Recognition: small fern with dull, translucent fronds, creeping on the ground or on tree trunks. The sori (the aggregations of the spore-producing sporangia), which occur at the apices of the frond segments, are often paired. The frond is hairless and its margins untoothed. One of the most common filmy ferns in New Zealand, and the most likely to be extensively growing on the ground.
Distribution/ecology: only found in New Zealand. In lowland and montane forest throughout, but less common in the eastern South Island.
Relationships: 21 species of Hymenophyllum filmy fern are recorded in New Zealand. 14 are only found in New Zealand, while the others extend variously to Australia and the Pacific Islands. They are distinguished primarily by whether the fronds bear hairs, whether the frond margins are toothed, and by the nature of the sori.
Hymenophyllum is a member of the Hymenophyllaceae fern family, whose other indigenous representatives are Cardiomanes and Trichomanes. Cardiomanes comprises the aptly named kidney fern (Cardiomanes reniforme). There are five species of Trichomanes in New Zealand. The most common is Trichomanes venosum (veined bristle fern) which is a frequent epiphyte on tree ferns in lowland forest, and is recognised by the branching veins in each frond segment and the tubular indusia (structure housing the sori).