NOTES ON THE FLORA OF NORTH-WESTERN YUNNAN. 39 
NOTES ON THE FLORA OF NORTH-WESTERN 
YUNNAN. 
By George Forrest. 
The flora of North-west Yunnan is so rich and varied, the area so 
extensive, the mountain and river systems so complicated, that it 
is a matter of no small difficulty to select one portion in illustration 
of the whole. The region includes the watersheds of the mid-Salwin, 
Mekong, and Yangtze ; those watersheds are broken into an indescrib- 
able chaos of subsidiary ranges and spurs, many of them bearing 
species which are purely local. Much of the area is still unknown, 
or at least unmapped. 
It is a marvellous country, planned on Nature's grandest scale, 
prodigal in flora and fauna, rich in minerals ; for gold, silver, galena, 
copper, iron, and coal are found on every side. Numerous tribes, 
nearly all of Tibetan origin, people it, settled in the valleys and on 
the ridges as far south as lat. 25 0 N., the diversity of whose customs, 
languages, and religions is truly remarkable. Like the slopes of the 
Caucasus, the region might be called the country of the hundred 
nations, and is worthy of the most thorough exploration by competent 
ethnologists. 
All of the principal ranges, which fall away from the Tibetan plateau 
and enclose those three great rivers, run due south as far as mid- 
Yunnan, at which point the divergence eastwards of the Yangtze 
causes a break in the regular contour of the country. 
As is now generally known, the formation of those ranges is purely 
limestone, a hard grey magnesian limestone, and that possibly accounts 
in great measure for the exceptional richness and high development 
of the vegetation. Only in the principal and deepest valleys — the 
Salwin, Mekong, and Yangtze — are other strata exposed in places, 
and in descending to those one immediately leaves the most interesting 
flora behind. 
In the higher valleys, above 6,000 feet, and the still higher plateaux, 
the soils consist of heavy reddish clay marls, gritty limy clays and 
loams, and lime silts and cements. Quite a number of those valleys, 
even at an altitude of 9,000 feet, show signs of having been at some 
period the sites of extensive lakes; evidence, in the shape of deep, 
extremely durable, and barren lacustrine deposits, being abundant. 
On the rolling downs, which are characteristic of the country in 
the centre, east, and south-east of the province, the clay marls and 
heavy loams are general ; in the opposite direction, north-westwards, 
the farther one travels the more evident is the limestone, till, north 
of lat. 26 0 , it becomes dominant. 
