roni" wheats have so much sticky material that they are not good for making yeast bread. Can you tell why? 318. What are the Legumes? Legume (leg'yum) is an uncommon word, but it stands for some very common plants. Really, legume is the name of the peculiar pod which forms the seed case for these plants. You have all seen this pod in the case of green peas and string beans, as well as when the pods are ripe and ready to split into their two parts, or valves. The legumes, or leguminous plants, as they should be called, all have two cotyledons in the seed (see § 298). They include such plants as clover, alfalfa, peas, beans, lentils, wisteria, bluebonnet, the locust and redbud trees, and many others. Have you ever seen the beautiful flowers of the redbud in early spring, before the leaf buds of the tree opened? All the legumes have their flowers in clusters. Have you seen any other flowers of the legumes? Of course you have, in the sweet peas at the florist's, even if you have not raised them at home. What is the shape of the sweet pea, and how many sepals and petals has it? You remember that one of the petals is much larger than the others, and stands upright, like a banner, or standard; two of the petals are like wings; while the remaining two look somewhat like the keel of a boat, and form a little box for the stamens and pistil. Do the attractive color and odor of the sweet pea suggest that the plant has need of insects or other creatures? As a matter of fact, the ' keel " of the flower is a special device by which the plant causes an insect which visits it to carry the pollen of one flower to the pistil of another. 66 When we speak of the plants which the farmer raises in his pasture or meadow as food for his cattle, we must not forget clover and alfalfa. These are not grasses at all, but legumes. The clover does not seem to have flowers much like peas and beans, unless you examine them closely; but they are really all alike, except that those of the clover are in a close head. Have you ever examined a clover head gone to seed? What are some different kinds of clover? Does the clover produce anything that is attractive to bees, and causes them to pay it frequent visits? Alfalfa is also called lucerne. It was brought into America from Europe as a forage plant that could be grown profitably in the drier regions of some Western States; but it is now grown in many other parts of the country. Have you ever thought of another common legume? How about the peanut? Open the halves of a peanut: an unroasted one, if possible, and see if you can find the germ. What is it like? Do you know the peculiar way in which peanuts are harvested? They are dug from the ground, like potatoes. The plant produces the flower above ground, but when the pod begins to develop, the plant forces it into the ground to ripen. The peanut is also called a goober. 319. How Do Legumes Capture the Nitrogen? — We have one more very important thing to learn about the legumes. Do you remember that in our study of foods (see §§ 188 and 190) we found that our bodies need some foods containing nitrogen to build up our tissues? The same is true of all living things. Strangely enough, while all plants need nitrogen, the legumes are almost the only food plants which contain it in large quantities. There is a great deal of nitrogen in the air, but plants cannot use it; so when nitrogen is added to a plant's food, it must come from the nitrogen compounds dissolved in the soil, and be taken up by the roots of the plant. Therefore we would expect that as the legumes contain a great deal of nitrogen, and as they must get it from the soil, the ground on which legumes are grown would lose a good deal of its nitrogen. But the opposite is true if a crop of clover, or alfalfa, or beans, is grown upon a piece of land, the land becomes actually richer in nitrogen than before. Men have known for years that growing clover or alfalfa upon soil improved the soil for other plants, but only recently have they learned the reason. If you pull up a half grown clover plant, you will find on its roots little, wart-like growths which are called root tubercles (tū'bĕr-kls; see Fig. 243). Inside the tubercles are multitudes of bacteria of a special kind, which have the power to unite the nitrogen of the air with oxygen and other substances and produce nitrogen compounds. The roots of the clover and other legumes provide homes for these bacteria, and then are able to feed upon some of the nitrogen foods which they produce. The clover, or other legume, does not use all of these foods; hence when the plant is removed, some nitrogen food is left FIG. 243. - A red clover in blossom. Note the tubercles on for the next plant to be grown upon the roots. that soil. Is not this a wonderful partnership between the nitrogen-gathering bacteria on the one hand, and the legumes on the other? This, then, is the reason why the legumes are not only able to live upon a soil that is poor in nitrogen, but to leave the soil richer in nitrogen than it was before. Have you ever heard that farmers often grow clover or alfalfa in a field, and then plow it under, in order that the ground may be more valuable for other crops? Review § 159. By "a vege 320. Why Do We Eat Vegetables? — table" we mean part of a plant which is edible, or fit to be eaten. We have already learned (see § 193) that our common garden vegetables include the seeds, stems, roots, and leaves of certain plants. Thus the sweet potato is a root, while the potato is an underground stem. In the asparagus, celery, and rhubarb we eat the stalk, in lettuce and cabbage the leaves, in tomatoes and cucumbers the fruit, and in cauliflower the flower itself. What vegetables are seeds? We may divide vegetables roughly into two classes: (1) those which we call starchy vegetables; and (2) those which are juicy, or succulent. We eat the starchy vegetables largely because they are good fuel and give us energy (see § 189). We eat the juicy vegetables because they have a pleasant flavor, add bulk to our food, provide the necessary mineral food (see § 191), and give us the important growth substances, commonly called “vitamines." Make a list of the vegetables with which you are familiar, and tell which might be called starchy and which juicy. Do you try to have some of each class every day? Scientists say that three fourths of the American people do not eat enough vegetables. 321. What Fabrics Do We Get from Plants? - We have already learned some things regarding the materials of clothing (see § 181) and of the difference between their fibers. What are the most important plant fabrics besides cotton and linen? They are hemp and straw, are they not? The cotton plant needs a long growing season, so it is grown in regions which combine the right soil conditions with a warm climate. India, Egypt, and our own Southern States have both the soil and the climate. Seaisland cotton is that grown in the low lands of our southeastern coast; it has especially long and silky fibers. Upland cotton is that grown away from the coast. The cotton seeds and fibers are inclosed in a seed case, called a boll. was. The cultivation of cotton on a large scale was made profitable by the invention of the cotton gin (Fig. 244) by Eli Whitney in 1792. Until this machine was invented, the seeds had to be separated from the fibers by hand. You may imagine what a slow and difficult process this But by the use of the gin the process is a rapid one, and the seed, as well as the cotton fiber, has great commercial importance. The reason for this is that the seed contains a great deal of fat, called "cottonseed oil," which can be used as a substitute for olive oil and lard, and for the fats needed in soap-making. To get the oil out of the seed, the seed must be compressed strongly ; what is left is called seedcake, and is sold as food for cattle. When you learn that about two pounds of cotton seed are produced for every pound of cotton, you will realize how important it is that these by-products of cotton-raising shall be put to use. We turn now to linen. Ancient books speak often of linen garments, so we know that the flax plant, from which linen is made, |