Holodontium (Mitt.) Broth.

Plants robust, yellow-green when fresh and moist, becoming brown-green when dry, dull, forming extensive turves on irrigated rock. Stems c. 40-50 mm, much branched by both forking and innovation, in cross-section lacking a central strand, with 2-3 layers of small, thick-walled cortical cells, sparsely beset with red-brown, smooth, weakly branched, and ± straight rhizoids (mostly arising in leaf axils). Leaves secund and strongly curved or falcate both moist and dry, linear-lanceolate and evenly tapered throughout, ± auriculate and clasping at insertion, the distal ⅓ to ½ filled by the costa (see notes below), rounded at the apex, entire, broadly U-shaped throughout, 3.0-6.5 mm, variable in size on single stem; laminal cells (c. ⅓ above base) quadrate to short-rectangular, c. 6-12 × 5-6 µm, firm-walled, forming a broad bistratose juxtacostal band (not well illustrated in plate 000), unistratose in 4-5 marginal rows, with fine cuticular striations (apparently on both surfaces) that extend between cells; laminal cells closer to the leaf base becoming unistratose and more pellucid, not elongate, forming a large area of more clearly defined cells immediately above the alar cells; alar cells strongly inflated and rounded, to c. 30-40 × 25 µm, ± pigmented, forming a large, well-defined and ± auriculate group extending to the costa and sometimes remaining attached to the stem when the leaves are removed. Costa stout, c. 290-325 µm wide, c. ⅓ to ½ the leaf width, and well-defined in lowest 1 mm of leaf, rapidly becoming ill-defined above; in surface view with short-rectangular cells on the adaxial surface and quadrate cells on the abaxial surface; in cross-section (at mid leaf) C-shaped, with a row of median guide cells and with the abaxial surface cells appearing finely papillose due to cuticular striations.

Autoicous. Perichaetia terminal but usually overtopped by innovation, often 2 or more per shoot, with perichaetial leaves differentiated, usually shorter than vegetative leaves, sheathing at base and ± distinctly shouldered. Perigonia on very short shoots at the base of the perichaetia, with the inner bracts short, oblong-ovate, and weakly costate; antheridia <10 per perigonium, mixed with filiform, uniseriate paraphyses. Setae (12-)18-23 mm, flexuose and sinistrorse, yellow-brown; capsules broadly ellipsoid and scarcely constricted below the mouth when dry, scarcely altered when moist, 1.3-1.5 × 0.8-0.9 mm, smooth; exothecial cells at mid urn rounded-polygonal, firm-walled, weakly collenchymatous, becoming isodiametric or ± oblate in several rows at the mouth; stomata restricted to capsule base, superficial; operculum long-rostrate from a conic base, oblique, ± equal the capsule in length, probably systylious. Peristome teeth well-developed, inserted close to rim, yellow-brown, very irregular in outline, often anastomosing and then the paired teeth appearing cribose, to 270 µm long × 75 µm wide (when paired, the fused teeth collectively to c. 120 µm wide), the outer surface trabeculate-lamellate, either coarsely verrucose or sometimes nearly smooth, the inner surface with an irregular median line, thicker cell walls, and moderately to strongly verrucose; preperistome absent in N.Z. material. Calyptra cucullate, smooth. Spores 22-30 µm, finely papillose, brown.

Holodontium is a small genus of austral distribution. It was placed in the Dicranaceae (subfamily Dicranoideae) in the general relationship of Dicranoweisia by Brotherus (1924). Brotherus included five species in Holodontium, including three that occur in N.Z. These three species are here excluded from the genus and discussed under Kiaeria in the Dicranaceae.

More recently, Holodontium was monographed by Ochyra (1993), who reduced it to a single species and placed it in the Seligeriaceae, while continuing to postulate a relationship to Dicranoweisia. The placement by Goffinet et al. (2009) of Holodontium in the Rhabdoweisiaceae is accepted for the purposes of this Flora. The description of H. strictum, which is the sole accepted species (and an earlier name for the nomenclatural type), applies to the genus.