The description of T. australasiaeis presented here as representative of the genus.
Plants blackish green, white below, tufted or in turves. Stems 3–10 mm, branched from below perichaetia and perigonia, in cross-section with a central strand, sclerodermis absent. Leaves erect-spreading from a loosely sheathing base with distal part often ± erect when moist, loosely curled individually and often around the stem when dry, 1.5–2.5 mm, narrowly linear-lanceolate, carinate, acute to acuminate; margins variably recurved, becoming bistratose distally, papillose; upper laminal cells somewhat obscure, irregularly quadrate, rounded or oblate, firm-walled, superficially ± flat, with 2–4 low, simple, often inconspicuous papillae, 8–13 × 9–12 µm, becoming longer towards the leaf base; lower laminal cells conspicuously differentiated, lax and thin-walled, hyaline, smooth, rectangular, becoming narrower and firmer towards the leaf margins. Costa reddish brown, stout below, narrower above and sunken in a groove, failing before the apex or percurrent; adaxial superficial cells similar to adjacent laminal cells except in extreme leaf base; abaxial superficial cells quadrate distally. Brood bodies not seen. Axillary hairs of 4–8 cells, of which the basal cell is shorter and brown. Laminal KOH colour reaction negative, or pale yellow, sometimes with red patches.
Dioicous. Perichaetia terminal, with perichaetial leaves erect, loosely sheathing the seta base, longer than vegetative leaves, with basal zone of smooth, hyaline, lax cells extending >½ leaf length. Perigonia terminal, often overtopped by an innovation, bulbiform, on equal-sized plant. Setae slender, reddish orange, 4–11 mm. Capsules erect, symmetric, cylindric or narrowly ellipsoid, brown to reddish brown, darker at the mouth, 1–1.5 mm. Operculum rostrate with a slightly curved oblique beak, from ½ to equal the theca length, with cells arranged obliquely in the base only. Peristome orange-brown, c. 200–400 µm (as retained on theca after capsule dehiscence, but with additional fragments remaining within the operculum), comprising 16 ± erect teeth (incurved when dry), inserted on a low basal cylinder and divided, sometimes irregularly, into two finely and densely spiculose rami. Calyptra cucullate.Spores 11–17 mm, smooth.
The genus was described by Cardot (1909) to accommodate the new species Trichostomopsis crispifolia from Mexico, and its systematic position has been controversial since then (Jiménez et al. 2005). Only two species are currently recognised in the genus, both being widespread in temperate regions of the world. In a N.Z. context the sole representative of the genus has been variously recognised in Barbula Hedw. (Dixon 1923; Sainsbury 1955), in Didymodon Hedw. (Fife 1995; Zander 1993), and in Trichostomopsis Cardot (Scott & Stone 1976; Catcheside 1980; Beever et al. 1992; Allan Herbarium 2023).
The description of T. australasiae is presented here as representative of the genus.
| Category | Number |
|---|---|
| Indigenous (Non-endemic) | 1 |
| Total | 1 |
