CULTURE OF WHEAT 69 



cal characters, such as size, plumpness, hardness and color of 

 grain, length and shape of spike and in length of straw. It 

 seems to be quite conclusively demonstrated that these changes 

 are more closely related to climate than to any other factor. (74) 

 Some varieties of wheat, however, such as Fultz, have a very 

 wide distribution. 



Those localities which have extremes of temperature and 

 rainfall, especially during the ripening period, generally have 

 the hardest and reddest grains and the highest per cent of 

 nitrogen, but are generally less plump and are smaller in size. 

 Wheat of hot, sunny climates, with moderately dry weather 

 during the latter part of growth, is brighter and makes better 

 quality of flour the world over. The United States is particu- 

 lary favored in this respect. 



112. Effect of Climate Upon Growth. — Seelhorst found that 

 a high moisture content in the soil during early growth caused 

 a larger number of spikelets per head, and that a high water 

 content at time of heading increased the number of developed 

 blossoms per spikelet.^ 



A cool, prolonged, but not too wet spring, followed by moder- 

 ately dry sunny weattier during ripening, is most favorable to the 

 largest yield of best quality. The influence of the length of the 

 growing period on the accumulation of plant food and conse- 

 quently upon yield may be illustrated by assuming that a maxi- 

 mum crop reqkiires t^venty-four pounds of nitrates besides those 

 already fu^-n-^d in the soil, and by assuming that throughout the 

 growing s<^,ason four pounds of nitrates per month are produced 

 by the nitrifying agents in the soil. Six months of growth would 

 be necessary to produce a maximum crop. If climatic condi- 

 tions should force the crop to maturity in five months, there would 

 not be enough nitrates to produce a full crop, unless the same 

 climatic conditions influenced the production of nitrates in 

 the soil. The loss of nitrates during wet seasons has been 



1 Jour. Landw. 4.^ (1900), No. 2, pp. 165-177, pis. 2. (E. S. R. XIII (J902), 125.) 



