- 47 — 



It will be understood that the Salt-desert is regarded by 

 BoRszczow and Paulsen as a part of Antonow's Loess-desert 

 of which another part together withe Loess-steppe is referred 

 to Clay-desert. The salt-desert of Borszczow is not however 

 the same as that of Paulsen. 



The vegetation of the lowlands of Transcaspia is in my 

 opinion, to be classified under the following natural forma- 

 tions : 



1. Salt-desert corresponding to parts of Antonow's 

 Loess-desert. 



2. Clay-desert corresponding to Antonow's Loess-steppe 

 and parts of his Loess-desert. 



3. Stone -desert. Under this heading are placed not 

 only deserts with stony soil, but also the small, 

 scattered groups of mountains. 



4. Sand-desert. 



5. The Riverside Thickets. 



The outstanding features of tlie formations are sufficiently 

 indicated by the above titles. 



The principal factor which determines the formations is 

 the amount of water. The riversides and the salt-deserts 

 have the moister soil, the clay-desert has the driest, in the 

 physiological sense at least. The physical constitution of the 

 soil also plays a great part especially all that is involved in 

 the difference between sand and clay. Beyond these the life- 

 conditions of the plants in the different formations are still 

 very obscure. 



To the natural formations one should" add the tilled soil, 

 the formation of cultivation, which in this work is left out of 

 consideration. It only amounts to 2 per ct. of the total area 

 (Schwartz p. 576). 



In selecting names for the formations I have avoided the 

 word Steppe. Like Schimper, Krassnow (1899) and Tanfiljew 

 (1903, 1905), I prefer to recognise grass-steppe alone as 

 Steppe (see p. 41). Carbonate of lime is here the dominant 

 salt, the vegetation is on the whole uniform all the year 

 round and has produced a surface layer of dark soil. The 

 desert, on the contrary, is an open formation on soil which 



