320 On the CUmaie and Fegetation of the Himalaya. 



tion ; and on the dry stony hills of the Punjab where rain hardly 

 ever falls, and it is at all seasons exposed to a powerful and scorch- 

 ing sun. The only other coniferous tree of low elevations in the 

 Himalaya is Podocarpus, one species of which is a native of the 

 lower ranges of Nepal and Sikkini. 



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 Hima- 

 laya. 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 Kamaon, and extends as far east 

 as Bootan. The most alpine species of the family are P. Gerar- 

 diana, 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 subal- 

 pine zones as we advance towards the interior of the mountains, in 

 consequence of the diminution in the amount of rain. 



In travelling through the Plimalaya we ascend a great river, the 

 ascent is so very gradual, that the change of climate and of vegeta- 

 tion in ascending is almost imperceptible, and is only detected by 

 careful observation. If, however, on the other hand, we cross a 

 range of considerable elevation, and descend on its northern side into 

 another valley, the transition is often very striking, and if the chain 

 be sufficiently elevated to intercept the greater part of the rain, the 

 contrast between its two sides is perfectly astonishing ; when the 

 transition is thus complete, the traveller leaves dense forests and 

 common Himalayan vegetation on the one side, to find on the other 

 a dry, barren, burnt-up soil, with scattered Astragali, Boraginece, 

 Crudferce, of forms quite characteristic of the flora of Siberia. Such 

 is the vegetation of Tibet, which may be reached either suddenly 

 by crossing a lofty pass, or gradually by ascending the Indus, the 

 Ohenab, the Sutlej, the Ganges, and many other of the Himalayan 

 rivers. This arid vegetation is met on the Sutlej, as low as 10,000 

 feet above the level of the sea, and is therefore in no way dependent 

 upon mere altitude. 



