CONCLUSION 393 



of dispersal over land may apply also for at least the great majority of the 

 species in the Icelandic flora (E. Einarsson, this symposium). It goes almost 

 without saying that some of the truly Amphi-Atlantic biota in eastern North 

 America must have dispersed westwards in a similar manner. In addition, 

 glacial survival in Arctic America seems even more likely than in Scandinavia 

 for the simple reason that there a much larger land area may have been free 

 from ice north of the glaciation limits (cf. Ewing and Donn. 1956; Ives, this 

 symposium; Terasmae, 1961). 



Land-connections have been discussed by several contributors to this 

 symposium. Some biogeographers seem to hold the opinion, based on climatic 

 requirements of the biota, that a land-bridge must have connected at least 

 Iceland and Europe as recently as in late Pliocene (Dahl, this symposium). 

 Others have used paleobotanical data to indicate such a hypothetical connec- 

 tion as late as in the latter part of the Pleistocene (Sorensen, 1953) or during 

 the penultimate glaciation itself (Love and Love, 1956). However, the 

 possibility of such relatively recent connections over the Atlantic or parts of it 

 remains a matter of dispute and has so far received only limited support from 

 geologists (Heezen and Tharp, this symposium), but not from paleoclimatolo- 

 gists (Schwarzbach, this symposium). On the contrary, geological (Tr. 

 Einarsson, Schwarzbach, this symposium) and certain botanical (Hulten, 

 this symposium; Steere, 1937; Love and Love, 1953) as well as zoological 

 (Walden, Omodeo, this symposium) evidence seem strongly to uphold the 

 opinion that Iceland (or at least "Great Iceland", cf. Barth, 1941 ; Tr. Einars- 

 son, this symposium) has been an isolated island ever since the Middle 

 Tertiary, and that its present indigenous biota must be regarded as only 

 remnants of the flora and fauna which became isolated at that time. It 

 follows, if this reasoning is correct, that at least the "West Arctic" plants in 

 Scandinavia are survivors not only of the Pleistocene but relics from a still 

 more distant past when there was some kind of land-connection at least 

 between Greenland and Scandinavia. This is in conformity with the views 

 previously expressed by Nordhagen {he. cit.) and Nannfeldt {loc. cit.). 



The question arises what kind of connection over the North Atlantic made 

 possible at least a limited exchange of biota until the Middle Tertiary, but 

 because of the limited geological knowledge of the sea bottom in these regions, 

 the answer remains controversial. Though Tr. Einarsson (this symposium) 

 seems to favor the idea of a large Atlantic island (cf. Barth, 1941) somewhat 

 Hke the Scandic proposed by De Geer (1912), other possibilities remain open 

 and those who prefer, for example, one land-bridge over Iceland and another 

 over Svalbard (Cernohorsky, Hadac, Ronning, this symposium), or simply 

 some kind of continental displacement (cf. Heezen and Tharp, this sym- 

 posium) can still find support for these ideas with equally strong evidence. 

 However, the data presented by Lindroth and Walden and even Dahl (this 

 symposium) seem to back the opinion by Tr. Einarsson (this symposium) 



