower plant with

only one flower head there

is

The corn plant and examples of corn tassel the

stamen

another flowers,

Can you

?

tell

why

only one flower head sometirhes

tall is

bamboo are good

slender stems.

The

a tuft of branches bearing

The

flowers.

branch

and

and

the

which

later

silken

bears

the fruit.

the

ear

is

pistil

Are other

branches of the Indian corn ever developed

Wheat and

?

oats, also,

have

tall 45

?

and777 slender

fig.

74.

Sunflower, cylindrical type.

THE GEOWTH AND PARTS OF PLANTS

46

Perhaps

stems.

all

these plants have formed the habit

of long stems because they often

means

masses, and take this

grow

in large, crowded

of lifting themselves above

other plants in search of light and

air.

In the pines, spruces, and larches rises

like

a great

main stem

the

shaft from the ground

straight

through the branches to the top.

The highest part

end of this straight

is

the

shaft.

These trees have many branches reaching out in graceful curves, but the main

stem

remains

A

distinct.

stem which continues or runs through

to

the top is said to

Have you

he excurrent.

ever

been on the top of a mountain surrounded Fig,

a

forest

of

oaks, maples, beeches, pines, 75,

Conical type of larch.

and spruces ber

by

how

the

tall,

slender pines

or

?

You remem-

spruces

towered

above the oaks or beeches.

How is it with the oak stem ? The branches are larger main stem, so that the main trunk is Compare the oak tree or pine which has grown in the open field with those grown

in proportion to the

often lost or disappears. tree

in the forest.

How should you account for the difEerence ?

FULL-GROWN PLANT AND The trunk carefully the

of the

way

elm tree and

its

is

dissolved.

s

PAETS

branches.

47

Study

the branches of the elm are formed

and you will see why the main stem a stem

ITS

is

soon

said to he deliquescent, because

Compare

large elms

grown

it

in

lost.

Such

seems to be the forest

THE GROWTH

48

AifD PAETS OF

PLANTS

The strawberry, dewberry, and other prostrate stems We call them creeping or creep or trail on the ground.

The strawberry vine takes

trai lin g stems.

Pig.

77.

root

here

Prostrate type of the water fern (Tnarsilia).

and there and sends up a tuft of leaves and erect flower is

stems.

The

creeping

water

fern

(marsilia)

a beautiful plant, the stem usually creeping on the

bottom

of shallow

ponds or borders of streams, and

the pretty leaves with four leaflets floating like bits of

mosaic on the surface.

The pea, the Japanese ivy glory,

of support.

many

or

Boston ivy, the morning-

and similar stems cling to other plants, or places

They are climbing stems.

Then

there are

stems which neither climb nor creep, nor do they

FULL-GROWN PLANT AND

ITS

PARTS

49

stand erect, but are between erect and prostrate stems.

Some ascend;

that

is,

the end of the stem arises some-

what from the ground, although the

rest of it

These are ascending stems.

prostrate.

over so that the end

is

may

be

Others topple

turned toward the ground.

They are downward ient (decumbent).

Then there are stems which burrow, as it were. They creep along under the surface of the ground, the bud pushing or burrowing along as the stem grows. The mandrake, Solomon's seal, Burrowing

stems.

and the common bracken fern are well-known exam-

The mandrake and Solomon's seal, and some others, as you know, form each year erect stems which ples.

Fig.

rise

78.

Burrowing type, the mandrake, a

above the ground.

the surface

" rhizome."

Stems lohieh hurroxv along under

of the ground are called rootstocks, or rhi-

zomes, which means root form.

They

are

known from

THE GEOWTH AND PAETS OF PLANTS

50

roots because they have buds

and

the rhizome of the bracken

fern,

scale leaves,

though

the sensitive fern

and some others have large green leaves above the ground. The trillium has a

(see Fig. 93),

which

rise

short, thick rhizome.

Stems as Stoeehousbs foe Food Bulbs are familiar to

all

of

They

us.

short

are

stems covered with numerous overlapping thick scale

Some Some

leaves, as in the onion, the lily, or the tulip.

bulbs, like the Easter lily,

have a single stem. have the

several

Chinese

stems,

hke

or

the

lily,

" multiplier onion." Quantities of

food are stored up

in the thick scale leaves, to be used

by the plant

as

the flower and fruit stalk are being formed.

Chinese Fig.

79.

Bulb of

hyaointli.

that the bulb will

grow

lily

much food if it

is

there

In the is

so

in these leaves

placed in a

warm room

with the lower surface resting on broken bits of crockery

immersed

in a vessel of water, so that the fibrous roots

can furnish moisture. leaves, flower stem,

The

lily

will

develop green

and flowers from the food in the

FULL-GROWN PLANT AND scale leaves alone.

obtained from the

These Chinese florist

PAETS

ITS

and grown

51

bulbs can be

lily

in the schoolroom

or home.

Another kind of food reservoir

for plants is the tuber.

The most common and well-known tuber is the potato. a very much thickened stem. The "eyes" are buds on the stem. Do you know what develops from It is

these " eyes " tato

is

when

the po-

planted in the ]varm

ground

Place several tu-

?

bers in cups of water so that

one end will be out of the water, and set

window

of a

where they

them

warm

^^''^°-

in the

room.

Tuber of irish potato.

Place some in a dark drawer

will not freeze in winter

leave

;

them

for

about a year and see what will happen.

The potato

is

filled

underground stem.

from a "

If

with starch grains.

you dig away the you

hill " of potatoes,

It

is

an

soil carefully

will see that there are

underground stems more slender often than the erect ones,

which have buds and

the end there

is

scale leaves

often a potato tuber.

stored here for the good

of the potato.

be started from the tuber.

on them.

The starch

New

make

is

plants can

They grow more rapidly and

vigorously than from the seed of the potato. other animals

On

use of the potato for food.

Man and

THE GROWTH AND PAETS OF PLANTS

52

The

short, flattened

underground stem of the Jack-

in-the-pulpit is called a corm.

year.

Every spring

which

dies

down

it

This lives from year to

sends up a leafy flower stem

in the

Young corms

autumn.

are

formed as buds on the upper surface of the larger one, probably in the axils of older leaves which have

disappeared.

come

free

plants.

These

be-

and form new

Other corms are

the crocus, gladiolus, etc.

To

see

from

how corms

differ

bulbs, cut one open.

It is a solid, fleshy stem,

sometimes with loose, on the

scale-like leaves

outside.

Storehouses which are partly stem, partly root. Pig.

81.

Corm

of Jaok-iu-the-puluit.

«

,

.

,,

'

are round in the nip, beet, turnip, radish, etc.

the crown of leaves arises,

part

is

root.

Such a tuber

The upper

part,

pars-

where

is

the stem, and the lower

is

sometimes called a crown

tuber.

Food in

the

is

stored in rootstocks, or rhizomes, also, and

stems of

trees

and shrubs.

But the kinds

enumerated above show some of the results which the

FULL-GROWN PLANT AND

ITS

PARTS

53

plants have gained in forming special reservoirs for food.

Most

seeds,

as

we have

studied, are reservoirs of little

plantlet can feed on

germinate.

seen from

the few

food so situated that the it

as soon as

it

begins to

CHAPTER IX THE FULL-GROWN PLANT, III.

Taproots.

the

first

ETC. (Continued)

THE EOOT we found

that

downward, no matter in what

posi-

In the seedlings studied

root grows

tion the seed

is

This habit of

planted.

downward growth

in the first root

is

of

the greatest importance to the plant to insure a hold in the soil where

obtain a large part of water.

its

It also puts the root in

tion to send out in search of food,

numerous

must

it

food and

all its

a posi-

lateral roots

and serves

to bind the

plant more firmly to the ground.

In

some plants the first root, or the one which grows directly downward, maintains this direction, size as

compared with the

Such a root Fio.

82.

Taproot of

dandelion.

the

root

is

and grows to a large

is

lateral roots.

called a taproot.

a leader.

You

The

tap-

see it continues

through the root system somewhat as

main stems

of pines, spruces, etc., 54

do through the

FULL-GKOWN PLANT AND branches,

ITS

only

it

PAETS goes

55

down-

The dandelion is a good The turnip, carrot, example.

ward.

and beet The

also

root system.

a plant, with

Fig. 83.

have taproots.

The

all their

roots of

branches,

Fibrous roots of bean.

form the root system

Where

of that plant.

the roots are

and

all

many

more or

less

slender, the system

is

fibrous, or the plant is

said

to

have

fi-

hrous roots, as in the

clover,

wheat,

the corn, grasses,

Where one

or

etc.

more

of the roots are stout

and fleshy, the system is

fieshy, or the plant

Fig.

84.

Air roots of poison

ivy.

THE GROWTH AND PAETS OF PLANTS

56

have fleshy roots. Examples are found in the is

said to

sweet beet,

potato,

turnip, etc.

carrot, beet,

Bracing roots of Indian corn.

tubers,

is

52)

and

is

called

are sometimes

called

b e-

sprouting and

new Ex-

amine roots of a

number

of

plants to see if

they are

fi-

brous or fleshy.

Air roots.

Most roots with which we are

familiar

are soil roots, since they grow

Fig.

86.

a

fleshy

the sweet potato

capable of

potatoes.

also

The

cause they are

forming

In the

part stem (see page

root

roots of 85.

carrot,

and turnip the

crown tuber. Fig.

the

Bracing roots of screw pine.

root

PULL-GEOWN PLANT AND

ITS

PARTS

57

Some plants have also air roots (called aerial Examine the air roots of the climbing poison

in the soil. roots).

ivy, but be careful not to touch the leaves unless

know is

that

literally

wUl not poison

it

you

One side of the stem roots. They grow away

you.

covered with these

from the light toward the tree on which the ivy twines,

and fasten

quite

it

firmly to the tree.

Air roots or braces are formed in the Indian corn,

the screw pine, etc.

Air roots grow from the branches of the

banyan

tree of

and striking ground the into India,

brace the wide branching

system Pie.

87.

Buttresses of silk-cotton tree, Nassau.

of the stems.

Buttresses are formed partly of root and partly of stem at the base of the tree trunks where root and

stem

join.

The work

work the

for the plant.

The They

roots do several kinds of

serve to anchor plants to

or in the case of certain climbing plants to them to some object of support. They aid also

soil,

fasten

of roots.

THE GROWTH AND PAETS OF PLANTS

58

and in holding the trunk or

in supporting the plant

Another important work

stem upright.

of water

up

and

is

the taking

of food solutions

from the

soil.

of water

from the

In the absorption the root

soil

hairs of plants play a very active

Fig.

88.

Pull

lings

growing

Ficj. 89.

and

roots have not been

ish seedling.

pulling

up

broken

the plant, particles to

them which can-

not be washed

is

because the root

This

off.

hairs cling so firmly

to the soil particles.

This

91.

is

seen in Fig.

only moist the water

thin film, as thin as the ble,

which

lies

in

When the it

soil

particles.

film of a soap bub-

on

It

necessary then

for the root hairs

to fix themselves

very closely and grown under glass,

tightly i^ije

again st

Fig.

91.

Soil clinging to root hairs

corn seedling pulled from ground.

^q[i particles, so

soil

forms a very

the surface of the

seediing

ofE in

of earth will be clinging

is

is

rinse

If the smaller

lioot

hairs of rad-

ling.

of the seed-

in the soil

the roots in water.

Koot

hairs of sunflower seed•

up some

part.

that they

may come

in close contact with this film of water.

PULL-GROWN PLANT AND

ITS

While plants need a great deal

many

Most

moist, not wet.

many

much

kinds can thrive

where the

soil is

cultivated plants and

flowers and trees do better in well-drained land.

Perhaps you have seen of corn or field.

wheat look

This

is

wet

soil,

how

air.

many

small and yellow patches

in the low

because there

and not enough few trees and in

59

of water a great

better

the

of

PARTS

On

is

too

and wet parts of a

much water

in soil

the other hand, there are a

other plants which thrive better

or even in the water.

It

has been the

habit of the parents and forefathers of such plants to live in these

places, so they naturally follow in this

habit.

How

the roots and root hairs do the work of absorb-

ing the water from the

study of Chapters

soil

XI and

can be understood by the

XII.

CHAPTER X THE FULI^GROWN PLANT, ETC.

LEAVES

IV.

The

In the spring and

color of leaves.

leaves of different plants in the garden,

Examine those ter,

of

(Continued)

many

more.

and woods.

In the autumn or win-

plants in greenhouses or those

grown

will furnish leaves for observation.

the different leaves have

summer gather

field,

in the

What

room

colors do

The oak, hickory, maple,

?

elm, strawberry, dandelion,

corn, bean,

pea are

all

green in color.

Do you think that

Maybe you birch,

all

leaves are green ?

will see in

further.

some yard a copper beech, or

with leaves that are copper colored or brown,

especially those that are

They

Look

on the ends of the new

shoots.

then show shades of

when they get older. They brown and green. In the garden

or in the greenhouse

you may see leaves that are

are not so bright

brown, or partly green and partly white.

The

red,

coleus

plant has variegated leaves, part of the leaf being green,

and the middle part white

know

(see Fig. 148).

Many of you

the ribbon grass, striped white and green. 60

Why

FULL-G-ROWN PLANT AND ITS PAETS are leaves differing in color

61

from the common green

leaf usually found in the flower garden or greenhouse

Plants which grow in the fields and woods

have variegated leaves, but they are

?

occasionally

rare.

you should happen to find the Indian -pipe plant, or ghost plant, you would see that the leaves are white, They are very or sometimes pink, but never green. If

Fig, 92.

small.

Has

Purslane or " pusley " sliowing small thick leaves.

the dodder leaves

?

Yes, but they are yel-

They, too, are very small. Do you know any other plants which always have white Are the leaves of such plants always small ? leaves ? The green leaf, compared with white ones.i Compare

lowish white, not green.

You see that the green leaves with the white ones. such as nearly all the green leaves you have gathered, grown in the dark are often white. between leaves grown in the light. made be should comparison 1

The

leaves of plants

This

62

THE GROWTH AND PARTS OF PLANTS

those

of the oak, elm, maple, apple, bean,

corn, are broad

and

The

thin.

and narrow, but they are

thin.

pea, and

grass leaves are long If

you have gathered

some pine leaves, or leaves of the spruce, balsam,

how very

hemlock, or larch, you see

from the other

different they are

Perhaps you have never heard

leaves.

on the pine, for they are often called pine

of leaves

They

needles, because of their needle-like shape.

not so thin as most other leaves, and they are

Did you ever "pusley" thick.

fir,

?

see the purslane, or, as

some people

Its leaves are not very large,

are

stiff.

call

it,

and they are

So we find that while most green leaves are

You

broad and thin, some are not. the thin leaves wilt and

see

how

quickly

dry after they are picked.

the purslane leaves do not wilt so easily.

On

But

hot days,

during a long " spell of dry weather," did you ever notice

and

how many

suffer for

with the purslane Note

of the plants with green leaves wilt

want

During

of

water?

At such times how

?

late

summer and autumn

take on bright colors, such as red, yellow,

etc.,

the leaves of

The

beautiful coloring

going on inside the leaf during

The causes here. But

many

of varying shades.

pupils interested in gathering leaves will be attracted foliage.

is it

by

trees

The

this brilliant

is

the expression of certain changes

its

decline at the close of the season.

form too diiHcult a subject for discussion should be understood that the " autumn colors " of leaves

of these colors it

are not necessarily due to the action of frost, since

occur before the frosts come.

many of

the changes

FULL-GROWN PLANT AND

ITS

PARTS

63

The Form of Leaves Most leaves are Most green leaves are broad and thin. You have seen this by looking at different kinds of leaves. Have you noticed the shapes of leaves ? Yes, of course. You see the larger number of them have a little stalk Stalked leaves and sessile leaves.

green.

where they are joined

[petiole)

stem which holds out

to the

the broad

part

some of the stalk

is

many large

in

no

water-lilies

the

long and large.

In

ferns the stalk

and

many

is

also

sometimes taken

is

stem

for the

In

(blade).

