Differs from all other Subulicystidium species by cystidia which bear few spaced and irregularly located crystals and have a thick cell wall.

COLOMBIA. Cundinamarcha: 23rd kilometre of a highway from Medellin (direction SE) to Tenjo, alt 2600 m, 6.0605, -75.4095, on dead twig, 4 Jun 1978, L.Ryvarden (LR 15483 in O:F 918488).

rarocrystallinum (Lat.), having few spaced crystals on cystidium.

Basidiomata annual, effused, resupinate, fragile, porulose, thin, adnate. Hymenophore smooth, finely velutinous due to numerous protruding cystidia, whitish. Margin thinning out, adnate.

system monomitic. All septa with clamps. Subiculum thin, compact, with richly branched hyphae 3–3.5 µm wide, thin-walled to slightly thick-walled, hyaline and smooth. Subhymenium thin, compact, with richly branched hyphae 3–3.5 µm wide, thin-walled, smooth. Cystidia subulate, 45–65(–80) × 3.7–5 µm including encrustation, projecting up to 50 µm, with especially thick-walled, occasionally slightly swollen (up to 5.5 µm), basal part, with outer hyaline crystalline sheath covering the whole cystidium except the tapering, thin-walled apex. Crystal protrusions on cystidium are moderately large, rectangular to rounded, rather sparse and allocated rather irregularly and mostly in the medial part.

Basidia suburniform, 11–15 × 4.5–5.5 µm, thin-walled, with 4 sterigmata and a basal clamp, without encrustation. Basidiospores cylindric, adaxial side slightly concave, L=(7.5–)8.0–10.5(–10.8) µm, W=(2.8)2.9–3.7(–3.8) µm, Q=(2.2–)2.5–3.2(–3.7), N=72/1, with minute apiculus, smooth, thin-walled, hyaline, negative in Melzer’s reagent.

The few spaced far from each other crystals on cystidium and thick cell wall of cystidium are peculiar. Furthermore, in the single collection studied, cystidia were relatively infrequent and subhymenium was more compact than in other species. Species can be distinguished from Subulicystidium brachysporum also by larger cylindric basidiospores.