Vegetation of the Himalaya. 319 



come more and more bare and grassy, wliile the lower levels and the 

 base of the mountains rctam a greater degree of damp and are clothed 

 with forest. It would appear also that above 6000 or 7000 feet, 

 up to 10,000 or 11,000 feet, at which elevation mountain ranges 

 sensibly interrupt the passage of the moist atmosphere, the temperate 

 ranges are more moist than those below them, which do not collect 

 the clouds, and have a higher temperature, and consequently more 

 powerful sun. To the eastward of Sikkim, the same phenomena are 

 very well marked, the lower ranges being extremely dry and arid, 

 while above 7000 feet, dense forest and a humid atmosphere prevail, 

 just as in the mountains of Sikkim. 



The valleys of the larger rivers which traverse the Himalaya from 

 north to south, have of course a much lower elevation than the 

 mountains by which they are surrounded ; and up them, therefore, 

 tropical vegetation penetrates very far into the interior. In the 

 extreme west, the valleys of the Indus and Chenab, and even of the 

 Sutlej, are up to the height of 5000 feet, which they do not attain 

 till more than 100 miles from their exit into the plains, hot, dry, 

 and tropical. Further east, the tropical forest stretches far up the 

 valleys, and they are only bare for a small portion of their extent, 

 and in the humid atmosphere of Sikkim they are densely wooded 

 throughout. In that province, the valleys of the Teesta and its 

 tributaries carry tropical vegetation far into the interior, almost 

 within a day's journey of the line of perpetual snow, and the luxu- 

 riance of the dense and dripping forest requires to be seen to be un- 

 derstood. 



The temperate region of the Himalaya may be said to extend from 

 about 5000 feet, or a little above it, to the upper limit of arboreous 

 vegetation; which, to the westward, is about 12,000 feet, to the 

 east about 1000 feet higher. Above 9000 feet, however, the tem- 

 perate region is characterised by many remarkable forms, which da 

 not extend lower ; these are generally, in the west especially, of 

 very European type; but in the eastern flora, it is at such levels that 

 the magnificent Rhododendrons of Sikkim, which form so striking a 

 part of its flora, principally occur. In this zone a great part of the 

 trees are of European genera, alder, oak, birch, hazel, hornbeam, 

 horse-chestnut, and cherry, being characteristic forms. It is also 

 especially the region of coniferous trees, very few of which extend 

 either below or above it. The pine which descends to the lowest 

 level in the Himalaya, is Pinus lonc/ifolia, which is a common tree 

 throughout the whole region from the mountains of the Punjab to 

 the east of Bootan. It is confined in a great measure to the outer 

 ranges of the mountains, and commences as low as 1000 feet above 

 the level of the sea, rarely if ever attaining a greater elevation than 

 7000 feet. This tree appears to have a very great power of endur- 

 mi ing varieties of climate, for it seems equally at home in the hot, 

 UL damp valleys of Sikkim, surrounded by an entirely tropical vegeta- 



