Chapter IV: Front Matter (4)

Think of the weight a tree has to bear. You could not _begin_ to lift the crown of a large tree, yet the tree trunk has to hold it up in the air. Not only that,—it has to hold on to it when the wind blows, which is a much harder task. Even small bushes and tender garden plants have quite a weight to bear and quite a task to keep their leaves and stems from being blown away. They could _never_ hold on to them if it were not for the wood and other tough cells they have,—never in the world.

These wood cells and other tough cells are made by protoplasm, of course.

The protoplasm builds them very much as it does the tube cells, long and slender, as you see in the picture at the beginning of the chapter, and then when the hard, tough walls are all done, the protoplasm slips out and leaves the strong framework of tough fibres to do its duty. This framework is not only strong, it is elastic, so it can bend easily. If it were not, the first strong wind or the first thing that happened to bend the plant would snap it off short.

You cannot break wood easily, and, if you do succeed, it always bends more or less first. Some wood bends more easily than others, as you know. A willow twig can be tied into a knot, it bends so easily.

Nearly all land plants have these stiffening cells. They run out of the stems down into the leaves and help make their framework of “veins.” The tubes and the strengthening fibres run along in bundles side by side. You see this saves space. If the tubes and strengthening fibres each took a different road, that would not leave much space for the chlorophyll and other working cells. But all the tubes and fibres are closely packed together and run lengthwise, through the stem. All around these long fibres are placed the other cells which are not long and do not form tubes or fibres. Most of those other cells in the leaf contain chlorophyll. They contain protoplasm, and do the work of transforming food materials into plant material.

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WE AND THE PLANT PEOPLE.

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We live and the plants live. Probably neither we nor the plants spend much time thinking about what we owe to each other.

The plants are excusable for this, for they are not great thinkers, at least so far as we know.

But we owe so much to them, we ought to stop and think about it once in a while. We are indebted to them not only for the food we eat, but for the air we breathe.

We know about chlorophyll and the starch it makes, and how this starch is stored up in potatoes and wheat and corn and rice and all sorts of food grains and vegetables.

We know, too, how the roots suck up substances from the earth which we need in our bodies, and how they are stored away with the starch or sometimes by themselves. We know, in short, how all the food we eat is made first or last by the plants. Not only do we owe our food to the plants, but all animals do.

You see, animal cells are not able to take carbon dioxide and water and ammonia and other gases and minerals and work them up into living cells.

The plants have to do this for them; and then the animals eat the plants, for animal cells are able to work starch and sugar and plant protoplasm over into animal protoplasm, which can build all sorts of animal cells. So all the animals in the world get their food from the plant world. If the plants were to stop living, all the animals in the world would soon starve to death. The word “animals,” you know, means every living thing that is not a plant; in this sense flies and bees and oysters and caterpillars are animals as well as dogs and cats and such large creatures. Last of all, we ourselves are animals.

So the animal world would be in a sad predicament if anything should happen to the plants.

But there is more to thank the plants for than food. That is a pretty large item certainly; but what do you think of having to thank them for the air we breathe as well? Yet this we shall have to do if we begin thanking them at all.

You know about oxygen, of course. It is one of the gases that make up the air; and I may as well remind you that air is composed principally of oxygen and nitrogen gases,—about four times as much nitrogen as oxygen, but the oxygen is the most important to us. We do not use the nitrogen in the air at all probably. It serves the purpose of diluting the oxygen, which would be too strong for us if it were not mixed with nitrogen. But what we do use is the oxygen.

That goes into our lungs, and some of it does not come out again. It passes into the lung cells and from them into the blood, and is carried by it all over our bodies to all the millions of cells.

We need a great deal of oxygen, and if the supply should be cut short we would die.

All animals need oxygen; even the worms in the ground and the fishes and oysters in the water must have it. So great quantities are being used up all the time.

Now, you know, when the plants pull carbon dioxide to pieces, they keep the carbon and return the oxygen to the air. In this way we get it to breathe.

But there is more than this to the matter in hand. We are all the time breathing out carbon dioxide as an impurity; so are all the millions upon millions of animals in the world.

