Marasmius guyanensis Mont.
Pileus 0.5–3 mm diam, hemispherical to convex, umbilicate, with or without small dark reddish-brown papilla in umbilicus, striate; surface dull, dry, glabrous; disc brown (7E6–7), margin brownish-yellow. Context thin, yellowish-orange (4A6). Lamellae adnate to a collarium, distant (8–11) with no lamellulae, non-intervenose, narrow, yellowish-orange (4A6), non-marginate. Stipe 15–23 × 0.2–0.3 mm, central to eccentric, cylindrical, terete, tough, glabrous, insititious, dark reddish-brown overall; rhizomorphs present. Odour and taste not distinctive.
Basidiospores 10–12 × 3–4 mm [xmr = 10.3–11.9 × 3.1–3.9 mm, xmm = 11.1 ± 0.8 × 3.5 ± 0.4 mm, Q = 2.5–4.0, Qmr= 2.8– 3.6, Qmm = 3.2 × 0.4, n = 25 spores per 1 specimen], ellipsoid, smooth, hyaline, inamyloid, thin-walled. Basidia not observed. Basidioles clavate to cylindrical. Cheilocystidia common, of Siccus-type broom cells; main body 12–15 × 6–8 mm, cylindrical to pyriform, clavate or broadly clavate, rarely lobed, hyaline, thin-walled; apical setulae 1–2 × 0.8–1.0 mm, cylindrical to conical or irregular in outline, obtuse to subacute, hyaline to pale-yellow, inamyloid, thin-walled. Pleurocystidia absent.
Pileipellis hymeniform, mottled, composed of Siccustype broom cells; main body 12–19 7–17(–20) mm, pyriform to turbinate, subglobose or sometimes irregular in outline, rarely lobed, hyaline, inamyloid, thin-walled; apical setulae 2–4 × 1 mm, cylindrical to conical or irregular in outline, obtuse to subacute, brownish yellow, inamyloid, thin- to thick-walled. Pileus trama interwoven; lamellar trama interwoven; hyphae 3–5(–6) mm diam, cylindrical, smooth, hyaline, inamyloid, thin-walled, non-gelatinous. Stipe tissue monomitic; cortical hyphae 3–6 mm diam, parallel, cylindrical, smooth, light brown to brown, inamyloid, thick-walled (> 1 mm), non-gelatinous; medullary hyphae 2–5 mm diam, parallel, cylindrical, smooth, hyaline to pale-yellow, inamyloid, thin-walled. Caulocystidia absent. Clamp connections present.
Habitat: Scattered to gregarious on undetermined dicotyledonous leaves. Caribbean region, South America, Singapore, Thailand.
Material examined: Thailand: Chiang Mai Province: Chiang Mai University, 11 Aug. 2004, N. Wannathes 254 (CMU, SFSU).
Notes. The material from Thailand differs slightly from that described by Desjardin et al. (2000) from Indonesia in forming pilei with more brown tones and less orange tones, and in forming basidiospores that are slightly shorter (mean of 11.1 × 3.5 mm versus 12.1 × 3.6 mm). In other details, the two populations are similar.
Fig. 1 Marasmius guyanensis (N. Wannathes 254). (A) Basidiomes. (B) Basidioles. (C) Basidiospores. (D) Cheilocystidia. (E) Pileipellis. Bar: (A) 5 mm; (B–E) [ 10 mm.
Wannathes N, Desjardin DE, Lumyong S 2007– Mating studies, new species, and new reports of Marasmius from northern Thailand. Mycological Research 111: 985-996. https://doi.org/10.1016/j.mycres.2007.06.013