Anamorph: Pyrenochaeta berberidis. Conidiomata similar in structure but smaller than the ascostromata; 200-350 µm diam, black, smooth or slightly verrucose, the outer wall composed of 2 layers of strongly melanized textura globulosa, ± smooth but with frequent short dark thick-walled blunt setae, with a single cavity. Conidiophores present as a single layer of small hyaline angular cells, each producing a single conidiogenous cell. Conidiogenous cells 4-5 x 1.5-2 µm, ampulliform to slightly tapered, thin-walled, proliferating percurrently, sometimes extending to form a septate hypha-like structure to ca 30 x 2 µm, with conidiogenous loci formed laterally just below each septum. Conidia 2-3 x 0.5-0.75 µm, cylindrical to bacilliform, usually straight, thin-walled, hyaline, aseptate, without a sheath or appendages.
Teleomorph: derived from a basal mycelial mat immersed in the outer layers of plant tissue, erumpent in clusters through cracks in the bark, 350-650µm diam, ± globose to turbinate, often constricted at the base, black, strongly verrucose, sometimes covered with short dark thick-walled blunt setae especially when immature. Ascomatal cavity to 250 µm diam, ± globose, lined with thin-walled flattened hyaline cells. Peridium with outer layer to 40 µm thick, composed of strongly melanized and ± completely occluded thick-walled textura globulosa with cells to 6 µm diam. Inner tissue composed of slightly larger pale brown thin-walled cells intermediate between textura globulosa and angularis. Interascal tissue composed of copious cellular pseudoparaphyses 2-2.5 µm diam, frequently septate. Asci 132-164(-190) x 16.5-22 µm, cylindrical, short-stalked, thick-walled, fissitunicate, the apex rounded with a distinct invagination in the inner wall, nominally 8-spored but individual spores frequently failing to mature. Ascospores 24-33 x 10-13(-16) µm, sometimes laterally flattened, variable in shape, ± cylindrical with the ends usually acute to obtuse but a small proportion almost truncate, muriform, golden brown, mucous sheath not seen. Primary septum usually slightly submedian, distinctly constricted, the upper section usually slightly wider than the lower one. Secondary transverse septa 7-8 and vertical septa usually 3 when mature, sometimes slightly oblique, their arrangement irregular with individual septa rarely extending from one outer wall to the other.
The anamorph is not a typical species of Pyrenochaeta according to Schneider (1979). Most conidiogenous cells are ± ampulliform rather than hyphal with lateral fertile loci. The conidia are presumably spermatial in function.