The Botany of Iceland - 01.12.1914, Side 145

PHYSICAL GEOGRAPHY
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fragilis,. but also flowering plants, such as Sedum annuam, O.vyria
digyna, Plantago maritima, Saxifraga cœspitosa, Poa glauca, Festuca
ovina, and others. On damp rock-faces near large waterfalls these
same species are met with, often as large, well-developed speciinens
(H. Jonsson, 1905, p. 30); also Poa alpina f. vivipara, Aira alpina,
Saxifraga hypnoides, S. stellaris, S. nivatis, S. cœspitosa and several
Fig. 31. The river Thverá in Öxnadal. Epilobium latifolium and Aira on a small
gravel-island in the river; July, 1909.
(Phot. A. Ilesselbo.)
species of mosses. Nowhere is seen so mixed and variegated a plant-
society as on extensive, fairly densely plant-covered mountain slopes
where the majority of the plant-formations are met with, in patches,
side by side. On a talus of fallen blocks and débris (urd) there is
often a considerable vegetation of lichens, mosses and liverworts.
In some places, especially far up on the mountains, the sloping
heaps of rock-fragments are poor in plants; in other places they
carry a rich vegetation of ferns or willows and birch shrubs and
heather, with a variable admixture of herbaceous plants from dif-
ferent formations, with no special character, the vegetation resembling
closely that which occurs in ravines and lava-clefts.
Where the conditions of life are specially favourable; where the