118 TRANS ACTIOXS OF THE [Sess. lxxxi 



of the whole section, spreads beyond the confines of Asia, 

 ranging from Japan to Ireland, Greenland, and across N. 

 America. The groups of species into which Rhodiola has 

 been divided above show more or less well-marked centres 

 of distribution, sometimes contradicted (as is so often the 

 case when one is dealing with distributional problems) by 

 some notable exception. 



.Series Rhodiolae sensu stricto. — Of some twenty species, 

 rather more than half are Himalaj^an plants, and almost 

 all of these are confined to that region ; but one of them 

 (»S'. roseuin) is the most widespread of all the Rhodiolas. 

 Four have a wide range over Central and Eastern Asia, 

 two are confined to Tibet, and two to Western China. 



Series Crassipedes. — Of nineteen species, eight are 

 Chinese (mainly Yunnan), five Himalayan, four come from 

 Siberia, Turkestan or Tibet ; and one (S. rhodanthum) 

 from Western X. America. 



Series Primuloides.— The Longicaules group have their 

 homes far apart — one in Afghanistan, two in Yunnan, and 

 one in Quelpaert ; while of the Brevicaules, four come from 

 Tibet, one from the Himalayas, one from Central Asia, and 

 one from China. 



Roughly speaking, half the Roseae are confined to the 

 Himalayan region, half the Crassipedes to China, and half 

 the Primuloides to Tibet ; if we take those three regions as 

 constituting a single area, we find that to that area are 

 confined about three-fourths of the Roseae and Crassipedes, 

 and practically the whole of the Primuloides : in other 

 words, nearly four-fifths of the whole section Rhodiola. 



