Of the simple plants of this group the Grass Family, or Poaceæ ([Figure 86]), is the most important, for in it are all our turf grasses, the bamboo and sugar cane, besides scores of others. Over 4,500 species are known, and they inhabit every region of the globe. The steppes of Russia and our Great Plains are predominately grassy; in the wonderful bamboo forests in the tropics are also woody representatives of this family. Certain kinds in the tropics grow as vines, with great hooked spines at the joints, so that nearly every kind of growth-form is to be found in the Poaceæ. All agree in having very small flowers, arranged in tiny spikelets, which are themselves grouped in various ways, although the inflorescence is usually some form of spike, or raceme or panicle. The individual flowers are between chaffy scales, of which several make up each spike. Always the lowest two scales are empty, and the flowers begin in the third from the bottom, or
Fig. 86. Blue-joint grass, a common grass of North America and a member of the Poaceæ. Fig. 87. Wool-grass, a tall swamp sedge popularly but incorrectly spoken of as grass. It is a member of the Cyperaceæ or Sedge family, which have usually triangular solid stems, whereas grasses have hollow round stems.
sometimes even above that. The flower is so simple that there is neither calyx nor corolla, only three stamens and one to three styles. The fruit is a grain and the Poaceæ, therefore, are the chief source of cereals. Wheat, rice, corn, oats, barley, millet, and rye, all come from grasses, and all, except corn, are natives of the Old World. They were grown for countless ages before the discovery of America, when Europeans first saw corn used by the Indians. As they are wind-pollinated, the flowers of grasses produce no honey nor colored petals, and the vast majority of them have no odor. Most of them reproduce, not only by seeds, but by rootstocks, and many of them grow so closely together that they form turf. In nearly all of them the stem is hollow, and in the largest of them, the bamboo, these hollow stems are used as water and sewer pipes, especially in India. An exception to the hollow stem is the sugar cane, from whose solid stem the juice is pressed out, that is the chief source of sugar; and our common Indian corn.