— 128 — 
advancing dune of about the same height is in process of 
burying some of them, the bushes impede the progress of 
the sand but where there is a break in the Tamarix the dune 
presses forward curving in a south-westerly direction. 
6. Desert south of the town of Kunja Urgentsh (Chiwa) 
and south of a branch of the Amu Darya running towards 
the west. August 4. 1899. 
Along the river as a green belt runs a rugged tract of 
sand thickly covered with Tamarisk-bushes. These are some 
of the Tamarix dunes already described (p. 96) which are 
stationary and stratified, but the bushes also grow in great 
numbers on the loose shifting sand. Interspersed among the 
Tamarisks are thousands of Alhagi Camelorum often extending 
right up to the top of the dunes; on lower places Pluchea 
caspica, Lycium ruthenicum and Phragmites communis. The 
boundary between this green band and the desert is sharply 
defined. The latter is a naked plain with loess as a soil; it 
is stable and flat and bordered in the far distance by the 
green trees and fields of an oasis. In some places, however, 
the soil is torn up, possibly through wind-erosion, and here 
the loess shows a well-known characteristic in that it forms 
perpendicular shelves, the largest a couple of metres high. 
To the west lie some large and almost naked sand-dunes 
which show by their shape that north-easterly winds prevail; 
here and there smaller dunes appear où the loess-plain, and 
in their neighbourhood the clay-soil is covered by a level 
layer of sand. 
Isolated tufts of Aristida pennata grow on the larger dunes. 
In a sandy valley between two dunes one notices even from 
a distance fresh green patches which are groups of large, 
vigorous Alhagi. The glissade of the most easterly dune has 
commenced to pour its masses of sand over them, and some 
show now only the outmost shoot-apices projecting above 
the sand, their days being numbered. On the other side of 
the dune, Alhagi suffers in the opposite way, for here the sand 
is blown away from it and strong vigorous bushes of aerial 
shoots are overthrown and lie on the sand, anchored by 
stems metres in length. Previously while these were co- 
vered by soil, they were vertical. One could see that they 