The air might in time contain enough carbon dioxide to kill us if there were not some way of getting rid of it. You know what that way is.

The plants use it up. So by giving oxygen into the air and taking out carbon dioxide, the plants keep the air fit for us and all animals to breathe.

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But there is more than this we have to thank them for.

They shade the earth and regulate the rainfall and the water supply.

Where forests grow there are always streams of water, and the large water courses are kept full the year round.

The Mississippi River depends upon the far-away forests for its broad stream.

The spreading crowns of the trees shade the earth and prevent the water which falls as rain or dew from evaporating rapidly. It collects into streams and flows through the land, keeping the earth fresh and beautiful.

More than this,—large forests cause the rain to fall and the dew to collect. Their leaves condense the moisture in the air and cause it to fall as rain or be deposited as dew.

When people recklessly cut down the forests in a country, the water courses dry up, and even the largest rivers are affected.

When the spring rains fall over a country whose trees have been cut away, the water rushes down the little streams all at once and causes a terrific flood in the large rivers. It soon drains away; then the rivers fall lower and lower until they nearly dry up. This state of affairs is a great calamity, because the people can no longer raise crops on the land near where the old forests stood, for it is parched and dry months at a time.

Moreover, boats laden with coal and grain and all sorts of things can no longer pass up and down the rivers, because the water is too low.

People ought to think of these things and not destroy too much forest land. After awhile we shall have to go to work and plant trees instead of cutting them down or burning them; but it takes a long time for trees to grow, and a wiser way would be for us to take care of those we have.

You have heard a great deal about plants eating and the good they do us by eating the carbon dioxide in the air. They take this in through their leaves, and you remember they take in all their other food materials—water, nitrogen compounds, sodium, potassium, magnesium, and many other substances—through their roots.

But they do more than eat; they also breathe.

They breathe everywhere over the surface of their bodies where there are stomata or where the skin is not too thick for the air to penetrate it.

And I must tell you they breathe just as we do,—that is, they take in air, use the oxygen, and give off the carbon dioxide.

It seems rather inconsistent of them to take in carbon dioxide as food and throw it off as a waste at the same time, but that does not trouble _them_; they do not care whether they are consistent or not. And it is true they take in carbon dioxide and give off oxygen, and take in oxygen (in the air) and give off carbon dioxide, in one breath as it were.

You see, it is different parts of protoplasm at work that does this; one part—that in the chlorophyll bodies—is attracting carbon dioxide, breaking it up, and casting out oxygen. Other protoplasm in the cells outside the chlorophyll bodies attracts and uses the oxygen, while the carbon dioxide comes to the stomata from different parts of the plant as a waste material, just as it comes to the cells of our lungs to be cast out.

So plants, by breathing, make the air a little impure, but they destroy or break up so much more carbon dioxide than they make that on the whole they act as powerful purifiers of the air.

When we think of the great forests of the tropics, all overgrown with luxuriant vegetation, we may remember that those tangles of vines and trees and strange growths are our friends no less than the grass and bushes in our dooryard.

For there is a carrier always at work bringing the pure air to us and carrying away the impure air which we create. This carrier is the air currents. The great winds sweep about the earth, bearing the oxygen from the forests to the crowded cities, and sweeping away the carbon dioxide from the cities to the fields and woods. The winds, too, stir up the water where the water plants and fishes live, and help keep it full of air for the things in it to breathe; the tides and currents help, so as far down in the water as there are living things, you may be sure there is air for them to breathe. There would not be air enough for you, because you need so much; but for them there is plenty.

Swirling around the earth go the winds, carrying the oxygen to the people and the carbon dioxide to the plants, for the plants are as glad to get the carbon dioxide we breathe out as we are to get the oxygen they give off.

And we are glad, when we come to think about it, that we are able to give them something in return for all they give to us.

You see, we need each other,—plants and people, and the winds are friends to us both.

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WHAT ARE THE FLOWERS MADE OF?

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I think flowers are “made of sugar and spice and everything nice.” At least, if it is not that, it is something very like it, as I have good reason to believe.

