— 104 — 
burrowing rodents. In the terms used by Cow es this met- 
amophosis is a topographic succession, due to topographical 
changes of the surface. Korsninsky regards the matter from 
a different point of view. His opinion (1896 pp. 6, 8) is that 
the “normal type” of sand-desert is the Desert-plain “level 
or undulating areas of sand” covered with Haloxylon, Salsola 
Arbuscula, Calligonum, Ephedra, Ammodendron and Eremospar- 
fon, and during spring with a number of herbaceous spring- 
plants; this desert-tree vegetation KoRSHINSKY regards not only 
as the most characteristic, but also as the original type (comp. 
above p. 36). He is of opinion that in former times a similar 
vegetation covered the whole area of sand, and that man is the 
agent of destruction to whose devastations the naked and shifting 
sand-desert is due. “As soon as we get away from roads 
and human habitations and reach more solitary places, we 
always find that the sand-surface becomes more closely covered 
with vegetation of trees or shrubs. These trees arrest the sand, 
not through their sand-binding roots, but through their size 
which modifies the force of the wind and screens the soil from its 
attacks. Under their protection a richer herbaceous vegetation 
is also developed.” This development from stable to unstable 
desert through the agency of man must be termed a biotic 
succession (Cow tes). This and the topographic succession 
mentioned above do not exclude each other. 
Even if we allow that KorsHinsky is correct, that man 
through felling trees for firewood and through his herds of 
cattle roaming about, has in many places laid bare the arrest- 
ed sand and thus brought about the appearance of ithe naked 
desert, — it is still probable that the Desert-plains and the 
Hummock-desert have originated from the shifting-desert. In 
what other way could the hilly or undulating sand-desert 
originate? With OBRUTSCHEW and RADDE I consider it most 
natural to assume that the normal and natural development 
(the regional succession, (COWLEs) not the topographic or biotic 
one) has taken place from Barchans to Hummock-desert and 
from the latter to Desert-plains. It is not correct as KORSHINSKY 
states that the stable desert is always found far from human 
habitations, for in such places I.have seen wild sand-desert 
almost devoid of vegetation. 
