Orthotrichum alpestre var. majus Lesquereux & James; O. alpestre var. watsonii (James) Grout; O. occidentale James; O. watsonii James

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.