Life habit: lichenized Thallus: crustose, effuse, scurfy granular; prothallus: rarely detected, rather varying in color from white to dark brown surface: white to green, dull ochraceous or brown, rarely sorediate soralia: (if present) ±round, discrete to often confluent and forming large patches, blastidiate, sometimes irregularly shallow-verrucose, often rimose, sometimes areolate cortex: not differentiated, no epinecral layer detected, sometimes filled with crystals (visible as fine to large clusters) photobiont: primary one a chlorococcoid green alga, secondary one absent Ascomata: apothecial, adnate, sessile, sometimes slightly stalked, mostly with a pale thin margin, 0.1-0.6(-0.8) mm in diam. disc: chocolate- to dark brown, flat or later slightly convex, epruinose or thinly white-pruinose exciple: consisting of paraplectenchymatous cells, rarely containing crystals, sometimes becoming excluded hymenium: hyaline, I+ blue; paraphyses: sometimes unbranched, but often branched and anastomosing, 1-1.5 µm in diam.; hypothecium: hyaline, or dull orange-brown or dark reddish brown asci: clavate, Byssoloma-type, (2-)8spored ascospores: hyaline, 1-3(-7)- septate to rarely submuriform, clavate, ovoid, oblong-ovoid to fusiform, 6-37 x 1.5-10 µm; wall: smooth, or sometimes with a perispore which can be c. 2 µm thick in K Conidiomata: pycnidial, often numerous, sometimes conspicuous, ±immersed in thallus, with a white or brown-orange ostiole, often expanded conidia: pyriform, rarely bacilliform to ellipsoid, ±slightly curved, 3-4 x 1.3-1.7 µm Spot tests: all reactions negative Secondary metabolites: dibenzofurans (usnic acid, isousnic acid), higher aliphatic acids (roccellic acid) or triterpenes (zeorin) Geography: cosmopolitan, extending into temperate, rarely boreal areas, best represented in tropical and subtropical areas Substrate: mostly on leaves, sometimes on bark or wood and rarely on acidic rocks.