ICE AGE REFUGIA IN ICELAND 



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common in all the refugia except one, and outside of them it grows only in 

 such mountain ranges where there possibly have been ice-free peaks during the 

 glaciation of the Ice Age. In other locahties in the country P. radicatum is not 

 found. 



As mentioned before, there are six districts in the country where species 

 with centric distribution are concentrated. Outside these districts no such 

 tendencies are found, except for some anthropochorous plants, which have 

 obviously been introduced a comparatively short time ago. Below I will give 

 a short survey of the districts in question and the species with a central dis- 

 tribution occurring in each of them. 



Fig. 10. Botrychiuin boreale. 



1. The Eyjafjordur district is situated between the fjords Skagafjordur to- 

 wards the west and Skjalfandifloi and the valley Bardardalur towards the east. 



As mentioned before, 8 species of the West Arctic and North Atlantic 

 groups have distinct centers in the district, either only there or in some other 

 centers as well, i.e. being bi- or tricentric. Besides these, 33 species have a 

 fairly similar distribution, i.e. they have their central area in the Eyjafjordur 

 district, although most of them are also found in other possible refugia. 



I have divided these species into two groups, alpine plants and lowland 

 plants, according to whether their main distribution is above or below the 

 200 m line above sea level. 



The alpine group contains 18 species. Only 3 of them can be charac- 

 terized as unicentric in the Eyjafjordur district, i.e. Carex glacialis, Diapensia 

 lapponica, and Saxifraga foliolosa, but all of them occur in isolated localities 

 at nunatak areas outside the district. C. glacialis has a fairly wide distribution 

 east of the Eyjafjordur district, in almost continuous connection with it. 



Six species of the group are distinctly bicentric, Antewmria alpina, Botry- 

 chium boreale (Fig. 10), and Luzula sudetica have their centers in the Eyja- 



