PHYSICAL GEOGRAPHY 331 



with blown sand. Where the sand-covered tracts reach the shore 

 their outermost border supports a halophilous vegetation which, at 

 a short distance from the coast, is replaced by the common plants of 

 sandy soil and rockv flats. On gravelly tracts of sand in the low- 



\J *f V 



lands the following plants are the commonest: Sz7e/ie maritima, Ar- 

 meria maritima, Festnca rnbra, v. arenaria, Carex incnrva, Agrostis 

 alba, Jiincns bullions, Elymus arenarins and Polentillu unserina; also 

 Gulinm vernm and T hymns serpijllnm, often occurring in patches. 

 Although the vast stretches of glacial sand in South Iceland have 

 a fairly variable surface yet they are extremely poor in plant-life; 

 owing to "glacier-bursts," and to glacier-rivers constantly causing 

 floods and changing their courses, the vegetation has rarely the chance 

 of development. On Skeidararsandur (cf. H. Jonsson, 1905, pp. 20 22) 

 the following plants occur widely scattered: Chamcenerium latifolinm, 

 Arabis petrcea, Silene maritima, Saxifraga opposilifolia , S. ccespitosa 

 and Poa glanca, also small patches of Grimmia hypnoides; but there 

 are, in addition, large stretches quite naked and entirely destitute 

 of plant-life. The main part of Myrdalsandur is a desert almost 

 devoid of vegetation ; far apart occur a few specimens of Arabis 

 petrcea, Silene marilima and Elymus arenarins; usually there is no 

 vestige of plant-life, and one may ride for hours without seeing a 

 single plant. In a few localities in Breidamerkursandur and Skei- 

 dararsandur there is open grass-vegetation in small oases where the 

 sandy gravel from some cause or another has for some length of 

 time escaped inundation by the ice-cold glacier water; in such 

 places, in addition to Chamcenerium latifolinm there occurs usually 

 Agrostis alba, Poa alpina, P. glanca, Aira alpina, Calamagrostis stricta, 

 Festnca ouina, F. rnbra v. arenaria, Carex incnrva, Jnncns bullions. 

 J. triglnmis, Lnzula spicala, Salix lanata, Oxyria digynu and others. 

 As may be seen, there is nothing specially characteristic in the 

 vegetation of these tracts of glacial sand and if they were rescued 

 from the destructive effect of the glacier-rivers, they would quickly 

 become covered by the various plant-formations of the level country: 

 we have already mentioned one such instance, when Brunasandur 

 in 1783 was rescued from the inundations ot glacier-rivers by a 

 lava-stream, which pushed a large rtver aside. 



Blown sand supports a somewhat more peculiar flora, the 

 characteristic plant being Ely inns urenurins; but where it is very 

 mobile, as e. g. on the plateau in the neighbourhood of Fiskivotn 

 and between Tungna and Skafta, no plant-life can thrive on it. 



The Botany of Iceland. I. 22 



