Part 3

You know when you are very warm, you feel a moisture come on your skin. That was once water in your blood. It creeps out through tiny pores over all your skin.

The plant skin has such pores. The water goes off through them. When the plant breathes out this water, then more hurries up through the cells to take its place. So the sap keeps running up and down all the time.

Plants not only send out water through the pores of the leaves, but also a kind of air or gas. If they did not do that, we should soon all be dead. Can I make that plain to you?

Did you ever hear your mother say, “The air here is bad or close”? Did you ever see your teacher open a door or a window, to “_air_” the schoolroom? If you ask why, you will be told “So many people breathing here make the air bad.”

How does our breathing make the air bad? When our blood runs through our bodies it takes up little bits of matter that our bodies are done with. This stuff makes the blood dark and thick. But soon the blood comes around to our lungs.

Now as we breathe _out_, we send into the air the tiny atoms of this waste stuff. It is carbonic acid gas. As we breathe _in_, we take from the fresh air a gas called oxygen. That goes to our lungs, and lo! it makes the blood fresh and clean, and red once more.

So you can see, that when many people breathe in one room they will use up all the good clean air. At the same time they will load the air of the room with the gas they breathe out.

That is why the window is opened. We wish to sweep away the bad air, and let in good air.

But at this rate, as all men and other animals breathe out carbonic acid gas, why does not all the air in the world get bad? Why, when they all use oxygen, do they not use up all the oxygen that is in the world?

Just here the plants come in to help. Carbonic acid gas is bad for men, it is food to plants. Oxygen is needed by animals, but plants want to get rid of it. Animals breathe out a form of carbon and breathe in oxygen. Plants do just the other thing. They breathe out oxygen and take in carbonic acid gas.

The air, loaded with this, comes to the plant. At once all the little leaf-mouths are wide open to snatch out of the air the carbonic acid gas. And, as the plants are very honest little things, they give where they take away. They take carbon from the air, and breathe into the air a little oxygen.

Where did they get that? The air they breathe has both carbon and oxygen in it. So they keep what they want,--that is, carbon,--and send out the oxygen.

Now it is only the green part of the plant that does this fine work for us. It is the green parts, chiefly the leaves, that send out good oxygen for us to breathe. It is the green leaf that snatches from the air those gases which would hurt us.

It is the green leaf that changes the harmful form of carbon into good plant stuff, which is fit for our food. How does it do that? Let us see.

What makes a leaf green? Bobby who crushed a leaf to see, told me “a leaf was full of green paint.”

Inside the green leaves is a kind of green paste, or jelly. Now it is this “leaf-green” that does all the work. The “leaf-green” eats up carbon. The “leaf-green” turns carbon into nice safe plant material. It is “leaf-green” that sets free good oxygen for us.

“Leaf-green” is a good fairy, living in every little cell in the leaf. Leaf-green is a fairy which works only in the day-time. Leaf-green likes the sun. Leaf-green will not work in the dark, but goes to bed and goes to sleep!

In such simple lessons as these, I can tell you only a little of what _is_. The deep “how” and “why” of things I cannot explain. Even the very wisest men do not know all the how and the why of the “leaf-green” fairy.

I have told you these few things that you may have wonders to think of when you see green leaves. After this lesson, will you not care more for seeds and leaves than you ever did before?

LESSON VIII.

THE COLOR OF PLANTS.

Almost the first thing that you will notice about a plant is its color. The little child, before it can speak, will hold out its hands for a bright red rose, or a golden lily. I think the color is one of the most wonderful things about a plant.

Come into the field. Here you see a yellow buttercup, growing near a white daisy. Beside them is a red rose. Close by, blooms a great purple flower. All grow out of the same earth, and breathe the same air. Yet how they differ in color.

Some flowers have two or three colors upon each petal. Have you not seen the tulip with its striped blossoms, and the petunias spotted with white and red?

The flower of the cotton plant changes in color. Within a few days this flower appears in three distinct hues. The chicory blossom changes from blue to nearly white as the day grows warm.

