Eur. N. Amer. Bryin. 2: 232. 1897. -- Grimmia platyphylla Mitt., J. Linn. Soc. Bot. 8: 20. 1864.
Grimmia alpicola var. latifolia (Zett.) Möll., Bot. Not. 1907: 143. 1907. -- Schistidium alpicola var. latifolia (Zett.) Limpr., Laubm. Deutschl. 1: 709. 1889.
Plants to 2.5 cm high, in dark green cushions, opaque-green to nearly black below. Leaves lightly imbricate when dry, erect-spreading when moist, somewhat concave and keeled, to 1.5 mm long without an awn either on perichaetial or vegetative leaves, elliptic-lanceolate and broadest near leaf middle, 2.5–3: 1. Median leaf cells in regular longitudinal rows, bistratose in up to 5 rows at margin and often with bistratose streaks internally, smooth, to 8 µm wide, isodiametric with lumens irregular and with distinct corner thickenings; thick-walled with lumen: wall ratio about 4: 1. Marginal cells quadrate, similar in size and shape to median cells. Basal juxtacostal cells rectangular and rather thin-walled, to 5: 1, to 10 µm wide, with lateral walls straight. Cells of alar region to 8 µm wide, quadrate with rounded lumens, with lumen: wall ratio 3–4: 1; little different from more distal laminal cells. Costa filling less than 1/10 of immediate leaf base, not tapered above, percurrent to shortly excurrent. Costa cross-section at leaf middle rounded to elliptic, with 3–4 cells exposed on adaxial surface and 8–10 cells exposed on abaxial surface. Margin inconspicuously recurved with that recurvature restricted to distal 1/2 of leaf. Axillary hairs to 600 µm long, with more than 10 rectangular, thin and vesicular cells, without a basal brown cell. Rhizoids pale-brown and monopodially branched, to 35 µm wide at base, smooth. Stem cross-section round with a prominent central strand, with stereome well- differentiated from the somewhat leptodermous, hyaline inner cortical cells,
Autoicous with perigonia located only a few leaf axils below perichaetia. Perichaetial leaves loosely sheathing capsule, mostly 1.5–2 times as long as adjacent vegetative leaves with awn consistently absent. Seta to 0.5 mm long, yellow to pale brown, straight and smooth. Urn immersed, erect, symmetrical, short-cylindric, to 1.2: 1 when operculate, smooth when dry, to 1.2 mm long, not strumose. Operculum with only a short apiculus, about 0.2 mm long. Annulus absent or indistinct. Calyptra mitrate, lacerate basally, covering only operculum Peristome erect and strongly cribrose, vividly red-brown, to 500 µm long, finely vertically to irregularly striate. Suboral exothecial cells strongly reddened, rather thick-walled, quadrate, to 20 µm wide. Median exothecial cells somewhat irregular in size and shape, to 30 µm wide, in rather regular vertical rows, quadrate to rectangular 1–3: 1, with lumen: wall ratio about 5: 1. Basal exothecial cells somewhat longer than median ones but with difference gradual. Stomata absent or sparingly produced. phaneroporous, restricted to base of urn. Spores smooth, to 15 µm.