Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Primary thallus: squamulose, persistent; squamules: 4-5 mm long, 2-3 mm wide, crenate-lobate, upturned or involute, with dying bases ochraceous podetia: 10-40 mm tall, yellowish green, cup-bearing; cups: up to 1 cm wide, regular to slightly asymmetrical; margins: entire surface: mostly corticate, esorediate, not granulose but occasionally squamulose cortex: continuous to chinky-areolate, often appearing as rough scales on the podetia Apothecia: common, up to 6 mm wide, red ascospores: fusiform, 9-10 x 3 micro meter Pycnidia: common, on cup margins, ovoid to conical, at base constricted or not, with red gelatin conidia: 6-8 x 1 micro meter Spot tests: K-, KC+ yellow, P-, UV- (or UV+ weak bluish-white) Secondary metabolites: thallus with barbatic and usnic acids; apothecial discs with rhodocladonic acid as a red pigment. Habitat and ecology: on mossy boulders and rocks (including lava) and thin acidic soils in well-lighted habitats at high elevations, mainly arctic to boreal World distribution: Antarctica, Asia, Europe, North America and South America Sonoran distribution: Arizona at high elevations. Notes: Stenroos (1989a & b) segregated C. borealis from C. coccifera on the basis of secondary chemistry and subtle morphological differences. The primary squamules of the material studied here were evanescent rather than persistent, and the podetia were shorter than in Stenroos's description. Some specimens with the chemistry of C. borealis (barbatic and usnic acids) approach C. coccifera (zeorin and usnic acid), which is very rare in the Sonoran region. The podetia of C. borealis are esorediate, unbranched, cup-forming, with scarlet apothecia on the margins of the cups. Partially corticate specimens of C. pleurota may be confused with C. borealis, but C. pleurota is always sorediate.