Galapagos Species Database

Thallus thin, continuous to rimose, white to whitish gray; surface dull, whitish pruinose, ecorticate; Apothecia immersed, flush with the thallus surface, lirellate; lirellae slender, elongate, sparsely to moderately branched; labia thin, striate, black, but appearing whitish gray, entirely covered by fine, white pruina, typically surrounded by a thick thallus rim, which is distinctly separated from the thallus by a thin fissure; disc concealed to barely open, grayish white pruinose where visible; exciple only apically carbonized, carbonization not extending laterally; hymenium hyaline, clear (not inspers), I–; ascospores hyaline, I+ bluish violet, 8 per ascus, fusiform, 22-45 x 6-11 µm, transversely septate, 6-12 celled. Chemistry: No substances found; all spot tests negative.

The only other densely pruinose species is G. caesiella, but that species reacts K+ orange (red crystals), it has blackened lirellae that are only sparsely pruinose and, although immersed, typically more prominent. The two species are therefore superficially not very similar. The entire aspect of G. glaucescens is white, the lirellae barely visible as pale grayish streaks. In contrast lirellae of G. caesiella are much darker and thus quite distinct. Staiger (2002) correctly describes the labia of G. glaucescens as striate although this striation of the labia is typically only visible in cross section and not to be confused with the appearance caused by the relatively broad thalline rim that surrounds the apothecia.