Collybiopsis gibbosa (Corner) R.H. Petersen, Mycotaxon 136(2): 342 (2021) FIGURE 4

Index Fungorum number: IF556187

Pileus 16–26 mm diam., convex, margin decurved, non-striate, eroded and split in age, dull, dry, appressed-fibrillose, disc grayish orange to reddish orange (6–7B6–8), margin light orange to grayish orange (5–6A–B4–5). Context 1–2 mm thick, soft, white. Lamellae adnate with a short decurrent tooth, close with 2-3 series of lamellulae. Stipe 38–46 × 2.5–4 mm, central, cylindrical, stuffed, non-insititious; surface dull, dry, glabrous, apex pale orange to light orange (5A3–4), base brownish orange (6C6–8).

Basidiospores [50/2/2] 8–9.5 × 4–4.5(5) μm [x̄ = 8.51 ± 0.48 × 4.27 ± 0.33 µm, Q = 1.7–2.25, Q m = 2.02 ± 0.17], ellipsoid, smooth, hyaline, inamyloid, thin-walled. Basidia 22–30 × 5.5–7 μm, clavate, 4-spored, thin-walled, hyaline, inamyloid. Pleurocystidia absent. Cheilocystidia scattered, 24–51 × 4–8 μm, irregularly cylindrical, with or without a few knob-like outgrowths, hyaline, inamyloid, thin-walled. Pileipellis a cutis of radially arranged hyphae 4–7 μm diam., cylindrical, smooth or brown-incrusted, yellowish brown to brown, inamyloid, weakly gelatinous, thin-walled; terminal cells repent, similar to the cheilocystidia. Pileus trama interwoven to radially arranged; hyphae 4.5–10 μm, cylindrical, hyaline, inamyloid, non-gelatinous, thin-walled. Lamellar trama regular; hyphae 3–12 μm, cylindrical or inflated, hyaline, inamyloid, non-gelatinous, thin-walled. Stipitipellis a cutis with scattered caulocystidia; 3–6.5 μm wide, cylindrical, non-diverticulate, smooth, hyaline to pale brown, inamyloid, non-gelatinous, thin-walled; medullary hyphae 4–8 μm diam., hyaline, otherwise like cortical hyphae. Caulocystidia repent, similar to the cheilocystidia. Clamp connections present.

Habitat and known distribution:—Fruiting scattered to gregarious on soil. Known from Africa (São Tomé) (Desjardin & Perry 2017), Australia, Brazil (Petersen & Hughes 2021), USA (Hawaii) (Desjardin et al. 1999), Singapore (Corner 1996), Thailand (This study), and Indonesia (Java) (Wilson et al. 2004).

Material examined:— THAILAND, Chiang Mai Province, Chiang Mai University, 18°48´7´´N 98°57´23´´E, elevation 330 m, on soil, 10 August 2022, W. Phonrob SDBR-CMUWP051 ; Phatthalung Province, Thaksin University, Phatthalung Campus, 7°48´39´´N 99°56´44´´E, elevation 19.47 m, on soil, 24 October 2022, P. Nutaratat, J. Kumla, and N. Suwannarach, SDBR-TSU053 .

Note:—Macroscopic and microscopic features of Thai materials were well agreed with Corner (1996) and Desjardin & Perry (2017). Thai materials were clustered together with C. gibbosa in both phylogenetic trees of the combined analysis of ITS and nrLSU regions, as well as, in the ITS region (FIGURES 2 and 3). Morphologically, C. gibbosa is similar to C. brunneigracilis; however, C. brunneigracilis possesses larger dark reddish brown pileus (28–53 mm diam), longer basidiospores (8–13.6 × 4–6.1 μm), and without caulocystidia (Wilson et al. 2004).