Look at your mother’s roses. Some are white, others are red, pink, or yellow. None are ever blue.

Then look at a wild-rose tree. The root and stem are brown. The green color is in the leaves, and in some of the stems. The petals are red. The stamens and pistils are yellow.

You never saw the red color get astray and run into the leaves. The leaf-green did not lose itself, and travel up to the petals. The stamens and pistils did not turn brown instead of golden.

Does not that seem a wonder, now that you think of it? Perhaps you never noticed it before. It is one thing to see things, and another to notice them so that you think about them.

Here is another fact about color in plants. All summer you see that the leaves are green. In the autumn they begin to change. You wake up some fine frosty morning and the tree leaves are all turned red, yellow, brown, or purple. It is a fine sight.

It is the going away of the leaf-green from the leaf that begins the change of leaf-color in the fall. The leaves have done growing. Their stems are hard and woody. They do not breathe as freely as they did. The sap does not run through them as it did early in the season.

The leaf-green shrinks up in the cells. Or, it goes off to some other part of the plant. Sometimes part of it is destroyed. Then the leaves begin to change.

Sometimes a red sap runs into the leaf cells. Or, an oily matter goes there, in place of the “leaf-green.”

The leaf-green changes color if it gets too much oxygen. In the autumn the plant does not throw out so much oxygen. What it keeps turns the leaf-green from green to red, yellow, or brown.

The bright color in plants is not in the flower alone. You have seen that roots and seeds have quite as bright colors as blossoms. What flowers are brighter than many fruits are?

The cherry is crimson, or pink, or nearly black. What a fine yellow, red, purple, we find in plums! Is there any yellow brighter than that of the Indian corn? Is there a red gayer than you find on the apples you like so well? What is more golden than a heap of oranges?

If you wish to find splendid color in a part of a plant, look at a water-melon. The skin is green marked with pale green, or white. Next, inside, is a rind of pale greenish white. Then comes a soft, juicy, crimson mass. In that are jet black seeds.

Oh, where does all this color come from? Why is it always just in the right place? The melon rind does not take the black tint that belongs to the seeds. The skin does not put on the crimson of the pulp. See, too, how this color comes slowly, as the melon ripens. At first the skin is of the same dark green as the leaves, and inside all is of a greenish white.

Let us try to find out where all this color comes from. Do you know we ourselves can make changes in the color of flowers? Take one of those big hydrangeas. It has a pink flower. But give it very rich black earth to grow in. Mix some alum and iron with the earth. Water it with strong bluing water. Lay soot and coal-dust upon the earth it grows in. Very soon your hydrangea will have blue flowers, instead of pink ones.

Once I had a petunia with large flowers of a dirty white color. I fed it with soot and coal-dust. I watered it with strong bluing water. After a few weeks my petunia had red or crimson flowers. Some of the flowers were of a very deep red. Others were spotted with red and white.

Now from this you may guess that the plant obtains much of its color from what it feeds on in the soil.

But you may give the plant very good soil, and yet if you make it grow in the dark, it will have almost no color. If it lives at all, even the green leaves will be pale and sickly.

This will show you that the light must act in some way on what the plant eats, to make the fine color.

The plant, you know, eats minerals from the earth. In its food it gets little grains of coloring stuff.

But how the color goes to the right place we cannot tell. We cannot tell why it is, that from the same earth, in the same light, there will be flowers of many colors. We cannot tell why flowers on the same plant, or parts of the same flower, will have different colors. That is one of the secrets and wonders that no one has found out.

There are many plants which store up coloring matter, just as plants store up starch, or sugar. The indigo, which makes our best blue dye, comes from a plant. Ask your mother to show you some indigo. When the plant is soaked in water the coloring stuff sinks to the bottom of the water, like a blue dust.

Did you ever notice the fine red sumac? That gives a deep yellow dye. The saffron plant is full of a bright orange color. Other plants give other dyes.

