All 24 sequences generated by the authors of specimens putatively identified as Russula albonigra, are placed within R. subg. Compactae and group together with other members of R. sect. Nigricantinae (Fig. 1). All but two of these sequences are placed in one strongly supported clade, here further referred to as the R. albonigra lineage. The two sequences outside the R. albonigra lineage are placed in either the R. atramentosa Sarnari clade or the R. anthracina Romagn. clade (these sequences were not used for the final analysis and are not shown in the trees). Our molecular analysis shows the presence of five distinct European species within the R. albonigra complex (Fig. 1). They form four well supported clades and one singleton collection on a long branch. The name R. albonigra is assigned to a clade with two collections from the Czech Republic, PRM 924409 and PRM 934322, that originate from the type collecting area. Three species, R. ambusta, R. nigrifacta and R. ustulata, are described here as new. One species is represented by a singleton position in the tree, placed as sister to R. albonigra and is labelled as Russula sp. 1. These two species form a sister clade to a larger clade containing R. ambusta, R. nigrifacta and R. ustulata. The relations within the latter clade are not well supported.
When searching for UNITE species hypotheses labelled as Russula albonigra, at every threshold, two species hypotheses are found that are not placed within the R. albonigra lineage defined by our multi-locus analysis. Both are represented by a singleton sequence. The first, UDB024525 (SH1188824.08FU, SH1300522.08FU, SH1425850.08FU, SH1569640.08FU, SH1740739.08FU and SH1961434.08FU at 3.0%, 2.5%, 2.0%, 1.5%, 1.0% and 0.5% threshold respectively) represents a collection from Lao People's Democratic Republic and seems more closely related to R. atramentosa. The second, JF908707 (SH1188856.08FU, SH1300551.08FU, SH1425887.08FU, SH1569689.08FU, SH1740802.08FU and SH1961540.08FU at 3.0%, 2.5%, 2.0%, 1.5%, 1.0% and 0.5% threshold respectively) represents a collection from Italy with an isolated position in the phylogeny (Fig. 2).
The general topology of the ITS tree is congruent with the multi-locus tree and all sequences of the R. albonigra lineage generated by the authors of this study are again placed within this monophyletic group (Fig. 2). The ITS analyses revealed the presence of three additional North-American clusters and one Chinese collection of singleton position, within the Russula albonigra lineage. Two of the North-American clusters are supported and probably represent well defined species, while the status of the three sequences from the United States (KF306041, JF834355 and KF306040) is uncertain and requires more sequence data to resolve. The singleton Chinese sample (KX441086) probably represents an undescribed species sister to R. albonigra. Furthermore, Fig. 2 shows an overview of the different UNITE species hypotheses within the R. albonigra lineage at different thresholds. At a threshold of 1% or higher two species hypotheses are recognised (for SH numbers see red and pink boxes in the Fig. 2). The first one labelled as R. albonigra with the representative UNITE sequence UDB016040 covers R. ambusta, R. nigrifacta, R. ustulata and the North-American species. The second one with the representative sequence JF519228 is labelled as Russula sp. and covers R. albonigra and the Chinese species. At a threshold of 0.5% all European species (except for R. sp. 1 which is not represented by any public sequence) and two North-American species are supported. Threshold < 0.5% gives additional units within the phylogenetic species that were not supported by our multi-locus analysis.
Taxonomy
The species within the Russula albonigra lineage are characterised by the moderately distant, relatively narrow lamellae, the context that is rapidly and strongly blackening, generally without intermediate reddening. In some cases though, some slight reddening is observed. The taste of the lamellae and flesh is never acrid, but can be menthol-cooling. Microscopically, the species are defined by spores with low and dense warts forming subreticulate to reticulate ornamentation, long pileocystidia (if present) and a cystidial content which is not reacting in sulfovanillin.
Russula albonigra (Krombh.) Fr. (Figs. 3c-f, 4–6)
Lectotype: plate 70, Figs. 16–17 in Krombholz (1845) (Lectotypus; hic designates; MBT number to be assigned).
Epitype: Slovakia, Oblík Nature reserve, with Fagus, 23 Sept. 2017, S. Adamčík, SAV F-20179 (Epitypus, SAV; hic designates; MBT number to be assigned).
