Tylocinum griseolum Yan C. Li & Zhu L. Yang, in Wu et al., Fungal Diversity 81: 100 (2016)
Etymology: The epithet ‘‘griseolum’’ refers to the grayish color of the pileus.
Pileus 1.8–4 cm in diam., hemispherical to applanate, gray (20C1) to dark gray (20F1), much paler towards margin, surface covered with granular-like, fibrillose or tomentose squamules, dry; context soft when mature, white to pallid, without discoloration when bruised. Hymenophore depressed around apex of stipe; hymenophoral surface white when young, pallid to dirty white when mature; tubes concolorous with hymenophoral surface, without color change when injured; pores angular, up to 1.5 mm wide; tubes short, up to 4.5 mm long, without discoloration when bruised. Stipe 3.5–5 9 0.4–1 cm, cylindrical, concolorous with pileus, surface covered with concolorous granular-like squamules, without discoloration when touched; context white to pallid, without discoloration when bruised; basal mycelium pallid. Taste and odor mild.
Basidia 30–45 x 10–12 μm, clavate, 4-spored. Basidiospores (11) 12.0–14.5 (16) x 4.5–5.5 μm [Q = 2.60–3.22, Qm = 2.81 ± 0.13], oblong to subfusiform in side view, ellipsoid in ventral view, colorless to yellowish, smooth (under SEM). Hymenophoral trama boletoid; hyphae cylindrical, 3.5–11 μm wide. Cheilo- and pleurocystidia 50–60 x 11–14 μm, fusiform to subfusiform or clavate often with sharp apex and long pedicel, often containing yellowish pigments, thin-walled. Pileipellis a trichodermium composed of hyphae with 3–5 concatenated cells 5.5–22 μm wide, with termimal cells 46–72 x 11–21 μm. Pileal trama composed of interwoven hyphae 4–7 μm wide. Clamp connections absent.
Habitat: Scattered on soil in southern subtropical forests dominated by Lithocarpus spp. and Castanopsis spp.
Known distribution: Currently only known from southwestern China.
Additional specimens examined: CHINA, YUNNAN PROVINCE: Jinghong City, Dadugang Town, alt. 1350 m, 7 July 2006, Y.C. Li 455 (HKAS 50209); same location, 22 July 2007, Y.C. Li 925 (HKAS 52612).
Index Fungorum number: IF818493
Notes: Tylocinum griseolum is characterized by the gray to dark gray tomentose pileus, the soft and white to pallid pileal context, the trichodermium pileipellis, the relatively big hymenophoral pores (up to 1.5 mm wide), the verrucose stipe, the southern subtropical distribution, and the association with fagaceous plants. The tomentose pileus and soft pileal contex are similar to those in Xerocomus Quél., but species in the latter genus has a yellowish to yellow hymenophore and context, and an occasionally bluish discoloration when bruised. The white to pallid hymenophore in younger fruiting bodies and the dark verrucose stipe in Tylocinum are identical to those in Leccinum Gray. However, Leccinum is characterized by the fine hymenophore pores, and the solid context in the pileus. Phylogenetically, collections of Tylocinum formed a unique clade in our phylogenetic analyses. Thus, a new genus is proposed here based on morphological and molecular data.
Figure 1. Fresh basidiomata of representative species. a–c. Tylocinum griseolum (a-HKAS 50281, b-c-HKAS 52612)