Classification
 Nomenclature
Scientific Name:
Hymenophyllum scabrum A.Rich., Essai Fl. Nouv.-Zél., 90, t. 14, f. 1 (1832)
Synonymy:
  • Sphaerocionium scabrum (A.Rich.) C.Presl, Hymenophyllaceae 34 (1843)
  • Diploophyllum scabrum (A.Rich.) Bosch, Verslagen Meded. Afd. Natuurk. Kon. Akad. Wetensch. 11: 323 (1861)
  • Mecodium scabrum (A.Rich.) Copel., Philipp. J. Sci. 67: 24 (1938)
Holotype: Nouvelle Zélande [New Zealand], D’Urville, Herb. A. Richard, P 00623460!
  • = Sphaerocionium glanduliferum C.Presl, Epimel. Bot. 22, t. 12 (1851)
Lectotype (selected by Brownsey & Perrie 2016): N[ova] Zeelandia [New Zealand], Hügel, and Nova Zeelandia, R. Cunningham, both mounted on one sheet, Herb. Presl, PRC 455139, right-hand specimen (image!)
  • = Hymenophyllum scabrum var. hirtum Colenso, Trans. & Proc. New Zealand Inst. 13: 379 (1881)
Lectotype (selected by Brownsey & Perrie 2016): New Zealand, W. Colenso, K! (photo WELT E468/33)
Etymology:
From the Latin scabrus (with a rough surface), a reference to the scabrid stipe.
Vernacular Name(s):
rough filmy fern
 Description

Epiphytic, terrestrial or rupestral ferns. Rhizomes long-creeping, 0.5–1.0 mm diameter, bearing abundant pale brown hairs up to 1 mm long, clustered at bases of stipes. Fronds 100–780 mm long. Stipes 40–170 mm long, dark brown throughout, not winged, densely covered in bristly hairs up to 5 mm long. Laminae usually 4-pinnatifid, rarely 3- or 5-pinnatifid, ovate or elliptic, 65–630 mm long, 40–150 mm wide, olive-green, membranous, 2–4 cells thick, with scattered hairs on costae and especially at bases of indusia. Rachises narrowly winged for most of their length, dark brown, bearing bristly hairs; rachis wings planate.  Primary pinnae in 10–25 pairs, scarcely overlapping, winged throughout, narrowly ovate or ovate, adnate; distal portion of primary pinnae straight or slightly incurved acroscopically; the longest primary pinnae at or below the middle, 25–140 mm long, 14–50 mm wide. Secondary pinnae arising both acroscopically and basiscopically, scarcely overlapping, ovate to elliptic, winged throughout, adnate; the longest secondary pinnae 12–39 mm long, 6–18 mm wide. Ultimate lamina segments oblong, up to 4 mm long, 0.6–1.4 mm wide; apices obtuse or truncate; margins entire, lacking a distinct border; distal segments on primary pinnae divergent or slightly curved towards frond apex. Sori borne on acroscopic and basiscopic segments at the distal ends of the pinnae, solitary, many on each primary pinna, adnate or slightly immersed in lamina; indusia bivalvate; indusial flaps broadly elliptic or broader than long, 0.75–1.5 mm long, apices obtuse or truncate, margins minutely or irregularly toothed, bearing capitate hairs when young, outer surfaces hairy at base; receptacles included within indusial flaps.

 Recognition

Hymenophyllum scabrum is a large filmy fern easily recognised by its olive-green laminae, segments with entire margins, and long bristly hairs on the stipe and indusial flaps, with the latter being minutely toothed and often broader than long.

 Distribution

North Island: Northland, Auckland, Volcanic Plateau, Gisborne, Taranaki, Southern North Island.  

South Island: Western Nelson, Sounds-Nelson, Marlborough, Westland, Canterbury, Otago, Southland, Fiordland.

Chatham Islands, Solander Island, Stewart Island.

Altitudinal range: 0–1100 m.

Hymenophyllum scabrum occurs in lowland and montane areas of the North Island from the Mangamuka Range southwards. It ranges from sea level, reaching 1100 m on Mt Taranaki and Mt Hauhungatahi. In the South Island it occurs in lowland and montane areas of the Marlborough Sounds, north-west Nelson, Westland, Fiordland and Southland, extending to Dunedin and a few scattered localities in Marlborough and Canterbury. It reaches 925 m on Key Summit.

 Habitat

Occurs in kauri, podocarp, beech and broadleaved forest growing on the ground, on rocks, banks, rock faces, rotten logs and stumps, and as an epiphyte. It has been recorded growing on Cyathea dealbata, C. medullaris, Dicksonia fibrosa, D. squarrosa, Coriaria arborea, Fuchsia excorticata, Griselinia littoralis, Lophozonia menziesii, Prumnopitys taxifolia, Pseudowintera colorata, Schefflera digitata, and Weinmannia racemosa.

 Biostatus
Indigenous (Endemic)
 Cytology

n = 36 (Brownlie 1958).

 Notes

Hymenophyllum scabrum, together with H. dilatatum and H. nephrophyllum, 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
Bosch, R.B. van den 1861: Eerst bijdrage tot de kennis der Hymenophyllaceae. Verslagen en Mededeelingen van de Afdeeling Natuurkunde; Koninklijke Akademie van Wetenschappen 11: 300–330.
Brownlie, G. 1958: Chromosome numbers in New Zealand ferns. Transactions of the Royal Society of New Zealand 85: 213–216. [as Mecodium scabrum (A.Rich.) Copel.]
Brownsey, P.J.; Perrie, L.R. 2016: Hymenophyllaceae. In: Breitwieser, I; Heenan, P.B.; Wilton, A.D. (ed.) Flora of New Zealand — Ferns and Lycophytes. Fascicle 16. Manaaki Whenua Press, Lincoln.
Brownsey, P.J.; Perrie, L.R. 2016: Taxonomic notes on the New Zealand flora: lectotypes in the fern family Hymenophyllaceae. New Zealand Journal of Botany 54(1): 48–62.
Brownsey, P.J.; Smith-Dodsworth, J.C. 2000: New Zealand ferns and allied plants. Edition 2. David Bateman, Auckland.
Colenso, W. 1881: On some new and undescribed New Zealand ferns. Transactions and Proceedings of the New Zealand Institute 13: 376–384.
Copeland, E.B. 1938: Genera Hymenophyllacearum. Philippine Journal of Science 67: 1–110.
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. [Not Threatened]
Holloway, J.E. 1923: Studies in the New Zealand Hymenophyllaceae. Part 1. Transactions and Proceedings of the New Zealand Institute 54: 577–618.
Presl, C.B. 1843: Hymenophyllaceae. Haase, Prague.
Presl, C.B. 1851: Epimeliae botanicae. Haase, Prague.
Richard, A. 1832: Essai d'une Flore de la Nouvelle Zélande. In: Dumont d'Urville, J. Voyage de découvertes de l'Astrolabe. Botanique. Tastu, Paris.