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

Thallus: crustose, up to 5 cm across, < 1 mm thick, effuse, areolate-squamulose, with a persistent or +soon excluded thalline margin; prothallus: absent areoles: roundish to crenate, 0.3-0.7 mm across, plane to moderately convex, scattered, thin and tightly attached, or becoming aggregated and +imbricated into groups 1.5-2.5 mm across, up to 1 mm thick with +free margins upper surface: pale yellowish green to paler than grayish yellow-green, dull to slightly shiny, epruinose, edges often paler, esorediate upper cortex: 50 µm thick, with numerous dead algal cells medulla: white; algal layer: continuous c. 50 µm thick lower cortex: absent Apothecia: soon sessile and constricted, numerous, becoming crowded and +imbricate, up to 1 mm in diam.; disc: light yellowish brown to light orangish yellow, epruinose, dull to shiny, plane to convex margin: pale greenish yellow, scarcely raised, entire to flexuous, 0.1 mm wide, either without a or with a thin, indistinct, pale gray-green parathecial ring amphithecium: present, with a continuous algal layer (c. 50 µm thick) in the margin and extending below the hypothecium, with a poorly developed medulla without granules or crystals, corticate; cortex: c. 40 µm thick parathecium: hyaline, not distinctly differentiated, with conglutinate, randomly oriented hyphae c. 3 µm wide and with lumina 3-5 x 0.5 µm epihymenium: inspersed with fine brownish granules (soluble in K), 5-10 µm thick hymenium: hyaline, 70 µm tall; paraphyses: hyaline, 2 µm wide, the tips 2-2.5 µm; subhymenium: hyaline, c. 30 µm thick, inspersed with oil droplets; hypothecium: hyaline, up to 200 µm thick in center asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid, 10-13 x 5-6 µm, rather thick walled Pycnidia: not found Spot tests: thallus K-, C-, KC+ yellow, P- Secondary metabolites: containing usnic acid and unknown gray-brown 3 in solvents A, B, and C. Substrate and ecology: on rocks World and Sonoran distribution: central Arizona (San Francisco Peaks). Notes: Lecanora geiserae differs from forms of L. polytropa with well-developed thallus especially by having larger, more squamule-like areoles, a well developed thalline margin with abundant algae and only a poorly developed, pale gray-green parathecial ring, a hyaline hypothecium, thinner epihymenium, and lacking zeorin and rangiformic acid. It differs from L. mazatzalensis particularly by lacking marginal lobes, having generally smaller areoles, constrictedly sessile apothecia, and lacking zeorin.