Synonyms: Lecanora intumescens var. glaucorufa (Mart.) Körb.; Lecanora subfusca var. intumescens (Rebent.) Flot.; Ochrolechia parella var. tumidula (Pers.) Arnold non auct.; Ochrolechia tumidula (Pers.) Arnold non auct.; Patellaria intumescens (Rebent.) Trevis.
Description: Thallus crustose, usually smooth, continuous to finely rimose in central parts, white to very pale grey, sometimes delimited by a dark prothallus. Apothecia lecanorine, 1-3 mm across, round or irregular in outline, slightly constricted at base, with an ochraceous brown to medium brown, at first slightly pruinose, flat to finally convex disc, and a thick, swollen, often flexuose, pruinose thalline margin. Thalline exciple without a differentiated cortex, the medullary hyphae reaching the margin, with abundant, small, yellowish crystals insoluble in K; epithecium orange to orange-brown, the pigment not dissolving in K, with coarse, yellowish crystals dissolving in K; hymenium colourless, 75-110 µm high; paraphyses slightly thickened at apex; hypothecium colourless, not inspersed. Asci 8-spored, clavate, very thin-walled, with a K/I+ blue, tall tholus penetrated by a faintly amyloid apical cushion, the wall K/I-, surrounded by a blue outer layer, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, 11-18 x 5-8 µm. Photobiont chlorococcoid. Spot tests: thallus K+ yellow, C-, KC-, P+ yellow to orange-red (reaction more evident in the thalline margin of apothecia), UV+ pale orange; apothecial disc P-. Chemistry: atranorin (major), chloratranorin, psoromic acid, 2'-0-demethylpsoromic acid, zeorin.
Note: a cool-temperate species found on smooth subacid bark, with optimum in humid beech forests; present throughout the country, but most common in the beech forests of central and southern Italy.