V. 



WHEAT. 



I. CLIMATE. 



109. Conditions of Successful Wheat Culture. — The yield and 

 quality of wheat, and hence its successful growth, agriculturally 

 considered, depend mainly upon these six conditions: (i) 

 climate, (2) soil (including fertilizers), (3) variety, (4) methods 

 of cultivation, (5) liability to disease, and (6) attack of insect 

 enemies. 



no. Effect of Climate Upon Geographical Distribution — - 

 According to the tenth census seventy per cent of the wheat of 

 the United States was grown where the average January tem- 

 perature was below freezing; eighty-five per cent was grown 

 where the average July temperature was between seventy and 

 eighty degrees, and sixty-five per cent where the mean annual 

 temperature was between, forty-five and fifty-five degrees. Too 

 much weight must not be attached to this, as the soil, partic- 

 ularly in respect to its ease of cultivation, has greatly affected 

 the distribution of wheat. Most of the wheat of the world, 

 however, grows in regions of cold winters, although there are 

 some noted exceptions, as California, Egypt and India. Taking 

 the world at large, and including both spring and winter 

 v^ari^ties, wh-eat has a very wide climatic range. Its range of 

 successful culture, also, seems to be constantly extending north- 

 ward, whether through climatic adaptation or from other causes 

 seems less clear. 



III. Effect of Climate Upon Quality. — Localities having 

 widely different climate and soil have their peculiar varieties, 

 which differ somewhat in composition but much more in physi- 



