Orthotrichum rupestre, Spec. Musc. Suppl. 1(2): 27. 53. 1816. -- Dorcadion rupestre (Schwaegr.) Lindb., Musci Scand. 29. 1879. -- Orthotrichum texanum Sull. & Lesq., Musci Bor. Amer. (ed. 1) n. 122. 28. 1856. -- Orthotrichum texanum var. globosum Lesq., Mem. Calif. Acad. Sci. 1: 17. 1868. -- Orthotrichum rupestre var. globosum (Lesq.) Grout, Moss Fl. N. Am. 2: 110. 1935. -- Orthotrichum bullatum C. Muell., Flora 70: 223. 1887. -- Orthotrichum macfaddenae Williams, The Bryologist 31: 52. 1928. -- Orthotrichum rupestre var. macfaddenae (Williams) Grout, Moss Fl. N. Am. 2: 111. 1935.

   Plants spreading in dark green to yellow-green tufts, often prostrate with only the branch tips ascending, and with the main axes to 10 cm long. Leaves spreading to strongly spreading when moist but appressed when dry, ovate-lanceolate to lanceolate, broadest near the base, with acute to narrowly obtuse apices, to 4 mm long, about 3–4: 1. Median laminal cells to 10 µm wide, arranged in somewhat regular rows, isodiametric to slightly elongate along an oblique axis. Lumens of the median cells rounded due to the strong corner thickenings. Papillae arranged over the lumens on each surface, 1–2, often bifid. Basal marginal cells to 12 µm wide, isodiametric to short rectangular, pellucid and smooth, usually clustered in a small rounded and leptodermous auricle on at least one margin. Basal juxtacostal cells mostly smooth, rectangular, to 15 µm wide, 6: 1, pitted, reddish-brown or concolorous. Cells on adaxial surface of costa elongate and pitted in 1–2 rows. Margins markedly papillose crenate, recurved from base to near the apex. Costa ending within a few cells of apex, lying in a sharply defined keel. Costa cross-section nearly homogeneous but with a single layer of abaxial cells smaller than the more adaxial ones. Costa mostly 4 cells thick, and with more than 10 cells along the abaxial perimeter. Median axillary hairs with one basal brown cell, not offset from leaf insertion, to 12 cells and 500 µm long with the laterally inserted ones much shorter than the lateral ones. Rhizoids very sparsely produced at base of plant, to 30 µm in diameter at insertion, smooth, brown to pale-brown, sparingly branched. Stem cross-section without a central strand, mostly with leptodermous and hyaline inner corticals and with 1–3 layers of strongly pachydermous, red brown outer cortical cells.

   Autoicous with perigonia in leaf axils near the perichaetia. Perichaetial bracts not differentiated from vegetative leaves. Capsule immersed to somewhat emergent on a yellow to yellow brown, smooth and erect seta which seldom exceeds 1.5 mm in length. Urn pale-brown, to 2 mm long, 1.5–2: 1, erect, strongly or lightly sulcate with eight well-defined ribs, lightly or not at all strangulate. Operculum conic-apiculate to short rostrate. Annulus well-defined, falling in fragments. Exothecial cells in cross-section single-layered. Exothecial cells at capsule mouth often strongly reddened, to 35 µm wide, transversely elongate with rounded lumens in up to 6 rows. Exothecial cells at middle of urn rather thick walled with lumen: wall ratio 4–6: 1, short rectangular, 2–4: 1, to 25 µm broad, strongly differentiated from ridge to valley of the sulcate capsule. Stomata phaneroporous, scattered on proximal 1/2 of urn. Exostome teeth erect to spreading when dry, seldom or never fused in pairs, pale to light yellow, to 300 µm long, lightly or not at all papillose. Endostome segments consistently absent. Calyptra campanulate, lightly covered with papillose hairs. Spores green, to 20 µm, rather coarsely papillose.

Vouchers: Fresno Co.: Mist Falls trail near junction with Bubbs Creek, Kings Canyon National Park, Shevock & York 14478; Humboldt Co.; Forest Road 7K100 at junction of road to Horse Mountain Ski Lift, Six Rivers National Forest, Norris 70665; Lake Co.: The Openings above Cedar Creek, Mendocino National Forest, Toren & Shevock 8093 (CAS); Modoc Co.: west side Goose Lake about 4 miles south of Oregon border, Norris 23656; Orange Co.: Upper Trabuco Canyon, Santa Ana Mountains, Cleveland National Forest, Shevock 3991; Santa Clara Co.: Mt. Hamilton about 1 mile below summit, Koch 1421 (UC).

Literature: Bourell 1981; Cooke 1941; Harpel 1980a; Harthill et al. 1979; Kellman 2003; Kingman 1912; Koch 1950a, 1951e, 1958; Koch and Ikenberry 1954; Lawton 1971; Lesquereux 1868; Lesquereux and James 1884; Long 1978; McGrew 1976; Mishler 1978; Moxley 1928; Showers 1982; Sigal 1975; Spjut 1971; Steere et al. 1954; Strid 1974; Toren 1977; Watson 1880; Whittemore and Sommers 1999; Yurky 1990, 1995. As Orthotrichum sturmii Lesquereux 1868; Lesquereux and James 1884; Watson 1880.

Illustration References: Malcolm et al. 2009 p. 211; Flowers 1973; Ignatov and Ignatova 2003; Ignatov and Lewinsky-Haapasaari 1994; Lawton 1971; Lewinsky 1987, 1993; Sharp et al. 1994; Smith 1978; Vitt 1973.

Elevation by latitude plot for Orthotrichum rupestre
   in California