Plants: in cushions or low, sometimes extensive tufts, olivaceous or yellowish brown. Stems: 0.8â2.5 cm, central strand distinct. Leaves: erect or curved, rarely falcate, imbricate when dry, lanceolate to ovate-lanceolate, strongly keeled distally, (0.9â)1.4â2(â2.3) mm, 1-stratose; margins usually recurved to just before the apex, proximally often more broadly recurved on one side of leaf, distal 1/3 often plane, smooth, 1-stratose with 2-stratose sections; apices acute or sub-obtuse; costa excurrent as a denticulate, flexuose, usually strongly decurrent awn, often embracing part of the lamina, smooth; basal marginal cells short-rectangular, occasionally with transverse walls thicker than longitudinal walls; distal cells mainly short-rectangular or quadrate, 7â10(â11.5) µm wide, smooth, usually strongly sinuose. Sexual: condition autoicous. Capsule: orange-brown or reddish brown, campanulate, 0.5â0.6 mm; exothecial cells short-elongate or isodiametric, often more or less quadrate, thin-walled or slightly thickened, small trigones usually present; stomata present; operculum rostrate; peristome rudimentary, consisting of basal segments, or absent, yellowish, papillose. Spores: 8â12 µm, verruculose. Phenology: Capsules mature late spring to early summer. Habitat: Shallow crevices and cavities on basalt cliffs Elevation: low to moderate elevations (60-1200 m) Distribution: Greenland, N.W.T., Que., Alaska.
Discussion: The long, usually strongly decurrent awns and the campanulate capsules absent a distinct peristome separate Schistidium cryptocarpum from other arctic species of the geunus. Mogensen and Blom provided further details on this species. It should be confused only with S. flaccidum, a more southern species, which differs in having a mamillate rostrum and a cupulate capsule.