Stroma irregular in shape but usually ±circular, up to c. 20 mm diam., black, weakly punctate, slightly raised above the leaf surface, surrounded by a narrow brownish area of dead host tissue. Anamorph: Conidiomata immersed, at first discrete but soon aggregating to form one to several locules; upper wall rather irregular, consisting of an outer layer of host cuticle and a single inner layer of fungal cells 5–8 μm diam. Conidiomata dehiscing by means of many rather irregular ostioles ca 5 μm diam.; lower wall 8–13 μm thick, consisting of heavily degraded epidermal cells and rather thick-walled poorly defined textura intricata with slight blackening in the intercellular spaces; the leaf tissue below the lower wall filled with ramifying hyaline thick-walled hyphae apparendy surrounded by copious quantities of gel; subhymenial layer 5–10 μm thick, consisting of thick-walled textura intricata. Conidiogenous cells phialides, often sited on short hyaline conidiophores, smooch, hyaline, ±cylindrical, tapered towards the apex, 7–15 × 1·5–2 μm, development enteroblastic, with inconspicuous periclinal thickening. Conidia hyaline, cylindrical, aseptate, 6–10 × ca 1 μm, smooth, thin-walled, probably spermatial in function. Teleomorph: Ascomata apparently developing directly from the conidiomata. In surface view: Ascomata elliptical to oblong-elliptical, 500–1300 (–1800) × 300–500 μm, often curved and occasionally trilobed, significantly raising the stroma surface, opening by means of an occasionally branched longitudinal split extending two-thirds to three-quarters the length of the ascoma; clypeus matt black, lips and perimeter line absent. In median vertical section: ascomata completely subcuticular, joined by black stromatic tissue continuous with the upper wall, and by an extensive network of thick-walled hyaline gelatinised hyphae invading the host tissue below the ascomata; upper wall irregularly semicircular in section (lips closed), lower wall gently concave. Clypeus irregular in thickness, sometimes thinning slightly towards the edges of the ascoma, consisting of a layer of strongly blackened textura globulosa-epidermoidea 35–60 μm thick below the host cuticle, becoming paler towards the inner surface, which has a thick gelatinous coating; basal wall 17–22 μm thick, consisting of dark brown textura globulosa-epidermoidea invading the host epidermis; subhymenium of hyaline many-septate textura intricata, 20–28 μm thick. Hymenium: Paraphyses 100–135 μm long, hyaline, several-septate, often contorted and sometimes branched at the apex, not swollen, without a gelatinous coating. Asci ripening sequentially, cylindrical, 105–130 × 9–12 μm, short-stalked, apex obtuse to almost apiculate, very thin-walled, without apical thickening, dehiscing by means of a small apical hole, 8-spored. Ascospores borne in a fascicle, sometimes helically arranged, cylindrical, tapering towards the base, 60–80 × 1·5–2·5 μm, hyaline, aseptate, with an apical gelatinous appendage 2 –4 μm long, appearing to have a very thin continuous gelatinous sheath within the ascus which expands and becomes less conspicuous after dehiscence.