DISTRIBUTION OF FLORAS IN S. E. ASIA. 25 



many alpines such as Polygonum Forsterii, Primula serratifolia, 

 Cassiope palpebrata, besides sub-alpines such as Primula sonchi folia, 

 Nomocharis, etc. 



But with the flora of Yunnan east of the Salween, apart from the 

 high ranges which thrust long processes southwards from the north- 

 ern mountain masses, the North Bast Frontier flora seems to have 

 nothing in common. 



Endemic species are found especially in the alpine region, and to 

 a lesser extent at intermediate altitudes. Amongst the former may be 

 mentioned species of Rhododendron, Primula, Cremanthodinm etc., 

 amongst the latter the monotypic genera Becsia and Sporoxia, species 

 of Strobilanthes, Codonopsis and various Gesnerads. 



Those plants which are both Himalayan and Chinese are widely 

 distributed across eastern Asia, often occurring in Japan as well and 

 sometimes even in N. America, (e.g., Clitoria mariana). On the 

 other hand there are plants ranging from the Himalaya into western 

 China, which are not found on the N. E. Frontier, (e.g., Isopyrum 

 grandiflorum). 



Plants from what I have called the Burma-Yunnan area are not 

 found in the Himalaya. This area is simply the splayed out ends of 

 the North East Frontier belt, tailing off southwards into the Indo- 

 Malayan region; it has carried this flora southwards into the Indies, 

 where for instanco Primula imperially is found on the mountains 

 of Java. 



But many plants of the Himalayan foot hills, representing the 

 Indo-Malayan element, are found in the Burma-Yunnan area. 



Negative results in the alpine belt are as valuable as positive 

 results. I have insisted on the relationship of the alpine flora to that 

 of the Himalaya and western China ; but what shall we say to the 

 complete absence of such typical genera as Aquilegia, Tncarvillea, 

 Primulas of the Amethystma section, and Pinguicula alpina ; and to 

 the extreme poverty of such as Meconopsis, woolly Compositae, alpine 

 Leguminosae, Berber is, Cotoneaster , Lonicera, etc.? In view of the large 

 number of Rhododendrons, especially of the dwarf groups, we are, 

 forced to the conclusion that if it is simply a question of altitude — 

 and the highest peaks are little over 13,000 feet — then altitude affects 

 plants both absolutely and relatively. In other words, Rhodadendrons 

 flourish within 1,000 feet of the snow line, wherever the snow 

 line may be ; but Meconopsis for instance, flourishes only above 

 15,000 feet. 



We are now in a position to appreciate to some extent the part 

 played by the North East Frontier belt as regards distribution in 

 South East Asia generally. 



640-4 



