Thallus: endolithic medulla: white, I- Apothecia: black, with a strongly constricted base, up to 2.2 mm in diam. disc: black, flat to moderately convex, dull, slightly or distinctly pruinose margin: black, persistent, dull to shiny exciple: unpigmented but due to crystalline inspersion brownish opaque, 70-100 µm wide epihymenium: green-black to green-brown (cinereorufa-green), 10-15 µm thick hymenium: hyaline, 40-50 µm tall, I+ blue; paraphyses: unbranched and rarely anastomosing subhymenium: 15-30 µm thick (or indiscernible) hypothecium: unpigmented, or pale ochre to light brown asci: clavate, 30-45 x 8-12 µm, 8-spored ascospores: hyaline, simple, bacilliform, 7.5-15 x (2.5-)2.9-3.3(-4.5) µm, length-width index: 3.2-3.5 Pycnidia: unknown Spot tests: cortex and medulla K-, C-, KC-, P- Secondary metabolites: exciple densely inspersed by crystalline masses of schizopeltic acid; chemical races: (I) schizopeltic acid; or (II) schizopeltic and norstictic acids. Substrate and ecology: in open habitats on granites, schist and other types of acidic rocks of the chaparral World and Sonoran distribution: very rare, lower montane belt in southern California. Notes: Lecidea hassei resembles Lecidea laboriosa in many respects; however, it differs in producing schizopeltic acid (instead of 4-O-demethyl planaic acid). It was named in honor of H.E. Hasse, who wrote the "Lichen Flora of Southern California" in 1913.