THE 



BEITTLE BLADDER FERN. 



Cystopteris fragilis* BEENHAEDI. 



The Bladder Ferns (kystos is Greek for bladder) are 

 so called because the indusium, even in age inflated or 

 bulged out like a hood, has when young the look of a 

 flask or bladder. The plant differs in this from the 

 flatness (the sori in both being round) of the Poly- 

 stichums and Lastreas with which it was formerly 



* Polypodium fragile (Linnaeus), Aspidium fragile, Athyrium 

 fragile, Asplenium fragillimum. 



