Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Life habit: lichenized Thallus: thin, often immersed, smooth, occurring in small roundish to irregular areas surface: pale greenish gray to whitish Ascomata: 0.3-0.8 x 0.1-0.25 mm, black, narrowly oblong, subimmersed to adnate, often scattered, straight to curved or obscurely flexuous, simple, sometimes branched, epruinose; disc slit-like, slightly widening when old, epruinose exciple: black, widely open below the subhymenium hymenium: 60-75 µm, I+ reddish; subhymenium: pale brown, 35-50 µm; paraphysoids: to 1.5 µm wide asci: claviform, 45-50 x 12-14 µm (Vulgata-type) ascospores: oblong-dactyloid, (12-)14-16 x (3.5-)4-5 µm, 3-septate (Calcarea-type) Pycnidia: not founded Spot tests: thallus K-, C-, KC-, P- Secondary metabolites: none detected. Substrate and ecology: on bark of Umbellularia californica World and Sonoran distribution: southern California (Santa Monica Range, Catalina Island) and Santa Cruz Co. to the north (Tucker 38276, SBBG). Notes: Opegrapha umbellulariae is closely related to the Mediterranean O. celtidicola (Torrente and Egea 1989), but differs in having shorter, epruinose ascomata with slit-like discs.