Pileus large, 56–112 mm diam., plano-convex, at the centre with shallow but wide depression; margin deflexed, long involuted, not striated, smooth; pileus surface velvety and smooth near margin, towards the centre radially wrinkled or rugulose, centre smooth, dry, matt, almost not peeling (max. up to 1/3 of the radius); young completely white, later becoming yellowish white (4A2), cream (4A3) to orange grey (5B2) at the centre, more greying and blackening when old. Lamellae segmentiform to subventricose, up to 6 mm deep, adnate to subdecurrent; snow white, later yellowish white (4A2), blackening with age or when bruised; with numerous lamellulae of different lengths, frequently forked near the stipe but also near the pileus margin, often anastomosed; moderately crowded to moderately distant, L = 190–260, l = 1 (one between each pair of long lamellae); edges even, concolorous, blackening with age. Stipe 42–60 × 14–29 mm, cylindrical, firm and fleshy, longitudinally striated, velvety near the lamellae; white, later becoming greyish orange (5B4) near the base; interior solid, with ca. 2.5 mm thick cortex. Context ca. 7 mm thick at mid-radius, hard, white, turns rapidly grey and then black on cut section, at surface also turns red before grey and black; turning orange with FeSO4, immediately dark blue with guaiac (strong reaction, +++); taste mild, slightly like mint (refreshing) in lamellae, odour weak of apples.
Spores (7.1–)7.5–8.0–8.5(–9.4) × (5.6–)5.9–6.3–6.7(–7.1) µm, broadly ellipsoid to ellipsoid, Q= (1.16–)1.22–1.29–1.36(–1.49); ornamentation of low, dense [(6–)7–10(–11) in a 3 µm diam. circle] amyloid warts, 0.1–0.4 µm high, subreticulate, abundantly fused into chains [(0–)3–7(–8) fusions in a 3 µm diam. circle], and also connected by short, fine line connections [0–4(–6) in a 3 µm diam. circle]; suprahilar spot medium-sized, not amyloid. Basidia (44–)48.9–55.1–61.3(–75) × 10.0–10.8–11.6(–13) µm, narrowly clavate, 4-spored. Hymenial cystidia (65–)69.6–85.8–102.0(–115) × (7–)7.6–8.5–9.4(–10) µm, cylindrical to narrowly fusiform, apically obtuse to mucronate, thin-walled; with little content composed of large pale, oily, refringent guttules, without reaction in sulfovanillin; near the lamellae edges, (30–)40.4–58.5–76.6(–98) × (6–)7.1–7.9–8.7(–9) µm, cylindrical to narrowly fusiform, sometimes slightly flexuose, apically obtuse to mucronate or with small appendage, thin-walled, content same as on lamellae sides. Lamellae edges sterile, when older elements can contain brown pigments; marginal cells (11–)16.5–22.1–27.7(–31) × (3–)3.5–4.9–6.3(–8) µm, poorly differentiated, cylindrical, flexuose, thin-walled. Pileipellis orthochromatic in Cresyl Blue, 80–90 µm deep, not sharply delimited from trama and not gradually passing, intermediate; subpellis not delimited from suprapellis; hyphae 3–6 µm wide near trama, not regular in width, dense, homogeneous, pigmented only near the surface, with no distinct gelatinous coating or only weakly on deeper hyphae. Acid-resistant incrustations absent. Hyphal terminations near the pileus margin long, with multiple septa, flexuous, thin-walled, filled with irregular refractive bodies containing brown pigments; terminal cells very long (35–)55.9–86.6–117.3(–160) × (5–)5.2–6.6–8.0(–10) µm, narrowly cylindrical to subulate, on average apically constricted to 3.5 µm (average difference of 3.2 µm between maximum width and width of the tips); subterminal cells and the cells below usually shorter and gradually wider, subterminal cells occasionally branched. Hyphal terminations near the pileus centre slightly slender and apically less attenuated; terminal cells slightly shorter (40–)51.8–72.9–94.0(–124) × (4–)4.5–6.0–7.5(–10) µm, subterminal cells never branched. Pileocystidia near the pileus margin widely dispersed, 1–3 celled, long, terminal cells (61–)73.0–97.5–122.0(–160) × (5–)5.5–7.0–8.5(–10) µm, cylindrical to subulate, flexuose, sometimes with small lateral projection, apically obtuse or with 1–2 eccentric appendages, sometimes bifurcating, with oily guttulate content, without reaction in sulfovanillin; near the pileus centre widely dispersed, 1–2 celled, generally shorter, terminal cells (52–)58.0–75.2–92.4(–115) × (4–)5.1–6.8–8.5(–11) µm, similar in shape and content, mostly apically with 1–2 eccentric appendages, not bifurcating. Pileocystidia not near surface but only deeper in the pileipellis. Oleiferous hyphae containing brown pigments and cystidioid hyphae present in the trama.
Ecology: Associated with Fagus sylvatica and/or Abies alba and/or Picea abies and/or Carpinus betulus.
Distribution: Known from Austria, the Czech Republic, Estonia, Germany, Norway and Slovakia.
