PHYSICAL GEOGRAPHY 319 



On the strand sand, especially in South Iceland, there is a fairly 

 characteristic vegetation of Halianthus pephides, Cakile maritima, 

 Atriplex patula, Stenhammaria maritima and Potentilla anserina; 

 often, each of these species occurs separately and in abundance, but 

 sometimes they are found intermixed in various ways. Cakile ma- 

 ritima usually occurs nearest to the sea, and Potentilla anserina at 

 the highest levels, occupying large areas, and occurring so abun- 

 dantly that the ground is quite interwoven by its creeping shoots. 

 On the strand sand are also seen in small numbers Cochlearia offici- 

 nalis, Matricaria inodora, Silene maritima, Polygonnm aviculare, Stel- 

 laria crassifolia, S. media, Capsella bursa pastoris, Glyccria distans, 

 Festuca rubra, Elymus arenarius, Carex incurva, etc. On the vast 

 sandy stretches along the south coast blown-sand formations are 

 frequent nearest to the sea; here Halianthus peploides and Elymus 

 arenarius occur in tufts; above this belt of sand dunes, tracts are 

 found occupied by a vegetation richer in species and consisting of 

 Potentilla anserina, Festuca rnbra var. arenaria, Thymus serpyllum, 

 Galium uerum, Achillea millefolium, Juncus balticus, and several 

 others. But below the glacier-bearing mountains (Jokulls) the strand 

 sand quickh^ merges into glacier sand, which forms sandy wastes 

 extremely poor in plant-life. 



At several places along the coast of Iceland salt-marshes are 

 found, overflowed by salt w r ater, for example in Borgarfjordur, Myrar, 

 Hornafjordur and Lon. In Myrar the dominant species are Glyceria 

 maritima, Agrostis alba, Plantago maritima, Stellaria crassifolia, more- 

 over Heleocharis uniglumis, Triglochin maritima, Juncus bufonius, 

 several species of Carex, etc. H. Jonsson found that in some 

 places two-thirds of the area \vas occupied by Glyceria maritima and 

 one-third by Agrostis alba, each species occurred separately in patches; 

 some thick-leaved Plantago maritima occurred, however, in the Gly- 

 ceria patches 1 . 



The Vegetation of the Fresh Water. Plant-life occurs very 

 sparingly in running water, and where strong currents are felt it 

 is usually absent. Nor do plants appear to thrive in glacier-rivers; 

 this is probably due to the low temperature of the water and the 

 current. In slowly flowing river-arms on level land, in rivulets and 

 brooks there is often a considerable quantity of green algas (Zygnema 

 and Spirogyra), both at the bottom and upon the surface; in South 

 Iceland Enteromorpha intestinalis is common in streams. The fol- 



1 Bunadarrit. XX. 1906. pp.150, 151. 



