INTRODUCTOllY ESSAY. 177 



of nearly 13,000 feet by Mr. Booth in 1849, in a district north 

 of Bishnath, in Upper Assam, which is inhabited by a race 

 called Duphlas. He collected some Ferns, and especially seeds 

 of Rhododendrons, of which an account has been published 

 by Nuttall in ' Hooker's Journal of Botany.' 



Mr. Griffith's attention was of course mainly devoted to the 

 botany of the district, and in his ' Itinerary Notes' and jour- 

 nals we have a mass of important information regarding the 

 general features of the vegetation, together with a great deal 

 of detail which will become valuable as soon as the species 

 are determined. 



The climate of Bhotan seems to be very equable, and the 

 humidity of the winter months appears to increase to the 

 eastward. We do not, however, possess any records of tem- 

 perature or humidity, and our inferences regarding the cli- 

 mate are drawn from the vegetation only. The steepness with 

 which the mountains rise, and the influence of the elevated 

 mass of the Khasia to the south, make the lower mountains 

 which skirt the plains of Assam, between the Godada and the 

 Monas, drier than those nearer Sikkim, which are exposed to 

 the full force of the monsoon, or than those further east. 



The deep narrow valleys of the great rivers carry a tropical 

 vegetation very far into the interior of Bhotan, among lofty 

 mountains capped with almost perpetual snow. These attract 

 to themselves so much of the moisture of the atmosphere, 

 that the bottoms of the valleys are everywhere comparatively 

 dry and bare of forest, which only begins at about 6000 feet of 

 elevation, except in ravines. The outer ranges, too (except 

 near Sikkim), even above this level are only partially wooded, 

 the trees being arranged in clumps, among which are inter- 

 spersed open grassy glades, which are compared by Griffith to 

 those of Khasia; Oaks and Rhododendrons being extremely 

 abundant. 



On the northern face of the range which separates the Mo- 

 nas valley from Assam, Pines make their appearance, the first 

 species being Pinv^ longifolia in the drier valleys below 6000 



2 a 