(Fig.

But

93).

other leaves there

and the

stalk,

stem

seated

on

leaves

are

sessile.

plants

the

stem

the

blade ;

is is

such

In some appears

to Kg.

grow through the reality the leaf

the stem

;

leaf,

grows

all

but in

round

sometimes there

is

93. Sensitive fern showing large leaves and the rhizome or root-

stock which runs underground.

one leaf only at one point

on the stem, and in other cases two leaves which are opposite have their bases grown together round the stem. Simple leaves and compound leaves. How many difLook at ferent pieces are there in the blade of a leaf?

THE GROWTH AND PARTS OF PLANTS

64

the elm, the oak, the

lilac,

see the blade is all in

and the sunflower

leaf.

one piece, although the elm

You leaf

notched on the

is

edge, and the scarlet

oak

leaf

is

scalloped.

deeply

Where

the blade of the leaf is

in one piece

it is

called a simple leaf. Fig.

Elm

94.

is

leaf (stipules

blade of a bean leaf ash, hickory,

How many pieces

leaf

?

are there in the

a clover leaf

and ailanthus leaves

all these plants,

somewhat

where the

joined to stem).

like

you may

them.

?

of the oxalis, pea, If

?

find others

you do not

find

which have leaves

Perhaps you

thought each one of the pieces of the blade was the entire leaf. see

where the stalk

call

it

of the leaf joins

The leaf stalk and

the stem. that

But

supports

is

one

leaf.

all

We

such leaves as these compound.

Do you know a compound fern leaf ? The

pieces of each

are called

leaflets.

compound leaf Each leaflet is

Fig. 95.

Compound

leaf

of ash.

supported on the leaf stalk by a stalklet.

If

compound

you can find some

leaves,

of the different kinds of

make drawings

to

show the shape, and

FULL-GROWN PLANT AND where the bean

leaflets are

leaf, as

PARTS

ITS

65

The

attached to the leafstalk.

well as that of the pea, ash,

etc., is

c

mp

The

once

und.

leaves of

the sensitive

plant, of the

honey locust

and some others, are

twice

com-

pound, and so on. FiQ.

96.

Scales, leaves

and yoving Bummer leaves

bud of

in opening

ailantlius tree.

Leaves wearing a Mask

Masks on the pea leaf. Some of the leaves which you have seen may have puzzled you because they have parts which are not leaf\M.\kl The pea, for like.

example, has curled, thread-like

outgrowths

on the end, which we call tendrils.

These

tendrils cling to objects

and hold the pea vine upright. Now see where Fro.

these tendrils are joined

97.

Tendril of squash partly turned to leaf.

THE GROWTH AND PARTS OF PLANTS

66

They

to tlie leaf.

the

as

leaflets.

are in pairs, in the

Are

not

they

same

leaflets

positions

which have

changed in form to do a certain kind of work for the plant f Has the leaflet here given up its thin part and kept the midrib, or vein,

do

new work?

this

part of the pea leaf

under a mask ;

it is

to

This

then

is

disguised.

Masked leaves

of the

squash

or

pumpkin.

Ex-

amine

the

tendrils

on a

squash or pumpkin vine, or

some one of

their near rela-

tives.

Draw

tendrils

and show how they

a cluster of

attached to the vine.

are

Make

a drawing of a

Compare the two.

Do

tendrils correspond

to

large veins of the leaf Fig.

98.

you ever

Awl-shaped leaves of Kussian

leaf.

?

the the

Did

find one of these

thistle.

which was part part tendril

Can you

?

tell

and

a very interesting story.

tell it ?

Spine-like

growing

Such leaves

leaf

leaves.

If

are

examine them.

in the yard,

do the spines occupy

there

?

barberry bushes

What

position

See the short, leafy branches

FULL-GROWN PLANT AND which Is

ITS

PARTS

67

between the spines and stem.

arise in the axil

not the spine a mask under which some of the

barberry leaves appear

Not

all spines,

?

however, are masked leaves.

do the spines or thorns occur on the hawthorn

you ever seen

?

Where Have

them on the Rus-

on the amarantus, or pigweed, as it is sometimes called ? What are the spines on sian thistle, or

a cactus

on a

?

What

thistle,

thistle or

are the spines

like

common

the Canada thistle

?

The Position of Leaves The

plants in the

field, forest,

and garden, as well as those

grown in the house, can tell some interesting stories about the positions of their leaves on the stem.

The plants speak

a very quiet way.

We

Fig.

99.

Spines on edge of

common

thistle leaf.

in

cannot hear them, because they

speak in a sign language. Now you know what this means, so you must look at the plants and see how the The position of the leaves on the leaves are arranged. plant does,

is

the sign.

You

are to act as the interpreter

and put what the leaves

tell into

your own words.

THE GROWTH AND PAETS OF PLANTS

68

One

of the plainest signs

can be understood

if

which the green leaves make

you compare a geranium plant

grown in the window with one grown out of doors, or in a glass

house where

the light comes in from

above as well as from

The

leaf

wants to face the

light,

one

side.

to be in such a position

on the plant that get

light

directly

easily

can

it

and

on the upper

surface.

In the corn plant, the sunflower, or the mul-

with erect and usually unbranched lein,

stems, the leaves stand

out horizontally, so that

they get light from the Fig. 100.

Garden-balsam plant showing leaves near ends of branclies.

see also that in

most cases one

sky where

it is

strong-

est (see Fig. 72). leaf is

You

not directly over

They are set so that they do not shade one another. If two leaves are in the same perpendicular line, one is so much above the other on the stem that another.

the slanting light can easily reach the lower one.

rULL-GEOWN PLANT AND The garden-balsam plant, tells

ITS

or the wild

branched, and in an old plant

all

69

" touch-me-not,"

You

the same story and more.

PARTS

see the

stem

is

the leaves are near

the ends of the branches, and on

As the

top.

branch grew in length the leaves

reaching out aU

around cut off much light from the center of the

plant, and the leaves here, which were formed when the plant

was younger, became so shaded that they died and

fell

away.

Can you read this story in other plants

Fig. 101.

" Feather down," elm.

?

The leaves

of

many

trees tell a similar story.

the trees are in leaf observe

how

on the oaks, maples, elms,

etc.

position of the leaves varies

When

the leaves are arranged

You

will see that the

somewhat

in different trees

;

THE GROWTH AND PARTS OF PLANTS

70 of the

The

same kind.

has a great

many

oak, or elm, or apple tree, which

branches, will have nearly

all

its

These allow so little light to

leaves on the outside.

get to the inside of the tree that few leaves are formed

Have you

there.

seen trees of this kind on which there

and down its a tree which by What story is large branches ? has a great many leaves in its center ? Did you ever were

many

leaves all through the tree told

see a tall tree standing alone in a field or a yard, with

a great

many

from

leaves standing out

young branches

What

?

The story that leaves

its

story do they tell

of forest trees tell.

trunk on

?

In the deep

forest all the leaves of the larger trees are at the top.

When

these were very

the ground.

The young

Now

ground.

young trees

trees, the leaves

had branches

were near

also near the

the old forest trees show no branches

They have long, straight, bare The great mass of leaves in the top of the

except near the top. trunks.

forest tell us that they shaded the lower branches so

much

that few or no leaves could

the branches died and dropped in here

and

there, so that the

have some leaves on them. leaves on

young maples,

grow on them, and

off.

A little light comes

young trees But do you

pines, oaks,

in the forest

see so

and other

many

trees in

a deep forest, as you do on trees of the same

growing in an open there are

field ?

some plants which

The

size

forest also tells us that

like to

grow

in its shade

THE GEOWTH AND PAETS OF PLANTS

72 for

we

find

grow well

them doing well open

in the

there, while they cannot

field.

The leaves of most plants Most trees and shrubs shed live but a single season. Evergreen trees form a their leaves in the autumn. The duration

of leaves.

crop of leaves each season, but these leaves remain on the tree for more than a year, in some trees for several years, so that the trees are green during winter as well

as

summer. The veins

you examine carefully the

which you have gathered while learning the

leaves

and form, you

stories of their color

them have

veins, as

we

call

where the

will see that all of

them.

on the underside of the

cially lines

If

of leaves.

leaf as

These show espeprominent raised

leaf substance is thicker.

There are

The midrib of the leaf The smaller veins branch out

large veins and small ones. is

the

largest vein.

from the larger ones, or If

arise at the base of the leaf.

you look carefully at the leaves of some plants

tonia, for

smallest veins form a fine network. of veins in a leaf

Where the

the leaf the leaf

it

entire system

is

is

leaf.

Where

said to be net-

veins run in parallel lines through

parallel-reined.

You have observed that

The

forms the skeleton of the

the veins form a network the leaf veined.

[Fit-

example. Pig. 102), you will see that the

the germination of the corn, and

has one cotyledon.

How

do the veins in the

FULL-GKOWN PLANT AND leaves of the corn run

?

pumpkin, sunflower, oak,

How

ITS

PAETS

73

In germinating beans, peas, etc.,

you found two

cotyledons.

do the veins in the leaves of these plants run

?

The work of leaves. Leaves do a great deal of work. They do several kinds of work. They work together to make plant food, and to do other work which we shall learn later.

Part

II

THE WOUK OF PLANTS CHAPTER XI HOW THE

LIVING PLANT USES

To restore firmness

how soon

WATER TO REMAIN FIRM

in wilted plants.

unless they are kept where the air

times

we

restore wilted flowers or

or firm condition in

is

all

know

By

Many

moist.

plants to a fresh

by putting the cut stems

water for a time.

show how

We

flowers or plants wilt after being picked,

or roots

a simple experiment one can

to hasten the return of firmness or rigidity

in the wilted plant.

Cut

the seedlings growing in the

soil.

on the table for several minutes

until

off several of

Allow them they droop.

to lie

Put the stem of one in a glass

and place over

a glass of water imcovered.

of

water

Leave another stem

this a fruit jar.

in

The covered one should

revive sooner than the uncovered one.

How

beet slices remain rigid.

from the

soil is

quite firm. 74

A

beet freshly dug

Cut out

slices

from the

HOW THE

LIVING PLANT USES WATER

75

beet 4 to 5 cm.^ long, 2 to 3 cm. broad, and about 4 to 5

mm.

finger

thick. Hold tbem between the thumb and and try to bend them. They yield but little to

They are firm Place some of the slices

pressure.

solution,^

or rigid. of beet in a five per cent salt

and some in fresh water.

After a half hour

by trying

or so, test the slices in the fresh water

Fig. 103.

Beet

slices

;

hand one

to

one after lying in salt solution, rigMwater and placed in fresh -water.

at left fresh one, middle talcen

from

salt

bend them between the thumb and remain rigid as before.

Now

finger.

test those

been lying in the salt solution.

They

They

which have

are limp

and

flabby and bend easily under pressure.

from the salt solution and After an hour or so test place them in fresh water.

Now '

2

The

remove the

2^ cm.

=

1 inch.

25

slices

mm. =

1 inch.

tumbler of water. Dissolve a rounded tablespoonf ul of table salt in a one. cent per five nearly a be will solution

THE WOEK OF PLANTS

76

them

again.

They have regained

their rigidity.

In-

stead of being limp and flabby they are firm and plump.

from this that they

It appears

have regained their firmness

by taking in or absorbing water. The slice of beet, like all parts of plants, is made up

many cells,

of a great

are called. Fig.

Make-believe

104.

cell,

with sugar

ment

like tiny

boxes packed close

Each one absorbs

Perhaps the following experi-

will help us to understand

A make-believe plant cell. vial

cells are

together.

solution inside, lying in water.

water and becomes firm.

These

as they

Pill

how

this takes place.

a small, wide-mouthed

with a sugar solution made by

dis-

solving a heaping teaspoonful of sugar in

a half cup of water.

Over the mouth

firmly a piece of a bladder

(The footnote, page 90,

tells

get a bladder membrane.)

Be

as the

membrane

end of the

vial,

is

tie

membrane.

how

to

sure that,

tied over the

the sugar solution

open

fills it.

Sink the vial in a vessel of fresh water Fio.

and allow

it

to remain twenty-four hours.

105.

lieve

Make-be-

cell after

taking in water.

Then take it out and set it on the table. The membrane which was straight across

now bulged

out because of inside pressure.

at first

is

HOW THE

LIVING PLANT USES WATEK

77

Now

sink the vial in a very strong sugar solution for several hours. There should be so much sugar in the water that all of

it

The mem-

will not dissolve.

brane has become straight across again because the inside pressure is removed. Now sink it in fresh water

The

again.

Fig. 106.

water

inside pressure returns,

and the membrane

cell, at left before placing in water, middle one after lying in pressure, one at right after lying in very strong sugar solution

Make-believe lias inside

has collapsed or become flabby.

bulges again.

Thrust a sharp needle through the

brane when

it is

out again.

The

mem-

arched or bulged, and quickly pull

it

liquid spurts out because of the inside

pressure.

What

is it

that causes the inside pressure

the inside pressure removed in the stronger solution

?

when

the vial

?

is

Why

is

immersed

THE WORK OF PLANTS

78

Movement of water through memhranes. This experiment illustrates the well-known behavior of water and solutions of different kinds when Water moves separated by a membrane. quite readily through the membrane, but the substance in solu-

Fig.

Puncturing

107.

a malce-believe cell after it has been lying in water.

tion

moves

with

difficulty.

Also

the water will

move

more readily

through

in

the

direction of the The

stronger solution. or but

little, in

solution.

fresh water has no substance,

The sugar

solution

is

stronger

than the water, so the water moves readily through the

membrane into it. Now when the immersed

vial containing the sugar solution

in

fresh

through the

mem-

water, some

brane into the sugar

y-''

solution, because this

Fig.

__-

IS

stronger,

.

lOS.

same

after needle

is

of

the

is

water flows

as Fig. 107,

removed.

ihis

increases the bulk of the sugar solution

and

it

presses against the

making

When some

it

it

is

tight

and

membrane,

firm,

or rigid.

placed in the stronger solution, this draws

of the

water out, and the membrane, losing

firmness, becomes flat again.

its

HOW THE How

LIVING PLANT USES

the beet slice works.

The

WATER

beet slice

is

79

not like

a bladder membrane, but some of the substances in the beet act like the sugar solution inside the vial.

In

fact, there are

certain sugars

and

salts in

solution in the beet,

and

it

is

the "pull" which these

Fig. 109. Picture of a real plant cell, at left it is in natural condition, middle one after lying in a salt solution, one at riglit after being taken from salt and placed in water.

on the water outside that makes the beet rigid. While these sugars and salts in the beet draw the water exert

what is there in the beet which acts like the bladder membrane through which the water is " pulled," and which holds it from flowing quickly out again ? In the ieet slices there are thousands of tiny membranes of a inside,

slimy substance in the

Every one of

a tiny box.

Fig.

110.

form of rounded these formes

sacs, each lining

a plant

cell,

and

Cells of beet slice, at left fresh, middle ones iust placed in salt water,

ones at right after lying in salt water a few moments.

acts like the bladder

Inside these tiny

beet are

in

membrane

in the make-believe

membranes the sugars and

solution.

When

the

cells

cell.

salts of the

are .full

and

THE WOEK OE PLANTS

80

plump they entire

mass

and make the the beet firm and plump. They are

press against each other of

too tiny to be seen wii^out the use of a microscope,

but

A

we can look dead beet

some pictures

at

slice

of them.

Place some of the

cannot work.

fresh slices of beet in boiling water for a

with pressure.

They

are flabby

them

few moments,

Then

or in water near the boiling point.

and bend

them

test

Place

easily.

in fresh cold water,

in about

an hour

They

again.

are

and

them

test still

limp

and do not again become firm.

Why

is

the hot

membranes

this

It is because

?

water killed

all the tiny

in the beet, so that they cannot

longer do the work. then, these tiny

they are alive

In

living plant,

the

membranes are

;

and

alive.

Yes,

really, they are the liv-

ing substance of the plant.

