Plants erect in glaucous green to yellow green wefts. to 10 cm high. Leaves ovate to ovate lanceolate with acute apices, to 2 mm long, about 3: 1, erect spreading to imbricate when moist, little changed upon drying, plicate near base. Median laminal cells oblong to long rectangular, 3–8: 1, prorate at the proximal ends of most of the cells and sometimes prorate also at the distal ends, moderately thick walled but without pitting, to 10 µm wide. Basal and alar cells shorter and broader than median cells, usually prorate only near the margins. Margins decurrent, recurved at least near base with recurvature sometimes extending above the middle, serrate in the distal 3/4 with at least some of the teeth geminate. Costa percurrent to very short excurrent. Axillary hairs to 5 cells long, to 150 µm, with one basal brown cell, not offset from leaf insertion. Rhizoids dense at least near base of plant, smooth, red-brown, repeatedly branched, surrounding a distinctive macronematal area. Stem cross-section rounded pentagonal with a central strand, leptodermous inner corticals, several layers of moderately pachydermous, red brown outer cortical cells, and with a single hyaloderm layer.
Dioicous with male plants somewhat smaller than females, bearing terminal discoid perigonia with squarrose-spreading bracts. Perichaetia terminal with bracts similar to but somewhat larger than vegetative leaves. Seta yellow to yellow brown, smooth, erect, to 50 mm long. Urn to 2.5 mm long, nearly spherical, inclined and sulcate, not at all strumose. Operculum short conic. Annulus absent. Exothecial cells at capsule mouth to 15 µm broad, isodiametric with rounded lumens in up to 8 rows. Exothecial cells at middle of urn rectangular, to 5:1, to 15 µm broad, not in regular rows, very thick walled on ridges of capsule with lumen:wall ratio 0.25–1: 1, thinner walled in valleys of the sulcate capsule. Exostome dark brown to red brown, to 400 µm long, undivided, densely to rather remotely papillose. Endostome segments arising from a high basal membrane, lightly papillose, about as long as exostome, irregularly open along keel with several abortive or rather short cilia. Calyptra mitrate, plicate. Spores reniform, to 30 µm, densely papillose.
This is a plant of very broad distribution in suitably wet habitats throughout warm temperate to arctic areas of North America, Eurasia and North Africa. In California, it is primarily restricted to such ruderal habitats as seepages along roadbluffs. In more undisturbed habitats such as bogs and swamps it is replaced by P. americana, a plant distinguished by frequent axillary, caducous and microphyllous branchlets, and by remotely to strongly pentastichous leaves which become quite contorted when dry.
|Literature||Bourell 1981; Cooke 1941; Coville 1893; Crum and Anderson 1981; Dismier 1911; Flowers 1973; Harpel 1980a; Harthill et al. 1979; Holmberg 1969; Kellman 2003; Koch 1950a, 1951e, 1958; Koch and Ikenberry 1954; Lawton 1971; Long 1978; McGrew 1976; Showers 1982; Spjut 1971; Strid 1974; Toren 1977; Yurky 1990, 1995. As Bartramia fontana Lesquereux 1868; Watson 1880. As Philonotis calcarea forma occidentalis Koch 1950a.|
|Illustrations||Allen 2002; Crum and Anderson 1981; Flowers 1973; Ignatov and Ignatova 2003; Ireland 1982; Koponen et al. 1995; Lawton 1971; Smith 1978.|
|Bioregions||CaR, CW, MP, NW, SN, SNE, SW.|
|Vouchers||Fresno Co.: Forest Road 10S66 above Bear Creek, Sierra National Forest, Shevock & Bourell 14014; Humboldt Co.: shore of Snow Camp Lake, Norris 50381; Marin Co.: Olema, Jepson 66 (UC); Placer Co.: North Fork Campground near Emigrant Gap, Tahoe National Forest, Norris 88049; Riverside Co.: Dark Canyon, San Jacinto Mountains, San Bernardino National Forest, Harpel 79 (pers. herb.); Santa Cruz Co.: Slippery Rock Meadow, Big Basin Redwoods State Park, Kellman 698 (CAS).|