Sometimes children take the bright petals of plants, or stems, that have bright color in them, to paint with. Did you ever do that? You can first draw a picture, and then color it, by rubbing on it the colored parts of plants.

Some trees and plants, from which dyes are made, have the coloring stuff in the bark or wood. That is the way with the logwood tree. The best black dye is made from that.

You have seen how much dark red juice you can find in berries. Did you ever squeeze out the red juice of poke or elder berries? It is like red ink. Did you ever notice how strawberries stain your fingers red? Grapes and blackberries make your lips and tongue purple.

No doubt you have often had your hands stained brown, for days, from the husks of walnuts. All these facts will show you what a deal of color is taken up from the soil by plants, changed by the sun, and stored up in their different parts.

But the chief of all color in the plant is the leaf-green. We cannot make a dye out of that.

Leaf-green is the color of which there is the most. It is the color which suits the eye best of all. How tired we should be of crimson or orange grass!

Though leaves and stems are generally green, there are some plants which have stems of a bright red or yellow color. Yellow is the common color for stamens and pistils. In some plants, as the tulip, the peach, and others, the stamens are of a deep red-brown, or crimson, or pink, or even black color.

LESSON IX.

THE MOTION OF PLANTS.

If I ask you what motion plants have, I think you will tell me that they have a motion upward. You will say that they “grow up.” You will not say that they move in the wind. You know that that is not the kind of motion which I mean.

Some plants grow more by day, some by night. On the whole, there is more growing done by day than by night. At night it is darker, cooler, and there is more moisture in the air. The day has more heat, light, and dryness. For these causes growth varies by day and by night.

Warmth and moisture are the two great aids to the growth of plants. Heat, light, and wet have most to do with the motion of plants. For the motion of plants comes chiefly from growth.

The parts of the plant the motion of which we shall notice, are, the stems, leaves, tendrils, and petals. Perhaps you have seen the motion of a plant stem toward the sunshine.

Did you ever notice in house plants, that the leaves and branches turn to the place from which light comes to them? Did you ever hear your mother say that she must turn the window plants around, so that they would not grow “one-sided”?

Did you ever take a pot plant that had grown all toward one side, and turn it around, and then notice it? In two or three weeks you would find the leaves, stems, branches, bent quite the other way. First they lifted up straight. Then they slowly bent around to the light.

Perhaps you have noticed that many flower stems stoop to the east in the morning. Then they move slowly around. At evening you find them bending toward the west.

This is one motion of stems. Another motion is that of long, weak stems, such as those of the grape-vine or morning-glory. They will climb about a tree or stick.

Such vines do much of their climbing by curling around the thing which supports them. If you go into the garden, and look at a bean-vine, you will see what fine twists and curves it makes about the beanpole.

Such twists or curves can be seen yet more plainly in a tendril. A tendril is a little string-like part of the plant, which serves it for hands.

Sometimes tendrils grow out of the tips of the leaves.

Sometimes they grow from the stem. Sometimes they grow from the end of a leaf-stem in place of a final leaf.

Tendrils, as I told you before, are twigs, leaves, buds, or other parts of a plant, changed into little, long clasping hands.

Now and then the long slender stem of a leaf acts as a tendril. It twists once around the support which holds up the vine. Thus it ties the stem of the vine to the support.

You have seen not only climbing plants, such as the grape-vine. You have seen also creeping plants, as the strawberry and ground-ivy. You will tell me that a climbing plant is one which travels _up_ something. You will say, also, that a creeping plant is a vine which runs along the ground.

The climbing plant helps itself along by tendrils. The creeping plant has little new roots to hold it firm.

Look at the strawberry beds. Do you see some long sprays which seem to tie plant to plant? Your father will tell you that they are “runners.”

The plant throws out one of these runners. Then at the end of the runner a little root starts out, and fastens it to the ground. A runner is very like a tendril. There are never any leaves upon it. But the end of a tendril never puts out a bud. The end of the runner, where it roots, puts out a bud.

