Classification
 Nomenclature
Scientific Name:
Hymenophyllum lyallii Hook.f., Bot. Antarct. Voy. II (Fl. Nov.-Zel.) Part II, 16 (1854)
Synonymy:
  • Trichomanes lyallii (Hook.f.) Hook. ex Hook. & Baker, Syn. Fil. [Hooker & Baker] 77 (1867)
  • Sphaerocionium lyallii (Hook.f.) Copel., Philipp. J. Sci. 67: 33 (1938)
Lectotype (selected by Brownsey & Perrie 2016): New Zealand, Thomson’s Sound, SW coast, Middle Island, D.Lyall, March 1851, Herbarium Hookerianum, K, labelled only “H. lyallii”! (photo WELT E469/22)
Etymology:
Named in honour of David Lyall (1817–1895), a Scottish botanist who visited New Zealand in HMS Terror as part of Ross’s Antarctic Voyage (1839–1843).
 Description

Usually epiphytic ferns, rarely terrestrial or rupestral. Rhizomes long-creeping, 0.1–0.2 mm diameter, bearing unbranched pale brown hairs up to 1.5 mm long, clustered at bases of stipes, more evenly distributed elsewhere. Fronds 9–90 mm long. Stipes 4–70 mm long, dark brown, not winged, bearing long brown bifurcate hairs. Laminae 2–4-pinnatifid or branching pseudodichotomously 2–4 times, ovate or flabellate or almost orbicular, 4–40 mm long, 6–34 mm wide, pale green, membranous, with marginal teeth bearing long bifurcate hairs, and sparse bifurcate hairs on costae. Rachises winged, dark brown, bearing sparse bifurcate hairs. Primary pinnae in 2–5 pairs, not overlapping, winged throughout, obovate or flabellate, all adnate; distal portion of primary pinnae straight; the longest primary pinnae at the base, 6–21 mm long, 3–13 mm wide. Secondary pinnae arising basiscopically or both basiscopically and acroscopically, not overlapping, obovate, winged throughout, adnate; the longest secondary pinnae 2–18 mm long, 2–10 mm wide. Ultimate lamina segments oblong, up to 6 mm long, 1.1–2.4 mm wide; apices obtuse or truncate or emarginate; margins with minute teeth, lacking a distinct border; distal segments on primary pinnae divergent. Sori terminating ultimate segments throughout primary pinnae, solitary, many on each primary pinna, immersed in lamina; indusia bivalvate; indusial flaps obovate or obtriangular or broader than long, 1–2 mm long, apices obtuse or truncate, margins entire, hairy on margins; receptacles included within indusial flaps.

 Recognition

Hymenophyllum lyallii is distinguished by its flabellate fronds with minute marginal teeth bearing bifurcate hairs. No other New Zealand species of filmy fern has flabellate fronds or bifurcate hairs, although stellate hairs are present in H. frankliniae and H. malingii. However, sterile fronds of H. lyallii are often confused with a group of common liverworts, including Hymenophyton flabellatum and Symphyogyna species.

 Distribution

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

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

Chatham Islands, Stewart Island, Auckland Islands.

Altitudinal range: 0–925 m.

Hymenophyllum lyallii occurs in lowland and montane areas of the North Island from Doubtless Bay to Rotorua and Mt Taranaki, with an outlying population on Mt Arawaru, Tararua Ranges. There is also an unlocalised collection in the Cheeseman Herbarium made by Colenso from the Ruahine Ranges (AK 142002). The species has only rarely been recorded below 250 m but reaches 850 m on Mt Kaitarakihi and Mt Pirongia, and 925 m on Mt Te Aroha. In the South Island, it occurs in lowland and montane areas of the west coast from Nelson to Fiordland, western Southland and Stewart Island. It ranges from sea level up to 1000 m in the Bryant Range, north-west Nelson and Mt Davy, Paparoa Range. It is known from a single collection each on the Chatham Islands (AK 305162, WELT P023356) and Auckland Islands (CHR 323171).

Also Australia (New South Wales).

 Habitat

Occurs in kauri, podocarp, beech and broadleaved forest, usually as an epiphyte or at the base of trunks, but also on old stumps, mossy banks, rock faces and under overhangs. It has been recorded growing on Cyathea dealbata, C. smithii, Dicksonia squarrosa, Dacrydium cupressinum, Lepidothamnus intermedius, Libocedrus bidwillii, Lophozonia menziesii, Metrosideros sp., Quintinia serrata and Weinmannia racemosa.

 Biostatus
Indigenous (Non-endemic)
 Cytology

n = 36 (Brownlie 1965).

 Notes

Hymenophyllum lyallii has been recorded for New Caledonia by Ebihara et al. (2004). However, DNA sequencing suggests that New Caledonian plants are not closely related to Australian and New Zealand plants and may belong to a different species (Perrie et al. 2016).

 Bibliography
Brownlie, G. 1958: Chromosome numbers in New Zealand ferns. Transactions of the Royal Society of New Zealand 85: 213–216.
Brownlie, G. 1965: Chromosome numbers in some Pacific Pteridophyta. Pacific Science 19: 493–497.
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.
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]
Ebihara, A.; Hennequin, S.; Iwatsuki, K.; Bostock, P.D.; Matsumoto, S.; Jaman, R.; Dubuisson, J.-Y.; Ito, M. 2004: Polyphyletic origin of Microtrichomanes (Prantl) Cope. (Hymenophyllaceae), with a revision of the species . Taxon 53(4): 935–948.
Hooker, J.D. 1854–1855: The Botany of the Antarctic Voyage of H.M. Discovery Ships Erebus and Terror, in the years 1839–1843, under the command of Captain Sir James Clark Ross. II. Flora Novae-Zelandiae. Part II. Flowerless plants. Lovell Reeve, London.
Hooker, W.J.; Baker, J.G. 1865–1868: Synopsis Filicum. Hardwicke, London.
Perrie, L.R.; Shepherd, L.D.; Brownsey, P.J.; Larrain, J.; Shaw, B.; Thouvenot, L.; von Konrat, M. 2016: Rediscovery and reinstatement of the New Caledonian endemic filmy fern Hymenophyllum pumilio Rosenst. New Zealand Journal of Botany 54(1): 1–10.