Part 28

These materials are nitrogen, sulphur, and phosphorus.

Nitrogen is the most important, and this the plant gets chiefly through the roots.

Nitrogen is found in the earth combined with hydrogen and other substances. The protoplasm tears to pieces these nitrogenous substances which the roots suck up, and so enables the plant to take the nitrogen.

The other two substances which the protoplasm needs, sulphur and phosphorus, the plant gets partly from the air and partly from the earth.

Sulphuric acid exists in very small quantities in the air and goes in through the stomata, attracted, no doubt, by the protoplasm inside. But other sulphurous and phosphorous compounds are taken up by the roots.

So we see protoplasm is complicated. It contains carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus united in a very complicated way.

Although protoplasm itself is made only of carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus, it can make use of a great many other things. When the protoplasm of certain cells wants to build hard, tough walls, it uses potash and soda or even silica, which you know glass is made of. Just draw a blade of sedge grass through your fingers if you want to feel the silica in it. You will probably cut your fingers, but that will help make you remember about silica. Then the protoplasm uses iron to color the petals and other parts of the plant. It uses magnesia, too, and salt and lime and a number of other materials for building walls or making dyes or something else.

Every material in our own bodies is found in plants, and sometimes the plants have materials that we do not have.

Of course materials are put together differently in plants from what they are in us. When Mother Nature combines her carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus, magnesia, iron, and all the other things to make a plant, she does not go to work as she would if she were going to make an animal.

Just what the difference is it would be difficult to tell, but there is a difference.

Plants contain a good deal of sugar as a rule, and if you remember cloves you will admit that at least some flowers are made of spice, for cloves are the dried flower buds of the clove tree.

Cinnamon is the bark of a plant, and if you are acquainted with orange trees you will be willing to say they are “made of sugar and spice and everything nice,” for the whole tree, wood, bark, stems, leaves, flowers, and fruit, is fragrant and spicy.

Oil is another common substance in plants, and it is made from the materials of starch which, as we know, are carbon, hydrogen, and oxygen; cotton-seed oil, olive oil, and castor oil we are all familiar with.

All nuts contain a great deal of oil, and the skin of a fresh-picked orange is so full of it that it runs down our fingers when we cut the orange.

All the things in a plant—starch, sugar, oils, spices, wood, bark—everything is made by the wonderful protoplasm in the cells.

Starch and the food taken up by the roots pass through all parts of the plant by the sap tubes, and as the sap goes along, each living cell draws into itself the substances from the sap that it needs, and these it combines into the things it wants to make. Some of the cells in an orange skin, for instance, attract out of the sap the materials to make the fragrant, stinging oil that fills the fresh skin, while other cells attract the materials to build the white cottony covering inside the outer skin, and so the cells in each part of the plant take out what they need to build with.

WHAT BECOMES OF THE FLOWERS?

Early in the spring the snowdrops and crocuses peep out, and then they go away.

We do not think much about it, for other flowers have come in their places.

Spring beauties and bloodroots shine in the woods, and then they go away. But the mandrakes have come with their umbrella leaves, and then the columbines and roses ask for a welcome.

After awhile we can find no more mandrakes and columbines, only yellow apples and brown seed-pods.

Jack-in-the-Pulpit jumps up quite early in the summer, and then we cannot find him, only in the late summer we sometimes come across little clusters of bright red berries lying on the ground.

We would scarcely suspect them of having any relation to Jack, yet they are his berries. But what has become of Jack?

In the autumn the rose leaves fall off, and there is left only red stems and red berries.

The morning-glory vine wilts and turns black at the first frost; it sinks to the ground and we see it no more, or else its stems linger brown and hard for a time, but in the end it all disappears. What has become of it?

And the nasturtiums—what a wreck the frost makes of them! The leaves are wilted and black; the stems, too, are soft and lie flat on the ground.

Why, you say, the frost has killed them. But that does not at all tell what has become of them. Besides, the frost did not kill the snowdrops and crocuses and blood roots and spring beauties nor Jack-in-the-Pulpit nor the umbrella leaves of the mandrakes. Yet they are all gone. All we can find of Jack and the mandrakes are red berries and yellow apples. Not a sign of the snowdrops or spring beauties or crocuses is left.

If you will just step down with me under the earth a few inches I will show you something.