Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.

Thallus: erect to suberect, up to 6 (-8) cm broad; texture: cartilaginous; branching: isotomic dichotomous; budding: absent or rare lobes: separate to centrally subcontiguous, 1-3 (-4) mm broad; black border: not visible from above; profile: even; width/height ratio: 0.5-2; tips and axils: entire, upper surface: white to greenish gray, sometimes dark mottled, becoming rugose soredia: terminal, in capitate soralia; isidia and lobules absent medulla: hollow, ceiling of cavity white or dark, floor of cavity white or dark lower surface: black, sparsely perforate Apothecia: rare, substipitate, up to 2 mm in diam; stipe: urn- or funnel-shaped, loosely filled with hyphae; disc: brown ascospores: subglobose, 6-7 x 5-5.5 µm Pycnidia: sparse conidia: not seen in local material Spot tests: cortex K+ yellow, C-, KC-, P+ pale yellow, UV-; medulla K-, C-, KC+ orange-red, P-, UV- Secondary metabolites: upper cortex with atranorin and chloroatranorin; medulla with physodic acid (major), 3-hydroxyphysodic acid (major), 2'-O-methylphysodic acid (accessory, frequency about 50%). Substrate and ecology: typically on bark or wood, including conifers and deciduous trees, rarely on mossy rock or alpine sod World distribution: circumboreal, montane, and cool temperate areas; northern Asia, North America, and Europe; in North America south to southern California and central Rocky Mountains Sonoran distribution: southern California and Guadalupe Island in Baja California. Notes: Much more common northward, the species is easily distinguished by its suberect to erect lobes with soredia coating the tips. Young, pre-sorediate specimens might be confused with H. imshaugii, but that species has pure white lobe interiors and only rarely contains 3-hydroxyphysodic acid. Hypogymnia bitteri has terminal soralia but an appressed, rosette-like thallus with contiguous lobes and often an overall brownish color.