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 (forming "bread-loaves"), thick, dispersed; prothallus: absent surface: pale brown to tawny yellow ("isabelline"), shiny, smooth, epruinose, rarely faintly pruinose, phenocorticate (with a very thick and distinctly pigmented phenocortex and distinct epinecral layer), esorediate medulla: white, lacking calcium oxalate (H2SO4-) Apothecia: lecideine; (0.3-)0.6-1.1(-1.2) mm in diam., sessile margin: black, thin, rarely persistent, usually excluded with age disc: black, epruinose, plane, soon becoming convex proper exciple: 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, not 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, narrowly oblong to ellipsoid, usually not constricted, with obtuse ends, not curved, (11-)12-[13.6]-15.2 (-19) x (6-)6-[6.7]-7.5(-9) µm (n=60); proper septum: becoming thickened early but only briefly during spore ontogeny (±Physconia-type); ornamentation: microrugulate Pycnidia: infrequent, urceolate to globose, unilocular, at maturity lined with short moderately branched conidiophores; ontogeny similar to the Umbilicaria-type conidiogenous cells: mostly terminal, rarely also intercalary (cf. conidiophore-type V) conidia: bacilliform, 5-9 x 0.5-1 µm (n=20) Spot tests: K+ yellow, P+ yellow, KC-, CK- fluorescence: UV+ bright yellow iodine reaction: medulla non-amyloid Secondary metabolites: atranorin and chloroatranorin, diploicin, 3-demethylscensidin and isofulgidin (J. A. Elix, HPLC). Substrate and ecology: epilithic, on volcanic rock (HCl-) World and Sonoran distribution: Baja California (Guadalupe Island and the fog zone of the mainland). Notes: The species' name derived from Latin "panis" meaning bread refers to the "bread-loaf"-like areoles. It is not to be confused with "panniformis" meaning "with a felt-like appearance". Its strongly bullate thallus with its smooth and shiny brown surface is very characteristic of B. paniformis. The thallus gloss is caused by a very thick epinecral layer that typically covers immature apothecia before they break through the surface. The species could be mistaken for some forms of B. dispersa or B. nashii that lack pruina. These species, however, contain different secondary metabolites.