THE BOOK OP WHEAT 



of wheat is the same for all latitudes, and that if these vary, 

 the period of growth will vary in inverse proportion. In sup- 

 port of this position Cooke* collected the statistics given 

 below. 



Cooke found the number of heat units required to be ap- 

 proximately the same for different countries, i. e., about 8,500. 

 Experiments conducted at Fargo, N. D., to verify this failed of 

 their purpose, and gave approximately 6,500 heat units. The 

 period of growth was about 100 days. Recent observations 

 have shown that the number of heat units decreases when the 

 growing period shortens. In general, the growing period is 

 shortest in the coldest climate. 



The Weight of Different Materials entering into an acre of 

 the wheat crop is shown in the table given below. All weights 

 are in pounds. The grain and straw are given as air dry ma- 

 terial, which contains about 15 per cent of water. 



WEIGHT OF MATERIALS IN" AN ACRE OF WHEAT. 



1 Yearbook U. S. Dept. Agr., 1894, p. 174. 



2 Kept. Mont. Exp. Sta., 1902, p. 61. 



3 Evidence of Saunders, 1900, p. 23. 



4 Neb. Bui. 19, p. 15. 



* N. D. Bui. 47, p. 704. 