What flowers and all other parts of the plant are made of depends upon protoplasm; and if protoplasm can make sugar and spice and build up flowers that way, we should like to know it.

We _do_ know about sugar and how the little green chlorophyll people run their starch factories in all the green parts of the plant,—under the skin of stems sometimes as well as of leaves, for wherever a stem is green, we may be sure chlorophyll is at work making starch in it. And we know how the protoplasm in the different cells changes the starch into sugar.

We know, too, how wood and other tough substances are made of starch.

But there is something else in plants as important as starch and very different,—the protoplasm. Protoplasm itself is not made entirely of starch; it requires materials not found in starch.

These materials are nitrogen, sulphur, and phosphorus.

Nitrogen is the most important, and this the plant gets chiefly through the roots.

Nitrogen is found in the earth combined with hydrogen and other substances. The protoplasm tears to pieces these nitrogenous substances which the roots suck up, and so enables the plant to take the nitrogen.

The other two substances which the protoplasm needs, sulphur and phosphorus, the plant gets partly from the air and partly from the earth.

Sulphuric acid exists in _very_ small quantities in the air and goes in through the stomata, attracted, no doubt, by the protoplasm inside. But other sulphurous and phosphorous compounds are taken up by the roots.

So we see protoplasm is complicated. It contains carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus united in a very complicated way.

Although protoplasm itself is made only of carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus, it can make use of a great many other things. When the protoplasm of certain cells wants to build hard, tough walls, it uses potash and soda or even silica, which you know glass is made of. Just draw a blade of sedge grass through your fingers if you want to feel the silica in it. You will probably cut your fingers, but that will help make you remember about silica. Then the protoplasm uses iron to color the petals and other parts of the plant. It uses magnesia, too, and salt and lime and a number of other materials for building walls or making dyes or something else.

Every material in our own bodies is found in plants, and sometimes the plants have materials that we do not have.

Of course materials are put together differently in plants from what they are in us. When Mother Nature combines her carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus, magnesia, iron, and all the other things to make a plant, she does not go to work as she would if she were going to make an animal.

Just what the difference is it would be difficult to tell, but there _is_ a difference.

Plants contain a good deal of sugar as a rule, and if you remember cloves you will admit that at least _some_ flowers are made of spice, for cloves are the dried flower buds of the clove tree.

Cinnamon is the bark of a plant, and if you are acquainted with orange trees you will be willing to say they are “made of sugar and spice and everything nice,” for the whole tree, wood, bark, stems, leaves, flowers, and fruit, is fragrant and spicy.

Oil is another common substance in plants, and it is made from the materials of starch which, as we know, are carbon, hydrogen, and oxygen; cotton-seed oil, olive oil, and castor oil we are all familiar with.

All nuts contain a great deal of oil, and the skin of a fresh-picked orange is so full of it that it runs down our fingers when we cut the orange.

All the things in a plant—starch, sugar, oils, spices, wood, bark—everything is made by the wonderful protoplasm in the cells.

Starch and the food taken up by the roots pass through all parts of the plant by the sap tubes, and as the sap goes along, each living cell draws into itself the substances from the sap that it needs, and these it combines into the things it wants to make. Some of the cells in an orange skin, for instance, attract out of the sap the materials to make the fragrant, stinging oil that fills the fresh skin, while other cells attract the materials to build the white cottony covering inside the outer skin, and so the cells in each part of the plant take out what they need to build with.

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WHAT BECOMES OF THE FLOWERS?

Early in the spring the snowdrops and crocuses peep out, and then they go away.

We do not think much about it, for other flowers have come in their places.

Spring beauties and bloodroots shine in the woods, and then they go away. But the mandrakes have come with their umbrella leaves, and then the columbines and roses ask for a welcome.

After awhile we can find no more mandrakes and columbines, only yellow apples and brown seed-pods.

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Jack-in-the-Pulpit jumps up quite early in the summer, and then we cannot find him, only in the late summer we sometimes come across little clusters of bright red berries lying on the ground.

We would scarcely suspect them of having any relation to Jack, yet they are his berries. But what has become of Jack?

