Schistidium agassizii, Musci & Hep. U.S. 104. 1856. -- Grimmia agassizii (Sullivant & Lesquereux) Jaeger, Ber. S. Gall. Naturw. Ges. 1872–73: 66. 1874.

   Plants to 3.5 cm high, in blackish-green to very black cushions, but with young leaves dark green. Leaves lightly to strongly imbricate when dry, erect-spreading when moist, shallowly concave below but not distally keeled, to 4 mm long without an awn, narrowly lanceolate from near the base, 5–7: 1. Median leaf cells in very regular longitudinal rows, unistratose throughout or with a single row of bistratose cells at the margin, smooth, to 12 µm wide, isodiametric to elliptic, 1–1.3: 1, with lumens regular and with indistinct corner thickenings. Marginal cells not differentiated. Basal marginal cells quadrate and regular with transverse walls only slightly thickened relative to lateral walls. Basal juxtacostal cells rectangular and rather thin-walled, to 3: 1, to 12 µm wide, with lateral walls straight. Cells of alar region to 12 µm wide, quadrate to short rectangular with quadrate lumens, with lumen: wall ratio 4–6: 1; little different from more distal laminal cells. Costa filling about 1/8 of immediate leaf base, little tapered above, percurrent and filling most of leaf apex. Costa cross-section at leaf middle rounded to elliptic, more than 3 times as thick as the adjacent leaf, with 5–6 cells exposed on adaxial surface and about 10 cells exposed on abaxial surface. Leaf margin plane throughout or with some recurvature immediately above leaf base on one or both sides of the leaf. Awn absent throughout. Axillary hairs to 100 µm long, with 5–6 short rectangular, thin and vesicular cells, without a basal brown cell. Rhizoids red brown and monopodially branched, to 20 µm wide at base, smooth to finely verruculose. Stem cross-section round without a central strand, with stereome only gradually differentiated from the somewhat leptodermous, hyaline inner cortical cells,

   Autoicous with perigonia located only a few leaf axils below perichaetia. Inner perichaetial leaves pale to hyaline, erect and markedly shorter than the capsule. Outer perichaetial leaves loosely sheathing capsule, mostly a little longer than the adjacent vegetative leaves, never with awn. Seta to 1 mm long, brown to pale brown, straight and smooth. Urn immersed, erect, symmetrical, broadened from base to the very wide mouth, smooth when dry, to 1.2 mm long, about 1: 1, not strumose. Operculum with only a short apiculus, about 0.2 mm long. Annulus absent or indistinct. Calyptra cucullate and smooth, covering only operculum. Peristome vivid red-brown, to 400 µm long, finely papillose, asymmetrically cribrose but not at all bifid. Suboral exothecial cells thick-walled in 4–6 rows with lumen: wall ratio about 1–2: 1, transversely elongate, to 25 µm wide, about 0.4–0.5: 1. Median exothecial cells very irregular in size and shape, 20–35 µm wide, not in regular vertical rows, quadrate to rectangular or hexagonal, 1–3: 1, moderately thick-walled with lumen: wall ratio about 5: 1. Basal exothecial cells not differentiated. Stomata absent. Spores smooth to finely verruculose, to 18 µm.

Vouchers: Inyo Co.: slopes east of Dragon Peak and north of Golden Trout Lake near Onion Valley, John Muir Wilderness, Inyo National Forest, Norris 46726; Madera Co.: Jackass Creek above Minarets Road, Sierra National Forest, Shevock & Kellman 19700 (determined by Blom): Mariposa Co.: Below Glacier Point Road along Bridalveil Creek, Yosemite National Park, Shevock & Norris 20189 (determined by Blom); Siskiyou Co.: Klamath River at Clear Creek, Norris 10506; Trinity Co.: Highway 36 at North Fork Rattlesnake Creek about 4 miles east of Forest Glen, Norris 23783; Tulare Co.; Mineral King, East Fork Kaweah River, Sequoia National Park, Shevock & O'Brien 15947 (determined by Blom); Tuolumne Co.: South Fork Tuolumne River at Highway 120, Yosemite National Park, Shevock 18473 (determined by Blom); Ventura Co.: Chorro Grande Canyon about 1 mile north of Highway 33, Los Padres National Forest, Norris 55542.

Literature: As Grimmia agassizii Crum and Anderson 1981; Flowers 1973; Koch 1950a, 1958; McGrew 1976; Spjut 1971; Strid 1974. As Grimmia alpicola Bourell 1981; Crum and Anderson 1981; Flowers 1973; Harpel 1980a; Lawton 1971; McGrew 1976; Showers 1982; Toren 1977.

Illustration References: Blom 1998; Bremer 1980a; Crum and Anderson 1981; Flowers 1973; Holmes 1976; Ignatov and Cao 1994; Ignatov and Ignatova 2003; Ireland 1982; Lawton 1971.

Elevation by latitude plot for Schistidium agassizii
   in California