Some Plant Formations from the Arid Regions of 
Western China. 
BY 
F. KINGDON WARD, B.A., F.R.G.S. 
HE arid or semi-desert regions to which the following notes apply 
J- comprise several deep trench-like valleys, trending for the most part 
north and south, which dissect the complicated mountain systems of far 
western China in the provinces of Kansu, Ssii-chuan, and Yun-nan, or 
as this country may be comprehensively termed, Chinese Tibet. 
As examples to which I shall have occasion to refer we may instance 
the headwaters of the Min river in Southern Kansu, the T'ung-ho, and the 
Kin-sha-kiang (or upper Yangtze) in Ssii-chuan, the upper Mekong in 
North-West Yun-nan, and the upper Salween in South-East Tibet, north of 
lat. 28°. The arid nature and peculiar vegetation of these gorges in the 
midst of a region of copious rainfall, certain historical questions which 
obtrude themselves in connexion with one of the most characteristic 
components of the open formation met with, and the morphological adapta- 
tions of the flora, are interesting points which deserve to be considered 
in turn ; but at the outset it will be well to explain how these barren gorges 
have come into existence in the first instance. 
The rivers referred to here flow at altitudes varying from about 6,000 
to perhaps 10,000 feet above sea-level, while the mountains immediately 
overshadowing them rise to very much greater altitudes, more especially in 
the case of the Mekong and Salween rivers. 
Apart from the xerophytic nature of the vegetation, the fact that these 
rivers have been able to cut their way straight down between their investing 
walls is sufficient evidence for the dryness of the climate in the valleys 
themselves, but the big alluvial cones debouching into the main valleys 
speak just as eloquently of a furious rainfall above. 
Where the rock is limestone clean-cut gorges are indeed always formed, 
owing to natural jointing ; but even where the rocks are of granite, or 
of metamorphic origin, these rivers have managed to cut their way straight 
down, often leaving cliffs of rubble as much as 700 feet high. 
Through these funnel-like valleys a daily wind blows up from south to 
north throughout the summer months with the regularity of a trade wind, 
springing up shortly before mid-day and dying away after sunset. 
[Annals of Botany, Vo). XXVI. No. CIV. October, 1912.] 
