Thallus: placodioid, areolate, lobate at the margins, usually forming rosettes 3-4 cm in diam., sometimes decaying in the center, usually tightly adnate; prothallus: usually absent or vestigial, black, along edges or lobe tips areoles: contiguous to discrete, (0.3-)0.5-1(-1.5) mm wide, irregularly rounded, becoming crenate or short-lobed, thicker than the lobes, scattered to contiguous, convex, often contorted lobes: discrete to slightly overlapping, plane to somewhat convex, mostly 3-5 mm long, 0.7-1.5 mm wide, slightly to moderately sinuous or plicate, not strongly inflated, the tips flattened to slightly convex, often broadened and rather thin (to 0.5-0.7 mm), often crenate-incised, the ultimate segments 0.5-0.8 mm wide upper surface: light to medium yellow or grayish to greenish yellow (in shade becoming paler and grayer, in old herbarium specimens developing a brownish tone), smooth to uneven, sometimes with shallow cracks, usually nitid especially at tips and edges of lobes, emaculate, rarely with weak pruina, edges and tips of lobes smooth (without thallospores), esorediate upper cortex: without dead algal cells, 40-75 µm thick, with cells 4 µm in diam. in K; epinecral layer: 10 µm thick medulla: white, moderately loose, partly with granules insoluble in K, with hyphae c. 3 µm in diam.; algal layer: +continuous lower cortex: blue-green, present only on marginal lobes Apothecia: usually numerous, borne submarginally to several per areole, adnate to broadly sessile, often partly appearing irregularly areole-like and lobed, 0.5-2(-3) mm in diam. disc: usually orange to reddish orange (more yellow or gray in shade, darker and brown when young), plane to convex, usually smooth and at least slightly waxy or shiny, epruinose margin: concolorous with thallus or paler, sometimes the outer part blackened, entire to wavy or coarsely crenate, 0.1-2 mm wide, +level with disc, often becoming excluded, usually at least slightly shiny, either without a parathecial ring:or with a thin, indistinct parathecial ring that is slightly deeper color than the disc amphithecium: present, with a continuous or partially discontinuous algal layer marginally and extending below the hypothecium, with a poorly differentiated medulla (partly with granules insoluble in K), similarly corticate to thallus parathecium: hyaline, with conglutinated hyphae, 15-20 µm thick, poorly differentiated from hypothecium but with the hyphae +periclinally oriented epihymenium: red-brown, densely inspersed with fine granules (soluble in K), usually covered by hyaline, non-inspersed layer, 20-35 µm hymenium: often with yellowish granules (insoluble in K) in some of the paraphyses or asci, (35-)40-65 µm tall; paraphyses: tips: up to 2.5 µm thick, hyaline; subhymenium: pale gray, 30-50 µm thick, without oil droplets; hypothecium: hyaline to pale yellow, 15-50 µm thick, with randomly oriented hyphae asci: clavate, 8-spored ascospores: hyaline, simple, +ellipsoid, 9-12(-15) x (4-)56 µm Pycnidia: sometimes rather numerous; ostioles: reddish or bluish; conidophores: type III of Vobis (1980) conidia: filiform, +curved, 20-25 µm long Spot tests: thallus K-, C-; cortex: P-, KC+ yellow; medulla: KC-, and P- (chemotype 1), P+ orange (chemotype 2) or P+ yellow (chemotype 3) Secondary metabolites: cortex with usnic acid (trace or major), isousnic acid (+trace); medulla with rangiformic acid and related fatty acids (chemotype 1), pannarin plus fatty acids (chemotype 2) or psoromic acid plus fatty acids (chemotype 3). Substrate and ecology: on granite, on +exposed and gently sloping surfaces, among pines World distribution: western North America (mainly in the Sierra Nevada) Sonoran distribution: southern California at 2000-2800 m and Baja California at 3200 m. Notes: Lecanora semitensis was sometimes identified as L. cascadensis (= L. garovaglii ssp. cascadensis), or more often as L. muralis, but can usually be distinguished from both species by the absence of terpenes (and frequent presence of P+ substances in chemotypes 2 and 3), a shinier, epruinose upper surface and usually more orange and nitid apothecia. It also differs from L. muralis in the more convex and plicate lobes and the absence of conical hyphal bundles in the cortex. However, in material of L. sierrae from shaded sites (including several in the Sonoran region), the upper surface is mostly dull and gray tinged, and discs are dull and rather pale and yellowish brown.