Plants: to 3 cm. Stem: leaves erect-appressed and straight when dry, ligulate, elongate- to ovate-lanceolate, 2–4 mm; margins recurved-revolute to just below apex, entire; apex acute; basal laminal cells long-rectangular to elongate, walls thick, nodose; distal cells 9–13 µm, 1-stratose, papillae 2 or 3 per cell, 2-fid, low. : Specialized asexual reproduction absent. Sexual: condition gonioautoicous. Seta: 1–2.2 mm. Capsule: 1/2 emergent to short-exserted, long-cylindric when mature, cylindric and constricted along entire length when old and dry, 1.6–2.5 mm, strongly 8-ribbed 2/3 capsule length; stomata superficial; peristome double; prostome absent; exostome teeth 8, erect when mature, reflexed to reflexed-recurved when old, coarsely and obscurely papillose or sometimes papillose-reticulate, deeply perforate, cancellate; endostome segments 8, rarely 16, well developed, usually present when capsule is old and dry, narrow, of 2 rows of cells, papillose. Calyptra: conic-oblong, smooth, hairs few, papillose. Spores: 15–18 µm.
Deciduous trees, shaded rock, shaded forests near stream beds, canyons, mountains. low to high elevations (0-3000 m). Alta., B.C., Calif., Colo., Idaho, Mont., Oreg., Utah, Wash., Europe, Asia, n Africa.
Orthotrichum affine, a species confined to western North America in the flora area, is best recognized by: superficial stomata; cylindric, strongly ribbed, almost exserted capsules; a well-developed but not stout endostome; and a calyptra that is only sparsely hairy.
Plants: 0.5–2.3 cm. Stem: leaves loosely erect-appressed and ± loosely twisted when dry, elongate- to ovate-lanceolate, 2–3.5 mm; margins revolute to below apex, entire; apex sharply acute, sometimes acuminate, cuspidate, or apiculate; basal laminal cells long-rectangular to rectangular, walls thin, sometimes nodose at insertion; distal cells 9–14 µm, 1-stratose, papillae 2 or 3 per cell, conic or 2-fid, large. : Specialized asexual reproduction on leaves. Sexual: condition gonioautoicous. Seta: to 1.4 mm. Capsule: 1/2–3/4 emergent, sometimes almost exserted, oblong-ovate when mature, oblong to short-cylindric when old and dry, to 1.4 mm, strongly 8-ribbed 2/3 to entire length, constricted below mouth when dry; stomata immersed, 1/2 covered by subsidiary cells, cells projecting, inner walls thickened; peristome double; prostome absent; exostome teeth 8, reflexed, densely and evenly papillose, striate-reticulate distally; endostome segments 8 or 16, well developed, of 1 or 2 rows of cells, smooth or finely roughened. Calyptra: oblong, smooth, ± hairy, hairs strongly papillose. Spores: 10–15 µm.
Rock, trees, base of trees, moist crevices of large boulders, moist pine and deciduous forests. high elevations (2100-3000 m). Greenland, Alta., B.C., Nfld. and Labr., Ont., Yukon, Ariz., Calif., Colo., Idaho, Mich., Mont., Nev., N.Mex., Oreg., S.Dak., Utah, Wash., Wyo., Europe, Asia, Pacific Islands (New Zealand).
Orthotrichum alpestre is distinguished by the highly papillose distal laminal cells; slightly twisted, sharply pointed leaves; calyptra with papillose hairs; absence of prostome; and papillose or papillose-reticulate exostome. The endostome is always present in mature capsules and, because of enlarged cross walls, has a shiny appearance. The capsule is usually oblong and strangulate, although the shape depends on age. In some specimens, the capsule is short-cylindric and not much constricted below the mouth. The stomata are found just below mid capsule.