Plants small to medium. Stems simple to fastigately branched, red to red-brown, to c. 6 mm long. Leaves triangular or linear-lanceolate, acuminate, 0.73–1.90 mm long, 0.15–0.37 mm wide; margin recurved and denticulate above; costa well-defined, excurrent to long-excurrent, toothed dorsally by projecting cell ends, occupying c. one-third of the leaf base (rarely half), without multistratose costal wings (rarely with small wings blurring costa edges); laminal cells rectangular, 26–44 × 6–10 µm, prorate; lower cells more elongate.

Perigonia most commonly just below perichaetia. Perichaetia in branch axils; leaves similar to those on the stem. Setae 9–20 mm long. Capsules erect to inclined or, rarely, pendulous, globose to ovoid, sulcate. Peristome single; exostome teeth red, long-triangular-lanceolate, trabeculate, smooth, joined at the apices. Spores globose, reniform or ovoid, c. 58 µm diameter.

Conostomum pusillum and C. pentastichum are readily separated. The leaves of the latter are distinctly 5-ranked, especially lower on the stem, and the poorly defined costa is comparatively broad. In contrast, the leaves of C. pusillum are not as obviously 5-ranked due to slight twisting of the leaves around the stem, and the costa is well-defined, narrower and scarcely winged. Sterile specimens of C. pusillum can be difficult to distinguish from Philonotis tenuis which differs in the occasional presence of subquadrate outer basal cells, papillose rhizoids, and the absence of 5-ranked leaves.

n = 8 [Blackheath, N.S.W., Ramsay 56/64 (SYD)].

Native.

This species grows on soil in alpine or subalpine regions of New South Wales, Australian Capital Territory, Victoria and Tasmania; also in New Zealand.

Conostomum pusillum Hook.f. & Wilson, in J.D.Hooker, Fl. Nov.-Zel. 2: 88 (‘1855’) [1854] var. pusillum;  Bartramia pusilla (Hook.f. & Wilson) Mitt., Hooker’s J. Bot. & Kew Gard. Misc. 8: 260 (1856), nom. illeg.; Philonotis pusilla (Hook.f. & Wilson) Mitt., J. Proc. Linn. Soc., Bot. 4: 81 (1860).
Type: Top of the Ruahine Mountains, [New Zealand], W.Colenso 2746; holo: BM n.v., fide A.J.Fife, New Zealand J. Bot. 36: 611 (1998).

Taxonomic synonym

Conostomum parvulum Hampe, Linnaea 28: 207 (1856).
Type: In rupibus montium Grampians et in monte Cobboras, 6000’, [Vic.], coll. unknown; holo: BM n.v., fide A.J.Fife, op. cit. 613 (1998).

Misapplication

[Conostomum giganteum auct. non E.B.Bartram & Dixon: J.-P.Frahm et al., Trop. Bryol. 12: 100 (1996)]

N.S.W.: Charlotte Pass, Mount Kosciuszko Natl Park, D.H.Vitt 26783 (CANB).

A.C.T.: Mt Aggie, Brindabella Range, D.Verdon 1020 (CANB).

Vic.: Dargo High Plains Rd, 6 km SW of Mt Hotham, H.Streimann 57340 [Musci Australas. Exsicc. 531] (CANB).

Tas.: Lake Dobson, D.McVean 267113 (CANB).

A.J.Fife, New Zealand J. Bot. 612, fig. 5g–k (1998); D.Meagher & B.Fuhrer, Field Guide to the Mosses and Allied Plants of Southern Australia 109 (2003).

Gilmore, S.R. (2012). Australian Mosses Online 42. Bartramiaceae. Australian Biological Resources Study, Canberra. Version 9 June 2012. http://www.anbg.gov.au/abrs/Mosses_online/42_Bartramiaceae.html

First published as: Gilmore, S.R. (2006). Bartramiaceae, in McCarthy, P.M (ed.) Flora of Australia 51: 248–270. (Australian Biological Resources Study, Canberra & CSIRO Publishing, Melbourne.)