University Herbarium
		University of California, Berkeley

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Plants in cushions or tufts to 2.5 cm high, olive green to brownish-green above but blackening below. Leaves loosely spreading when moist but rather rigidly erect when dry, elliptic lanceolate and broadest below the middle, with broadly acute to obtuse apices, to 3 mm long, 3.5–4.5: 1. Leaves mostly bistratose in the distal 3/4, or with a few unistratose streaks near the costa. Median laminal cells isodiametric with rounded lumens, thick walled with strong corner thickenings, to 10 µm wide, with 1–2 low and unbranched papillae on each surface. Basal marginal cells in a moderately well-demarcated alar cluster, smooth and thin walled, to 20 µm broad, mostly isodiametric. Basal juxtacostal cells smooth, quadrate to very short rectangular, 1–2: 1, with lateral walls thin and not pitted. Margins mostly recurved near the base bu plane in distal 1/3–1/2 of leaf, entire. Costa ending within ten cells of apex, not in an abaxial keel. Costa cross-section about twice as thick as the adjacent lamina, essentially homogeneous or with abaxial cells reduced, mostly 3 cells thick, and 6–10 cells wide along the abaxial perimeter. Lateral axillary hairs to 3 cells and 125 µm long with one basal brown cell and with not distal diameter enlargement of the hair; central axillary hairs more than twice as long with up to 12 cells, none of them offset from leaf insertion. Rhizoids rather densely clustered near base of plant, smooth and very thick-walled, red-brown, to 20 µm in diameter at base, sparingly branched. Stem cross-section pentagonal, with no central strand, with all cells pachydermos and red-brown, and with only minor and gradual enlargement of the cells inwardly.
    Autoicous with perigonia in leaf axils near the perichaetia or on the apices of separate short branches. Perichaetia terminal with bracts somewhat smaller than vegetative leaves. Capsule exserted on a yellow to yellow brown, smooth and erect seta to 0.8 mm in length. Urn stramineous with orange-brown ribs, to 1.5 mm long, about 2: 1, erect, strongly sulcate with eight ribs, lightly to strongly strangulate. Operculum conic-apiculate. Annulus well-defined, revoluble. Exothecial cells at capsule mouth strongly reddened, to 20 µm wide, rounded-isodiametric with very thick walls and strong corner thickenings. Exothecial cells at middle of urn quadrate to very short-rectangular, 1–1.5: 1, to 20 µm broad, very thick walled on ridges of capsule with lumen: wall ratio 0.25–1: 1, thinner walled in valleys of the sulcate capsule. Stomata mostly on proximal 1/2–1/3 of urn, cryptoporous, only partially obscured by subsidiary cells. Subsidiary cells of stomata little differentiated, not raised above the level of the adjacent exothecial cells. Exostome teeth erect to weakly spreading, mostly 8 but occasionally splitting with age, pale to almost white, to 300 µm long, ridged-striate below but somewhat papillose above. Endostome segments mostly 8, occasionally absent, as long as exostome, longitudinally striate, arising from only one row of cells. Calyptra less than twice as long as broad, campanulate but ittle plicate, sparsely covered with smooth to sparingly papillose hairs. Spores to 15 µm, rather coarsely papillose.

Elevation by latitude plot for Orthotrichum hallii
   in California

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