Description contributed by Graham Kinsey (CABI), based also on Sutton (1980) and Dennis (1971).
Anamorph: Pyrenochaeta sp. Conidiomata pycnidia, to 350 µm diam, globose, subepidermal but becoming superficial, ostiolate, hairy, the wall composed of angular cells, forming within the subiculum. Conidiophores 25-70 x 2-3.5 µm, septate, branched, cylindrical, conidiogenous cells terminal and intercalary with fertile loci immediately below septa. Conidia 3-6 x 1-2.5 µm, cylindrical, straight to curved, biguttulate.
Teleomorph: ascostromata 100-200 µm diam, uniloculate, perithecial, ± globose, sometimes with a slightly immersed base, upright, not or minutely papillate, black, with stiff black tapering setae ca 50 x 5 µm around the ostiolar region, crowded, intially subepidermal but later exposed by weathering of the substrate and appearing superficial. Subiculum composed of abundant red-brown hyphae 5-6 µm diam. Peridium 40-50 µm thick, widening to 100-120 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 60-80 x 7.5-9 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 15-22 x 3.5-5 µm, fusiform, straight or curved, 1- to 4- but mostly 3-septate, becoming yellowish-brown, constricted at the primary septum, lacking a gelatinous sheath.