In the autumn the rose leaves fall off, and there is left only red stems and red berries.

The morning-glory vine wilts and turns black at the first frost; it sinks to the ground and we see it no more, or else its stems linger brown and hard for a time, but in the end it all disappears. What has become of it?

And the nasturtiums—what a wreck the frost makes of them! The leaves are wilted and black; the stems, too, are soft and lie flat on the ground.

Why, you say, the frost has killed them. But that does not at all tell what has become of them. Besides, the frost did not kill the snowdrops and crocuses and blood roots and spring beauties nor Jack-in-the-Pulpit nor the umbrella leaves of the mandrakes. Yet they are all gone. All we can find of Jack and the mandrakes are red berries and yellow apples. Not a sign of the snowdrops or spring beauties or crocuses is left.

If you will just step down with me under the earth a few inches I will show you something.

Make believe you are a gnome or a fairy and can see as well in the dark earth as anywhere else and come along. Now look about.

Did you ever dream of anything so cunning in all your life? Everywhere and everywhere old mother earth is packed full of little white and brown bulbs.

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There they are as snug as peas in a pod, thousands of them, in every direction as far as you can see.

And besides these bulbs, there are thick, fleshy root stems, red and brown and yellow, everywhere and everywhere. Do you want to know who they are?

They are our little friends of the early summer,—snowdrops and crocuses and spring beauties and dogtooth violets; mandrakes, too, and Jack-in-the-Pulpit.

These bulbs and thick roots are full of plant food; and this is where the plant has gone to. It has curled up, so to speak, in these bulbs and roots and gone to sleep till next spring. Then it will wake up. It will hardly wait for the snow to go off before it pushes out a bud. The snowdrop does not wait, but sometimes blossoms right under the snow. In a few days the woods that looked so dead and bare are as gay as you please. That is because the plants sleeping in the bulbs and thick underground stems have waked up. They have eaten the rich food stored up there and have grown like magic. Up into the sunshine they spring; they wave sweet flowers; they call the little insects that have ventured out to come and taste their nectar and bring them pollen.

Their leaves are green and delicate, but they work hard, for the plants have used up the food in the bulbs or in the thick underground stems, and the leaves and roots must make new bulb material or store away more food in the thick underground parts.

It is spring, and the air is moist and warm. It rains often, and the plants have all the water they need.

What fun it must be to come out in the world! What joy to unfold bright flowers in the shadowy woods! They dance on their stems and ripen their seeds; before the slow roses have thought of opening their eyes, the bulb people and the underground-stem people have done all their work of growing. The seeds are ripe and ready to be scattered; new bulbs are packed full of plant food, and fresh food is stored in the thick underground stems. The bulb people and the underground-stem people have had a good time.

They were up early in the summer and saw the sweet, fresh world; their leaves worked hard, and their work is all done now.

They are tired and want to sleep. They fear the heat and dryness of the summer. They do not want to be crowded by the other plants that are beginning to look out everywhere.

“We will go to sleep and let the other plants have our places; we have had our share of the air and the water and the dear sunshine,” they seem to say. “We have caught the sunbeams and stored them away in our bulbs and roots, and we will now rest.”

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So they go to sleep. They open the channels from the leaves to the bulbs and the underground stems, and then all the living part of the leaves passes quickly down into the part that lies underground. There is only left the hard framework of the leaves. This is not alive; it never was alive. The living part of the leaf built it for a house to live and do its work in; now the house is empty: the living part has run down into the bulb or the underground stem. The part of the leaf that is left soon falls to pieces, as any old abandoned house will do. It falls on the ground; the rain soaks it, and it crumbles apart. It changes into food for other plants. It is not lost; it is taken up by other plants and again built into good plant material.

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So it is with the seed-pods; when the seeds fall out, the part that is left behind is not alive. All the living part has gone out of the dry pods down into the bulbs or the underground stems; and the pods, too, crumble to pieces and make good food for other plants.

But the seeds are alive. They lie in the earth and wait for the time to come when they may wake up and make new plants with young bulbs or thick underground stems.