This bud grows into a new plant. The new plant sends out its runners. These root again, and so on. Thus, you see, a few strawberry plants will soon cover a large space of ground.

There is a very pretty little fern, called the “walking fern,” which has an odd way of creeping about. When the slender fronds[8] reach their full length, some of the tallest ones bend over to the earth. The tip of the frond touches the ground. From that tip come little root-like fibres, and fix themselves in the earth. A new plant springs up from them.

When the new plant is grown, a frond of that bends over and takes root again. So it goes on. Soon there is a large, soft, thick mat of walking fern upon the ground.

This putting out new roots to go on by is also the fashion of some climbing plants. Did you ever notice how the ivy will root all along a wall? Little strong roots put out at the joints of the stem, and hold the plant fast.

All this motion in plants is due to growth. In very hot lands where there is not only much heat, but where long, wet seasons fill the earth with water, the growth of plants is very rapid.

In these hot lands, there are more climbing plants than in cool lands. Some trees, which, in cool lands where they grow slowly, never climb, turn to climbers in hot lands.

Some plants will twine and climb in hot weather, and stand up straight alone in cool weather. This shows that in hot weather they grow so fast that they cannot hold themselves up. When it is cool, they grow slowly, and make more strong fibre. But we must leave the stem motions of plants and speak of the motion of other parts.

Let me tell you how to try the leaf motion of plants. Take a house plant to try, as that is where wind will not move the leaf. Get a piece of glass about four or five inches square. Smoke it very black.

Lay it under the leaf, so that the point of the leaf bent down will be half an inch from the glass.

Then take a bristle from a brush and put it in the tip of the leaf. Run the bristle in the leaf so that the end will come beyond the leaf, and just touch the glass. Leave it a night and a day. Then you will find the story of the leaf’s travels written on the glass. As the leaf moves, the bristle will write little lines in the black on the glass. Try it.

As you have proved the motion of the leaf with your smoked glass, let us look at leaf motion. There is, first, that motion which unfolds or unrolls the leaf from the bud. That is made because, by feeding, the plant is growing larger, and the leaf needs more room.

The leaf often has, after it is grown, a motion of opening and shutting. Other leaves have a motion of rising and falling. But of these motions I will tell you in another lesson.

Flowers have, first, the motion by which the flower-bud unfolds to the full, open blossom. That, as the leaf-bud motion, comes from growing. Did you ever watch a rose-bud, or a lily-bud, unfold?

Then the flowers of many plants have a motion of opening and shutting each day. I shall tell you of that, also, in another lesson.

Besides these motions in plants, there are others. Did you ever see how a plant will turn, or bend, to grow away from a stone, or something, that is in its way?

If you watch with care the root of one of your bean-seeds, you will see that it grows in little curves, now this way, now that. It grows so, even when it grows in water, or in air, where nothing touches it.

People who study these changes tell us that the whole plant, as it grows, has a turning motion. In this motion all the plant, and all its parts, move around as they grow.

The curious reasons for this motion of plants, you must learn when you are older. I can now tell you only a little about it. I will tell you that the plant moves, because the little cells in it grow in a one-sided way.

Thus the air, light, heat, moisture, cause the cells on one side of the plant to grow larger than the others. Then the plant stoops, or is pulled over, that way. It is bent over by the weight. Then that side is hidden, and the other side has more light, heat, and wet. And as the cells grow, it stoops that way.

This is easy to understand in climbing plants. Their long, slim stems are weak. They bend with their own weight. They bend to the side that is slightly heavier. Their motion then serves to find them a support. As they sweep around, they touch something which will hold them up. Then they cling to it.

Now, there is another reason for a tendril taking hold of anything. The skin of the tendril is very soft and fine. As it lies against a string, or stick, or branch, the touch of this object on its fine skin makes the tendril bend, or curl.