Additional material studied: Slovakia. Stužica Natural reserve, under Kýčera hill, with Abies and Fagus, 22 Sept. 2017, S. Adamčík, SAV F-20177 (SAV); Stužica National Nature Reserve, central part, with Fagus sylvatica, 5 Oct. 2003, S. Adamčík, SAV F-755 (SAV); Badínsky prales Nature reserve, with Abies and Fagus, 22 Sept. 2017, S. Adamčík, SAV F-2559 (SAV); Badínsky prales Nature reserve, with Abies and Fagus, 29 Sept. 2011, S. Adamčík, SAV F-3465 (SAV); Revúca, road to Sirk, with Fagus sylvatica, 14 Oct. 2015, S. Adamčík, SAV F-4776 (SAV); Germany. Bavaria, Oberallgäu, Oberstaufen, Hündle, alt. 975 m, N47°32'45.9" E10°04'15.1", with Abies alba, Fagus sylvatica and Picea abies, 6 Sept. 2013, J. Kleine, JK RUS 13090603 (personal herbarium Jesko Kleine); Czech Republic. Central Bohemia, Chrudim District, Bojanov (Horní Bezděkov), under Fagus, 12 Aug. 2012, J. Borovička, PRM 934322 (PRM); Central Bohemia, Kladno District, Běleč (Jenčov), under Fagus and Carpinus, 3 Sept. 2013, J. Borovička, PRM 924409 (PRM).
Russula ambusta De Lange, Adamčík & F. Hampe sp. nov. (Figs. 3g, 7–9)
Mycobank: to be assigned
Holotype: Slovakia, Vývrať, Bučková, W slopes of the hill, with Quercus, 6 July 2011, V. Kučera, SAV F-3558 (Holotypus, SAV).
Etymology: Refers to the appearance of the basidiomata, which look like they were burnt.
Diagnosis: Differs from the other species of the Russula albonigra lineage by the intermediate spore ornamentation and the presence of appendages, but lack of bifurcations on the pileocystidia.
Pileus large, 45–100 mm diam., planoconvex to applanate, centrally depressed to umbilicate, becoming more infundibuliform when older; margin slightly inflexed when young, straight when mature, smooth; pileus surface smooth, dry, dull to somewhat viscid when wet; greyish orange, light brown (5B5, 5D5) to umber, greyish brown (5F8, 6F3) with paler white to sand coloured patches. Lamellae segmentiform to subventricose, up to 6 mm deep, adnate to subdecurrent; snow white, later yellowish white (4A2), blackening with age or when bruised; with numerous lamellulae of different lengths; dense (7–10L + 5–8 l/cm at mid-radius); edges even, concolorous, blackening with age. Stipe 30–40 × 15–25 mm, cylindrical, firm and fleshy, smooth; white but rapidly almost completely orange brown; solid inside. Context ca. 3–5 mm thick at mid-radius, firm, white, greying before blackening, no reddening observed; turning immediately dark blue with guaiac (strong reaction, +++); taste first mild, then quickly somewhat cooling with menthol component, never spicy or acrid; odour indistinct. Spore print white (Ia).
Spores (6.7–)7.4–8.2–9.0(–9.6) × (5.4–)5.7–6.0–6.3(–6.8) µm, broadly ellipsoid to narrowly ellipsoid, Q= (1.18–)1.28–1.38–1.48(–1.54); ornamentation of very low, dense to very dense [(6–)7–13(–16) in a 3 µm diam. circle] amyloid warts, up to 0.2 µm high, subreticulate to reticulate, abundantly fused in chains [(2–)3–8(–10) fusions in a 3 µm diam. circle], and also connected by short, fine line connections [(0–)1–9(–17) in a 3 µm diam. circle]; suprahilar spot medium-sized, not amyloid. Basidia (54–)57.5–62.6–67.7(–76) × (8–)8.9–9.5–10.1(–11) µm, narrowly clavate, 4-spored. Hymenial cystidia (66–)67.1–91.9–107.7(–125) × (7–)8.5–9.8–11.1(–13) µm, variable: (1) narrowly fusiform to narrowly clavate, flexuose to even slightly moniliform, apically obtuse or with a constriction or with small appendage to even slightly mucronate, thin-walled; with heteromorphous, oily content, mostly fragmented in multiple crystalline-like masses or slightly granulose, without reaction in sulfovanillin; (2) narrowly fusiform to lanceolate, flexuose, tapering towards the top; with less content, heteromorphous, oily, mostly fragmented in multiple crystalline-like masses or slightly granulose, without reaction in sulfovanillin; near the lamellae edges, (29–)37.0–63.7–90.4(–144) × (5–)7.2–8.5–9.8(–10) µm, (1) narrowly fusiform to narrowly clavate, flexuose, apically obtuse or tapering towards the top in a moniliform way with a small appendage, thin-walled; content same as on lamellae sides; (2) same as on lamellae sides. Lamellae edges