74 
BRITISH FERNS. 
tooth. Almost each vein bears at its termination a 
cluster of capsules of a roundish form, which contain 
the seeds: these increase very rapidly, and at last 
become confluent. 
This beautiful little fern is distributed widely over 
the United Kingdom, and prefers moist and moun¬ 
tainous districts, in the fissures of rocks, or the in¬ 
terstices of stone walls. It is rare in Ireland. It is 
found all over the world in favourable situations, 
extending even to the Arctic regions. The varieties 
are easily distinguished. They are : 
Cystopteris fragilis dentata, which is smaller 
than the original fern, and always blunter in form. 
The veining is similar, but the fructification is at the 
margin and not near the middle of the secondary 
vein. One great distinction from the Brittle Bladder 
Fern is that the clusters of sori as they ripen form a 
brown ridge on the under surface of the pinnules. It 
is found in the north of England chiefly. 
Cystopteris Dickieana is a variety of fragilis 
having a very compact frond. It may be distin¬ 
guished by its deflexed overlapping pinnae ; the pin¬ 
nules decurrent, broad, obtuse, with a few shallow 
marginal teeth. It is of a deep green colour and 
very transparent. It has only been found by Dr. 
Dickie in sea-caves near Aberdeen, after whom it was 
named. 
Few ferns can be cultivated with greater facility 
