10 TRANSACTIONS OF THE [Sess. lxxx 



maple, Tilia, oak, alder, holly, birch, walnut, and many 

 climbers such as Clematis and honej^suckles, Akebia, Acti- 

 nidia, Aristolochia, shrubs like Ribes, Rubus, and rhodo- 

 dendron, etc. The undergrowth of this rain forest has 

 already been mentioned, as also the next formation, alpine 

 meadow. Within the limits of the alpine meadow come 

 numerous smaller plant associations dependent on soil, 

 situation, and physical conditions generally, and above 

 the tree limit we come to alpine turf, with dwarf rhodo- 

 dendron. Lastly comes open scree, where a few plants 

 struggle up almost to the snow-line, gradually growing 

 fewer and ultimately disappearing altogether. 



Starting then from the Mekong valley, we have in the 

 valley itself a xerophilous flora, then the forest belt, 

 dominant because it is dependent on the climate of this 

 region, hot, wet summers and cold winters with some rain 

 at all seasons ; hence it covers the greater part of the 

 range, being absent only where the general climate is subor- 

 dinated to local climatic conditions, the result of extremes, 

 e.g. in the bottom of the Mekong valley, and above 

 14,000 or 15,000 feet. After the forest belt comes the 

 meadow, incidental because it occurs only to a limited 

 extent in the valleys, dependent on special local conditions, 

 and within the limits of the forest belt ; forest is often 

 mixed up with it, and outstrips it. Lastly comes the 

 alpine belt, including scree associations, turf, dwarf 

 rhododendron, and precipice plants, above the limit of 

 trees. Hereabouts the conditions are more diverse than 

 down below, and near the tree limit the plant associa- 

 tions change more rapidly than elsewhere with any change 

 of conditions. 



On the Mekong- Yangtze divide we also find three main 

 belts, but tlie diflerences, as already pointed out, are 

 striking. The first and dominant formation is the shrub 

 belt, whicli is a contiiuiation of the xerophilous flora found 

 in the valley. Secondly comes the narrow forest belt, 

 which corresponds more or less to the meadow belt on the 

 Mekong-Salween divide, being confined chiefly to the 

 valle3'S and having the shrub belt mixed up with it. 

 Alpine meadow, wliicli is dependent on an almost con- 

 tinuous i-aiiifall tlir()UL''liout the vesfetative season, and 



