Pertusaria rupicola (Fr.) Harm. forma rupicola

    Thallus crustose, rather thick, surface coarse more or less crazed to verrucose with numerous papillae, yellow-greenish when moist, yellow-ochre when dry, prothallus usually limited, blackish. Apothecia rather rare, at apices of wart-bodies, disc irregular, brownish, often at the bottom of splits. Ascii 4-(8)-spored. Ascospores colourless, simple, thick wall, broadly ellipsoid, 70-110 x 30-50 µm. Photobiont: chlorococcoid. Cortex : C+ orange, K+ yellow, KC+ yellow to orange, Pd-. Saxicolous, coastal, suboceanic and Mediterranean, on sloping and vertical walls little exposed to direct sun. N.B. Very difficult to distinguish from Pertusaria pluripuncta f. fertile, notably in the West of France, but the typical form of the latter is coastal, its prothallus is well developed and with zonation, several apothecia are crowded per areole instead of being at the top of wart-bodies. Inventories of Pertusaria rupicola in Brittany probably are erroneous. A sterile form with numerous isidia may be found: Pertusaria rupicola f. coralloidea. N.B. Pertusaria flavicans, with similar colors, is sorediate.