Bryum capillare Hedwig, Sp. Musc. Frond., 182. 1801

Plants small, bright green. Stems 0.5-1.5 cm, distinctly singly rosulate, innovations short, rosulate. Leaves of main rosette and innovations similar, regularly spirally twisted around stem, erect-spreading when moist, obovate, weakly concave, 0.5-2.5 mm; base not decurrent; margins recurved to mid leaf, distinctly serrulate distally, limbidium present, of 1-3 rows of cells; apex acute; costa long-excurrent, awn sometimes hyaline, slender, irregularly twisted when dry; proximal laminal cells long-rectangular in rosette leaves; medial and distal cells short-rhomboidal, 12-25 µm wide, 3-4:1, walls thin, not porose. Specialized asexual reproduction by rhizoidal tubers, , red-brown, , 200-300 µm, . Sexual condition dioicous. Capsule inclined, red-brown, cylindric to elongate-pyriform, 3-5 mm.

Capsules mature May-Jul. Moist shaded soil, soil banks, rotting wood; low to high elevations (0-2500 m); Greenland; Alta., B.C., Man., N.B., Nfld. and Labr., N.S., Ont., P.E.I., Que., Sask.; Alaska, Ariz., Ark., Calif., Colo., Conn., Del., Idaho, Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.Dak., Ohio, Oreg., Pa., R.I., S.C., Tenn., Utah, Vt., Va., Wash., W. Va., Wis., Wyo.; Mexico; West Indies; Central America; South America; Eurasia; Africa; Atlantic Islands (including Macaronesia); Pacific Islands (New Zealand); Australia.

Traits diagnostic for the protean Rosulabryum capillare are leaves spirally twisted around the stem, long awn, distinct border, and serrulate margins, small size, rosulate innovations, and rhizoidal tubers the same color as the rhizoids. Rosulabryum gemmascens has irregularly contorted leaves with a much weaker border and nearly entire margins, and elongate somewhat imbricate innovations of small red-brown ovate leaves. Rosulabryum laevifilum has a much more variable costa that sometimes does not reach the apex, green leaves, and filiform gemmae. Rosulabryum torquescens has irregularly contorted leaves with strongly serrate margins and red to crimson tubers, brighter than the rhizoids, and is usually synoicous.