Dicranoweisia Lindb. ex Milde

Plants small to medium-sized, dull, yellow- or brown-green, forming cushions on rock. Stems erect, branching by forking and innovation, in cross-section with a central strand and firm-walled cortical cells. Leaves lanceolate or subulate, crisped and often spirally twisted when dry, usually entire, strongly concave or tubulose; mid to upper laminal cells quadrate or short-rectangular, mostly with cuticular striations that extend across cell walls, sometimes smooth, firm-walled, unistratose or bistratose at margins; cells of lower leaf rectangular to linear, often ± quadrate near margins; alar cells usually well differentiated, inflated. Costa narrow, in cross-section with two stereid bands.

Autoicous (paroicous in N.Z. species). Perichaetial leaves sheathing, abruptly tapered to a stout subula in N.Z. species. Setae erect and elongate, single; capsules erect and symmetric, short-cylindric to obovoid, not strumose, smooth but becoming wrinkled with age; annulus absent; operculum long-rostrate, curved. Peristome teeth inserted below rim, undivided, often fugacious, papillose or baculate throughout (not striolate in N.Z. species). Calyptra cucullate, smooth, entire at base. Spores spherical.

A medium-sized genus distributed in temperate and colder regions of both hemispheres and mostly occurring on non-calcareous rock. Brotherus (1924) recognised 18 species. Only one species is accepted for N.Z.

The combination of strongly crisped dry leaves, erect capsules, and undivided and coarsely papillose teeth is a feature of the genus as a whole. Longitudinal cuticular thickenings of the laminal cells are characteristic of both the type and the N.Z. species.

The genus is traditionally (e.g., Brotherus 1924) placed in the Dicranaceae, but Goffinet et al.’s (2009) placement in the Rhabdoweisiaceae is followed here. Ochyra (1993; 1998, p. 122) proposed its placement (with Holodontium and Verrucidens) in a subfamily Dicranoweisioideae of the Seligeriaceae.

Bell (1976) presented a treatment of three Dicranoweisia species occurring on Signy I. in the South Orkneys, and Ochyra (1998) has considered the species occurring on King George I. These two authors presented very different taxonomic interpretations. Dicranoweisia spenceri, although accepted as a Dicranoweisia by both Sainsbury (1955, p. 120) and by Fife (1995), is here referred to Kiaeria.

Weissia crispula var. ambigua Hook.f. & Wilson, Bot. Antarct. Voy. I. (Fl. Antarct.) Part I: 127 (1845). The type specimen of this name (BM) is heterogeneous. Only a small fraction of the type is unquestionably referable to D. antarctica and this name is therefore considered a nomen dubium.

Weissia tortifolia Hook.f. & Wilson (London J. Bot. 3: 540, 1844) was described from Kerguelen. Combinations based on this name have been made in several genera, including both Dicranoweisia and Verrucidens. This species has been reported from Macquarie I. (Clifford 1953, quoted by Seppelt 2004, p. 241). Irrespective of its possible occurrence on Macquarie I., Seppelt’s suggestion that it may be conspecific with Dicranoweisia antarctica deserves further investigation. If Seppelt’s suggestion is proven correct, W. tortifolia would have nomenclatural priority.