Violella fucata  (Stirt.) T. Sprib.

    Thallus crustose, highly variable, rather thin and almost smooth to moderately thick, rimose and roughly verrucose, pale greyish, dull white or occasionally slightly purplish-blue, more or less covered with green soralia ordered in small mounds or crusts of yellow-green soredia. Apothecia rare, leceidine, flat to faintly convex, 0.5-1.5 mm diam., blackish (section purple-blue), exciple thin, disappearing soon. Ascospores ovoid, 2 per ascus, 30-50 x 15-21 µm. Photobiont: chlorococcoide. Thallus and soredia: C-, K- yellow-brown, KC+ brown, Pd+ rusty red, UV-. Rare (or understated), corticolous, and seldom lignicolous (in that case most often fertile) on smooth bark of deciduous  trees. N.B. Not to be confused with Buellia griseovirens that is K+ yellow turning red and Pd+ yellow.*