[Illustration: [Leaves]]
After all, that is what a rose is,—nothing but leaves; and what a violet
is and a lily and a nasturtium and a honeysuckle and all the flowers you
can name.
You do not believe it? That is because you know so _very_ little about
leaves. When you know more, you will believe it, see if you do not.
Perhaps when you know where the flowers came from and how they came to
be flowers at all, you will change your mind about several things.
Anyway, there is one thing you do know, because you have studied
geography and about the stars and about the earth’s crust and all that.
You know that once upon a time there were no flowers in all the round
old earth. You do _not_ know it? Why, of course you do. You know that
once upon a time there was no life on the earth, at least not what we
call life now. It was so hot _nothing_ could live, not even a
salamander, which they say lives in the fire, although, of course, this
is not true, and it could no more live in the fire than you could.
Well, we are told that once the earth was about as hot as the sun is
now,—just a mass of blazing gases and melted rocks and metals.
You would not have known it if you could have seen it, and, what is
more, you would not have wanted to see it; you would have been afraid to
come near enough.
You could not have found Lake Michigan on it nor even the Atlantic Ocean
nor the Rocky Mountains, and the reason you could not have found them
is, they were not there. There was no Lake Michigan and no Atlantic
Ocean and no Rocky Mountains.
You see, they had not been made yet. All the water and minerals were
bubbling and seething and whirling around in the most awful storms. You
would have wanted to get as far from the earth in those days as you
possibly could; not even the North Pole was cool enough to rest upon
with any comfort.
This went on for a few millions of years probably, but the earth was all
the time getting a little cooler, until it got so cool that things began
to harden and the dry land to appear. But mother earth was in a state of
terrific excitement even then, and every once in a while would heave
such a sigh that an earthquake or volcanic eruption would break forth.
But as old earth, or young earth I suppose it was then, grew older and
calmer, it settled more and more into its present form. It got so cold
and old after awhile that it became wrinkled, like the skin of an apple
in the late fall. You know how that is. Only mother earth was a very
large apple and her wrinkles were very deep, and in fact they made the
great mountain ranges.
You need not believe all this unless you want to, but it is true,—that
is, the wise people, who know more than you and I ever will, say so.
But what has all this to do with leaves?
It has as much to do with leaves as the fire in the stove has to do with
the boiling of the tea kettle.
Of course, while the earth was in this overheated state, nothing could
grow on it. But it kept getting cooler and cooler, until at last life
began to appear. Just exactly what this first life looked like I do not
know. Nobody does, because, you see, nobody was living then to tell
about it and write it down. But very likely queer mushy plants were the
first to come along, and they were about all leaf. So far we may be
pretty sure.
After awhile plants with stems and leaves grew up and flourished.
They were queer enough, no doubt, for there are pictures of some of them
which the rocks took and kept for us, and people often break open a rock
nowadays and find these old plant pictures.
[Illustration: [Leaves]]
They are what we call fossils, and now I have no doubt you know all
about it; if you do not you will some day,—that is, if you care to.
From what the rocks tell us, and for other reasons, we feel pretty sure
that the earlier plants had only leaf and stem, but no flowers. And the
very first leaves were not like the leaves we see in the woods and
gardens about us, for they were probably large and mushy and had no
veins to speak of. If you had picked one up it would have been flabby
and squashy, and you would have been glad to put it down again. But
nobody ever did pick one up, because nobody was there.
The earth was not ready for us yet. It was all soft and swampy or hard
and cheerless, and we had to wait until these queer pioneer plants
gradually changed into other plants and made the earth fit to live on.
But these flabby old friends of ours went to work with a will to get
things in shape for us to come. Their green leaves and stems, where they
had any, ate the gases in the air and stored them up as plant material.
Then they died. They did us as much good by dying as by living, for only
part of their substance went back as gases into the air; the rest went
into the ground and began to make soil for other plants to grow in.
So Mr. Flabby Leaf was a very good life starter.
[Illustration: [Fern]]
One thing we are quite sure of, and that is, these earlier plants did
not have any seeds. When new plants came from the old ones, they merely
sprouted out from the leaves or the roots, as a certain fern that grows
in Fayal and other places does to-day. It is fun to raise this fern in a
window box and watch the young ferns sprout out of the edge of the
leaves of the old fern. After they get two or three tiny green leaves
and the cunningest little curled-up frond, just like a big fern, off
they tumble down to the ground, where they strike root and grow as
calmly as though they had come the regular plant way and sprouted from a
seed.
