Thallus on living leaves, often mainly along the main nerves, usually < 5 mm diam., very thin (no more than 15-25 μm thick), inconspicuous, brownish green or grey-green, often with a pink tinge, smooth, composed of a single layer of net-like branched mycelium with cylindrical to irregular cells, becoming broader and more irregular as the colony matures and the interstices between the branches contract. Isidia and soralia absent; occasional soredia may be seen on the thallus but these are probably dispersal propagules from another species. Photobiont a green alga with irregularly rounded aggregates of cells. Anamorph: not known. Teleomorph: ascomata perithecia, 100-150 µm diam. and <100 µm high, developing underneath the mycelial mat; shallowly domed to hemispherical, appearing applanately wart-shaped, pink-brown to almost black, sometimes with a darker red tinge around the ostiole, covered by a thin algal layer until mature. Periphyses always present, made of a layer of cells with conical-ovoid apices. Asci 40-48 × ca 15 μm, clavate or obovoid, with a thin wall except at the apex which is substantially thickened when immature, the wall K/I– but protoplasm typically K/I red-brown, 8-spored. Ascospores (10-)14-16 × (4-) 4.5-5 μm, very variable in both shape and septation, fusiform-ellipsoidal to cylindric-ellipsoidal, initially 0- or 1-septate but usually becoming 3-septate when mature, the upper median and distal cells slightly broader, with rounded ends, hyaline, smooth- and thin-walled, without an epispore, gelatinous sheath or appendages.