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Dicranum scoparium Hedwig [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 ·
LiteratureLawton 1971.
IllustrationsAbramov and Volkova 1998; Ignatov and Ignatova 2003; Lawton 1971.
NotesAlthough attributed to California in the bryological literature, all but one of the California specimens we examined labeled as Dicranum scoparium are actually D. howellii.
BioregionsNW.
VouchersSiskiyou Co.: Granite Creek between Tickner Creek and Blue Granite, Norris 52329.
   

Elevation by latitude plot for Dicranum scoparium
   in California

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