Synoicous. Plants in loose tufts or mats, 10–30 mm tall, green to yellowish green above, red-brown or brown below. Stems branched. Rhizoids extending up stems. Leaves crisped, flexuose and loosely curled around stem when dry, spreading or somewhat recurved when moist, lanceolate or linear-lanceolate, 1.4–2.4 mm long, 0.5–1.2 mm wide; apex sharply acute; base slightly decurrent; margin ±undulate, often dentate, with teeth formed by whole cells; costa ending below apex or, rarely, percurrent and broadened at apex; upper laminal cells irregularly arranged, isodiametric, 6.0–12.5 × 4.5–11.0 µm, thick-walled, with 3–6 short papillae per cell. Gemmae rare, small, clavate, 3-celled, green with hyaline walls.

Perichaetial leaves ovate-lanceolate, with acuminate apices. Calyptra smooth. Setae 10–15 mm long. Capsules oblong or cylindrical, 1.5–2.0 mm long, with 8 deep ribs along entire length when dry. Peristome single; exostome absent; endostome segments 8, rarely 16, filiform, smooth, hyaline. Spores 20–25 µm diameter, papillose.

This species can be separated from Zygodon intermedius by the more open habit, the more twisted and undulate leaves and longer setae, synoicous rather than dioicous reproduction, larger spores, longer capsules and differences in the perichaetial leaves. The two species also differ in their ecology and distribution; Z. hookeri occurs in wetter habitats and is endemic to Australasia, whereas Z. intermedius tolerates a wider ecological amplitude and is more widespread.

Chromosome number not known.

Native.

Extends to New Zealand. In Australia local in southern New South Wales, southern and southwestern Victoria and Tasmania.

Occurs at elevations of 400–1000 m, most commonly as an epiphyte (often on trunks of Nothofagus in wetter areas) and occasionally on rocks.

Zygodon hookeri Hampe, Linnaea 30: 632 (1860). Type: Grampians, [Vic.], 1854, F.Mueller; holo: BM.

Misapplied names

Zygodon reinwardtii auct. non Schwägr.: L. Rodway, Pap. & Proc. Roy. Soc. Tasmania 1913: 58 (1914).

Zygodon anomalus auct. non Dozy & Molk.: L. Rodway, Pap. & Proc. Roy. Soc. Tasmania 1913: 58 (1914).

N.S.W.: Deep Creekk, Batlow, W.W. Watts 7631 (NSW).

Vic.: Mount William, Grampians, H. Streimann 3031 (CANB).

Tas.: Mount Wellington, W.A. Weymouth 3049 (HO); Forth River, L. Rodway 2492 (HO); Great Lake, D.H. Norris 33028 (HO).

J. Lewinsky, Lindbergia 15: 116, figs 31–33; 134, figs 156–175 (1989).

H.P. Ramsay, D.H. Vitt & J. Lewinsky-Haapasaari (2012), Australian Mosses Online 47. Orthotrichaceae. Australian Biological Resources Study, Canberra. Version16 June 2012. 

First published as: J. Lewinsky-Haapasaari & H.P. Ramsay(2006), Orthotrichaceae: Zygodon, Fl. Australia 51: 237–244. Australian Biological Resources Study, Canberra & CSIRO Publishing, Melbourne.