Streblotrichum P.Beauv.

The description of S. convolutum below is presented as representative of the genus.

Plants bright yellow-green above, brown below, forming tufts or turves, usually on soil. Stems 3–10 mm, in cross-section with a central strand, a weakly developed sclerodermis, and with the outermost walls of the surface cells thin. Leaves erect-spreading to spreading when moist, incurved, or individually twisted, and often weakly twisted around the stem when dry, 1.0–1.7 mm, oblong-lanceolate, carinate, acute, often with a conspicuous unicellular, hyaline apiculus (not illustrated); margins variably recurved in basal half, plane and often undulate above, crenulate-papillose; upper laminal cells obscure, quadrate to round-rhombic, some oblate, firm-walled, evenly thickened, pluripapillose with complex papillae, (6.0–) 9–10.5 × 7.5–9.0 µm; upper marginal cells mostly shorter in one row; lower laminal cells gradually transitioning from upper laminal cells, extending higher medially, rectangular, thick-walled, with scattered simple papillae, smooth in the extreme base, and one row shorter at the margin, forming a weak border. Costa failing 1–3 cells below the leaf apex or percurrent, sunken in a deep groove adaxially; adaxial superficial cells long-rectangular, ± smooth; abaxial superficial cells elongate and papillose in distal ⅔ of leaf. Rhizoidal tubers often present, sub-spherical to ellipsoid-pyriform, (70–)100–120(–150) µm long, brown with internal walls thin and dark red, non-protuberant surface cells. Laminal KOH colour reaction yellow.

Perichaetia with leaves conspicuously sheathing the seta base and the inner leaves strongly differentiated, appressed, acuminate or rounded at apex from a long, tightly convolute base, with upper laminal cells vermicular and smooth. Perigonia not seen in N.Z. material. Setae slender, yellow, 10–16 mm. Capsules erect, asymmetric, subcylindric, tapering from near base to mouth, brown, becoming red at the mouth, with a well-developed annulus, 2.0–2.6 mm. Operculum long-conic, ⅓ –½ the theca length with cells spirally arranged. Peristome c. 1.0 mm, light brown, of 32 spiralled rami, densely spiculose, very weakly articulate, twisted several times to the right from a low basal cylinder. Spores 8–10 µm, smooth.

The reinstatement of the segregate genus Streblotrichum P.Beauv. was proposed by Kučera et al. (2013) to accommodate those species of Barbula​​​​​​​ s.l. that have strongly differentiated, convolute perichaetial bracts and a well-differentiated annulus. These characters have traditionally been associated with the name Streblotrichum, whether at generic, subgeneric or sectional rank (see, for example, Saito 1975, Zander 1993). Additional characters that also delimit Streblotrichum include a yellow seta and the formation of brown, spherical, rhizoidal gemmae (Kučera et al. 2013), all of which characters are present in the sole N.Z. representative of the genus S. convolutum.