Fungal Biodiversity Profiles 81 - 90 Wang, Xiang-Hua Das, Kanad Bera, Ishika Chen, Yu-Hui Bhatt, Rajendra Prasad Ghosh, Aniket Hembrom, Manoj Emanuel Hofstetter, Valérie Parihar, Arvind Vizzini, Alfredo Xu, Tai-Min Zhao, Chang-Lin Cryptogamie, Mycologie 2019 2019-08-27 20 5 57 95 6NSMC 2609086 X.H. Wang X. H. Wang 2019 [960,1257,825,852] Agaricomycetes Russulaceae Lactarius Fungi Russulales 19 74 Basidiomycota species exilis sp. nov.   ( Figs 9; 10B; 13) A small slender species with pileus with a conical center, white latex, globose reticulate spores, absence of pleuromacrocystidia, numerous cheilomacrocystidia and pileipellis a (hymeno)epithelium. A long INDEL in the ITS1 region is also characteristic.  TYPUS. —   China. Shanxi Prov., Xia Co., Sijiao, Tanghui, under   Quercustrees,  15.VIII.2015, coll. X.H. Wang, no. 3683( holo-, KUN[ HKAS 89954]!).  MYCOBANK. — MB 829288. GENBANK. — MK351982- MK351984(ITS).  ETYMOLOGY. — Referring to the slender fruiting bodies.  ADDITIONAL SPECIMENS EXAMINED. —  China. Henan Prov., Xinyang, Jigong Mt., between Laoyingwo and Xiannütan, 295 ma.s.l., 25.VIII.2015, coll. X.H. Wang, no. 3783(KUN[HKAS 90043]).   South Korea. Seoul, Donggureung Nine Royal Tombs, under  Quercustrees, 15.VIII.2011, coll. X.H. Wang, no. 2966( KUN[ HKAS73523]).  HABIT, HABITAT AND DISTRIBUTION. — Caespitose or 1-4 individuals growing together, in fagaceous forests. Northern ( Shanxi Prov.) and central ( Henan Prov.) Chinaand South Korea.   DESCRIPTION   Basidiomata Small, slender.   Pileus  6-15 mmin diam., at first convex with a pointed papilla, becoming plano-convex with a depressed center when mature, ± sulcate, margin sometimes crenate; surface dry, somewhat areolate-rimose, dark brown or dark reddish brown when young, later remaining so or becoming yellowish brown, orange brown, hygrophanous, radially rugose.  FIG. 13. —  Lactarius exilisX.H. Wang, sp. nov.(HKAS 89954, holotype): A, basidiospores; B, cheilomacrocystidia; C, lamella edge; D, pileipellis. Scale bars: A, 5 μm; B, 20 μm; C, D, 25 μm.   Context Very thin (< 0.5 mm), concolorous with the lamellae.   Lamellae  1-3mmbroad, decurrent, subdistant, pale yellow,grayish orange.   Stipe 20-40 × 1-2 mm, cylindrical, equal or gradually enlarged downward; surface dry, smooth, with silky luster, nearly concolorous with the lamellae or light brown.   Latex White, watery, neither discoloring nor staining.   Odor None.   Spore print Not obtained.   Basidiospores (80/4/3) 7.0-7.7-8.5 (9.0) × 6.5-7.2-8.0 (8.5) Μm [Q = 1.00- 1.12 (1.14), Q = 1.06 ± 0.03] [ holotype(40/2/1) 7.0-7.7-8.5 (9.0) × 6.5-7.3-8.0 (8.5) Μm, Q = 1.00-1.10 (1.14), Q = 1.06 ± 0.03], globose, subglobose; ornamentation 0.8-1.5 (2.0) Μm high, of ridges connected, forming an incomplete to complete reticulum, often with subtransparent (less amyloid) dots in the ridges or at the crossing points of ridges; plage not amyloid or slightly distally amyloid.   Basidia 4-spored, 35-52 × 8-13 Μm, clavate.   Pleuromacrocystidia Absent.   Pseudocystidia Uncommon to common, 2-4 Μm broad, often slightly enlarged at the apex, some forking.   Lamella edge Sterile, rarely with scattered basidia; cheilomacrocystidia numerous, 25-60 × 4-7 Μm, subfusiform, cylindrical, apex mostly mucronate or moniliform, with sparse to agglomerated contents.   Pileipellis An epithelium, 50-100 Μm thick; cells 15-30 Μm in diam., globose, ellipsoid, terminal cells often ellipsoid, colorless, hyphae beneath globose cells 5-10 Μm broad, colorless.   Stipitipellis A cutis, 40-50 Μm thick, closely packed; hyphae 3-5 Μm broad, pale yellowish brown.   Pileus and stipe trama With numerous rosettes.   NOTES The combination of pileipellis an epithelium, absence of pleuromacrocystidia and abundant cheilomacrocystidia of  L. exilisX.H. Wang, sp. nov., is shared by  L. castanopsidisand  L. resinosusX.H. Wang, sp. nov.(described below). Those two species have spores with deeply winged zebroid ornamentations and brownish hyphae underlying the pileipellis.  Lactarius exilisX.H. Wang, sp. nov., is similar to European  L. obscuratus,  L. cyathuliformisand  L. omphaliformisand Thai  L. crenulatulusWisitrassameewong & Verbekenin the slender habit and the pileipellis an epithelium. The three European species have pleuromacrocystidia and ellipsoid spores (Heilmann-Clausen et al.1998; Basso 1999). The Thai species lacks cheilomacrocystidia and has a more crenulate pileus and white pruinose stipe base ( Wisitrassameewong et al.2014). Japanese  L. cyathula f. japonicusHongolooks similar. It has bigger ellipsoid spores and lacks macrocystidia ( Hongo 1971). The long INDEL in the ITS1 region in  L. castanopsidis,  L. exilisX.H. Wang, sp. nov., and  L. resinosusX.H. Wang, sp. nov., is unique among the members of L.subg.  Russularia.This long INDEL is also present in several species of L.subg.  Lactariuswith violeting latex [e.g.  L. cascadensisHesler & A.H. Sm.and  L. luridus(Pers.) Gray]. Using the whole ITS or ITS1 region to BLAST gave hits to these not closely related species. 4077331308 2015-08-15 KUN X. H. Wang China Xia Co. Tanghui Sijiao 19 74 HKAS 89954 1 Shanxi Prov. holotype