But how about the roses? Do they not die in the fall? Why, what are you thinking of? Do they not wake up next spring and cover their stems with leaves and flowers? Dead bushes could not do so.

You see how it is. The leaves work all summer long. They store up food in the roots and the stems. When the frost comes and pinches them, they know it is time to stop work and go to sleep for the winter. They have roots down in the ground. And now you know as well as I do how they manage it.

When the leaves have done their work and fed the flowers and the stems and the seeds, and when the stems and the roots are stored full of food, the leaves stop working. The green little cells that made them so bright all summer go away; the living part of the plant and the rich juices find their way into the roots and stems. Only the dead frames of the houses that the living parts of the leaves built in which to do their work are left. They are dry and lifeless; they never were alive. The living protoplasm has left them and unhinged them so that they soon fall off.

You know what becomes of them. They change into a great many substances. The little particles in them let go of each other and unite with other particles. In this way gases are made which go out into the air, but some parts are solid minerals which the roots took out of the earth to build the frame of the leaves. All these minerals fall back into the earth for the roots to use again next year.

So you see the leaf frame simply changes back again into the gases and minerals of which it had been made by the leaves and the roots.

As the protoplasm withdraws from the leaves of the rose bushes and of many other plants, particularly the trees, the resting time of the plant is announced by the most brilliant colors, the result of certain changes going on within the leaf. These bright colors that make our autumn woods so entrancing are not dependent upon the frost, as many think, but upon certain changes going on within the leaf itself as it ripens, just as fruit, when it ripens, takes on glowing colors. The bright autumn leaves are ripe leaves getting ready to fall. Why do you suppose leaves fall? It is better that they should; the sooner they fall, the sooner they will be converted into leaf mould to feed other plants. So the plants have a way of gathering their ripe harvest of leaves.

The falling of the leaf is not an accident, nor is it dependent upon the wind; when the time comes, the leaves go down, wind or no wind, though doubtless the wind helps them. When they are fully ripe, the leaves let go! The cells that connect the leaf stem with the branch shrivel and shrink until the leaf is entirely separated from the parent plant; when this happens, the leaf falls. The ripe leaf is less juicy than the young leaf; its juices have departed and left the stiff, lifeless framework and the hardened skin, with the emptied cells beneath, to find their way to the earth.

But while the trees and bushes, the bulbs and underground stems store away the living part of the plant, what about the morning-glories and nasturtiums? They do not send their living part into roots or stems, for they do not grow again another year. What now becomes of them?

They die, you say. I do not say that. I say they change. Of course the seeds live on. The morning-glory seeds, and the seeds of all the plants that grow wild in a climate like ours, are not hurt by the cold.

You very well know that some of the life of the plant is folded up in the seeds. But the vines and leaves seem to be hurt by the cold. They fall limp to the ground. They change. The little particles of which they are made let go of each other; they unite with other particles in new ways. They float off in the air as gases.

These gases are carried about by the wind and meet new plants, which build them into their leaves and stems.

Part of the particles in the frosted vine do not become gases; they let go of other particles and sink down as minerals, to be taken up by plant roots another season. Other parts lie on the earth in the form of rich vegetable mould, which is also taken and built into new plants. So when our morning-glory or nasturtium vine disappears, it is not lost; it has only changed its form.

Instead of being a nasturtium, its particles may find themselves built into a dozen different plants.

So what we call death is only change. Not an atom of any plant is lost.

Besides, if no plants changed back again into gases and minerals, there could be no growth and no flowers in the world. There would be no material to make new plants, and no room for new plants to grow.

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There would be no room for seeds to sprout and no need of seeds, so the plants, which never do anything that is not necessary, would not make any seeds; and if there were no seeds, there would be no flowers. What a dreary earth it would be if plants never changed—if they never, as we say, died! The same old plants living forever,—no flowers, no opening buds, no tender spring green, no bright autumn colors.

It is good that the plants die, or change, as I prefer to call it.

NOTHING BUT LEAVES.

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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.

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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.

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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.

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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.

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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.

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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.

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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.