Amblystegium Schimp.

Plants minute to medium-sized, forming loose yellow-green or bright-green mats. Stems creeping, irregularly or subpinnately branched, with a central strand. Stem and branch leaves differing only by size. Stem leaves erect or spreading when moist, sometimes homomallous, erect to appressed when dry, ovate to narrowly lanceolate, often constricted at insertion, gradually or abruptly tapered to acumen, mostly plane, denticulate (in N.Z. species) or entire; mid laminal cells variable in shape (oblong hexagonal or rhomboid to oblong in N.Z. species), firm- or thin-walled, smooth, mostly lacking pores; alar cells differentiated or not (in N.Z. species ± quadrate and firm-walled, forming a large but ill-defined group). Costa single, from c. ⅓ the leaf length to percurrent. Axillary hairs with 1–2(–3) terminal hyaline cells. Asexual propagula lacking. Pseudoparaphyllia small, foliose. Paraphyllia absent or rarely present (and then filamentose or lanceolate).

Autoicous. Perichaetial leaves lanceolate, costate, smooth or plicate, sheathing the base of the setae. Perigonia gemmiform and scattered on fruiting stems in N.Z. species. Setae elongate, smooth, ± red when fresh; capsule cylindric from a moderately defined neck, strongly curved (in N.Z. species) or rarely ± erect, constricted below the mouth when dry; exothecial cells firm-walled, ± oblong; stomata present; annulus differentiated; operculum bluntly conic or rarely short-rostrate. Peristome hypnoid, as per family; exostome pale yellow-brown, transverse-striolate below, distinctly bordered; endostome well-developed or rarely reduced, with cilia in groups of 1–3 in N.Z. species, usually nodose. Calyptra cucullate, naked. Spores finely papillose or smooth.

Amblystegium is treated here in a sense similar to that presented by Hedenäs (2003) and the generic description above borrows elements from his treatment. Amblystegium varium was isolated into a monotypic genus Orthotheciella by Ochyra (1998) who emphasised the presence of "uniseriate, filiform paraphyllia on the surface of the stem and branches." However, I agree with Hedenäs (2003) that the presence of paraphyllia alone is insufficient reason to recognise Orthotheciella.

Members of Amblystegium are mostly small to minute, with singly-costate, ovate to lanceolate leaves and large but ill-defined groups of quadrate alar cells. The plants are autoicous and frequently produce fruit; the capsules can be useful to separate the present genus from superficially similar taxa belonging to unrelated genera such as Fabronia and Rhynchostegiella.

The name Amblystegium juratzkanum Schimp. was tentatively applied to one N.Z. collection (G.O.K. Sainsbury 874 ex Māhia Peninsula, CHR 602723) by Dixon. This taxon is closely allied to A. serpens and in recent floras is often treated as either a synonym (Smith 2004) or a variety of it. When recognised at all the variety is differentiated primarily by having more widely spreading leaves (Crum & Anderson 1981). The bulk of N.Z. collections of A. serpens have leaves rather widely spreading when moist. Amblystegium juratzkanum is not considered further.