Variable. Tuft of delicate 2-3 pinnate, lanceolate fronds, 5-30cm long. Long stalks, dark-brown with scales at base, green with fewer scales above. Two rows of sori, on each side of the mid-rib, covered by inflated white, oval indusia.
Mainly found in west and north Ireland on base-rich rocks, in damp, shaded rock-crevices and on walls.
Similar: Diaphanous Bladder-fern, Cystopteris diaphana
Brittle Bladder-fern, Cystopteris fragilis. Comeragh mountains, Co.Waterford. July 2009