94: PRINCIPLES OF STOCK-BREEDING. 



Heller, in describing the variations in maize culti- 

 vated in Mexico, states that the time of ripening varies 

 from " seven months to six weeks." l 



At the North the plant presents a dwarfed ap- 

 pearance, while at the South the stalks are very 

 large, the ears frequently being higher than a man 

 can reach. 



A collection of corn that I made in 18T6, to illus* 

 trate the variations produced by climate, represents 

 many interesting features in the character and distri- 

 bution of varieties. > 



At the North the cob, as a rule, is larger in pro- 

 portion than in the Southern varieties, or in apparent- 

 ly the same varieties grown in the Middle States. At 

 the North the flint varieties are exclusively grown, 

 while at the South they are entirely replaced by the 

 dent varieties. The smallest well-developed ear in 

 the collection weighs but half an ounce, while the 

 largest ear turns the scale at one pound eight and a 

 half ounces. 



The influence of climate upon the distribution and 

 development of wheat is hardly less marked. Samples 

 in my cabinet from British Columbia, Oregon, Canada, 

 Michigan, Russia, Norway, Sweden, and Australia, 

 present marked contrasts in their general appear- 

 ance. 



In North America a mean temperature of from 

 57 to 65, and in England of 60, for the months 

 of July and August, is required for its full develop- 

 ment. 



In 1853 the mean temperature of these months in 

 1 "Patent-Office Report," "Agriculture," 1847, p. 412. 



