Favolus gracilisporus H. Lee, N.K. Kim & Y.W. Lim, in Tibpromma et al., Fungal Diversity 83: 219, 2017

Basidiomes annual, attached by a short, rounded and undifferentiated lateral stipe, solitary or several form a branched base; pilei flabelliform to circular, up to 60 mm from the base to margin, up to 110 mm in width and 7 mm thick; upper surface azonate, fibrillose, radially striate, ivory to pale buff; margin concolorous or darker with age; hymenophore poroid, whitish or cream to pale brown, pores radially elongated, 2–2.5 mm long and 0.5–1 mm wide; dissepiments entire to slightly lacerate; tubes pale tan to ivory, corky, brittle when dry, up to 0.7 mm thick; context concolorous, continuous with the tube, homogenous, up to 5.5 mm thick. Stipe short, laterally attached to the pileus, buff, glabrous, with decurrent pores. Hyphal system dimitic with generative hyphae and skeleto-binding hyphae; generative hyphae hyaline in KOH, thin-walled, 3–4 μm in diam., septa with clamps, the thick-walled skeleto-binding hyphae aseptate, much branched, dominating in the basidiocarp, 3–6 μm in diam. Cystidia and cystidioles absent. Basidia clavate, 4–sterigmate, difficult to observe, 19–23 × 5–6 μm, with a basal clamp connection. Basidiospores cylindric to slightly allantoid, hyaline, smooth, IKI–, (7.40–)7.72–8.38(–8.76) × (3.14–)3.27–3.5(–3.69) μm, L = 8.1 μm, W = 3.3 μm, Q = 2.39 (n = 30).

Specimen examined – Hungary, Central Transdanubia, Komárom–Esztergom County, Komárom (N 47°43′15″, E 18°8′37″), leg. P. Jakab, 27 May 2016, on Celtis sp. trunk (BP 106942).

Phylogenetic tree obtained from ITS sequences. Maximum likelihood bootstrap values >70% are given at the branches. Bar indicates 0.05 expected change per site per branch.

Favolus gracilisporus basidiomes in the habitat (BP 106942). a–b pore surface. c–d pileal surface. Photographs by György Vrba

Microscopic structure of Favolus gracilisporus (BP 106942). a contextual skeletal-binding hyphae. b clamped generative hyphae and skeletal-binding hyphae in the trama. c basidia. d basidiospores.