Lactocollybia variicystis D. A. Reid & Eicker

Lactocollybia variicystis D. A. Reid & Eicker, Mycotaxon 66: 159 Figs 3, 4 Description. Basidiomata small-sized, collybioid. Pileus 5–15 mm diam., convex when young, gradually becoming planoconvex on maturity; surface moist, smooth, hygrophanous; white to yellowish white (1 A 1–2), changing to greyish yellow (1–2 B 4) on drying or bruising; margin entire or rarely undulating, decurved. Lamellae adnate, white (1 A 1) changing to greyish yellow (1 B 4) on drying or bruising, crowded (25 L + l / cm at pileus margin); lamellulae present in 6 series; edge entire. Stipe 7.5–22.5 × 1.5–2.5 mm, mostly central to slightly eccentric, cylindrical; surface moist, smooth, hygrophanous; white to yellowish white (1 A 1–2), changing to greyish yellow (1–2 B 4 – 5) and darker on drying or bruising; basal mycelium white. Context in pileus up to 1.3 mm thick, white (1 A 1), unchanging on bruising, exposure, and in 3 % KOH; hollow in stipe, yellowish white (1 A 2), unchanging on bruising, exposure, and in 3 % KOH. Basidiospores (3.1) 4.4–5.4 – 6.9 × (2.3) 3.1–3.9 – 4.5 (5.1) μm [n = 30, Q = (1.04) 1.18–1.38 – 1.62 (1.7), ellipsoid, rarely subglobose; thin-walled, smooth, apiculate, uni-guttulate, hyaline in 5 % KOH, inamyloid, non-dextrinoid. Basidia 20.7–23 × 4.8–6.2 μm, clavate to subclavate, thin-walled, hyaline in 5 % KOH, non-dextrinoid, 4 - spored; sterigmata up to 5.5 μm long. Gloeocystidia abundant, more abundant on lamellae side, 24–32.6 × 3.2–6.2 μm, cylindrical to subcylindrical with mostly obtuse to sub-capitate apices, thin-walled, arising from the hymenophoral trama, yellowish brown in H 2 O and 5 % KOH, non-dextrinoid; emergent up to 6 μm. Pleurocystidia absent. Lamellae edge fertile, heteromorphous with basidia, basidioles, and cystidia. Cheilocystidia abundant, 22.4–34.3 × 4.4–6.8 μm, cylindrical to subcylindrical with mostly obtuse to sometimes sub-fusoid, sub-capitate to mucronate apices, thin-walled, hyaline in 5 % KOH, non-dextrinoid; emergent up to 13 μm. Subhymenium thin, up to 13 μm thick, subcellular with ramifying hyphae. Hymenophoral trama composed of compactly arranged, subparallel to parallel, thin-walled, septate hyphae and gloeohyphal elements; hyphae 3.5–6 μm wide. Pileipellis a cutis with interspersed pale brownish pigment; composed of shortly catenulate, sometimes branched hyphae with numerous scattered gloeocystidia; hyphae 2.4–4.5 μm wide with obtuse, sub-capitate to sub-fusoid apices, thin-walled, septate, hyaline in 5 % KOH, non-dextrinoid; gloeocystidia lageniform to fusoid, 26.5–65 × 7.6–10 μm, mostly attenuated at both ends, refractive, yellowish in H 2 O and 5 % KOH. Pileus trama composed of compactly arranged, interwoven hyphae and gloeohyphal elements; hyphae hyaline in 5 % KOH, non-dextrinoid. Stipitipellis a cutis; composed of uprising hyphae with numerous scattered gloeocystidia; hyphae 2.2–4 μm wide with obtuse to sub-capitate apices, thin-walled, septate, hyaline in 5 % KOH, non-dextrinoid; gloeocystidia lageniform to fusoid, 17.8–31.2 × 3.5–6.1 μm, often forked at apices, attenuated at base, refractive, yellowish in H 2 O and 5 % KOH. Stipe trama composed of compactly arranged, parallel hyphae and gloeohyphal elements; hyphae hyaline in 5 % KOH, non-dextrinoid. Clamp connections common. Materials examined. Thailand • Lampang Province: Mueang Lampang district, 18°21.79314'N, 99°17.05644'E, Alt. 399 m, gregarious on a Dipterocarpus sp. tree in semi-deciduous Dipterocarpus dominated forest, 18 th June 2023, I. Bera, IB 23 - L 02 (MFLU 24-0388); 18°21.80328'N, 99°17.0535'E, Alt. 402 m, gregarious on a Dipterocarpus sp. tree in semi-deciduous Dipterocarpus dominated forest, 23 rd August 2023, I. Bera, IB 23 - L 06 (MFLU 24-0389). Notes. The Thai Lactocollybia variicystis is characterized by its small-statured, smooth, and hygrophanous, white to yellowish-white pileus; adnate and crowded lamellae; uni-guttulate ellipsoid basidiospores; omnipresence of yellowish-brown gloeocystidia in the hymenium; pale brownish pigmented pileipellis; and numerous scattered lageniform to fusoid and yellowish gloeocystidia in the pileipellis and stipitipellis. Additionally, the greyish yellow color change on bruising or drying makes this species quite distinct. The subcellular with ramifying hyphal nature of subhymenium and abundant gloeocystidia and clamp connection undoubtedly placed this species in the sect. Albae (Singer 1986). In the phylogenetic analysis (Fig. 1), inclusion of two sequences retrieved from our collections (PQ 530286 and PQ 530287) within this clade suggests the identification of Thai sequences as L. variicystis. In that case, PQ 530286 and PQ 530287 represent the new record of L. variicystis from Thailand. The type specimen of L. variicystis was discovered from Salix stump in South Africa (Reid and Eicker 1998). Our specimens are similar to the type specimen in respect of the size and color of the basidiomata, hymenial gloeocystidia, and cheilocystidia (Reid and Eicker 1998). However, we found differences in some characters compared to the type specimen. The striate or plicate margin, adnexed attachment of lamellae, furcation in lamellae at margin sometimes, slightly larger (6.6–8 × 4–6 μm) and broadly amygdaliform basidiospores, quite larger gloeocystidia (150 × 11.6 μm), wider hyphae (4–11.6 μm) in pileipellis, and presence of caulocystidia of the type specimen (Reid and Eicker 1998) differentiated it from our studied Lactocollybia species. Certain morphological details, such as changes in basidiomata color upon bruising, lamellae spacing, and corresponding molecular data of the type specimen, are lacking for comparison with our studied L. variicystis.