Dicranella heteromalla

   Plants to 20 mm high, in rather dense turfs, green to yellow-green. Leaves falcate-secund and spirally inserted without obvious ranking, to 4 mm long, more than 10: 1, keeled throughout with base closely enfolding the stem, but with this base poorly differentiated from the limb, gradually contracted to the blunt and channeled subula. Leaves erect and little distorted when dry, erect-spreading when moist. Lamina cells unistratose and smooth throughout. Alar cells quadrate in a moderately well-defined cluster but not at all inflated. Juxtacostal cells of the leaf base in regular rows, to 10 µm broad, 3–6: 1, rectangular with uniformly thick. Juxtamarginal cells of base above the alar region more narrow than adjacent internal cells. Median cells to 12 µm wide, about 6–8: 1, porose and thick-walled with lumen: wall ratio 3–4: 1 but with ends walls strongly pachydermous and oblique relative to long axis of leaf. Subula with lamina 1–3 cells wide but with distal portion narrowing to extinction, with those cells short rectangular, to 10 µm broad, 3–4: 1, arranged in regular rows, thick-walled with lumen: wall ratio 2–3: 1. Abaxial cells of costa narrowly linear, to 8 µm wide, more than 10: 1; adaxial cells very irregular in length, in regular rows, rectangular, 2–5: 1, similar in width to adjacent laminal cells. Costa about 1/5 of leaf base but filling all of subula, short excurrent. Costa cross-section at mid-leaf crescentic, 2.5–3: 1 with a well-defined single layer of guide cells, with strong abaxial and adaxial stereid bands and with well-demarcated dorsal and ventral epidermises. Margin plane below, becoming erect to incurved above, serrulate above the middle, sometimes dentate near apex. Rhizoids very sparingly produced, to 10 µm in diameter at insertion, pale to red-brown, mostly on abaxial leaf bases on extreme base of plant. Axillary hairs to 150 µm long, 5–6 cells, with 1–2 basal brownish cells and with all cells thin-walled and of uniform diameter throughout. Stem cross-section round to rounded pentagonal, with poorly defined central strand, very thin-walled inner cortical cells, and with only one layer of thicker walled smaller cells in the outer cortex.

   Dioicous with male and female plants similar. Perichaetial leaves larger and more sheathing than the vegetative leaves. Seta to 20 mm, yellow to brown, straight, smooth. Capsule mostly curved and asymmetrical with the mouth oblique and with the urn short cylindric, to 1.5 mm long, about 2: 1, markedly sulcate and strangulate, sometimes slightly strumose. Annulus absent or of only 1–2 rows of cells. Calyptra cucullate, glabrous, covering about 1/2–2/3 of urn. Operculum inclined, rostrate, 2/3 or more of urn length. Peristome reddish-brown, 400–500 µm long, striate below but sparingly reticulate papillose above, bifid to below middle. Exothecial cells irregular in size and shape, rectangular with oblique end-walls, not in regular rows, to 15 µm wide, 4–7: 1, thin-walled throughout. Suboral exothecial cells short rectangular to quadrate, reddened, to 25 µm wide, very thick-walled with lumen almost obscured by wall thickening. Stomata not seen. Spores spherical, to 15 µm, smooth.

Vouchers: Del Norte Co.: trail between Requa and False Klamath Cove, Redwood National Park, Norris 24029 and Sanger Lake, Six Rivers National Forest, Norris 7773 & 7775; Glenn Co.: Cottonwood Glade east of Plaskett Meadows, Mendocino National Forest, Norris 47961; Humboldt Co.: Goose Creek, Norris 56531; Marin Co.: South Novato, Jenkinson s.n. (UC); Mendocino Co.: east of Highway 1 just south of Caspar, Pygmy Cypress Forest, Tavares & Sharsmith 732 (UC); San Francisco Co.: Mt. Davidson, Shevock 18928; Santa Cruz Co.: Waddell Creek near Redwoods Camp 2, Big Basin Redwoods State Park, Kellman 782 (CAS); Sonoma Co.: Bodega Marine Laboratory, Norris 103450.

Literature: Crum and Anderson 1981; Howe 1897; Jamieson 1969; Kellman 2003; Koch 1950a; Koch and Ikenberry 1954; Lawton 1971; Shevock and Toren 2001; Yurky 1990, 1995. As Dicranum heteromallum Lesquereux 1868; Watson 1880.

Illustration References: Malcolm et al. 2009 p. 105; Crum and Anderson 1981; Ignatov and Ignatova 2003; Ireland 1982; Lawton 1971; Smith 1978.

Elevation by latitude plot for Dicranella heteromalla
   in California