AA = 
sand has been carried away, the roots are covered in with 
sand over which a layer of clay is spread. On an average 
about half the plants are successful, but the gaps are filled 
up by a second planting. 
It is of the greatest importance for the natural seeding 
of trees and bushes that many herbaceous plants should 
grow on the sand; if these are absent, then many seeds of 
Aristida pennata and Alhagi Camelorum are sown. The herb- 
aceous plants retain the fruits of the trees and protect the 
seedlings during their growth. 
We have here only referred to those parts of PALEzKU’s 
work which deal with the vegetation. 
G. J. TANFILJEW in the second Russian edition of War- 
MING’s “Plantesamfund” (Oecology of Plants) (translated by 
GENKEL, St. Petersburg 1903) gives a survey of the vegetation 
of Russia. The chapter dealing with deserts is of special 
interest to us. Desert and Steppe are closely related in the 
following respects: both are at the present time devoid of 
trees, they are not leached by running water and the soil is 
rich in dissolved salts, especially carbonates but also sul- 
phates and chlorides. 
In the steppe, however, carbonate of lime is dominant, 
and the more soluble salts do not attain the same concen- 
tration as in the desert. The steppe-vegetation is therefore 
richer, forming a more or less thick carpet all the year round, 
and the decomposing vegetable matter gives a dark colour 
to the upper layers of the soil (for instance in the Tjernosem). 
In the deserts the carpet of vegetation is either absent alto- 
gether or is present only in early spring; during summer and 
autumn the earth is bare or only sparsely covered with 
woody stems or dead shoots. No green-sward is present and 
no dark humus is formed, but dissolved salts are abundant 
and often crystallize out on the surface. 
The Semi-Desert (Loess-desert) is related to both steppe 
and desert. It resembles the desert in that it lacks the dark 
surface-layer of humus and the perennial sward of plants, 
while it has the high salinity of the loess. On the other 
hand, the luxuriant spring-vegetation is like the steppe, the 
loess of which is identical with that of the semi-desert. 
