Basidiomes agaricoid (pileostipitate), gymnocarpic (no veils), mostly mycenoid or rarely collybioid, homogeneous (context of stipe and pileus continuous), hymenophore lamellate, lamellae adnexed, decurrent with a tooth to almost free or free, spore deposit white to whitish, basidiospores usually smooth, when mature usually thick-walled, non-amyloid, often weakly to strongly dextrinoid, basidia non-siderophilous, sometimes thick-walled and sclerified (wall 1–3 µm thick, crassobasidia or sclerobasidia) and dextrinoid, hymenophoral trama regular to subregular, hymenial cystidia absent or present as cheilocystidia, rarely as pleurocystidia, caulocystidia usually present, pileipellis a cutis to trichoderm or pluristratous hymeniderm/epithelium/celluloderm, pileocystidia-like elements rare, clamp-connections present or absent, hyphal system monomitic. Terrestrial, trophic mode unknown, presumably saprotrophic or forming an unspecified symbiotic interaction with vascular plants.

Pseudobaeospora Singer, Lloydia 5: 129 (1942).

Baeospora oligophylla Singer, Revue Mycol., Paris 3(4–5): 194 (1938) = Collybia pillodii Quél. [as ‘pillodi’], C. r. Assoc. Franç. Avancem. Sci. 18(2): 509 (1890).

Pseudobaeospora .

The subfamily is currently monogeneric and is sister to the core of the Tricholomataceae [Tricholomataceae subfam. Tricholomatoideae (Singer) Bon] (Figs 1, 2) within the Tricholomatineae. Pseudobaeospora is circumscribed by small mycenoid (e.g., P. celluloderma) to collybioid white-spored basidiomes [indicatively, pileus 1.5–30 mm in diam., stipe 10–55(–70) × 0.5–3.0 mm]; pileus frequently with pale to dark lilac, violaceous, purple, blue tinges, hemispherical, obtusely conical or paraboloid to plano-convex or plano-conical (campanulate); lamellae adnexed, emarginate, or decurrent with a tooth to free, usually more or less concolorous with pileus; stipe pruinose to fibrillose, often rooting, at base mostly with white to rarely yellow tomentum and rhizomorphs; basidiospores small (from 2.5 µm to rarely more than 6.5 µm long), subglobose to broadly ellipsoid, colorless, smooth (minutely rugulose under SEM in P. wipapatiae Desjardin, Hemmes & B.A. Perry, Desjardin et al. 2014), pore-less, with very distinct, abrupt hilar appendage, at first thin-walled and non-amyloid, then becoming thick-walled and weakly to strongly dextrinoid, congophilous, cyanophilous, and rather frequently more or less metachromatic in Cresyl blue (e.g., P. paulochroma Bas, P. bavariae Bas); basidia 4-spored to 2-spored, or 4- and 2-spored in the same basidiome, often with a basal clamp-connection, without inner siderophilous granulations, scattered sclerified (thick-walled) dextrinoid basidia (sclerobasidia, crassobasidia following Singer and Clémençon 1972, Watling and Chandra 1983, and Clémençon 2004) often present; pleurocystidia usually lacking (rarely present, e.g., P. aciculifera Voto & Soop, P. cyanea, P. taluna) and cheilocystidia present in some species, in one case with amyloid contents (P. wipapatiae); hymenophoral trama regular to somewhat irregular, with elements in central part (mediostratum) often inflated; pileipellis varying from a simple cutis or cutis-trichoderm to a trichoderm in some species to an irregular pluristratous hymeniderm/epithelium/ /celluloderm in others; some terminal elements could be differentiated as pileocystidia; hyphae thin-walled, not or slightly gelatinized; pigments predominantly parietal (sometimes also hyphae with minute extracellular incrustations) but also intracellular (vacuolar or cytoplasmatic); in 5% KOH pileipellis fragments usually changing colour or becoming violet, green, yellow or brownish with such tinges, rarely first red then yellow-green; in several species pseudotissues more or less dextrinoid; caulocystidia usually present at least at stipe apex, thin-walled, scattered to clustered; clamp-connections usually present in several or all tissues, rare in P. calcarea, in one species restricted to basidia and subhymenium (P. frieslandica Bas) or absent (e.g., P. pillodii).

The species show a terrestrial habit, usually on needle carpets of conifers, forest litter, wooden debris, humus, deeply hidden among/on mosses and grasses but also sometimes on bare soil (Bas 2002, 2003). Their trophic status remains unknown, presumably saprotrophic, non-ectomycorrhizal (Bas 2002, 2003; not reported in Rinaldi et al. 2008, Tedersoo et al. 2010, and Tedersoo and Smith 2013). As noted by Ronikier and Moreau (2007), most species appear to prefer calcareous and/or nutrient-rich soils, but some are found on peaty soils.

The unique combination of small-sized mycenoid to collybioid basidiomes often with lilac violet tinges, pileipellis usually positively reacting with KOH, presence of scattered dextrinoid thick-walled basidia and small-sized spores becoming secondarily thick-walled and dextrinoid makes this genus easily identifiable and delimitable. Thickening spore walls becoming dextrinoid typically occurs also in the genus Rhodocollybia Singer (Omphalotaceae Bresinsky, Marasmiineae Aime, Dentinger & Gaya) (Antonín and Noordeloos 1997, 2010) and is considered a generic character. Rhodocollybia however differs in larger spores, larger basidiomes with a simple ixocutis, absence of crassobasidia, a pinkish yellow to pinkish brown, never white spore deposit, and a different (contradictory) trophic habit, viz. putatively EcM (Pera and Alvarez 1995; Mleczko 2004; Schirkonyer et al. 2013) to facultatively biotrophic saprobe (secondary colonizers of senescent EcM root tips, Tedersoo et al. 2010; Tedersoo and Smith 2013).

