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are bushes of Tamarix and Salix angiistifolia with narrow- 

 leaved Populus euphratica, while masses of Glycyrrhisa glabra 

 hide the ground. The dominant plant after the poplars is 

 Apocynum venetum, which attains the height of 2 — 3 metres 

 and has thin stems, the growth being that of a semi-liane 

 supporting itself on other bushes by the aid of its out- 

 spreading branches. These extend horizontally and through 

 their own weight become pendulous, the extremities bearing 

 inflorescences of handsome red blossoms.') When Apocynum 

 venetum grows on treeless ground, the branches lie prostiate 

 along the surface. 



Also Clematis orientalis and Cuscuta Lehmanniana I have 

 recorded as being of frequent occurrence in thickets of the 

 above type. 



The thickets described above must be regarded as true 

 riverside or gallery forest, an edaphic formation whose differ- 

 entiation from the surrounding formations depends solely 

 upon the presence of the river; in the first place the thickets 

 are only found along the river, and secondly one can see 

 that further from the river they become thinner and lower. 

 Such is for instance the case at Kogertle on the right bank 

 of the Amu Darya. Here the river-bed is much wider than 

 the river and is evidently subject to periodical flooding. 

 The plain is covered with thick luxuriant forests of poplars 

 interspersed with Phragmiteta and glades with Ei-ianthus and 

 Tamarisk. Gradually as one goes farther away from the 

 river, the forest thins out and the poplars become lower 

 and less vigorous. The clumps of trees become separated 

 more and more by open spaces occupied only by isolated 

 plants of Glycyrrhiza glabra, Halimodendron argenteum, Zygo- 

 phyllum Eichwaldii, Tamarix or low pjoplar-bushes. The 

 Tamarisks become more frequent until as almost pure com- 

 munities they form the outposts against the brown bare hills 

 of the desert. As will be shown later (chap. 11), the Tama- 

 risks may even invade the desert, where by means of their 

 very long roots they can always secure water from deeper 

 layers. 



') A fibre obtained from Apocynum venetum is used by the natives 

 for cordage under the name "red hemp" (Kisil Kandir). 



