Bryum caespiticium Hedw.

Plants yellow-green, ± lustrous, forming compact turves or tufts, comose. Stems red, to c. 8 mm, with numerous subperichaetial innovations but otherwise unbranched, beset below with brown, finely papillose rhizoids, in cross-section with 1–2 layers of firm-walled cortical cells and a distinct central strand. Leaves comose, erect-spreading when moist, moderately contorted when dry, oblong- or ovate-lanceolate, gradually tapered to a long-acuminate apex, c. 1.5–2.8 mm and with lamina 0.8–0.9 the total leaf length, concave, not plicate, ± red at base, entire or rarely finely denticulate near acumen base, bordered, narrowly recurved in lower ⅔ of leaf or nearly to apex, not decurrent; upper laminal cells rhombic-hexagonal, firm-walled, mostly 45–60 × 12–15 µm and 3–5:1, often becoming longer at base of acumen (and merging there with cells of the border), becoming longer, thinner-walled and ± porose in lower leaf; marginal cells ± linear, forming a border 3–5 rows wide at mid leaf that usually extends to the leaf apex where it merges with elongate cells of the acumen; basal cells ± oblong in a few rows, usually red, a few cells in alar angles inflated in comal leaves. Costa red at base, excurrent (usually long-excurrent) to fill acumen. Brood bodies (including tubers) absent.

Dioicous. Perichaetia on short basal shoots, overtopped by few to several subtending innovations. Perigonia terminal, the inner bracts c. 1 mm, enclosing numerous antheridia. Setae c. 15–25(–45) mm, cygneous just below capsule, red; capsules pendent, oblong-clavate, 2–3 mm long, with a poorly defined neck c. ⅓ the total length; operculum conic, apiculate, red-brown. Exostome teeth yellow, hyaline near apex, finely papillose below, baculate near apex; endostome segments fenestrate; cilia (2–)3, appendiculate. Spores 9–12(–16) µm.

Catcheside 1980, fig. 154; Crum & Anderson 1981, fig. 257 I–N; Smith 2004, fig. 184, 7–10.

The golden coloration, crowded (comose) leaves, non-decurrent leaf bases, narrower upper laminal cells, more strongly excurrent costae (to c. 0.2 the total leaf length), dioicous sexuality and generally shorter capsules distinguish between the present species and B. pseudotriquetrum, a species with which it is sometimes confused.

Confusion sometimes occurs with B. appressifolium, but that species can normally be distinguished by the non-comose arrangement of its leaves, its shorter capsules with large, bright red opercula, and its lack of secondary pigmentation at the leaf base. Bryum crassum differs by having serial comae, less excurrent costae, and strongly incrassate laminal cells, which overall give the plant a much more robust and sturdy appearance.

On bare soil, often calcareous, in either dry or moist situations. Often in tussock grasslands and on river beds; sometimes in lawns. Occurring from 200 m to at least 950 m. Ceratodon purpureus, Didymodon torquatus, Hypnum cupressiforme, and Weissia controversa, as well as Syntrichia spp. (including S. antarctica) are common associates.

The yellow colouration, comose habit, relatively long upper laminal cells, long-excurrent costae, recurved and entire margins and pigmented basal cells combine to give this weedy species a distinct facies. The elongate upper laminal cells merge with the more elongate cells of the leaf border at the base of the awn (not illustrated here) in a manner that is distinctive.

Type material of B. austrobimum is aberrant by having larger (18–21 µm) than normal spores for this species. In other respects, however, it lies near the lower end of the range of continuous variability (e.g., setae c. 15 mm long) but is not remarkable for B. caespiticium. Despite its unusually large spores, B. austrobimum is not recognised here at any taxonomic level; this conforms with the opinion given by Ochi (1970, p. 36).

Ochi annotated the lectotype of B. cylindrothecium as B. caespiticium but apparently changed his mind concerning its identity, deciding to recognise it as distinct (cf. Ochi 1984, p. 180). Bryum cylindrothecium is not recognised here.

For unclear reasons Spence & Ramsay (2006) treated B. caespiticium as a heterotypic synonym of Ptychostomum angustifolium (Brid.) J.R.Spence & H.P.Ramsay. However, the basionym of the latter name is B. angustifolium Brid. (1817), which was published many years later than B. caespiticium Hedw. Spence & Ramsay’s suggested nomenclature is not followed here.