Crassobasidia (non-dextrinoid) are occasionally present in different suborders of Agaricales: Armillaria (Fr.) Staude and Xerula Maire/Hymenopellis R.H. Petersen (Physalacriaceae Corner) within Marasmiineae (Singer and Clémençon 1972; Watling and Chandra 1983; Watling 1992; Clémençon 2004; Antonín and Dvořák 2010; Petersen and Hughes 2010); Amanita Pers. (Amanitaceae E.-J. Gilbert) within Pluteineae Aime, Dentinger & Gaya (Kotilová-Kubičková and Pouzar 1988; Tulloss and Halling 1997); Clavaria stellifera J. Geesink & Bas, Camarophyllopsis Herink s.l. and Ramariopsis (Donk) Corner (Clavariaceae Chevall.) within Clavariineae Olariaga, Huhtinen, Læssøe, J.H. Petersen & K. Hansen (Singer 1986; Geesink and Bas 1992; Halama et al. 2017); Crepidotus (Fr.) Staude (Crepidotaceae (S. Imai) Singer) and Inocybe (Fr.) Fr. s.l. (Inocybaceae Jülich) within Agaricineae Fr. (Kuyper 1986; Senn-Irlet 1995); Calocybella Vizzini, Consiglio & Setti (Lyophyllaceae Jülich), Fayodia Kühner (Fayodiaceae Jülich), Dermoloma J.E. Lange ex Herink (Tricholomataceae) and Entoloma (Fr.) P. Kumm. (Entolomataceae Kotl. & Pouzar), within Tricholomatineae (Singer 1986; Arnolds 1993; Horak and Desjardin 1993; Manimohan et al. 1995; Latha et al. 2020). Their presence is a generic character only for Armillaria and Camarophyllopsis s.l. (Singer 1986).

The microchemical reaction, 5% KOH pileipellis fragments which commonly become blue green is reminiscent of that exhibited by some Gymnopus (Pers.) Gray species allied with G. alkalivirens (Singer) Halling (Halling 1979, 1981, 1990; Antonín and Noordeloos 1997, 2010) (Omphalotaceae, Marasmiineae), Xerophorus (Bon) Vizzini, Consiglio & M. Marchetti (Vizzini et al. 2020a) (Callistosporiaceae Vizzini, Consiglio, M. Marchetti & P. Alvarado, Tricholomatineae) and Leucoagaricus Locq. ex Singer/Leucocoprinus Pat. species (Agaricaceae, Leucocoprineae Singer, Bon 1993; Vellinga et al. 2010; Asif et al. 2024; Kooij et al. 2024; Yang et al. 2024).

With the exclusion of Pseudobaeospora (Tricholomataceae subfam. Pseudobaeosporoideae) from the family core Tricholomataceae (Tricholomataceae subfam. Tricholomatoideae) the latter subfamily is thus restricted to species characterized by a mostly tricholomatoid or rarely tricholomatoid-collybioid habit (Dennisiomyces, Dermoloma), with smooth or verrucose (Leucopaxillus) non-dextrinoid and thin-walled basidiospores, whose walls usually react in grey or blue to Melzer’s reagent (immediately amyloid, Albomagister partim, Dermoloma subg. Amylospora Adamčík, Corneriella, Dennisiomyces, Leucopaxillus, Porpoloma, Pseudoporpoloma and Pseudotricholoma; latently amyloid, Tricholoma; see Moreau et al. 2015; Vizzini et al. 2016, 2020b, 2024; Corriol and Jargeat 2018; Sánchez-García et al. 2021; Matheny et al. 2024).

(selected here, MBT10024681): Quélet’s original plate, 1890, C.R. Ass. franç. Av. Sci. 18: pl. XV, fig. 4. Fig. 4g

(designated here, MBT10024682): FRANCE • Savoie, Bourg-Saint-Maurice, Arc 1800, under Alnus alnobetula (Ehrh.) K. Koch, 27 August 2006, leg. P-A Moreau (LIP PAM06082703).

Ludwig (2000: 152, 70.1); Ronikier and Moreau (2007: 1b, c); Morozova and Popov (2013: pl. I-1); Christan and Rexer (2020: 41).

Kühner and Romagnesi (1954: 92, as Collybia pillodii); Horak (1968: 511–513, as P. oligophylla); Redhead (1982: 217, as P. pillodii, no data on presence/absence of clamp-connections); Bas (2003: 192–193, as P. pillodii, 194–195 as P. oligophylla); Morozova and Popov (2013: 129–130, as P. pillodii, in Russian).