They do come the regular way the very early plants did, instead of
coming the way modern plants do, for in some such way the earlier
plants, no doubt, reproduced themselves.
They had no flowers and no seeds. Leaf and stem did it all. You see,
these first plants were simple people, not complicated at all, and so
each part of the plant was able to do all its own work. But after awhile
the plant world became more complex; the earth grew drier, for one
thing. The first plants lived in the water, no doubt, and so everything
was much easier for them; at least they could always get plenty of
water, which is a matter of great importance with plants.
No water, no plant. Then, too, the earth cooled more and more, and from
being uniformly warm and moist, which was just the best conditions for
plants to live without taking any trouble about it, the air was
sometimes colder and contained less moisture.
So the plants that grew on the land had to invent ways of getting and
keeping an extra amount of water, and even those that lived in the water
had to look around and find a way of protecting themselves against
changes of temperature.
[Illustration: [Leaves]]
As the earth grew cooler and drier, and the changes from hot to cold at
the different seasons became more marked, the plants that grew on the
prairies and mountain sides, where it was very hot and damp at one
season and very dry or very cold at another, had to find ways to protect
themselves against these changes. So the leaves and stems began to be a
little more particular about their work. The leaves may have said, “We
will do one kind of work in one part of us and another kind of work in
another part. We will have stiff veins and ribs to protect us from being
blown to pieces, and we will have our sap flow through veins, instead of
soaking all through us everywhere. And we will have a thick skin to
breathe through and to protect us from the sun when it is too hot.”
So some lived on the hot plains with small, thick, hard leaves, and
others lived in the damp shady woods with large, thin, tender leaves.
Thus, you see, there came about a division of labor. Not all at
once,—oh, no! but so gradually, so very gradually that, had you been
watching these plants grow from year to year, you could no more have
seen any change than you can see a blade of grass grow to-day, although
you know it _does_ grow. Perhaps the plants on the edge of a swamp were
the first to change.
Perhaps the water receded and so gradually left them higher and drier.
As they got less water, they would have to do one of two things,—change
to suit the new state of affairs or give up trying and die. Very likely
a good many died; the water may have receded too rapidly, or they could
not see just how to change. But others did see, and they stiffened their
flabby leaves with ribs and veins and made for themselves a thicker
skin, and so lived on. They survived because they were the fittest to
survive. And now you know the meaning of that very celebrated saying,
“the survival of the fittest”; whatever plant or animal can adapt itself
the best to the place it lives in is the fittest, of course, for that
place, and so it survives or lives on.
No doubt, in those early days, new plants grew out of the old ones just
anywhere as the baby plants grow out of the leaf of the Fayal fern I
told you about.
But as life grew more and more difficult, as the plants had to contend
with too much heat at one time and too great cold at another, with now a
season of moisture and now one of great dryness, their leaves, as you
know, began to change and divide up the work. A part of the leaf
breathed for the plant; another part ate for it; another part protected
it. Nor was this all. Some leaves did one kind of work and some another,
as time went on.
[Illustration: [Cactus]]
When animals came upon the earth they ate the plants, and so the plants
had to partly protect themselves to keep from being entirely destroyed.
Thus some plants changed part of their stems or leaves into sharp
thorns, as we see to-day in the hawthorns and cactuses. Some, like the
mullein, covered their leaves with a disagreeable wooly substance that
stuck to animals’ mouths and made them avoid the plants. These wooly
coverings served two purposes,—regulated evaporation and protected from
the attacks of animals. Some, like the aconite, manufactured a
poisonous, disagreeable juice, while others, like the nettle, clothed
the stems with stinging hairs.
There are many, many ways by which plants have changed their leaves and
stems in order to protect themselves from being eaten, and all this came
about very, very gradually.
While these things were happening, other things were happening too.
Wherever there is life there is change. Living things keep changing all
the time.
