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

Life habit: lichenized, not lichenicolous Thallus: crustose, verrucose-areolate to bullate-verruculose, thick areoles: contiguous or +dispersed, constricted at the base, becoming glebulose surface: gray-brown to pale gray, sometimes white or violet tinged or pinkish brown, sometimes violet tinged medulla: white, weakly I+ blue Apothecia: between the areoles, angular or rounded disc: flat, sometimes convex, dull margin: thin or disappearing epihymenium: reddish brown or olivaceous brown, usually K+ violet hymenium: hyaline to pale brown in upper part; parpahyses: coherent, capitate; hypothecium: brown, K- asci: clavate, 8-spored ascospores: dark brown, muriform, often aborted, ellipsoid, 24-46 x 11-18 µm Spot tests: cortex C+ pale pink; medulla K+ yellow or K-, C+ red, KC+ red, P+ orange, or P- Secondary metabolites: gyrophoric and barbatic acids, and +stictic and +norstictic acids. Substrate and ecology: on exposed acid rocks in arctic to temperate regions World distribution: western and northern North America Sonoran distribution: Arizona, southern California and Baja California. Note: Feuerer (1991) treats R. grande as a chemical race of R. eupetraeum but Timdal (1988) accepts the two as morphologically as well as chemically distinct.