Spores (2.8–)3.3–3.7–4.2(–5.6) × (2.5–)2.9–3.1–3.4(–4.2) µm (288/5/5), Q = (0.96–)1.07–1.19–1.32(–1.69), V = (10.2–)14.6–19.8–25.0(–46.1) μm³, globose to subglobose or broadly ellipsoid in frontal and side view, wall up to 0.2–0.3 µm thick, smooth, colorless in L4; hilar appendix prominent, 0.5–0.8 µm long (Fig. 6c–f). Basidia 16–17.5 × 5–6 µm, mostly tetraspored but also bispored, clavate, sterigmata up to 5 µm long. Hymenophoral trama regular to subregular, consisting of up to 8 µm wide hyphae, colorless in L4. Hymenial cystidia absent. Pileipellis suprapellis as a quite compact (dense) cutis of broadly ellipsoid up to 16 µm wide hyphae mixed with cylindrical, up to 8 µm wide hyphae, with rounded apex, slightly gelatinized, smooth, sometimes ascendant and forming small trichodermic patches; subpellis formed by broadly ellipsoid, densely septate hyphae up to 10 µm wide (Fig. 5a–h). Pigments brownish, intracellular. Stipitipellis of cylindrical, up to 6 µm wide hyphae (Fig. 6a). Stipititrama of up to 16 µm wide hyphae. Caulocystidia usually present, clustered, versiform, thin-walled, colorless, up to 6 µm wide (Fig. 6b). Clamp-connections absent everywhere.

FRANCE • Savoie, Bourg-Saint-Maurice, Arc 1800, under Alnus alnobetula (Ehrh.) K. Koch, 27 August 2006, leg. P-A Moreau (LIP PAM06082703, epitype of C. pillodii). NORWAY • Innlandet, Lesja, Joris delta, Flommarkskog med gråor, 12 August 2021, leg. T.E. Brandrud, S. Khalsa & P.G. Larsen (O-F:258872). POLAND • Western Tatra Mts., Sarnia Skala massif, northern slope, at the top, alt. 1375 m, Pinetum mugi carpaticum, on litter, 22 August 2001, leg. A. Ronikier (KRAM-F:53298); ibidem, 8 September 2001, leg. A. Ronikier (KRAM-F:53314). RUSSIA • Republic of Karachay-Cherkessia, Teberda State Nature Reserve, Dzhemagat Gorge, 1881 m, on the soil on the border of floodplain forest and meadow, 13 August 2009, leg. E.S. Popov, det. O.V. Morozova (LE 254346).

Collybia pillodii was described and illustrated by the French mycologist Lucien Quélet (1890) from Jura hills as a very small entirely violet species with a campanulate to convex pruinose pileus, whitish pileus margin, adnate and distant lamellae paler than the pileus, a fistulous and slender rooting stipe bristling at the base with white and radiant rhizoids, very thin violaceous context, and minute subglobose to ovoid spores. He reported its spores as minutely aculeate (“finement aculeolée”), but his observation was probably incorrect because it was not confirmed by all the subsequent authors who observed always smooth spores. The species was later described in detail by Kühner and Romagnesi (1954), who suggested its possibly placement in Tricholoma section Liposperma. Favre (1960) believed that the species was better placed within the tribe Orcellées (see below) in sense of Kühner (see Kühner and Romagnesi 1953, Kühner 1969 = Entolomataceae).

When Singer (1938) described Baeospora oligophylla he did not compare it to Collybia pillodii described 48 years earlier by Quélet (1890). He merely noted that the latter species probably also belongs to the genus Baeospora Singer. Then, when Singer (1942) established the genus Pseudobaeospora for the species of Baeospora with dextrinoid spores, he included only B. oligophylla. Both in the first and in second edition of “The Agaricales in modern taxonomy” (Singer 1951, 1962), he placed the genus Pseudobaeospora as closely related to Lepiota (following the suggestions by Locquin 1952), and still monotypic with a single species, P. oligophylla; while Collybia pillodii was classified as a probable member of Collybia section Iocephalae Singer.

The two species were placed together in one genus for the first time by Horak (1964), who made an invalid combination Pseudobaeospora pillodii, validated later by Wasser (1980). In the third and fourth editions of “The Agaricales in modern taxonomy”, Singer (1975, 1986) also followed Horak’s opinion including the two names in one genus.

Since type collections of Quélet’s Collybia pillodii and of Baeospora oligophylla (presumably kept in LE) do not exist (Olga Morozova, pers. comm.) and their very concise original descriptions are difficult to interpret there has been some speculation about the relation between P. pillodii and P. oligophylla and depending on the authors these taxa were treated as two independent species (Singer 1986; Bas 2002, 2003) or just one (Horak 1964, 1968, 2005; Redhead 1982; Ronikier and Moreau 2007; Morozova and Popov 2013; Desjardin et al. 2014; Voto 2021).

Bas (2003) was the only author who provided a comparison of P. pillodii and P. oligophylla. He mainly relied on his own collections, the original description of P. oligophylla (Singer 1938), the exhaustive descriptions of Collybia pillodii by Kühner (in Kühner and Romagnesi 1954) and of the Swiss specimens of P. pillodii by Horak (1968). He distinguished P. oligophylla by a cutis type of pileipellis with cystidioid, repent to ascending, terminal elements compared to a simple undifferentiated cutis of P. pillodii. These conclusions were later questioned by Ronikier and Moreau (2007) who, after finding and studying specimens at various stages of development, proposed to consider both taxa as synonyms, giving the priority to P. pillodii as an older name. They concluded that the cutis-like pileipellis observed by Bas as characteristic of P. pillodii is only the tardive stage of the subtrichodermic pileipellis found in young specimens named as P. oligophylla.

