172 PLANTS AND MAN 



from durum and common bread wheats. Durum wheat has 

 thick spikes of grains which are rich in gluten and therefore used 

 chiefly in making macaroni and spaghetti. It is a hardy, drought- 

 resistant variety introduced into this country from Russia and 

 grown in the northern plains states (Minnesota and the Dakotas) . 

 Durum wheats constitute about 6% of the domestic crop (fig. 

 104). 



There are several hundred varieties of the common bread 

 wheat: "hard" varieties have small grains rich in proteins, 

 while "soft" varieties have larger grains rich in starch; "spring" 

 wheats are sowed in spring and harvested in late summer, while 

 "winter" wheats are sowed in autumn, survive the winter and 

 mature for an early summer harvest. Soft winter wheat, used as 

 a pastry flour, comprises about a third of the national crop; it 

 is grown east of the Mississippi and in the Pacific northwest. 

 This was the variety grown in the first American wheat belt, 

 which extended from Delaware and Maryland to New York; 

 it was also brought into the Ohio Valley wheat region. After 

 the Civil War, the ideal wheat-raising country of the plains was 

 discovered, with a temperate climate and not too much rain (over 

 thirty inches annually is detrimental to wheat), and with a 

 suitable clay and loam soil. In the plains states, soft winter wheat 

 is replaced by hard winter wheat and hard spring wheat. Hard 

 winter wheats, constituting about 40% of our domestic crop, 

 are grown in the central and southern plains region (Kansas, 

 Nebraska and Oklahoma); the spring wheats are raised farther 

 north in Minnesota and the Dakotas, and make up about 20% 

 of the annual harvest of wheat. Both these types are used in 

 making bread flour. 



The growing and harvesting of wheat has become a large- 

 scale industry with mechanical aids supplanting hand labor. On 

 the rolling prairies of the midwest, machines plant the seed, other 

 machines weed and plow the furrows; harvesting, threshing and 

 transportation to the storage buildings is done by machines. On 

 large farms the combine is used — a traveling factory which 

 reaps, cleans, threshes, sorts the grain and even leaves it in bags 

 along the forty-foot wide swathe cut by the machine. Some 

 50,000,000 acres of American soil are under cultivation for wheat. 



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