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 Camelonim often extending 

 right up to the top of the dunes; on lower places Pluchea 

 caspica, Lycinm ruthenicnm 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 svell-know T n 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 on 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 ot 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 



