GEOLOGY AND GEO-BOTANY OF ASIA. 71 



regions in the Caucasus lately made by Russian botanists, who have 

 shown that the Pontic range (that is, the border-range of the Armenian 

 plateau) is an extremely important botanic boundary, or the remarks 

 of M. JNTovitskiy concerning the flora of the Karakoram plateau. 



The immense region which is usually represented on geo-botanic 

 maps under the name of Eur- Asian boreal region, and which is bounded 

 on the south by a line traced from the Black Sea to Lake Baikal and 

 thence to the Upper Amur and to the Sea of Okhotsk — this region has 

 not the uniformity which one would be inclined to attribute to it by 

 considering the map only. While it is quite certain that plants easily 

 spread from west to east — from Eussia to the lowlands of western 

 Siberia — they spread also with the same facility from the southwest to 

 the northeast along the high plains, the alpine zone, the border-ranges 

 and the plateau itself. Consequently, the flora of Siberia itself can 

 already be subdivided quite naturally into a number of distinct regions 

 running southwest to northeast, and not west to east. Thus we see, 

 for instance, the cedar- tree (Pinus Cernbra) spreading along the highest 

 parts of the northwestern border-range of the high plateau, from the 

 Altai to the Lena. We find again the same vegetation on the high 

 plateau in northwestern Mongolia, round Lake Kosogol and the Upper 

 Vitim. The vegetation of the high plains of the Altai offers again a 

 great analogy with the vegetation of the high plains in the west of 

 Lake Baikal (the Minusinsk flora being an intermediate link between 

 the two), and the Transbaikalian flora in the east of the Yablonovoi 

 has very much in common with the flora of the Gobi. 



As soon as the Amur emerges from the high plateau, in which it 

 has excavated a deep valley, we find on its banks representatives of the 

 Chinese and Japanese flora under the very same latitudes where we 

 find the Siberian flora further west. And it appears from recent ex- 

 plorations that even round Lake Balkhash, and at the foot of the Tian- 

 shan, vestiges of the European- Siberian flora have maintained them- 

 selves on the best-watered slopes. The lines of propagation of plants 

 along the degrees of latitude are thus completed by lines of propagation 

 having an oblique direction, from southwest to northeast. 



The next zone which is marked on our botanical maps is the zone 

 of the Steppes, which spreads from the prairies of south Eussia through 

 the Aral-Caspian depression and the middle parts of the high plateaus. 



Western and eastern Asia, including various separate desert regions 

 (the Han-hai, the Gobi, the dry parts of Inner Arabia, of Persia and 

 of northwest India). However, this immense region ought to be sub- 

 divided, for central Asia alone, into at least four distinct regions, 

 namely, the Aral-Caspian flora, the Tian-shan, the Tibet and the 

 Mongolian flora. 



The flora of the regions situated on the east of the high plateau, 



