Nomenclature
Scientific Name:
Hymenophyllum nephrophyllum Ebihara & K.Iwats. in Ebihara et al., Blumea 51: 234 (2006)
Synonymy:
  • = Trichomanes reniforme G.Forst., Fl. Ins. Austr. 84 (1786)
  • Cardiomanes reniforme (G.Forst.) C.Presl, Hymenophyllaceae 13 (1843)
Lectotype (selected by Nicolson & Fosberg 2004): no locality, Forster, UPS-T 25164 (n.v.)
Etymology:
From the Greek nephro- (kidney-shaped), -phyllus (-leaved), a reference to the shape of the frond.
Vernacular Name(s):
kidney fern; konehu; kopakopa; raurenga
 Description
Terrestrial, rupestral or low epiphytic ferns. Rhizomes long-creeping, 0.5–1 mm diameter; rhizome hairs red-brown, dense at bases of stipes, scattered elsewhere, up to 2 mm long. Fronds 40–280 mm long. Stipes 20–240 mm long, reddish brown throughout, narrowly winged distally for more than half their length, brittle, glabrous or with a few short scattered hairs. Laminae undivided, reniform or almost orbicular, fertile 17–65 mm long, 25–105 mm wide, sterile sometimes a little larger and more irregular in outline, shiny green, herbaceous, two or more cells thick, glabrous; margins entire, thickened to form a distinct border. Rachises absent. Primary pinnae absent. Ultimate segments absent. Sori borne around lamina margin, many on each lamina, crowded, partially to deeply immersed in lamina; indusia urceolate, 1–2 mm long, not widened at mouth, margins entire; receptacles exserted up to 4 mm.
 Recognition
Hymenophyllum nephrophyllum is immediately recognised by its undivided, kidney-shaped lamina bearing numerous sori around the margin. The urceolate indusia and slightly exserted receptacles are unusual in Hymenophyllum, and account for the fact that the species has previously been included in Trichomanes (Allan 1961; Brownsey et al. 1985; Brownsey & Smith-Dodsworth 2000) or the segregate genus Cardiomanes (Crookes 1963). It is now treated in the monotypic subgenus Cardiomanes (Ebihara et al. 2006).
 Distribution
North Island: Northland, Auckland, Volcanic Plateau, Gisborne, Taranaki, Southern North Island.
South Island: Western Nelson, Sounds-Nelson, Westland, Southland, Fiordland.
Chatham Islands, Stewart Island.

Altitudinal range: 10–780 m.

Hymenophyllum nephrophyllum occurs throughout the North Island in lowland and montane forest, but is absent from much of the east coast. It ranges from sea level to about 750 m near Lake Waikaremoana, on Mt Taranaki and in the Tararua Ranges, reaching 780 m in the western Raukūmara district. In the South Island it extends from the Marlborough Sounds through north-west Nelson, Westland and Fiordland to southern Southland. It grows from sea level up to 600 m in the Nelson Lakes District.
 Habitat
Hymenophyllum nephrophyllum forms extensive mats on the forest floor, on fallen trunks, on banks and rocks, on lava fields, in moss forest, at the base of tree trunks and as a low epiphyte in kauri, podocarp, broadleaved and beech forest, and in old kānuka scrub.
 Biostatus
Indigenous (Endemic)
 Cytology
n = 36 (Brownlie 1958).
 Notes
Hymenophyllum nephrophyllum is a nomen novum for Cardiomanes reniforme, required because the name Hymenophyllum reniforme is pre-occupied (Ebihara et al. 2010).

Hymenophyllum nephrophyllum, together with H. dilatatum and H. scabrum, is unusual in the genus in having a frond that is more than one cell thick. Holloway (1923) showed that sporelings had a lamina only one cell thick and that the multi-layered condition developed with maturity.
 Bibliography
Brownlie, G. 1958: Chromosome numbers in New Zealand ferns. Transactions of the Royal Society of New Zealand 85: 213–216. [as Cardiomanes reniforme (G.Forst.) C.Presl]
Brownsey, P.J.; Given, D.R.; Lovis, J.D. 1985: A revised classification of New Zealand pteridophytes with a synonymic checklist of species. New Zealand Journal of Botany 23(3): 431–489.
Brownsey, P.J.; Perrie, L.R. 2016: Hymenophyllaceae. In: Breitwieser, I; Heenan, P.B.; Wilton, A.D. Flora of New Zealand — Ferns and Lycophytes. Fascicle 16. Manaaki Whenua Press, Lincoln.
Brownsey, P.J.; Smith-Dodsworth, J.C. 2000: New Zealand ferns and allied plants. Edition 2. David Bateman, Auckland. [as Cardiomanes reniforme (G.Forst.) C.Presl; Trichomanes reniforme G.Forst.]
Crookes, M.W. 1963: New Zealand Ferns, ed. 6. Incorporating illustrations and original work by H.B. Dobbie. Whitcombe & Tombs, Christchurch.
de Lange, P.J.; Rolfe, J.R.; Barkla J.W.; Courtney, S.P.; Champion, P.D.; Perrie, L.R.; Beadel, S.N.; Ford, K.A.; Breitwieser, I.; Schönberger, I.; Hindmarsh-Walls, R.; Heenan, P.B.; Ladley, K. 2018: Conservation status of New Zealand indigenous vascular plants, 2017. New Zealand Threat Classification Series No. 22. [Not Threatened]
de Lange, P.J.; Rolfe, J.R.; Champion, P.D.; Courtney, S.P.; Heenan, P.B.; Barkla, J.W.; Cameron, E.K.; Norton, D.A.; Hitchmough, R.A. 2013: Conservation status of New Zealand indigenous vascular plants, 2012. New Zealand Threat Classification Series 3. Department of Conservation, Wellington. [as Cardiomanes reniforme (G.Forst.) C.Presl] [Not Threatened]
Ebihara, A.; Dubuisson, J.-Y.; Iwatsuki, K.; Hennequin, S.; Ito, M. 2006: A taxonomic revision of Hymenophyllaceae. Blumea 51: 221–280.
Ebihara, A.; Nitta, J.H.; Iwatsuki, K. 2010: The Hymenophyllaceae of the Pacific area. 2. Hymenophyllum (excluding subgen. Hymenophyllum). Bulletin of the National Science Museum, series B (Botany) 36: 43–59.
Forster, J.G.A. 1786: Florulae Insularum Australium Prodromus. Dietrich, Göttingen.
Holloway, J.E. 1923: Studies in the New Zealand Hymenophyllaceae. Part 1. Transactions and Proceedings of the New Zealand Institute 54: 577–618.
Nicolson, D.H.; Fosberg, F.R. 2003: The Forsters and the Botany of the Second Cook Expedition (1772–1775). Regnum Vegetabile 139: 1–760.
Presl, C.B. 1843: Hymenophyllaceae. Haase, Prague.
Pryer, K.M.; Smith, A.R.; Hunt, J.S. & Dubuisson, J-Y. 2001: rbcL data reveal two monophyletic groups of filmy ferns (Filicopsida: Hymenophyllaceae). American Journal of Botany 88: 1118–1130.