[Lecanora verrucigera (Hue) Zahlbr., more, Lecanora verrucigera f. densata H. Magn., Lecanora verrucigera f. incrassata H. Magn., Lecanora verrucigera f. pleiocarpa H. Magn., Lecanora verrucigera f. subelevata H. Magn., Lecanora verrucigera f. verrucigera (Hue) Zahlbr., Lecanora verrucigera var. superfluens H. Magn., Lecanora verrucigera var. verrucigera (Hue) Zahlbr.]
Thallus: areolate to rarely verrucose, up to 4 cm in diam., (0.1-)0.2-0.5(-0.6) mm thick areoles: angular, rarely rounded, flat to slightly convex, (0.2-)0.3-0.8(-1.2) mm in diam., contiguous or rarely dispersed, in parts slightly radiating at the thallus edge prothallus: indistinct or thin, sometimes present between areoles or at the thallus edge, rarely fimbriate, black to brown-black, 0.1-0.5(-1) mm wide surface: gray, some areas gray-brown to light brown, dull to slightly shiny upper cortex: 20-30(-35) µm thick, uppermost part brown, 8-10(-15) µm thick, cells (4-)5-7(-8) µm in diam.; cortex covered with an epinecral layer 5-12 µm thick photobiont: chlorococcoid, cells ±round, 5-16 µm in diam. Apothecia: aspicilioid, common, 0.1-0.3 mm in diam., 1-3(-7) per areole, round, or sometimes angular or elongated disc: black, epruinose, concave thalline margin: thin, flat or slightly elevated, concolorous with thallus exciple: 35-40(-50) µm wide, I-; uppermost cells brown, ±globose, 5-6 µm in diam. epihymenium: olive to olive-brown, without or with a few crystals, N+ green, K+ brown hymenium: hyaline, I+ persistently blue, (130-)140-160(-170) µm tall paraphyses: moniliform, with (2-)3-5(-6) upper cells ±globose to sub-globose, uppermost cells 3-4 µm wide; in lower part, 1.5-2 µm wide, slightly branched and anastomosing subhymenium and hypothecium: pale, I+ persistently blue (but often faint and some parts I-), together 40-50 µm thick asci: clavate, 65-80 x 17-22 µm, 8-spored ascospores: hyaline, simple, ellipsoid, (15-)16-19 x 10-13(-14) µm Pycnidia: rare, 1 per areole, immersed, 110-150 µm in diam., with a black, punctiform ostiole, 50-80 µm in diam conidia: filiform, 14-23 x (0.6-)0.8-1 µm Spot tests: medulla I-, K+ yellow, P+ orange, C- Secondary metabolites: stictic acid (major) and norstictic acid (minor). Substrate and ecology: on siliceous rocks and boulders in open situation World distribution: temperate to boreal to alpine areas of Europe and North America Sonoran distribution: not found in the Sonoran area, but in northern California, Siskiyou Co., at 1750-2000 m. Notes: Aspicilia verrucigera is characterized by a gray thallus and numerous, small apothecia, medium sized spores, rather long conidia and the presence of stictic acid. The two specimens from Siskiyou County differ slightly from A. verrucigera by having a taller hymenium and an exciple which is negative in I. Another specimen from Siskiyou County (edge of Marble Mountain Wilderness; Ryan 25203; ASU) contains only norstictic acid, and has an exciple that reacts I+ blue. However, in other respects it resembles the two stictic containing specimens examined here quite well. Further studies, preferably with DNA, are needed to document the inferred relationship with European specimens of A. verrucigera. Aspicilia cinerea differs from A. verrucigera by a lighter thallus color and larger apothecia, its brown epihymenium and lower hymenium, and by the presence of norstictic acid.