— 48 — 



has not been greatly transformed by the vegetation, and 

 which is rich in sulphates and chlorides. 



The vegetation provides a further difference between the 

 steppes of southern Russia and the Transcaspian deserts. 

 Without entering into details on the vegetation of the steppes, 

 we may take for instance Gruner's description (p. 106) which 

 states that during summer and autumn a large proportion of 

 non-xerophilous or only slightly xerophilous plants appear 

 [Melilotus, Marrubium, Teucrium, Chenopodium, &c.). In Trans- 

 caspia the summer and autumn types of vegetation are quite 

 distinct, as will appear from the following chapters. 



The same has been pointed out by Krassnow (1899), 

 namely that the plants of the desert have a special organis- 

 ation which enables them to endure the severe drought. (He 

 says this without any reservation although the ephemeral 

 plants might well be taken as exceptions.) Steppes on the 

 contrary are covered by a grassy vegetation not specially 

 adapted to droughts, and therefore liable to be scorched. As 

 a further disparity between desert and steppe, Krassnow points 

 out that the former cannot produce crops except with the aid 

 of irrigation whereas the steppe can. Both are devoid of 

 forests. 



It seems moreover to be of importance that trees are 

 absent from the steppes (the grass-steppes), while the desert- 

 vegetation in a considerable degree is characterised by trees 

 and bushes. This was also pointed out by Grisebach (1872, 

 I, p. 400). His view was, that desert is not a scientific defi- 

 nition but means "uninhabitable places", and, as already 

 stated (p. 45), he included all formations under "steppe". His 

 opinion is that the different forms of steppe are not caused 

 by climatic conditions but originate in the soil. Where there 

 is clay near the surface the water from precipitation does 

 not penetrate deeply so that grasses and herbaceous peren- 

 nials can live, and we find a grass-steppe. But where sand 

 stones and rocks attract the water to greater depths, we 

 have a desert, which is richer in ligneous plants than the 

 grass-steppe, because their roots go down deeper. In the 

 desert the surface consists of permeable strata. 



Apart from the fact that the desert is certainly depen- 