Usually there

are strings or strands of the

same

living

substance extending across the sac like a

The water

rough network. with the sugars, Tig. 111. Sunflower seedling fresh. It is

firm.

When

is

in the plant,

salts, etc., dissolved in

it,

inside the sac.

Why

the dead beet slice cannot work.

the living substance

is

killed the tiny

can no longer hold the sugars,

membranes

salts, etc., inside

them.

HOW THE These escape and

LIVING PLANT USES WATER filter

81

through into the water outside.

In the case of the heet this

is

of the red coloring matter,

shown by the behavior

well

which

also in

is

the water, inside the tiny living membrane.

When

the living beet

slice is

placed in cold

water the red coloring matter does not escape

and color the water. Nor does the salt solution pull it

out

slice

when we in

place the

salt water,

al-

though some of the water is

pulled out.

the beet slice

But when is

kUled in ^'*-

hot water the red color

^^^-

same seedlmg

as

shown in

Fig. Ill

lying in salt water.

escapes.

How water.

other plant parts behave in salt solution and in

Pull up a sunflower seedling or some other It is firm

plant. as

we

hold

it

and

rigid

in the hand,

and the leaves stand out

shown in Fig. 111. Immerse the leaves and most well, as

of the

stem in a

five

per cent

salt solution for fifteen Sunflower seedling taken from the salt

Fia.

113.

water.

as

shown

It

is

limp.

in Fig. 113.

utes.

Now

hand.

It is

hold

it

min-

in the

limp and flabby.

Immerse the seedling

in fresh

THE WOEK OF PLANTS

82

water for half an hour and test gained

its

again.

it

former firmness, as shown

It

has

re-

Can

in Fig. 114.

you account for the behavior of the seedling under these conditions?

How

would

immerse

it

it

behave

we should

if

in boiling water for a

few moments

?

Why ?

Immerse

in alcohol for fifteen minutes. effect has the alcohol

Immerse a red beet

it

What

had on

it?

slice in alcohol.

Describe the results.

Other plant parts in the

same way,

may if

it

be treated is

desired

to multiply these experiments.

The effect of too strong

food

in the soil. Fig. 114.

solutions

Some

of

Sunflower seedling

taken from salt solution and placedin water. It becomes firm again.

the plant foods are in the

in the

form of

salts are too

dant in the

salts

If the

soil.

abun-

soil,

Fig. 116.

Fig. 116. Washing the salt out of the soil.

the

food solutions are so

take them up.

Sunflower seedlings

salt solution was poured in soil.after

In

strong that the plant

fact, too

cannot

strong solutions will draw

HOW THE

LIVING PLANT USES

WATER

83

water from the plants so that they will become hmp and will fall down, as shown in Fig. 115, where a ten per cent salt solution was poured into the soil.

After these plants had collapsed,

tap water

was allowed

to

run through

the soil overnight, as shown in Fig. 116.

In the morning the plants had straightened up. again, as shown in Fig. 117, because the excess of salt was washed out of the soil

and the root

hairs could then

absorb water.

How some firm.

stems and petioles remain

so

been washed out

Did you ever think how strong

some stems and up

Fig. 117. After the surplus salt has

petioles

much weight

or rhubarb leaf

is

must be

of

the soil the plants revive.

to hold

as they often do

The

?

pie plant

very large, broad, and heavy.

we

leafstalk, or petiole, as is

quite soft, yet

it

The

call

it,

stands up firm

with the great weight of the leaf blade on the end.

shave

off

strips

If

you

one or two thin

from the

side,

it

weakens the leafstalk greatly.

Why

does

the

leafstalk become so

weak when Leaf of pie plant (rhubarb) before and after

sliav-

ing off two narrow stripe from the leafstalk.

^Jj^g

SUrf aCe

so little of is

TCmOVed ?

THE WOEK OF PLANTS

84

Cut a piece from a fresh leafstalk^ six or eight, Cut the ends squarely. With a knife inches long. remove a strip from one side, the entire

Try

length of the piece.

to put

than

It is shorter

place again.

Remove another

before.

in

it

was

it

and

strip

another, until the entire outer surface

has been removed.

Now try

to

put one

of the outside strips in place again. is

now

shorter than before as compared

with the center

You Fig. 119.

Portion of

leafstalk

It

when

see

removed

it

piece.

the outside strip was

When

shortened up.

all the

of pie

outside strips were

plant witli one strip

removed the center

removed.

piece lengthened out.

can

why

tell

course

it

of water in

Strips

to

make

from outside of leafstalk of pie plant placed in water, at

If pie plant

in greenhouses of elder are

it

Of the

But the center piece alone, with plenty

coil up, at right in salt

1

now you

that the leafstalk was so firm.

must have plenty

cells firm.

Fig. 120.

it is

I think

is

they

water they uncoil.

cannot be obtained, the plant excellent.

left

of

known

as

Caladium

In early summer the young soft shoots

good for the experiment.

HOW THE water,

is

limp.

LIVING PLANT USES WATEE

You

outside strips, as

part

is

it

is

pulling to shorten the stalk and the center

and

the inside

Why

when it is covered with the when undisturbed, the outside

see

pushing to lengthen

off

outside parts

makes

the stalk firm.

Did you ever break

the dandelion stem curls.

it coil

up

Do you know why

Fig. 121.

Strip

it

into beautiful curls as

does so

water at right

it

The

inside part

at left

it

gradually coils up,

until life

it

it

will curl

So when

it is split

around toward the outside part.

Split a

Watch

split

trying to lengthen, and the

is

outside part is trying to shorten. curls

splits ?

uncoils.

a stem with a knife or with your fingers little.

it

Even when you

I

from dandelion stem in water, in salt

it

is

This lengthwise pull between

it.

a dandelion stem, press one end against your tongue,

and make

a

85

it.

stem and place

makes a very

substance in the tiny

so, that all

To prove

in a vessel of fresh water.

it

more and more and more, The coil of several rings.

It begins to curl

close cells

takes in

more

loater

and siuells

together they push harder than they did before. this,

in salt water.

put the strips from the dandelion stem

They begin

to uncoil

and

finally

become

THE WORK OF PLANTS

86

We know this is nearly straight and quite limp. " " pulls water out of the cells, just as the salt because does

it

Now the

in

the beet

place the strips from salt

water

fresh water.

firm and coil

How of

a

a

back into

They become up again.

to imitate the coiling

tendril.

fully a

^fW^%/

slice.

Cut out care-

narrow

strip

from

long dandelion stem.

Fasten to a piece of

soft

wood, with the ends close together, as

122. Fig.

122.

Strip

made to

from dandelion stem

Now

shown place

it

water

and watch

Part of

it coils

imitate a plant tendril.

one

in Fig. in fresh it

coil.

way and

part another way, just as a tendril does after the free

end has caught hold of some place for support.

CHAPTER HOW THE ROOT

WATER

LIFTS

To

Root pressure in seedlings. the

seedlings

flower, bean,

and others.

which

XII IN THE PLANT see this

we may

growing vigorously

are

—

use sun-

pumpkin, buckwheat,

With a sharp

knife

cut off the stem near the upper

In a few minutes a drop of

end.

water will be seen forming on the cut end of the stem.

This

in-

creases in size until a large, round

drop

is

formed.

We know

that

water would not flow upward out of the

stem unless there was some

pressure from below. sure comes from

power as

of

the absorptive

the roots.

we have found

This pres-

The

roots,

in our previous Ju^-^^^j:.

study, take up water from the

soil pig.

through the root hairs so forcibly as to produce

an

inside pressure

123.

Drop of water pressed

^^floLrsU^tagty woTk °°"-

of

This water

is

passed

inward in the root by a similar process until

it

reaches

which makes the

tissue firm.

87

THE WOEK OF PLANTS

88

minute vessels or tubes which are continuous with similar

tubes in the

M^^^

The continued pressure

stem.

which

is

formed in the roots

the water up and forces

it

lifts

out

through the cut end of the stem. (The bleeding of cut stems in winter or early spring

due to

is

changes in the expansion of the air,

because of the great

differ-

ences in temperature.)

Root Pkbsstjre in a Garden

Balsam The materials necessary study.

for the

Select a vigorously grow-

ing potted garden-balsam plant. If this is not at hand, use a coleus

plant, geranium, or other plant.

Select a

piece of

several feet long

glass

tubing

and about the

same diameter as that

of the

of the plant to be used.

stem

Next

prepare a short piece of rubber

tubing which will Fig.

124.

Cutting off stem of

balsam plant.

end of

slip

over the

the glass tube.

Then

have ready some wrapping cord,

a small quantity of water, a

tall stake,

and a sharp

knife.

HOW THE EOOT To

start the experiment to

LIFTS

show

WATER

89

root pressure.

With

the knife cut off the stem squarely near the ground, as shown in Fig. 124. Slip one end of the rubber

tubing over the end of the stem and tie it tightly with the wrapping cord. Then pour in a small quantity of

water to keep the end of the stem moist at the

start.

Insert one end of the glass tubing in the other end of

Fig.

125.

The materials

the rubber tube,

for setting

up the apparatus

tie it tightly,

tubing to the stake to hold

must be made

in a

room

it

in

to

show root

pressure.

and then bind the glass

upright.

The experiment

which the temperature

is

suitable for growth.

The

result of the experiment.

In a few hours the

water will be seen rising in the glass tube.

This will

continue for a day or two, and perhaps for a longer time.

The

soil in

the pot should be watered just as

the entire plant were growing.

if

Observations on the

THE WOEK OF PLANTS

90

water

height of

the

should be

made

the. tube

in

several times a day It will be

for several days.

found

that the column rises and falls, show-

ing that there

is

some fluctuation

in

the pressure from the roots.

Thus we

see that the roots

by

their

power are capable, not

absorptive

only of taking in water from the

soil

with considerable force, but also of lifting it

up

in the stem.

cannot

lift

trees.

tall

to a considerable height

Root pressure, however, the water to the tops of It

has been found that

the root pressure of the birch can

water

lift

84.7 feet high, the grapevine

36.5 feet, and the nettle 15 feet.

A how

simple experiment to illustrate

Here

root pressure works.

is

an

experiment, easy to perform, which illustrates

\

vm

works

very well the

in lifting water.

tube (Fig. 127) and

sugar solution.

fill

way

the root

Take a thistle with a strong

Tie tightly over the

large open end a piece of a bladder Fig. 126. The experiment in operation showing '

water rising tube.

in the glass

Get one sheep's bladder, or

^

several, at the

butcher's and remove the surplus meat.

Inflate,

HOW THE ROOT membrane,

after soaking

it

LIFTS "WATER to

make

91

pliant.

it

Pour

out from the small end enough of the solution so that

it

will stand but a short distance above the bulb in the

narrow part

of the tube.

Invert this

in a bottle partly filled with water, pass a

down

perforated cork

mouth tion,

the tube and into the

of the bottle to hold the tube in posi-

and bring the tube

so that the sugar solution

in the tube level as the bottle.

is

same

at the

water in the

Allow

this to rest

for several hours.

experiment has

If the

been

set

up properly, the

sugar solution

now stands

higher in the tube than Fig. 127. " thistle

.

tube.

the level of the water.

Because the water in the

tube has sugar dissolved in

a stronger solution; that stronger

concentration

water in the

bottle.

it, it

is,

is

of a

than the

In such

Fig.

128.

Apparatus with

thistle tuhe, bladder

cases,

mem-

brane, and sugar solution to imitate root pressure.

where the two liquids are separated by a membrane, more water always goes through into tie

the open end, and place where

a membrane can be

it

will dry.

cut whenever wanted.

From these

dried bladders

Soak in water before using.

THE WORK OF PLANTS.

92

The bulk

the stronger solution.

thus increased, and

The

root acts

much

of the sugar solution

is

forced higher up in the tube.

it is

same way, except that

in the

each of the tiny root-hair

cells

and the tiny

cells of

the

root act as the thistle tube and sugar solutions do, or

The sap in the cells is a sugars and salts. The life substance

as the make-believe cell did.

solution of certain

(protoplasm) in each cell lines the cell wall and acts

water in the but

roots,

the

life

easily

The

membrane.

like the bladder

soil

outside the

is

comes in touch with

membrane because

through the

it filters

cell walls.

So

work

together,

and the

result of their

combined

work

like that of

all

the tiny cells

is

the thistle-

tube experiment.

A

potato

represent the hair,

or

tuber. The same apparatus shown in Fig. 128, but a

Fig. 129. as

a plant takes the place of the bladder membrane. leaf of

it,

work

of the

cylindrical

may

tube

be

used to

of

a single root

root.

Cut out a

piece

from

a

potato

Bore a hole nearly through

forming a tube closed at one

end.

Place in the bottom of this

tube a quantity of sugar and rest

the tube in a shallow vessel of water.

Observe

the sugar becomes wet from the water which

is

how

drawn

HOW THE EOOT through, the potato tube.

LIFTS

WATEE

Does the water

93

rise in this

tube above the line of the water in the vessel outside

?

Why? Note.

—A

membrane.

living leaf of a plant

may

take the place of the bladder

In the experiment illustrated in Fig. 129 the leaf of

the jewel weed, or wild touch-me-not (Impatiens),

the bladder membrane.

was used instead of which is free

It is necessary to select a leaf

from any puncture, and it must be tied on carefully with a soft cord. In this experiment the sugar solution rose two or three inches in a day,

and then rose no further. The thistle tube was then carefully lifted out, and the leaf was allowed to come in contact with boiling water to The tube was then replaced in the bottle of water. Strange kill it. as it may seem, the dead leaf worked much better as a membrane than the living leaf, and the sugar solution rose to near the top of the tube in two or three days.

CHAPTER HOW PLANTS What becomes

of the

XIII

WATER

GIVE OFF

water taken up by the plant?

"We have learned that the food which the plants take

from the it is

soil is

taken up along with the water in which

We know

dissolved.

that the solutions of plant

food must be weak, or the plant

them.

A

large

amount

is

not able to absorb

of water, then,

is

taken up by

the plant in order to obtain even a small food.

We know

also that

water

is

amount

of

taken up by the

roots of the plant independent of the food solutions in

it.

It

is

of

great

interest, then, to

know what

becomes of the large amount of water absorbed by the plant.

Some

plant, but

of the water is used as food by the would be impossible for a plant to use the water which it takes from the soil.

it

for food all

Loss of water by living leaves. leaves, or several leafy shoots

them on the in Fig. 130.

leaves under

table

from fresh

plants.

and cover them with a

Place another jar by it.

Take a handful

Be

its side,

of

Place

fruit jar, as

but put no

sure that the leaves have

water on them and that the jars are dry.

no

free

In the

course of fifteen or twenty minutes you can see a thin 94

HOW PLANTS

WATER

GIVE OFF

95

film on tlie inner surface of the jar covering the leaves.

In fifteen or twenty minutes more this is water, for it

riG. 130.

To show

which become

The other

will be seen that

water from leaves, the leaves jast covered.

loss of

larger

the

as

experiment continues.

The water,

jar is dry.

formed the mioisture

it

accumulating in small drops

is

film,

and

then,

which

later the drops,

first

on the

inner surface of the jar covering the leaves must come

Fig. 131.

from the

After a few hours drops of water have accumulated on the inside of the jar covering the leaves.

leaves.

We

see that

it

is

not only on the

sides of the jar, but also

on the top above the

So the water did not run

off

the leaves.

leaves.

THE WORK OF PLANTS

96 Further,

we cannot

any sign

see

on the

see it acciimulating

jar, so

from the leaves in a very can

that

we

naust pass off

it

light form, so light that

it

the air like dust without being visible.

float in

When

of water until

water

is

in this

The water passes

off

form in the

from

we

air

call it vapor.

the leaves in

form of

the

water vapor. Loss

of

water from

living

In the above

plants.

experiment the leaves were removed from the plant. It

is

not certain from this

water passes

experiment whether the

from the surfaces of the

off

leaf or

from

the broken or cut ends of the petioles.

We

are going to test the living plant

To do

in a similar way.

potted plant under a

this, place

tall bell jar,

a or

invert a fruit jar over the plant, after

having covered the pot and

soil

with

a flexible oilcloth or sheet rubber, or several layers of oiled paper.

