Grammatus labyrinthinus H.S. Yuan & Decock, in Yuan et al., MycoKeys 35: 32 (2018)
Etymology. labyrinthinus (Lat.): refers to labyrinthine hymenophore.
Diagnosis: Basidiocarps annual, resupinate, coriaceous, without special odour or taste when fresh, corky when dry, up to 15 cm long, 3 cm wide and 0.2 mm thick. Hymenophoral surface cream to pale buff when fresh, cinnamon-buff to yellowish-brown upon drying, firstly irregularly irpicoid to subporoid, the separate plates grow laterally and then develop into labyrinthine to sinuous pores, mostly 4–5 per mm, dissepiments thin; sterile margin up to 0.2 mm wide, pale yellow. Subiculum very thin (ca. 0.1 Hyphal structure. Hyphal system dimitic; generative hyphae bearing clamp connections, skeletal hyphae IKI–, CB+; tissue unchanged in KOH.
Subiculum. Dominated by skeletal hyphae; generative hyphae hyaline, thin-walled, rarely branched, 1.5–2.8 µm diam; skeletal hyphae hyaline, thick-walled to subsolid, straight to flexuous, covered by fine crystals, occasionally branched, interwoven, 1.8–3 µm diam. Tubes. Generative hyphae infrequent, hyaline, thin-walled, rarely branched, 1.5–2.5 µm diam; skeletal hyphae dominant, hyaline, thick-walled to subsolid, moderately branched, interwoven, 1.8–2.8 µm diam. Skeletocystidia numerous, clavate, thickwalled, originating from and tightly embedded in trama, upper part heavily encrusted, 10–30 × 4–8 µm (with encrustation). Dendrohyphidia present, especially along the dissepiments, arising from generative hyphae, thin- to slightly thick-walled, apically moderately to strongly branched. Basidia subglobose, longitudinally septate, already septate as probasidia, 18–25 × 10–13 µm, epibasidia divided into four parts up to 20 µm long, bearing four sterigmata and without clamp connection at the base, sterigmata up to 20 µm long.Basidiospores. Oblong-ellipsoid to cylindrical, hyaline, thin-walled, smooth, IKI–, CB–, (13–)13.3–15.7(–16) × (6–)6.4–7.4(–7.7) µm, L = 14.4 µm, W = 6.94 µm, Q = 2.07–2.1 (n = 60/2). Type of rot. White rot.
Index Fungorum number: IF825393
Figure 1. Maximum likelihood tree illustrating the phylogeny of Grammatus labyrinthinus and related taxa in Auriculariales, based on the combined ITS + nLSU sequence dataset. Branches are labelled with maximum likelihood bootstrap higher than 50%, parsimony bootstrap proportions higher than 50% and Bayesian posterior probabilities more than 0.95