392 ASKELL LOVE 



It is extremely difficult to reconstruct biological history when there are no 

 fossils and if all conclusions must be based on the distribution patterns of the 

 surviving populations. This has been the main problem in the investigations of 

 glacial survival in Scandinavia and North America. Although palynologica, 

 studies have added much information on the occurrence, recolonization and 

 extinction of some plants and on certain variations in distribution patterns, 

 such studies usually cover only the Late and Post-glacial periods in areas south 

 of the ice-border or made available by the retreating ice (cf. Deevey, 1949; 

 Godwin, 1956; Iversen, 1958). 



One of the most important contributions from this symposium is the 

 furnishing of definite paleobotanical evidence in support of the glacial survival 

 theory. This evidence comes from Iceland, where volcanic activity throughout 

 the Pleistocene has secured the conservation of extensive fossiliferous deposits 

 from the Interglacials (Thorarinsson, Th. Einarsson, in this symposium). In 

 fact, the Icelandic layers show not only that plants, including trees, survived 

 the glaciations within the country, but also that the flora of this island has 

 diminished gradually during the Pleistocene and that some species which were 

 dominant in the first Interglacials have become extinct in the latter. Logically, 

 this must be regarded as a fully satisfactory proof that plants and animals 

 have been able to survive the Pleistocene glaciations also in other countries 

 where no paleological remains have been found and where the only indications 

 left are met with in form of peculiar distribution patterns. 



This carries us back to Scandinavia. As mentioned by Fsegri (this sym- 

 posium), it is possible that the bicentric distribution of certain plants in the 

 Norwegian mountains may be explained as a consequence of climatical 

 variations after the glaciations. This argument is, however, considerably 

 weakened by the occurrence of multicentric areas in Iceland for several plants 

 whose present distribution within the country must have been affected by the 

 glaciation, as shown by Steindorsson (this symposium). There are, however, 

 several species in Scandinavia v/hich cannot have invaded their areas from 

 southern or eastern localities in Europe following the retreat of the ice for 

 the simple reason that they have never grown there. These are the species 

 belonging to the element termed "West Arctic" by Blytt (Joe. cit.), i.e. the 

 American-Arctic element in the European flora. It is apparent from the 

 statements by D. Love and Dahl (this symposium) that long-distance dis- 

 persal over oceans or ice is in this case hardly even a remote possibility, because 

 the radius of dispersability of these plants is much smaller than the present 

 distance to their nearest populations. The hypothesis is also supported by 

 the fact that these plants in Scandinavia are very rare and local though 

 apparently appropriate habitats are available in many localities close by their 

 present areas there. Hence, the "West Arctic" species must have arrived to 

 Scandinavia over some kind of a land-connection and hardly only over the 

 present lands, as partly suggested by Hulten (this symposium). The same sort 



