University Herbarium
		University of California, Berkeley

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Plants erect in olive-green to brown wefts or cusions, to 10 cm high. Lower leaves scalelike, loosely appressed and distant; upper leaves oblong lanceolate to lanceolate or linear-lanceolate with acute to acuminate apices, to 4 mm long, 3–8: 1, erect spreading when moist but somewhat twisted around stem when dry, keeled distally. Median laminal cells isodiametric with rounded lumens, mostly with prominent trigones, to 15 µm wide, strongly unipapillose on both surfaces. Basal and alar cells mostly enlarged and thin-walled, to 20 µm in diameter, round to very short elliptical. Margins recurved from base to above the middle, dentate at least in distal 1/2, short decurrent. Costa ending within about ten cells of apex, usually flexuose distally. Costa cross-section with two strong stereid bands and a single layer of guide cells, usually with both epidermises well-demarcated. Axillary hairs 3–4 cells long, to 35 µm, with one basal brown cell, not offset from leaf insertion. Rhizoids to 14 µm in diameter at insertion, lightly to strongly papillose, densely inserted at least near base of plant, red-brown, repeatedly branched, surrounding a macronematal area which is only 1.5–2 times as long as broad. Stem cross-section rounded pentagonal with a well-defined central strand, leptodermous inner corticals and several layers of strongly pachydermous, red brown outer cortical cells. Multicellular gemmae occasionally present, borne in globose clusters and borne singly along the elongate and otherwise naked gemmaphore, small and leaflike.
    Dioicous with male plants somewhat smaller than females, bearing terminal perigonia. Perichaetia terminal with bracts somewhat smaller than vegetative leaves. Seta yellow to yellow brown, smooth, erect, to 40 mm long. Urn to 3.5 mm long, about 3: 1, inclined to almost horizontal, strongly sulcate, not at all strumose. Operculum short conic, 1/4–1/5 as long as the urn. Annulus well-defined, revoluble. Exothecial cells at capsule mouth to 8 µm broad, isodiametric with rounded lumens in up to 6 rows. Exothecial cells at middle of urn rectangular, 2–4: 1, to 12 µm broad, in regular rows, rather thick walled on ridges of capsule with lumen: wall ratio 2–1: 1, thinner walled in valleys of the sulcate capsule. Exostome pale yellow to yellow brown, to 400 µm long, evenly tapered to the narrow apex, with high ventral and lateral trabeculae, finely papillose with papillae in close set horizontal rows. Endostome segments arising from a high basal membrane, lightly papillose, about as long as exostome, open along keel with 2–3, nodulose cilia. Calyptra cucullate, smooth. Spores to 14 µm, smooth or nearly so.

Elevation by latitude plot for Aulacomnium palustre
   in California

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