CONCLUSION 



AsKELL Love 



Institut Botanique de TUniversite de Montreal, Montreal, Canada 



The science of biogeography, in the true and wide meaning of the term,"may 

 be defined as the exploration of the universe of Hving beings and the appHca- 

 tion of the laws of nature to the interpretation of the history of the distribution 

 and dispersal of biota. In this application the laws themselves are put to a 

 test and important explanations are constructed. Such was the case with the 

 theory of evolution which arose from the study of distribution, in time and 

 space, of plants and animals. 



It has been said that the most important step in getting a work started is 

 the recognition of a problem. Regarding the North Atlantic biota, this was 

 achieved already by Hooker (1862), or perhaps even by Humboldt (1817) 

 who recognized the close relationships between the biota in the far north of 

 Scandinavia and America. The second important step in the development of 

 this case was the collection of evidence for and against several working hypo- 

 theses coined to explain the relationship. Out of this emerged the theory of 

 survival of plants within the glaciated areas of Scandinavia (Blytt, 1876, 1 882; 

 Fries, 1913) replacing the now merely historical tabula rasa idea. 



The theory of glacial survival has been found to be one of the most fertile 

 ideas of biogeography, and much evidence has been sought in support of it 

 for almost a century. Naturally, most of this evidence has come from Scandi- 

 navia, but some also from North America, Greenland, Iceland, Svalbard, 

 and the British Isles. Many Scandinavian biogeographers have agreed that 

 this theory is the only available explanation for the distribution patterns of 

 certain biota in Scandinavia (cf. Dahl, 1961 ; Gjaerevoll, 1959; Lindroth, 1958; 

 Nannfeldt, 1958; Nordhagen, 1936; and in this symposium). 



Some of the reasoning regarding the North Atlantic biota and their history 

 may seem to have been somewhat circular in that biologists proposed geo- 

 logical possibilites and geologists tended to accept such conclusions as final. 

 Recently, this has changed in such a way that most biogeographers base their 

 conclusions on biological evidence only, at the same time as the conclusions 

 of most geologists rest on geological observations alone. Lately, the latter 

 have tended to doubt the possibility of recognizing ice-free refugia even from 

 the last glaciation (Holtedahl and Rosenquist, 1958; Hoppe, 1959; and in 

 this symposium), though they have not regarded it wise to deny completely 

 this possibiUty because of the strong biological evidence. 



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