Galapagos Species Database

Thallus thin, continuous to rimose, gray to whitish gray, or creamy white; surface dull, not pruinose; Apothecia erumpent, lirellate; lirellae broad, elongate and rarely branched; labia thick, distinctly striate, shiny black, not covered by the thallus, but basally with lateral thallus hem; disc concealed, a thin slit; exciple completely carbonized, carbonization extending below the hymenium; hymenium hyaline, clear (not inspers), I–; ascospores hyaline, I+ bluish violet, 8 per ascus, ellipsoid to broadly fusiform, 25-50 x 5-10 m, transversely septate, 8-14 celled. Chemistry: No substances found; all spot tests negative.

All Galapagos material has a closed exciple, i.e., the carbonization is not confined to the lateral part, but extends below the hymenium. Previous records of G. striatula are therefore misidentifications of G. rimulosa. Because of its relatively broad, pitch black, distinctly striate lirellae G. rimulosa can not easily be confused with other Galapagos species. Unlike most other species of Graphis with broad, distinctly striate lirellae, the apothecia of G. rimulosa are never covered by thalline material and only basally hemmed in by a thin white thallus rim.