u — 
washed by this sea. In this earlier period the climate, which 
was probably rather moist, had been favourable to the growth 
of plants and had resulted in a luxuriant and fairly homo- 
genous flora developing over the immense area between the 
Himalaya and the Pyrenees. When the sea disappeared the 
climate became dry. The plants came under the influence 
of a very different environment so that they were compelled 
to change. Only in the northern part of the Elburs and the 
western part of the Caucasus, near two great inland seas, 
are luxuriant forests still found which are regarded as the 
last, though perhaps somewhat altered, remnants of the old 
tertiary vegetation of Western Asia. The rest of the plants 
must either die or adapt themselves to the new conditions. 
At the same time the Aralocaspian lowlands,.left by the sea, 
were open to immigration from the neighbouring countries. 
The result of the changes which took place was a new flora, 
xerophytic and especially adapted to a climate with a short 
vegetative period, but which was — and is — otherwise 
closely related to the elements of the flora of the Mediter- 
ranean lands with which they have a common origin’). 
If the development took place as indicated here ac- 
cording to ENGLER, it is evident that the flora of Trans- 
caspia must for the most part have originated from that of 
Western Asia, and that the plants must have descended from 
the mountainous parts towards the South and East (comp. 
Borsczow, above p. 30). Southern Russia cannot come under 
consideration as a starting point for the species which pop- 
ulated Transcaspia, because large tracts of it at the beginning 
of the quaternary period (SJÖGREN, see also KARPINSKI) were 
covered by water (the Aralocaspian Sea) and this “Caspian 
Transgression” probably originated in ice-water from the 
margins of the great European ice-sheet, so that the climate 
must have been cold. With regard to the climate of Western 
Siberia at that period there is no information, but it must 
also have been cold, colder than now, therefore the possibility 
of immigration from there need not be considered. 
7) ENGLER 1879, pp. 57 and following, 184 and following. 
IT. 
