Ascocarps in vertical section initially subepidermal, host epidermal cells becoming invaded by fungal cells as ascocarps mature. Upper wall 15-20 µm wide, of pale brown to hyphae, thin-walled cells. Lining inside of upper wall near ascocarp opening is a 20-25 µm wide layer of hyaline, cylindric cells. The outside of this layer becomes dark brown as the ascocarps mature. Lower wall 20-50 µm wide, of dark brown, thick-walled, 4-8 µm diam. cells.

Paraphyses 2 µm diam., often 1-3 times branching near apex, gradually swelling to 4-5 µm diam. at apex, embedded in gel, extending 20-30 µm beyond asci. Asci 145-180 x 7-9 µm, cylindric, tapering to small, rounded apex, wall not thickened at apex, 8-spored. Ascospores 90-130 x 1.5 µm, tapering slightly to both ends, often bending at right angles when released, 0-1 septate.

Pycnidia in vertical section intraepidermal, upper wall more or less lacking, lower wall 20-30 µm wide, comprising dark brown, thick walled fungal cells amongst disrupted host tissue. Near centre of pycnidium a column of hyaline, cylindric cells extends to the top of the pycnidium. Conidiogenous cells lining lower wall, solitary, 8-11 x 3-4 µm, hyaline, flask-shaped, proliferating either sympodially or percurrently, wall at conidiogenous locus slightly thickened, remains of thickening often visible following proliferation. Conidia 3-4 x 0.8-1 µm, cylindric, 0 septate, hyaline.

ETYMOLOGY: brunneolum = brownish, pale brown; refers to ascocarp wall colour.

L. brunneolum is similar to L. tindalii and L. nigrofactum, two Dracophyllum-inhabiting species. All three species have similarly shaped ascocarps, have a similar appearance in vertical section, have ascocarps remaining open even when dry, so exposing the hymenium, and have ascospores bending at right angles when released from asci. The three species can be distinguished by differences in the pycnidia (black in L. tindalii, brown in the other two species), in ascus width (8.5-11 µm in L. tindalii, 7.5-9 µm in L. brunneolum, 5-7.5 µm in L. nigrofactum), and in the shape of the ascus and paraphysis apices. Macroscopically the ascocarps of L. brunneolum appear paler than those of the other two species.

The collections of this species from Northland, Auckland, Coromandel, and Bay of Plenty are known only from Knightia excelsa (Proteaceae), those from Dunedin, Southland, and Stewart 1. only from Dracophyllum longifolium (Epacridaceae). In spite of the divergent host and geographic distribution the two groups of collections are morphologically and anatomically indistinguishable.

See also notes under L. nigrofactum.