Species diversity and taxonomy of Scytinostroma sensu stricto (Russulales, Basidiomycota) with descriptions of four new species from China Author Li, Yue https://orcid.org/0000-0003-4091-1506 School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China Author Xu, Wei-Qi https://orcid.org/0009-0000-5675-386X School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China Author Liu, Shi-Liang https://orcid.org/0000-0001-7556-2575 State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China Author Yang, Ning https://orcid.org/0009-0007-6900-5669 Beijing Municipal Research Institute of Eco-Environmental Protection, Beijing 100037, China Author He, Shuang-Hui https://orcid.org/0000-0003-4702-3034 School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China heshuanghui@bjfu.edu.cn text MycoKeys 2023 2023-06-13 98 133 152 http://dx.doi.org/10.3897/mycokeys.98.105632 journal article http://dx.doi.org/10.3897/mycokeys.98.105632 1314-4049-98-133 9B30833B688B54BABFE577817700CC53 Scytinostroma boidinii Yue Li, S.L. Liu & S.H. He sp. nov. Figs 4 , 5 Type . China , Beijing , Mentougou District , Xiaolongmen Forest Park , on dead angiosperm branch, 28 August 2020 , He 6911 (BJFC 033860, holotype ) . Figure 4. Basidiomes of Scytinostroma boidinii a He 6911 (BJFC 033860, holotype ) b He 4985 (BJFC 024503) c He 7465a (BJFC 038600) d He 7465b (BJFC 038601). Scale bars: 1 cm ( a-d ). Figure 5. Microscopic structures of Scytinostroma boidinii (from the holotype He 6911) a basidiospores b basidia c basidioles d gloeocystidia e skeletal hyphae from hymenium f skeletal hyphae from subiculum. Scale bars: 10 µm ( a-f ). Etymology. Named to honor Dr. Jacques Boidin (Lyon, France) who contributed much to the taxonomy of Scytinostroma . Fruiting body. Basidiomes annual, resupinate, widely effused, closely adnate, inseparable from substrate, membranaceous to coriaceous, first as small patches, later confluent up to 9 cm long, 3.5 cm wide, up to 300 µm thick in section. Hymenophore smooth, pale yellow (4A3), greyish yellow (4B4) to greyish orange [5B(3-4)], unchanged in KOH, not cracked; margin thinning out, adnate, fimbriate, white or concolorous with hymenophore surface. Context pale yellow. Microscopic structures. Hyphal system dimitic. Context thickening, compact. Generative hyphae rare, scattered, simple-septate, colorless, slightly thick-walled, 2-3 µm in diam., IKI-, CB-. Skeletal hyphae dominant, colorless to yellow, distinctly thick-walled, moderately branched, 1.5-2 µm in diam., dextriniod, CB+. Catahymenium composed of skeletal hyphae, gloeocystidia, basidia and basidioles. Skeletal hyphae abundant, similar to those in the context, but strongly dextrinoid, dichotomous-branched with acute tips, 1-1.5 µm wide at lowest part. Gloeocystidia abundant, subcylindrical to subfusiform, colorless, slightly thick-walled, with or without contents, weakly SA+, 50-80 x 5-10 µm . Basidia subclavate to subcylindrical, thin-walled, colorless, smooth, with four sterigmata and a basal simple septum, 30-50 x 4-7 µm ; basidioles in shape similar to basidia, but slightly smaller. Basidiospores subglobose, with a distinct apiculus, thin-walled, colorless, smooth, occasionally with oil-drops, amyloid, CB-, (4.5-) 5-5.5 (-6.5) x (4-) 4.5-5.5 (-6.2) µm , L = 5.1 µm , W = 5.0 µm , Q = 1.02-1.04 (n = 60/2). Additional specimens examined. China , Beijing , Mentougou District , Lingshan Scenic Spot , on dead angiosperm branch, 10 April 2022 , He 7465a (BJFC 038600) & He 7465b (BJFC 038601) ; Gansu Province , Tianshui County , Dangchuan Forest Farm, on dead Quercus tree, 9 August 2015 , He 2499 (BJFC 020952) ; Hebei Province , Xinglong County , Wulingshan Nature Reserve , on dead angiosperm branch, 2 September 2017 , He 4985 (BJFC 024503) ; Jilin Province , Jiaohe County , forestry experimental area, on fallen angiosperm trunk, 3 September 2017 , He 5138 (BJFC 024656) . Notes. Scytinostroma boidinii is characterized by the relatively long gloeocystidia and subglobose basidiospores. In the phylogenetic tree (Fig. 1 ), S. boidinii formed a distinct lineage sister to S. alutum Lanq., which differs in having cracked basidiomes, slightly larger basidiospores (5-7 x 5-7.5 µm ) and a distribution in France, Spain and Pakistan ( Boidin and Lanquetin 1987 ; Bernicchia and Gorjon 2010 ). Scytinostroma yunnanense C.L. Zhao from Yunnan Province, southwestern China, has similar-sized basidiospores (4.5-5.5 x 4.2-5.2 µm ) to S. boidinii , but differs in having white to cream hymenophore, smaller gloeocystidia (28-33 x 4-5 µm ) and smaller basidia (21-28 x 4-5.5 µm , Wang et al. 2020 ).