— 91 — 
a fact that in Pamir the localities with a southern exposure, 
(the driest), have the greatest number of chamaephytes, those 
with a northern exposure the smallest number; while hori- 
zontal. flats lie between the two, both in regard to insolation 
and to number of chamaephytes. 
How the species on the southern slopes adapt themselves 
in other respects to their surroundings, may be judged by 
comparing them with the flats described above. The species 
on slopes with a southern exposure are no other than a 
selection of the species growing on the flat “Pamirs”, a 
selection made by nature herself. If we try to catalogue them 
according to leaves and covering, as was done with the plants 
of the flats, we find among these plants growing on slopes 
with a southern exposure, 5 pinnate Astragaleae as compared 
with 11 on the flats, — 3 other species with pinnate or 
pinnatifid leaves, as compared with 6 on the flats, — 3 species 
with undivided small, hairy leaves, as compared with 7, — 
2 Gramineae and Cyperaceae, as compared with 7, — 2 species 
with small, narrow, glabrous leaves, as compared with 5, — 
1 species with large entire, glabrous leaves, as compared with 6, 
— 1 evergreen as compared with 3, — 1 Polygonacea as com- 
pared with 2, — and 1 leafless Ephedra as compared with 1. 
The reduction has, as we see, especially hit the groups 
Gramineae + Cyperaceae, and the two groups with entire 
and glabrous leaves. These 3 groups contain, I suppose, the 
least xerophytic plants. The plants on southern exposures 
in the remaining larger groups number about the half or 
a little less, of the species of the same groups on the flats, 
corresponding to some extent to the total number of species 
in the two localities: 19—49. 
That the least xerophytic species of the flats are prefer- 
ably the ones wanting on the southern slopes confirms that 
the former are drier than the latter. 
The plants on slopes with a northern exposure do not, 
as so often stated, belong to the xerophytic type. A glance 
at the list, page 87, will confirm the impression that the 
species are, on the average, mesophytic in their structure. 
Only a few species (Psychrogeton, Hedysarum, Acantholimon) 
are found again on the slopes with a southern exposure, and 
