Part 14

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 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.