GRASSES OP IOWA. 15.7 



ations, not only in the texture of the grain but in the fruit, leaf, 

 stalk and ear. All of the varieties are marked by certain 

 peculiarities. 



WJieat. — This important cereal assumes important changes 

 under diiferent climatic conditions, but less so than cjrn. 

 Major Hallet* has shown that some varieties are quite con- 

 stant. Metzg^rf states that a variety of wheat which was quite 

 constant in Spain, assumed its proper characters only during hot 

 summers. Another variety, when cultivated in Germany, 

 became more constant only after twenty-five years of cultiva- 

 tion. 



The most northern extension of wheat is obtained in Norway, 

 according to SchueblerJ, at 64*^ north latitude. Schuebler 

 further states that under favorable conditions summer wheat 

 may ripen as far north as 68^ 28'. At Skibotten this cereil 

 was sown May 9, 1870, germinated on the 23d, and ripened 

 on the 30th of August, therefore requiring 113 days. The 

 mean temperature for May was 41.2'^ P.; June, 55.6*^ F. ; 

 July, 55.6° F.; August, 55.1° F. 



Winter wheat does not mature because of the long period 

 that the ground is covered with snow. The lowest southern 

 latitude at which wheat is grown is at Chili in the Chilian 

 colony, Punta Arenas Magellanes. The chief zone in which 

 wheat occurs is in the north and south temperate zones. In 

 tropical regions the temperature is too high to allow the proper 

 development of wheat. This is shown very nicely in the tables 

 presented on a preceding page. In regard to the Uuited 

 States the success of the culture of wheat is very materially 

 affected by the long warm and hot months. Thus the southern 

 United States is not a wheit growing country because of the 

 rankness and vigor of the vegetation. This causes an undue 

 amount of rust. Where the culture of wheat is successful in 

 the warm regions, especially the southern parts of the tropical 

 regions, its culture must be carried on during the winter months. 

 According to Royle§, it succeeds best from October to Mirch, 

 and in the sub-tropical zone from November to May. Wallace! 

 in his work on India states that it flourishes best where the 

 supply of sunlight is abundant, yet it is in regions of moderate 



♦Gardners' Chronicle. Darwin. Animals and plants. 1 : 332. 

 tGetreidearten 66. 91. 92. 116. 117. 

 *Dle Pflanzenwelt Norwegens. 75. 

 §Royle. lUustr. Bot. of the Himalaya. 418. 

 Illndlaln 1887. S47. 