It keeps on bending or curling, until it gets quite around the object which it touches. Then it still goes on bending, and so it gets around a second time, and a third, and so on. Thus the tendril makes curl after curl, as closely and evenly as you could wind a string on a stick.

Some plants, as the hop, move around with the sun; other plants move in just the other direction. It is as if some turned their faces, and some their backs, to the sun.

FOOTNOTES:

[8] What you call the leaf of a fern is, properly speaking, a frond.

LESSON X.

PLANTS AND THEIR PARTNERS.

Did I not tell you that the plants had taken partners and gone into business? I said that their business was seed-growing, but that the result of the business was to feed and clothe the world.

In our first lessons we showed you that we get all our food, clothes, light, and fuel, first or last, from plants. “Stop! stop!” you say. “Some of us burn coal. Coal is a mineral.” Yes, coal is a mineral now, but it began by being a vegetable. All the coal-beds were once forests of trees and ferns. Ask your teacher to tell you about that.

If all these things which we need come from plants, we may be very glad that the plants have gone into business to make more plants.

Who are these partners which we told you plants have? They are the birds and the insects. They might have a sign up, you see, “Plant, Insect & Co., General Providers for Men.”

Do let us get at the truth of this matter at once! Do you remember what you read about the stamens and pistils which stand in the middle of the flower? You know the stamens carry little boxes full of pollen. The bottom of the pistil is a little case, or box, full of seed germs.

You know also that the pollen must creep down through the pistils, and touch the seed germs before they can grow to be seeds. And you also know, that unless there are new seeds each year the world of plants would soon come to an end.

Now you see from all this that the stamens and pistils are the chief parts of the flower. The flower can give up its calyx, or cup, and its gay petals, its color, honey, and perfume. If it keeps its stamens and pistils, it will still be a true seed-bearing flower.

It is now plain that the aim of the flower must be to get that pollen-dust safely landed on the top of the pistil.

You look at a lily, and you say, “Oh! that is very easy. Just let those pollen boxes fly open, and their dust is sure to hit the pistil, all right.”

But not so fast! Let me tell you that many plants do not carry the stamens and pistils all in one flower. The stamens, with the pollen boxes, may be in one flower, and the pistil, with its sticky cushion to catch pollen, may be in another flower.

More than that, these flowers, some with stamens, and some with pistils, may not even be all on one plant! Have you ever seen a poplar-tree? The poplar has its stamen-flowers on one tree, and its pistil-flowers on another. The palm-tree is in the same case.

Now this affair of stamen and pistil and seed making does not seem quite so easy, does it? And here is still another fact. Seeds are the best and strongest, and most likely to produce good plants, if the pollen comes to the pistil, from a flower not on the same plant.

This is true even of such plants as the lily, the tulip, and the columbine, where stamens and pistils grow in one flower.

Now you see quite plainly that in some way the pollen should be carried about. The flowers being rooted in one place cannot carry their pollen where it should go. Who shall do it for them?

Here is where the insect comes in. Let us look at him. Insects vary much in size. Think of the tiny ant and gnat. Then think of the great bumble bee, or butterfly. You see this difference in size fits them to visit little or big flowers.

You have seen the great bumble bee busy in a lily, or a trumpet flower. Perhaps, too, you have seen a little ant, or gnat, come crawling out of the tiny throat of the thyme or sage blossom. And you have seen the wasp and bee, busy on the clover blossom or the honeysuckle.

Insects have wings to take them quickly wherever they choose to go. Even the ant, which has cast off its wings,[9] can crawl fast on its six nimble legs.

Then, too, many insects have a long pipe, or tongue, for eating. You have seen such a tongue on the bee.[10] In this book you will soon read about the butterfly, with its long tube which coils up like a watch spring.

With this long tube the insect can poke into all the slim cups, and horns, and folds, of the flowers of varied shapes.

Is it not easy to see that when the insect flies into a flower to feed, it may be covered with the pollen from the stamens? Did you ever watch a bee feeding in a wild rose? You could see his velvet coat all covered with the golden flower dust.