Hymenophyllum tunbrigense

Hymenophyllum tunbrigense, the Tunbridge filmy fern or Tunbridge filmy-fern, is a small, fragile perennial leptosporangiate fern which forms large dense colonies of overlapping leaves from creeping rhizomes. The common name derives from the leaves which are very thin, only a single cell thick, and translucent, giving the appearance of a wet film. The evergreen fronds are bipinnatifid, deeply and irregularly dissected, about 3 to 6 cm long, 2 cm across with dark winged stipes. In contrast to the similar H. wilsonii the fronds are more divided, flattened, appressed to the substrate and tend to have a bluish tint. The fronds are monomorphic and produce sori along the frond segments close to the rachis. Up to 5–10 purse-shaped sori are produced per frond, each covered by two strongly convex, flattened indusial valves. The valve margins are jagged and used to distinguish H. tunbrigense from H. wilsonii, where the edges are entire. In common with all ferns, H. tunbrigense exhibits a gametop......read more on Wikipedia.