Life habit: lichenized, Thallus: squamulose, small (up to 0.5 mm wide in Northern Hemispheric material), with interspersed dark bluegreen granules, hypothallus indistinct upper surface: green gray to yellow-brown or shining cinnamon brown but greenish when wet; isidia and soredia absent upper cortex: paraplectenchymatous medulla: white, very thin, often indistinct photobionts: primary one a chlorococcoid alga (Myrmecia?); secondary photobiont Nostoc, greenish to dark brown, in wart-like cephalodia lower cortex: paraplectenchymatous Ascomata: apothecial, common, large, sessile, up to 5 mm wide, often concave with brown disc; thalline margin: raised, persistent, squamulose; hymenium: I+ dark blue; paraphyses: simple or branched near apices, apices not thicked or capitate asci: narrowly ellipsoid or cylindrical, with internal amyloid apical tubes, apex K/I+ blue, the tholus staining paler, 8-spored ascospores: simple, colorless, ellipsoid with distinctive, often with 1-2 large oil droplets, often warted epispore, ± apiculate Conidiomata: pycnidial, pale brown conidia: simple, bacilliform, colorless Secondary metabolites: mostly without secondary products Geography: pantemperate, in Northern Hemisphere but primarily in Southern Hemisphere, extending towards the subtropics in high montane areas Substrate: on soil, often among mosses; also on bark in the Southern Hemisphere. Notes: This is primarily a temperate genus occurring in both hemispheres. All species have a green primary photobiont, external cephalodia and ascospores with warted perispores and correspond to what has been called the Psoroma hypnorum group. In the Southern Hemisphere many larger, squamulose or foliose species were placed in this genus, but they are now treated as Pannaria (Jørgensen 2000a).