4 GENERAL COLLETT AND MR. W. 8. HEMSLEY ON PLANTS 
19th and 22nd parallels of North latitude, and as bounded on 
the east by the Salween river, and on the west by the plain of 
Upper Burma. 
Along the whole western border of this mountainous region 
runs the belt of jungle locally known as “ the terai,” which inter- 
poses its malarious valleys between the plain country and the 
healthy plateaux of the interior hills. This fringe of forest, or 
terai, presents the usual features characteristic of similar belts 
of jungle bordering the foot of the Himalayas, from north-east 
to south-west. Up to about 2000 or 2500 feet of elevation the 
forest is dry, the soil poor, and the trees more or less stunted in 
their growth, forest-fires being of frequent occurrence. Under- 
growth is almost absent, and bamboos and Dipterocarps, asso- 
ciated with species of Stereospermum and Dillenia and a few 
climbers, such as Spatholobus and Congea tomentosa, are the 
most prominent features of the vegetation. 
On attaining a higher elevation, from about 2500 to 4000 feet, 
the character of the vegetation is much changed, owing in part 
to the greater humidity, in part to a lower temperature. The 
trees are much larger; mosses, lichens, and ferns abound; the 
hill-sides are covered with undergrowth, and numerous trees and 
herbaceous plants appear which are not represented at lower 
levels: such are Quercus, Schima Wallichii, and two or three 
arboreous Composite. This is the principal forest, from the 
gloomy depths of which the traveller passes, at about 3500 or 
4000 feet of elevation, by one step, to the open breezy plateaux 
intervening between the forest edge and the next range of moun- 
tains. It causes a pleasant feeling, after marching for two or 
three days along narrow paths, cut through dense jungle, and 
breathing a stagnant atmosphere, to mount the last ascent and 
emerge, quite unexpectedly, into the cheerful light of day, 
seeing before one rounded grassy hills, with occasional clumps of 
oak or pine, and crowned in the blue distance with the pic- 
turesque pagodas of some Shan village. It is the plants of these 
rolling plateaux, and of the precipitous limestone hills which rise 
above them, that have yielded the greater number of the novelties 
described in this paper. 
The general geological formation of the plateaux is a water- 
worn limestone, with occasional interposed sheets and boulders 
of conglomerate, underlying a sedimentary deposit of fine- 
grained red clay or loam, varying in thickness from a thin super- 
