Chap. IX] 



DESERTS 



619 



most remarkable in East Africa. One of them, Pyrenacantha malvifolia (Olacaceae), 

 during the dry season reveals only the stem swollen out in monstrous fashion, 

 and not until the rain approaches do there spring forth from beneath the upper 

 convex surface shoots, hardly as thick as one's thumb, which are beset with mallow- 

 like leaves, and clamber up through the surrounding bushes. The other, Adenia 

 globosa (Passifloraceae), permanently bears at the top of its tuberous stem cascades of 

 arching green, switch-like shoots, which bend down to the ground or support them- 

 selves against and climb up trees and shrubs, and which, instead of bearing leaves, 

 are armed with finely pointed, conical, hard thorns. . . .' 



The oecological character of the vegetation of the Sahara continues the 

 same eastwards (Fig. 350), as far as North-West India, the flora also 

 exhibiting great constancy. According to Brandis x , there are forests along 

 the Indus within reach of the abundant subterranean water, but beyond 



Fig. 355. Trans-Caspian desert, near Kara-bugaz. Calcareous sand with Salsolaceae, 

 Calligonum sp. From a photograph by Andrussovv. 



this river only a meagre growth of shrubs prevails, consisting of species 

 that also cn-ow in the desert districts of Africa. 



ii. THE DESERT DISTRICTS OF WEST AND CENTRAL ASIA. 



The great Central Asiatic desert is a north-eastern branch of the desert 

 of North Africa and Arabia, and extends from the shores of the Caspian 

 Sea, about 50 E.. up to Eastern China, at about 120 E. 



It is split into a western portion, extending from the Caspian Sea to the 

 Tian Shan, and an eastern portion, extending from these mountains to the 

 Chinese Great Khingan Mountains. The western or Trans-Caspian desert 

 is a plain ; the eastern one of Gobi, a plateau. Both desert tracts belong 

 to the cold temperate belt and possess an extreme climate. 



Przhevalsky - makes the following statement regarding the climate of 

 the Gobi desert : — 



1 Brandis, op. cit., p. 414. 2 Przhevalksy, II, pp. 247, 248. 