Tie the

paper close around the stem of the prevent the evaporation of

plant to

water from the Fig. 132.

Water

is

given

by the leaves when attached to the living off

Several ,

During

or pot.

•

j-

De scen

soil

hours the moisture film can

lormmg on

glass vessel.

t

•

.

i

i

i-

the mside oi the

Gradually

it

accumulates

until

numerous drops are formed, some of which

time

may

trickle

down

the

side

of

the jar.

in

The

HOW

PLANTS GIVE OFF WATEE

accumulation of the moisture

may

97

often be hastened

or increased at certain places on the jar by holding

a piece of

The

near the jar outside.

ice

cold glass

condenses the water vapor into water again, in the

same way that the cold air above condenses the water vapor as it arises from the earth, first forming clouds and later raindrops. The living plant, then, loses water through

A

its

surface in the

form of water

vapor.

escape of water vapor from

delicate test for the

plants.

A very pretty and

of water

vapor from living plants can be made in this

Make

way.

delicate test for the escape

a solution of a substance

known

as cobalt

chloride in water.

Saturate several pieces of filter paper it.

Allow them

to dry,

and then dry

with

them

still

oughly

more

thor-

by holding

them near a lamp or gas

jet,

or in a

You

oven.

warm

will ob-

serve that the water

solution of

cobalt

red.

is

wet

moist paper

or

thoroughly dry

off

The

chloride

A good way to show that the water passes from the leaves in the form of water vapor.

Fig. 133

IS

it is blue.

.

also

red,

but

when

it

is

It is so sensitive to moisture

THE WOEK OF PLANTS

98

that the moisture of the air is often sufficient to redden the

paper.

Take two jar

a potted plant,

place

covered

shown

bell jars, as

as

described on

the pot and earth being

page

Or

96.

cover the

Pin to a stake in the pot a

plant with a fruit jar.

piece of the dried cobalt paper,

pin

In one

in Fig. 133.

and at the same

tinie

a stake, in another jar covering no plant,

to

They should be

another piece of cobalt paper.

dried

and entirely blue when they are put into the both should be put under

the jars at the

jars, and same time.

In a few moments the paper in the jar with the plant will begin to redden.

minutes, probably,

it

In a short time, ten or

fifteen

be entirely red, while the

will

paper under the other jar wiU remain blue, or be only slightly reddened. the living

off

from

plant comes in contact with the sensitive cobalt

chloride in sufficient

The water vapor passing

the

paper and reddens

vapor present

it

to condense as

before

there

is

a film of moisture

on the surface of the jar.

The

loss of

water from plants.

This

is

similar

to

evaporation, except that from a given area of leaf surface less water evaporates than of water surface.

in that the living plant is

back the

loss of water.

following way.

from an equal area from evaporation

It further differs

Pull

up

enabled to retard or hold

This

may

several

be shown in the

seedlings of beans,

HOW PLANTS sunflowers,

etc.,

one

and take some leaves

of

99

geranium or

lots, having in the an equal number of the various kinds. Immerse

lot in boiling

water for a few moments to

Immerse the other

plants. to

WATEE

Divide them into two

other plants. lots

GIVE OFF

have the living plants

the experiment. dry.

In

wet

at the beginning of

lots out

on a table

examine them.

hours

have

killed

the

lot in cool water, in order

also

Spread both

twenty-four

which were

kill

lost

to

Those

much more water than

Some of them may be dried so that The living plants are enabled to retard

the living plants.

they are

crisp.

the loss of water, so that the process of evaporation

hindered, not only

by the

action of the

life

is

substance

within the plant, but also by a regulating apparatus of the leaves.

The

these conditions

we

loss

of water from plants under

call transpiration.

Does transpiration take place equally on both surfaces This can be shown very prettily by using

of the leaf ?

the cobalt chloride paper.

Since this paper can be

kept from year to year and used peatedly,

it

is

re-

a

very simple matter to

make

these

experiments. Provide two pieces of Fig. 134.

glass

(discarded

The

holes (stomates) in the leaf bordered by the guard cells,

;

THE WORK OF PLANTS

100

glass negatives, cleaned, are excellent),

two

pieces of

cobalt chloride paper, and some geranium leaves enDry the paper until it tirely free from surface water. Place one piece of the paper on a glass plate is blue.

place the geranium leaf with the underside on the paper.

On

now

the upper side of the leaf

place the other cobalt paper,

and next

On

the second piece of glass. pile place

the

a light weight to keep the

The stomate open.

^^^^ ^g^ ^^ contact. lu fifteen or twenty minutes open and examine. The paper next

FIG. 135.

the underside

under the

of the geranium leaf is red where it lies The paper cm the upper side is only

leaf.

The greater

slightly reddened.

loss of water,

through the underside of the geranium

many

true of a great

make

But

will show.

Why

do

underside?

many You

leaves, as tests it

is

then, is

This

leaf.

is

which you can

not true of

all.

leaves lose more water through the will

not be able to see with your

eyes the mechanism in the leaf by which

it

can, to

some extent, control the escape of the water vapor. It is too tiny.

It

can only be seen by using a micro-

scope to look through pieces of the skin, or epidermis, of the leaf

which we can

strip ofE.

just as well for the present it

made from

the leaf.

through the epidermis.

if

Fig.

Perhaps

it

will be

you look at a picture 134 shows

little

of

holes

These open into spaces between

HOW PLANTS the cells inside the crescent,

if

leaf.

GIVE OFF WATEE

Two

cells,

101

each shaped like a

you take a surface view,

fit

in such a

around the opening that they stand guard over call

them guard

cells

little

some

"We

are filled tightly

with water and press back against the other keep the

it.

cells.

During the day the guard

lose

way

cells

and

At night they

holes {stomates) open.

of their water, so they are not so tight.

They then

collapse a

little,

so that

come together and The water vapor cannot escape so fast when the stomates

their inner edges

close the opening.

are closed.

On

very sunny days during dry

weather,

if

the roots cannot give the

plant enough water, the guard cells lose

some

of their water, so that they

m

ae^ir spaces the leaf can aisote seen.

'^°{a^^\

close up and prevent such a large escape would take place should they remain open.

of

water as

Is this

not

a good arrangement which the leaf has to prevent the Someloss of too much water during dry weather? times, however, the ground gets so dry that the roots

cannot get enough water for the plant. then wilt, and sometimes Leaves help to

lift

The

plants

die.

water in the plant.

As

the water

evaporates or transpires from the surface of the leaves more water is drawn up into the leaf to take its place.

THE WOEK OF PLANTS

102 This work

The

is

leaf, then,

done by the can help

lift

tiny

the leaf.

of

cells

water in the plant.

This

can be well shown by the experiment in Fig. 137.

A

leafy shoot of coleus, geranium, or other plant

cut,

is

and connected by a short piece of rubber tubing to one

end of a bent, or U,

tube which has been

filled

with water so that the end of the cut shoot

in con-

is

The

tact with the water.

rubber tube must be tied tightly

and

both to the shoot

to the

glass

tube,

so

in.

As

that air cannot get the

water transpires from

the leaf

drawn from that

arm

it

this Showing that the leaf can water in tlie stem as it is given

137.

raise

off at

the surface.

tube so

the

lowers in the other

of the tube.

water Fig.

gradually

is

it'

is

nearly

When the all

arm, mercury

poured

in,

and

out of

may

be

after a time

the mercury will be lifted

higher in the arm of the tube which the plant than in the other.

is

Mercury

connected with is

a great deal

heavier than water, so the leaves can do some pretty

hard work in

lifting.

HOW PLANTS Can the

roots take the

than the leaves can give

ment

to

GIVE OFF

it

show the power

WATER

103

water into the plant faster off?

Here

is

a pretty experi-

of root absorption.

Young

wheat plants growing in a pot will show it clearly if

the pot

is

covered with

a fruit jar and the roots are kept

warm.

shows how done.

If

it

Fig.

this

138

can be

not sum-

is

mer time, when the soil in the pot would be quite

warm enough, may be set in

the

pot

a broad

pan of wet moss or sawdust,

and here covered ^^i

with

the

fruit jar.

A

flame from a spirit lamp

may be set so that it will warm the edge of the pan, but the

soil in

the pot

138. The roots are lifting more water into the plant than can be given otf in

Fig.

the form of water vapor, so

it is

pressed

out in drops. must not be allowed to In a few hours or a day the leaves will get hot. appear beaded with the drops of water which are

pressed out.

There are

little

holes on the edge of

the leaf through which the water escapes.

water stomates.

These are

THE WOEK OE PLANTS

104

This condition of things sometimes happens at night

when

the

soil is

warm and

the air

damp and

cool, so

that the green leaves cannot transpire rapidly.

We

then, that root pressure exceeds transpiration.

Wheji a

plant

ivilts

the roots .in the

on a hot, dry day,

can

dry

lift

soil.

it is

say,

transpiring faster than

up water, because

there is so little water

now

exceeds root pressure.

Transpiration

CHAPTER XIV THE WATER PATH IN PLANTS

How

to determine the

through the plant.

You may

way.

by which,

so

some garden-balsam

plants, or the

are very good ones for the of

begonia

flows

in a very easy

wild Impatiens or jewel weed, or similar plants.

shoots

inter-

may be shown

These

cut

You will be much water

water path.

ested to find the paths

purpose.

Cut

also

These

some

or

other plant with white flowers. If there are corn

plants or wheat plants

half

some

grown

at

hand,

of these should be

Use also some good bleached celery leaves cut from a bunch. used.

Fig.

139.

Shoots of garden balsam, begonia, in colored solution.

and pea,

Set these shoots in a vessel containing red ink.

be

made by

Or

if

preferred a red dye can

dissolving one of the red "

diamond dyes

"

In a few hours, sometimes, the plants will show the red color in the leaves, or in the white petals. At least in a day they will begin to show the red color. in water.

105

THE WORK OF PLANTS

106

There are several distinct water paths in the shoot.

shows us in a very clear way that the red dye is taken up along with the water and stains

Tliis

i

In the garden balsam or the

the plant.

we can sometimes

jewel weed

These mark the paths through

outside.

which the water seen

I

if

in two.

we

are better

cut one of these colored shoots

In the cut shoot they will show

where the colored

In splitting the stem

water has passed.

If

They

flows.

as small round red spots

III

red

shoot by looking at the

the

streaks in

see

I

of stem of garden

they would appear as long red streaks or In these bundles there are tiny bundles.

balsam. The colored tracts show

tuoes or vessBls, througk

outside^ of

flows.

Fig.

140.

Portion

..

the

^

^

Therefore

^

we

^

.

_

_

which

call the

the

loater

water paths

in plants vascular bundles.

The arrangement

of the vascular bundles.

In cutting across the shoot of the garden balsam, or coleus, or begonia, you will see that these bundles have a regular arrange-

They

ment.

are in the

form

These plants are annuals, that ,

only one year, 1

m

•

rrn

ihere

i_i

bundles in them,

stump

of

will see

•

TJ?

it

is

1

of a ring. is,

they

1

live »

.

but one ring oi

11 you look

J

at

j_i

the

cut end stem showing where the water

fig. i«. of

patlis are located.

an oak tree or at the end of a

many

rings.

log, you Each year the bundle grows in

THE WATER PATH IN PLANTS

107

an outward direction as the tree becomes larger. The vessels formed in the bundle in spring and early summer are larger than those formed in

late

summer.

When

cut

across in the tree these vessels

look like pores.

As

bundles in the tree side

by

side,

all

the close

lie

the larger pores

formed in the spring alternate each year with the smaller Cross section of oak, show ing annual rings.

Fig. 142.

One each usually made

ones and form a ring. ring

is

year as the oak tree grows, so that the approximate age of the tree can be told from the number of the rings.

The vascular bundles

in a corn stem.

If a young cornstalk was The red ink, cut it across.

in the red

spots

which

the position of the bundles are

mark

arranged irregularly.

growing cornstalk

is

If

a fresh-

not at hand, take

an old dried one. With a knife cut around and just through the outer hard

Fig. 143. Vascular bundles of corn stem

Then gently break it, pulling apart the two ends at the same time. As it breaks, the bundles puU out as stifE layer.

pith,

and

in this

way

("where

tlie

"water

paths are located).

strings in the

the irregular arrangement

is

easily

THE WOEK OF PLANTS

108

A

seen. also,

palm shows that

section of the stem of a

here,

the vascular bundles are arranged irregularly.

Plants with netted-veined leaves usually have ,the vascular bundles plants with

arranged regularly in rings, while usually have the

leaves

parallel-veined

vascular bundles arranged irregu-

Compare the arrangementon the leaves of the

larly.

of the veins

garden balsam, coleus, begonia, sunflower, oak,

bean, pea,

with

arrangement

the

The

vascular bundles. netted-veined, Fig. 144. Cross section of palm stem. There are no annual rings.

of

etc.,

the

leaves are

and the bundles are

Compare the

in regular rings.

veins in a lily leaf or in a blade

with the arrangement of

of corn, wheat, oat, or grass

The

the bundles.

that the bean, pea, oak, seedling,

What

and the remember

leaves are parallel-veined,

bundles are arranged irregularly. etc.,

You

will

have two cotyledons in the

and that the corn has only one. kind of venation in the leaves, and what

arrangement of the vascular bundles are usually found in plants with

cotyledon

caUed

?

?

two cotyledons

What

are these

?

In plants with a single

two large groups of plants

CHAPTER XV THE LIVING PLANT FORMS STARCH All OUT starch is formed

the essential foods of also

plants.

man and

Starch

or

occurs in

It

vegetables and other plant foods which

is

nearly or quite pure

made by of ways for

is

formed,

is

stored in

plants.

food,

The

plants use

and much of

some part

tuber, for instance,

is

All this

starch.

it,

it

in

a

after being

of the plant for future

use, as in certain seeds, roots, or tubers.

The potato

largely composed of starch.

Tincture of iodine colors starch blue.

wet or moist with water

A

manu-

Prepared starch, like cornstarch, used for

eat.

variety

in the

It is

dressing of numerous useful articles.

many

puddings, starch

one of

is

other animals.

employed in many useful processes

facture

we

by

it is

When

colored blue

starch

by

is

iodine.

tincture of iodine can be obtained

from the drug

may

be dissolved in

store, or

alcohol.

much

a few crystals of iodine

In a test tube place a small quantity (as

as can be held

starch,

on the point of a penknife) of corn-

which can be obtained

at the grocery.

Pour

water into the test tube to a height of two inches. Hold the test tube over a flame for a few minutes to 109

THE WORK OF PLANTS

110

warm

tlie

water so

tliat

the starch will be well wetted.

Now cool it by moving the end of or

by holding

Add

it

in

the tube in cold water,

running cold water from a hydrant.

a few drops of the tincture of iodine.

The

liquid

immediately appears blue because the

numerous

starch grains are colored

blue by

Now hold the

it.

end of the tube over the

few

flame again for a

minutes, but do not let get hot.

The blue

disappears,

warm water iodine

it

color

because

the

extracts the

from the

starch.

Cool the tube again and the blue color reappears.

To test the starch Cornstarch dissolved in water, and tincture of iodine added. At left the solution is cold, middle one is heated

Fig.

145.

slightly, at right it is cooled.

potatO tuber.

Cut a pOtatO

(Irish potato) in tWO, -

in a

and

„

on the cut suriace scrape

some

of the potato into a pulp with a knife.

some

of the tincture of iodine to the potato pulp.

Apply It

The potato, then, is largely made up of starch. Place some of the pulp in water in a test tube, and add a few drops of the tincture of iodine. Then becomes

heat

it

blue.

gently to see

if

it

behaves like the cornstarch.

THE

LIVIISTG

PLANT FOEMS STARCH

Test for starch in Indian corn.

111

Split a kernel of

Indian corn and scrape out some of the endosperm or meat. test

Place

it

in water

and

What

the

with iodine.

is

Test grains of sweet

result?

corn in the same way.

