Fairly common or occasional in coastal rock crevices and in forest at low altitudes.
N.Is.: Duncombe Bay, M.Lazarides 8063 (CANB, K, NSW); along Rooty Hill Rd, R.D.Hoogland 11298 (CANB, K); point S of Emily Bay, P.S.Green 1878 (K); Cascade, A.Cunningham 28 (K); Philip Is., R.M.Laing (CHR).
Hybrids with A. dimorphum Kunze occur on Norfolk Is.
T: Lord Howe Island, P.S.Green 2334; holo: K. So named in reference to the substitute or surrogate role for A. pteridoides which this species has played.
?Asplenium obtusatum var. incisum Benth., Fl. Austral. 7: 747 (1878); ?A. lucidum var. incisum (Benth.) Hook. ex Bonap., Notes Pteridologiques 5: 123 (1917).T: Lord Howe Island, J.P.Fullagar; holo: ?MEL n.v.
[Asplenium pteridoides auct. non Baker: J.G.Baker in W.J.Hooker, Icon. Pl. 17: t. 1649/1, 2, 4 (1886), et auct. mult.]
Illustrations: J.G.Baker in W.J.Hooker, Icon. Pl. 17: t. 1649, figs. 1, 2, 4 (1886); C.J.Goudey, Austral. Fern J. 1:  (1984).
Terrestrial or epiphytic fern. Caudex short, distinct; scales narrow, to 3 cm long, clathrate, hair-tipped. Fronds pinnate–bipinnatifid; stipe 15–30 cm long, with occasional long, narrow scales and dense brown, appressed 'scurfy' scales 0.5–2 mm long, easily rubbed off; lamina 30–55 cm long, 15–30 cm broad, with very small, scattered, irregularly-shaped scales beneath; pinnae long-acute, the longest 6–16 cm long, 1–2 cm broad, deeply and regularly divided, apices of lobes 3–4 mm apart; segments narrow, 2–3 mm wide with 2 or 3 apical teeth. Sori oblong-linear to elongate oblong-lanceolate, 3–7 mm long, on upper edges of segments only.
Lord Howe Is. Endemic.
Occurs in forest at high altitudes, rare at lower elevations.
L.H.Is.: Mt Gower, J.P.Fullagar 16 (MEL); loc. id., P.S.Green 1606 (A, K); loc. id., P.S.Green 2334 (K); Erskine Valley, M.Percival 11 (BRI); side of Mt Lidgbird, W.G.Milne 24 (MEL); track to North Bay, A.C.Beauglehole 5384 (MEL).
Shortly after A. pteridoides was described by J.G.Baker he published a drawing (W.J.Hooker, Icon. Pl. 17: t. 1649, 1886) in which, without realising, he included this species as well – and as the most prominent part of the plate. Many subsequent authors have consequently misidentified this, the commoner of the two species, as Baker's A. pteridoides. A hybrid with A. milnei has been recorded.
Terrestrial or epiphytic fern. Rhizome stout, shortly creeping; scales dense, narrow, clathrate. Fronds pinnate; stipe 10–20 (–30) cm long; rachis with narrow, brown scales when young, usually shed early; lamina 25–90 cm long, 10–20 cm broad, discolourous; pinnae 15–25 per side, lanceolate to very narrowly lanceolate, widest towards base, 5–12 cm long, 0.5–2 cm broad, doubly serrate with margins variously cut, at an acute angle to costae, apices of lobes c. 10 mm apart, long-acute. Sori linear, often almost parallel to or at a very acute angle to midrib, to 1.5 cm long; indusia attached on alternate sides of adjacent sori.
Sicklefern, Sickle Asplenium.
Norfolk Is., Lord Howe Is. Quite common in the National Park on Norfolk Is., only occasional on Lord Howe Is. Also known from Madagascar, through tropical Asia to Malesia, Australia, New Zealand and Polynesia.
