Plants with a persistent protonema whose upright axes almost obscure the tiny, essentially stemless gametophores. Plants with leaves spreading when moist, somewhat twisted when dry, scattered among the protonematal strands, pale to sordid green. Leaves to 1 mm long, narrowly lanceolate to ligulate-lanceolate, 6–8: 1, scale-like below but grading imperceptibly to the perichaetial leaves. Leaf apex evenly acute to slightly acuminate. Lamina unistratose throughout, with plane margins and no keeling. Median and distal cells only gradually differentiated from the basal cells. Median laminal cells to 30 µm broad, rectangular with transverse end-walls, 2.5–4: 1, evenly rather thick-walled without corner thickenings. Basal cells shorter and somewhat thinner walled but otherwise undifferentiated. Costa completely absent or with a few celled central bistratosity in the central, distal portion of the leaf apex. Margin coarsely serrate to dentate with some of the teeth made up of all or most of a cell, and with the larger teeth recurved in the plane of the leaf. Rhizoids hyaline to pale brown, smooth and sparingly branched, to 15 µm wide at insertion.
Autoicous with male branches inserted near stem base, often fragile and lost by the time of capsule maturity. Perichaetial leaves poorly differentiated from associated vegetative leaves. Seta inconspicuous even in the young sporophyte, smooth and straight but concealed by the larger capsuled. Capsule red-brown when mature, globose, to 0.5 mm in diameter, apiculate at apex but without a differentiated operculum. Peristome absent. Exothecial cells quadrate to short rectangular, thin-walled, to 50 µm wide; in cross-section unistratose with the outer wall rather thick but with the inner wall hyaline and thin, tardily collapsing. Spores 45–60 µm, spherical to elliptic, nearly smooth.
|Literature||Brandegee 1891; Bryan and Anderson 1957; Crum and Anderson 1981; Kellman 2003; Koch 1950a; Lesquereux 1868; Shevock and Toren 2001; Toren 1977; Watson 1880. As Ephemerum minutissimum Crum 1957. As Ephemerum serratum var. angustifolium Lesquereux and James 1884.|
|Illustrations||Malcolm et al. 2009 p. 128; Bryan and Anderson 1957; Crum and Anderson 1981; Ignatov and Ignatova 2003; Ireland 1982; Smith 1978.|
|Bioregions||CaR, CW, NW, SN.|
|Vouchers||Lake Co.: near Hell's Peak, Toren 1476 (CAS) [determined by Bryan] and Highway 53 about 1 mile south of Highway 20, Norris 47709; Madera Co.: near Eastman Lake, Shevock 14933a; San Francisco Co.: Mission Dolores, San Francisco, Bolander s.n. (DUKE); Santa Barbara Co.: Santa Inez Mountains about 4 miles south of Solvang, Norris 68160; Santa Cruz Co.: University of California, Santa Cruz, Norris 55679; Shasta Co.: Highway 299 about 9 miles east of Bella Vista, Norris 47595, 47596, & 47598; Tulare Co.: Coffee Campground off of Highway 190, Tule River Canyon, Sequoia National Forest, Norris 87046.|