The little fern that drops from the leaf of its parent is, in a general
way, like the parent, but it is not exactly like its parent; it is
_itself_ and has some peculiarities of its own. You see, it changes a
little from the parent form or, as we say, varies. Every living thing
has this power to vary within limits. No doubt, the power of variation
was much greater in early times, and animals and plants were able to
change much more then than now.
As time went on, things sort of settled down, as it were, and stopped
changing so rapidly.
But way back in the early ages the plants changed a good deal. And all
they had to work with, you will remember, was just stem and leaves,—not
another thing. But that was enough. They could change stem and leaves
into thorns, as we know, and they could do something else. They could
change leaves into pistils.
When the leaves divided their work, some plants devoted certain of their
leaves to the task of making new plants. Ferns show this up to this very
day.
Look at a clump of ferns in the woods any time in the middle of the
summer or later, and you will see that some of the fern leaves have
little dark spots on their backs. Sometimes these dots are on their
margins, sometimes on the ribs, and sometimes scattered everywhere over
the back of the leaf.
These dots are little cups filled with a fine dust, which falls on the
ground and finally gives rise to more ferns. It is sometimes called fern
seed, but the bits of dust are not exactly seeds. In the end they answer
the same purpose, however. Well, suppose one of these fern leaves with
the dots growing on it should curl over backwards until its edges met,
and suppose the little grains should become true seeds, then we would
have a very good ovary with the ovules inside.
Fern leaves do not act in this way; they are too old-fashioned. But some
of the leaves in flowering plants do. They just roll up into a pistil,
with young plants, in the form of seeds, growing inside.
And to this day that is all a pistil is,—a leaf, or a whorl or circle of
leaves, rolled together, with seeds growing along the inner part. Of
course, in time, these pistil leaves changed very much, and to-day we
find all sorts of pistils, and by just looking at them, we would never
suspect they were leaves or ever had been. And they are not leaves any
more, and they themselves never have been leaves; but long ago the
pistils of their ancestors were leaves or parts of leaves, and they have
inherited and improved upon these pistil leaves, as a boy improves upon
a willow twig and makes it into a beautiful carved whistle that does not
look at all like a willow twig, and yet that is just what it is at
heart. So you see, one of the most important parts of the flower is,
after all, “nothing but leaves.”
After seeing how the pistil, with its seed-children, is modified leaves,
you will not be surprised to learn that stamens, too, are merely
modified leaves. Anyway, whether you are surprised or not, that is just
what they are. Tender little leaves folded a part of themselves together
into little rooms or cells, and on the inside of these cells the pollen
grains grew.
[Illustration: [Cactus]]
Now the plant was all fitted out. It had flowers, not very beautiful
ones, to be sure, as they had nothing but pistils and stamens. Still
they were flowers, and flowers are flowers whether they are bright or
not.
Pistils and stamens were enough at first. But times change. Each plant
tried every possible means to make strong seeds, so it could live in the
crowded world. It did not wish to be crowded out, you see. So when it
discovered the value of cross-fertilization, it began, so to speak, to
invent ways to bring this about.
The insects with wings came to it and brought it pollen, so it learned
to coax the insects to come oftener. It made quantities of pollen, so
the insect could eat what it would and still leave enough for the plant.
It, no doubt, had several rows of stamens, as a wild rose or a cactus
flower has to-day. But it soon found out a good use to put some of these
stamens to.
It wanted the bees to see and come, so it changed some of its stamens
into petals.
The anthers ceased to grow, and they and the filaments spread out broad
and bright. So, you see, petals, too, are nothing but leaves,—very much
changed leaves, true, as they were first leaves, then stamens, and then
petals, but that does not prevent their having come from leaves after
all.
If you want to see how it is done, look at a water lily next time you
get a chance.
Unless it is a very unaccommodating lily indeed, you will be sure to see
stamens changing into petals.
Some of the inside petals are small with an anther at the tip.
Of course flowers do not go through all these changes every time they
bloom now. They used to way, way back, when things were in a general
state of change, but after awhile they found out just how to do it, and
so out of the tiny buds at once made pistils and stamens and petals and
sepals.
For sepals, too, came from stamens. The plants made all these new forms
out of the materials of their leaf buds and wrapped them all together
into a flower bud; so when this opened, there were the parts all ready
to go to work without any more shifting around.
