Description: Thallus crustose, green to grey-green, at first smooth, then covered in up to 0.3 mm wide, isidia-like, subglobose granules. Cortex 4-8 μm thick, colourless, with many crystals soluble in K. Apothecia lecideine, orange brown to reddish brown, sessile, (0.4-)0.5-1(-1.5) mm across, with a flat, epruinose disc and a rather thick, smooth, sometimes whitish-pruinose proper margin (almost excluded in old apothecia). Proper exciple colourless to pale orange-brown in upper part, of radiating hyphae; epithecium pale orange-brown, K-; hymenium colourless, (69-)80-90(-105) µm high, K/I+ blue; paraphyses simple or forked in upper part, 1–1.5 µm thick at base, the apical cells slightly swollen, up to 2.5 µm wide: hypothecium colourless in lower part, more or less straw-coloured in upper part. Asci 8-spored, clavate to cylindrical-clavate, the apical dome K/I+ dark blue with a pale, conical-pointed apical cushion (axial mass), the wall K/I-, but the thin outer gel K/I+ blue, Bacidia-type. Ascospores 3-7(-13)-septate, hyaline, needle-like, (35-)45-70(-84) x (2.4-)2.5-3.5(-4.2) µm. Pycnidia immersed, pale orange to orange-brown near the ostiole, composed of several locules. Conidia curved, simple, 10-24 x 0.6-0.8 µm. Photobiont chlorococcoid. Spot tests: K-, C-, KC-, P-., UV-. Chemistry: without lichen substances; apothecia with the Rubella-orange pigment.
Note: a temperate lichen found on old trees, especially oaks, still widespread, but probably declining, almost extinct in the Po-plain, with optimum in the submediterranean belt.