Fig. 2. Jar A contains lime-water through which human breath has passed. Jar B, lime-water through which ordinary air has been pumped for the same time. Note how much greater is the milky deposit in A than in B.
The giving out of carbonic acid gas is one of the most characteristic things about animal breathing, and we can show that plants in breathing give out this gas too.
To prove this, take another jar with a well-fitting cork, and put some beans and peas, which are just beginning to grow, into it, with a little damp blotting-paper to keep them sufficiently moist. Leave the jar closed for a day or two and then open it and quickly and gently pour in some lime-water. Put the lid on again at once and shake it up. You will find that the lime-water turns quite milky, showing that the same waste gas is given out by the plants as was given out in your own breath.
These experiments show us that plants breathe in a part of the air, and also breathe out some of the same waste gas which is given off by animals in breathing. So that we have found that plants do breathe.
Now to go to the other signs of life. I think you will hardly need to do any special experiment to show that seedlings grow into big plants, you must have seen it so often for yourself in the woods and fields and gardens.
We have still to show that plants eat and move, but before we can do this properly, we must learn a little more about the parts of the bodies of the plants themselves, for they have quite a different set of organs to those we are accustomed to in animals, and their way of eating is so different from that of animals that we cannot understand it immediately.
CHAPTER III.
SEEDS AND SEEDLINGS
If we wish to follow the whole life of a plant, we cannot do better than begin by watching the baby plant “hatching” out from its seed at the beginning of its active life.