Lactifluus venosellus Silva-Filho, Sá & Wartchow, sp. nov. (Figs. 4–5–6b,c) Mycobank:—MB832852 Genbank accession nrITS: MK929292 Type:— BRAZIL. Paraíba: Mamanguape, Reserva Biológica Guaribas, 6°44’27.89” S 35°8’53.82” W, on soil, 30 June 2012, M.C.A Sá MS37 (UFRN-fungos 2197 holotype). Diagnosis:—Distinguished from other species by:pileus convex to slightly depressed, plane-depressed,infundibuliform, surface slightly velutinous, rivulose, reddish brown; lamellae slightly decurrent, distant. Basidiospores 8‒9 × 6‒7 µm, broadly ellipsoid to ellipsoid; ornamentation up to 0.3 µm high, composed of irregular short ridges; cystidia absent; scattered to abundant cylindrical, fusoid to slightly fusiform pseudocystidia; pileipellis a palisade with scattered lactifers, and an unique ITS sequence. Description:—Pileus 20–40 mm, convex slightly depressed, becoming plane-depressed to infundibuliform, reddish brown (8E4) with dark brown (8F7) spots; surface slightly velutinous, rivulose near margin, slightly cracked, dry, dull; edge even to slightly eroded, incurved (Figs. 4a–c); context firm, 4–5 mm at the disc, very thin towards margin, pastel red (7A4), unchanging (Fig. 4c). Lamellae short decurrent, distant, brownish (7D5/6); edge even, concolorous with the face; lamellulae frequent with two lengths, sometimes forked. (Figs. 4a–c). Stipe 15–20 × 7–9 mm, central, cylindric, equal to tapered to the base, dry, reddish brown (8E4), dull red (8B3) sometimes with brown (6E6) spots; surface smooth, sometimes veined (Figs. 4a–c); context solid. Veil absent. Latex not found. Odor and taste not determined. Basidiospores (7.5‒)8‒9(‒10) × (5.5‒)6‒7(‒7.5) µm; L = 8.5 µm, W = 6.5 µm; Q = 1.18‒1.47, Qm = 1.37; broadly ellipsoid to ellipsoid, thin-walled, hyaline; ornamentation amyloid, up to 0.3 µm high, composed of irregular short ridges and warts; plage non-amyloid; hilar appendix up to 1 µm long (Figs. 5a, 6b,c). Basidia 53.5‒80 × 6–8 µm cylindrical to slightly clavate, 4-spored, thin-walled, hyaline, sometimes with refractive contents; sterigmata up to 6 µm high (Fig. 5b). Pleuromacrocystidia absent. Pleuropseudocystidia abundant, 5.5‒10 µm diam., cylindrical to slightly fusiform, thin-walled, with refractive contents; projecting up to 35 µm above the hymenium; arising deeply from hymenophoral trama (Fig. 5c). Lamellae edge sterile, composed of scattered cheilopseudocystidia and common marginal cells: cheilopseudocystidia 4‒8 µm diam., cylindrical and fusoid, thin-walled, with refractive contents, projecting up to 18 µm above the hymenium, arising deeply from hymenophoral trama (Fig. 5d); marginal cells 28–35 × 7.5–7 µm, clavate, cylindro-clavate, sphaeropendunculate, catenulate, sometimes flexuous, thin-walled, hyaline (Fig. 5e). Hymenophoral trama composed of abundant sphaerocytes 9‒17 µm diam. and frequent, thin-walled, 7–12 µm wide lactifers. Pileipellis a palisade up to 85 µm thick, composed of isodiametric cells with cylindrical, clavate and obclavate terminal cells and scattered lactifers: isodiametric cells, 9–22 µm diam., thin-walled; lactifers, 7‒10 µm diam., with refractive contents, sometimes emergent, arising deeply from pileus trama (Figs. 5f,g); terminal cells 12.5– 50 × 3.5–11.5 µm, cylindrical, clavate sometimes obclavate, thin-walled, hyaline (Fig. 5g). Pileus trama composed of abundant sphaerocytes 6–21 µm diam., cylindrical hyphae, 2‒5 µm diam., and frequent to abundant, 7‒12 µm wide, thin-walled lactifers,. Stipitipellis a palisade similar to pileipellis. Clamp connections absent from all tissues examined. Etymology:—From Latin ‘venosellus’ (with small veins), in reference to the veined surface of the pileus. Habitat:—Scattered, on sandy soil, in a savanna area of Atlantic forest, under unknown host, but growing surrounded by the following tree species: Coccoloba alnifolia, C. laevis, C. mollis, C. ramosissima, and C. scandens. Distribution:—Known only from type locality. Materials examined:— BRAZIL. Paraíba: Mamanguape, Reserva Biológica Guaribas, 5 July 2015, FW 15/2017 (JPB). Aditional material examined:— Lactifluus brasiliensis: BRAZIL. Amazonas: Manaus, road Manaus-Caracaraí Km 45, 28 February 1978; St. John, Araujo and R. Singer B10729 (holotype INPA 77475), ibid., 12 January 1979, R. Singer B 11479 (paratype INPA 82380). Comment:— Lactifluus venosellus also belongs to Lf. subg. Pseudogymnocarpi based on molecular and morphological evidence. In our phylogeny Lf. venosellus clusters with five undescribed South American species, and forms a branch in Lf. sect. Polysphaerophori. The collection (TH7677) from Guyana was identified as Lf. aff. brasiliensis. Lactifluus brasiliensis, as mentioned above, perhaps belongs to Lf. subg. Pseudogymnocarpi (Singer et al. 1983). Both species share a similar pileipellis structure, but Lf. brasiliensis differs in the larger pileus (20–40 mm diam.) and stipe (15–20 × 7–9 mm) (Singer et al. 1983). We also analyzed the holotype and paratype of Lf. brasiliensi s, which possess globose to broadly ellipsoid basidiospores with higher ornamentation (up to 1 µm high); they lack pleuropseudocystidia. ‘ Lactifluus rupestris ’ described from Caatinga, is distinguished from Lf. venosellus by a larger pileus (60–70 mm) with red tint, larger stipe (35–45 × 18–21 mm), crowded lamellae, scarce pleuropseudocystidia and a trichoderm as pileipelis (Wartchow & Cavalcanti 2010).

Published as part of Silva-Filho, Alexandre G. S., Sá, Mariana C. A., Komura, Dirce L., Moncalvo, Jean-Marc, Margaritescu, Simona, Roy, Mélanie & Wartchow, Felipe, 2020, Two novel species of Lactifluus subg. Pseudogymnocarpi (Russulaceae) from Brazil, pp. 222-236 in Phytotaxa 436 (3) on pages 227-230, DOI: 10.11646/phytotaxa.436.3.2, http://zenodo.org/record/13874368