Varicellaria hemisphaerica (Flörke) Schmitt & Lumbsch

 

=Pertusaria hemisphaerica (Flörke) Erichsen

    Thallus crustose, rather thick, smooth to rugose-verrucose, sometimes wrinkled, cracked, whitish, pale white-greyish, pale greyish, pale grey-bluish, more or less covered (notably towards the center) with soralia, markedly convex or hemispherical, 1-2 mm diam., concolourous or pale grey-greenish, prothallus often well developed but sometimes restricted to a simple margin, with a circular zonate structure, whitish, sometimes very pale brown-pink. Apothecia unknown. Photobiont: Chlorococcoid. Soralia: C+ carmine red, K-, KC+ red, Pd-, UV+ white-bluish. Rather rare, on rough bark of deciduous tree trunks, notably towards the base. May be confused with some taxa of Ochrolechia androgyna but the latter have more cracked and verrucose thalli, and in general more numerous C+ carmine red soralia. Also not to be confused with Pertusaria albescens var. corallina which sometimes has a similar aspect but negative chemical reactions.*