Although corn is not so essential a staple as wheat, it has a much wider range of usefulness. The starch made from it is considered a delicacy and is used very largely in America and Europe as an article of food. Glucose, a cheap but wholesome substitute for sugar, is made from it; from the oil a substitute for rubber is prepared; smokeless powder and other explosives are made from the pith of the stalk; while a very large part of the product is used in the manufacture of liquor. =Rye.=--Rye is the seed of a cereal grass, _Secale cereale_, a plant closely resembling wheat in external appearance. Rye will grow in soils that are too poor for wheat; its northern limit is in latitudes somewhat greater than that of wheat, also. It is an ideal crop for the sandy plain stretching from the Netherlands into central Russia, and this locality produces almost the whole yield. The world's crop is about one and a half billion bushels, of which Russia produces nearly two-thirds. Germany, Austria-Hungary, and Japan grow nearly all the rest. It is consumed where it is grown. In the United States the yearly product is about twenty-five million bushels, about one-tenth of which is exported to Europe. Rye-bread is almost always sour, and this fact is its chief disadvantage. =Barley.=--Barley is the seed of several species of cereal grass, mainly _Hordeum distichum_ and _Hordeum vulgare_. It is one of the oldest-used of bread-stuffs. It can be cultivated farther north than wheat, and about as far within the tropics as corn; it has, therefore, very wide limits. Formerly it was much used in northwestern Europe as a bread-stuff, but in recent years it has been in part supplanted by wheat and corn. Barley is a most excellent food for horses, and in California is grown mainly for this purpose. Its chief use is for the manufacture of the malt used in brewing. The world's crop of barley is not far from one billion bushels, of which the United States produces about sixty million bushels. Most of the crop is grown in the Germanic states of Europe, and in Russia. =Oats.=--The oat is the seed of a cereal grass, _Avena sativa_ being the species almost always cultivated. It is not known where the cultivated species originated, but the earliest known locality is central Europe, where it was certainly a domestic plant during the Bronze Age. It seems probable that the species now cultivated in Scotland at one time grew wild in western Europe; certain it is that wild species are found in North America. [Illustration: OATS PRODUCTION] The oat grows within rather wider limits of latitude, and thrives in a greater variety of soils than does wheat. Grown in a moist climate, however, the grain is at its best. The oat-crop of the world aggregates more than three billion bushels, surpassing that of wheat or corn in measurement, but not in weight. A small portion of this is used as a bread-stuff, but the greater part is used as horse-food, for which it is remarkably adapted.