雪白囊小伞

3.2.4 Cystolepiota nivalis T. Bau and X. Y. Zhou, sp. nov.
MycoBank number: MB 851388 (Figures 9, 10).
Diagnosis: The main distinguishing features of C. nivalis are the widely umbonate, white, farinose pileus, with a strongly appendiculate margin, with a farinose stipe and cystidia absent.
Etymology: “nivea” refers to snowy white pileus.
Type: China, Jilin province, Jiaohe City, Qianjin forest farm, August 25, 2023, coll. T. Bau and M. Liu (HMJAU68220), Holytype!
Description: Basidiomata small. Pileus 1.2–1.7 cm, hemispherical, then campanulate, with a broad umbo, with concolorous farinose squamules; margin appendiculate strongly farinose, concolorous with pileus; context thin, whitish. Lamellae free, crowded, white to light cream, unequal, with 1–3 tiers of lamellulae. Stipe 3.7–5.6 × 0.1–0.2 cm, central, subcylindrical to cylindrical, surface strongly farinose, white to cream, light brown (6D5–D8) to reddish brown (7E4–E8) towards the base. Annulus white, fugacious. Odorless, taste not recorded (Figures 9A–C, 10A).
Basidiospores [120,4,4] 3.8–4.7 (−4.9) × 2.0–3.0 μm, Q = 1.47–2.06 (−2.28), Qv = 1.85, ellipsoid to cylindrical, slightly thick-walled, smooth-walled under the LM and SEM, hyaline inamyloid, non-dextrinoid, metachromatic in cresyl blue, cyanophilous. Basidia 12–17 × 3.5–5 (−6) μm, clavate, 4-spored, sometimes 2-spored, hyaline. Lamellar trama regular. Pleurocystidia and cheilocystidia absent. Pileus and stipe covering composed of globose, subglobose, pyriform cells 8–36 μm in diam., or 9–25 × 4–12 μm, sometimes 2–5 cells connected in a string, thin-walled, hyaline. Clamp connections present in all structures (Figures 9D–F, 10B–D).
Habitat: Solitary to scattered in mixed forest.
Distribution: Found only in Jilin Province, northwestern China.
Additional specimens examined: China, Jilin province, Jiaohe City, Qianjin forest farm, August 25, 2023, coll. T. Bau and H. Cheng (HMJAU68219); Huadian City, Red Rock National Forest Park, August 27, 2023, coll. T. Bau and X. Y. Zhou (HMJAU68217, HMJAU68218).
Notes: Morphologically, P. petasiformis also has a white pileus with an obvious umbonate, but it is easy to distinguish from C. nivalis by its context turns pale orange after cut, and lacks clamp connections (Vellinga and Huijser, 1998; Yang et al., 2019).