— 49 — 



dent upon the climate and not upon the soil, and that its 

 surface in many places consists of impermeable clay, the 

 reasoning of Grisebach has a great amount of truth. Kos- 

 TYTSCHEFF, IsMAiLSKY and Krassnow independently point out 

 the same circumstance in the Russian steppes, that the ab- 

 sence of tree-growth (among other things) is caused by the 

 surface layer of the soil not permitting the water to penetrate 

 into the depths. With reference to Transcaspia, Romanowski 

 states (p. 56) that in layers of gravel under the loess, water 

 is found and is widely diffused under the soil. This may be 

 rain or snow absorbed through sand^), or it may originate 

 from rivers which have sunk into the sand. "Consequently 

 the sand-steppes of Turan cannot be said to be absolutely 

 waterless." 



Here then we have probably the reason — or one of the 

 reasons — why the desert has trees, the steppe none. The 

 presence or absence of trees taken along with the relation of 

 the water to the soil, seem to me so important, that they, 

 together with the climatic conditions and the conditions of 

 the soils, must be regarded as distinguishing characters be- 

 tween steppe and desert. 



For my own part I regard the steppe (grass-steppe) as 

 mainly a closed plant-formation (or group of formations) oc- 

 curring on soil rich in humus without excess of sulphates 

 and chlorides, and with a comparatively moist surface-soil; 

 the vegetation consists of herbaceous perennials, undershrubs 

 and annuals while trees and bushes are wanting. 



The soil of the desert, on the contrary, is devoid of 

 humus or very poor in humus, and contains many sulphates 

 and chlorides. The subsoil is (always?) better supplied with 

 water than the surface. The formations are very open and 

 they frequently include trees and bushes. 



This attempt to explain the terms steppe and desert may not 

 lead to any sharp distinction between the two, so much the less 



^) In this connection It may be pointed out that the steppes of 

 southern Russia have their maximum precipitation in summer so that the 

 water will evaporate quicker than in Transcaspia where maximum occurs 

 between winter and spring. O. P. 



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