sterile, when older elements can contain brown pigments; marginal cells (15–)19.1–26.1–33.1(–36) × (4–)4.7–5.6–6.5(–7) µm, undifferentiated, cylindrical to narrowly clavate, thin-walled. Pileipellis orthochromatic in Cresyl Blue, 175–400 µm deep, not sharply delimited from trama, gradually passing; subpellis not delimited from suprapellis; hyphae 3–6 µm wide near trama, dense near surface and near trama, irregularly oriented, more parallel and horizontal near trama and surface, intricate everywhere, pigmented near surface only, with no distinct gelatinous coating. Acid-resistant incrustations absent. Hyphal terminations near the pileus margin long, with multiple septa, flexuous, thin-walled, filled with irregular refractive bodies containing brown pigments; terminal cells (41–)51.4–70.2–89.0(–125) × (3–)4.3–5.4–6.5(–8) µm, narrowly cylindrical, on average apically constricted to 3.5 µm; subterminal cells and the cells below similar in length or slightly shorter, similar in width or gradually slightly wider, subterminal cells and cells below sometimes branched. Hyphal terminations near the pileus centre similar, terminal cells usually shorter (28–)40.8–59.8–78.8(–106) × (3–)4.0–5.0–6.0(–7) µm, subterminal cells and cells below not branching. Pileocystidia hard to find; near the pileus margin widely dispersed to rare, mostly 1-celled, but up to 3-celled, long, terminal cells (73–)79.1–110.6–142.1(–145) × 4.9–7.2–9.5(–11) µm, cylindrical, flexuose, apically mostly with 2–3 eccentric appendages or obtuse, content same as in hymenial cystidia or more granulose, without reaction in sulfovanillin; near the pileus centre widely dispersed, 1-celled, (63–)79.4–106.7–134.0(–151) × (4–)5.0–6.4–7.8(–8) µm, cylindrical to slightly subulate, apically with double constriction or 1–2 eccentrical appendages, contents same as near pileus margin. Oleiferous hyphae containing brown pigments and cystidioid hyphae present in the trama.
Ecology: Associated with Quercus robur and Pinus sylvestris and/or Betula pendula.
Distribution: Known from Estonia, Germany, Slovakia, Spain and Sweden.
Additional material studied: Germany. Brandenburg, Landkreis Oder-Spree, near Helenesee Frankfurt-Oder, Markendorfer Forst, MTB 3752/2 (Müllrose), N 52.256386 E 14.46049, lichen-pine (Pinus sylvestris) forest with interspersed birch trees (Betula pendula) on an unpaved forest path, on sandy soil, 19 Oct. 2008, F. Hampe, FH 2008 ST01 (personal herbarium Felix Hampe).
Remarks: The range of the spore size is large within this species. This results from the spore size difference between the collections. The holotype (SAV F-3558) has smaller spores and lower Q-value than collection FH 2008 ST01. The variability in the shape of the hymenial cystidia is also due to the difference between the collections with the holotype having cystidia of type 1 and collection FH 2008 ST01 having cystidia of type 2 (types referring to (1) and (2) in the description). Therefore we could hypothesize these collections to represent a different species based on morphology. Nevertheless, we treat them here as the same species because phylogenetically there is no support for the hypothesis of two different species. All markers used in this study place these two collections together as the same species. Measurements are given for each collection separately in Supplementary material 1. Of course more collections and more micromorphological study are needed in order to understand this intraspecific variation. The UNITE species hypothesis at 0.5% corresponding to our concept of R. ambusta is based on a locked sequence and after this publication we will propose to change the reference sequence to the holotype of the species.
Russula nigrifacta De Lange & Adamčík sp. nov. (Figs. 3a-b, 10–12)
Mycobank: to be assigned
Holotype: Italy, Tuscany, Province of Livorno, Piombino, with Quercus ilex and Quercus suber, 9 Nov. 2016, R. De Lange, RDL 16–044 (Holotypus, GENT).
Etymology: Named after the strong blackening of the basidiomata
Diagnosis: Differs from the other species of the Russula albonigra lineage by the lack of appendages and bifurcations on the pileocystidia.
