Galapagos Species Database

Thallus thin, often partially embedded in the bark, continuous to rimose, pale creamy white, grayish or ochraceous, ± the same color as the substrate; surface smooth to uneven, not pruinose; Apothecia immersed to prominent, circular to oval, not distinctly lirellate; proper margin thin, indistinct, typically with an additional thin, papery thallus layer, young disks as if “bursting open” from the thallus; disc expanded, initially ±concave and ±immersed, but soon flattened, inconspicuously covered by a farinose whitish pruina; exciple basally not carbonized, pale yellowish or brown, laterally expanding, apically increasingly becoming carbonized, wedge-shaped, typically surrounded by a thin, but distinct thallus layer; hymenium hyaline, inspers, I–; ascospores pale gray, brownish with age, I+ red or reddish brown; 8 per ascus, narrowly oblong to fusiform, 27-47 x 7-10 µm, transversely septate, 6-11 celled. Chemistry: No substances found; all spot tests negative.

Because of its circular apothecia quite a distinctive species that superficially may resemble P. fusca, a species that has the same kind of immature apothecia bursting from the thallus, but typically at least ±elongate, more oval lirellae. Chemically the two species are distinct (P. fusca contains norstictic acid), they differ in exciple carbonization, and ascospores of P. lobata are transversely septate, not (sub)muriform.