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Acaulon rufescens A. Jaeger [Pottiaceae]


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Database links

UC Specimens in the University and Jepson Herbaria Public Portal

Specimens of Acaulon rufescens in the Consortium of North American Bryophyte Herbaria portal (CNABH)

Acaulon rufescens, Musci Cleist. p. 19, 1869. -- Acaulon muticum var. rufescens (Jaeg.) Crum, Bryologist 72: 240. 1969.

   Plants glossy, yellow-green to golden, mostly scattered or somewhat gregarious and bulbiform. Leafy stems to 2 mm high with the stem essentially obsolete. Leaves concave, not or inconspicuously keeled, erect and enclosing the capsules, not contorted when dry. Leaves ovate to very short-elliptic, 1.5–2: 1, scale-like below but grading imperceptibly to the perichaetial leaves which may exceed 1.5 mm in length. Lamina unistratose throughout. Median and distal cells only gradually differentiated from the basal cells. Median laminal cells elliptic to hexagonal, to 12 µm broad, 1.5–2: 1, with elliptic lumens and without defined corner thickenings. Basal cells rectangular with straight lateral walls, to 14 µm broad, 3–4: 1, smooth, moderately thick-walled, unistratose throughout. Costa narrow from its base to its percurrent to short excurrent, reflexed apex. Costa cross-section at mid-leaf about twice at wide as thick, only slightly thicker than the adjacent lamina, with only a slight hint of an abaxial stereid band, otherwise essentially homogeneous. Margin crenulate-serrulate or occasionally nearly entire, often with irregular dentations near apex, recurved to well above the middle. Axillary hairs pale brown and rather thick-walled, to 120 µm long, 3-celled, with no basal brown cells. Rhizoids hyaline, smooth to minutely verruculose, sparingly branched, to 20 µm wide at insertion.

   Dioicous with the male plants so small as rarely to be seen. Perichaetial leaves larger than, but only gradually demarcated from the vegetative leaves. Seta mostly less than 0.5 mm long, straight. Capsule globose, to 0.5 mm in diameter, apiculate at apex but without a differentiated operculum. Calyptra mitrate, covering only the apiculus. Peristome absent. Exothecial cells mostly short rectangular, 2–3: 1, with curved lateral walls, 15–20 µm wide. Stomates phaneroporous, restricted to base of urn. Spores 30–50 µm, spherical to very short elliptic, nearly smooth.






Vouchers: Alameda Co.: Brushy Peak northeast of Livermore, Norris 87165; Humboldt Co.: Highway 36 about 2 miles east of Carlotta, Norris 48206; Lake Co.: Indian Valley Lake near dam, Norris 67538; Monterey Co.: cemetery on Lockwood Road east of Alamo Air Strip, Hunter-Liggett Military Reservation, Norris 87322; Santa Barbara Co.: El Capitan State Beach west of Santa Barbara, Norris 68146; Sierra Co.: near Alleghany about 4 miles from Highway 49, Tahoe National Forest, Norris 67413; Trinity Co.: Trinity River about 4 miles east of Del Loma, Shasta-Trinity National Forest, Norris 72793.

Literature: Shevock and Toren 2001. As Acaulon muticum Howe 1896; Kellman 2003; Koch 1950a; Toren 1977; Yurky 1995. As Acaulon muticum var. rufescens Crum and Anderson 1981. As Sphaerangium muticum Brandegee 1891; Lesquereux 1868; Lesquereux and James 1884; Watson 1880.

Geographic subdivisions for
Acaulon rufescens: CaR, CW, GV, NW, SN.
map of distribution

Illustration References: Malcolm et al. 2009 p. 113; Crum and Anderson 1981; Smith 1978. As Acaulon muticum Ignatov and Ignatova 2003.

P. L. Redfern 27039

No expert verified images found for Acaulon rufescens.

Elevation by latitude plot for Acaulon rufescens
   in California