56 



is said to grow here. These latter species indicate that "Ta- 

 kyr" is also closely related to the Clay-desert. 



From what has been said about the Salt-deserts, we 

 can deduce the following characteristics of the formation: it 

 consists of annual or perennial Halophytes of which a few 

 are dwarf-bushes, very few are bushes (Tamarix) and none 

 are trees. The plants grow scattered on a very saline soil. 

 There is no spring flowering period but all the plants vege- 

 tate throughout the summer or, at least, far into it. This 

 last feature I regard as the chief distinguishing characteristic 

 between this formation and the Clay-desert. 



The formation does not fall in w r ith GRISEBACH'S Salt- 

 steppe or BORSZCZOW'S Salt-desert both of which occur to some 

 extent in the Clay-desert. This is indicated by the fact that 

 both authors mention trees and bushes as constituents of 

 the vegetation. 



CHAPTER 7 



The formation of the Clay-Deserts. 



Clay-deserts are distinguished here as areas which have 

 a clay substratum, and which do not contain salts to the 

 extent that they to a greater amount come to view on the 

 surface. This concept is to some extent identical with "The 

 area of the Clay-deserts" in BORSZCZOW, but parts of his 

 Salt-desert also belong here. ANTONOW'S formation of the 

 "Loess-steppe" belongs here, likewise "the Clay-desert" with 

 the exception of the saline places, which are here classed 

 under the preceding formation. 



According to many authors, Clay-deserts are very ex- 

 tensive in the lowland of Transcaspia (comp. BORSZCZOW above 

 p. 25, and ANTONOW p. 32), and RICHTHOFEN regards them as 

 "the true normal steppes of Central-Asia". 



The soil of the Clay-deserts differs from that of the 

 Salt-deserts by its greater dryness. When these two forma- 

 tions are found together, the Salt-desert always occupies the 

 deeper parts. The saline ground- w r ater cannot diffuse up to 



