THE BLADDER FERNS. 



81 



the frond. The whole texture of the frond is delicate and 

 herbaceous, as in the more common species, and hence the 

 veins show very distinctly: in the ultimate pinnules the 

 central vein is somewhat flexupus, and gives off alternate 

 lateral veins, one of which is directed towards the sinus or 

 marginal indentation between two serratures. The sori 



Tio. 23. 



Cyttopterii montana. 



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 a blunt, concave, jagged-edged indusium. 



This rare species occurs only among the Breadalbane 

 mountains of Scotland, and in the Clova Mountains in For- 

 farshire. In the European Alps it is met with, most abun- 



