CHAPTER LI. 



THE PRAIRIE AND PLAINS SOCIETIES. 



I. Grass-land Formations. 



1041. Types of the grass-land. Grass-land formations are of 

 three general types: ist, Savannas; 2d, Prairies or Meadows; 

 3d, Plains or Steppes. 



1. Savannas. This term is applied to the grass-land forma- 

 tions in warm temperate or subtropical countries where scattered 

 trees or tree-clumps occur. The regions are too dry at certain 

 seasons for the development of a woodland formation and yet 

 not dry enough for the desert type. So grasses make the charac- 

 teristic climatic formation. But there is sufficient moisture and 

 absence of high winds to permit the development of numbers of 

 trees. 



2. Prairie. The prairies (or meadows according to Schimper) 

 are grass formations in the cold temperate regions where there 

 is sufficient moisture to induce a close formation. They differ 

 from savannas in the absence of trees. The high winds and 

 very dry summer season prevent the development of trees. 



3. Plains (or Steppes). The plains or steppes are grass-land 

 formations principally, but usually the formation is more open 

 because of the greater aridity of the climate. See paragraph below 

 on extent of prairie and plains in the United States. 



1042. Extent of prairie and plains region in United States. 

 The prairie vegetation region in North America extends over 

 the arid areas of the austral region east of the Rocky Mountains, 



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