[Lecanora radiosa var. karelica Räsänen, moreLichen swartzii Ach., Parmelia swartzii (Ach.) Ach., Placodium swartzii (Ach.) Duby, Placolecanora subradiosa (Nyl.) B. de Lesd., Placolecanora subradiosa var. fossulata B. de Lesd., Placolecanora subradiosa var. subradiosa (Nyl.) B. de Lesd., Verrucaria swartzii (Ach.) Ach., Zeora swartzii (Ach.) Arnold]
Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: crustose, rimose to verrucose areolate to verrucose peltate; prothallus: white areoles: flat to bullate or peltate, thick, opaque or glossy, ecorticate surface: yellowish white to yellowish gray or yellowish orange to orange-white or whitish gray to gray, smooth, white pruinose, with an effigurate margin, or arachnoid, esorediate Apothecia: constricted at the base to almost subpedicilate, 0.5-1.5 mm in diam., lecanorine disc: brown or gray brown, convex; heavily whitish or bluish gray pruinose margin: concolorous with thallus, thin, becoming excluded, even, not flexuose, smooth, entire or verruculose, without a parathecial ring amphithecium: present, with numerous algal cells, with large crystals, insoluble in K, corticate; cortex: distinct, basally thickened, gelatinous or interspersed, hyaline, 15-25 µm thick laterally, 20-50 µm thick basally parathecium: hyaline, containing crystals soluble in K epihymenium: brown to dark brown, with pigment dissolving in K, with crystals dissolving in K hymenium: hyaline, clear; paraphyses slightly thickened (up to 3 µm wide) apically, not pigmented; subhymenium: hyaline, 15-20 µm thick; hypothecium: hyaline, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid, 9-14 x 6-7.5 µm; wall: less than 1 µm thick Pycnidia: not seen Spot tests: thallus and apothecia K+ yellow, C+ orange, P+ pale yellow Secondary metabolites: containing atranorin (major), chloroatranorin (minor), eugenitol (minor), roccellic acid (major), sordidone (major). Substrate and ecology: on siliceous rocks under overhangs and on shaded rocks World distribution: bipolar Sonoran distribution: central Arizona. Notes: Lecanora swartzii belongs to the L. rupicola-group is easily recognized by the almost subpedicillate apothecia with a thin margin that becomes excluded, the thick thallus that contains sordidone, and the presence of an amphithecial cortex.