A7 — 
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. 
pel he Riverside-Thickets. 
The outstanding features of the 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 
