Stromata widely effuse, often >10 mm diam. and to 1 mm high, irregularly shaped, developing beneath the periderm and breaking through in wide areas; flat-topped, the disc blackish brown, interior pale brownish, lighter than the bark; immersed part of the stroma delimited by a black zone. Anamorph: Libertella-like; described in culture by Rappaz (1987). Teleomorph: Ascomata perithecia, densely crowded, uniseriate, situated in the upper part of the stroma, 250-300 µm diam. and ca 400 µm high, globose to pyriform; ostiolar neck 70-80 µm diam. beneath the surface crust, ca 120 µm diam. in the very low, pulvinate free part, with minute but distinct radiating furrows. Peridium very thin and soft, 12-15 µm thick, brown, of an indistinct small-celled structure, black and almost opaque in the ostiolar region. Interascal tissue not clearly developed, but periphyses numerous. Asci 30-40 (-55) x 4-5 µm (spore-bearing part), narrowly clavate with a long tapering stalk, with a minute apical ring that does not blue in iodine. Ascospores irregularly biseriate, 6-10 x 1.5-2 µm, allantoid and almost cylindrical, the ends rounded, aseptate, pale brown, thin-walled, smooth, without a gelatinous sheath or appendages.