Initially evident as hemispherical swellings in the bark surface and subsequently angular cracking caused by development and emergence of pulvinate stromata, with orange-yellow to brown ectostromatic discs through which ostioles extend, the discs ultimately almost black and usually with the surrounding bark surface blackened but without zone lines.
Conidiomata formed as locules within the outer part of the stroma, the wall structure not well-developed. Conidiogenous cells cylindrical and proliferating percurrently, formed on branched conidiophores. Conida dimorphic: alpha conidia 13-21 x 3.5-4.5 µm, fusiform to cylindric-fusiform, hyaline, aseptate, without gelatinous sheath or appendage; beta conidia similar but somewhat smaller (10-15 x ca 2 µm) and irregularly cylindrical in form.
Ascomata perithecial, 240-480 µm tall and 320-640 µm diam, globose to oblate, clustered below the ectostromatic discs and surrounded by well-developed, somewhat paler entostromatic tissue, the walls black, the necks hardly to strongly erumpent through the ectostromatic disc, the ostiolar region cylindrical to ± conic. Interascal tissue not seen. Asci 55-65 x 6-9 µm, clavate, with short evanescent stalks and a consipcuous refractive apical ring, 8-spored. Ascospores arranged biseriately, 15-20 x 2.5-5.5 µm, fusiform-ellipsoidal, hyaline, slightly constricted at the ± median septum, often inaequilateral or slightly curved, without a gelatinous sheath or appendages.