Our analyses, which did not take into account the developmental stage of the basidiomes as they were carried out on only herbarium (fungarium) material, show that regardless of the presence or absence of ascending pileocystidioid terminal elements (which in our opinion depends more on the point of the pileus where the sampling is taken) all the collections are molecularly conspecific (Figs 2, 3), and thus supporting the conclusions of Horak (1964, 1968), Redhead (1982), and Ronikier and Moreau (2007). Accordingly, Quélet’s illustration of Collybia pillodii (Quélet 1890) is selected above as lectotype and a sequenced French collection (LIP PAM06082703), also studied in Ronikier and Moreau (2007), is established as epitype of C. pillodii.

According to the results of our study, P. pillodii is characterized by very small to small, very slender (e.g., pileus 1–15 mm wide, stipe 10–55 (70) × 0.2–2.0 mm), brownish lilac, entirely purplish coloured basidiome except its whitish pileus margin, spaced lamellae (L = 12–19, l = 0–3), a non-striate pileus, a stipe with basal rhizoids, subglobose to broadly ellipsoid spores (on average not exceeding 4 µm in length), basidia prevailingly tetrasporic (few specimens have been found with 2-spored basidia only, e.g., Kühner and Romagnesi 1953) as well with 2- and 4- spored basidia sometimes even on one lamella (e.g., Ronikier and Moreau 2007, our observations), cheilocystidia absent (but reported as basidioliform by Horak 1964 or filiform by Singer 1938), suprapellis as a cutis with (subtrichodermoid) or without ascending terminal (pileocystidioid) elements, that is negative to pallid or turns very pale grayish-greenish in KOH, clamp-connections absent. Kühner (in Kühner and Romagnesi 1954) pointed out that all the specimens he examined were haploparthenogenic (apogamic, with uninucleate hyphae).

Pseudobaeospora pillodii was originally described from a deciduous mountain forest (Quélet 1890) and is often reported from Alnus Mill. litter (Kühner in Kühner and Romagnesi 1954; Favre 1960; Bas 2003; Ronikier and Moreau 2007; von Bonsdorff et al. 2012 etc.) as well as from subalpine coniferous litter (Singer 1938; Kühner in Kühner and Romagnesi 1954; Horak 1964, 1968; Bresinsky and Schmid-Heckel 1982; Redhead 1982; Ronikier and Moreau 2007; Læssøe 2008, 2012; Morozova and Popov 2013; Christan and Rexer 2020) or other subalpine plant communities, such as Salix L. shrubs, the Athyrio-Sorbetum association (Bujakiewicz 2004) or Rhododendron L. shrubs (Wasser 1980). As suggested by Ronikier and Moreau (2007), it might be a nitrophilic saprotrophic species, to be sought in other nitrogen-rich organic substrates. It is reported from Asia (Siberia), Europe (France, Germany, Norway, Poland, Switzerland, Russia), and North America (Canada) (Singer 1938; Horak 1964, 1968; Redhead 1982; Bas 2003; Ronikier and Moreau 2007; Læssøe 2008, 2012; Morozova and Popov 2013; Christan and Rexer 2020; Voto 2021). Jamoni (1997) described a Pseudobaeospora collection (on only one basidiome in very poor condition) from subalpine Piedmont (Italy) near Alnus incana which may represent P. pillodii due to its tetrasporic basidia, clampless hyphae and absence of cheilocystidia, but unfortunately the specimen can no longer be found in any fungarium.

There are several interesting observations on P. oligophylla or P. pillodii which were not confirmed by other authors and require further investigation. Favre (1960) and Kühner (1980) reported a lilac-purplish or pinkish spore deposit for P. pillodii. Bon (in Jamoni and Bon 1996) cited some French collections of P. pillodii consisting of only albinotic basidiomes, but these may represent white Pseudobaeospora species which were described later (e.g., Bas 2002, 2003).

For a single collection named P. oligophylla in sense of Bas, the collector, N. Dam, noted that some rhizoids were connected to small ochraceous tubers (presumably sclerotia) in the soil, as in Collybia tuberosa (Bull.) P. Kumm. (cited in Bas 2003; Clitocybaceae Vizzini, Consiglio & M. Marchetti, Tricholomatineae).

The presence of bisporic and/or tetrasporic basidia in basidiomes and/or collections of the same species found in P. pillodii should not be surprising as, apart from P. wipapatiae and Agaricus fuscolilacinus Peck (that according to Desjardin 2004 belongs to Pseudobaeospora) for which only bisporic basidiomes are known (Desjardin 2004; Desjardin et al. 2014), some other species, e.g., P. brunnea, P. cyanea, P. lilacina, show a mixture of (1)2- and 4-spored basidia (Bas 2003; Arauzo 2011a; Wu et al. 2017; Voto 2021), P. pyrifera collections with 2–4 spored basidia and others only 4-spored (see below), and for P. taluna three collections from Tasmania are 4-spored, and one from Victoria, 2-spored (Craig et al. 2023).

