Plant delicate, up to 25 cm. Prothallus perennial, often obvious, bilobed, 7-10 mm long, attached to a swollen, summer-persistent tuber. Sporophyte annual, with up to 6-8 fronds, petiole as long as the lamina, slender, smooth, polished, blackish brown below, pale straw above, lamina of first leaf reniform, of later leaves bipinnate, lanceolate, with 6-7 pinnae, thin, ultimate segments triangular to ovate, bilobed at apex. Sori naked, elongate along veins. Spores tetrahedral. Spores ripe 4-7. On dry rocks, 30-1000 m.
Mediterranean area N to Switzerland, W. France & Channel Islands, Crimea, N. America; scattered to S. Africa, India & Australasia.