Macrothelypteris torresiana (Gaudich.) Ching

Rhizomes short-creeping to erect, 3–5 mm diameter, scaly. Rhizome scales narrowly ovate, 6–10 mm long, 0.5–1 mm wide, pale to dark brown, with numerous marginal and superficial hairs. Fronds 235–1200 mm long, rarely up to 2000 mm, arching upwards. Stipes 90–750 mm long, glaucous when fresh, yellow-brown when dry, swollen and with scales and hairs near base especially when young, slightly rough proximally but smooth and glabrous distally. Laminae deeply 2-pinnate-pinnatifid to 3-pinnate-pinnatifid, ovate, gradually tapering to the apex, 145–1000 mm long, 95–700 mm wide, light green on both surfaces, herbaceous. Scales virtually absent; colourless, acicular hairs up to 0.6 mm long on adaxial costa surfaces, and multicellular hairs up to 2 mm long on the abaxial costae and vein surfaces; short-stalked glands up to c. 0.1 mm long on all lamina surfaces. Primary pinnae in 15–25 pairs, widely spaced especially proximally, narrowly ovate to ovate; the longest near the base, short-stalked, 60–450 mm long, 25–200 mm wide, reducing gradually in length to the apex; the basal pair often not much reduced in length. Secondary pinnae narrowly ovate, 16–120 mm long, 5–40 mm wide, midribs narrowly winged, apices acuminate, bases decurrent. Tertiary pinnae (when present) oblong, 8–24 mm long, 1–6 mm wide, apices obtuse, margins serrate to divided more than halfway to midrib, bases decurrent forming a wing on the secondary pinna midribs. Veins all free, branching in ultimate pinna segments, not reaching the margins. Sori round, on veins of ultimate segments, away from pinna margins; indusia reniform, 0.2–0.4 mm diameter, bearing capitate hairs or almost glabrous.

Macrothelypteris torresiana is recognised by its large fronds, glaucous stipes, 2-pinnate-pinnatifid or more divided laminae, free veins, indumentum of long multicellular acicular hairs on the abaxial surfaces and much shorter glands, absence of scales on the laminae, and tiny indusia.

Macrothelypteris torresiana has been recorded on Raoul Island from disturbed habitats and slip faces in open sunny areas, on banks, in swamps and on Macauley Island from the base of canyon walls growing with sparse Hypolepis dicksonioides. At North Cape, on Surville Cliffs, it was found on open ultramafic rock scree (de Lange & Crowcroft 1997).

2n = 124 (de Lange et al. 2004).

Names used in earlier Floras based on Cheilanthes setigera Blume (notably Nephrodium setigerum and Dryopteris setigera) are misidentifications. Macrothelypteris setigera is a Malesian species that has been much confused with M. torresiana (Holttum 1977).

It was reported by de Lange & Crowcroft (1997) that occasional cultivated specimens of M. torresiana have set viable spores, and given rise to sporelings in the vicinity of the adult plants (e.g. the experimental glasshouses at the University of Auckland, AK 231884, 231951). This location is a long way south of the southernmost known wild population at Surville Cliffs. However, de Lange & Crowcroft noted that such occurrences are uncommon and that few sporelings survive, even in the mild Auckland winters. Further north, however, M. torresiana self-sows outside and can withstand winters in Kerikeri; iNaturalist observation #67228856 shows a plant that has grown in an old compost heap for several years. Source material was not from New Zealand and was grown in a commercial fern nursery.