Ascomata subcuticular. In vertical section the upper wall of unopened ascomata up to 70 µm thick, narrower toward the edges of the ascomata. Wall comprising mostly brown to dark brown, angular cells, but with a group of paler, thinner-walled cells in the inner part of the wall, along the future line of opening. Ascomatal upper wall starts to split open, and a layer of hyaline, cylindric cells begins to develop along the exposed face of the breaking upper wall, before covering host cuticle breaks. In opened ascomata the upper wall is up to 70-120 µm thick near the ascomatal opening, becoming either gradually or more or less abruptly thinner toward the outside edge. Upper wall comprising dark brown, thick-walled, angular, 4-7 µm diam. cells. Exposed face of the broken upper wall is lined with hyaline, thin-walled, 20-30 x 4-5 µm, cylindric cells. Lower wall 10-20 µm thick, of 2-3 rows of brown, thick-walled, angular to cylindric cells.

Paraphyses 1.0-1.5 µm diam., loosely circinate at apex, extending 5-10µm beyond asci. Asci 90-l40 x 11-16 µm, clavate-stipitate, tapering to truncate apex, wall often slightly thickened at apex with inconspicuous central pore, 8-spored, spores confined to upper half of ascus. Ascospores 14-21 x 4.5-6.0 µm (average 17.0 x 5.2 µm), in face view elliptic, tapering more or less equally to both ends, in side view slightly curved, 0-septate, surrounded by gelatinous sheath.

Conidiomata subcuticular. In vertical section upper wall absent. Lower wall of 1-3 layers of brown, thick-walled, angular cells. Lower wall lined with short columns of angular to cylindric, pale brown to hyaline, 4-8 x 4 µm cells, and the conidiogenous cells develop on this layer. Conidiogenous cells 13-22 x 2-3 µm, Solitary, cylindric, tapering to apex, with sympodial proliferation, often with two conidia held at the apex. Conidia 5-9 x 1 µm, cylindric, straight, ends rounded, 0-septate, hyaline.

CHARACTERISTICS IN CULTURE: Ascospores germinating on agar plates within 24 hours. Colonies on OA 60-80 mm diam. after six weeks, aerial mycelium sparse, white, cottony, agar surface pale greyish-brown, with numerous, scattered, black-walled, globose conidiomata. Conidiomata opening by irregular splits in the wall to expose the grey conidial ooze. Conidiogenous cells and conidia the same as described from plant material.

ETYMOLOGY: named after host substrate of holotype.

NOTES: Hypoderma cordylines is macroscopically similar to the common and widespread H. rubi. The two species can be distinguished by ascospore shape, and by the length of the conidia. H. rubi has not been found on Cordyline spp.