Plants in loose to dense tufts, light to dark green, glossy to sometimes dull. Stems 2-10 cm, tomentose with white to brown rhizoids. Leaves very variable, usually falcate-secund, rarely straight and erect, slightly contorted and crisped when dry, sometimes slightly rugose or undulate, (4-)5-8.5(-15) × 0.8-1.8 mm, concave proximally, keeled above, lanceolate, apex acute to somewhat obtuse; margins strongly serrate in the distal 1/3 or rarely slightly serrulate; laminae 1-stratose; costa percurrent, excurrent, or ending before apex, 1/10-1/5 the width of the leaves at base, usually with 2-4 toothed ridges above on abaxial surface, with a row of guide cells, two thin stereid bands, adaxial epidermal layer of cells not differentiated, the abaxial layer interrupted by several enlarged cells that form part of the abaxial ridge, not extending to the apices; cell walls between lamina cells not bulging; leaf cells smooth; alar cells 2-stratose, well- differentiated, sometimes extending to costa; proximal laminal cells linear-rectangular, pitted, (25-)47-100(-132) × (5-)7-12(-13) µm; distal laminal cells shorter, broad, sinuose, pitted, (11-)27-43(-53) × (5-)8-12(-20) µm. Sexual condition pseudomonoicous or dioicous; dwarf males on rhizoids of female plants or male plants as large as females; interior perichaetial leaves abruptly long-acuminate, convolute-sheathing. Seta 2-4 cm, solitary, rarely two per perichaetium, yellowish brown to reddish brown. Capsule 2.5-4 mm, arcuate, inclined to horizontal, smooth to striate when dry, yellowish brown to reddish brown; operculum 2-3.5 mm. Spores 14-24 µm. Capsules mature spring. Soil, humus, humus over rock, decaying stumps and logs, tree bases in dry to mesic woodlands; sometimes bogs, fens and swamps; 50-2900 m; Greenland; Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico; Europe; Asia; Pacific Islands (New Zealand); Australia.