Conobolbitina fuscoviolacea T. Bau & H. B. Song sp. nov.

Figs 2 E, 2 F, 3 C, 3 D, 6, 7

Etymology.

“ fuscoviolacea ” refers to the presence of dark violet pigmentation in the pileipellis.

Holotypus.

China • Jilin Province, Huadian City, Hongshi National Forest Park, 31 July 2025, 42°50'01"N, 127°07'57"E, alt. 487 m, T. Y. Zhang, ZTY 2573131 (FJAU 72931).

Diagnosis.

This species is characterized by a non-bulbous stipe base, ellipsoid to oblong basidiospores, a pileipellis becoming slightly pastel violet in KOH, and pileocystidia with apical, chocolate brown to terra brown pigmentation. The combination of these features distinguishes it from other Conobolbitina species.

Description.

Basidiomata small-sized. Pileus 2–3 cm in diameter, initially lentiform, later becoming straight, slightly subumbonate, plano-concave. Pileus center nut brown (RAL 8011) to sepia brown (RAL 8014), margin ivory (RAL 1014) to brown beige (RAL 1011). Pileus hygrophanous, smooth, viscid, with distinct striations extending up to 1 / 2 of the center; the margin even to slightly undulate. Context thin, light ivory (RAL 1015) to ivory (RAL 1014), with no specific odor or taste. Lamellae adnexed to narrowly adnate, ventricose, moderately crowded, unequal in length, beige red (RAL 3012), beige (RAL 1001) to ochre brown (RAL 8001), with serrulate edges. Stipe 2–3 cm long, 2–3 mm thick, cylindrical, light ivory (RAL 1015) to ivory (RAL 1014), surface covered with pruinose pubescence, with longitudinal fibrous striations, base is not swollen and is equal in diameter throughout.

Basidiospores (60 / 2 / 2) (6.9 –) 7.8–10.4 (– 11.2) × (4.4 –) 4.8–6.1 (– 6.6) μm, Q = (1.47 –) 1.54–1.76 (– 1.78), Q m = 1.65 (± 0.07), ellipsoid to oblong, slightly lemon-shaped in frontal view, with a slight suprahilar depression in lateral view. Appears smooth to slightly rough under a light microscope, with pointed ornamentation visible under a scanning electron microscope. Spore wall thick, containing oil droplets. Germ pore diameter less than 1.5 μm or inconspicuous. Basidiospores appear brown beige (RAL 1011) to clay brown (RAL 8003) in KOH solution. Basidia (17 –) 18–25 × (7 –) 8–11 μm, clavate, 4 - spored, occasionally 2 - spored, sterigmata 2–6 μm long, with vacuolar contents in basidia. Cheilocystidia (18 –) 22–43 (– 45) × 9–14 (– 15) μm, variable in shape, cylindrical and constricted at the center, broadly capitate, utriform, clavate, cylindrical, with bifurcated apices, nearly femoral head-shaped, some with excrescences, and sterile margins. Pleurocystidia absent. Caulocystidia (22 –) 23–60 (– 63) × 9–16 μm, variable in shape, similar to cheilocystidia but slightly larger, clavate, spheropedunculate, utriform, subcapitate, with bifurcated apices, nearly femoral head-shaped, some with excrescences. Pileipellis epithelioid hymeniderm, composed of (20 –) 21–42 (– 45) × 13–20 (– 21) μm sphaeropedunculate or broadly clavate elements, exhibiting red brown (RAL 8012) to pastel violet (RAL 4009) pigments. Pileocystidia (22 –) 24–50 (– 52) × 5–8 μm, clavate, subcylindrical, capilliform, some with apices pigmented chocolate brown (RAL 8017) to terra brown (RAL 8028). A gelatinous layer is present. All structures have clamp connections. A weakly positive reaction with ammonia solution is observed, resulting in the formation of rhomboid crystals.

Habitat.

It grows solitarily on decaying fir wood in summer.

Known distribution.

Jilin Province, China.

Additional specimens measured.

China • Jilin Province, Jilin City, Huadian City, 27 August 2023, 42°49'30"N, 127°08'17"E, alt. 483 m, H. Cheng, C 2382702 (HMJAU 65107).

Notes.

This species is distinguished from Con. lignicola and Con. glutinosa by the pastel violet reaction of its pileipellis in KOH and the chocolate brown to terra brown apical pigmentation on some pileocystidia (Horak and Hausknecht 2002). It differs from Con. viscosa and Con. sibirica by the latter two having distinctly olive-black pilei (Watling 1975; Crous et al. 2021). Phylogenetically, this species forms a sister group with Con. sibirica, but the latter originates from a log of Populus tremula L. and is phylogenetically distinct (Crous et al. 2021).