SURVIVAL OF PLANTS ON NUNATAKS IN NORWAY 



263 



10 (species and subspecies) in the southern one and about 30 in the northern 

 one. In numerous papers (Nordhagen, 1931, 1935; Nannfeldt, 1940) strong 

 evidence is given for the probability that this centricity must have a historical 

 explanation. Briefly recapitulated, this explanation is to the effect that there 

 must have been two areas where the glaciation has not been total: one area of 

 ice-free refugia in the district of More, another from about the Polar Circle to 

 western Finnmark. Owing to the reduced ability and possibility of dispersal of 

 some of the species a centric distribution has been formed. By far the greater 

 part of the problematic species of the Scandinavian alpine flora is found in 

 these two areas. 



Fig. 2. The total distribution of Rhododendron lapponicinn (inch R. parvifolium) 



(after Hulten, 1958). 



Blytt also indicated an American-Greenlandic element in the Scandina- 

 vian flora. Today the species belonging to this element in Scandinavia are 

 called West Arctic. They total about 30 taxa most of which belong to the 

 centric groups. Nearly all of them are found in the northern area, but only 

 one-third in the southern one. 



Rhododendron lappouicum in Europe is only known from Scandinavia 

 where it occurs — often predominating — within a large area in the north, and 

 a small one in the south, thus it belongs to the bicentric species (Fig. 2). 



Pedicidaris flammea is, in the same manner, very distinctly a West Arctic 

 species, but it is restricted to the northern area (Fig. 3). 



There are also some eastern species displaying the same distribution. 



