Caloplaca cerina (Ehrh. ex Hedw.) Th. Fr.

     Thallus crustose, thin, occasionally inconspicuous, surface smooth or rarely warted, pale to dark grey, tinged grey-glaucous or blue, dark ring at margin more or less defined corresponding to prothallus. Apothecia lecanorine generally numerous, scattered all over the thallus, not in clusters, sessile, disc flat, colour highly variable but often bright, yellow, orange-yellow, orange, brown-orange, wax-yellow (refers to its name), sometimes yellow-lemon, yellow-green when moist, thalline margin persistent, conspicuous, rather thick, even, swollen, raised, flexuose grey to concolourous. Ascospores ellipsoid, colourless, polarilocular, septum wide, about 1.3-12 of the length of the ascospore, 10-15 x 6-8 µm. Photobiont: chlorococcoide. Thallus and thalline margin K-; discs K + purple, KC+ purple. On alkaline bark of deciduous trees, isolated or aligned (Acer and Populus notably). On the field, not to be confused with some other Lecanora species with brighter apothecia (see chemical spot test results with K.). Might well be a cluster of different species. Awaiting clarification with additional approaches.