Flowers and their friends

by Margaret Warner Morley

CHLOROPHYLL.

Chlorophyll is plant green.

That is what the word means.

We are so used to seeing green leaves that we think very little about it.

It probably never has occurred to most of us that the green coloring matter of plants can be of much importance. Yet it is one of the most important things in the world.

Like many other things, it is not what it seems. It is not merely a dye as one might suppose, but much more than that.

We cannot really see what it is without a microscope, and when we look at a piece of green leaf through the microscope we are surprised to find the leaf is not green at all.

It is colorless like glass, but in the cells just behind the skin cells we see little roundish green bodies packed away. These are the chlorophyll grains, and when there are a great many of them close together they show through the skin and make the whole plant green.

The skin protects them, you see, and yet it is transparent and allows the light to get to them, which is a matter of great importance to the chlorophyll grains, for they are hard workers, but cannot do a single thing without sunlight.

Chlorophyll grains lie just behind the skin cells in all parts of the plant that look green. The cells they lie in are often long with their short ends towards the skin. Leaves contain several layers of chlorophyll cells. The inner ones are not long like the outer ones, and do not contain so many chlorophyll grains. In the illustration, a, a represent the upper and lower skin and b the cells containing chlorophyll. The under side of a leaf usually has fewer chlorophyll grains in its cells, for the light is not so bright there, and chlorophyll needs plenty of light.

Sometimes the cells in the middle of a leaf, that is, halfway between the upper and lower surfaces, have no chlorophyll at all.

Now what do you suppose is the work the chlorophyll grains have to do?

You never could guess, so I may as well tell you at once. If it is not making sugar, it is something very like it. To begin at the beginning, which is a long way from sugar, but which will certainly bring us to it, I must tell you that these little round green chlorophyll people have a strong attraction for carbon dioxide, which you know is a gas and is always found in the air. You know, too, we breathe it out as an impurity. Probably you did not know it had anything to do with sugar, but it has a very great deal to do with it.

The chlorophyll grains attract carbon dioxide as strongly as a magnet attracts bits of iron. The carbon dioxide in the air goes through the pores in the leaf skin, right through everything to the cell where the chlorophyll lies. You know carbon dioxide is made of carbon and oxygen. The plant needs a great deal of carbon, for nearly all its hard parts are made of it. Wood for one thing is nearly all carbon.

As soon as carbon dioxide comes where chlorophyll is, the chlorophyll, which of course is chiefly made of protoplasm, tears it to pieces. It pulls the carbon away from the oxygen and the oxygen rushes out through the pores back into the air. But the carbon stays behind.

You see oxygen is a gas and carbon is a solid. When carbon and oxygen unite in a certain way, they make another gas, our carbon dioxide.

It is very queer that carbon should have the form of a gas when united with oxygen, and I cannot explain it here. You must just remember that it is so.

When the oxygen flies away into the air again and leaves the carbon behind, the work of the chlorophyll has but just begun. Raw carbon is of no use whatever,—no more use than carbon dioxide, which we know is good for nothing to the plant or else the chlorophyll would not tear it to pieces.

But if the chlorophyll can only get a little water, something worth while will happen. This it can always do, as the roots take good care to send it plenty.

Water, you know, is made of two gases, hydrogen and oxygen, united together.

Here, you see, gases unite and make a liquid. Well, chlorophyll has a way of its own of uniting the carbon it took away from the carbon dioxide with the hydrogen and oxygen it gets from the water and forming a solid, which the plant cannot live without.

Now what do you suppose this new solid is? Probably you never could guess.

It is starch, just starch!

Chlorophyll makes starch out of carbon, hydrogen, and oxygen.

Sometimes it makes sugar and oil out of them, but its work is most generally starch-making.

The carbon, you remember, it gets from the carbon dioxide of the air, and the hydrogen and oxygen from the water the roots send it.

The strangest thing about all this is, chlorophyll is the only thing that can make starch.

Perhaps you do not think starch worth making such a fuss about. But wait a moment.

There is more to starch than you ever dreamed of. Really and truly, if it were not for starch you would not be alive to-day, and I would not,—in short nobody would.

All our lives depend upon starch. So when we come right down to the truth, our lives depend upon chlorophyll, because that makes all the starch there is in the world.

You do not think our lives depend upon starch? Wait and see.

Chlorophyll makes starch. Never forget that as long as you live. Forget your own name if you want to, but do not forget that chlorophyll makes starch.

You see starch is the raw material of which plants are made.

After the chlorophyll has made starch, the starch is dissolved, or melted you would likely say, and so is carried all over the plant in the sap. Some parts of the plant change the starch into sugar; for sugar is made of the same things as starch, only in it the carbon, hydrogen, and oxygen are put together a little differently, just as you can make several kinds of cake from flour, butter, sugar, milk, and eggs by stirring them together differently and mixing them in different proportions.

You cannot make cake without flour, sugar, eggs, and milk, and usually butter. But if you have these ingredients you can make a great many kinds of cake.

Starch is the material of which the plant makes a large part of its substance.

Some parts of the plant that need sugar make it from the starch, and we find more or less sugar in all plants. There is, as you know, a great deal in the nectar of flowers, but other parts of the plant need it too, so sugar is a matter of importance to plants as well as to people. But sugar, remember, is made generally from starch, no matter in what part of the plant we find it.

The sweet sap in the sugar maple is made from starch; so is the sweet juice of the sugar beet and of the sugar cane. All the sugar we use, excepting that in homeopathic pills, is made from starch. The sweet juice of fruits, berries, apples, peaches, oranges, contains sugar, which the plant has made from starch. In green fruit the starch has not yet been changed into sugar, so it is not pleasant to the taste.

Some parts of the plant need thick walls, like wood or bark, and these are made by the protoplasm from starch; they are not sugar, however, but a very tough, firm substance so unlike sugar that you wonder how it can be made of the same materials. But it is, for starch is the substance from which both are made.

There are other things in the plant besides starch, and there are things which are not made from starch; for instance, there are acids and minerals of different kinds and there is protoplasm, but the greater part of every green plant is formed from starch.

Some plants make more starch than they need at once, so they store it away for future use, just as people raise extra supplies of wheat and corn, and store them away until they want them.

The potato plant, for instance, stores a large quantity of starch in the potatoes underground. A potato is nearly all starch, and the sweet potato stores up sugar as well as starch in its underground parts.

The potatoes have a reason for this, and, if let alone, would use up the starch and sugar another season; but we do not let them alone, as you know. We too need starch, and so we dig up the potatoes and eat them instead of leaving them for the plant.

A great many plants store up starch in their seeds that the young plant may have food enough to start growing. All our grains do this. Wheat, rye, oats, barley, rice, corn, and all other grains are only the seeds of plants which have been stored full of starch. Peas and beans are also starch-filled seeds. Cabbages store food made from starch in their big thick leaves. Beets store sugar and other starch-food materials in their thick roots; so do carrots and parsnips and turnips. Onions store it in their bulb leaves underground.

You begin to see now how important starch is to our lives. Nearly all the vegetables and grains and fruits we eat are composed almost entirely of starch or the materials of starch. Even meat is made from starch, for what do the animals we kill for meat live on?

Why, plants of course, and chiefly the starch they find in plants.

So now we are just where we started,—we see we really do owe our lives to starch, and we owe starch to chlorophyll, so of course, we owe our lives to chlorophyll. I wonder if we shall think of this next time we look at the green leaves everywhere in the fields and woods.

I wonder if these green leaves will not look more beautiful than ever when we think of the work they are doing.