Pluteus septocystidiatus

Pluteus septocystidiatus Ševˇcíková, Antonín & Boroviˇcka

Index fungorum number: 808469

Pileus 10–25 mm diam. plano-convex with slightly depressed at center, striate at margin, otherwise smooth, glabrous, chocolate brown (6F4) at disc, brown (6E4–5) slightly paler towards margin. Context thin, soft, white. Lamellae free subdistant with 2–3 series of lamelluae, dark blond (5D4). Stipe 20–40 × 3–4 mm. cylindrical, central, hollow, finely floccose-tomentose half way from base, white. Basidiospores 6–7 × 5–6 µm(x = 6.70 ± 0.46 × 5.60 ± 0.50, Q = 1.09–1.40, q = 1.20 ± 0.08, s = 1) subglobose to broadly ellipsoid, smooth, hyaline, inamyloid, thick-walled. Basidia 20–23 × 7–8 µm, clavate, thin-walled, 4-spored, unclamped. Lamellar edge sterile. Cheilocystidia common, 26–47 × 16–28 µm, broadly clavate to vesiculose, hyaline, inamyloid, thin-walled. Pleurocystidia common, 35–75 × 9–14 µm, fusiform, narrow fusiform, clavate, multiseptate, hyaline to pale yellow, inamyloid, relatively thick-walled. Pileipellis a cutis, hyphae 5–10 µm diam., cylindrical, with pale brown cytoplasmic pigment, inamyloid, thin-walled. Pileus trama interwoven. Lamellar trama convergent, cylindrical, hyaline, inamyloid, non-gelatinous, thin-walled. Stipitipellis a cutis, hyphae 3–12 µm diam., cylindrical, hyaline, inamylid, non-incrustrated, non-gelatinous, thin-walled. Caulocystidia absent. Clamp connections absent in the examined tissues.

Specimen examined: THAILAND, Sukhothai Province, Si Satchanalai National Park, on decaying wood, August, 2018, N. Wannathes, J. Kumla & N. Suwannarach, BKF 10212.

Habit, habitat, and known distribution: Solitary on decaying wood in bamboo thickets, deciduous dipterocarp-oak forests in South Korea, Thailand, and USA.

Notes: Pluteus septocystidiatus is characterized by appearing slightly depressed, brown, halfway striate pileus, white cylindrical stipe, subglobose to broadly ellipsoid basidiospores with mean dimensions of 6.7 × 5.6 µm, thick-walled multiseptate pleucystidia without hooks, and a cutis pileipellis. From the protologue, P. septocystidiatus has been described as being from the Republic of Korea and has been determined to be distinct from P. albostipitatus, a closely related species sharing similar morphology and ITS sequences, by the formation of obvious multiseptate and thick-walled pleurocystidia. The material from Thailand matches quite nicely with the description of the holotype. However, the Thailand collection expands knowledge about a variability in the basidiospore size of this species.