Classification
 Nomenclature
Scientific Name:
Trichomanes humile G.Forst., Fl. Ins. Austr. 84 (1786)
Synonymy:
  • Didymoglossum humile (G.Forst.) C.Presl, Hymenophyllaceae 23 (1843)
  • Crepidomanes humile (G.Forst.) Bosch, Hymenophyll. Javan. 16, t.11 (1861)
  • Crepidopteris humilis (G.Forst.) Copel, Philipp. J. Sci. 67: 58 (1938)
  • Crepidophyllum humile (G.Forst.) Reed, Amer. Fern J. 38: 89 (1948)
  • Reediella humilis (G.Forst.) Pic.Serm., Webbia 24: 719 (1970)
Lectotype (selected by Nicolson & Fosberg 2003): no locality, Forster, “from Forster’s Herb.”, K (n.v.)
Etymology:
From the Latin humilis (low-growing), a reference to the short stature of the plant.
 Description

Epiphytic ferns. Rhizomes long-creeping, 0.2–0.3 mm diameter, bearing red-brown hairs up to 0.5 mm long. Fronds 25–35 mm long. Stipes 4–10 mm long, brown proximally, green distally, narrowly winged for at least half their length, glabrous or with short scattered hairs. Laminae 1–2-pinnatifid distally to 2–3-pinnatifid proximally, ovate or elliptic or narrowly elliptic or narrowly obovate, 22–25 mm long, 4–12 mm wide, green, membranous, glabrous or with a few short scattered clavate hairs. Rachises winged throughout, green, glabrous or with a few short scattered clavate hairs. Primary pinnae in 4–6 pairs, not overlapping, narrowly ovate to broadly ovate, winged throughout; distal primary pinnae decurrent; proximal primary pinnae almost stalked; the longest primary pinnae just above or below the middle, 4–9 mm long, 2–6 mm wide. Ultimate segments linear, entire, up to 2 mm long, 0.6–1.0 mm wide, adnate, each with a single unbranched vein; apices obtuse; margins entire with a clearly defined bistratose border of elongated cells with oblique end-walls. Sori borne on short acroscopic segments near bases of primary pinnae, one on each primary pinna, immersed in lamina with a wing 1–2 cells wide at mid-length; indusia tubular, 1.5–2.5 mm long, widened at mouth; sporangia borne on a fine receptacle up to 1 mm long, projecting beyond the indusia at maturity.

 Recognition

Trichomanes humile is superficially similar to T. endlicherianum and T. caudatum but can be distinguished by its bistratose border of elongated cells, and sometimes by the absence of roots. Trichomanes caudatum has a border of shorter cells and T. endlicherianum a border of elongated cells, but neither are bistratose. Trichomanes humile is further distinguished by the wing of laminal cells either side of the sori which are only 1–2 cells wide at mid-length, whereas in T. endlicherianum they are 3 or more cells wide.

 Distribution

Kermadec Islands.

Altitudinal range: 450 m.

Trichomanes humile is a rare fern in New Zealand, at the southern extent of its distribution, known only from a single collection on Raoul Island, Kermadec Islands (AK 329225, WELT P026050).

Also Taiwan, Thailand, Malaysia, Philippines, Indonesia, Papua New Guinea, Australia (Queensland), Micronesia, Solomon Islands, New Caledonia, Vanuatu, Fiji, Samoa, Tonga, Cook Islands, Society Islands, Austral Islands.

 Habitat

Occurs as an epiphyte on Cyathea milnei in dense, deeply shaded wet forest under Metrosideros kermadecensis at 450 m altitude.

 Biostatus
Indigenous (Non-endemic)

Trichomanes humile (as Crepidomanes) was given a conservation status of Naturally Uncommon by de Lange et al. (2013).

 Notes

In the classification of Ebihara et al. (2006), Trichomanes humile is treated as Crepdiomanes humile.

 Bibliography
Bosch, R.B. van den 1861: Hymenophyllaceae Javanicae. Van der Post, Amsterdam.
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.
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. [Nationally Critical]
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.
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.
Nicolson, D.H.; Fosberg, F.R. 2003: The Forsters and the Botany of the Second Cook Expedition (1772–1775). Regnum Vegetabile 139: 1–760.
Pichi Sermolli, R.E.G. 1970: Fragmenta Pteridologiae II. Webbia 24: 699–722.
Presl, C.B. 1843: Hymenophyllaceae. Haase, Prague.
Reed, C.F. 1948: Two new generic names of ferns. American Fern Journal 38(3): 87–89.
Smith, A.R.; Pryer, K.M.; Schuettpelz, E.; Korall, P.; Schneider, H.; Wolf, P.G. 2006: A classification for extant ferns. Taxon 55(3): 705–731.