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Bryum muehlenbeckii Bruch & W. P. Schimper [Bryaceae]
map of distribution

Plants erect in lustreless green to reddish green tufts with red stems, to 3 cm high. Leaves uniformly spaced along stem, not comose distally. Leaves only slightly concave-keeled, elliptic-lanceolate, broadest near leaf middle, bluntly rounded at apex, to 2.5 mm long, about 3–3.5: 1, erect-spreading when moist, not much changed when dry, not plicate. Median laminal cells rhomboidal to hexagonal (3–4: 1) with rather thick walls (lumen: wall ratio 4–10: 1), completely smooth, not pitted, to 15 µm wide. Basal and alar cells markedly shorter and broader than median cells. Margins not decurrent, mostly erect but with inconspicuous recurvature near base, mostly entire but with low serrulations distally. Limbidium poorly demarcated, of 1–3 rows of more narrow and rectangular cells, unistratose throughout. Costa reddened, especially at base, percurrent on most leaves but often ending in a minute recurved apiculus. Costa elliptic (about 2:1) in cross-section with a strongly developed abaxial stereid band and with two abaxial layers of non-stereidal cells. Axillary hairs to 70 µm long, with a pale brown basal cell and two distal cells which taper to the end. Micronemata absent. Macronemata red-brown, high papillose, to 35 µm wide at insertion, surrounding an isodiametric macronematal area. Stem cross-section round but ribbed by costa bases, with a strongly demarcated central strand, with hyaline and leptodermous inner corticals abruptly transitting to 2–3 layers of pachydermous, red brown outer cortical cells, but without an hyaloderm. Gemmae absent from our specimens. Dioicous with male plants somewhat smaller than females. Perichaetial leaves similar but smaller relative to the vegetative leaves. Seta light-brown to brown, smooth, erect but geniculate distally, to 15 mm long. Urn with neck comprising about 1/3 of capsule length, to 3.5 mm long, cylindric, 3.5–4.5: 1, strongly inclined to pendent, neither sulcate nor strumose. Operculum short conic. Annulus present, falling in fragments. Exothecial cells at capsule mouth to 30 µm broad, transversely elongate in several rows. Exothecial cells at middle of urn irregularly rectangular, 2–5: 1, to 40 µm broad, in regular rows, evenly thick walled with lumen: wall ratio 2–4: 1. Stomates restricted to neck of capsule, not raised on pustules, elongate. Exostome yellow-brown, to 350 µm long, obviously shouldered, finely punctate-papillose throughout. Endostome with basal membrane constituting more than 1/2 of total length of endostome. Segments smooth, as long as exostome, rather narrowly perforated along keel with cilia 2–3, nodose. Calyptra cucullate, mostly shed before capsule maturity. Spores to 15 µm, almost smooth to very finely papillose.

Mail a correction to Paul Wilson ·
LiteratureCrum and Anderson 1981; Holmberg 1969; Koch 1950a; McGrew 1976; Showers 1982; Spence 1988a; Toren 1977.
IllustrationsCrum and Anderson 1981; Ireland 1982; Lawton 1971; Smith 1978.
NotesNeeds update to Imbribryum muehlenbeckii (Bruch & Schimper) Pedersen.
BioregionsCaR, NW, SN.
VouchersMariposa Co.: Highway 49 about 3.3 miles southeast of Mariposa at junction with Highway 140, Shevock 15242; Shasta Co.: Highway at Shasta College north of Redding, Norris 57789; Tulare Co.: below Paradise Ridge overlooking the Middle Fork Kaweah River, Sequoia National Park, Shevock 14633.
   

Elevation by latitude plot for Bryum muehlenbeckii
   in California

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