the Devonian sandstone territory appears, and the typical stamp of the taiga scenery 

 therefore gradually disappears. The black taiga gradually retreats, and the valley be- 

 comes more open and smooth. 



Southwards from here there appears a successional zonation in the vegetation 

 from the dark, moist taiga to the dry, open steppe land. This transition zone, which 

 is widely distributed over the Urjankai country, I have separated as the wooded 

 steppe region. The transition between the subalpine primeval forest and the wooded 

 steppe region may here roughly be set down at a height of about 800—850 m. 

 above sea-level. In comparison it will be remembered that the primeval forest on the 



Fig. 48. From the middle course of tlie Sisti-kem near Ust Algiac. 



The banks are grown chiefly with cedar, spruce, and also birch. 



About 980 m. above sea-level. 



north side of the mountains might be reckoned to begin about Kushabar, at a height of 

 only 320 m. above sea-level. The forest thus descends considerably lower on the north 

 side. This is also an indication of an average drier climate on the south side of the 

 mountains. 



Further to the south the country becomes successively still drier, even in upland 

 regions. Thus, the Tannu-Ola mountains, forming the boundary of the Urjankai country 

 to the south, and being recorded to average still higher than the Sayansk mountains, 

 are much drier, even in the more elevated tracts. Here the black or moist taiga is 

 altogether wanting, and the ground is dry and treeless right up to the highest ridges, 

 or only grown with scattered, open larch-forest. 



This distribution of the downpour may, I think, perhaps be accounted for by the 

 prevalent winds in these regions being mostly northern, for which reason the moisture is 

 mainly given off on the north side of the mountains"; and the wind blows down the south 



77 



