1915-16.] BOTANICAL SOCIETY OF EDIXBURGH 11 



does not, like the forest, mind Avind, is wanting altogether ; 

 and the third belt, that of the alpine associations, is much 

 the same as on the Mekong-Salween divide, though not 

 so rich in genera. The differences recorded are not, of 

 course, entirely due to the smaller rainfall on the Mekong- 

 Yangtze divide, considerable modifications having been 

 introduced b}^ the retreat of the glaciers and elevation of 

 the snow-line, as already pointed out. Again, the Mekong- 

 Salween divide is the extreme eastern boundary of the 

 monsoon region, and its climate approaches that of the 

 Burmese hinterland, which has undoubtedly contributed 

 to its flora, while the Mekong- Yangtze divide is cut off 

 from this source of supply by the whole length of the 

 dry Mekong valley ; if the latter range ever supported any 

 monsoon plants, they would probably have disappeared 

 before now. Here, however, I am dealing with the forma- 

 tions and plant associations, not with the flora and its 

 origin, which is another matter. While, however, the 

 climatic differences on the two ranges have differentiated 

 the formations and to a considerable extent the flora, this 

 does not obscure the still more remarkable similarit}' noted, 

 nor conceal the fact that a common origin alone will 

 explain this.^ 



The following lists, of course far from complete, contain 

 the names of certain characteristic plants of each associa- 

 tion in the alpine region. Those marked with an asterisk 

 are common to both divides (though it cannot be said for 

 certain that others too are not common), and it is worth 

 noting that the alpine flora of the two divides has a much 

 larger proportion of species in common than the forest 

 or meadow belt, very few species of the latter association 

 being found on the Mekong- Yangtze divide, though many 

 species of both the alpine and meadow belts, of the Me- 

 kong-Salween divide, extend southwards and westwards 

 into the Burmese hinterland. 



Alpine Turf. 



*Priinula hella, Franch. 

 ^Primula brevifolia, G. Forrest. 



1 North of latitude 28° 30' the fonnations and flora on the two divides 

 are identical. 