The calyx was ready to protect, the corolla to call the bees and
butterflies, the stamens to make pollen, the pistils to make ovules.
Sometimes flowers forget and go back to the old ways of doing things;
and if we are lucky enough to find such a flower, we can see just how it
happened.
Sometimes roses behave in this peculiar way, and the flower goes back to
leaves.
I used to know a bush whose roses did that. The pistils were leafy and
also the stamens, and sometimes a branch grew right out of the middle of
a rose as it does out of a leaf bud. Of course it was a very
ugly-looking thing, neither flower nor leaf, but it was very
instructive.
What do you suppose double flowers are?
Very often they are only flowers whose stamens have changed into petals.
A double rose has fewer stamens than a single rose, and sometimes _all_
the stamens are changed, and the rose has not a grain of pollen to help
itself with. What becomes of its seeds? It does not have any, as a rule.
Where flowers become very double, the vitality goes to make petals
instead of essential organs, as stamens and pistils are called, and such
flowers often set no seeds.
Then how do they continue the life of the race?
Sometimes simply because somebody takes care of them. Almost always
double flowers are cultivated ones. People take them and tend them, give
them rich soil to grow in, water them, and, if necessary, keep them
warm. Such plants seem to grow lazy and helpless, as rich people who
pamper themselves a great deal always do. They have all they want
without any effort of their own, and so they cease to be
self-supporting; they cannot even raise their own children, but live and
die seedless. Such plants, if left to themselves, would quickly die, as
they would be crowded out by sturdier growths, or else they would change
their habits at once and become good seed-setting, industrious plants
once more, with a tendency to stop having double flowers.
There are one or two things about corollas that I am sure you would like
to know. One is, how did the flowers manage to change stamens into
corollas? Another is, how did they manage to give them such bright
colors?
About corolla-making,—if you are determined to know that, you will have
to take yourself off to that far-away time when there were no flowers.
Then, in course of time, while changing about and trying to get fitted
to their surroundings, the plants, as you know, rolled some of their
leaves into pistils and stamens. But still they had no petals.
[Illustration: [Corolla]]
The pistils and stamens were flowers, however,—as much flowers as they
would ever be, no matter how much corolla they might develop.
A corolla does not make a flower; by this time you know the important
part of a flower is the pistil and stamens, and so, even to-day, some
flowers, as the elms and some maples, have no petals at all. When such
maples are in bloom, you will see gay fringes decorating the trees. This
fringe is made of the long pedicels with the stamens at the end. The
stamens swing in the breeze, and the pollen is blown to the stigmas
which are often in flowers on different trees.
Now, as plants grew and adapted themselves to their surroundings, they
produced more seeds than could by any chance find room in the earth to
grow. So every little seed that fell had to fight its way with a host of
other seeds and plants. A defective seed or a weak one would stand no
chance at all. The others would crowd it out. We know how that is in a
garden. The delicate flowers have to be helped or the strong weeds would
kill them. We pull up the weeds and let the flowers have the whole
garden to themselves. But in the woods and fields each plant has to take
care of itself and struggle up as best it can.
This fight of the plants for a place to grow in is called the struggle
for existence. Now, whatever would help a plant in the struggle for
existence would, of course, be of great benefit to that plant. As we
know, cross-fertilization is a very great help; it makes stronger and
better seeds, and the plants whose seeds were regularly cross-fertilized
would be the ones to survive.
Where pistils and stamens are forming, there is a great deal of
nourishment brought to that part of the plant, and substances are being
changed there. Very often sweet juices are present. Long ago when
insects, in flying about, smelled these sweets they doubtless would go
and eat them, and they would also eat the pollen. As they went from
flower to flower looking for food, they would carry pollen sticking to
their legs or bodies, and so would sometimes fertilize the flowers.
The seeds from such flowers would be strong and would have the best
chance to survive. The plants that grew from these seeds would also
inherit the tendency to secrete sweet juices near the flower.
In probing for sweets, the insect would irritate the parts it touched,
and this would cause an extra flow of sap there and very likely the
manufacture of more sweet juice; so the nectary came to be developed.
You can understand how this might be by recalling how the skin of your
hand changes when you first try to do some new and hard work, like
rowing a boat.