What

The starch the sweet corn was changed is

the result

?

in to

sugar and stored in the seed in the forrp of sugar. Variegated leaf of grass

Fis. 146.

beet

is

The sugar

a rBservoir for food.

It is

it.. not stored as starch but as sugar.

(white and green).

,

Starch formed in green leaves.

leaves

Take a few green which have been in

sunlight through the

the

Immerse them

day.

over-

night in a strong solution of chloral hydrate in the

proportion of five ounces of chloral hydrate^ to one-

half a tumbler of

water.

This will remove the green color

and the leaves become Fig.

147.

Variegated leaf of aoutilon.

ten ounces for Chloral hydrate can be obtained at the drug store, hydrate to chloral grams eight about one dollar. More accurately, use •

5

o.c.

of -water.

THE WOEK OF PLANTS

112

Rinse the leaves for a

pale.

Then

place

them

moment

made by disIn a few moments the

in a tincture of iodine

solving iodine crystals in alcohol.

become dark purple-brown

leaves

in fresh, water. ^

in color,

sometimes

nearly black, with a more or less blue or purplish tinge.

This

is

the color given to starch

when it

The experiment shows us that starch

takes

up

iodine.

present in the

is

green leaves which have been for some time in the light.

But

if

we

should keep the plant in the dark for a

day or two, and then

test

find

some

of the leaves

we should

no starch present.

Where starch

is

formed in the

variegated leaves of the coleus plant.

The

leaf

of

the coleus

variegated, that colors.

is, it

plant

In this one which we are

to study, part of the leaf

and part

is

has difEerent

is

is

green

white, the green occupy-

ing the middle portion and the borFig.

148.

Variegated leaf of

coleus plant, in fresh con-

der,

while the white forms a V.

figure between.

We

wish to know

dition.

which part

We

will

of the leaf forms starch.

immerse some of these variegated leaves in the

strong solution of chloral hydrate overnight. 1

The

Now they

tincture of iodine can be purchased at the drug store.

one-quarter ounce of the crystals of iodine

placed in alcohol as needed.

may be

Or

purchased and a few

THE LIVING PLANT FORMS STAECH

113

are almost entirely white, the chlorophyll having been

We v?ill rinse them a moment in water and then place them in the tincture of iodine. Those removed.

which were

portions

now

green

are

quite dark, while the V-shaped

figure,

or

that

part which

was

white, remains white in the iodine or does not take the dark color.

The green part of the leaf, then, forms starch. We have now learned that the leaf -green as well as sim-

make starch. make starch nor can the light make

light is necessary to

The

leaf-green cannot

in the dark,

riG.

149.

Similar leaf after

green color is removed and treated with iodine to show

starch in portions of a leaf which

location of starch.

have no leaf-green. Starch is formed in the green leaf during the day, but

what becomes

of it at night ?

In the afternoon

cover a part of a leaf in such a light

from that

spot.

way

Take two

let

us

as to shut out the

corks, place one

on

either side of the leaf, covering a small circular portion,

and thrust two pins through the edge pin

it

fast to the other.

we know

From

our former experiments

that at this time of day

leaf contain

of one cork to

all

parts of the green

starch, so that the part covered

corks, as well as the uncovered portion, starch.

now

On the following day at noon, or

by the contains in

the

THE WOEK OF PLANTS

114 afternoon,

we

and immerse solution to it

will take this it

same

remove the green

and place

it

leaf,

remove the

corks,

overnight in the strong chloral -hydrate

Now we

color.

will rinse

The part of the leaf which was

in the tincture of iodine.

by

covered

corks

the

does not show the starch reaction, while

parts of the

the other

So

leaf do.

must

it

be that the starch piG.

150.

Pumpkin

leaf covered to

leaves

;

at

left portion of

keep out sunliglit at right same no starch where leaf was

.

;

leaf treated with iodine,

covered.

,

i.x^

nCW was made m ,

±.

at nigllt, tliat ,

i

starch

t

the parts exposed to the light, and that no starch

formed in the part covered from the

When it

go?

dis-

appeared f rom the leaf >

was

light.

the starch disappears from the leaf where does Is

it

found in other parts of the plant not

exposed to the light?

where does

it

starch stored

How

does

it

get there, and

come from? For what purpose up in reservoirs?

is

the

CHAPTER XVI THE WORK DONE BY PLANTS IN MAKING STARCH Plants do work.

yet

it is

seems strange that plants work

It

Some

quite true.

work, and hard work

plants do a great deal of

Plants work when they make starch, though, as we have seen, they cannot do this work without the help of light.. But light, without the leaf-green and the living plant, cannot make starch.

We

cannot see the work which the green

plant does, but tell

that the

too.

easy to see some of the signs which

it is

work

is

We must

going on.

learn to read

the sign language.

How

water plants

some water weeds, is

the elodea, but

may

or leafy plants

A very good

lakes, or streams.

work.

tell of this

when

this

Let us select

which grow

in ponds,

plant for this purpose

cannot be found others

be obtained which will serve quite as well.

plants

may

bottle of water

which

is set in

the window, so that they

will get the sunlight, or the brightest light

be had

if

The

be brought to the room and placed in a

the day

is

cloudy.

which may

In a very short time

bubbles of gas collect on the leaves, small ones at

but increasing in

size until

they are freed.

115

first,

Then they

THE WOEK OE PLANTS

116 rise to

Some

the surface of the water.

of the plants

should be placed in an inverted position in the bottle so that the cut end of the shoot will be below the surface.

From

this cut

end of the shoot bubbles

of the gas come out more rapidly than

from the is

leaves.

Most

of the gas,

came from the

true,

leaves,

it

but

there are air spaces all through the

plant between the

gas which

is

cells,

so that the

formed in the leaves can

pass out not only at tiny openings in

the

leaf,

but also through the connect-

ing spaces in the stems.

The more the

work

light there is the faster

goes on.

If the bottles con-

taining these water plants are kept in

the is Fig. 151. The " tell-tale bubbles rising from a

window

for several days,

and there

cloudy weather as well as sunshine,

','

water plant.

you

will notice that the bubbles of gas

come out more rapidly on a sunshiny

The more, light there is, more work the plant can do. This can be Remove the bottle from the wintold in another way. dow and put it in a poorly lighted corner of the room. The gas is given off more slowly. Gover the bottle day than on a cloudy one.

then, the

with dark cloth to shut out minutes uncover

it.

all light.

The escape

In ten or fifteen

of the gas has ceased.

WOEK DONE

MAKING STAECH

IN

117

Now

place it in the brightly lighted window again. The bubbles soon start up afresh. Do the "pond scums" do the same kind of work? Many of you have seen the green-looking " scum," as some people call it, which floats on the surface of ponds or on the water of ditches,

and which

the spring and autumn.

This pond scum deserves a

better name, for

really

it is

made up

abundant in

so

is

of beautiful tiny

which we

plants, often consisting of silk-like threads,

can see by that

it

lifting a bit of it

from the water.

work

does the same kind of

plant, place

some in a

window by the

bottle of water

have perhaps noticed that

this

on the water, has a great

many

bubbles in

and then replace it

If

all it

Now

tell-tale

you as

it

you take up

of this tangle, rinse

water to remove

set it in the

The

caught in the

it,

tangle of threads.

some

and

pond scum,

floats

see

as the leafy water

side of the other plants.

bubbles show themselves here also.

To

it

in the

the bubbles,

in the water;

does not float well, but tends to

sink to the bottom.

But when the

bubbles of gas begin to form again c? ^ ^ and are caught in the meshes of the tangle, they are so

much

they buoy up the plant and

JP'ig-ib2.

Bubwes

pond scum

rising

from

in sunligtt.

lighter than water that lift

it

once more to the

THE WORK OF PLANTS

118

Here the plant can get more

surface of the water.

more

and

air,

The leaves

so do

more work

of various kinds.

and shrubs,

of garden herbs

light,

trees,

But

land plants do the same kind of work.

and other

since they do

not grow in water they do not show the signs of this

work

At

as water plants do.

signs of

it

because the gas

is

we cannot see the much like the air in its

least,

so

Perhaps you have put a lettuce leaf or a

nature.

leaf

some other land plant under water, and have been

of

told that the bubbles

which

rise

water are a sign that the leaf

But

making.

given

off

from the

leaf in the

doing work in starch-

this brings the land plant into

vorable environment, and

bubbles given

is

off are of

by the water

it

soon

an unfa-

Not

dies.

all

the

the same kind of gas as that plant,

that this

so

must be

regarded as a misleading experiment.-' 1

When

the leaf of a land plant

is

placed in water there

a thin layer of air over the surface of the

exposed to the sunlight, there

is

a

rise in the

This

inside the leaf ture.

This air

may

is

always

If the water

is

temperature which causes

the air around the leaf to expand, and some of bubbles.

leaf.

it rises

continue for a considerable time.

in the form of

Some of the

air

crowded out because of the change in temperathat is rising from the leaf because of the change in

is

also

is not the same kind of gas that rises from the water plant from the pond scum. We cannot distinguish between the two kinds of gas as they rise together from the land plant in the water. Therefore it is no sign that the plant is doing the work, but only an evidence that a change in temperature is going on which expands the air and causes some of it to be freed from the surface of the leaf. The same thing can be seen if we place a piece of broken crockery or a dry

temperature or

WORK DONE What

IN MAKING STAECH

use the plant makes of starch.

so necessary to plants,

we ought

uses

which the plant makes

new

life

of

to

only because more

life

Since starch

know some It helps to

it.

This

substance in the plant. substance

is

119

is

is

of the

make

necessary, not

needed as the plant

becomes larger, but because, in one kind of work which the plant does, some of the

substance

life

is

consumed.

We

must understand that when the starch helps to form new life substance it no longer exists as starch but is assimilated along with other foods which the root takes

The making of starch is not the making of the life It must he assimilated with the other food substance. up.

substances taken

water plant

up by

from

the

the root

from

the soil, or

by the

water, before living rnaterial

is

m,ade.

When we

eat solid food substances they are acted

on by certain

juices of the

mouth, stomach, and other

organs.

A

solved.

These food solutions are then absorbed through

part of the food

is

thus digested and

dis-

the surface of the large intestine, where they enter the blood. all

In the blood vessels they are finally carried to

parts of the body, where they

the living matter.

The

come

digested food

is

in contact with

now assimilated

and then set the vessel in the light. To show do the same kind of work which the water plants indicate by the bubble sign would be too difficult an experiment for piece of

wood

in water,

clearly that land plants

young persons.

THE WOEK OF PLANTS

120

and helps to make new living matter to replace that which has been used up in growth or work.

The

case with the plants

their structure, of course,

made

in the green leaf

is is

somewhat similar, though very different. The starch

is

the solid food, though

not taken in by the plant in that form.

It

it is

must be

by the action of a juice (a ferment) in the Here it meets other food substances absorbed by the roots. Then by a process of assimilation similar to that which digested and changed to a form of sugar life

takes place in our

own

bodies,

substance.

new

living material

is

made. So while plants and animals get their food by ent methods, and in different forms, into living material in the

stance of plants

animals.

is

it is

same way.

the same as the

life

finally

The

differ-

made

life sub-

substance of

CHAPTER XVII THE KIND OF GAS WHICH PLANTS GIVE OFF WHILE MAKING STARCH

How

to catch this gas in a tube.

to learn

what of

more

We

some

plant. jar

if

possible,

can catch some

will take the elodea

other

Place

suitable

it

water

wide

in a tall,

and invert a funnel over small

that the

so

are interested

in a tube in the following

it

way. or

We

it is.

We

and to know,

of this gas,

it

end of the

funnel will be under the surface of the water.

Sink a test tube

in the water,

and then, without

bringing the open

end of the

tube out of the water, invert

and lower

it

it

over the end of the

funnel as shown in Fig. 153.

Set

the jar in the sunlight and leave it

there for several days, arrang-

ing

something

the tube in case

to hold it

down

becomes 121

Fig. 153.

CatoUng the bubbles

of gas in a test tube.

full of the

buoyant gas.

THE WOEK OF PLANTS

122

The gas now, rises it

through

as

tlie

it is

given

off

from the water

plant,

funnel and into the test tube where

accumulates in the upper end and gradually displaces

the water.

In several days so

lated that perhaps the tube

water.

How

We

now

are

is

much

gas has accumu-

full of it

and empty

of

ready to test for the kind of gas.

to test for the gas.

We

wish

glowing splinter into the end of the

now

to bring a

test tube before

the gas escapes, and without wetting the splinter in

We

water.

light

a long, soft pine

and hold

splinter it

in

one

hand,

while with the other we grasp the upper end of the test tube, which

should be freed

if

was tied down. Blow out the flame on the splinter,

it

leaving

the

glowing. Via. 154.

Eeady

to see

what the gas

is.

lift

coal

Quickly

the tube from

the water and thrust the glowing end of the splinter

The we know that the oxygen

into the test tube. is

oxygen, for

It flames again

!

gas, then, of the air

GAS WHICH PLANTS GIVE OFF necessary in

is

making a

so that

fire

it

123

consume

will

the wood, or coal, or other material.

The reason the glowing the air

enough

to

But there

ignite

is

not great

it.

much

so

is

oxygen caught test tube

splinter does not flame in

because the proportion of oxygen

is

in the

from the plant

that the glowing coal

Fig.

ISS.

The splmter lights again presence of oxygen gas.

m the

readily flames again.

How just

is

the gas formed ?

how this

gas

of chemistry

is

It is difficult to

formed, for a considerable knowledge

necessary to understand

is

show here

it

thoroughly.

But perhaps you have learned about some of the chemical compounds, as they are called, and how they sometimes change their combinations and associations. let

plant in off.

When

us boil some water. it

This

and is

off,

and which

and carbonic

acid.^

If

we

1

since

The carbon dioxid

in water.

it is

can

givfn

But

it

which the

set free.

This was

introduce air and carbon

will soon be given off again

now

here in the

is

necessary for the plant

oxygen may be

dioxid into the water, oxygen

by the plant,

in the water

is

First

put a water

No gas you may say.

queer behavior,

in order that the air

is cool,

set it in the sunlight.

shows us that something was boiling drove

it

absorb carbonic acid. form of carbonic

acid, since it ia

THE WOEK OF PLANTS

124

How

In the case of

this takes place in land plants.

land plants, the leaves of which are surrounded with air,

You

not water, the plant absorbs carbon dioxid.

perhaps have been told that the parts of

tiventy-one,

djrifgen gas,

air consists of

about

seventy-nine parts of

rtxtxogen gas, and a very small fraction of carhon-dioxid

The carbon-dioxid constituent

gas.

pound

that

;

There

is, it is

composed

of

is

a chemical com-

two elements united.

one part of carbon and there are tioo parts

is

of oxygen, and

it

The carbons

written thus, CO2.

is

and oxygens hold on to each other very so soon as they

come

take up some of explains

how

tightly, but

in contact with water they quickly

it

and form carbonic

This

acid.

the carbon dioxid in the air for the land

plants becomes carbonic acid in the water for water plants.

Water

is

a

compound composed

p^ts, and oxygen, one part, and thus, H2O.

the air

is

As

its

of hydrogen,

symbol

absorbed by the leaves of the land plants

and forms immediately carbonic it

dissolves in the water

The symbol

plants.

to

it

in their cells,

acid, just as it does

which surrounds water

of the carbonic acid

then

is

CH2O3,

compounds there is one part of carevery two parts of hydrogen and three parts of

since in the united

bon

tivo

written

soon, however, as the carbon dioxid of

comes into direct contact with the water

when

is

oxygen.

GAS WHICH PLANTS GIVE OFF

125

Now the carbon, hydrogen, and oxygen in the carbonic acid do not hold on to each other very tightly. When they get into the green of the leaf and the sunlight flashes in,

hurry to

them apart very easily, and they form new associations or compounds which it

drives

the sunlight cannot break.

hurry

so,

that the

permanent

;

new

Perhaps

it is

associations they

because they

make

are not

at all events these are soon broken

and

others formed, until finally the elements unite in such

a

way

as to

form sugar

this sugar is CeHiaOg.

in the leaf.

