306 



steind6r steindorsson 



The first striking feature in the distribution of a great many Icelandic 

 plants is the evident discontinuity, i.e. many of the plants seem to be accumu- 

 lated in cer:ain dist icts with large gaps in their distribution where no 

 natural obstacles can be observed to explain this discontinuity. 



Searching for the causes of this phenomenon one is led sooner or later to 

 the opinion that these species might be remnants of an older flora, one which 

 has been isolated in these areas. The only time such an isolation could have 

 taken place is during the Ice Age. 



Table 1 

 The Distribution in Iceland of West Arctic and North Atlantic Groups 



A fairly thorough study of the distribution of Icelandic plants made it 

 obvious that there are six districts which can be considered as centers of 

 distribution and occurrence of the various species; apart from them, a few 

 smaller areas were found in different parts of the country where the same 

 species occur. Comparing these plant centers with these districts, which 

 Thorarinsson (1937) has pointed out as possibly ice-free during the Ice Age, 

 on the basis of their landscape forms, it appears that they correspond sur- 

 prisingly well. The smaller areas are all situated at such places where there 



