Ascomata subcuticular. In vertical section, upper wall of the unopened ascomata up to 60-70 µm thick, comprising mostly brown to dark brown, angular cells, with darker areas along the outer and inside edges of wall, but with a line of paler, thin-walled cells at the centre of the ascomata, along the future line of opening. In opened ascomata the upper wall is up to 90-1 1 0 µm thick near the ascomatal opening, becoming abruptly thinner about half way to the edge of the ascomata. Upper wall comprising either all dense, black tissue with no visible cellular structure, or with a few thick-walled, dark brown, angular cells visible in the centre of the labia. Exposed face of the broken upper wall lined with hyaline to pale brown, thin-walled, cylindric cells. Lower wall 3-5 µm thick, of 1-2 layers of thick-walled, pale brown, angular, 3-5 µm diam. cells. Both walls extending over 200 µm beyond edge of hymenium.

Paraphyses 1-1.5 µm diam., circinate at apices, extending 5-10 µm beyond asci. Asci 110-175 x 11-14 µm, clavate-stipitate, tapering to small, truncate apex, wall undifferentiated at apex, 8-spored, spores confined to upper half of ascus. Ascospores 28-45 x 2.5-3.5 µm (average 37.2 x 2.9 µm), in face view cylindric, apex rounded, near the base tapering to more or less acute base, 0-septate, surrounded by gelatinous sheath.

Conidiomata subcuticular. In vertical section lenticular in shape, upper wall 5 µm thick, of brown to black material with no visible cellular structure. Lower wall of 2-3 layers of brown to dark brown, thick-walled, angular cells. Lower wall is lined with 1-2 layers of thin-walled, hyaline cells on which the conidiogenous cells develop. Conidiogenous cells 6-9 x 2.0-2.5 µm, cylindric, percurrent proliferation, wall thickened at single apical conidiogenous locus. Conidia 3-4 x 1 µm, cylindric, straight, 0-septate, hyaline.

ETYMOLOGY: campanulatus = bell-shaped; refers to ascomatal shape, with a distinctive, flattened, shelf-like plate of tissue surrounding the central, raised part of the ascomata.

NOTES: H. campanulatum is often found in association with two other species, H. carinatum and H. alborubrum. The most distinctive feature of H. campanulatum is the paler, grey, flattened, shelf-like margin to the ascomata.

See also notes under H. carinatum and H. alborubrum.