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STEINDOR STEINDORSSON 



its second center in the Eyjafjordur district, but is also found in a nunatak 

 area closely connected with the Austfirdir district. All the other species are 

 polycentric. 



Admittedly, only half of the centric species of the Vestfirdir district are 

 considered as overwinterers in other countries. But the similarity between 

 their distribution and that of other centric species can hardly be explained if 

 overwintering were not the case. 



As an example of such species 1 will take Melampyrum silvaticum 

 (Fig. 18). Its main center is in the Vestfirdir district where the locahties are 

 concentrated in three separate groups in the fjords: Thorskafjordur, Isaf- 

 jordur, and Steingrimsfjordur-Bjarnarfjordur. Although the distance between 



Fig. 18. Melampyrum silvaticum. 



these areas is not very great, it is not likely that the plants have been dis- 

 tributed from the same center. It is more probable that they have survived in 

 small refugia and have not spread beyond their immediate vicinity, which has 

 also been the case with many of the species that have their centers in the 

 refugial districts. It is difficult to believe in Post-glacial migration of this 

 species into these remote places where the climate is rather rough and cold, 

 as long as the plant has not yet established itself in the forests in other parts of 

 the country. Outside Vestfirdir the species occurs at only one locality. 

 Faskrudsfjordur in the Austfirdir district. As already mentioned, the distribu- 

 tion of M. silvaticum indicates distinctly that the species is an overwinterer. 

 And if that is so, and this is a species rather sensitive to cold and also a forest 

 plant which has been able to survive in refugia throughout the last Glacial 

 period, the possibilities are undeniably great for the survival of a great part of 

 the Icelandic flora in such refugia. 



