Part 15

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:

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.”