CEREAL ADAPTATION AND ASSOCIATION 283 



have already come about. The most interesting and most 

 recent case is the segregation of the hard winter wheat 

 district, central in Kansas. 



In North America the directions of climatic resistance 

 are usually opposite to those of Russia. Cereal exten- 

 sion, therefore, finds its greatest obstacles to the west and 

 north, instead of the northeast, east, and southeast, as in 

 Russia. The spring wheat district of the northern 

 plains states and Canada is constantly encroached upon 

 by winter wheat in its northward extension from Iowa and 

 Nebraska, and in Montana and Alberta. Barley is now 

 grown chiefly in the north central and northern plains 

 states, and in California, its production having increased 

 greatly in the latter states. Rye is found in Ontario and 

 the north central and New England states, being em- 

 ployed for hay in the last-named district. Wheat and 

 oats are more generally distributed, but are grown in the 

 largest quantity in the prairie region of the Great Plains 

 and central states, as would be expected (Fig. 82). 



296. Argentina. Climatic -resistance, with regard to 

 dryness, increases to the westward in Argentina as in 

 the United States, but with respect to winter cold, it 

 increases to the southward. The quality of cereals, there- 

 fore, and, within limits, the quantity, increase in the same 

 directions. The Chaco-Pampean Plains, constituting the 

 natural cereal zone, cover the largest part of the Republic. 

 Wheat is the only cereal grown to any considerable 

 extent, but the production of this crop has increased 

 remarkably in recent years. The cereal varieties now 

 grown are those adapted to warm sub-humid regions. 

 There is durum wheat, however, in the drier districts, 

 and a rather hardy winter wheat of excellent quality in 

 Chubut (Fig. 83). 



