Ferns of the Forest Floor
There are 28 species of filmy ferns of the family Hymenophyllaceae found in New Zealand. The fronds are thin and delicate and the sporangia are conspicuous; they are borne on receptacles which sometimes project from the margins of the leaves. Filmy ferns are found throughout the country; the largest forms and most luxuriant grow in the damp forests. They vary from the large Hymenophyllum dilatatum, which may reach 2 ft in height, to the tiny H. minimum, less than 1 in. high. Under suitable conditions Mecodium dilatatum may also grow to a large size, and other minute forms are Sphaerociarium lyalli and Craspedophyllum armstrongii. The kidney fern, Cardiomanes reniforme, with undivided leaves fringed with prominent sori, is common throughout the country. Some members of this family are matforming; others are tufted, as the lovely Mecodium pulcherrimum, the stiff little Selencodesmium elongatum with protruding receptacles, and Macroglena stricta.