Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Thallus: appressed, up to 5 (-6) cm broad; texture: soft; branching: variable; budding: often present lobes: contiguous, 1-4 (-6) mm broad; black border: not visible from above; profile: pinched and swollen; width/height ratio: 1.5-5; tips and axils: perforate upper surface: white to greenish gray, rarely dark mottled, becoming rugose soredia: diffuse, powdery, laminal, generally 15-40 µm in diameter, developing from gradual deterioration of the cortex, rarely arising from the edges of a cracking cortex; isidia absent, lobules rare medulla: hollow; ceiling and floor of cavity: both dark lower surface: black, rarely perforate Apothecia: rare, substipitate to stipitate, up to 4 mm in diam; stipe: urn-shaped, hollow; disc: dark reddish brown ascospores: subglobose to globose, 5-5.5 x 5-5.5 µm Pycnidia: uncommon conidia: rod-shaped to weakly bifusiform, 4.5-5.5 x 0.5-0.7 µm Spot tests: cortex K+ yellow, C-, KC-, P+ pale yellow, UV-; medulla K-, C-, KC+ orange-red, P- Secondary metabolites: upper cortex with atranorin and chloroatranorin; medulla with physodic acid (major), and 3-hydroxyphysodic acid (accessory). Substrate and ecology: on bark and wood, typically on shrubs (Salvia, Adenostoma) and conifers (Pinus), most often in coastal chaparral scrub; infrequent Sonoran distribution: San Luis Obispo County, California, south to at least 31oN in Baja California, including Channel Islands (Santa Catalina, Santa Cruz, and Santa Rosa). Notes: This distinctive species has soft, puffy, whitish lobes nearly covered by very fine soredia. See notes under H. austerodes and H. farinacea.