2b. Grimmia subg. Guembelia (Hampe) Schimper, Coroll. Bryol. Eur. 48. 1856.
Guembelia Hampe, Bot. Zeitung (Berlin) 4: 124. 1846
Plants 10-20 mm (-70 mm for G. atrata). Stem central strand present or absent. Leaves narrowly ovate-lanceolate to oblong-lanceolate, keeled, margins plane, recurved or incurved, costa prominent; basal marginal cells hyaline or not; distal lamina 2-stratose or with at least several marginal rows 2-stratose. Gemmae absent. Sexual condition autoicous or dioicous. Seta straight, centrally attached to capsule. Capsule immersed to exserted, smooth (except G. mariniana); stomata present or absent, small, at neck to part way up capsule. Calyptra mitrate to cucullate, covering operculum.
Species 41 (13 in the flora): North America, Mexico, Central America, South America, Eurasia, Africa, Pacific Islands, Australia, Antarctic.
Members of subg. Guembelia are recognized by their thick, keeled leaves and usually long, straight setae with smooth capsules. Most occur on dry acidic rock, with three species growing on damp to wet acidic rock and one on dry calcareous rock.