Adustochaete tribulata Spirin & Ryvarden sp. nov.

Fig. 15 G

Holotype.

Uganda • Kabarole: Kibale National Park, Makere University Field Station, dead, partly corticated branches, 20 Apr 2002, Ryvarden 44803 * (O, isotype – H).

Etymology.

Tribulatus (Lat., adj.) – sharpened.

Description.

Basidiomata annual, effused, gregarious, up to 2 cm in the longest dimension, arid, rather soft, 0.05–0.1 mm thick. Hymenial surface spinulose, cream-colored to grayish, spines rather regularly distributed, sharp-pointed, 60–200 × 40–50 μm, 8–10 per mm. Margin pruinose, white to cream-colored, adnate, up to 0.5 mm wide.

Hyphal structure monomitic, hyphae clamped; subicular hyphae hyaline, slightly thick-walled, subparallel, tightly agglutinated, not encrusted, 2–4 μm in diam., subhymenial hyphae hyaline, thin- to slightly thick-walled, interwoven, rather loosely arranged, 2–3 μm in diam., occasionally inflated up to 5 μm in diam., hyphae of hymenial spines hyaline, slightly thick-walled, ascending, CB (+), some irregularly inflated, 1.5–3.5 μm in diam. Crystals abundant in all parts of basidiomata, encrusting hyphae and hymenial cells, small, angular or sand-like. Cystidia occasionally present, hyaline or grayish-brownish, thin- to slightly thick-walled, clavate to broadly clavate or somewhat tapering, sometimes sinuous, predominantly embedded, 15–30 × 6–12 μm. Hyphidia abundant, dominating in hymenial layer, hyaline, slightly or distinctly thick-walled, CB (+), originating from subtend subhymenial hyphae, frequently dichotomously branched, 1–1.5 μm in diam. at the very apex, richly encrusted by small, densely arranged crystals. Basidia four-celled, ellipsoid-ovoid to nearly obconical, sessile, (12.5 –) 13–17 (– 17.5) × (9.3 –) 9.7–12.1 (– 12.2) μm (n = 23 / 1), thin-walled or with a distinct wall, embedded or exposed, sterigmata up to 15 × 3–3.5 μm. Basidiospores thin-walled, narrowly cylindrical to cylindrical, clearly curved, (11.4 –) 12.1–17.0 (– 17.2) × (4.8 –) 5.0–5.8 (– 6.1) μm (n = 30 / 1), L = 14.85, W = 5.30, Q = 2.82.

Remarks.

Adustochaete tribulata is macroscopically similar to two other whitish Adustochaete species described above, viz. A. minuta and A. nivea. It differs from them in having firm, abundant, richly branched and encrusted hyphidia dominating in the hymenial layer. Adustochaete tribulata is the single spinulose Adustochaete species so far detected in Africa. It is currently known only from the type locality in Uganda.