1915-16.] BOTANICAL SOCIETY OF EDINBURGH 45 



sections being represented in all three areas; it is note- 

 worthy that only one section (Malvacea) has representatives 

 in the North China and Burma-Yunnan areas, but not in 

 the Himalayas ; and only one section (Farinosa) has repre- 

 sentatives in the North China and Himalaj^an areas, 

 missincr the Burma-Yunnan area. But the section Farinosa 

 is as much American as Himala^^an, and may have reached 

 Asia via the Aleutian Islands or by whatever route the 

 American flora travelled west — though I think it more 

 likely that both floras were derived from a common source, 

 and radiated from the far north, than that an actual 

 emigration took place. 



Thus we see that seven wideh" distributed sections have 

 representative species in all three areas, while most of the 

 others which occur in the Himalayas spread south into the 

 Burma- Yunnan area, and are represented there by a larger 

 number of species than in the Himalayas.^ This is the 

 case with six out of eight sections confined to these two 

 regions, but the increase of species is conspicuous in no less 

 than nine sections, including those with forms in North 

 China as well. In two groups confined to the Himalaj^an 

 and Burma- Yunnan areas (Minutissima and Sphaeroce- 

 pliala) and in one common to all three areas (Soldanelloides) 

 there is a decrease in passing from the Himalayan to the 

 Burma- Yunnan area. Finally, two Himalayan sections 

 (Farinosa and Verticillata) have no representatives in the 

 Burma- Yunnan area. The former is, as already remarked, 

 as much American as Asiatic, and had probably spread 

 over Asia long before the break in the Sino-Himalayan 

 range was formed ; there is no a 'priori reason why it 

 should have travelled south with other forms, though it 

 may have done so and since disappeared, or forms of this 

 section may yet come to light in the South. The latter is 

 a N.W. Himalayan tjq^e developed in Afghanistan and 

 Abyssinia. These exceptions, if they are exceptions, ma}- 

 all need correction as the exploration of Yunnan and 



1 Sir George Watt, of course, more than hints at the same conchision 

 when he says : " The forms that spread eastwards from Sikkim to 

 Assam, Burma, and Manipur are seen to belong to an assemblage that 

 attains its greatest development in China, more especially in the 

 mountains of the province of Yunnan" (Observations on Indian 

 Primulas). 



