Colonies on upper surface of living leaves, macroscopically invisible, but clearly seen under dissecting microscope, comprising groups of conidiomata and ascomata linked by meandering, branched, sparse hyphae. Colonies more or less circular in outline, about 3-5 mm diam., conidiomata and ascomata usually confined to the central 1.5-2.5 mm of the colony, colonies often confluent, sometimes covering entire upper surface of the leaf. Hyphae intracuticular, flattened, ribbon-like, 1-3 µm high, 8-9.5 µm wide, typically comprising alternating hyaline and dark brown cells, hyaline cells 25-30 µm long, dark cells 6.5-9.5 µm long, dark cells with thickened walls; if two hyaline cells adjacent, then separated by a thick, dark septum, septa with a prominent central pore.

Fruiting bodies appear to arise from the sides of the hyaline cells, where a thick, dark septum forms between part of the side wall of the cell and the adjacent cell of the fruiting body. Ascomata somewhat flattened, circular in outline, 0.15-0.2 mm diam., intracuticular or subcuticular; upper wall up to 10 µm thick in vertical section, comprising 1-3 layers of angular cells 4-6.5 µm diam. with walls thick, dark brown; in face view cells of upper wall more or less cuboid, 6.5-7.5 µm diam., arranged in quite regular, radiating rows; lower wall more or less lacking, comprising remains of a single layer of cells that split as ascomatal cavity forms; in centre of ascoma is a column of hyaline, cylindric cells which extends between base and upper wall, the wall above this column breaks down to form a single, central, round ostiole; ascogenous hyphae develop in a ring near outer perimeter of ascoma, the developing asci lying more or less flat, orientated inward toward centre of ascoma.

Asci in water 70-80 x 14-16 µm, more or less cylindric, uniformly thin-walled, 8-spored, spores clustered near top of ascus; in 3% KOH asci slightly shorter, 60-70 µm long, spores clustered near base of ascus, with wall very thick at apex, with narrow central pore; dehiscence fissitunicate.

Ascospores 11.5-13(-14) x 5-6 µm (mean 12.4 x 5.6 µm, n = 33), oblong or tapering slightly to base, ends broadly rounded, wall smooth, slightly thickened, dark brown with a broad hyaline band in upper third of spore, 0-septate.

Paraphyses probably lacking; in squash mounts irregularly branched, paraphysis-like elements are seen amongst the asci, but these appear to arise from a different hyphal system to that holding the asci, and they may form the central column of sterile tissue.

Conidiomata somewhat flattened, circular in outline, 0.15-0.2 mm diam., intracuticular or subcuticular; upper wall up to 15 µm thick in vertical section, comprising 1-3 rows of angular cells 5-6.5 µm diam. with walls thick, dark brown, inside of wall lined with conidiogenous cells; in face view, cells of upper wall more or less cuboid, arranged in regular, radiating rows; lower wall more or less lacking, comprising lower wall of a layer of cells that appears to break as ascomatal cavity forms. Conidiogenous cells initially ampulliform, 4.5-6.5 µm diam., developing narrow necks up to 12 µm long with age, necks with a series of annellations due to percurrent proliferation. Conidia 8.5-9.5(-10.5) x 4.5-5.5 µm (mean 9.4 x 4.9 µm, n = 34), ovoid, tapering toward apex, ends broadly rounded, hyaline, 0-septate.