Thallus: verrucose-areolate, not distinctly limited, studied specimens up to 7 cm in diam., but probably covering larger areas, 0.2-0.7(-1.5) mm thick areoles: verrucose, round, rarely angular, convex, dispersed, rarely in parts contiguous, (0.2-)0.3-0.7(-1.5) mm in diam., fertile areoles usually large prothallus: large areas without visible prothallus, but sometimes forming black areas between the areoles surface: almost white or gray-white to white-gray or gray, sometimes partly gray-brown to light brown, dull upper cortex: (20-)25-45 µm thick with ±crystals, uppermost part ±brown, 5-12(-15) µm thick, with cells 4-7(-9) µm in diam.; cortex covered with an epinecral layer 2-10(-14) µm thick photobiont: chlorococcoid; cells: ±round, 5-17 µm in diam. Apothecia: aspicilioid, rather common, (0.1-)0.2-1 mm in diam., 1(-2) per areole, round, rarely angular, fertile areoles often elevated disc: black, usually without pruina, rarely with white pruina, concave, rarely plane thalline margin: ±elevated, rather prominent in larger apothecia, dark or concolorous with thallus, sometimes with a ±distinct, dark proper exciple inside exciple: 40-80(-100) µm wide, I-, or sometimes I+ blue in the lower part and medially; uppermost cells brown, ±globose, 4.5-6(-7) µm in diam. epihymenium: green to olive or olive-brown, usually without but sometimes with crystals, N+ green to blue-green, K+ brown hymenium: hyaline, I+ persistently blue, 120-160(180) µm tall paraphyses: moniliform or sometimes submoniliform, with (1-)3-5(-7) upper cells ±globose, or sometimes subglobose to cylindrical, uppermost cells (3-)3.5-4.5(-5) µm wide; in lower part, 1.5-2(-3) µm wide, slightly branched and anastomosing subhymenium and hypothecium: pale, I+ persistently blue, together (30-)45-70 µm thick asci: clavate, (80-)100-120 x 18-30 µm, 8-spored ascospores: hyaline, simple, ellipsoid, (16-)18-26 x (9-)11-14(-16) µm Pycnidia: rare to rather common, 1(-3) per areole, immersed, 120-150 µm in diam., with a black, punctiform ostiole, 50-80(-100) µm in diam conidia: filiform, 10-16(-21) x 0.8-1 µm Spot tests: cortex and medulla I-, K+ red, P+ orange, C- Secondary metabolites: norstictic acid, sometimes also trace of connorstictic acid. Substrate and ecology: on siliceous and volcanic rock, at 300-850 m World distribution: western U.S.A: Oregon to southern California Sonoran distribution: only known from southern California (Riverside Co.). Notes: Aspicilia sipeana is characterized by its gray-white to gray, verrucose-areolate thallus with dispersed, convex areoles, a hymenium of medium height, its rather large spores, conidia of medium size and the presence of norstictic acid. In the original description Magnusson recorded 5-7 µm long conidia from a pycnidium in an apothecium. Re-examination of the type (Lane Co., Oregon), however, showed that pycnidia are not uncommon in the areoles, and contain conidia measuring 10-16 µm. The pycnidia with the short conidia, also found in the two Californian specimens (as well as ordinary pycnidia), probably belong to a parasymbiont that has also been found in some other Aspicilia species from the Sonoran area. A specimen from San Benito County, California, had young, small apothecia with rather flat thalline margin, but has a typical dispersed, verrucose-areolate thallus and fits well with the Oregon specimens. The specimen from Riverside County has a thallus in part with rather flat, contiguous areoles separated by large cracks and in part with ±dispersed, verrucose and convex areoles (then resembling the Oregon specimens). The microscopical characters of the two specimens from California agree with the type. Other gray Aspicilia-species with norstictic acid in California, as A. brucei, A. cinerea and A. pacifica differ from A. sipeana by the contiguous areoles. Furthermore, A. brucei and A. pacifica have shorter conidia, and A. brucei and A. cinerea have shorter spores, than A. sipeana.