Thallus: within substrate, not visible, or rarely crustose and composed of scattered inconspicuous areoles, ecorticate surface: gray, esorediate Apothecia: occurring singly, sessile, concave or flat when mature or also slightly convex, 0.3-1 mm in diam. disc: reddish brown, dark brown to black, smooth, epruinose margin: white or rarely slightly brown, prominent or even with disc, thick and distinctly fissured (with 3-10 cracks) when young then thin and slightly crenulate when mature, epruinose, without a parathecial ring amphithecium: present, with algae filling the medulla and reaching the top of margin, 100-170 µm thick, corticate; cortex: indistinctly delimited, +uniform in thickness, 30-50 µm thick laterally and at base, amorphous (cell walls and lumina indistinct), gelatinous, +obscured by granules (pol+, insoluble in K, soluble in N) parathecium: indistinct epihymenium: deeply pigmented (up to 1/3 of the upper hymenium), shades of red or blue-green (turning green in K and more intense brown or purple in N), not at all granular hymenium: hyaline, 40-50 µm tall; paraphyses: thick and adglutinated, upper most part (2-3 highest segments) submoniliform; tips: sometimes branched, end cell distinctly enlarged, coherent in K; subhymenium: distinct, granulose, not transparent, 20-30 µm thick; hypothecium: hyaline or almost so, composed of adglutinated hyphae, darkened by granules (pol-) and oil droples, 50-90 µm thick asci: clavate, 8-spored ascospores: hyaline, simple, narrowly ellipsoid, 10.4-16.3(-17.8) x (4-)4.5 Pycnidia: very rare conidia: elongate, filiform, usually curved, 16-19 µm long Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on dry, exposed sandstone and granite rocks, occasionally also on wood, in desert to montane habitats World distribution: central and western North America Sonoran distribution: eastern and northern Arizona and southern California at elevation of 1830 to 2870 m. Notes: Lecanora flowersiana is characterized by reddish brown, dark brown to black, usually epruinose apothecial discs and white, distinctly cracked (fissured) apothecial margins. It is also easily distinguishable due to its deeply pigmented hymenium, its thick adglutinated paraphyses, that may become submoniliform apically, and its narrowly ellipsoid to elongate spores. The taxon was recognized for the first time by W.A. Weber in 1950's but was subsequently neglected. A similar taxon, L. percrenata H. Magn., was described from central Asia (Magnusson 1940). But the type collection of the latter species is too poor a specimen elucidate potential differences. Further investigations in Asia. For comparisons with the North American species L. crenulata, see under that species.