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

Thallus: crustose, warted-areolate, distinct only around apothecia, with an ash-gray to dark gray prothallus between the areoles areoles: ±isodiametric in outline, sometimes incised or crenulate, 0.15-0.35 mm in diam., weakly to moderately convex, ecorticate but sometimes with a loose unorganised alga-free layer of various hyphae surface: yellowish beige to ochre, dull, esorediate Apothecia: rounded or irregular, rarely flexuose, single to densely crowded, sessile with a constricted base, 0.30.6(-0.8) mm in diam. disc: beige to orange-brown, often more or less olivaceous, flat to weakly, rarely moderately convex, white pruinose at least when wet, rarely epruinose, dull or slightly glossy margin: weakly to strongly prominent when young, persistent, more or less granular-knobby, dull, concolorous with thallus or slightly lighter, without a parathecial ring amphithecium: present, with an algal layer, laterally 75-120 µm, basally 75-125 µm wide, medulla with irregularly entangled, short-celled hyphae with lumina c. 1-1.5(-2) µm wide, corticate; cortex: hyaline within, outer part with granules (soluble in K) like in the epihymenium, strongly gelatinized, anticlinally arranged hyphae with lumina of (1-)1.5-2.5 µm, 5-15 µm wide above, 25-65 µm near base parathecium: absent or composed of branched and anastomosing hyphae and 10-25 µm wide epihymenium: ochre to orange-brown, often streaking into hymenium, granular, 10-25 µm thick hymenium: hyaline to pale yellow, (35-)50-60 µm tall; paraphyses: simple or weakly branched and anastomosing below, moderately branched above, with 1 µm wide but apically 1-2 µm wide lumina; subhymenium: hyaline, 25-65 µm thick; hypothecium: hyaline or pale yellow, 4060 µm thick asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid to broadly ellipsoid, (6.5-)8-9.5(-11) x (5-)5.4-6.4(-7.5) µm Pycnidia: not observed Spot tests: thallus K-, C-, KC-, P+ yellow Secondary metabolites: usnic acid, psoromic acid, ±2'-O-demethylpsoromic acid. Substrate and ecology: sometimes endosubstratal, mostly on twigs of conifers and Quercus World distribution: central and western North America Sonoran distribution: Arizona above 1750 m. Notes: Lecanora densa is a distinctive species on account of its light orange-brown apothecia and thallus areoles dispersed on a dark gray hypothallus.