Part 23 (1/2)
”First, we will go over the life history of a plant, and then I'll tell you of this magic and how to work it. Or better yet my a.s.sistants here, Josephine, Miriam and Ethel, will do the trick.
”A plant really goes through much the same operations in life as does an animal. Only to be sure, these operations are performed in a rather different way. A plant has a digestive, or feeding, system, a breathing apparatus, the power to rid itself of waste and to make seed; it moves, and it grows, too. Philip looked a bit skeptical when I said it moves.
Well, it does. Of course, a plant does not walk about, and move from spot to spot. But a plant can and does move. Why it can turn itself around back to, even. Just look at my geranium slips there! they seem to be breaking their backs to peep out of the window and look at their best friend, the sun. Turn all of them around, George. See, they face us now!
remember to look at them next Friday.
”But to start over again. A plant has just three necessary and important parts: these parts are the roots, stem, and leaves. No, Elizabeth, the fruit and flowers are not separate parts. Why? Well, merely because by some queer provision of the plant world, the leaves are responsible for making or forming both the flower and the fruit. If you watch a bud form and unfold, you will notice that the entire little bud seems to be a series of leaves. And if your fingers were clever enough you could take tiny leaves and fold them into the parts which go to make up the flower and the fruit. This last, like most of the rest of that I am telling you, is just one of the miracles of nature.
”The root, rootlets and root hairs all go to make up the root-system of a plant. This system is a feeding and food storage system; cold storage, we might call it.
”I have spoken before about how the root hairs absorb food. Food is soaked up something as a blotter soaks up ink. Underground plant food must be liquid in nature. This is because plants, like babies, must have very dilute food. Plants can no more get food out of a dry lump of soil than a little baby can get its food from a hunk of bread or a thick slice of corn beef. But let that soil be water-soaked, and have the proper bacteria at work, and the material is in plant-food form.
Josephine has here an old, old experiment. What was a white pink is now a red one. It has been in that gla.s.s of red ink and a little water. And lo, up the stem the red fluid climbed until it suffused the white flower and made it red. Notice as Miriam holds that lump of sugar only just touching the surface of the water, the water moves up that lump. In this way water and liquid food rise up the stems of plants. Just so, too, water rises in the soil from the lower layers up to the feeding place of the roots, and even up to the surface of the ground.
”As the roots are feeding and storing places, so the stem is a sort of pa.s.sage way for the pa.s.sing back and forth of liquids. Take a stem of a big plant, like an oak tree, and you see in the wood where storage of fibre has gone on. But the great work is that of interchange.
”Leaves are very active portions of the plant. They represent a great, busy manufactory. Manufacturing what? That question I see stamped on Myron's face so plainly he need not speak it out. Manufacturing real food out of raw material--that is the work of these plant shops.
”Let me tell you about this. Ethel has in her hands two little plants.
The one in her right hand has been growing in the light; the other, in her left hand, has been put away in the dark to grow. The absence of green colour is very marked in this latter plant. So you see it takes light to form this green, or chlorophyll as it is called. The chlorophyll-saturated cells, absorbing carbonic acid and the water-diluted food from the soil, literally break them up. And when broken, food is found suitable for plants to absorb. Wonderful, is it not?
”I spoke of carbonic acid; well, this is a gas, as some of you have found out before, made up of carbon and oxygen. It is a gas which we of the animal kingdom breathe out as waste from our bodies. The plant takes it in through the leaf--and, by the way, I ought to explain that. It is this way: if we had a magnifying gla.s.s we should find over the inner surface of leaves, pores, or stomata as they are called. They open in the presence of light; and from these openings what the plant has no use for pa.s.ses out, and gases from the air may pa.s.s in. Some call these openings breathing pores.
”Quant.i.ties of water pa.s.s out through these pores. When this process goes on too rapidly a plant will wilt.
”So, to go back, we will suppose that carbonic acid gas has pa.s.sed into the leaves. Straightway the chlorophyll bodies get to work. The gas is broken up, and oxygen and carbon are left. The carbon is wood the plant builds. Some of the oxygen pa.s.ses out into the air and some is kept for plant food use.
”It is a good thing for us that some of the oxygen does escape into the air for we need it. So you see we, in our respiration, and the plant, in its breathing, are doing each other a good turn.
”Of course, there is the dilute food from the soil, which is largely mineral matter and water. The chlorophyll bodies work away on these minerals, and make them into foods. A great body of water, as I have said before, pa.s.ses out of the plant through the stomata.
”I have told you a thing that the plant can do which we are not capable of doing. A plant takes a mineral and makes it over into food. You and I, unless we happen to be circus gla.s.s-eaters, are not built to do this work. But the vegetables which we eat do the work for us.
”A great deal of plant food is in the form of sugars and starches. I remember Katharine and Peter told me last winter that in their physiology they learned how sugars and starches were made in our own bodies. And lo and behold, the geranium can do a similar thing.
”Some plants store up lots of starch, as the potato. Others store quant.i.ties of sugar, as the Southern sugar cane and the beet. Wonderful?
Well, I guess it is. If we could hear and see all the work these energetic little chlorophyll bodies are doing, we should be amazed.
”You will remember that I told you some plants could take the very necessary chemical nitrogen from the air; most of them, however, must get it from the soil. And so again this from the soil solution is worked over into available food.
”After all we must not fail to see that water is most important. It floats all the important food elements to the leaves for the work to be done there. The food carbon, of course, is an exception to this rule and I will say again in certain cases nitrogen is, also.
”Thus you boys and girls now understand how necessary it is that a soil should be of the right texture to hold water. If it is not, it must be helped to be so. Sand, you will remember, had to be doctored to hold water. Clay needed treatment in order to make it quit its bad habit of baking out.
”Here is a rather interesting experiment set up by Josephine and Ethel.
Look at the first piece of apparatus--a tumbler partly full of water, a piece of cardboard over the top of the tumbler, and pa.s.sing down through a hole in the cardboard a piece of plant just stem stripped of leaves, and finally a second tumbler clapped over the first. The second piece of apparatus is exactly like the first, only that the stem, one end of which is in the water, has leaves on the other end. Notice that the upper gla.s.s in the second case has moisture on it. The upper tumbler of the other set is perfectly dry. Whence, then, came the moisture? It must, of course, be the leaves which gave it off, since they represent the only difference in the two pieces of apparatus.
”I wish we might go on with whole sets of experiments, but for that we have not time.
”You understand a little of the mission of root, stem and leaf. The root does a good work in holding a plant in place. It is the foundation material of the plant. There is much, much more to be learned about all these subjects. This little is just to open your eyes to the wonders of the work each plant is performing all the time.