Pseudobaeospora pillodii was the only clamp-less species reported from Europe so far before this publication (see below). Pseudobaeospora sp. described in Adamčík and Ripková (2004b) based on a single clamp-less basidiome collected among Molinia sp. under Alnus glutinosa (L.) Gaertn., from Czech Republic, is distinguished mainly by a very minute basidiome (pileus 4.5 mm wide and stipe 20 × 0.6 mm), pileus with 1–1.5 mm long marginal striation, very sparse lamellae (L = 11, l = 0–1), well-developed versiform to irregular cheilocystidia 21–33 × 2.5–6.0 µm, strictly bisporic basidia, a pseudoparenchymatic subpellis of 9–24 µm wide hyphae, and spores longer than 4 µm on average.

Agaricus (Tricholoma) microsporus Ellis (Nom. illegit., Art. 53.1, Shenzhen Code) is, based on the data provided by Desjardin (2004) who examined its holotype collection (“this species forms violet basidiomes with a thin cutis-type pileipellis that overlays a subcellular hypodermium, has dextrinoid basidiospores 4–5 × 3.5–4.5 µm, lacks cheilocystidia, lacks clamp connections, and does not discolor in KOH”), and the original description (Ellis 1874, stipe with “long, spreading, pale-yellowish hairs at base”), a possible older synonym of P. pillodii.

Figure 4. 

Basidiomes of some sequenced Pseudobaeospora collections. a P. calcarea (LIP PAM06090111-FR2013078); b P. cyanea (GDOR M3986); c P. laguncularis var. denudata (LIP PAM99101004-FR2013079); d P. pillodii (KRAM F-53314); e P. terrayi (SAV-F:3317, holotype); f P. terrayi (SAV-F:20813). Lectotype of. C. pillodii; g Quélet’s original plate, pl. XV, fig. 4. Photos: a, c by P.A. Moreau; b by D. Gisotti; d by A. Ronikier; e, f by S. Jančovičová.

Figure 5. 

Pseudobaeospora pillodii , microscopic features. Pileipellis. a–c (KRAM F-53298); d (KRAM F-53314); e, f (LE 254346); g, h (O-F:258872); a–h in ammoniacal Congo red. Scale bars: 10 µm (a–c); 20 µm (e–h). Photos by L. Setti.

Figure 6. 

Pseudobaeospora pillodii , microscopic features. Stipitipellis. a (KRAM F-53298); b (KRAM F-53314). Spores; c (KRAM F-53298); d (KRAM F-53314); e (LE 254346); f (O-F:258872); a–f in ammoniacal Congo red. Scale bars: 10 µm (a); 20 µm (b); 5 µm (c–f). Photos by L. Setti.

Pseudobaeospora deceptiva differs from P. pillodii by larger basidiospores, tetrasporic basidia and lack of rhizoids and from the other members of the genus by its unique phylogenetic position.

the species epithet derives from the Latin word deceptivus (= misleading) and refers to its strong resemblance to P. pillodii.

ITALY • Abruzzo, Ponte di Platano (CH), on the ground, on rotting leaves of Alnus alnobetula [= A. viridis (Chaix) DC.], 28 August 2000, leg. et det. G. Robich, as P. pillodii (MCVE:15315).

Habit collybioid. Pileus 5–20 mm broad, conical campanulate to plano-convex, expanding plane with an obtuse umbo, margin at first slightly crenulated-undulate, not striate, flattened to revolute in mature specimens, surface dry, pruinose to minutely felted, not or only slightly hygrophanous, dark violaceous (Dark Bluish Violet, Blackish Violet, Plate X; Navy Blue, Plate XXI; Dusky Violet-Blue 1, Plate XXIII), with a whitish paler margin. Lamellae deeply emarginate with slightly decurrent tooth to almost free, spaced, L = 18–20, 1 = (1–)3–5(–7), rather thick, narrow to ventricose, 1.5–2 mm broad, purple-lilaceous (Pale Amparo Purple, Light Amparo Purple, Plate XI; Light Mallow Purple, Mallow Purple, Plate XII; Pale Vinaceous, Plate XXVII), with a concolorous, entire to slightly irregular/eroded edge. Stipe 40–60 × 1.5–2.5 mm, cylindrical, flexuous, solid to slightly hollow at maturity, not filiform, concolorous with the pileus, at first sparsely but entirely covered by minute silky whitish fibrils and flocks, then evidently fibrillose only at apex (Fig. 7a), base radially strigose. Context violaceous. Pileus surface showing a negative reaction with a drop of 5% KOH. Smell indistinct. Taste mild. Spore-print white.

Spores (3.9–)4.2–4.6–5.0(–5.4) × (2.6–)3.1–3.4–3.8(–4.1) µm (64/2/2), Q = (1.18–)1.25–1.36–1.46(–1.63), V = (15.4–)20.9–28.9–36.8(–46.5) μm³, broadly ellipsoid to ellipsoid, colorless, smooth, in L4; contents granulose or with one or two oil-droplets (guttules), at first thin-walled and inamyloid, but maturing after liberation and becoming thick-walled up to 0.8 µm, dextrinoid, congophilous and cyanophilous; hilar appendix prominent, 0.8–1 µm long (Fig. 7e). Basidia 15–19 × 6–7 µm, clavate, tetrasporic, with sterigmata up to 3 µm long. Hymenophoral trama regular to subregular, consisting of hyphae up to 8 µm wide, colorless in L4. Hymenial cystidia not observed. Pileipellis: slightly gelatinized, a cutis composed of loose, 2.5–4 µm wide hyphae; hyphal terminations towards the pileus margin often ascending and arranged in subtrichodermic patches, subcylindrical, smooth, apically rounded, up to 8 µm wide; subpellis consisting of up to 8 µm wide cylindrical hyphae (Fig. 7b–d). Pigment brownish, intracellular. Stipitipellis consisting of 3–7 µm wide, non-dextrinoid parallel-oriented cylindrical hyphae. Stipititrama similar to stipitipellis structure but hyphae up to 10 wide. Caulocystidia present (observed at stipe apex), 10–40 × 5–10 µm, usually in tufts, thin-walled, colorless, often irregularly shaped, clavate, lageniform, sinuous, lobed, sometimes catenulated, with rounded apex (Fig. 7f). Clamp-connections absent in all parts.

