Plants in hemispherical hoary cushions, greyish green. Stems 1--3 cm, central strand present. Stem leaves flexuose when dry, erect when moist, lanceolate, 1--1.7 × 0.3--0.6 mm, keeled, margin recurved on both sides nearly from base to apex, abruptly contracted into short to long, smooth to denticulate awn, costa weak proximally, projecting on dorsal side; distal laminal cells 1-stratose, margins 2-stratose; medial laminal cells rounded-quadrate, slightly sinuose, thin-walled; basal juxtacostal laminal cells short-rectangular, thin-walled; basal marginal laminal cells quadrate, thin-walled. Gemmae absent. Sexual condition autoicous. Seta arcuate, 3--4 mm. Capsule usually present, exserted, ellipsoid to obloid, brownish and ribbed when empty and dry, exothecial cells thin-walled, annulus present, operculum rostrate, peristome teeth reddish, fully developed, papillose. Calyptra mitrate.

Various substrates, from acidic to basic rock, with a preference for old mortar, tree trunks; 0--3000 m; Alta., B.C., Ont.; Calif., Colo., Ind., Iowa, Md, Mich., Miss., Nev., Tex., Utah, Wash.; Mexico; South America (Argentina, Chile, Uruguay); Eurasia; Africa; Pacific Islands (New Zealand); Australia.

Grimmia pulvinata is the most common Grimmia species. It has a nearly cosmopolitan distribution, and is a pioneer on various substrates, even on the trunks of trees. However, in the eastern part of North America, it occurs only in a few scattered localities (H. A. Crum 1977). Grimmia pulvinata is easily recognized by its neat spherical cushions with abundant capsules. It may be confused with G. orbicularis, having a comparable habit and growing in the same habitat. However, as discussed above, it differs both in gametophytic as well as sporophytic characters. Some forms with more acuminate leaf tips may be confused with G. trichophylla, but the thin-walled, short-rectangular basal cells and the small rounded midleaf cells will distinguish G. pulvinata.