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Dicranum howellii Renauld & Cardot [Dicranaceae]
map of distribution

Plants in yellow green to green cushions or tufts, to 8 cm high, glossy to almost lustreless. Leaves usually at least somewhat falcate secund, occasionally undulate but not crispate when dry, erect spreading when moist, keeled to subtubulose distally, to 8 mm long, 5–8: 1, neither plicate nor fragile, narrowly lanceolate. Median leaf cells smooth, to 12 µm wide, 3–8: 1, in regular rows, linear to rectangular, strongly pitted. Marginal cells more narrow but not otherwise differentiated. Basal cells rectangular, to 20 µm wide, more strongly pitted than median cells. Alar cells well demarcated, often extending to costa, inflated, usually thin walled. Costa percurrent to excurrent in a mostly acute apex, smooth proximally but with 2–4 serrate lamellae on the abaxial surface near its distal end. Costa cross-section with two rather weak stereid bands and with a single layer of guide cells but with no epidermis. Margin plane to erect, serrate at least in distal 1/2, unistratose throughout. Rhizoids white or brown to red brown, to 15 µm wide at base, smooth, mostly dichotomously branched with the ultimate branches strongly curled, arising on stem from immediately below leaf insertion. Stem cross-section homogeneous with no central strand and with even the outer cortical cells rather large, but somewhat pigmented.
    Pseudautoicous with male plants bud-form, in the axils of leaves close to the perichaetia. Perichaetial leaves partially sheathing base of seta, truncate into a short acumen or occasionally acuminate from base to apex. Mostly monosetous with the seta to 30 mm, yellow to red-brown, straight and smooth. Urn inclined to horizontal, arcuate, smooth to very slightly sulcate, to 3.5 mm long, 4–5: 1, not strumose. Operculum rostrate, about as long as urn. Annulus not differentiated. Peristome red-brown, inserted near capsule mouth, to 500 µm long, bi- to trifid near apex, vertically striate proximally but at least somewhat papillose distally. Exothecial cells to 25 µm wide, not in regular vertical rows, quite irregular in size and shape, rectangular 2–4: 1, very thin walled. Spores minutely papillose, to 25 µm.

This is probably the most common Dicranum in most of North America and temperate to cool temperate Eurasia. In California it is found both on tree bases in coastal dune forests and on rocks and tree bases in inland forests. It is quite scarce in the coastal redwoods. In California, this is the only moss with large lanceolate and falcate leaves, and with elongate, pitted median cells combined with enlarged, often pigmented alars.

Mail a correction to Paul Wilson ·
LiteratureBourell 1981; Howe 1896; Kellman 2003; Lawton 1971; Shevock and Toren 2001; Toren 1977. Misapplied as Dicranum scoparium Holmberg 1969; Jamieson 1969; Koch 1950a; Koch and Ikenberry 1954; Lesquereux 1868; Spjut 1971; Watson 1880; Yurky 1995. As Dicranum bonjeanii Holmberg 1969; Koch 1950a, 1951e; Spjut 1971; Yurky 1990.
IllustrationsMalcolm et al. 2009 p. 108; Lawton 1971.
BioregionsCaR, NW, SN.
VouchersButte Co.: about 2 miles northeast of Forbestown, Plumas National Forest, Dillingham 1011 (CAS) and arm of Oroville Lake near Bloomer Hill, Janeway 7745 (UC); Del Norte Co.: Whiskey Lake, Six Rivers National Forest, Norris 83369; Humboldt Co.: Emerald Creek east of Orick, Norris 24591; Mendocino Co.: Eel River about 3 miles south of Piercy, Norris 72142; San Francisco Co.: Mt. Davidson, Shevock 19290; Santa Cruz Co.: Whites Lagoon, Forest of Nisene Marks State Park, Kellman 774 (CAS); Shasta Co.: Soda Creek Road about 3 miles northeast of Highway 5 near Dunsmuir, Shasta-Trinity National Forest, Norris 84783; Siskiyou Co.: Clear Creek below Young's Valley, Norris & Ignatov 74747; Trinity Co.: Hennessy Ridge Road about 1 mile west of eastern border of Six Rivers National Forest, Norris 77269.
   

Elevation by latitude plot for Dicranum howellii
   in California

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