158 FIRST FORMS OF VEGETATION. 
and Andes as well as the British mountains. But 
it is in the Arctic regions alone that they 
luxuriate, covering the surface of every rock, to 
the level of the sea-shore, with a gloomy 
Plutonian vegetation, that seems like the charred 
cinders and shrivelled remains of former verdure 
and beauty. I gathered magnificent specimens 
of two members of the family Umbilcaria 
pustulata, and U. spodochroa, on rocks a little to 
the south of Christiansand, and on the rocks 
below the fortress in the harbour of Bergen in 
Norway. They grew in these two places in the 
utmost profusion, and to an enormous size; 
whereas on the heights of the Dovrefjeld, where 
I expected to see them still larger and more 
abundant, I found only a few dwarfed individuals. 
They seem to reach the maximum of their 
development in the extreme south and at the 
sea-level, decreasing in size and number as we 
proceed northward and ascend the high moun- 
tains. We are accustomed to regard the Um- 
bilicaria pustulata as an Alpine lichen in this 
country, but I have never gathered it on moun- 
tains, and the only spot in which I have seen it 
attaining anything like the size of Norwegian 
specimens was on rocks of hypersthene around 
the shores of Loch Corruisk in the Isle of Skye. 
In that wild scene it grew to the size sometimes of 
