BOTANY. 
269 
torrents. Most of the known alpine species of 
Jungermannia are also natives of Iceland, and 
some new ones, the loss of which I peculiarly 
regret. Of Lichens there are comparatively but 
few, as, indeed, may reasonably be expected from 
the extreme scarcity of trees, to which so many 
of them are exclusively attached; and even the 
rocky species are far from abounding; the lava, 
which covers so great a proportion of the island, 
being eminently unfavorable to the growth of 
them. On the primitive mountains I observed 
the more common crustaceous Lecidece and Bar- 
melice, with some others unknown to me, which 
the exceeding severity of the weather prevented 
my examining carefully in their places of growth, 
and the exceeding hardness of the stone prevented 
my getting specimens of. The perennial snow 
that caps the higher hills, forbids any of them 
to grow on very high elevations, as in more tern- 
perate climates; in the plains Bceomyces ran- 
giferinns s so useful in Lapland as the food of the 
reindeer, is found in the greatest profusion and 
luxuriance, and the singularly elegant Cetraria 
nivalis , which is almost equally abundant, though 
always barren, makes amends by its beauty for 
the absence of a greater variety of species. The 
shores of the island are too much exposed to the 
most heavy and tempestuous seas, to suffer the 
