Dichodontium pellucidum, Coroll. Bryol. Eur. 12. 1856 -- Bryum flavescens Dicks. ex With. Syst. Arr. Brit. Pl. ed. 4, 3: 813. 1801-- Dichodontium flavescens (With.) Lindb.

   Plants in yellow green to dark green loose cushions to 4 cm high, almost lustreless. Leaves mostly rather distantly inserted, strongly crispate when dry, spreading to erect-spreading when moist, not at all secund, somewhat inrolled when dry but not keeled, to 4 mm long, 4–5: 1, broadest at extreme base, neither plicate nor fragile, lanceolate to oblong- lanceolate. Leaf lamina unistratose throughout with median cells quadrate with rounded lumens, to 14 µm wide near the costa but gradually more narrow toward margins, high mammillose to nearly smooth, in regular rows, not at all pitted, often somewhat collenchymatous. Basal cells pellucid but rather thick walled, rectangular, to 6: l. Alar cells not differentiated. Costa filling about 1/6 of leaf at base, tapering and ending within a few cells of the obtuse to broadly acute apex. Costa cross-section with two strong stereid bands; with guide cells well demarcated and with both epidermises well differentiated and chlorophyllose. Margin recurved at least at base or near leaf middle, entire below but serrulate to denticulate near apex, unistratose throughout. Rhizoids brown to red brown, to 15 µm wide at base, smooth, sparingly branched, arising on stem immediately below leaf insertion. Stem cross-section with small central strand, with, leptodermous interior cells and with 2–3 layers of small pachydermous outer cortical cells.

   Dioicous with male and female plants similar. Perigonia terminal. Perichaetial leaves spreading, similar to adjacent vegetative leaves. Consistently monosetous with the seta to 20 mm, yellow, straight and smooth, thickened distally near capsule. Urn erect and symmetrical or very much arcuate, short cylindrical, to 1.5 mm long, about 2: 1, not at all sulcate or strumose. Operculum rostrate, about as long as urn. Annulus essentially undifferentiated. Peristome red-brown, inserted at capsule mouth, or somewhat above it on a short basal membrane, to 500 µm long, divided to or below the middle, vertically low striate but occasionally papillose distally. Exothecial cells to 25 µm wide, in regular vertical rows, quite irregular in size and shape, rectangular 0.5–3: 1, very thick walled with lumen/wall ratio about 2: 1. Spores to 15 µm, lightly papillose.

Vouchers: Alpine Co.: Silver Creek at Carson River, Toiyabe National Forest, Norris 78978; Fresno Co.: Avalanche Creek at Cedar Grove, South Fork Kings River, Kings Canyon National Park, Shevock 13770; Humboldt Co.: Forest Road 5E21 at East Fork about 5 air miles north of Mad River, Six Rivers National Forest, Norris 83887; Lake Co.: beyond Towhead Flat, Mt. Sanhedrin, Mendocino National Forest, Toren 5077 (CAS); Riverside Co.: Middle Spring along Devils Slide Trail, San Jacinto Mountains, San Bernardino National Forest, Harpel 941 (pers. herb.); Shasta Co.: Highway 299 north side of Haynes Flat about 3 miles west of Burney, Norris 68563: Siskiyou Co.: Shadow Creek at Callahan about 6 miles northeast of Cecilville, Klamath National Forest, Norris 70552.

Literature: Bourell 1981; Crum and Anderson 1981; Harpel 1980a; Harthill et al. 1979; Holmberg 1969; Jamieson 1969; Kellman 2003; Koch 1950a, 1951e; Koch and Ikenberry 1954; Long 1978; Showers 1982; Spjut 1971; Strid 1974; Tan and Schofield 1980; Thomson and Ketchledge 1958; Toren 1977.

Illustration References: Malcolm et al. 2009 p. 101; Crum and Anderson 1981; Flowers 1973; Ignatov and Ignatova 2003; Ireland 1982; Lawton 1971; Smith 1978; Werner 2002.

Elevation by latitude plot for Dichodontium pellucidum
   in California