Plants small, moderately sized to large, loosely to densely caespitose or forming extensive mats or patches, green, yellow- to grayish green or yellow-brown, sometimes olive with rusty-red tinge, often hoary when dry. Stems creeping, procumbent to ± erect, irregularly to pinnately, sparingly to copiously branched, often with numerous, short tuft-like branches. Leaves erect-appressed when dry, erect-spreading to squarrose when moist, ovate, elliptical, ovate-lanceolate, triangular, to lanceolate, obtusely to sharply keeled or broadly canaliculate distally; margins 1-stratose throughout, recurved on both sides to mid leaf or to apex; apices long- to broadly short-acuminate, sometimes muticous, usually awned, awn stout to capillaceous, straight, flexuose, or reflexed, not or decurrent, smooth or denticulate, papillose or epapillose; costa single, ending in mid leaf to percurrent, entire or branched distally, strongly flattened abaxially, 2-stratose throughout or 3-stratose in the base; basal laminal cells elongate to linear, sinuose-nodulose; alar cells mostly enlarged, thin-walled, hyaline to yellowish, forming somewhat inflated and decurrent auricles; supra-alar cells hyaline or yellowish, quadrate to rectangular, not sinuose or sinuose, epapillose, thin- or thick-walled, often forming a distinct or indistinct pellucid border; medial and distal laminal cells 1-stratose, subquadrate, to short-rectangular, sinuose, with tall, stout, conical papillae over lumina on both surfaces. Perichaetial leaves differentiated, hyaline or yellowish, obtuse to acute, sometimes piliferous. Seta yellowish to blackish red, erect, sinistrorse when dry, smooth. Capsule narrowly ellipsoid, obloid to cylindric, smooth to somewhat sulcate when dry; annulus tardily deciduous, 2–3-seriate; operculum very long-subulate, straight; peristome teeth nearly as long as the urn or longer, red-brown, divided almost to the base into 2 or rarely 3 linear-subulate, densely papillose branches. Calyptra verrucose distally. Spores globose, finely papillose.
North America, Europe, arctic and temperate Asia, Atlantic Islands (Azores, Iceland, Madeira).
Species 8 (6 in the flora).
Niphotrichum comprises species from the traditionally conceived genus Racomitrium centered around R. canescens. It is characterized by strongly papillose laminal cells with tall conical papillae that are situated over the lumina. This type of papillosity is common, for example, in the Pottiaceae but is unique in the Grimmiaceae. This exceptional diagnostic character is coupled with very long peristome teeth that are regularly cleft to the base into 2–3 filiform segments, and hyaline or yellowish hyaline and thin-walled alar cells that form convex and often decurrent auricles. Moreover, species of this genus possess massive, papillose, and denticulate awns; costae forked or branched at the tip, ending at mid leaf or extending to the leaf apex; triangular, elliptic, or broadly ovate-lanceolate leaves; innermost perichaetial leaves hyaline, sheathing, and sometimes pilose; setae smooth, sinistrorse on drying; operculum with a subulate beak as long as the urn or longer; and capsules often plicate when dry.
|1||Leaves obtusely keeled to broadly canaliculate in the distal part, elliptical to broadly ovate-lanceolate; costa mostly distinctly branched, extending 1/2-3/4 of the way up the leaf; papillae tending to be relatively large and conspicuous in the distal part of the leaf lamina.||Niphotrichum sect. Niphotrichum|
|1||Leaves sharply keeled to narrowly canaliculate in the distal part, ovate-lanceolate to triangular; costa mostly unbranched, extending 3/4 of the way up the leaf to percurrent; papillae tending to be relatively small and inconspicuous in the distal part of the leaf lamina.||Niphotrichum sect. Elongata|