To

get this

The symbol for it was necessary

for six parts of the carbonic acid to combine.

would take

all

of the carbon

and

This

of the hydro-

all

gen, but there would be twelve parts of oxygen left over.

This oxygen

amount

is

then

of carbonic acid

set free.

which

is

From

broken up in the

leaf under these conditions, a considerable

oxygen would be

left

After the sugar

is

goes out of for starch.

it,

the great

amount

of

over and set free from the plant.

formed, one part of water (HgO)

leaving CgHioOg, which

is

the symbol

CHAPTER XVIII HOW PLANTS BREATHE Do plants breathe ?

But

Yes.

if

plants do not have

we do, how can they breathe ? There many animals which do not have lungs, as

lungs as

starfish,

the oyster, the

they breathe. respiration.

worm,

etc.,

Breathing in animals

So in plants breathing

is

are

the

and yet

we

call

respiration.

Soak a

Respiration in germinating seeds.

handful of peas for twenty-four hours in water.

Remove them from

the water and put

them

in

Cork tightly

a bottle or a fruit jar.

or cover with a piece of glass, the

underside of which

is

cemented to

mouth of the jar with vaseline to make it air-tight. Keep it in a moderately warm room for twentyfour hours. Keep an empty bottle covered in the same way. Light a the

taper or a splinter, and as the cover is Fig. 156. Peas germinating in a closed jar.

is

extinguished,

removed from the

jar thrust the

lighted end into the jar.

Now light the taper 126

The flame

again, uncover the

HOW PLANTS BEEATHE empty into

bottle

it.

and thrust the lighted end

The flame

gas, carbon dioxid,

given

is

in the jar, so

of the taper

A

not extinguished.

was

in the first jar.

by the germinating

off

127

much

it

This gas

is

Being confined

peas.

of

suffocating

accumulated that

it

smothered the flame. Lime-water

baryta-water

or

a test for

is

Make some

carbon-dioxid gas.

lime-water by dissolving lime in

I

water and allowing

Baryta-water

Make a hydrate.

is

it

saturated solution or allow

Filter;

and then pour

of it

barium

to settle,

the clear liquid.

off

should be kept corked

Take some

to settle.

even better.

when not

in a shallow vessel.

It

in use.

Open

the jar containing the germinating peas

and pour from

it

some

of the carbon-

dioxid gas into the baryta-water. Fig.

157.

Tlie light

smothered in

is

carbon-dioxid gas

the gas given off

by

germinating

is

(The

heavier than air and

downward when the jar Cover the jar again. Imme-

therefore flows

peas.

is

tipped.)

diately on pouring the carbon dioxid into the baryta-

water, a white substance 1

if

Barium carbonate,

lime-water

is

used.

if

-^

is

formed.

baryta-water

Lime-water

is

is

Chemists

us

used, or calcium carbonate,

easier to obtain,

are not so striking as with barytarwater.

tell

To make

but the results lime-water, take

THE WORK OF PLANTS

128

that this white substance

is

formed by the union of

Pour some of the

carbon dioxid and baryta-water. baryta-water

down

the sides of the jar and on the peas.

Notice the white substance which

is

formed.

Take some of the fresh baryta-water and breathe upon it. This

Carbon dioxid from our breath. lime-water or

same white

precipitate

is

formed, because there

is

a quantity of the carbon dioxid exhaled from our lungs as

we

breathe.

It is interesting to

agreement between plant

life

show

and animal

this close

life.

Plants take in oxygen gas while they breathe. require

oxygen in the process

So far as the movement of the gases

animals do. concerned,

Plants

of respiration just as

respiration

consists

is

the taking in of

in

oxygen gas into the plant or animal body, and the giving

off of

carbon dioxid.

To show that oxygen from the

Soak some wheat

plants breathe. in water.

the folds

Let

Remove of damp

remain until

it

it

air is

used up while

for twenty-four hours

from the water and place

it

in

cloth or paper in a moist vessel. it

begins to germinate.

Fill the

bulb of a thistle tube with the germinating wheat.

By

the aid of a stand and clamp, support the tube upright, a

lump

of lime twice the size of a hen's egg

of water.

AUow

and in a day

and put

it

in a quart

two pour off the clear liquid cork in a bottle before using. The white substance formed when lime-water is used is due to the union of the lime-water and the carbon dioxid. I

it

to settle

or

HOW shown

as

PLAJSTTS

BREATHE

129

Let the small end of the tube

in Fig. 158.

rest in a strong solution of caustic potash (one stick

caustic potash in two-thirds tumbler of water) to

which

red ink has been added to give a deep red color.

Place a small glass plate over the rim of the bulb and seal it air-tight with an abundance

Two tubes

of vaseline. set

up

can be

in one vessel, or a second

one can be

set

baryta -water

up

strong

in

colored

in

the

same way. The

result.

You

will see that

the solution of caustic potash rises

The

slowly in the tube.

barytarwater wiU also,

if

that

The solution is colored so that you can plainly see it rise in the tube, even if you are is

used.

at a little distance

from

it.

In

Fig. 158. Apparatus to show " breathing " of germinating

the experiment the solution in six hours

had

risen to the height

In twenty-four hours

it

had

wheat.

shown

in Fig. 158.

risen to the height

shown

in Fig. 159.

Why

the solution of caustic potash rises in the tube.

Since no air can get into the thistle tube from above

or below, is

inside

it

must be that some part

the

tube

is

of the air

which

used up while the wheat

is

130

THE WORK OF PLANTS

germinating.

From our study

know

of germinating peas

we

given

off

that a suffocating gas, carbon dioxid,

The

while they breathe.

baryta-water, whichever

is

caustic potash solution or the

used, absorbs the carbon

is

The carbon dioxid is heavier than air, and so settles down in the tube, where it can ___^^^__

dioxid.

^"'.^

be absorbed.

IT

Where does the carbon dioxid come from? We know it comes from the

^

You

growing seedlings.

breathing,

remember that the symbol for The carbon carbon dioxid is CO2.

will

comes from the plant, because there is

not enough in the

air.

The

nitro-

not join with the

gen of the

air could

carbon to

make CO2

;

so

it

must be

that some of the oxygen of the air joins with the carbon of the plant. FIG.

159.

The same

later,

ygg,

it

absorbed by the plant.

doeS

;

When

but the OXygeU it

association with the living substance

join the oxygen,

away from

and hurries

and together they escape into the

When plants breathe fast they are From what we have just learned we the living plant

substance

while the plant breathes.

is

firSt

gets into the living

plant substance, some of the carbon breaks its

is

to

air.

doing more work. see that

some

of

used up or consumed

When

a

fire

burns, oxygen

HOW PLANTS BEEATHE is

taken from the

wood

and

air

131

joins with carbon in the

or in the coal, and carbon dioxid

This joining of oxygen and carbon

is

is

set free.

called oxidation.

In the living plant the joining of the oxygen from the air

with the carbon in the plant takes place slowly, so

that no flame or

made, but

fire is

it is still

oxidation.

Oxidation takes place slowly in animals in the same

way when they

But while the plant

are breathing.

being partly oxidized or consumed as

very thing enables

and in other ways.

to

it

When you of your

to get

power or energy

to play

play

one kind of work.

is

is

breathes, this

do more work, in growth

A part

breathe faster.

it

run or play hard, you

body must be oxidized ;

or to

work

either, for

The carbon dioxid which is given off is one form of the waste from your body, or from the plant's body, while work of this kind is going on. To take the place of this waste you must eat, and you know how hungry you are when you are growing and playing. You need a great deal of food to

make new

living materials to

take the place of the waste, and to supply what

needed for growth.

So

it

is

with plants

food for growth, and to repair waste.

;

is

they need

Part

III

THE BEHAVIOE OF PLANTS CHAPTER XIX THE SENSITIVE PLANT

One

of

the most interesting manifestations

joi

life

movement of the leaves in the The plant so-called sensitive plant {Mimosa pudica). may be easily grown from the seed in pots, either in a in plants

is

the rapid

Fig. 160.

Leaf of sensitive plant.

greenhouse or in the window of a room, tected from the hot rays of the sun. in late spring will bring forth

use in late

summer

it

is

pro-

The seed planted

good plants ready for

or during the autumn. 132

if

THE SENSITIVE PLANT The

Appearance of the sensitive plant.

A

the sensitive plant are rather large.

posed of a large number of

A

com-

leaf is

arranged

as the toes of

single leaf

160 attached to the shoot.

of

which are joined to

somewhat

leaf)

a bird are joined at the foot. in Fig.

leaves

leaflets (pinnce)

in pairs along four different axes,

a stalk (the petiole of the

133

is

shown

Imagine

a branched shoot with a number of these leaves and

you

will

know how

the sensitive

plant looks.

Movement plant.

of the leaves of the sensitive

When you

wish to

test the plant, it

should be on a bright day, though the plant will

work on a cloudy day

too dark. quiet for

It

must be

left

some time before

also

not

if it is

undisturbed and

We

using.

be careful not to touch or jar

it

must

until

we

are ready.

Movement of the leatlets after pinchmg one:

Pig. IGl.

Now, with a fingers, pinch

pair of forceps, or with the

one of the terminal

leaflets.

Instantly the terminal pair clasp or fold together above the axis.

Then the second

pair do the same,

third and fourth pairs follow quite

movement all

closed.

Then the

This

regularly.

continues, successive pairs closing

on the axis are

and the

up

last pairs

until

on the

other three axes fold together, and successive pairs on these close

up

until

all

are

closed.

By

this

time,

THE BEHAVIOR OF PLANTS

134

probably, the four axes which bear the leaflets are

The

closer together.

stalk of the leaf

is

drawn

also likely to

turn downward, and the entire leaf presents the appearance

When we was given

shown

pinched the

to the leaf

The

stimulus.

in Fig. 162.

leaflet,

what we

stimulus

there call

travels

through the leaf,

and

response it

in to

the move-

ment

takes

Fig. 162. Position of leaf after movement has ceased.

place.

If

we

jar

a sensi-

tive plant suddenly, all the

leaves close up

a

drooping

shown

and assume position,

as Fig. 163.

in Pig. 163.

The

sensitive plant

after jarring.

a

all

THE SENSITIVE PLANT

the leaves at night or on dark days.

Behavior of

On

a dark day the leaves of the sensitive plant are

folded together

;

or

we

if

take the plant into a poorly

lighted room, the leaves will close it

;

then

out to the light they will open again.

fall

135

if

we

bring

So at night-

the leaves fold together, and the sunlight of the

following day

is

necessary before they will open again.

This teaches us one of the influences which light exerts

on

plants.

This plant

is

very sensitive to contact with

other objects or to shock; but

we

see that

it is

also

sensitive to light, for the leaves will

open in a short

time when brought into the

The mimosa

called^

light.

the sensitive plant because stimulus

to

contact

all

plants are

more

so than others.

or shock.

it

responds so quickly

In

or less sensitive,

This

we

is

reality,

however,

some being more

can readily see

the relation of other plants to the light.

by observing

CHAPTER XX THE BEHAVIOR OF PLANTS TOWARD LIGHT Compare plant stems grown

When

grown in darkness. flower,

in sunlight

with those

planting seeds of the sun-

pumpkin, buckwheat, pea, wheat, or corn, place

some

of the pots

to exclude the light.

etc.,

under tight boxes

The

pots should be

covered as soon as the seeds are planted so that no light will reach the young seedlings.

They should remain covered for two or three weeks or more. They can be safely uncovered ally,

occasion-

for a

few mo-

ments at a time, to supply the necessary

water and to compare

them with the

seed-

lings started at the Pumpkin

one at left grown in dark, one at right of same age grown in light.

Fig. 164.

seedlings

;

same

time,

in

the

light.

Observe the plants about twice each week.

measurements

of

the

growth; 136

sketch,

Make

and keep a

BEHAVIOR OF PLANTS TOWAED LIGHT record of the observations.

137

Do the stems grow more

rap'

Compare the leaves on the plants grown in the dark with those grown in the Compare the leaves of the light. wheat grown in the dark with those grown in the light. How does the wheat differ from the pumpkin, sunidly in the light or in the dark

?

flower, or similar plant in this respect

?

shows a

Fig. 164, left-hand plant,

pumpkin seedling grown in the dark. The right-hand plant in the same Fig. 165. Buckwheat seedlings grown in light. figure is another of the same age grown in the light. The stem grown in the dark is much longer than the one grown in the light.

week

old.

lings of

These plants are about one Fig.

166 represents seed-

buckwheat grown

in the

dark

they are longer than those of the same

age grown in the light.

Are the stems

grown

in

light

stouter and firmer?

In Fig.

166.

Buckwheat seedlings of same grown m aarK.

age,

comparing

the

in geedlingS o o grOWn

THE BEHAVIOR OF PLANTS

138

the dark with those there

grown

in the light

another striking difference be-

is

tween them which we cannot observe.

The stems grown

fail

to

in the dark

are longer, but they are less firm, and

they are not capable of supporting themselves so well as the stems

This

light.

is

well

grown

shown even

in the in the

week-old seedlings of the buckwheat, as seen in Fig. 166.

They cannot support

own

weight, but

fall o.ver

and hang

their

down by the pot.

This

also in Fig. is

marked 169, which

a later stage of the

pumpkin shown is

side of the is

seedling

in Fig. 164.

It

now three weeks old,

and has grown

all this

time in the dark.

To

support the stems they

were tied to a stake.

Those grown Fig.

167.

seedlii

dark.

Sunflower ;

grown

in

(Nat. size.l

Fio. 168. lings

suDflower seed-

grown

in

the

light are stouter

and

firmer and are able to

in dark, older

thaninFig.167. (Iteduoed.)

SUppOrt themSclveS. If

BEHAVIOR OF PLANTS TOWARD LIGHT we

we

crush these steins with the fingers,

139

find those

grown in the light firmer than those grown in the dark. A more accurate test would be to dry the plants thoroughly and then to weigh them. The plants grown in the light would outweigh those grown in the dark.

made more

In other words, they have

plant substance.

It will

remembered that be

green

plants

form starch in sunlight.

The

starch

of

in

it,

substance, walls,

used,

is

much

making new plant especially

cell

which constitute the

firmer portions of plants.

li^G. 169.

Same

seedlings

shown

in Fig. 164,

the reason, then,

This

is

why

the stems

l)nt older.

the dark are

and

less firm

than those grown in the

grown in more slender

light.

The leaves on plants grown in the dark. While stems grow less rapidly in light than in dark, light accelerates Plants grown in the dark the growth of the leaves. have very small or undeveloped leaves.

shown

in the

pumpkin

(Fig. 169).

This

Compare the

is

well

leaves

THE BEHAVIOE OF PLANTS

140

on the plant grown in the dark with those on the plant

grown

The

in the light.

plants are of the

same

age.

Light, then, increases the size of

the leaves of such plants as the

pumpkin, sunflower, buckwheat, etc.

How

is

it

with the wheat

and similar plants

?

Do the cotyledons

of the

pump-

kin or squash open in the dark ?

As the cotyledons of the pumpkin slip from the seed coats and are pulled out of the ground by the loop,

they are clasped tightly

together. Fig.

Sunflower seedlings grown in light, just covered to exclude light.

But

as

170.

they are straightening up in the

light

they spread apart and expand.

What

causes

them

to

open and expand ?

Let us cover some pumpkin seedlings

which have grown

in the light,

and in

which the cotyledons have just expanded.

The box should be

tight so that the seed-

lings will be kept in the dark.

Allow

them to remain here a day or two then remove the box sometime near mid-day. The cotyledons are clasped together and ;

erect, as in Fig. 171.

Now

leave

Pin.

Same seedafter being

171.

lings

covered two days.

them uncovered; the

BEHAVIOE OF

cotyledons open again.

when and

it is

we examine them

If

usually find

As the morning

erect.

The

again.

we

dark,

TOWARD LIGHT

PLAISTTS

141

at night

them clasped together

comes on they open then, must have an influence in

light,

light

spreading the cotyledons apart.

