Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.

Thallus: crustose, bullate areolate (thallus surface "gnarled"), distinctly thickened, ±continuous; prothallus: distinct, delimiting the thallus as a black outline surface: usually white to pale ivory rarely whitish gray, dull or ±shiny, smooth (often eroded in herbarium specimens), epruinose, phenocorticate, esorediate medulla: white, lacking calcium oxalate (H2SO4-) Apothecia: lecideine; (0.3-)0.6-1.1(-1.4) mm in diam., soon sessile margin: black, thin, rarely persistent, soon excluded with age disc: black, epruinose, plane, sometimes ±convex proper exciple: similar to the dispersa-type, inner excipular hyphae distinct, not reduced, pigmented, prosoplectenchymatous (textura oblita), extending from the deep reddish brown hypothecium (leptoclinoides-brown, textura intricata), outer excipular hyphae short-celled, cells angular, distinctly swollen (textura angularis) and ±carbonized with various amounts of a brown pigment (cf. elachista-brown, HNO3-) epihymenium: brown, pigmentation continuous with the outer exciple (HNO3-) hymenium: hyaline, inspersed with oil droplets; paraphyses: simple to moderately branched, apically swollen, with a brown pigment cap (cf. elachista-brown) asci: clavate, Bacidia-type, 8-spored ascospores: soon brown, 1-septate, oblong to ellipsoid, usually not constricted, with obtuse ends, not curved, (11-)12.8-[14.6]-16.3(-19) x (5.5-)6.4-[7.4]-8.4(-10) µm (n=60); proper septum: becoming distinctly and ±persistently thickened during spore ontogeny, lateral wall inconspicuously thickened (±Callispora-type); ornamentation: not visible in DIC Pycnidia: infrequent, globose, unilocular; ontogeny similar to the Umbilicaria-type conidiogenous cells: mostly terminal, rarely also intercalary (cf. conidiophore-type V) conidia: bacilliform, 4-5 x 0.5-1 µm (n=20) Spot tests: K+ deep yellow, P+ faintly yellow, C-, KC-, CK- fluorescence: UV+ bright yellow iodine reaction: medulla amyloid Secondary metabolites: diploicin, 3-dechlorodiploicin, fulgidin, and isofulgidin, virensic acid, atranorin and chloroatranorin, gangaleoidin, norgangaleoidin, chlorolecidioidin and dechlorogangaleoidin; brialmontin 1 (J. A. Elix, HPLC). Substrate and ecology: epilithic, on siliceous mineral-poor coastal rock (generally HCl-) World and Sonoran distribution: currently known only from the Pacific coast of Baja California and Guadalupe Island. Notes: Because of the spore type, the oil immersion in the hymenium and the similar thallus morphology, Buellia regineae is closely related to the Sonoran epiphytic B. desertica and the European saxicolous B. leptoclinoides. The distinctly I+ blue medulla and different secondary metabolites distinguish it reliably from those two species.