Asplenium appendiculatum (Labill.) C.Presl

Terrestrial or rupestral ferns or very rarely a low epiphyte. Rhizomes short, erect or short-creeping, bearing scales. Rhizome scales narrowly ovate with filiform apices, 5–30 mm long, 0.5–3 mm wide, dark brown, clathrate. Fronds 40–670 mm long. Stipes 10–290 mm long, brown abaxially, green adaxially, bearing narrowly ovate scales with filiform apices. Rachises green, scaly. Laminae 1–2-pinnate-pinnatifid or rarely 3-pinnate, ovate to broadly ovate or narrowly to broadly elliptic, narrowed to a pinnatifid apex, 20–480 mm long, 15–280 mm wide, mid- to dark green on both surfaces, coriaceous or thick and fleshy, bearing scattered scales, lacking hairs. Primary pinnae in 2–25 pairs below pinnatifid apex, often overlapping; proximal pinnae and those at mid-lamina narrowly ovate or ovate or narrowly oblong; the longest at or below the middle, 5–215 mm long, 4–58 mm wide, apices obtuse or acute or acuminate, bases stalked; costae of primary pinnae winged in distal half. Secondary pinnae gradually decreasing in length along each primary pinna to the distal end, or all more or less equal in length and decreasing only at the distal end; the longest proximal secondary pinnae narrowly ovate to ovate or elliptic or obovate, 4–65 mm long (very rarely up to 100 mm long), 2–13 mm wide, apices acute or obtuse, sometimes partly or deeply divided into tertiary segments, bases stalked or sessile; the distal secondary pinnae narrowly oblong, straight or falcate, 2–12 mm long, 1–2.5 mm wide, apices acute or acuminate, bases adnate. Sori submarginal; indusia 2–8 mm long, straight; free margins of indusia entire. Mean spore size 43–51 μm long, 29–34 μm wide; perispores prominently winged and ridged.

Asplenium appendiculatum almost always grows terrestrially and is characterised by fronds that are usually 2-pinnate-pinnatifid, somewhat coriaceous, and have the secondary pinnae decreasing gradually in size along the primary pinna to the distal end. The species is morphologically similar to A. gracillimum but has more coriaceous fronds, never produces bulbils, has primary pinnae with longer acuminate apices, and generally has longer indusia (2–8 mm long cf. 2–4 mm long).

Asplenium appendiculatum is sometimes confused with A. flaccidum subsp. flaccidum but can be distinguished in New Zealand by its terrestrial habit and upright, more divided fronds, unlike A. flaccidum subsp. flaccidum, which is usually epiphytic with pendulous, 1-pinnate-pinnatifid fronds. The latter is also tetraploid, rather than octoploid, with smaller and less prominently ridged spores.

Asplenium appendiculatum can be difficult to separate morphologically from A. flaccidum subsp. haurakiense, although their distributions barely overlap. In A. appendiculatum the secondary pinnae decrease gradually in size from the proximal to distal end of each primary pinna, whereas A. flaccidum subsp. haurakiense usually has an enlarged basal acroscopic secondary segment, which is markedly larger than the adjacent segment.

Asplenium appendiculatum has two distinct forms, which were recognised as separate subspecies by Brownsey (1977b). Subsp. appendiculatum occurs in inland forest and on rocky ground in drier parts of the southern North Island and eastern South Island; it has leathery fronds, and secondary pinnae that decrease markedly in length along the primary pinnae to the distal end. Subsp. maritimum is a coastal form that occurs from Auckland to Banks Peninsula but is most abundant on the shores of Cook Strait; it has thick, fleshy fronds, secondary pinnae that decrease only slightly along the primary pinnae, and often a broader lamina than in subsp. appendiculatum.

A terrestrial fern that occurs either under podocarp, broadleaved, and beech forest, and in mānuka, kānuka, low scrub and tussock grassland, or in exposed coastal habitats. In inland areas it grows under forest or scrub on the forest floor, cliffs, banks, streamsides and boulders; in coastal areas it grows on exposed cliffs and rocks or under coastal scrub. It is found on greywacke, sandstone, schist, basalt, limestone, marble and ultramafic rock.

There is evidence that A. appendiculatum hybridises with A. flaccidum subsp. flaccidum, A. hookerianum, A. lyallii, A. richardii (Brownsey 1977a), A. gracillimum (Brownsey 1983), A. lepidotum (Perrie & Brownsey 2016), and A. bulbiferum (newly recorded here).

n = 144 (Brownsey 1977b).

Asplenium appendiculatum was recognised as a distinct endemic species by Brownsey (1977b), who first described it as A. terrestre, with two separate subspecies. However, it was subsequently shown (Brownsey 1998) that an earlier name, Caenopteris appendiculata Labill., had been used for the form in Australia. The species occurs in both Australia and New Zealand and should be known as Asplenium appendiculatum (Labill.) C.Presl.

Asplenium laxum was published by Brown (1810), but he included Caenopteris appendiculata in its synonymy, an earlier name published by Labillardière (1806–1807), whose specific epithet should have been used instead. Asplenium laxum is therefore a superfluous name for A. appendiculatum, although it has more often been associated with A. bulbiferum (e.g. Allan 1961). Brownsey (1998) examined Brown’s material of A. laxum in BM, K, and MEL and concluded that it was a mixed collection of A. appendiculatum, A. gracillimum, and hybrids between the two. The combination A. bulbiferum var. laxum (R.Br.) Hook.f. based on Brown’s superfluous name is illegitimate.

Analysis of low-copy nuclear DNA sequences suggests that A. appendiculatum is an allopolyploid species derived from A. flaccidum and A. hookerianum (Shepherd et al. 2008).

Following Brownsey (1977b) the two forms of Asplenium appendiculatum are treated here as subspecies, but molecular and distribution evidence (Perrie unpub.) suggests this would be worth further investigation.