Orthotrichum flowersii Vitt, Bryologist. 74: 159. 1971.
Plants to 5 mm. Stem leaves stiffly-erect and loosely-appressed when dry, ovate-oblong to oblong-ligulate, 2--2.8 mm, rounded or obtuse, often mucronate, carinate, subcucullate; margins revolute, entire or crenulate by means of projecting papillae near apex; distal laminal cells 13--19 µm wide, 1-stratose, with ± 2, small, conical papillae; basal laminal cells rectangular to short-rectangular, non-nodose. Sexual condition autoicous. Seta ± 0.5 mm. Capsule immersed or shortly emergent; urn ovate-oblong to oblong when mature, 1--1.4 mm, strongly 8-ribbed 1/2 to 3/4 the length of the capsule, stomates immersed, in 1 or 2 rows at middle of the capsule, guard cells barely to 1/2 covered by subsidiary cells which have inner walls ± thickened; peristome double; endostome segments 8, usually of 1 row of cells, finely roughened; exostome teeth 8, reflexed, densely papillose or papillose-striate above. Calyptra oblong, naked or with a few hairs. Spores 10--17 µm.
Base of tree trunks and trunks of deciduous trees in xeric and exposed habitats; 500--2000 m; Calif., Idaho, Nev., Utah; Europe.
This species is distinguished from O. pumilum and O. pallens by having blunt, carinate leaves that are ovate or ovate-oblong, and almost always have a small mucro.