Description contributed by Graham Kinsey (CABI), based also on Sutton (1980).
Anamorph: Pyrenochaeta sp. Conidiomata pycnidia, to 200 µm diam, globose to subglobose, subepidermal but becoming superficial, ostiolate, hairy, the wall composed of angular cells. Conidiophores not exceeding 100 µm, septate, simple, seldom branched, conidiogenous cells 6-10 x 1.5-2 µm, terminal and intercalary with fertile loci immediately below septa. Conidia 1.5-2.5 x 1-2 µm, cylindrical, straight or slightly curved.
Teleomorph: ascostromata 500-750 µm diam, uniloculate, perithecial, ± globose, sometimes with a slightly immersed base, upright, not or minutely papillate, black, with sparse to abundant red-brown hyphae 5-6 µm diam arising from the surface except at the apex and merging with a subiculum, not setose, crowded, intially subepidermal but later exposed by weathering of the substrate and appearing superficial. Peridium 60-80 µm thick, widening to ca 150 µm at the apex, composed of angular, brown, polyhedral cells, darker and with thicker walls at the outer surface, paler and compressed at the inner surface; lateral and basal regions uniform but widened internally at the apex with dark thick-walled cells forming a ring around the ostiole. Interascal tissue of cellular pseudoparaphyses 1-2 µm diam, hyaline, filiform, septate, branched and anastomosed, at least initially continuous from top to bottom of the cavity. Asci 128-160 x 12-14 µm, cylindric-clavate, apex rounded, base tapering to a lobed and often foot-shaped base, thick-walled, sometimes with an internal apical beak, fissitunicate, 8-spored, J-, arising in parallel from the lower half of the cavity. Ascospores 36-50 x 5-6 µm, fusiform, hyaline, 1-septate, constricted at the septum, smooth, lacking a gelatinous sheath.