Anamorph: Conidiomata subcuticular, 0.7-1.5 x 0.3-0.6 mm, irregular in form but mostly elliptical to oblong in outline, strongly flattened, often confluent, dark grey to black. Upper wall composed of small ark brown thick-walled angular cells, almost completely occluded by melanized material, opening with irregular splits. Lower wall composed of several layers of small mid brown angular cells 5-7 µm diam. Conidiophores absent or reduced to small barrel-shaped cells, the conidiogenous cells mostly developing from a hyaline subconidiogenous layer above the lower wall. Conidiogenous cells (4.5-) 6-9 x ca 1 µm, cylindrical, proliferating sympodially at the apex, often with more than one conidium attached, denticles not visible. Conidia 3.2-3.8 x ca 1 µm, ellipsoidal to cylindric-ellipsoidal, sometimes slightly curved, aseptate, hyaline, thin-walled, smooth, without an epispore, gelatinous sheath or appendages. Teleomorph: not known.
The species is treated here in the sense of Grove (1937); it may well not have a nomenclaturally acceptable name. The type of L. filicinum was considered by Holm & Holm (1978) to be referable to Cryptomycina as C. filicina, and restricted to collections on Osmunda. C. pteridis (on Pteridium) also appears to be a different species.