Terrestrial, so far known only from Italy.

ITALY • Piemonte, Val d’Otro, Alagna Valsesia (VC), 10 September 1994, leg. et det. P.G. Jamoni, as P. pillodii (MCVE:4905).

Pseudobaeospora deceptiva is a species difficult to distinguish from P. pillodii without careful observation of some morphological characters: it shows larger basidiomes (pileus 5–20 mm and stipe up to 2.5 mm wide), a stipe without basal rhizoids, spores on average longer than 4.5 µm, and frequent subtrichodermic structures near the pileus margin. The two collections studied here were previously identified as P. pillodii. The difference between the spore dimensions of the two species is even more worthy of attention if we consider that while the collections of P. pillodii show a variable percentage of bisporic basidia, those of P. deceptiva are consistently tetrasporic. The ITS sequences do not unambiguously separate the two species (Fig. 3) but they are clearly different in the multigene analysis where also their SSU and LSU sequences are present (Fig. 2).

Pseudobaeospora sp. described in Adamčík and Ripková (2004b) shares with P. deceptiva the colours of the basidiomes, the clamp-less hyphae, spores longer than 4 µm in average and a suprapellis containing numerous ascending to erect terminal elements (pileocystidia according to Bas 2003) but is distinguished by a very minute basidiome (pileus 4.5 mm wide and stipe 20 × 0.6 mm), pileus with 1–1.5 mm long marginal striation, very sparse lamellae (L = 11, l = 0–1), well-developed versiform to irregular cheilocystidia, different length/width spore ratio (Q = 1.08–1.29), bisporic basidia, and a pseudoparenchymatic subpellis of 9–24 µm wide hyphae.

Among the extra European clamp-less species, P. defibulata Singer described from Argentina on rotten leaves of dicotyledonous trees differs by a smaller pileus (3–7 mm wide), a thinner stipe (0.2–0.6 mm thick), a pale livid to partly almost white pileus, sparse lamellae (L = 13, l = 1), smaller spores, 4.0–4.2 × 3.0–3.2 µm, and a suprapellis of only horizontal hyphae (Singer 1963). Pseudobaeospora citrina Rawla from India, is distinguished by small basidiomes (pileus 5–10 mm, stipe 10–15 × 1 mm) greenish yellow to citrine, pileipellis a trichoderm of repent up to 7 µm wide hyphae, with fasciculate, slightly thick-walled, 28–140 × 3–5 µm hairs (pileocystidia) (Rawla and Arya 1991; Bas 2003).

Figure 7. 

Pseudobaeospora deceptiva (MCVE:15315, holotype). a Basidiomes; b–d pileipellis; e spores; f caulocystidia; b–f in ammoniacal Congo red. Scale bars: 20 µm (b–d); 5 µm (e); 10 µm (f). Photos by L. Setti.

GERMANY • Bavaria, Lower Franconia, Kitzingen, ‘Klosterforst’, 10 September 1995, leg. L.G. Krieglsteiner s.n. (holotype L; isotype REG).

Krieglsteiner (1999: 37, photo G. Wölfel); Chaillet et al. (2007: 7, photo G. Moyne); Krieglsteiner (2010: 74); Arauzo (2011a: p. 34–36); Morozova and Popov (2013: pl. I-2); Caillet et al. (2018: 71).

Bas and Krieglsteiner (1998: 204–205); Adamčík and Bas (2002: 272–274, as P. mutabilis); Bas (2003: 175–177); Chaillet et al. (2007: 5–7); Arauzo (2011a: 34–35); Morozova and Popov (2013: 131–132, in Russian).

Habit collybioid. Pileus 8–26 mm broad, conical campanulate to plano-convex, finally flattened with an obtuse umbo, margin at first slightly crenulated-undulate, not striate, flattened to revolute in mature specimens, surface dry, pruinose to minutely felted, not or only slightly hygrophanous, purplish brown (Pinkish Vinaceous, Deep Vinaceous, Plate XXVII), dark vinaceous brown to pinkish brown at centre (Dull Magenta Purple, Schoenfeld’s Purple, Indian Lake, Plate XXVI) with a paler margin (brownish pink, Pale Vinaceous, Plate XXVII). Lamellae deeply emarginate with slightly decurrent tooth to almost free, moderately crowded, L = 18–23, 1 = (1–)2–5, rather thick, narrow to ventricose, 2–3 mm broad, reddish violaceous to violaceous pink, becoming lilacinous ochraceous (Lilac, Plate XXV; Pale Rose-Purple, Rosolane Pink, Plate XXVI) to greyish ochraceous, with a concolorous, entire to slightly irregular edge. Stipe 25–50 × 1.2–3.0 mm, cylindrical, solid to slightly hollow at maturity, concolorous with lamellae, dark vinaceous red-brown, purplish brown, at first sparsely but entirely covered by minute silky whitish fibrils and flocks, then evidently fibrillose only at apex, with long whitish strigose felt hair at the base (Fig. 8a, c, d). Context violaceous red, darkening when bruised. Pileus surface showing a bluish-green reaction with a drop of 5% KOH. Smell indistinct. Taste mild. Spore-print white.

