SOIL RELATIONS 237 



it is commonly agreed that prairie soils have, from a 

 previous indefinite time, been composed of finely divided 

 particles. How far back vegetation began to be con- 

 cerned in their formation is not well established, though 

 Russian writers maintain that it was very long ago, nearly 

 or quite as long as the beginning of the soils themselves. 1 

 As to the formations underlying these soils, they are known 

 to be of the most diverse kinds, ranging in this country 

 from carboniferous to the uppermost tertiary and loess. 

 In the Red River Valley of the northern Great Plains they 

 overlie the deposits of the ancient lake Agassiz. Along the 

 Mississippi River and branches they overlie glacial drift. 

 A similar diversity prevails in the underlying formations 

 of the Russian prairies. As over one third of the small 

 grain of the world, exclusive of rice, is produced in Russia, 

 North America, and Argentina, most of which is grown 

 in the prairie regions, it will be well to state briefly the 

 general characteristics of these areas. 



250. The Russian chernozem. The Russian word, 

 chernozem, is a derivative from two root words, " chernui," 

 black, and " zemlya," earth. It is, therefore, literally 

 the black earth of Russia and Siberia. It coincides, 

 nearly, with the steppe region as distinguished from the 



and Dokuchaev (who was the actual founder of the school), who 

 have been followed more recently by Kostichev, Krasnov, Tan- 

 filiev, and many others. The literature has already reached 

 several hundred volumes. It would be of great benefit to Ameri- 

 can students to have at least abstracts of these publications put 

 into English. 



1 The three distinctions of these soils must be kept in mind : 

 (1) the grass humus (indicating cereal adaptation) with mineral 

 salts, (2) a dry climate, and (3) a summer rainfall. So-called 

 prairies (lowland meadows or marshes) within timbered or 

 humid regions are very different, as are treeless plains with a 

 winter rainfall. 



