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 7 (-10) cm broad; texture: cartilaginous; branching: variable; budding: present lobes: contiguous to ± separate, 0.5-3 (-4) mm broad; black border: not visible; profile: even to nodulose; width/ height ratio: 0.7-3, tips and axils: entire upper surface: white to greenish gray, dark mottled or not, becoming rugose soredia: laminal, arising from rugosity on the upper surface which then cracks and develop soredia along the edges of the cracks; isidia and lobules lacking medulla: hollow, ceiling of cavity white, floor of cavity grayish or brownish lower surface: black, entire; Apothecia: rare, substipitate to stipitate, up to 5 (-10) mm in diam; stipe funnel shaped, hollow; disc: brown to reddish brown ascospores: subglobose, 5-6 x 4-5 µm Pycnidia: rare conidia: rod-shaped to weakly bifusiform, 2-2.5 x 0.6-0.9 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), 3-hydroxyphysodic acid (accessory, frequency about 80%), 2'-O-methylphysodic acid (minor accessory), unknown C8 (minor accessory). Substrate and ecology: on bark or wood, especially conifers in montane forests World distribution: boreal and montane forests in continental climates of Europe, more rarely in North America Sonoran distribution: southern Rocky Mountains. Notes: Hypogymnia farinacea is distinguished by close-set, imperforate, appressed lobes, pale color, and soredia arising at the edges of cracks in rugosities of the upper cortex. This kind of soredia is occasionally seen in H. bitteri, H. austerodes, and H. mollis, but in those cases it is never the predominant form of the soredia. Hypogymnia farinacea and H. mollis do not melanize in exposed environments, while H. bitteri and H. austerodes become light to dark brown in the sun. See further discussion under H. austerodes.