Dioicous. Plants medium-sized to robust, pale green to yellow-green. Stems to 5 cm long, sparingly branched from the base; branches often erect. Stems and branches complanate, densely foliate, variously weakly wrinkled when dry, straight when moist. Leaves distichous, imbricate, spathulate, 1.8–3.2 mm long, 0.8–1.7 mm wide; apex rounded; base narrow; margin entire to regularly crenate above, distantly at the base; costa prominent, occupying more than three-quarters of the leaf length, 2 or 3 cells wide, 40–60 μm wide at the base. Laminal cells moderately thick-walled; upper cells irregularly quadrate, rounded or hexagonal to shortly irregularly rectangular, to 15–27 × 14–16 μm, slightly smaller and quadrate at the margin; median cells similar, obliquely angled, to 30 × 16 μm; juxtacostal cells larger; basal juxtacostal cells thin-walled, rectangular to hexagonal, to 90 × 30 μm, nearer the margin to 30 × 10 μm, shorter along the margin; border absent. Rhizoids moderately dense on lower stems, short-branched, papillose, to 10 mm long, to 15 μm wide; cells opaque, 180–220 μm long.

Perigonia axillary, elongate. Perigonial leaves oblong-lanceolate, c. 1.25 mm long and 0.55 mm wide, ecostate; margin weakly and distantly toothed. Laminal cells rhomboidal, c. 75 × 25 μm; basal cells more rectangular. Antheridia c. 10 per perigonium, 450–500 × 45–50 μm; paraphyses hyaline, sparse, c. 0.7 mm long and 10 μm wide. Perichaetia ovate. Perichaetial leaves broadly elliptical, c. 1.3 mm long and 0.8 mm wide, ecostate, acute to obtuse; base broad; margin entire. Laminal cells elongate-hexagonal, c. 62 × 15 μm; marginal cells rectangular, narrower, not forming a border. Calyptra 1.0–1.2 mm long. Seta 3–10 mm long, smooth. Capsules dark purplish, inclined or erect, ovoid, 0.5–1.0 mm long; operculum to 1.2 mm long, conical, with an erect beak. Peristome: rxostome teeth yellowish brown, c. 400 μm tall, c. 70 μm wide at the base; endostome segments clear, smooth. Spores opaque, 10–12 μm diameter.

The large, hyaline mid-leaf cells are quite prominent and give the leaves a whitish appearance.

The main period of capsule formation is August–January, with a lull in December.

Hypnum microcarpon Hedw., Species Muscorum Frondosorum 244 (1801); Pterygophyllum microcarpum (Hedw.) Brid., Muscologiae Recentiorum Supplementum  4: 149 (1819); Hookeria microcarpa (Hedw.) Hook. & Grev., Edinburgh Journal of Science  2: 226 (1825); Mniadelphus microcarpus (Hedw.) Müll.Hal., Linnaea 21: 196 (1848); Distichophyllum microcarpum (Hedw.) Mitt., Transactions and Proceedings of the Royal Society of Victoria 19: 77 (1882). 
Type: “Insulae Australis”; holo: G, n.v.

Taxonomic synonyms

Hookeria complanata Hampe, Linnaea 40: 320 (1876); Pterygophyllum complanatum (Hampe) A.Jaeger, Bericht über die Thatigkeit der St. Gallischen Naturwissenschaftlichen Gesellschaft 1875–76: 342 (1877) [Ad. 2: 246]. T: ‘Johanne River’ [Johnson R.], Qld; holo: BM; iso: MEL.

Hookeria subrotunda Hampe, Linnaea 40: 320 (1876); Pterygophyllum subrotundum (Hampe) A.Jaeger, Bericht über die Thatigkeit der St. Gallischen Naturwissenschaftlichen Gesellschaft 1875–76: 342 (1877) [Ad. 2: 246]; Mniadelphus subrotundus (Hampe) Müll.Hal. ex M.Fleisch., Hedwigia 63: 214 (1922). T: Mount Dissaipointement [Disappointment, Vic.]; holo: BM; iso: MEL.

Pterygophyllum levieri Geh., Revue Bryologique 8: 26 (1881); Distichophyllum levieri (Geh.) Broth., in H.G.A.Engler & K.A.E.Prantl, Naturlichen Pflanzenfamilien I, 3: 930 (1907). T: Mt Wellington, Tas.; n.v.

S.A.: Hindmarsh Valley Falls, D.G.Catcheside 53.273 (AD, MEL). Qld: Lamington Natl Park, I.G.Stone 4220, 4229 (MELU).

N.S.W.: Erlington Ck, Tallaganda S.F., 17 km WSW of Braidwood, H.Streimann 37835 (B, CANB, NY); Stoney Ck, H.Streimann 45230 (CANB, NY).

A.C.T.: Tidbinbilla Nature Reserve, H.Streimann 9275 (CANB, L).

Vic.: near Point Hicks, H.Streimann 39654 (CANB, CHR, NY).

Tas.: ‘German Town’, 5 km NNE of St Marys, J.A.Curnow 2461 (CANB).

J.Beever, K.W.Allison, J.Child, Mosses of New Zealand, 2nd edn 131 (1992); H.Streimann, Journal of the Hattori Botanical Laboratory 86: 102, fig. 7 (1999).

Streimann, H. (2012). Australian Mosses Online 11. Hookeriaceae: [Distichophyllum]. Australian Biological Resources Study, Canberra. Version 19 April 2012