314 



STEINDOR STEINDORSSON 



fjordur and Vestfirdir districts, but Antennaria may also have a center north of 

 Vatnajokull. Draho olpina, Erigeron eriocephalus, and Phyllodoce coerulea 

 (Fig. 11 ) are bicentric in the Eyjafjordur and Austfirdir districts. 



Five species are tri-centric in the Eyjafjordur, Austfirdir and Vestfirdir dis- 

 tricts: Botrychium lanceolatiinh Draba nivalis, Erigeron uniflorus, Phippsia 

 algida, and Ranunculus glacialis, but all of them except Botrychium also 

 occur in nunatak areas. Ranunculus glacialis does not have such a distinct 

 centric distribution as most of the centric species. 





c:^ 



Fig. 1 1. Phyllodoce coerulea. 



Finally, there are 4 polycentric species: Cardamine bellidifolia, Minu- 

 artia biflora, Saxifraga cernua and Ranunculus pygniaeus. The first 2 occur 

 in all the possible refugia except Myrdalur and Hvalfjordur, but the last 2 

 are missing in Myrdalur and Breidifjordur. All of them occur in nunatak 

 areas. 



All the species of this group are considered either genuine or at least 

 probable survivors in Scandinavia, and some of them in North America and 

 Greenland as well. 



The lo}\ land group contains 15 species. Three are unicentric, i.e. Agropyron 

 trachycaulum {Roegneria borealis var. islandica), Carex flara (Fig. 12). and 

 Crepis paludosa (Fig. 13). Four species are bicentric: Agropyron {Roegneria) 

 caninum, Carex livida (Fig. 12), Primula stricia (Fig. 14), and \'iola epipsila 

 (Fig. 15) have a second center in the Austfirdir district, but Carex livida seems 

 to have a third center in the nunatak area of the Sniefellsnes. Potentilla 

 Egedii occurs also in the Hvalfjordur district. None of these species except 

 Carex livida occurs in nunatak areas. 



