- bladder fern - any fern of the genus Cystopteris characterized by a hooded indusium or bladderlike membrane covering the sori
--1 is a kind of fern
--1 is a member of Cystopteris, genus Cystopteris
--1 has particulars:brittle bladder fern, brittle fern, fragile fern, Cystopteris fragilis; mountain bladder fern, Cystopteris montana; bulblet fern, bulblet bladder fern, berry fern, Cystopteris bulbifera