(1.3) Scleroderma cepa Pers.,

Synopsis Methodica Fungorum (Göttingen) 1: 155 (1801)

(Fig. 5)

Description:— Basidiomata small to medium-sized, 28–54 mm in diameter, 23–33 mm in height, subglobose to tuberiform, mostly sessile, rarely shortly stipitate; odor unknown; taste unknown. Peridium leathery, 1–2.5 (3) mm thick, merino white (#F9F5EC), lotus-root orange (#F5E9D9) to butter orange (#F2DF8F), usually without a color change after damaged or turning reddish after damaged, with thin, flaky, concolorous or dull dirty orange (#EBD087) to light brown (#B39966) squamules. Gleba compact at first, becoming pulverulent, flint brown (#736960) to dull black (#0B0C0E). Basal rhizomorphs abundant, whitish to yellowish.

Basidiospores {40/2/2} 12.5–16 (17.5) [14.26 ± 1.17, 13.50] µm in diameter including ornamentation, mostly globose, rarely subglobose, thick-walled, with echinulate to subreticulate ornamentation 1–2 µm high, brownish to purplish, often surrounded by remnants of placental cells. Basidia collapsed. Gleba trama composed of 2–5.5 μm wide, thin-walled to slightly thick-walled, nearly colorless to slightly brownish, compact, moderately branching, subregularly arranged to interwoven hyphae without clamp connections. Peridial squamules composed of 3–6 μm wide, slightly thick-walled, brownish, moderately compact, moderately to frequently branching, subregularly arranged to interwoven hyphae without clamp connections. Peridial trama composed of 3–6.5 μm wide, slightly thick-walled, nearly colorless to slightly brownish, compact, moderately to frequently branching, subregularly arranged to interwoven hyphae without clamp connections.

Habits and distribution:— Gregarious, on soil, usually in subtropical forests, associated with plants of Fagaceae, Juglandaceae and Pinaceae. Currently known from Asia (China, Japan, South Korea & Thailand), Europe (Germany, Poland, Portugal & UK) and North America (Mexico & USA) with molecular evidence.

Collections examined:— China, Chongqing Municipality, Bishan District, exact location unknown, June 7, 2023, Huan Wang, Kun L. Yang et al., S23123 (HTBM0366). China, Sichuan Province, Guang’an City, Linshui County, exact location unknown, June 19, 2023, Zhi Ci Liu Nian, Kun L. Yang et al., S23171 (HTBM0414).

Notes:— As confirmed in the current phylogeny (Fig. 1), this species is widely distributed across Asia, Europe and North America. Several collections labeled as “ Scleroderma laeve ” from Asian countries (China, Japan & South Korea) clustered with S. cepa collections (Fig. 1) are regarded as misidentifications here, because S. laeve is originally known from Africa and Europe (Lloyd 1916) but without collections from these regions for support in the current phylogeny. Even if S. cepa and S. laeve are synonymized with each other, S. cepa should be adopted on account of the priority.

Scleroderma cepa is a distinct member of the sect. Scleroderma that shows larger basidiomata with a relatively thick peridium. It is poisonous, causing gastroenteritis and psycho-neurological disorder (Bau et al. 2024). Given its macromorphology so similar to the edible species S. yunnanense, this species has been frequently misidentified as the latter and accidently eaten by the public in China. According to the data from Chinese Center for Disease Control and Prevention, S. cepa did cause at least 24 mushroom poisoning incidents involving at least 82 patients in the recent five years (2019–2023) in China (Yang et al. 2024).