We

should

now

refer

our

to

observations on the squash seed-

grown

lings,

in the dark, or

if

we

did not then observe the cotyledons,

we

should at once examine

some seedlings

shown

of the

grown

squash,

pumpkin

the dark,

in

or as

in Fig. 164.

The

cotyle-

dons remain closed.

Fig.

169

is

the stem as

it

very interesting

;

,

grows

IS

obliged to push

its

"2. same seedlings after exposure to llglit again.

f».);?.

Troops of these more fortunate

creatures are scattered here and there.

Fia. 276. Seedling o£ white pine just coming up.

The struggle with other vegetation.

Now

begins a competition

among

the seedlings and

other plants for mastery of the position.

Weeds, grasses,

;

BATTLES OF PLANTS IN THE WOELD

226

vines, perhaps

the soil lific

is

young shrubs and oaks, spring up,

for

thick with the seeds of other plants as pro-

in seed-bearing as the pine.

Many

of these

grow

now than

faster

the pine seedlings.

The weeds and soon tower

grass

them and hide them. It above

looks as

if

the pine

seedlings would be

choked

out.

But

they can do

fairly

well in the shade

better, perhaps, than the weeds think,

if

they are

capable of

doing

such a thing. The. pine seedlings do

not hurry.

..^m^mm Fig. 277,

White-pine seedlings casting seed coats or

embryo

They

cases.

long roots.

The

They

They

'^^f'^*^""' bide their time. are

making

and useful

are preparing for a long struggle for

score after the first season.

us take count of the contest.

life.

In the autumn

The weeds raced

let

swiftly

THE STRUGGLES OF A WHITE PINE and got far ahead.

227

But they have exhausted them-

They have ripened many seeds, but they die leaves wither and dry up. This lets in more light

selves.

their

The autumn winds and on the dead weeds and break many of them The snow finishes many more. In the spring,

for the tiny pine seedlings.

rain beat

down.

Fig. 278.

^

Evergreens and broad-leaved trees just getting above the weeds and grass (Alabama).

when the snow lings

disappears,

had another chance.

it

looks as

If the

if

the

little seed-

winter was cold and

the ground bare for a part of the time, perhaps some

were frozen to death.

come and

go.

The second and

The weeds

flourish each year just as

They hide the tiny choke them out. The little befdre.

surely.

third seasons

pines, but trees

they cannot

grow slowly but

228

BATTLES OF PLANTS IN THE WORLD

Another enemy than weeds to struggle against. haps, in the

Fig. 279.

first

Per-

season, or the second, or the third,

Young white

pines getting a start. Tliree ages of pine trees are sliown (New York).

or even later, another foe appears

which pursues _dif'

ferent tactics from those of the weeds.

It is a tiny

THE STEUGGLES OP A WHITE PIKE

229

fungus, or mold, of delicate gossamer-like threads. is

make

apt to

Weather, just

inside.

Young

Fig. 280.

much soft,

of

it

that

and

dies.

to rot

and

was the

it

itself

It

wet

away and becomes thin and ground level. The little pine

shrinks

It topples over to the

up.

We

say

die

on account of the wet ground.

little

in

" bull pines " getting a start (Colorado).

and dead at the

cannot hold

on the seedlings

at the surface of the ground. The mold make little holes in the stem and They feed on the stem, dissolving so

threads of the

grow

attack

its

it

''

damps

oil,"

because

plant mold that killed

it.

it

ground appears

But

Though

it

the

230

BATTLES OF PLANTS IN THE WOELD

mold was very much smaller than the

pine,

made a

it

Many may fall

successful attack.

of the seedlings

from the attacks

of this

insidious foe.

The pines get

larger.

Each year those that remain get higher. They seem to make up in size what they have lost in number. They grow at a more rapid rate now and are beginning to outstrip and shade the weeds. The weeds and grass cannot endure the shade as well as the

little

pines

could.

As

the pines get higher

the branches

reach

and nearly cut light

off

out the

from the ground.

Finally

the

weeds

and

grass can no longer grow

underneath them.

The

few pines remaining have Fig. 281.

Four giant wliite pines (New York).

,

•

^

overcome the weeds.

THE STRUGGLES OP A WHITE PINE

231

Other competitors appear.

There were, perhaps, some acorns, or beechnuts, or the seeds of other trees in the ground. few of these got a start. Some may have

A

started before the pines did.

Fig. 282.

The pines have grown

Conifers overtopping broad-leaved trees in

out of the

way

of the

feared the weeds.

perhaps, while

tlie

weeds now.

They were etc.,

In

(New Hampshire),

fact,

they never

grateful for the shade,

they were young.

oaks and beeches, elms,

forest

are

Now

the

young

more sturdy and

BATTLES OF PLAINTS IN THE WOELD

232

They do not die at the end They grow larger and larger. During the summer their broad leaves make a great deal more shade than the Some of the pines get pine leaves do.

dangerous competitors. of the season.

covered and crowded as time goes on.

Some

of the smaller ones die.

This

renewed year

year.

struggle

One

is

after

foot, eighteen inches, or

two

feet,

the trees add to their height annually.

Their limbs reach out and interlock as if

in actual

physical struggle.

The

dense foliage on the upper branches cuts off Fig. 283. pines,

An enemy of shelving

a

die

spruce

hemlock.

away.

The

smooth trunks of trees appear

The lower

light below.

branches

"mushroom," growing from a

much

tall, fore^st

below the

ris-

ing tops, which get higher

and higher.

The smaller

trees die

and

ground.

It is a struggle

fall

to the Fig.

now between

the

taller

284.

wood

and taller

finer

pines

Spawn

in Fig. 283 as

it

of the "

malces

mushroom " shown way through the

its

of the tree.

and the

and sturdier oaks.

It is

a battle of giants, a

contest for the " survival of the

fi.ttest."

Here and

THE STEUGGLES OP A WHITE PINE

233

there between the round tops of the oak are clear views of the sky above. Through these openings the straight shaft, or " leader," of the pine shoots

rapid growth.

upward in

its

more

Soon the pines begin here and there

tower above the other

trees.

to

Their branches reach out

and elbow their way above the tops of the oaks. The pines have risen above the other trees of the forest and

Pig.

285.

Effects of fire in forest

hold almost undisputed

(New

sway.

It

Jersey).

now becomes

struggle of pine with pine to see which

Enemies of old pines. fallen they

is

a

the stronger.

As the conquered

trees

have

have crushed down others, or they have

The wood the mushroom and

broken large limbs and bruised the trunks.

and timber enemies, in the shape of bracket fungi, enter the

wound by

the "heart" of the tree, so that hollow.

tiny threads and rot it

is

weakened and

Fires run through the forest, flashing through

'

BATTLES OP PLANTS IN THE WOELD

234

Sound logs. the leaves and burning longer in the dead which makes trunks are scorched and sometimes kUled, Insects, in the other entrance places for their enemies. " " destroy. shape of " borers and saw-flies," wound and

Man sometimes a great enemy the woodman may come to level

of

Then

the forest.

the giants with axe

Against him the pines have no means of

and saw.

defense.

are

cut.

The finest trees Here is one

which has suffered from a fungus enemy, and so has a hollow trunk. The

woodman

spares that

tree because

it is

value to him.

standing alone to tale of the

of no

It is left tell

the

proud pine

forest and its grand struggle for mastery.

Then man begins Fig. 286.

A

bracket "

mushroom

" growing

from a maple.

and the brushwood are ally rooted out.

'

'

civilizing

his

influences.

'

The old fallen trunks burned. The stumps are gradu-

The ground

is

plowed and planted.

Here and there are a few of the remaining giants which

man field.

for one reason or another leaves in his cultivated

One

of these is the

towering hollow trunk of the

THE STEUGGLES OP A WHITE PINE It has the look of centuries.

pine.

.

It has ceased to

advance.

Near the top

branches.

Buildings spring up where once

stood.

Many people come

235

of the tall trunk are great its

comrades

to admire this battle-scarred

j^k^

Tia. 288.

White

pine.

Besult of a tuBsle with a gale.

THE STRUGGLES OF A WHITE PINE rocked to and limbs would yielding,

Now

fro.

seemed as

if

the slender

off. But they were lithe and and recovered and straightened from each

be torn

heavy thrust of the and

it

The

gale.

old pine stood proud

A fierce

fixed, its litheness of limb nearly gone.

gust of the wind snapped

stem and dashed

and

237

stiffly

did

it

the

down

off

a huge limb like a pipe-

into the

snow bank.

old pine hold

Firmly

out against each

onslaught of the gale, but fiercer came the gusts and half a dozen limbs lay half buried in the snow,

and only

the stout stubs stood out where once large branches

were. still

Finally the wind subsided, and the

old pine

stands, with only its topmost branches left.

sad to think that the time old tree

must go down.

is

near at hand

It is

when

the

CHAPTER XXXI STRUGGLES AGAINST WIND

While

the wind

is

of

very great help to

and thus giving

in scattering their seed,

and young individuals,

is

it

which plants have to contend.

often an

many plants

enemy

localities

direction.

against

Hurricanes and cyclones

sometimes sweep down large tracts of forest

some

new

rise to

In

trees.

there are prevailing winds from one

These winds are so frequent and of such

force that the tree cannot maintain its

normal

erect

Such prevailing winds often

and symmetrical growth.

occur along the seacoast or near large lakes, and in

mountainous regions, where there are certain wellestablished

and marked

air pressures

which tend

differences in temperature

and

to create continuous currents

in definite directions.

In some places along the seacoast and on mountain heights, especially

elevations

in

on the

mountain

of

mountains or on

passes, the

strong winds are

sides

nearly all from one direction and of such force that the entire tree leans

grow side.

with the wind

;

or the trunk

erect while all the branches are

The young

lithe

may

on the leeward

branches which come out on 238

240

BATTLES OF PLANTS IN THE WOELD

the windward side are bent around in the opposite direction.

The wind keeps them bent

in this direction

growth and hardening of the the branch in that position, a good

so continuously that the

wood

finally fixes

example of the force of habit.

Pig. 290.

it

it

easier to

—

The young branch

Tree permanently bent by wind (coast of

bend with the wind than to

becomes old

this habit is fixed,

New Jersey).

resist

in regions

it.

When

and the bent and

gnarled branches could not straighten even should moderate.

finds

if

the wind

Very interesting examples are seen where the trade winds occur. The trade

Pig. 291.

Fig.

292.

Old cypress trees, permanently bent by wind (Monterey jOoast of California).

Main trunk straight, branches all bent and fixed wind from one direction (Kocky MountainsJ.

to one side by

BATTLES OF PLANTS IN THE WOELD

242

winds are not very strong, but they blow constantly in one direction.

Fig.

293 represents a silk-cotton

tree

on the island of Nassau, in the Atlantic Ocean, tree this

is

inclined as a result of the constant wind.

tree

is

exposed to the wind, buttresses (bracing

roots) are developed at the base

that the silk-cotton tree

said

Fig.

The Where

293.

of the trunk.

when growing

It is

in the

Tree permanently bent by trade wind (Nassau).

where the wind does not exercise such force on has no buttresses. The one-sided development of

forest, it,

the

banyan

winds,

tree

(Fig.

295), influenced

by the

trade

compare with the one shown where, in the absence of a constant wind in one direction, a symmetrical development has taken is

interesting to

in Fig. 294,

place.

Fig. 294.

Banyan tree spreading equally on all sides from a central trunk where the tree and taking root as it spreads to give support (photograph, Bau, No. 6109).

started,

Fig, 295,

Banyan

tree

moved

in

one direction by trade wind.

portion of the tree

is

at the right.

The

older

CHAPTER XXXII STRUGGLES FOR TERRITORY I

The struggle

is

going on around us

all

the time.

There are opportunities for all of us to see some of

Fig. 296.

Sycamores, grasses, and weeds, having a liard time starting on a rock bed.

these struggles

among

the plants themselves, and the

struggles of plants with the condition of the soil or

weather

or

other surroundings. 244

Go

into

woods

or

STRUGGLES FOR TERRITORY

almost any day and you will see some sign of

fields

A

the warfare going on. several small trees

them down. trees

245

The

and

is

grapevine has covered over

smothering and weighing

grass has stopped growing under

which branch and produce dense

When

ground.

Kg.

297.

the water

is

foliage near the

drained from a marshy

Island witli perpendicular sides in Lake Massawiepie, Adirondacks.

piece of ground, plants

from the

drier

ground rush

and soon the character of the vegetation

is

in,

changed.

Did you ever observe how much quicker the grass or cultivated plants wither in dry weather near large trees off

?

The

tree takes water

from the

the water supply of other plants.

food also.

There

is

often a struggle

soil.

It cuts

It takes their

among the branches

BATTLES OF PLANTS IN THE WORLD

246

of a tree to see whicli one shall get

and thus outlive

its

most of the

competitors.

Certain soils are congenial to certain plants.

grow

plants could

light

in all situations,

we

If all

should have

fewer kinds of plants because there would be so manycompetitors for every foot of ground.

have found one kind of

soil

congenial to them, and

other plants prefer another kind of plants

leave

certain

enter into a contest

territory if

But some plants soil.

So,

many

undisputed, and only

some favorable changes take

place in those localities, provided, of course, their seeds

get

in

there.

We

do sometimes find a few plants

struggling in a very uncongenial

Fig. 298.

become

grow

but they never

Island in Kaquette Kiver, Adirondacks, with sloping sides and providing different kinds of territory.

real competitors

there.

soil,

They

with the plants which like to

are struggling only with the physical

forces of nature, not with other plants.

STEUGGLES FOE TEEEITOEY

247

Struggles of plants on border territory.

The difEerent which are congenial to different plants border on one another. Sometimes the border is very abrupt,

territories

that there

so is

no struggle

on the part of the plants in

one territory over

to cross

into the other.

But in a great

many cases the change from one

ter-

ritory

an-

other ual.

to is

grad-

Fig. 299. Border of lake with sloping shore. Cocklebur on the right fighting with grasses on the left (Ithaca, N.Y.).

In these

cases the

border line becomes the seat of a

struggle for

occupation

fierce

between the plants of the

two adjoining areas. These struggles are very commonly seen along the borders of lakes, ponds, or streams, where the ground

down

to the water edge and out into

So, also,

on the borders of marshes or

slopes gradually

deep water.

where there a moist

soil

is

up

a gradual difference in elevation from to one

which

see various kinds of plants

is

drier.

drawn up

Here we often in battle array

BATTLES OF PLANTS IN THE WOELD

248

defending and holding their ground.

The arrow-leaf

grow in soil covered with water on the borders lakes and ponds, where the water is not too deep.

likes to

of

The it

cat-tail flag prefers

a

little less

depth of water, and

contends for the ground nearer the shore, where the

Fig.

water like

300.

is

Plants drawn in battle array on shore line of lake (Ithaca, N.Y.).

very shallow.

very moist

soil

The Joe-Pye weed and boneset

near the water.

In this picture (Fig. 300) you see such a contest going on,

and the

place

same kind

drawn. Near this an army of rushes occupying the

lines of battle sharply

you could of

see

territory that

here, because the

the arrow-leaf occupies

same conditions were congenial

and the rush drove the arrow-leaf

out.

So,

to

on such

it

dis-

puted grounds, struggles for possession go on between the kinds of plants which like that territory, and the

weaker ones are often crowded out of existence.

CHAPTER XXXIII PLANT SOCIETIES Plant

associations.

Plants which

have

congenial

grow together in harmony on the same territory. There is room for several different kinds, just as there is room for many small stones in dispositions often

the spaces between large- stones in a pile.

Fia.

301.

Moreover,

Peat-bog formation with heaths, cranberries, sedges, etc., growing on and all advancing to fill in the pond. This is a plant " atoll."

several kinds of

plants of

the same size

it,

may have

congenial dispositions toward each other, so that they

can

live

tries to

No

peaceably together. cover

all

the ground.

a spot here and there.

