42 TRAXSACTIOXS OF THE [Sess. lxxx 



iiig more or less close relationship : namely, a western, 

 an eastern, and a southern, to be called respectivel}" the 

 Himalayan, the North China, and the Burma- Yunnan 

 tioras. For this purpose we will take the genus Prhnula, 

 as, Primula-hunting having become a cult, a very large 

 number of species are known and the genus has been the 

 subject of classical work. It is an Eurasian genus, and only 

 one species in either hemisphere extends south of the 

 Equator. Primula is divided into a number of sections 

 based chiefly on similarity of habit and foliage, shape and 

 method of dehiscence of the capsule, type of flower, 

 inflorescence, and so on. 



Taking Professor Balfour's classification, and looking at 

 the three plant areas we have mapped out as the result of 

 breaking the Sino-Himalayan range, we ought to find, if 

 the genus Primula typically represents the case : — 



(i) A Himalayan Primula area with endemic species, 

 (ii) a North China Primula area with endemic species, and 

 (iii) a Burma- Yunnan Primula area richer than either of 

 the others in endemic species, but related to both. Area (i) 

 should differ widely from area (ii) — more so than it differs 

 fi'om (iii), the far ends especially being in contrast Avhile 

 the two ends at the break might not differ so widel}?' ; but 

 area (iii) should show obvious connecting links with both 

 (i) and (ii), having derived elements from both, especiallj^ 

 in the north, in the region of the break, though there is 

 always the possibility of such links being completely wiped 

 out in such a vortex of change, with two or three different 

 floras crowding througli this narrow gap. 



Now what do wc actually find to be the case ? 



To begin with, Bhotan and Sikkim together form a very 

 rich Priunila area — the richest known till the exploration 

 of Yunnan was begun by the French Catholic priests 

 and carried on so successfull}^ by Forrest ; the eastern end 

 of the Himalayas may be regarded as area (i), which, as 

 Sir George Watt points out, grows poorer (in Primulas) 

 towards the north-west, while the types attain their fullest 

 development towards the south-east, that is to say, in area 

 (iii). Area (ii) comprises Eastern Szechwan, and extends 

 nortliwards into Kansu and eastwards through Shensi, 

 where the Sin-linii- ranoe is well defined. Its western 



