Dk. Thomson on the Climate and Vegetation of the Himalaya. 203 



tation; which, to the westward, is about 12,000 feet, to the east about 

 1,000 feet higher. Above 9,000 feet, however, the temperate region is 

 characterized by many remarkable forms, which do 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 floi-a, principally occur. In 

 this zone a great part of the trees are of European genera, alders, oaks, 

 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 longifolia, which is a common tree through- 

 out 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 7,000 feet. This tree appears to 

 have a very gi-eat power of enduring varieties of climate, for it seems 

 equally at home in the hot, damp valleys of Sikkim, surrounded by an 

 entirely tropical vegetation ; and on the dry stony hills of the Punjab 

 where rain hardly ever falls, and it is at all seasons exposed to a power- 

 ful and scorching sun. The only other coniferous tree of low elevations 

 in the Himalaya is Podocarj^us, one species of which is a native of the 

 lower ranges of Nepal and Sikkim. 



Pinus excelsa, which is allied to P. strobus, and Pinus Smithiana, 

 which is near abies, are the more common species of the central zone, 

 which are distributed throughout the whole extent of the Himalaya. In 

 the same zone, the deodar (Cedrus deodara) is confined to the western 

 mountains, not being, I believe, to be found indigenous in any part of Nepal, 

 while P. Brunoniana, on the other hand, commences in the eastern parts 

 of Kamaou, and extends as far east as Bootan. The most alpine species 

 of the family are P. Gerardiana, P. Webbiana, and several species of 

 juniper, of which all but the first, which is a western tree, seem universally 

 distributed. 



It would be needless to dwell at any length on the alpine zone, because 

 luxuriant as is the vegetation, and beautiful as are the plants, the forms 

 at least must be familiar to most of my auditors. 



I must be content, in conclusion, with drawing your attention to the 

 change produced in the vegetation in the temperate and subalpine zones 

 as we advance towards the interior of the mountains, in consequence of 

 the diminution in the amount of rain. 



If in travelling through the Himalaya we ascend a great river, the 

 ascent is so very gradual, that the change of climate and of vegetation in 

 ascending is almost imperceptible, and is only detected by careful obser- 

 vation. If, however, on the other hand, we cross a range of considerable 

 elevation, and descend on its northern side into another valley, the transi- 

 tion is often very striking, and if the chain be sufiicicntly elevated to 

 intercept the greater part of the rain, the contrast between its two sides 



