Orthotrichum laevigatum, Oefv. Svensk Vet. Ak. Foerh. 19: 363. -- Dorcadion laevigatum (Zett.) Lindb., Musci Scand. 28. 1879. -- Orthotrichum speciosum var. laevigatum (Zett.) Amann, Fl. Mousse Suisse 2: 163. 1918. -- Orthotrichum speciosum var. brevicaule Lesq., Mem. Calif. Acad. Sci. 1: 17. 1868. -- Orthotrichum speciosum var. polyanthum Lesq., Mem. Calif. Acad. Sci. 1: 18. 1868. -- Orthotrichum kingianum Lesq., Mem. Calif. Acad. Sci. 1: 18. 1868 -- Orthotrichum laevigatum var. kingianum (Lesq.) Grout, Moss Fl. N. Am. 2: 113. 45. 1935. -- Orthotrichum macounii Aust., Bull. Torr. Bot. Club 6: 343. 1879. -- Orthotrichum roellii Vent. in Roell, Bot. Centralbl. 44: 390. 1890. -- Orthotrichum speciosum var. hainesiae (Aust.) Par., Ind. Bryol. ed. 1 896. 1897. -- Orthotrichum raui Aust., Bull. Torr. Bot. Club 6: 343. 1879. -- Orthotrichum speciosum var. raui (Aust.) Lesq. & James, Man. N. Am. Moss. 169. 1884. -- Orthotrichum macounii Aust., Bull. Torr. Bot. Club 6: 343. 1879. -- Orthotrichum laevigatum fo. macounii (Aust.) Lawton & Vitt in Lawton Moss Fl. Pacific Northwest 222. 1971. -- Orthotrichum speciosum var. polycarpum Lesq. & James, Man. N. Am. Moss. 169. 1884. -- Orthotrichum stenocarpum Vent. in Roell, Bot. Centralbl. 44: 389. 1890. -- hom. illeg. -- Orthotrichum roellii ssp. stenocarpum (Vent. in Roell) Kindb., Eur. N. Am. Bryin. 2: 301. 1897. -- Orthotrichum roellii Vent. in Roell, Bot. Centralbl. 44: 390. 1890.

   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: Colusa Co.: Summit Springs south of Snow Mountain, Mendocino National Forest, Norris 76126; Inyo Co.: about 3 miles south of Schulman Grove, White Mountains, Inyo National Forest, Norris 46857; Lake Co.: Cobb Mountain Summit, Toren & Dearing 7387 (CAS); Lassen Co.: Amedee Canyon north of Honey Lake, Norris 81028; San Bernardino Co.: west end Bluff Lake, San Gorgonio Wilderness, San Bernardino National Forest, Harpel 599 (pers. herb.); Shasta Co.: Pit River about 2 miles below powerhouse #2, Shasta-Trinity National Forest, Norris 82591; Tulare Co.: Trail 34E08 southeast of Manter Meadow near Black Mountain, Domeland Wilderness, Sequoia National Forest, Shevock 10827.

Literature: Flowers 1973; Harpel 1980a; Harthill et al. 1979; Koch 1950a, 1951e, 1958; Koch and Ikenberry 1954; Lawton 1971; Long 1978; McGrew 1976; Mishler 1978; Showers 1982; Sigal 1975; Spjut 1971; Toren 1977. As Orthotrichum kingianum Lesquereux 1868; Lesquereux and James 1884; Watson 1880. As Orthotrichum roellii Koch 1950a.

Illustration References: Crum and Anderson 1981; Ignatov and Ignatova 2003.

Elevation by latitude plot for Orthotrichum laevigatum
   in California