Grimmia pellucida Kindberg; G. prolifera Müller Hal. & Kindberg; G. pseudotorquata Kindberg; G. tortifolia Kindberg

Plants in soft, readily disinte-grating cushions, yellow-green to brownish, occasionally light green, blackish to red-brown inside. Stems 1-4 cm, small central strand present. Leaves contorted when dry, patent when moist, lanceolate, 1.5-2 × 0.3-0.5 mm, keeled, margins slightly recurved proximally, plane distally, awns very short and smooth, occasionally absent, costa weak proximally, projecting on abaxial side; basal juxtacostal laminal cells linear, extremely sinuose, thick-walled; basal marginal laminal cells long rectangular, thin-walled, hyaline; medial laminal cells rectangular, extremely sinuose, thick-walled; distal laminal cells 1-stratose. Gemmae brown, multicellular, present on the abaxial side of distal leaves. Sexual condition dioicous. Seta slightly curved, straight when dry, 3-5 mm. Capsule sporadically present, exserted, ovoid, brown, smooth, striate when dry and empty, exothecial cells thin-walled, annulus present, operculum rostrate, peristome teeth yellowish, short, split in distal part, weakly papillose. Calyptra mitrate.

Damp, frequently vertical faces of acidic rock; moderate to high elevations (200-4000 m); Greenland; Alta., B.C., Nfld. and Labr., N.W.T., Ont., Que., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Mont., Nev., Oreg., Wash., Wyo.; Mexico; Eurasia; n Africa; Pacific Islands (Hawaii).

Grimmia torquata is a montane-alpine species with a preference for shaded habitats. It grows in hemispherical cushions on steep, damp rock walls. Preferred substrates are granite, gneiss, quartzite, and schist. Its distribution reaches from near sea level in the Arctic to above 4000 m on Mexican and Hawaiian volcanoes. The species is easily recognized by its yellow-brown cushions of plants, which have contorted leaves when dry, and their brown gemmae, which are borne at the bases of older leaves. In densely shaded habitats, the cushions are light green; on exposed rock, they are usually brown. Although the species has a wide distribution, it is seldom present in quantity, usually growing in a small number of cushions in one habitat. Sporophytes are very rare worldwide and have not been found in eastern North America (H. A. Crum and L. E. Anderson 1981).