CYSTOPTERIS. 



103 



triangular in outline, about Gin. each way (Fig. 21), instead of emanating 

 from either a compact crown or a short rhizome as in other kinds, are pro- 

 duced on very slender, underground rliizomes, such as are noticed in the 

 Marsh Shield Fern, Nephrodium {Lastrea) Thelypteris^ or in the common 

 Oak and Beech Ferns, Polypodium Dryopteris and P. Phegop)teris. They are 

 borne on slender, erect stalks, from Gm. to 9in. long, perfectly smooth, 



Fi^. 21, Frond of Cystopteris niontana 



(I nat. size). 



except near their base, where there are a few light -coloured scales, and 

 are quadri-pinnatifid (four times divided half-way to the midrib) and of 

 a light green colour. 



Eaton, who says that this species is one of the rarest North American 

 Ferns, states that it is found growing by the side of streams in shady alpine 

 woods in the Rocky Mountains of British America, and on the North Shore 