N.Is.: King Fern Gully, R.D.Hoogland 11194 (CANB, K); s. loc., 1902, J.H.Maiden & J.L.Boorman (K, NSW); s. loc., A.Cunningham 52 (K). L.H.Is.: E side of North Hummock, A.C.Beauglehole 5386 (CANB, MEL); E edge of Intermediate Hill, J.C.Game 69/292 (K); atop Mt Gower, A.C.Beauglehole 5962 (CANB).
P.J.Brownsey, in his revision of the New Zealand species (New Zealand J. Bot. 15: 47, 1977), commented that the narrow-leaved variant from the Kermadec Is. closely resembles the plants from Lord Howe Is. and Norfolk Is. A hybrid with the Lord Howe Is. endemic, A. milnei, has been recorded.
pteridoidesBaker J. Bot. 11: 17(1873)
Hooker's Icon. Pl. 17: t.1649/3(1886) p.p.
T: Lord Howe Island, 1871, Eclipse Expedition, [C.Moore 19]; holo: K. Named from a resemblance to ferns of the genus Pteris.
Asplenium bulbiferum var. howeanum Watts, Proc. Linn. Soc. New South Wales 37: 399 (1913); A. howeanum (Watts) W.R.B.Oliv., Trans. & Proc. New Zealand Inst. 49: 122 (1917).T: Dinner Run, Lord Howe Island, W.W.Watts; lecto: NSW, fide P.S.Green, Kew Bull. 43: 650 (1988).
Illustration: J.G.Baker in W.J.Hooker, Icon. Pl. 17: t. 1649, fig. 3 (1886).
Terrestrial fern. Rhizome decumbent(?); scales very narrowly triangular, 4–6 mm long. Fronds tripinnatifid; stipe 9–10 cm long, naked except for the base with scales like those on rhizome; rachis narrowly winged in upper half; lamina 12–23 cm long, 7–15 cm broad, glabrous; pinnae 6–9 per side, lanceolate-deltoid in outline, the largest 5–9 cm long, 1.5–4 cm broad, divided to the narrowly winged costae; pinnules cuneate-rhomboid, 1–2.5 cm long, lower half entire. Sori linear, 2–3 mm long, confined to outermost edges of pinnules.
Lord Howe Is. Endemic. This has been little collected and, confined to the southern mountainous areas, is perhaps rare or local in its occurrence.
L.H.Is.: Mt Gower, C.Moore 19 (K); loc. id., 1920, J.L.Boorman (K, NSW); loc. id., J.P.Fullagar (K); SE side of Mt Lidgbird, A.C.Beauglehole 5387 (MEL); s. loc., J.P.Fullagar (MEL).
Generally confused with the more common fern now called A. surrogatum.
dimorphumKunze Linnaea 23: 233(1850)
Based on Asplenium diversifolium A.Cunn. ex Endl., Prodr. Fl. Norfolk. 10 (1833), nom. illeg. non Blume (1828).T: Norfolk Island, F.L.Bauer & loc. id., A.Cunningham; syn: W; isosyn: K. So named from the Greek dis (twice) and morphe (shape), in reference to the different types of frond in this fern.
Darea heterophylla Sm. in A.Rees, Cycl. 11: No. 2 (1808), non Asplenium heterophyllum C.Presl (1825).T: 'New South Wales' [Norfolk Island], comm. R.Molesworth; holo: LINN; IDC microfiche 5074.1629/6.
Terrestrial fern. Rhizome short; scales c. 1 cm long, clathrate. Fronds bipinnate and tripinnate; stipe 30–40 cm long, covered with short, appressed, and long, narrow, scattered, clathrate scales, easily rubbed off; upper half of rachis not winged; lamina 30–60 cm long, 25–40 cm broad, with small, scattered, clathrate scales below or glabrescent; pinnae 8–10 per side, lanceolate-deltoid in outline, the longest 12–20 cm long, 3–8 cm broad, markedly dimorphic; sterile pinnules deltoid, 10–20 mm broad, bipinnatisect or sometimes bipinnate, serrate, acute, with base somewhat asymmetrical; fertile pinnules linear, 3–15 mm long, 1–2 mm broad, tripinnate; sterile and fertile fronds separate or sometimes both types of pinnae on same frond, the sterile in the lower part. Sori linear, 4–12 mm long, marginal.