Individual plants of the the grass family are more numerous and more widely distributed than plants of any other flowering plant family. There are, however, possibly only one-fourth as many species of grasses as there are members of the Sunflower Family. The flowers of grasses are highly specialized in structure and have a terminology all their own (Fig. 24.25). The calyx and corolla are represented by tiny, inconspicuous scales, and the flowers are protected by boat-shaped bracts. The stigmas, when they are exposed, are feathery, and the leaves sheathe the stem at their bases.
Nearly all of the cereals, including wheat, barley, rye, oats, rice, and corn, belong in this family, which includes nine of the ten most important crop plants in the world. Indeed, civilization as we know it would be vastly different without them. More than 900 million metric tons (1 billion tons) of cereals, feeding more than half of the world's population, are harvested each year, primarily in the Orient, North America, and Europe.
Sugar cane (Fig. 24.26), from which about 55 million metric tons (60 million tons) of sugar is extracted annually, is grown at lower elevations throughout humid tropical areas. It is a large grass, often growing to heights of 6 meters (20 feet). After the cane is harvested, raw liquid sugar is squeezed out by a milling process. The juice then is centrifuged, with the
Stern-Jansky-Bidlack: I 24. Flowering Plants and I Text I I © The McGraw-Hill
Introductory Plant Biology, Civilization Companies, 2003
Flowering Plants and Civilization 481
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