Spores (Italian collections, mono-, bi- and tetrasporic) (3.5–)3.8–4.3–4.7(–5.8) × (2.5–)3.0–3.5–4.0(–5.0) μm (64/2/2), Q = (1.00–)1.10–1.22–1.35(–1.63), V = (13.5–)18.3–28.6–38.9(–73.8) μm³, (Slovak collections, tetrasporic) (2.9–)3.2–3.5–3.8(–4.7) × (2.4–)2.9–3.1–3.3(–3.9) μm (160/3/3), Q = (0.96–)1.04–1.12–1.20(–1.36), V = (10.0–)14.2–17.8–21.3(–31.6) μm³, globose, subglobose to subelliptical, sometimes larmiform (drop-like), colorless, smooth, with the tendency to agglomerate in tetrads or in greater numbers (clusters) (Figs 9h, 10j–l), contents granulose or with one or two oil-droplets (guttules), at first thin-walled and inamyloid, but maturing after liberation and becoming thick-walled (0.7–1.3 µm thick), dextrinoid, congophilous and cyanophilous; majority of spores (80–90%) turns green-blue sea in L4 (Fig. 9h). Basidia 21–25 × 5.2–7.2 µm, clavate, sometimes constricted in the middle, in some collections mostly tetrasporic, but also 1–2 sporic, in others strictly tetrasporic, sterigmata up to 4 µm long. Crassobasidia (sclerobasidia) scattered, with thick dextrinoid, strongly congophilous walls (0.8–1 µm thick) turning green-blue sea in L4 (Fig. 9c). Hymenophoral trama subregular to irregular, slightly intertwined (intricate), consisting of hyphae up to 14 µm wide (Fig. 9d). Cheilocystidia 15–25 × 5.8–9.7 × 2.4–5.0 µm, abundant and densely packed, mostly broadly clavate to sphaeropedunculate, sometimes lageniform, subutriform, thin-walled, colorless (Figs 9e–f, 10d–f). Pleurocystidia absent. Pileipellis: suprapellis consisting of loosely arranged chains of inflated pyriform to broadly clavate elements (transition between trichoderm and epithelium) up to 15 µm wide (Figs 9a, b, 10a–c), overlying on a subpellis made up of radially to irregularly arranged chains of largely ellipsoid to cylindrical hyphae, 7–10 µm wide, with minutely yellow-brown encrusting extracellular pigments and intracellular pigments which turn pale greenish blue in KOH (dried material). Pileitrama made up of non-dextrinoid cylindrical hyphae up to 10 µm wide. Stipitipellis consisting of 2–7 µm wide, non-dextrinoid cylindrical hyphae. Stipititrama similar to stipitipellis but hyphae up to 11 wide. Caulocystidia present (observed at stipe apex), 10–30 × 6.7–11 µm, usually clustered in tufts, thin-walled, colorless, narrowly pyriform, clavate, lageniform, sometimes irregularly shaped, often catenulated, apically rounded (Figs 9g, 10g–i). Clamp-connections present.

Terrestrial, single or in small groups (gregarious), rarely subfasciculate. Known from France, Germany, Italy (the present study), The Netherlands, Spain, Norway, Estonia, and Sweden (see collections in Fig. 3) and Slovakia (as P. mutabilis).

ITALY • 11 December 2009, Punta Ala (Castiglione della Pescaia, GR), in a mixed forest of Quercus ilex L. and Juniperus oxycedrus ssp. macrocarpa (Sm.) Neilr., leg. L. Setti (AMB 18729); 23 November 2016, Castelporziano (Ostia, RM), in a mixed forest of broad-leaved trees, leg. G. Consiglio & A. Gennari (AMB 18730). SWEDEN • Dalarna, 4 September 2018, leg. E. Larsson (GB:0160633) (as P. pillodii). SLOVAKIA • Záhorská níñina lowland, Abrod National Nature Reserve, Závod village, among the tall vegetation of Molinia caerulea (L.) Moench, near solitary Betula and Frangula alnus Mill., 12 August 1998, leg. S. Adamčík, V. Stanová & A. Viceníková (SAV-F:3518, holotype of P. mutabilis); • Biele Karpaty Mts., 1.5 km E of Nová Bošáca, Blažejová Nature Monument, on soil among the grass, 30 July 2005, leg. S. Adamčík (SAV-F:3525, as P. mutabilis); • ibidem, 27 September 2005, leg. V. Kučera, (SAV-F:3524, as P. mutabilis); • Biele Karpaty Mts., Blažejová Nature Monument, Nová Bošáca village, the settlement of Španie, 29 June 2020, leg. S. Adamčík (SAV-F:20580, as P. mutabilis); • Biele Karpaty Mts., Krivoklátske lúky, 20 July 2020, leg. S. Adamčík (SAV-F:20589, as P. mutabilis).

