306 THORODDSEN 



Empetrum nigrum - a miserable stunted specimen of each of these 

 two species, 2 and 2 l /2 cm. in height respectively. On the plateau 

 towards the east: Kjarrdalsheidi near Lon (665 metres), Salix 

 herbacea, Polygonum viviparum, Oxyna digyna, Ranunculus glacialis, 

 all small and stunted. Markalda (961 metres) near the eastern 

 edge of Vatnajokull, Polygonum viviparum, Armeria maritima, Salix 

 herbacea, Saxifraga nivalis. Litla Snaefell (1133 metres), Salix her- 

 bacea, Oxyria digyna, Arabis alpina, Ranunculus glacialis. On Hlid- 

 arfjall near Myvatn (790 metres) where I was together with Gron- 

 lund in 1876, we noted the following plants: - - Alsine biflora, Draba 

 nivalis, Saxifraga cernua, Cassiope hypnoides, Pedicularis flammea, 

 Oxyria digyna 1 . 



All that is situated outside the glacier-bearing mountains in the 

 centre of Iceland at an altitude of 650 1100 metres may justly be 

 regarded as a desert; seen both from a geological and geographical 

 point of view the country here is desert-like in character, and in 

 spite of considerable precipitation the plants suffer from drought, 

 because the water disappears immediately over large areas owing 

 to the porous nature of the rocky substratum - lava, tuff, volcanic 

 gravel and sand. The few plants which grow in these wastes occur 

 widely scattered; at a height of 900 1000 metres above sea-level a 

 few 7 lichens and mosses are seen only here and there, and at long 

 intervals a few specimens of the hardy Armeria maritima, Silene 

 maritima and Polygonum viviparum and in places where blown sand 

 occurs a few 7 tufts of Elymus arenarius; at a height of 1000 1100 

 metres one may ride for miles without coming across a single pha- 

 nerogam. In addition to want of water, the frequent storms, often 

 of sand and snow, check plant-growth during the short summer; 

 moreover, a rather dry Form wind often blows across the wastes 



/ 



north of the great Jokulls, having already deposited its moisture 

 upon the great plateaus of the Jokulls. Somewhat lower down, at 

 an altitude of 700 900 metres, a few more species are met with 

 as scattered individuals, e. g. Silene acaulis, Arabis alpina and A. 

 pelrcea, and here and there a few haulms of Luzula arcuala, Poa 

 glauca or Fesluca ovina\ moreover, a few scattered cushions or tufts 

 of lichens (Stereocaulon) or mosses (Grimmia) occur. 



Scattered here and there in these extensive wastes are sometimes 



1 See also Chr. Gronlund's list of plants from Heljardalsheidi and Hrafn- 

 tinnuhryggur. and the list of plants collected by Johnstrup on Dyngjufjoll (Karak- 

 teristik af Plante-v;eksten paa Island, 1884, pp. 28 and 29). 