Pileus large, 75–105 mm diam., planoconvex to applanate, centrally depressed to umbilicate, becoming more infundibuliform when older; margin slightly inflexed when young, straight when mature, smooth; pileus surface smooth, sometimes slightly cracked at the margin, dry, dull to somewhat viscid when wet; ivory to cream, sand coloured, yellowish white (4A2, 5A3, 5B3) with darker spots of pale brownish/greyish orange, yellowish brown to light brown, dark brown (5B6, 5E4, 5E8, 5F4). Lamellae narrow, segmentiform to subventricose, 2–4 mm deep, adnate to subdecurrent; white to yellowish white, rarely with faintly blueish shine, blackening with age; with numerous lamellulae of different lengths without clear regular pattern, rarely locally anastomosing; dense (6–9L + 8–9 l/cm at mid-radius); edges even, concolorous, blackening with age. Stipe 30–60 × 19–30 mm, cylindrical, firm and fleshy, smooth; white, becoming more orange brown with age; solid inside. Context ca. 6–7 mm thick at mid-radius, firm, white, blackening without reddening, surface of pileus and stipe also slightly reddening before blackening; turning blue/green with FeSO4, yellowish with KOH, immediately dark blue with guaiac (strong reaction, +++); taste mild to slightly refreshing; odour fruity, sweet. Spore print white (Ia).
Spores (6.7–)7.5–8.0–8.5(–9.5) × (5.0–)5.7–6.0–6.3(–7.0) µm, broadly ellipsoid to ellipsoid, Q= (1.15–)1.25–1.34–1.43(–1.56); ornamentation of low, dense [(5–)7–10(–11) in a 3 µm diam. circle] amyloid warts, 0.2–0.4 µm high, subreticulate, abundantly fused into chains [(0–)3–6(–8) fusions in a 3 µm diam. circle] and also connected by short, fine line connections [0–3(–4) in a 3 µm diam. circle]; suprahilar spot small, not amyloid. Basidia (50–)57.0–62.8–68.5(–79) × (8–)8.7–9.6–10.5(–11) µm, narrowly clavate, 4-spored. Hymenial cystidia (57–)62.6–82.6–102.6(–128) × (7–)7.7–8.9–10.1(–15) µm, cylindrical to narrowly fusiform to narrowly clavate, sometimes slightly flexuose, apically obtuse or with small appendage, thin-walled; with heteromorphous, oily content, fragmented in multiple crystalline-like masses, without clear reaction in sulfovanillin; near the lamellae edges, (37–)53.0–69.4–85.8(–119) × (7–)8.0–9.1–10.2(–11) µm, cylindrical to narrowly fusiform, sometimes narrowly clavate, often slightly flexuose, apically obtuse with small appendage or mucronate to tapering towards the top, thin-walled; content same as on lamellae sides. Lamellae edges sterile, when older elements can contain brown pigments; marginal cells (15–)17.7–22.2–26.7(–30) × (4–)4.6–5.9–7.2(–10) µm, poorly differentiated, cylindrical to narrowly clavate, flexuose, thin-walled. Pileipellis orthochromatic in Cresyl Blue, 90–136 µm deep, not sharply delimited from trama and not gradually passing, intermediate; subpellis not well delimited from suprapellis; hyphae 2.5–7 µm wide near trama, dense near surface and near trama, irregularly oriented, more parallel and horizontal near trama, pigmented throughout the pileipellis, with some gelatinous coating. Acid-resistant incrustations absent. Hyphal terminations near the pileus margin long, slender, with multiple septa, flexuous, thin-walled, filled with irregular refractive bodies containing brown pigments; terminal cells (50–)63.5–83.5–103.5(–133) × (3–)4.0–4.9–5.8(–7) µm, narrowly cylindrical; subterminal cells and the cells below similar in length and width, subterminal cells never branched. Hyphal terminations near the pileus centre similar; terminal cells (42–)53.1–79.6–106.1(–135) × (3–)3.4–4.6–5.8(–8) µm, sometimes more subulate, subterminal cells and cells below shorter, subterminal cells rarely branched. Pileocystidia near the pileus margin dispersed, 1–4 celled, very long, terminal cells (41–)83.4–119.5–155.6(–235) × (5–)5.8–6.7–7.6(–9) µm, cylindrical, flexuose, apically obtuse or with slight constriction, with oily granulose content, without clear reaction in sulfovanillin; near the pileus centre dispersed, 1–2 celled, similar in shape and content or with less and more oily guttulate content, terminal cells (64–)80.9–123.0–165.1(–220) × (4–)5.2–6.0–6.8(–7) µm. Oleiferous hyphae containing brown pigments and cystidioid hyphae present in the trama.
Ecology: Associated with Mediterranean oaks (Quercus ilex and Quercus suber) in Italy, in Slovakia with Quercus robur and/or Carpinus betulus.
Distribution: Known from Estonia, Italy and Slovakia.
