Of course, the plants do not really know anything. Still they usually act wisely; and that is practically just as good as knowing, and often looks very much like it.

For instance, one sees little pine trees growing in a pasture. Each year they send up a “leading shoot” a foot or more long, straight up into the air, to become by and by the main trunk. Each year, also from the point where the trunk ended the year before, there starts out a whorl of little branches, a half dozen or so of them, some of which will by and by become the main limbs. It is the same way with the firs and spruces. If you haven’t seen these growing out of doors, you have at least had them for Christmas trees in the house.

When these little trees grow in the pasture, pretty soon a cow comes along and eats off the top so that there is no longer any leading shoot to grow up into a trunk. What does the tree do then, but pick out one of the side branches from the uppermost whorl, and turn that up into a new leading shoot. So the tree gets a trunk in spite of the cow. Somehow or other, nobody understands how, one of those green tufts which was meant to grow into a horizontal branch, changes its mind, turns up, and becomes the vertical trunk.

This may happen five or six times to a single tree—for when it isn’t cows, then it’s wind, or insects, or something else, that kills the bud that ought to grow up into the main trunk. So one finds often in the woods, trunks of evergreen trees that grow up straight for a few feet; then take a sharp turn to one side, and another straight run of trunk; then another turn. Each of these turns means that something has happened to the leading shoot, and that the tree, like a very wise vegetable, has at once made another leading shoot out of a side branch. But still the curve remains to show where the branch had to change its mind.

It certainly is most clever of the tree. I for one, should like much to know how that side branch finds out that something has happened to the leader, and that it must step into the gap; and how the tree decides which side branch it shall be that is to make the change. Sometimes, indeed, the tree doesn’t seem to be able to decide, so that two branches turn up instead of one; and after that, the tree has a double trunk. Sometimes, too, when the leading shoot is weak but still alive, a side branch turns up; and if the leader recovers itself and grows up strongly again, there will be here also a double trunk; but in such a case, one trunk will grow up straight, while the other starts out with a turn. So the tree sometimes makes a mistake, just as we all do. But it almost never makes so bad a mistake as to have three branches turn up into trunks, tho as far as numbers go, it might have six.

Another matter that all plants seem to understand is the difference between up and down. At least they never make the mistake of sending their roots into the air and their stems down. You recall the bean plant that is inside the bean, with its little root and its tiny stem and leaves tucked snugly away between the two big seed-leaves which are most of the bean. You may plant the bean any way you like, right side up or wrong side up, point the stem up and the root down, or the stem down and the root up, put the bean flat on its side, even plant it in one position for a while and then dig it up and turn it over to another. It makes no difference what you do; that little stem will twist round and grow up, and the little root will twist round the other way and grow down, tho each has to travel half way round the bean to do it. Somehow every seedling does tell which from t’other.

Now the question is, does the plant grow up because up is up, or because up is toward the light? The matter is easily settled. If we plant a seed in a pot, pack the earth in solidly, put a screen over the surface to keep the earth from falling out, and then tip the pot upside down then if the stem wants to grow up it will have to grow away from the light, and if it wants to grow toward the light it will have to grow down. Thus we shall find out whether the plant goes by light-and-darkness or by up-and-downness.

As a matter of fact, while nearly all plants are influenced by both, for young seedlings just getting their start in the world, the question of up and down is much the more important. So a seed planted in an upside down pot, will grow its stem up into the dirt, and its roots downward into the air.

So a plant knows in a way, up from down, as indeed it must, else a tree would not be able to send a tall trunk straight up into the air. Besides, when a tree happens to get uprooted, and yet lives, the new part of the trunk which grows after the accident, does not continue the direction of the old fallen portion, but turns and grows straight up. You can see this sort of thing almost anywhere in the woods.

The plant also, in a way, knows which way the light is falling on it. Commonly, as everybody is supposed to know, the plant grows toward the light. Yet the curious thing about it is that some parts of some plants always grow away from the light. The leafless runners of the strawberry geranium grow away from the light; but when they begin to form leaves on their ends, then they change and grow toward the light like other plants. The tendrils of many vines also, always grow away from the light, while the leaves and, stems are growing toward it. The reason is that by turning away from the light, they turn back toward the rock or tree trunk or wall or trellis which gives them support.

Thus the plant, that seems to know two things, is twice as well off as the infusorian that knows only one.