Thallus dispersed-verrucose to verru-culose, granular in some, white, yellowish white, or yellowish gray; sometimes with white fibrous hypothallus. Apothecia sessile or constricted at base, to 1.8 mm broad; margin smooth to verruculose or verrucose, prominent; margin with large crystals, rarely absent; cortex gelatinous, inspersed, distinct, 20-25 μm laterally, 35-50 μm basally; disk dark brown to brown-black or black; epihymenium lacking granules, pigmented brown to greenish or olive; spores broadly ellipsoid, 8-15.5 x 5.5-7.5 μm.

Contents: atranorin, gangaleoidin, ± ca-lifornin (Brodo 1984b).

This species grows on noncalcareous to slightly calcareous rocks in shade of ravines and cliffs. It is known from hemiboreal North America and from one locality in Japan. In North America it ranges from Alaska to New Brunswick and south to New Mexico and New England.

Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Thallus: crustose, dispersed-verrucose to verruculose; prothallus: white areoles: thin or thick, glossy, ecorticate surface: smooth, whitish gray to yellowish gray, epruinose, with an indistinct margin, esorediate Apothecia: sessile, 0.6-1.8 mm in diam., lecanorine disc: black to brown-black, even when wet, plane, epruinose margin: concolorous with thallus, inner part often black, thin or thick, persistent, prominent, smooth, entire or verruculose, without a parathecial ring amphithecium: present, with numerous algal cells, with large crystals insoluble in K, corticate; cortex: hyaline, distinct, uniform or basally thickened, gelatinous or sometimes not, interspersed with small crystals, 15-25 µm thick laterally, 25-50 µm thick basally parathecium: hyaline, containing crystals soluble in K epihymenium: brown to greenish black, not turning green in K, without crystals hymenium: hyaline, clear; paraphyses: not thickened or slightly thickened apically, olivaceous; subhymenium: hyaline, 15-20 µm thick; hypothecium: hyaline or yellow-green, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, broadly ellipsoid to subspherical, 9-15 x 5.5-8 µm; wall: less than 1 µm thick Pycnidia: not seen Spot tests: thallus and apothecial margin K+ yellow, C-, KC-, P+ pale orange Secondary metabolites: atranorin (major), chloroatranorin (minor), gangaleoidin (major), and norgangaleoidin (minor). Substrate and ecology: on exposed siliceous rocks in montane areas World distribution: circumboreal, known from Asia and North America Sonoran distribution: Arizona. Notes: Lecanora argentea is very rare in the study area and is only known from a single locality in Arizona (Apache Co.). Brodo (1984) mentioned an additional collection from high altitudes in nearby New Mexico. This saxicolous species is characterized by black apothecial discs and the presence of the gangaleoidin chemosyndrome. It is similar to L. gangaleoides but differs in having a different epihymenium (Lumbsch 1992).