Additional material studied: Italy. Tuscany, Province of Livorno, Piombino, with Quercus ilex and Quercus suber, 7 Nov. 2016, R. De Lange, RDL 16–028 (GENT); Tuscany, Province of Livorno, Piombino, with Quercus ilex and Quercus suber, 11 Nov. 2016, R. De Lange, RDL 16–063 (GENT); Slovakia. Obyce, forest NE of the village, with Quercus and Carpinus, 24 July 2008, S. Adamčík, SAV F-2418 (SAV); Prenčov, Horné Majere, with Quercus and Carpinus, 22 July 2008, S. Adamčík, SAV F-2419 (SAV); Tepličky, with Quercus and Carpinus, 4 July 2009, S. Adamčík, SAV F-3006 (SAV); Bohunický Roháč, forest close to the nature reserve, with Quercus, 8 Sept. 2006, S. Adamčík, SAV F-1501 (SAV).
Russula ustulata De Lange & Verbeken sp. nov. (Figs. 3h, 13–14)
Mycobank: to be assigned
Holotype: Norway, NT Steinkjer, Kvamsfjellet, North of Lystjörna, Austerolsenget, alt. 137.5 m, N64°12’47’’ E11°49’09’’, 20 Aug. 2016, A. Verbeken, AV 16–019 (Holotypus, GENT).
Etymology: Refers to the appearance of the basidiomata, which look like they were burnt.
Diagnosis: Differs from the other species of the Russula albonigra lineage by the absence (or rareness) of pileocystidia.
Pileus large, 101–112 mm diam., planoconvex to applanate, centrally depressed to umbilicate to infundibuliform, widely V-shaped; margin straight, smooth; pileus surface smooth, glabrous, dry, shiny; very dark blackish brown to dark grey-black (7F2–4) without lighter brown tints, uniform. Lamellae narrow, segmentiform to subventricose, 4–5 mm deep, adnate to subdecurrent; completely white to yellowish white, quickly blackening; with numerous lamellulae of different lengths, locally anastomosing; moderately distant (6–9L + 3–4 l/cm at mid-radius) to distant (sometimes almost as in R. nigricans); edges even, papery thin, concolorous, quickly blackening with age. Stipe 45–65 × 25–30 mm, cylindrical, firm and fleshy, smooth to irregular surface, dry; white but rapidly turning dark grey, black (stays whitish only at the top); solid inside. Context ca. 5–9 mm thick at mid-radius, firm, white, staining grey, then brownish black, mostly blackening without reddening but a slight pink tinge can be present; turning green with FeSO4; taste mild but not agreeable, musty, but slightly menthol-like in the gills. Spore print white (Ia).
Spores (7.4–)8.1–8.5–8.9(–9.3) × (5.7–)6.0–6.3–6.6(–6.9) µm, broadly ellipsoid to ellipsoid, Q= (1.12–)1.26–1.36–1.46(–1.48); ornamentation of very low, very dense [(9–)10–15(–17) in a 3 µm diam. circle] amyloid warts, up to 0.2 µm high, reticulate, abundantly fused into chains [3–7(–10) fusions in a 3 µm diam. circle], abundantly connected by short, fine line connections [(6–)7–11(–13) in a 3 µm diam. circle]; suprahilar spot large, not amyloid. Basidia (53–)58.9–67.3–75.7(–83) × (8–)8.4–9.2–10.0(–11) µm, narrowly clavate to cylindrical, 4-spored. Hymenial cystidia (78–)88.7–106.6–124.5(–153) × (7–)8.0–9.1–10.2(–12) µm, cylindrical to narrowly fusiform, apically obtuse with small appendage or slightly tapering towards the top, thin-walled; with heteromorphous, oily content, fragmented in multiple masses to needle-like crystalline, without reaction in sulfovanillin; near the lamellae edges, (60–)70.0–82.9–95.8(–111) × (7–)8.1–9.5–10.9(–14) µm, narrowly fusiform to narrowly conical, slightly flexuose, apically obtuse, sometimes with small appendage or tapering towards the top, thin-walled; content same as on lamellae sides, often containing brown pigments. Lamellae edges sterile, when older elements can contain brown pigments; marginal cells (14–)19.8–26.5–33.2(–39) × 4.9–6.3–7.7(–10) µm, poorly differentiated, cylindrical to narrowly clavate to fusiform, flexuose, thin-walled. Pileipellis orthochromatic in Cresyl Blue, 250–300 µm deep, not sharply delimited, gradually passing; subpellis not delimited from suprapellis; hyphae 3–7 µm wide near trama, dense near surface and near trama, loose in intermediate zone, irregularly oriented, pigmented throughout the pileipellis, some gelatinous coating can be present deeper in the pileipellis. Acid-resistant incrustations absent. Hyphal terminations near the pileus margin long, with multiple septa, flexuous, thin-walled, filled with irregular refractive bodies containing brown pigments; terminal cells (29–)36.0–53.6–71.1(–100) × (4–)4.9–6.0–7.1(–9) µm, narrowly cylindrical to subulate, on average apically constricted to 4.5 µm; subterminal cells and the cells below shorter and gradually wider, subterminal cells never branched, cells below occasionally branched. Hyphal terminations near the pileus centre slightly slender and apically less attenuated; terminal cells slightly longer, (31–)43.3–59.0–74.7(–89) × (3–)4.0–5.1–6.2(–8) µm, subterminal cells and cells below more of similar size as terminal cells, subterminal cells rarely branched. Pileocystidia near the pileus margin extremely rare (only 5 observed), inconspicuous, hardly distinguishable, 58.2–79.6–101.0(–115) × (6–)6.3–7.0–7.7(–8) µm, cylindrical to narrowly clavate, apically obtuse, content like hymenial cystidia but very little, near the pileus centre absent. Oleiferous hyphae containing brown pigments present in the trama, cystidioid hyphae absent.
