Ascomata subcuticular. In vertical section upper wall of unopened ascomata up to 45-60 µm thick, narrower toward the outside edge and near the centre of the ascomata. Upper wall comprising mostly dense, black tissue with no obvious cellular structure, but with brown to pale brown, angular cells at the narrow, central part of wall. The inside of this central part of the wall is lined with a few thin-walled, hyaline cells. In opened ascomata the upper wall is up to 60-90 µm thick, slightly thinner toward the ascomatal opening and toward the edge of the ascomata. There is no well-differentiated, persistent zone of paler cells lining the exposed face of the broken upper wall. Lower wall 30-45 µm thick, of 5-10 rows of angular cells, brown to dark brown and thick-walled toward the outside of the wall, hyaline and thin-walled toward the inside.

Paraphyses 1.5-2.0 µm diam., undifferentiated at the apex, barely extending beyond asci. Asci 130-175 x 11-13 µm, clavate, becoming clavate-stipitate immediately prior to spore release tapering slightly to the broadly truncate to somewhat rounded apex, wall often with a small pore at the apex, 8spored. Ascospores bifusiform, 22-33 x 3.5-5.0 µm (average 24.5 x 4.1 µm), broadly rounded apex, tapering toward base, constricted to 1.0-1.5 µm diam. near middle of the spore, surrounded by a narrow gelatinous sheath.

Conidiomata subcuticular. In vertical section the upper wall is 3-5 µm thick, comprising brown to pale brown material with no obvious cellular structure. Lower wall 5-10 µm thick, comprising 2-3 rows of angular cells, outer layers of cells brown, inner layers hyaline. Conidiogenous cells develop on the innermost cells of lower wall, 8-15 x 2-3 µm, cylindric, solitary, proliferating sympodially, often with two developing conidia at apex. Conidia 4-6 x I µm, cylindric, ends rounded, straight, 0-septate, hyaline.

ETYMOLOGY: named after host substrate.

NOTES: Ascomatal shape and ascospore shape distinguish this species from H. cordylines, also found on Phormium in New Zealand.

See also notes under H. carinatum.