184 
HISTORY OF BRITISH FERNS. 
vein is somewhat flexuous, and gives off alternate lateral 
veins, one of which is directed towards the sinus or margi- 
nal indentation between two serratures. The sori have the 
roundish form common in this genus, and, being often 
numerous, they then become very conspicuous when full- 
grown ; but though crowded, they do not appear often to 
become confluent. These sori are covered, in the young 
state, by blunt, concave, jagged-edged indusia. 
This rare species was supposed to occur wild in the 
United Kingdom only, among the Breadalbane mountains 
of Scotland, on one of which, Ben Lawers, it was originally 
found in 1836 by Mr. Wilson, in company with Sir W. J. 
Hooker and Professor Graham. It has subsequently been 
found in other parts of the same region ; and more recently 
by Mr. Backhouse in the Clova Mountains. It grows in 
very wet shady places, on the ledges of the rocks. In the 
European Alps this Fern is met with, most abundantly 
northwards ; and it also occurs on the Rocky Mountains 
of the New World. 
The synonyms of this species are Polypodium montanum, 
Aspidium montamm, Gyathea montana^ Cystopteris Alii- 
oni, and Cystopteris myrrhidifolia. 
