7o POPULAR SCIENCE MONTHLY. 



as also in a few islands of the Bay of Bengal and Arabia, and of western 

 Asia. Numerous extinct volcanoes are found, not only in the same 

 regions, but also in the Caucasus, on the plateau of Armenia, in east 

 Tian-shan, in the northwestern border-ridges of the high Siberian 

 plateau, and in the southwest of Aigun, in Manchuria (the Uyun 

 Holdontsi region). An immense zone of land was covered with 

 basaltic lavas during the early Tertiary period (or Cretaceous?) along 

 the northwestern border of the high plateau of east Asia, and vents 

 through which scoriae were ejected, forming small cones of ejection, 

 are still seen on the Mongolian and Vitim plateaus, as well as in the 

 Sayans. Earthquakes are frequent, especially in Armenia, Turkestan 

 and around Lake Baikal. 



With the rich botanic materials which we are already in possession 

 of, it would be extremely interesting to make a picture of the distribu- 

 tion of the different floras of Asia upon the surfaces of its high and 

 lower plateaus, their border-ranges, the alpine zones, the high plains, 

 and the lowlands. It would then appear how much these orographical 

 divisions can help us to find out the true distribution of floras, which 

 botanists have hitherto tried to bring into accordance with zones that 

 were traced either along the degrees of latitude, or according to the 

 basins of the different rivers, without taking into account the great 

 orographical divisions and the differences of altitude, which mostly 

 run in diagonal directions. Thus, to take only one example, the Great 

 Khingan is the most important botanical boundary which is found all 

 over Siberia and Manchuria. When one crosses this border-range and 

 goes down its steep slope towards the east, one sees that in one hour, 

 or maybe in half an hour, quite a new flora — Manchurian — takes the 

 place of the Siberian flora; and one notices the appearance of trees, 

 which strike even the most ignorant in botany, because these trees have 

 not been seen before, while the traveler crossed Siberia over a distance 

 of several thousand miles. One sees also how the Manchurian flora 

 endeavors to spread westwards along the valleys of the Upper Amur 

 and the Argun. Another important botanic boundary is the escarp- 

 ment of the upper plateau, that is, the border-range of the Yablonovoi. 

 This escarpment separates the Daurian flora from the Siberian, prop- 

 erly speaking, as sharply as the Great Khingan separates the Man- 

 churian flora from the Daurian. 



The Little Khingan will, I am inclined to think, also appear some 

 day as another interesting botanic boundary between the Manchurian 

 flora and the flora of the Pacific littoral. It is also quite certain that 

 in central Asia, in the Gobi, in India and in western Asia, one could 

 arrive at most interesting botanical generalizations by establishing the 

 connection between the orographical and the botanical data; it is suf- 

 ficient to mention here, as an instance, the delimitation of botanic 



