Species with fusiform basidiospores with the width range 3.5–4.2 µm, halfway between the width ranges of Subulicystidium robustius K.H. Larss. & Ordynets and S. naviculatum Oberw.

ETHIOPIA. Arussi: Munessa Forest east of Lake Lagano, 7.5833, 38.9167, on dead wood, 10 Jan 1973, L.Ryvarden (LR 8860/b in O:F 909583).

ryvardenii, named after Leif Ryvarden, a Norwegian mycologist, enthusiastic explorer of the tropical fungal diversity and collector of the type specimen.

Basidiomata annual, effused, resupinate, soft and fragile, arachnoid, thin, loosely adnate. Hymenophore smooth, hirsute due to numerous large protruding cystidia, yellowish. Margin thinning out, adnate.

system monomitic. All septa with clamps. Subiculum thin, with loosely interwoven richly branched hyphae 3–4 µm wide, thin-walled to slightly thick-walled, hyaline and smooth. Subhymenium weakly developed, with hyphae 3–4 µm wide, loosely arranged, slightly thick-walled and often covered with a hyaline crystal sheath. Cystidia subulate, 65–115 × 4.5–6 µm including encrustation, projecting up to 50 µm, with or without a slight basal swelling (up to 6.5 µm diam.), terminal, with thick hyaline cell wall and an outer hyaline crystal sheath covering the whole cystidium except the tapering, thin-walled apex. Crystal protrusions on cystidium are large and mostly rounded and sparsely arranged in longitudinal rows.

Basidia subclavate to suburniform, 15–20 × 4–5 µm, thin-walled, with 4 sterigmata and a basal clamp, often with a hyaline crystal collar at the base. Basidiospores broadly fusiform, L=(8.5–)8.7–11.2(–11.6) µm, W= 3.5–4.2(–4.4) µm, Q=(2.3–)2.4–3.0(–3.2), N=31/1, with minute apiculus, smooth, thin-walled, hyaline, occasionally with oil drops, negative in Melzer’s reagent.

With its hirsute hymenium which has numerous large cystidia, the species is similar to S. robustius, but differs by broader basidiospores and more rounded single crystals on cystidia.