350 



Msport on the Tea Plant of XJfper Assam. [Oct. 



and by a general paucity of leaves. During the examinations, ample 

 opportLiniiies occurred of seeing both fiowers and ripe fruit, the latter 

 being the remainder of the produce of the last season. There is some 

 variation in the time of fiowering between the extreme localities, as at 

 Kujoodoo the plant was in fall flower in the middle of December, while 

 at Nadowar it was in fiower in February. The leaves of all the plants 

 were old and of a very dark green; they were sufficiently coarse and 

 varied in length from 4 to 8 inches. The young leaves unfold^ I believe, 

 about April. 



Remarks on the Vegetation associated with the Tea Plant in Assam 

 and in China. 



The cause that exercises the greatest influence on the distribution 0£ 

 vegetables is known to be temperature, and the causes which exercise 

 the greatest influence on this, are latitude and elevation. The ratio 

 wliich these bear to each other, has been determined by Baron Hum- 

 boldt, one degree of retrogressive latitude being near the tropics equi- 

 valent to an ascent of 396 feet. It is owing to this law that the line of 

 perpetual snow on the mountain Suliteima, in Lapland, lat. 68° N. 

 occurs at an elevation of 3,640 feet, and on Chimborasso, one of the 

 Andes in lat. 2£,30' S. at one of 15,600. For the same reason in ascend- 

 ing in India an elevation of a given height, the floras of a tropical, sub- 

 tropical, temperate, alpine, and lastly, arctic regions may be passed 

 through in succession, until we arrive at the limits of vegetable exist- 

 ence. The same series may be viewed in succession in passing from the 

 equator towards the poles, until we again reach the limits of vegetable 

 existence. In drawing up an estimate of the comparison between the 

 floras of xissam and of the Tea districts of China, we have but little to 

 do with elevation, that little being about 380* feet in favour of Upper 

 Assam, or in other words, nearly a degree of latitude ; so that lat. 2S^ in 

 Assam vv'ill correspond to lat. 29° in the districts alluded to. Elevation, 

 therefore^ not being of sufficient am.ount to be taken into consideration, 

 we must turn to the temperature of either climate (particularly to the 

 mean summer and mean winter temperatures), to the humidity, and the 

 amount of light. This last not having been noticed, we have only two 

 agents to consider, and these, I trust to shevv satisfactorily in a subse- 

 quent part of this report, to be of a nearly similar amount in both cli- 

 mates. I have considered it advisable to preface the remarks on the ve- 

 getation associated with the Tea in Upper Assam, by the above slight 

 notice of the agents that act most powerfully on the dibtribution of 

 plants, because a considerable number of forms appear in Assam which 

 are not found on any part of the plains of India, and which indicate 



* The Barometer at Tatung, according to Abel, stood atSOo 13" at Wooha-kea af 

 300 22', &c. See Abel's chart of the route on the Yang--tse-kiang. 



