Grimmia atrovirens Smith
Leaves ovate to lingulate, apex broadly acute to rounded, apiculate or mucronate, margins revolute or occasionally plane, often bordered proximally with rectangular cells usually hidden in the revolute margins; costa percurrent or ending in apiculus or short mucro, with an adaxial pad of swollen cells similar to those of the lamina, distally broad, (4--)6(--8) cells across adaxial surface; distal laminal cells subquadrate, 9--13(--18) µm wide, µm, 1:1; strongly papillose. Sexual condition autoicous. Sporophytes exerted. Seta 0.6--1.2 cm. Capsules stegocarpic, not systylius, cylindric to ellipsoidal, erect and nearly straight, urn 0.9--1.5 mm; peristome commonly 210--390 µm, teeth of 32 filaments, weakly twisted, occasionally rudimentary, basal membrane 40--50 µm; operculum 0.5--0.7 mm. Spores 15--18 µm, broadly ellipsoidal, nearly smooth.
Capsules mature winter--spring. Exposed soil, volcanic ash, rock, often calcareous; 0--2200 m; Alta., B.C.; Ariz., Calif., Colo., Idaho, Minn., Nev., N.Mex., Tex., Utah; Mexico; South America; Europe; Asia; Africa; Atlantic Islands; Australia; Pacific Islands (including Hawaii and New Zealand).
The species has a massive pad of bulging cells covering the costa, and may be mistaken for a Crossidium, which, however, has a ventral pad of filaments. It is somewhat similar to Tortula obtusifolia, which also has weakly differentiated, smooth, somewhat elongate marginal cells, but that species of more mesic climates and more northern latitudes has spatulate leaves lacking an adaxial pad.