— 260 — 
If the flora of Transcaspia originated thus from species 
which at the end of the tertiary period or the beginning of 
the quaternary period immigrated from the neighbouring 
mountains, it is natural to expect that many endemic species 
have developed. For all the factors of the lowlands, cosmic 
as well as terrestrial, differ from those of the highlands; 
besides, for many plants Transcaspia has been a closed basin 
enclosed towards the South and East almost everywhere by 
mountains — the Balchash basin being included — and 
barred towards the West by the Caspian, and towards the 
North by the cold. 
A third condition favourable for the evolution of endemic 
species is the dryness of the climate, and consequently a very 
scattered plant-covering. There is no internecine struggle 
among the plants themselves, but always sufficient open 
ground available; they have only the conditions of the 
environment to contend with (comp. ENGLER 1882, pp. 48, 
324; VAHL p. 154). 
Moreover it is natural that there should be a close flor- 
istic relationship between Transcaspia and the surrounding 
mountainous parts. This relationship must be closest towards 
the South, since the country towards the East rises to a far 
greater height than towards the South where the natural 
conditions must resemble those of Transcaspia more closely. 
Utilising the records of distribution given in the plant- 
list in chap. 12, we shall endeavour to formulate some con- 
clusions which may be of interest with regard to these 
questions. 
The 768 Transcaspian species enumerated in the plant- 
list (chap. 12) may be assigned with respect to their distri- 
bution outside Transcaspia to the following eight groups 
(comp. p. 138): 
1. Endemic species, 169 or 22 p. cent. 
2. Species distributed only towards the South (Western 
Asia), denoted in the list by V: 142 or 18 p. cent. 
3. Species distributed only towards the North (Russia) 
denoted in the list by R: 29 or 4 p. cent. 
4. Species distributed towards the East (High-Asia) denoted 
in the list by H;;33 or. 11, p. cent. 
