We have now done a number of experiments with plants, and found out many facts about their way of life, and I think you will agree that we have collected enough evidence to prove the statement made at the beginning of Chapter II.—that on the whole plants show the same “signs of life” as do animals.

We have seen that like animals they breathe in a part of the air, and that they breathe out with the air the added carbonic acid gas, which is the characteristic “waste product” of the out-breathing of animals.

They practically “eat” when they take in substances as food into their bodies, even though they have no gaping mouths which can open and close. We noticed, too, the interesting parallel between young plants and young animals, where both (the plants in the food in the seed, the animals in their mothers’ milk) are supplied with ready-made food at first, and as they get older have to find what food they require for themselves. As regards their feeding, the plants do more work than the animals, for they manufacture the starchy food for themselves out of simpler elements, while the animals require their starch to be ready made.

Then the fact that plants grow, increasing in size and forming new structures, has been known to you ever since you were a baby yourself. Although we noticed here an important difference between the kind of growth in plants and animals, yet the growth itself is alike in the two cases, for both plants and animals build up their living bodies out of simpler substances which they take in as food and change till the not-living food becomes part of themselves and is living.

Movement is not nearly so great in plants as it is in animals, and most plants are firmly fastened in the ground. Yet there are some plants in which we can see very rapid movements of some of the parts, while many simple little plants living in water can swim actively about like animals. All plants show some form of movement, though it is generally slow.

As a result, we find that all the signs of life we noted in animals, viz. breathing, eating, growing, and moving, are to be found in plants, and we must look on them as being just as much alive as animals. We can see that their mode of life and the work they do are distinctly different from those of the animals, but they are no less vital, and important for the world as a whole.