318 FLORA INDICA. 



and are hence gradiially drying up. This diminution of many 

 of the lakes is no doubt entirely attributable to a change of 

 climate, which is extremely interesting in a botanical point of 

 view, from its favouring the immigration of many saline types 

 of the Caspian flora. 



Where the surface is covered with salt-marshes, are found 

 Glaux maritima, Eurotia, Corispermum, Caroxylon, Suteda, 

 Salsola, Chenopodiwn, Ambrina, Christolea, Triglochin ; and a 

 large Nostoc, of a species eaten in China, floats on the surface 

 of the pools. The carbonate of soda again appears to have 

 no appreciable effect on the vegetation of the dry soil it en- 

 crusts ; grasses, tufted Androsaces, Astragali, Griaphalia, Ar- 

 temism, etc., being alike covered with it. 



Cultivation in Tibet attains the height of 15,000 feet, and 

 is luxuriant below 12,000 feet, barley and wheat being the 

 grains ciiltivated, with rape and millet at lower levels. The 

 indigenous vegetation is everywhere scanty. Though there is 

 no forest, the banks of the rivers and streams are skirted by 

 a dense scrub of bushes, chiefly Myricaria, Hippophae, Rosa, 

 and Lonicera. Populus balsamifera and Euphratica, and Juni- 

 perus excelsa are the only trees, and these occur rarely; as 

 does Pimis excelsa, which is only found towards the confines 

 of Hasora, and can hardly be considered a Tibetan tree. My- 

 ricaria and Hipipophae occasionally attain a height of twenty 

 feet. Of cultivated trees, apricots and Populus balsamifera are 

 seen up to 12,000 feet ; apples, walnut, the black poplar, and 

 Elaagmis up to 11,000 feet, pears to 10,000 feet, and grapes 

 and white poplar and plane-trees to 9000 feet. 



Subtropical types ascend along the course of the Indus 

 to Rendu and Iskardo, and some of them even as far as 11,000 

 feet, in Nubra and Le, of which the following genera are ex- 

 amples : — 



Capparis. Echinops. 



Peganum. Tamarix OaUicn. 



Tribnlus, Lyeium. 



Sophora. Vincetoxicum. 



