Thallus dimorphic. Primary thallus crustose, granular, verrucose or squamulose, soon disappearing, very seldom persistent. Pseudopodetia erect, usually branched, often complex, springing from a ± well-developed holdfast in some species, corticate or ± completely decorticate, covered with verrucae, or simple or branched phyllocladia which are usually terete and corticate. Medulla loosely woven, containing colonies of a green Protococcoid alga, chondroid axis of thick-walled longitudinal hyphae. Cephalodia abundant to rare, a characteristic feature of the genus, containing a blue-green alga (, or ). Apothecia lecideine terminal, disc frequently convex, occasionally plane and marginate, brown or red-brown to black. Hypothecium usually colourless, brown in some species. Paraphyses simple. Asci clavate to cylindrical, 8-spored. Ascospores colourless thin-walled, elongate-ellipsoid to cylindrical-fusiform or vermiform, transversely 1-13-septate. Pycnidia terminal or lateral, immersed, ovoid to spherical, darkened about the ostiole. Conidia filiform to cylindrical, straight or curved.