TRANSACTIONS OF THE SECTIONS. 73 



the rivers that penetrate at a very low level far into the interior, carrying with them 

 a tropical vegetation into the heart of the mountains. This, hov/ever, is considerably 

 modified by the height and by the greater humidity. We thus find Pines and Palms, 

 Oaks and Maples, growing with the ordinary trees of the plahis, and a similar confusion 

 of the flora of the temperate and torrid zones holds with the shrubs and herbs. From 

 this valley we pass into that of the Pindar, which we follow up from 7500 feet to its 

 source in a glacier at 12,000 feet. From 7500 to 11,000 feet, the region of Alpine 

 forest, the trees most common are Oak, Horse-chestnut, Elm, Maple, Pine, Yew, 

 Hazel growing to a large tree, and many others. They often grow to a very large 

 size, and the forest is usually far finer than in the lower mountains. At about 11,500 

 feet the forest ends ; Picea Webbiana and Belula Bhojpatra being usually the last trees. 

 Shrubs, however, continue in abundance for about 1000 feet more, at about 12,000 

 feet the vegetation becoming almost entirely herbaceous. On this southern face of 

 the mountains the snow line is probably at about an elevation of 15,500 feet. 'J'he 

 constant condensation of vapour on this face causing a very humid climate, the vege- 

 tation is very luxuriant, and the great riches of the Himalayan flora are found in this 

 region. As we pass to the north of the great snowy peaks, we leave behind us this 

 ■wet climate and enter a country that very soon becomes equally remarkable for its 

 extreme aridity, [n the valley of the Gori, into which we next pass at an elevation 

 of 11,500 feet, we find that several Tibetan plants have appeared, the flora, however, 

 having become very poor. The gorges that lead to the great passes into Tibet are 

 almost devoid of vegetation. The highest dicotyledonous plant noticed on this route 

 was at about 17.500 feet, probably a species of Echinospermum ; an Urtica also is 

 common at these heights. The snow line here recedes to 18,500 or 19,000. In Tibet 

 itself, the vegetation is scanty in the extreme, consisting chiefly of Caragana, Artemi- 

 sia, Astragali, a few Graminecs, Potentillece, &c. The plain to the north of the Hi- 

 malaya is almost a desert, not more than one-twentieth of the surface being clothed 

 ■with vegetation, and that of the most miserable sort, the bushes seldom rising above a 

 foot in height. The cultivation of barley extends to a height of 14,000 feet. Vege- 

 tation ends at about 17,500 feet, the highest plants being Corydalis, Crnciferse, Nepeta, 

 Sedum, and some few others. 



On the Botanical Geography of Western Tibet. 

 By Thomas Thomson, M.D., E.I.C.S. 



A section of this country, similar to that which accompanied Capt. Strachey's paper, 

 ■was also exhibited. It extended on a line nearly north and south from the upper part 

 of the Chenab river to the Kara Korum pass on the Konelun chain of Humboldt. 

 The chain to the south of the Chenab, rising to an elevation of 15,000 feet, excludes 

 a considerable quantity of humidity from the valley of that river, and the vegetation, 

 though not altogether losing its truly Himalayan character, becomes much modified. 

 Thus the Oaks, Rhododendrons, and Andromeda, so common on the southern moun- 

 tains, are not found ; while fruit-trees become more abundant, and the Grape-vine 

 ripens its fruit admirably. Passing to the north, the next ridge that is crossed reaches 

 a height of from 20,000 to 22,000 feet, the passes being usually upwards of 18,000 

 feet in elevation. To the north of this range the climate and vegetation suddenly 

 change, and the Tibetan types are at once established. The general character of 

 the Flora is Europeo-Siberian, but much modified by the extreme aridity which 

 almost excludes trees and shrubs ; it hardly exceeds 500 or 600 species in all. The 

 chief groups are Boraginese, Chenopodiacese, Cruciferae, Astragaline Leguminosae, and 

 Artemisoid Compositae. The few trees consist of a Poplar, confined to the more shel- 

 tered ravines, and an occasional Juniper on the hill sides. The more common shrubs 

 are Lonicera, Tamarix, Myricaria and Hippopha'e. The high Alpine herbaceous flora 

 is almost strictly Siberian, and is a little more varied and copious than in other parts 

 of this region, from the additional moisture derived from the melting of the snow. It 

 extends sometimes even to a height of 18,500 feet. 



