456 PEACTICAL BOTANY 



In the United States the average annual value of the grain 

 and hay crops for the five years 1903-1907 was as foUowsi; 



Corn 

 Hay. 



Wheat 



Oats 



Barley 



11,132,000,000 



587,000,000 



503,000,000 



293,000,000 



70,000,000 



418. Indian corn. Indian corn is an American plant, well 

 known to the Indians and cultivated by them long before the 

 coming of white people. Its food value per acre is about 

 double that of other grains. 



The United States is the chief corn-raising country, pro- 

 ducing more than three quarters of the world's crop, mainly 

 in the " corn belt " of the Middle West. This region, with its 

 fertile soil, its sunny summers, a fairly heavy rainfall, and a 

 high summer temperature,^ is especially adapted for corn grow- 

 ing. In northern Europe corn is grown in botanic gardens as 

 a curiosity, but does not succeed as a field crop because the 

 summer temperature is not high enough and there is not suffi- 

 cient sunshine. In the Mediterranean region the soil is fertile 

 and the summers are sunny and hot, but the scanty summer 

 rainfall — sometimes less than an inch during three months — 

 affords unfavorable conditions for corn growing. 



The most important types of corn are flint corn, dent corn, 

 and sweet corn. The flint varieties have a large proportion 

 of hard, translucent endosperm. The dwarfed, quickly matur- 

 ing kinds, which can be harvested in ninety days or less from 

 the time of planting, and which are therefore grown in the 

 northernmost states and Canada, are all flint varieties. The 

 dent varieties have much soft endosperm and indented kernels 

 (Fig. 332). The plants sometimes reach a height of eighteen 

 feet or more, and require nearly six months to mature. Dent 

 corn is much more productive, as a rule, than the flint varieties, 



1 See Yearbook, U. S. Dept. Agr., 1907. 



^ Averaging between 70° and 80° F. for the month of July. 



