THE POD BEARING TREES.
Whenever we see blossoms of the sweet-pea type on a tree or pods of the same type as the pea's swinging from the twigs, we may be sure that we are looking at a member of the pod-bearing family, leguminosae, to which herbaceous and woody plants both belong. The family is one of the largest and most important in the plant kingdom, and its representatives are distributed to the uttermost parts of the earth. Four hundred and fifty genera contain the seven thousand species already described by botanists. Varieties without number belong to the cultivated mem bers of the family, and new forms are being produced by horticulturists all the time. This great group of plants has fed the human race, directly and indirectly, since the First Man appeared on earth. Clovers, alfalfas, lentils, peas, beans yield foodstuffs rich in all the elements that build flesh and bone and nerve tissues. They take the place of meat in vegetarian dietaries.
Besides foods, the pod-bearers yield rubber, dyestuffs, balsams, oils, medicinal substances, and valuable timber. A long list of ornamental plants, beautiful in foliage and flowers, occurs among them, chiefly of shrub and tree form.
Last, but not least, among their merits stands the fact that leguminous plants are the only ones that actually en rich the soil they grow in, whereas the rest of the plant creation feed upon the soil, and so rob it of its plant food and leave it poorer than before.
Pod-bearers have the power to take the nitrogen out of the air, and store it in their roots and stems. The decay of these parts restores to the soil the particular plant food that is most commonly lacking and most costly to replace. Farmers know that after wheat and corn have robbed the soil of nitrogen, a crop of clover or cow peas, plowed under when green and luxuriant, is the best restorer of fertility. It enriches by adding valuable chemical ele ments, and also improves the texture of the soil, increasing its moisture-holding properties, which commercial ferti lizers do not.
Seventeen genera of leguminous plants have tree repre sentatives within the United States. These include about thirty species. Valuable timber trees are in this group. All but one, the yellow-wood, have compound leaves, of many leaflets, often fernlike in their delicacy of structure, and intricacy of pattern. With few exceptions the flowers are pretty and fragrant in showy clusters. The ripening pods of many species add a striking, decorative quality to the tree from midsummer on through the season. Thorns give uistinetion and usefulness to certain of these trees, making them available for ornamental hedges.