Ascocarps in vertical section intraepidermal or subepidermal. Upper wall 20-30 µm wide, not varying in width across ascocarp, comprising brown to pale brown, 4-8 µm diam. cells. In recently opened ascocarps a poorly developed layer of hyaline, cylindric cells is present along the exposed face of the broken upper wall. As ascocarps become older the upper wall erodes, and the marginal paraphyses become more swollen, closely septate, and tightly embedded in gel, so forming a distinct layer between the ascus-containing part of the hymenium and the upper ascocarp wall.

Paraphyses 1.5-2 µm diam., irregularly swollen to 3.5-5 µm diam. at apex, extending 20-30 µm beyond asci. Asci 100-140 x 7-9 µm, subclavate, tapering to the broadly rounded to slightly truncate apex, wall not thickened at apex, 8-spored. Ascospores 65-95 x 1.5-2 µm, 0-1 septate, with thin gelatinous sheath.

Pycnidia in vertical section intraepidermal, upper wall more or less obsolete, lower wall 10-20 µm wide, of 2-4 layers of dark brown, thick-walled, 3-7 µm diam. cells. Column of hyaline, thin-walled, cylindric cells extends between upper and lower walls near centre of pycnidium. Lower wall lined with conidiogenous cells, 8-12 x 2.5-3.5 µm, solitary, flask-shaped, sympodial. Conidia 2.5-4.5 x 0.8-1 µm, cylindric, 0 septate, hyaline.

ETYMOLOGY: medium = middle, midway between; refers to shape of the ascocarp, more or less intermediate between those typical of the genera Lophodermium and Coccomyces.

NOTES: Coccomyces radiatus Sherwood, which also occurs on Nothofagus menziesii, can be distinguished by larger, paler-walled ascocarps which are always round in outline, and by narrower asci.