Topic: fork fern
Is part of topic Common New Zealand ferns
Recognition: pendulous stems with spirally arranged leaves. The sporangia (spore producing structures) are rounded and in pairs.
Distribution/ecology: occurs in New Zealand and Australia. In New Zealand it occurs in lowland to montane forest throughout, but is less common to the south. It is usually a hanging epiphyte on the trunks of tree ferns.
Relationships: five Tmesipteris species occur in New Zealand, the two most widespread being Tmesipteris elongata and Tmesipteris tannensis. The sporangia of Tmesipteris tannensis are distinctly pointed. Tmesipteris horomaka is similar, but only known from Banks Peninsula. In Tmesipteris lanceolata, the leaves at the apex of the stem are flattened into one plane rather than being spirally arranged. In Tmesipteris sigmatifolia, the sporangia are spherical and at least some of the leaves are sigmoid (curved somewhat like an ‘S’). Both Tmesipteris lanceolata and Tmesipteris sigmatifolia are more frequent in the northern North Island, with the latter associated with kauri (Agathis australis).
Australia and New Zealand are the strong holds for Tmesipteris, with a few species occurring in the (south) Pacific Islands and one in eastern Asia. There are only about 14 species in the world.
Tmesipteris is related to Psilotum, also atypical-looking ferns (two widespread species, with one in New Zealand). They comprise the Psilotaceae fern family, whose closest relative is the Ophioglossaceae (represented in New Zealand by indigenous species of Botrychium and Ophioglossum). These two families are only distantly related to other ferns.