Caloplaca oasis (A. Massal.) Szat.

    Thallus crustose, rather thin, more or less immersed, possibly continuous or areolate but often discontinuous, forming areoles (0.1-1 mm) clusters, pale yellow, grey-yellowish, dull yellow, sometimes dark brown or blackish in nutrient-rich environments, prothallus and soredia absent. Apothecia numerous, usually clustured and sometimes crowded, 0.2-0.6 mm diam., disc plane when young and then slightly convex, brown-orange, dark orange when dry, orange-yellowish when moist, exciple thin usually persistent, concolourous or paler. Asci cylindrical, 8-spored. Ascospores polarilocular, ellipsoid, colourless, 9.5-13 x 4.5-6.5 µm, with a large septum up to 3-4 µm for mature ascospores (ratio septum/ascospore: 0,24-0,37). Apothecia K+ purple. Slightly thermophile species, on hard calcareous rocks, and seldom on mortar and concrete (and in that case hardly distinguishable from Caloplaca holocarpa ss. str. group to which it belongs). This species is usually parasitic of Verrucaria sp. , at least at first, and shares a common habitat. Later they seem to be autonomous. See other parasitic species but Aspicilia: Caloplaca inconnexa and Caloplaca necator which are much more thermophilic.