Lecanora albella (Pers.) Ach.
Lecanora pallida (Schreber) Rabenh.
Thallus crustose, thin, smooth to minutely granulose, sometimes slightly crazed or areolate towards the center, whitish, grey-whitish, sometimes with a white prothallus. Apothecia usually abundant, scattered all over the thallus, sessile, 0.5-1 mpm diam., disc flat, pinkish, pale brown-yellowish, pale brown-pinkish, appearing white due to dense white pruine, exciple determinate, powdery, more or less wavy, persistent, whitish. Ascopores simple, colourless, broadly ellipsoid, 10-14 x 6-9 µm. Photobiont: Trebouxia. Thallus: C-, K+ yellow, Pd+/- yellow-orange; apothecia: C-, K-, Pd+ bright yellow to red but most often orange. Common, on smooth bark of trees and notably Fagus, scarce on smooth sections of Quercus barks.
_ Not to be confused with Lecanora carpinea of which apothecia are C+ yellow and Pd- and to Lecanora intumescens equally K+ with apothecia exciple Pd+ orange, but apothecia of the latter are much less powdery and less whitish.