BRITTLE BLADDER FERN. 51 



does best in the interstices of a wall, where the mortar 

 has begun, to crumble. In. pot culture the soil should 

 be prepared with great care : old crumbled mortar, 

 peat earth, and limestone or oolite, should be well 

 mixed together, and placed in shade. It is generally 

 supposed that it is impossible to grow this fern in 

 the atmosphere of London ; yet Mr. Sowerby tells 

 us that the best specimen he ever had flourished in 

 the old wet mortar of a wall in Hatton Garden, 

 where not a ray of sunlight ever reached it, and where 

 the atmosphere was as full of London smoke as it is 

 anywhere. 



BRITTLE BLADDER FERN. 



CTSTOPTERIS FEAGILIS. 



\Bernkardi, Hooker and Arnott, jBabington, Moore, 

 and Newman] 



(Fig. 21.) 

 SYNONYMS. 



CYSTEA FKAGILIS. Smith. 

 CYATHEA FRAGILIS. Some authors. 

 POLYPODIUM. Linnaeus. 



THE whole of this genus consists of small fragile 



but beautiful and interesting ferns. They are all more 



delicate in texture than most of our native ferns. 



The present species has fronds from five to six 



E 2 



