Description: Thallus foliose, heteromerous, dorsiventral, tightly adpressed throughout, forming 3-7(-10) cm wide rosettes, sorediate. Lobes discrete to more often contiguous, 2-4(-6) mm broad, flat, olive-green or olive-brown, smooth to rugulose in central parts, dull throughout, with small, punctiform, yellowish, laminal soralia which often give rise to soft, globose to cylindrical, c. 9.25 mm tall, 0.02-0.06 mm thick isidioid outgrowths. Lower surface pale at margins, dark brown to black in central parts, with mostly simple, dark rhizines. Upper cortex paraplectenchymatous, with a pored epicortex, the cell walls containing isolichenan; medulla white to yellowish; lower cortex paraplectenchymatous. Apothecia very rare, lecanorine, with a brown disc and an often sorediate thalline margin. Epithecium brown; hymenium and hypothecium colourless. Asci 8-spored, clavate, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, 9-13 x 5-7 µm. Pycnidia rare, black, immersed, laminal. Conidia weakly fusiform to bacilliform, 5.5-7 x 1 µm Photobiont chlorococcoid. Spot tests: upper cortex K-, C-, KC-, P-, N-; medulla K-, C+ red, KC+ red, P-, UV-. Chemistry: medulla with lecanoric acid and subauriferin.
Note: a mainly temperate, pioneer species of smooth bark, e.g. on twigs of shrubs and trees, but also on boles of oaks in open woodlands and parklands; common throughout the country, with optimum in the submediterranean belt.
Growth form: Foliose, broad lobed
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)