Colonies discrete, arising in the tissues of the host, filling apothecia or associated with deformations, dark brown to black. Mycelium immersed, originating deep in the thallus, often amongst phycobiont cells, composed of subhyaline or very pale brown flexuose hyphae. Hyphae mainly 2.5-4 µm diam., thin and smooth-walled, septate, often markedly constricted at the septa, becoming inflated near algal cells. Anamorph: conidiomata absent. Conidiophores 15-35 x 2.5-4 µm, not well differentiated from vegetative hyphae, not synnematous, straight to flexuose, unbranched or branched sparsely either near the base or close to the apex, pale brown, smooth-walled, thicker-walled than the mycelial hyphae, septate, scarcely to markedly constricted at the septa, sometimes appearing almost torulose. Conidiogenous cells not proliferating, integrated, terminal, subcylindrical, pale brown, not clearly defined and the terminal cells in turn acting as conidiogenous cells. Conidia 5-8 (-9) x 4-6 µm, adhering in chains, dry, acrogenous, ellipsoidal to doliiform, very pale brown, aseptate or 1-septate, not or slightly constricted at the septum, the septum not broadened and thickened, smooth- and rather thin-walled. Teleomorph: not known.