After you have rowed a little while your hand is blistered. The constant
rubbing of the oar in one place has irritated it, just as you can
imagine the tongues of the insects rubbing against the delicate flower
tissue would irritate it. Wherever a place on the skin is irritated, the
blood flows to that spot; and so in the plant, where it is irritated,
there will likely be a collection of sap. After the blood has flowed to
the place on your hand which was rubbed by the oar, the spot becomes red
and inflamed and pains you, and finally the skin separates in the form
of a blister and a new skin forms underneath; and if you keep on rowing,
your hand does not keep on blistering, but actually makes a new kind of
skin to protect the rubbed places, and what we call a “callous” or hard
spot is formed. The skin is many times thicker here than elsewhere, and
was formed on purpose to protect the place. So we can understand how
irritation might change a plant organ and in time form a nectary.
But how about petals, you are asking. Well, imagine yourself in those
old times when plants made their first flowers out of pistils and
stamens only.
These primitive flowers were probably not very showy. Primitive flowers
means _first_ flowers,—flowers that lived way back in the beginning of
plant life.
They had no petals, but they secreted juices which the insects liked.
Those early insects were queer fellows, too, not very much like our
insects, except that they were fond of sweets and liked to eat the
tender parts of the flowers, just as our insects do to-day. They ate
nectar when they could find it and did not disdain pollen, which, it is
to be feared, they sometimes ate, anther and all; and, what is worse,
they in all probability frequently dined on pistil, which was very bad
for the plant.
Now imagine one strong plant secreting a good deal of nectar. The
insects would be likely to eat this and let the pollen and pistil alone,
only in getting to the nectar, they would be apt to dust the pistil with
pollen from another plant which they had been visiting and would also
brush off some pollen against their bodies.
Thus the strong plant with the abundant nectar would be cross-fertilized
and would keep its pistil unharmed. It would be very likely to develop
good strong seeds that would grow and again bear strong flowers with
plenty of nectar. Now, remember the essential organs—that is, stamens
and pistil—seem to find it a little easier to change than other parts of
the plant; so it would not be surprising if in time some of the stamens
were to become different. You see, the insects in visiting the flowers
would irritate them more or less walking over them and clinging to them,
and they would be likely to undergo change for this reason; and if it
happened that in some flower a row of stamens got too full of sap to
know what to do with themselves and so spread out a little broader and
more leaf-like and kept their yellow stamen color or bleached-out white,
that flower would be seen far and near and the insects would go straight
to it, for insects have the sharpest kind of eyes for seeing bright
colors a long way off. You see what would happen; all the flowers whose
stamens had done so would be abundantly cross-fertilized,—that is, all
their seeds would get fresh pollen from another strong plant, and the
plants growing from these seeds would inherit the tendency of their
parents to form petal-like parts from some of the stamens. The flower
could well afford to lose part of its stamens for this purpose. Of
course as time went on, these stamens, which were half petals, might
develop more and more in the direction of signals,—that is, might become
more and more perfect petals, finally losing all trace of their old life
as stamens.
Of course no one can say that is just the way it came about, but it is
likely that in some such way it happened, for there are proofs of it
which you may like to read when you grow older.
So, you see, flowers _are_ nothing but leaves after all,—very much
changed leaves, to be sure, but yet just leaves.
Sometimes when plants and animals have changed into a new form, they
change back again. We know some plants which once had petals but which
have again lost their petals and gone back to a form which has no
petals. Such backward changes we call retrogression, and it is sometimes
difficult to find out whether a flower with no petals is a primitive
form which for some reason has not changed or whether it is one which
has changed and gone back again. Usually, though, we can find traces of
petals and sepals in flowers which have retrogressed.
You see, a flower depends upon its surroundings for its shape. If its
surroundings (and of course this includes its insect visitors) are such
as to favor its growth in the line of petals, it does so. But if for
some reason it becomes easier for it to grow and be fertilized in some
other way, perhaps by making abundance of light pollen which is blown by
the wind, as in the maple trees, then it may gradually lose its petals,
as it depends less and less on insects and more and more on the wind for
cross-fertilization. Nothing in life stands still; it is always
moving,—going on or going back. And this, we know, is just the same in
human life.
[Illustration: [Corolla]]
We cannot stand still; we must keep growing wiser and stronger and
better, or else we must do the opposite.