Ecology: Associated with Picea abies and Pinus sylvestris.
Distribution: Known from the Czech Republic, Estonia, Finland, Italy, Norway and the Russian Federation.
Additional material studied: Italy. Langhestel, with Picea and Pinus sylvestris, 25 Sept. 1997, S. Adamčík, SAV F-2610 (SAV); Czech Republic. South Bohemia, Český Krumlov district, Malonty, with Picea and Pinus sylvestris, together with Tricholoma matsutake, 2 Sept. 2014, J. Borovička, PRM 924452 (PRM).
Russula sp. 1 (Figs. 15–17)
Pileus large, planoconvex to applanate, centrally depressed to umbilicate to infundibuliform; margin straight, smooth; pileus surface smooth, dry, dull; light brown to greyish brown, dark brown, with paler white to sand coloured patches. Lamellae narrow, segmentiform to subventricose, adnate to subdecurrent; completely white to yellowish white, quickly blackening; with numerous lamellulae of different lengths; moderately distant; edges even, concolorous, quickly blackening with age. Stipe cylindrical, firm and fleshy, smooth to irregular surface, dry; white but turning orange brown to dark grey, black; solid inside. Context firm, white, blackening without reddening; taste mild. Spore print white (Ia).
Spores (7.4–)7.6–7.9–8.2(–8.4) × (6.0–)6.1–6.3–6.5(–6.6) µm, broadly ellipsoid, Q= (1.18–)1.22–1.26–1.30(–1.33); ornamentation of very low, very dense [(8–)9–15(–16) in a 3 µm diam. circle] amyloid warts, up to 0.3 µm high, reticulate, abundantly fused into chains [(1–)2–7(–11) fusions in a 3 µm diam. circle], abundantly connected by short, fine line connections [(5–)7–13(–15) in a 3 µm diam. circle]; suprahilar spot medium-sized, not amyloid. Basidia (54–)56.7–60.9–65.1(–69) × (9–)9.4–9.9–10.4(–11) µm, narrowly clavate, 4-spored. Hymenial cystidia, 64.0–83.6–103.2(–130) × (7–)7.9–8.7–9.5(–10) µm, cylindrical to narrowly fusiform, often slightly moniliform and flexuose, apically obtuse or with double constriction or small appendage, thin-walled; with heteromorphous, oily content, fragmented in multiple crystalline-like masses, without reaction in sulfovanillin; near the lamellae edges, (53–)56.2–62.3–68.4(–76) × (6–)6.9–7.8–8.7(–9) µm, cylindrical to narrowly fusiform, often slightly moniliform and flexuose, apically obtuse or with small appendage, thin-walled; content same as on lamellae sides. Lamellae edges sterile, elements containing brown pigment when older; marginal cells (15–)16.3–21.5–26.7(–30) × (5–)5.3–6.6–7.9(–9) µm, undifferentiated, cylindrical to narrowly clavate, thin-walled. Pileipellis orthochromatic in Cresyl Blue, 200–275 µm deep, not sharply delimited from trama and not gradually passing, intermediate; subpellis not delimited from suprapellis; hyphae 3–5 µm wide near trama, more dense near surface and near trama, irregularly oriented, more parallel and horizontal near trama, pigmented only in the upper part of the pileipellis, with some gelatinous coating. Acid-resistant incrustations absent. Hyphal terminations near the pileus margin long, with multiple septa, scarcely branched at the bases, flexuous, thin-walled, filled with irregular refractive bodies containing brown pigments; terminal cells (39–)47.6–61.4–75.2(–86) × 5.0–6.0–7.0(–8) µm, narrowly cylindrical to slightly subulate or narrowly fusiform, on average apically constricted to 4.5 µm; subterminal cells and the cells below similar in length and width or slightly wider, subterminal cells never branched. Hyphal terminations near the pileus centre slightly wider and apically more attenuated, containing inflated cells, more often branched at the bases; terminal cells (28–)46.3–70.5–94.7(–130) × (3–)3.9–5.2–6.5(–8) µm, subterminal cells rarely branched. Pileocystidia near the pileus margin numerous, 1 celled, rarely 2 celled, extremely long, terminal cells 98–more than 320 × (8–)8.2–9.1–10.0 µm, cylindrical, flexuose, apically obtuse or with slight constriction, sometimes bifurcating, content same as in hymenial cystidia or more granulose, without reaction in sulfovanillin; near the pileus centre numerous, 1–2 celled, generally shorter but still very long, terminal cells 56.6–117.4–178.2(–298) × (5–)6.1–8.4–10.7(–14) µm, similar in shape and content, rarely with up to 3 eccentric appendages. Oleiferous hyphae containing brown pigments and cystidioid hyphae present in the trama.
