Fomitopsisbambusae is characterised by resupinate to effused-reflexed or pileate, soft corky basidiocarps with bluish-grey pores, small pores measuring 6–9 per mm, cylindrical to oblong ellipsoid basidiospores measuring 4.2–6.1 × 2–2.3 μm and growing on dead bamboo.

China. Hainan, Haikou, Jinniuling Park, on dead bamboo, 18.XI.2020, Yu-Cheng Dai leg., Dai 22116 (holotype BJFC036008).

Bambusae (Lat.): refers to the species growing on bamboo.

Basidiocarps annual, resupinate to effused-reflexed or pileate, separable from the substrate, without odour or taste and soft corky when fresh, corky and light in weight when dry. Pilei semicircular, projecting up to 1 cm, 1.5 cm wide and 5 mm thick at base; resupinate part up to 14 cm long, 6 cm wide and 2 mm thick at centre. Pileal surface bluish-grey when fresh, pale mouse-grey to greyish-sepia when dry, glabrous to slightly velutinate, rough, azonate; margin acute, incurved when dry. Pore surface bluish-grey to pale mouse-grey when fresh, becoming mouse-grey to dark grey when dry; sterile margin up to 1 mm wide; pores round to angular, 6–9 per mm; dissepiments thin, entire. Context white to cream, corky, up to 3.5 mm thick. Tubes paler than pore surface, corky, up to 1.5 mm long.

Hyphal system dimitic; generative hyphae bearing clamp connections; skeletal hyphae IKI–, CB–; tissue unchanged in KOH.

Generative hyphae hyaline, thin- to slightly thick-walled, occasionally branched, 1.5–3 μm in diam.; skeletal hyphae dominant, hyaline, thick-walled with a narrow lumen to subsolid, occasionally branched, interwoven, 2–4.5 μm in diam.

Generative hyphae hyaline, thin- to slightly thick-walled, rarely branched, 1.5–2.5 μm in diam.; skeletal hyphae dominant, hyaline, thick-walled with a narrow lumen to subsolid, occasionally branched, flexuous, interwoven, 2–3 μm in diam. Cystidia absent; fusoid cystidioles present, hyaline, thin-walled, 11–18 × 2.5–4 μm. Basidia short clavate to barrel-shaped, bearing four sterigmata and a basal clamp connection, 13–19 × 4.5–5.5 μm; basidioles dominant, in shape similar to basidia, but smaller.

Basidiospores cylindrical to oblong ellipsoid, hyaline, thin-walled, smooth, IKI–, CB–, (4–)4.2–6.1(–6.5) × (1.9–)2–2.3(–2.6) µm, L = 4.917 µm, W = 2.109 µm, Q = 2.26–2.41 (n = 90/3).

Brown rot.

China. Hainan, Haikou, Jinniuling Park, on dead bamboo, 7.XI.2020, Yu-Cheng Dai leg., Dai 21942 (BJFC035841), 18.XI.2020, Dai 22104 (BJFC035996), Dai 22110 (BJFC036002) and Dai 22114 (BJFC036006).