IIr' Devonian sinidslonc U'lrilorv appears, and llie typical stamp nt llic taij^a scenery 

 therefore j^radually disappears. The l)iack taiga iiradualiy retreats, and liie valley hc- 

 comes more open and snioolli. 



Southwards from here there appeals a successional zonation in the vegetation 

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

 is widely distrihuted over the I'rjankai country. I have separated as the wooded 

 steppe region. Tlie Iransilion between the sul)al|)ine pi'inic\al I'oresl and the wooded 

 steppe region may here roughly he sil down al a height of about 800—850 m. 

 above sea-level, hi i()nii)arison ii will be icniembered Ihal Hie primeval forest on the 



Fi.i;. 48. From tlie middle course ol' the Sisti kem near L'st .\lgiac. 



Tlie fjanlis are grown cluelly with cedar, s|)riice, and also bircli. 



Atjout 980 m. atjove 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 tiie 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 



/ 1 



