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Didymodon norrisii Zander [Pottiaceae]
map of distribution

Typescript last altered 17 June 2012
   Didymodon norrisii Zander, Bryologist 102: 112. Figs 1–11. 1999.

Plant erect or decumbent in crowded populations, red brown, often almost black. Stems to 1.5 cm tall, spreading to almost squarrose when moist, erect-spreading when dry, not at all keeled. Leaves ovate to ovate-lanceolate, smallest near base, gradually larger above but uniform in shape throughout. Leaves appressed when dry; reflexed-spreading from a weakly sheathing basal collar when moist. Leaves channeled along costa in distal region; broadly concave in at least the proximal ½, about 1.5 mm long and 0.8 mm wide, margins recurved only near base, not decurrent, with margins minutely and evenly crenulate. Costa smooth and dark, with obvious boundaries except near apex where there may be short spurs, with elongate cells in 4–6 rows on dorsal face, percurrent or nearly so. Costa cross-section elliptical, about 1.5: 1, with differentiated abaxial and adaxial epidermises, with a group of 5–8 guide cells and with mostly a single abaxial stereid band. Median laminal cells isodiametric, to 14 m in diameter, rather thin-walled without significant corner thickenings and with angular lumens, nearly smooth but with a few low papillae over the lumen, especially in distal, marginal portion of leaf. Basal laminal cells mostly similar to median cells or somewhat more elongate-rectangular, 1–2.5: 1, mostly smooth, with longitudinal and transverse walls with lumen: wall ratio about 1: 1. Stem rounded-triangular in cross-section, with outer cortical cells resembling a hyaloderm and surrounding a hyaline and thin-walled central area with a central strand. Rhizoids red-brown, to 25 m at insertion, mostly placed on decumbent portions of stem. Axillary hairs 4–6 cells in length with a single lightly pigmented basal brown cell uniseriate and evenly cylindric, to 100 m long, with diameter about 12 m, not expanded distally or proximally. Poorly developed tips of stems fragile and functioning in asexual reproduction. KOH brick-red.
    Dioicous with inner perichaetial leaves shorter and relatively more narrow than vegetative leaves, acute to almost subulate at apex, costate and entire, with cells all smooth and thick-walled. Seta yellow but reddened with age, about 12 mm long. Calyptra cucullate, smooth and glabrous. Capsule erect, stegocarpous, to 2 mm long. Peristome greatly reduced or absent. Spores brown and spherical, about 25 m in diameter, and finely papillose.
    Didymodon norrisii is to be expected at middle elevations in areas of abundant flat rocks that by impeding drainage leave areas that remain moist after the rocks show some seasonal desiccation. In such habitats, recognition is made rather easy by the deep red to almost black color of the gametophytes. The concavity of the leaf of D. norrisii combines with the restriction of significant marginal recurvature to a small area defined by the leaf base up to the point at which the leaf is at its broadest. From that point of the leaf's greatest width the line to the leaf tip is almost a straight line. Under the microscope, the crenulate leaf margins allow for confirmation of identification.

Mail a correction to Paul Wilson ·
LiteratureKellman 2003; Zander 1999.
IllustrationsMalcolm et al. 2009 p. 125; Zander 1999.
BioregionsCaR, CW, NW, SN.
VouchersContra Costa Co.: near Castle Rocks, Mt. Diablo State Park, Shevock & Ertter 20347; Humboldt Co.: near Kneeland, Norris 7884 (BUF, UC); Lake Co.: Manning Creek, Highway 175 about 4 miles west of Lakeport, Toren, Bourell, Dearing, & Shevock 6940 (CAS) and Toren 7402 (CAS), Hell's Peak near Blue Lakes, Toren 636 (CAS), The Slides west of Lake Pillsbury, Mendocino National Forest, Toren 7534 (CAS) [determined by Zander]; Shevock, Ertter, Toren, & Dearing 19488, and Bartlett Mountain Road at High Valley Ridge, Mendocino National Forest, Norris 10606; Madera Co.: Forest Highway 81 between Fish Creek and Slide Creek, Sierra National Forest, Shevock & Norris 19785; Nevada Co.: road to Downieville about 3 miles from Nevada City, Norris 67384; Santa Cruz Co.: Eagle Rock Lookout Tower near Bonny Doon, Kellman 890 (CAS); Tehama Co.: Hogback Road about 4 miles east of Highway 99, Shevock & Ertter 22251; Tulare Co.: near Brush Creek along Kern River, Sequoia National Forest, Toren 7936 (CAS); Tuolumne Co.: Highway 108 east of Long Barn, 6.1 miles east of Mi-Wok Ranger Station, Stanislaus National Forest, Shevock 18586 (determined by Toren).
   

Elevation by latitude plot for Didymodon norrisii
   in California

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