250 CLIMATE OF HIMALAYA. 



India to the uppermost limit of vegetable life. This would be 

 an easy task if the vegetation were uniform throughout the whole 

 chain, but owing to the great variations of climate to which I 

 have just adverted, there is a very great difference in this respect, 

 few indeed of the plants of the eastern extremity of the Himalaya 

 being identical with those which occur in the far west. In 

 general terms, it maybe said, that to the eastward the vegetation 

 is very much more luxuriant and tropical, and tliat it clianges 

 very gradually in advancing to the westward, in exact proportion 

 to the diminution in the quantity of rain. The same gradual 

 transition in the vegetable world may also be observed in advan- 

 cing up the valleys, or in passing across the mountains from the 

 outer valleys to those which are further removed from tlie 

 Indian plain ; though in the latter case, of course, the effects of 

 gradually increasing elevation must be taken into consideration 

 as partly the cause of the change, as well as the decrease of 

 humidity. 



Tiie plains of northern India which skirt the base of the Hima- 

 laya do not (if we except the belt immediately at the base of the 

 mountains) present by any means a rich flora. From their 

 situation nearly on the tropics, their distance as a whole from the 

 sea, and their proximity to the mountains, they are not very 

 damp, and their climate has too decided a lowering of tempera- 

 ture in the cold season to permit them to be clothed with the 

 dense forest vegetation which clothes the tropical plains of South 

 America. They are in general open plains without much wood, 

 and where not under cultivation, are covered either with a dense 

 jungle of different species of Arundo and Saccliarum, or with 

 scattered trees of various tropical families, Acaciae and Zizyphi 

 being very common genera. Here and there only there are 

 patciies of forest, generally low and scrubby, and without much 

 underwood, or any of the fine parasitical plants and ferns which 

 are so ornamental in tropical woods. 



In the lower parts of Bengal, the proximity of the sea some- 

 what modifies this general character ; a number of ferns, one or 

 two species of pothos, and a few^ Orchidese, among which Vanda 

 Roxburghii and a large and fine Cymbidium are the most com- 

 mon, are to be found. In the same way the valleys of Silhet and 

 Assam are exceptional in character, but from their being inclosed 

 with mountains of some elevation on all sides, they are scarcely 

 to be regarded as part of the Indian plain, but may more pro- 

 perly be considered as wide mountain valleys, and they in fact 

 closely resemble in vegetation the valleys of the larger Hima- 

 lay^an rivers in the east part of the chain. 



Close to the foot of the chain of mountains throughout its 

 whole course from east to west, there lies a belt of forest and 



