320 STEiNDOR steind6rsson 



There still remain 15 species which either occur in these 2 last mentioned 

 districts or are found in all the six possible refugial districts, but not outside of 

 them except in nunatak areas. 



In the foregoing, six districts have been pointed out as probable refugia for 

 biota during the Ice Age. In them some 100 species occur, the modern distribu- 

 tion of which is almost exclusively limited to inside the districts mentioned, 

 or outside of them only in such places where the landscape indicates nunataks 

 during the glaciation. 



Postglacial immigration of these plants does not seem probable, as in that 

 case they might have taken root just as easily in other parts of the country 

 which they do not. The same would hold true for all other sections of Iceland. 

 If we put it the other way around, i.e. that ice-free areas existed at least 

 during the last glaciation, the concentration of centric species in special 

 hmited areas is quite natural. As far as our present knowledge reaches, no 

 more probable explanation of that phenomenon can be put forth, especially 

 since a great majority of the centric species in Iceland are exactly the same as 

 established survivors of the Ice Age in other northern countries. 



REFERENCES 



Gelting, p. (1934). Studies on the vascular plants of east Greenland between Franz 

 Josephs Fjord and Dove bay. Medd. om Gronl. 101 (2), 1-340. 



LiNDROTH, C. H. (1931). Die Insektenfauna Islands und ihre Probleme. Zool. Bidrag fr. 

 Uppsala 13, 105-599. 



Love, A. and Love, D. (1956). Cytotaxonomical conspectus of the Icelandic Flora. Acta 

 HortiGotoburg. 20, 65-291. 



NoRDHAGEN, R. (1935). Om Aienaria humifusa og dens betydning for utforskningen av 

 Skandinavias eldste floraelement. Berg. Mm. Arbock 1935, Naturv. rekke 1, 1-183. 



StefAnsson, S. (1948). Flora Islands, 3. utg. (Steindor Steindorsson ed.) Akureyri. 



Steindorsson, S. (1937). Jurtagrodurinn og jokultiminn. Ndttitrufr. 7, 93-100. 



Steindorsson, S. (1949). Florunyjungar 1948. Ndtturufr. 19, 110-121. 



Steindorsson, S. (1962). On the age and immigration of the Icelandic flora. Soc. Sclent, hi. 

 35, 1-157. 



Thorarinsson, S. (1937). Vatnajokull. Scientific results of the Swedish-Icelandic investiga- 

 tions 1936-1937, Chapter II. The main geological and topographical features of Ice- 

 land. Geogr. Ann. 1937, 161-175. 



