Fl. Bor. Amer.: 324 (1803).
Chemistry:
Race I: Medulla and lower cortex K+ orange-red, upper cortex usually K+ yellow, lower cortex C+ red, medulla and lower cortex KC+ red; P-. Microchemical: gyrophoric acid, LQ unknown always present; 4-0-methylgyrophoric acid, atranorin, unknown 2 (Jordan 1973: 246).
Race II: gyrophoric acid, LQ unknown (Jordan 1973: 246).