At

one of these kinds

They

least

are content with

they have not very

pugnacious dispositions, nor are they so forward as to 249

BATTLES OF PLANTS IN THE WOELD

250

crowd themselves in and

which

They

live together

push, out the others.

peaceably in this

way form

Plants societies.

are really social in their dispositions, and often

several

kinds in one

They could not

others.

thing to cling great light

to,

dependent on the

society are live alone.

They need some-

or they need protection from the

and heat

of the sun.

Even where the rushes, and cat-tails, and arrow-leaf, and Joe-Pye weed seem to occupy the ground, there are

many

that

fit

other kinds of plants which are not so large

in between the tall ones or cling to them, or

float in the water.

Peculiar societies of peat bogs.

peat bogs or

sphagnum grows, you plants.

When you

visit the

sphagnum moors, where the peat moss

or

will find a society of peculiar

These plants like cold water and other singular

surroundings for their stems and roots. sition is so

common

Their dispo-

unusual in this respect that none of the

plants you are familiar with in the fields and

woods would go territory,

unless

into after

their

society or

many

years the

the territory should change so that

it

in

live

their

character of

would be more

congenial.

Growing along with the peat moss you

will often

find cranberries, Labrador tea, the curious pitcher plant,

and many other plants with thick leaves which are retentive of moisture.

The

plants that associate with

PLANT SOCIETIES the peat

251

moss must be those which give

water into

off

the air slowly, since the cold water

and certain acids

about their roots in the dead

below the surface

p'eat

prevent the roots from taking up water rapidly.

The vegetation on the margin the

of the peat

Fig. 302.

On

bog.

margin of the peat bog, where the ground

is

drier

Plants marching into the sea. They have advanced from the trees at the leit in about two hundred years.

and contains more

up in battle array.

soil,

The

see the plants

drawn

societies are struggling

among

you may

themselves, and are also pushing their into the peat.

The story

way

of the advance

is

slowly out

plainly told

252

BATTLES OF PLANTS IN THE WORLD

by the

size

and age

of the vegetation, as well as

by

its

difEerence in character.

Many

of the peat bogs

were once small ponds or

The peat moss and other plants which find shallow water a congenial place to grow in begin marchlakes.

ing out from the edge of the water toward the center

The stems

of the pond.

grow above.

So hi

this

of

the peat die below and

build up a floor or The dead peat now in. the

way they

platform in the water.

water below does not thoroughly

rot, as

the leaves do

in the moist ground of the forest, because the water

shuts out the pile

up quite

times

is

air.

fast in

entirely

The partly dead stems of the moss making the platform, which some-

composed

grow along with the

peat.

of peat.

Other plants

may

Their dead bodies also help

up this floor beneath. The army of peat and other water plants continues to march out toward the center of the pond, though to build

slowly.

Finally, in

many

cases

the line around the

shore meets in the center and the pond

having been extended entirely

floor

keep on adding each year to the

and higher, until

it is

is filled

across.

up, the

But they

floor, raising it

higher

high enough and dry enough for

the marching armies of the dry land grasses, shrubs,

and

trees.

At length a

floor built across the

other

members

forest comes to stand on the pond by the peat moss and the

of its society.

PLANT SOCIETIES Forest societies.

253

There are many kinds of

societies, just as there are of

herbaceous plants.

forest

These

depend on the elevation, the action of the climate, etc.,

as well as

on the kinds of

arctic regions are different

Fig. 303.

zones,

bearing,

The

of the temperate

Vegetation on border of marsh.

and these are

tropics.

Forests in the

trees.

from those

soil,

different

society

and evergreen

may

from the

be at

trees,

first

forests of the

mixed, cone-

with broad-leaved

trees.

In the end of the struggle some of these are likely to Where the forest growth is even and be crowded out. the leafy tops cut off

much

of the light, the forest floor

Fig. 304.

Coniferous forest society, white pine.

PLANT SOCIETIES will be covered

255

with leaves there will be an absence of shrubs and herbs, except the shade-loving ones, and the wood will be open below and free from " undergrowth."

When

;

the forest

growth of the

Fig.

305.

open above because

of the unequal

trees, or because of the

destruction of

is

Edge of broad-leaved

some of the larger

forest society in winter.

trees, light will enter

and encourage

a greater or less development of undergrowth, trees, shrubs, flowers, grass, etc.

Then,

too,

— young you ob-

serve in the forests the great numbers of mushrooms,

BATTLES OF PLANTS IN THE WORLD

256

but

singular

beautiful

and important members

Some

a forest society.

of

of

them, however, become

enemies of trees, entering at wounds and rotting out the heart.

Others attack the leaves, and by injuring

or destroying life

these food-getting

organs weaken the

Others attack branches and deform

of the tree.

or blight them.

Mosses and lichens, in the temperate and arctic greatly

forests,

the

influence

character of

trunk which they cover and color.

the

tree

Those hanging on

branches give a grotesque appearance and sometimes

In sub-tropical and tropical forests there

do injury. is

a tendency to a change of position of the smaller

members

of the society

tree tops,

where hanging moss and tree-dwelling orchids

from the

forest floor to the

and ferns abound.

The oddest looking

Desert societies. are

desert

kinds

of

societies,

cactus,

— the

many

rapidly as thin leaves do

by the

of the cacti covered with

These large fleshy trunks do not

suited to is

grow

;

so

lose

water so

these plants are well

in the dry climate of the desert,

often parched and

plants.

of different

with no leaves on them, or the

sprawling opuntias, spines.

the soil

of plant societies

great trunks

little

where

water can be found

This character of the vegetation

is

the

result of ages of warfare

with uncongenial conditions.

All plants not suited to

grow here

either have been

258

BATTLES OF PLANTS IN THE WORLD

driven out or have not been able to enter.

which could take on these forms of the yuccas,

etc.,

bore trunks with

leaves at the tops, survived,

a

Tliose

cacti, or of the

few hard-skinned

and now find these con-

ditions quite congenial to them.

Not every one

Fence-corner and roadside societies. of

you can go to the desert to see the desert

i^fe^ y.f^..jli^»i(tx:F Fig. 307.

-

*^

societies,

-

Desert society, chiefly yucca.

or to see the arctic or tropical societies.

be content with pictures of them.

You must

But nearly every

one can see plant societies near at hand that are interesting

if

you, in large

looked at in the right way. cities,

Some

of

perhaps do not often see fence

BATTLES OF PLANTS IN THE WORLD

260

corners (though there are some in the heart of

York

city) or

country roads.

But you surely get an you

don't,

Then you can study

fence-

outing into the country once in a while.

you ought corner

that's

all.

roadside

societies,

societies,

If

and

field

forest

the brambles, weeds, berries, golden-rod, and

societies,

asters,

to,

New

and the new-mown hay.

Garden

societies.

a garden society

;

a

Most little

you can have, at least, plot of ground where you can of

plant seeds or see the flowers grow, and in the corner of the garden a place

may

where the wild flowers and weeds

struggle.

am

Here, I

Plant societies in windows.

sure,

all

Fasten on

can have a plant society for observation.

a window ledge a long box, with broken bits of crockery in the bottom

and garden

soil

on

should be an outlet in one end to drain water.

Here you can grow

top.

There

off

the surplus

peas, beans,

and other

them struggle with each other and turn toward the light. In another box, or in pots, you geraniums, primroses, and can raise some flowers, plants to see

—

other suitable ones.

You can

also

up an aquarium be

have a water-plant society by in a well-lighted

made by using a

small ones can be pans.

window.

fitting

This can

large glass vessel, or perhaps some

made by using

Put some garden

soil in

fruit jars or

broad

the bottom to supply

PLANT SOCIETIES

261

some of the

food. Then nearly fiU the vessel with In these aquaria you can place elodea, the pond scum, and other water plants but do not have them too crowded. "With several of these aquaria and

water.

;

the

window gardens you

will have an opportunity of learning some interesting habits of plants.

While you can learn many interesting things about plants from window-garden societies, you should not be content with these mere glimpses of the habits and

The

social life of plants.

in their

own homes

is

improve every opportunity to and woods, become acquainted with

visit

the fields

some

of the flowers

their

best place to study plants

;

so

and trees, and especially to study behavior under different conditions and at dif-

ferent seasons of the year.

"When the

fields

and woods

cannot be visited, the parks and gardens will furnish

many

from which you can read most interif you will only try to interpret the sign

subjects

esting stories

language by means of which the trees and flowers express to us their lives and work.

INDEX AbutUon, variegated leaf Acorn, 174.

Carbon dioxid, 123-131.

of, 111.

Carbonic acid, 123, 125.

Akene, 170. Amanita, 217. American creeper, 154.

Caulicle, 19, 20.

Caustic potash, 129, 130.

Cedar of Lebanon,

148.

Ampelopsis, 164. Annuals, 42.

Cell,

Apple, 173, 174.

Chloral hydrate, 111.

Assimilation, 119.

Clematis, seeds

make-believe plant, 76-78.

Cells, plant,

work

of, 79, 85.

of, 182.

Climbing by coiled stems, 151.

Banyan tree, 242, 243. Barium carbonate, 127. Barium hydrate, 127.

Climbing plants, 150-155.

Baryta-water, 127.

Cobalt-chloride paper, 97.

Beggar needles, 170. Behavior of flowers, 156-167. Behavior of plants, 132-167.

Compass plant, Corm, 52.

by by

roots, 154. tendrils, 152.

Cocklebur, fruit

of, 183, 184.

143.

Berry, 172.

Cotyledons, 3-6, 12-15, 72, 73, 108.

Biennials, 43.

Cross pollination, 164, 167.

Blackberry, 172.

Cypress

Bladder membrane, 76-78, 90. Breathing of plants, 126-131. Buds, 33-39.

Dandelion, curling of stem, 85, 86.

Bulb, 50.

Desert societies, 256-258.

Burdock, seeds

seeds

bent by wind, 240.

of, 178, 182.

Dodder, 151, 152. Drupe, 170, 173, 175.

fruit of, 183.

Bur marigold,

tree,

170.

of, 183.

Buttercup, flower

Earth stars, 220, 221. Elm, seeds of, 182.

of, 156, 157.

Buttresses, 57.

Elodea, 115, 116, 121.

Embryo,

Cactus society, 257.

Calcium carbonate, 127. Capsule fruit, 169.

19, 22.

of fern, 209.

Embryo 263

case, 192, 193, 226.

INDEX

264 Endosperm,

Jack-in-the-pulplt, 164-166.

22, 23, 209.

Jewel weed, explosive fruits

Erect plants, 40, 41. Fern, bank of ferns, 205.

Leaf

scars, 37.

Leaves, 60-73.

bracken, 211. Christmas, 206.

autumn,

fruit dots of, 205, 206, 208.

color of, 60-62.

life

62.

compound, 63-65.

story of, 204-211.

little

dodder, 61.

spleenwort, 207.

maidenhair, 208.

duration

polypody, 208.

evergreen, 202, 203.

prothallium

of,

208-210.

of, 72.

Indian-pipe plant, 61.

spore cases, 205, 206.

mosaic

spores of, 205, 206.

position of, 67-70.

walking, 210.

purslane, 61, 63.

of, 71.

Fire, effects of, 233.

simple, 63, 64.

Fittonia, 71, 72, 148.

spine-like, 66.

Forest, mixed, 231.

variegated, 61, 112, 113.

conifers above broad-leaved trees,

veins of, 72, 108.

wearing a mask, 65,

231.

work

Forest societies, 253-256. Fruits, 168-175.

royal bit

fruits of,

176.

of, 193.

behavior of

Light,

Garden balsam, explosive

66.

of, 73, 115.

Life substance, 92, 193.

Fruits explosive, 177.

plants toward,

136-149.

on growth, 137-139.

effect of,

Garden societies, 260, 261. Gas given off in starch-making, 121-

importance

of, in

starch-making,

116, 117.

influence of, on leaves, 142-149.

125.

Germ,

of, 176.

Lime-water, 127.

193, 208.

Germ pocket

of fern prothallium,

Maple, seeds

208, 209.

Girdle scars, 37.

of, 183.

Milkweed, seeds

of,

177, 178.

Mimosa, 132-135. Herbaceous plants, 44. Hydrogen, 124, 125. Hypocotyl, 19.

Moss, capsule life

pigeon-wheat, 213, 214. spores

Impatiens, explosive fruits Iodine, tincture of, 109.

of, 213, 214.

story of, 212-214.

of, 176.

of, 214.

Mushroom, bracket, horse-tail, 220.

232, 234.

INDEX Mushroom, ink life

story

cap, 219.

of,

mycelium

216, 221.

of, 217.

poisonous, 217-219.

265

Protoplasm, 92. royal bit

of, 193.

Pufiballs, 220.

Pumpkin

flower, 158-160.

shaggy mane, 220. shelving, 232, 234.

Raspberry, 172, 173.

spawn, 216.

Receptacle, 171.

spore print, 216.

Respiration, 126-131.

spores, 216.

Rhizome, 49. Roadside society, 259. Root hairs, 10, 11, 15,

Nitrogen, 124.

Roots,

Oak, life story of, 194-203. moss-covered, 200, 201.

behavior

over-cup, 200, 201.

bracing, 56. fibrous, 55.

virhite,

growth

194, 198-200.

Ovule, 192.

toward moisture,

of,

32.

red, 197, 200. scarlet, 196, 200.

16, 58, 59.

air, 55, 56.

of, 24, 25.

pressure

of, 87.

taproots, 54.

work

Oxidation, 131.

of, 57,

Oxygen, 123-125.

Rootstock, 49.

87-93.

Peat bogs, 251.

Samara, 182, 183.

Pepo, 174.

Scale soars, 37.

Perennials, 43.

Screw

Petioles, rigidity of, 83, 84.

Seedlings coming up, 1-6.

Pine, white, fruits of, 223, 225.

Seeds, contrasted with fruits, 168.

pine, bracing roots of, 56.

seeds of, 225.

germinating, 7-17.

struggles of, 222-237.

how formed, 158, 192. how scattered, 176-184.

Pines, bull, 229.

enemy

of,

a shelving mushroom,

Plant atoll, 250. Plant societies, 249-261.

Poison ivy, 55, 154, 155.

Silk-cotton tree, bent

bracing roots Silkweed, seeds

174.

Pond scum,

Shoots, winter, 33-39.

117.

Prickly lettuce, seeds Prostrate plants, 42.

by trade wind,

242.

Pod, 169, 171, 172.

Pome,

winged, 182. Sensitive plant, 132-135.

232.

of, 182.

of, 57.

of, 177, 178.

Skunk cabbage, 165, 167. Spawn of bracket mushroom, Sperm, 193, 208, 209.

233.

INDEX

266 Sperm pocket

of fern protliallium,

Teasel, flowering of, 163, 165.

Toadstool, 218.

208, 209.

Star cucumber, 153.

Torus, 171.

Starch, 109.

Touch-me-not, explosive

uses

fruits

of,

176.

test for, 109, 114.

Tuber,

of, 119.

51.

Stem, 45-53. ascending, 49.

Vascular bundles, 106-108.

burrowing, 49.

Virgin's bower, seeds of, 182.

climbing, 48. deliquescent, 47.

Water,

diffuse, 47.

growtli

of, 26, 31,

.'52.

prostrate, 48. trailing, 48.

Stick-tights, seeds of, 183.

Stone

absorption

fruit, 170.

Strawberry, 170, 171, 173. Struggles against wind, 238-243. for territory, 244-248.

loss of,

use

by

plants,

161-163. effect of light on, 144-146.

Sweet-pea, flower, 189-191.

by

plants, 94-106.

of, to plant,

trade, 242. trees

permanently bent by, 240-

243.

Witch

hazel,

explosive

177.

Woody

plants, 44.

formation of seed, 192, 193. story of, 185-193.

74-86.

Water paths in plant, 106. Water vapor, 96, 97. Wild lettuce, seeds of, 182. Wind, struggles against, 238-243.

Sunflower, behavior of, in flowering,

life

of,

87-93.

excurrent, 46.

Yucca

society, 258.

fruits

of,

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