Ecology: Associated with Mediterranean oak (Quercus suber).
Distribution: Known from Italy (Sardinia).
Specimen examined: Italy, Sardinia, Tempio Pausania, road SS133, between 3 and 4 km from centre, with Quercus suber, 1 Nov. 2000, R. Walleyn, RW 1975 (GENT).
Remarks: Although there is molecular and morphological support that this collection represents a species different from the other species in the Russula albonigra lineage, the authors chose to not formally describe this species here as the description is based on a single collection only.
Key to the European species of Russula subg. Compactae
1 Height of spore ornamentation not exceeding 0.5 µm....................................................... 2
- Height of spore ornamentation exceeding 0.5 µm................. roseonigra H. Pidlich-Aigner
2 (1) Content of hymenial cystidia not reacting in sulfovanillin................................................... 3
- Content of hymenial cystidia at least greying in sulfovanillin.............................................. 8
3 (2) Basidiomata sturdy and fleshy; lamellae thick and very distant; context quickly and strongly reddening before blackening; pileocystidia never exceeding 90 µm................................................... nigricans Fr.
- Lamellae thin and moderately distant; context not reddening before blackening or only slightly at the surface; pileocystidia often exceeding 90 µm................................................................................. 4
4 (3) Content of cystidia oily guttulate................................................ albonigra (Krombh.) Fr.
- Content of cystidia not oily guttulate................................................................................ 5
5 (4) Pileocystidia absent or extremely rare and only near the pileus margin................................ ustulata De Lange & Verbeken
- Pileocystidia at least widely dispersed and found throughout the whole surface of the pileus ...............................................6
6 (5) Pileocystidia never with appendages or bifurcations......... nigrifacta De Lange & Adamčík
- Pileocystidia (at least some) containing appendages or bifurcations................................... 7
7 (6) Pileocystidia numerous, extremely long (some exceeding 200µm), with both appendages and bifurcations present; hyphal terminations of the pileipellis with inflated cells........................................ sp. 1
- Pileocystidia widely dispersed, never exceeding 160 µm, lacking bifurcations; hyphal terminations of the pileipellis without inflated cells.......................................................................................... ambusta De Lange, Adamčík & F. Hampe
8 (2) Taste mild....................................................................................................................... 9
- Taste, at least in the lamellae, noticeably acrid................................................................ 10
9 (8) Context not clearly reddening but quickly and strongly blackening, sometimes with a slight menthol-like taste ; pileocystidia absent; spore ornamentation up to 0.5 µm................................................... atramentosa Sarnari
- Context turning slowly pale pink before greying (but almost simultaneously, and without strong blackening); smell of old wine barrels; pileocystidia present; spore ornamentation not exceeding 0.2 µm adusta (Pers.) Fr.
10 (8) Hyphal terminations of the pileipellis consisting of shorter, broad, swollen cells............... 11
- Hyphal terminations of the pileipellis consisting of longer, slender cells............................ 12
11 (10) Context clearly reddening before turning grey-black................... densifolia Secr. ex Gillet
- Context not clearly reddening, first greying then blackening............. densissima Romagn.
12 (10) Context quickly and strongly blackening; lamellae with a distinct pinkish shine; pileocystidia absent; hyphal terminations of the pileipellis sometimes containing blackish droplets in..................... sulfovanillin anthracina Romagn.
- Context not so strongly and quickly blackening, more greying or slowly blackening; pileocystidia present..................................................................................................................................... 13
13 (12) Context strongly reddening, then greying; taste burning acrid, in the flesh as well as in the lamellae acrifolia Romagn.
- Context not clearly reddening, slowly blackening; taste acrid, but not burning and more prominent in the lamellae than in the context................................................................ fuliginosa Sarnari