CLIFFBRAKE

(Pellaea species), any of about 80 species of ferns of the genus Pellaea (family Adiantaceae or Sinopteridaceae, depending on the authority consulted). Cliffbrake ferns grow on or among rocks, mostly limestone, throughout the world. Small plants with blue-green leaves, they are characterized by spore-bearing structures (sporangia) that occur in round or elongated clusters (sori) on the margins of fertile leaves. Overlapping leaf margins form a protective covering. The name cliffbrake is sometimes used for rockferns or rock brakes, about four to seven species constituting the genus Cryptogramma, native to Europe, Asia, and both Americas. They differ from Pellaea species by having fragile, light-coloured stalks.