Ascomata initially subepidermal, epidermal cells becoming filled with fungal tissue as ascomata mature. Scattered fibre cells from the host leaf become trapped within the walls of the developing ascomata. In vertical section ascomata initially comprising rows of vertically oriented, hyaline cells, with the lowermost cells becoming dark brown and thick-walled. Paraphyses develop within a central cavity and, as they elongate, the lower wall becomes darker, and the epidermal cells become filled with angular, thick-walled, dark brown fungal cells. In opened ascomata both the upper and lower walls are almost entirely composed of very dark tissue with no obvious cellular structure, intermixed with fibre cells of the host leaf. A few pale, thin-walled, cylindric cells remain at the sides of the hymenium.

Paraphyses 1-1.5 µm diam., undifferentiated at apex, not extending beyond asci. Asci 70-80 x 5-6.5 µm, cylindric to subclavate, tapering slightly to broad, truncate apex, wall unthickened at apex, sometimes with small, central pore, development sequential, 8-spored, spores confined to the upper 40-50 µm of the ascus. Ascospores 30-35 x 1.5 µm, tapering toward both ends, curved or coiling on release, 1-septate, with no obvious gelatinous sheath. Conidiomata 0.3 mm diam, round in outline, pale brown with darker line around outside edge. In vertical section lenticular in shape, both upper and lower walls 5-10 µm thick, of 1-3 layers of brown to dark brown, slightly thick-walled, angular cells, the cells of the lower wall darker than those of the upper. Both upper and lower walls lined with 1-2 rows of hyaline, thin-walled cells, on which the solitary conidiogenous cells are formed. Conidiogenous cells 8-12 x 1.5-2.5 µm, cylindric or tapering to apex, proliferating sympodially, often with two developing conidia held at apex. Conidia 3-4 x 1 µm, oblong-elliptic with rounded ends, 0-septate, hyaline.

ETYMOLOGY: nematoideum = nematode-like, refers to shape of released ascospores.

NOTES: Macroscopically L. nematoideum is typical of the group of species with the pattern of ascomatal development matching L. minus (Tehon) Johnston (Johnston 1989a (as L. multimatricum Johnston), 1989b). It is easily distinguished microscopically from the other species in this group by ascospore shape and size, but is indistinguishable macroscopically from L. minus and L. breve (Berkeley) de Notaris, both also found on Gahnia.