Pseudobaeospora pyrifera was originally described from Southern Germany (Bavaria, Lower Franconia) and The Netherlands (Bas and Krieglsteiner 1998). Krieglsteiner (1999) reported five additional collections from the type locality (Lower Franconia) and seven collections from three other localities. At the type locality he found it sometimes to be the most abundant fungal species. It has been found in moist woods (Pruno-Fraxinetum), grasslands (Cirsio tuberosi-Molinietum) and a Juniperus stand, often together with Hygrocybe, Entoloma, Geoglossum and Ramariopsis species. The species has been later reported also from Spain, Iurreta (Bizkaia), locality of the Basque Country (N Spain), in the litter of Chamaecyparis lawsoniana (A. Murray) Parl. plantations (Arauzo 2011a), from France (Haute-Saône and Doubs) in dry lawns (Chaillet et al. 2007; Caillet et al. 2018) and North-western Russia (Novgorod oblast, Batetsky district) in a meadow (Morozova and Popov 2013). Pseudobaeospora pyrifera was included in the CHEGD fungi (the acronym of the constituent taxa: Clavariaceae, Hygrophoraceae Lotsy, Entolomataceae, Geoglossaceae Corda and Dermoloma) by Caboň et al. (2021). CHEGD fungi are a particular group of macrofungi which is characteristic of traditionally managed and undisturbed European grasslands, and which are often the dominant soil fungi in these habitats.

Pseudobaeospora mutabilis Bas & Adamčík from Slovakia was said to have many characters in common with P. pyrifera Bas & L.G. Krieglst. (Adamčík and Bas 2002; Bas 2003; Adamčík et al. 2007) but distinguished by a pileipellis structure as a transition between hymeniderm and epithelium. Moreover, its basidiomes seem to be somewhat sturdier (pileus 7–13 mm in diameter, stipe 20–30 × 1–2 mm) and the lamellae less crowded (L = 18, 1 = 1–3), KOH reaction very variable (inde nomen), on fresh material grey, on dry specimens pale green but sometimes at first violaceous. All the here sequenced collections of P. mutabilis (holotype included, SAV-F:3518) form a highly supported clade together with those of P. pyrifera [isotype included, 10-IX-1995, L. Krieglsteiner (REG)] both in the ITS (Fig. 3) and multigene analyses (Fig. 2). Accordingly, P. mutabilis is here considered as a younger synonym of P. pyrifera. Bas (2003) had even inserted the two species, which we now consider synonymous, into two different groups of his intrageneric sectioning: P. mutabilis in the Celluloderma group (basidiome coloured, clamp-connections present, cheilocystidia absent or present, pileipellis hymenidermoid) together with P. celluloderma; P. pyrifera in the Pyrifera group (basidiome coloured, clamp-connections present, cheilocystidia present and conspicuous, pileipellis not hymenidermoid) together with P. jamonii and P. laguncularis. Voto (2021), in first editions of his online keys to Pseudobaeospora, included P. mutabilis in his sect. Anistoderma (pileipellis hymeniform to ephitelioid) and P. pyrifera in sect. Pseudobaeospora subsect. Pseudobaeospora (pileipellis of principally short and inflated to broad hyphae). This must make us reflect on the fact that in the past too much importance has been given to the structure of the pileipellis both as a character to delimit intrageneric taxa and to distinguish species. The discrepancies in observations of the pileipellis structure might be sometimes a result of analysis of the basidiomes in different stages of development or are due to observations from different parts of the pileus (Adamčík et al. 2007; Ronikier and Moreau 2007).

Pseudobaeospora pyrifera is easily identifiable due to a unique combination of characters: violaceous pink tinges present all over the basidiome, the pale green to greenish blue reaction of pileus surface in KOH, mainly clavate cheilocystidia, pileipellis consisting of repent chains of inflated elements, and very small subglobose spores (Bas and Krieglsteiner 1998; Bas 2003; Arauzo 2011a). It contains peculiar metabolites named pyriferines A–C, which have an unusual eight-membered N/O-acetal ring, derived from L-glutamic acid (Quang et al. 2008). Adamčík et al. (2007) noted in some habitats the occurrence of collections with reddish brown basidiomes (see also our Fig. 8a, collection AMB 18729), instead of purplish violaceous ones, and they demonstrated that the colour of basidiomes was not affected by soil pH. Colour change to bluish grey on surfaces of basidiomes reported in original description of P. mutabilis (Adamčík and Bas 2002) was later not confirmed as a consistent character and might be due to local context pigment degradation rather than oxidation (Adamčík et al. 2007).

Macro- and micromorphology of the Italian collections are fully consistent with the original description (Bas and Krieglsteiner 1998; Bas 2003) and French (Chaillet et al. 2007), Spanish (Arauzo 2011a) and Russian (Morozova and Popov 2013) collections, excepted for the spores that are slightly longer [3.8–4.7 × 3.0–4.0 µm (on average 4.3 × 3.5 µm) vs 2.8–3.7(–4.2) × 2.6–3.5(–3.8) µm, vs 3.5–4.0 × 4.0–4.5 µm, vs 3.1–4 × (2.8–) 3.1–3.6 μm (on average 3.58 × 3.25 µm), and vs 2.9–3.7 × 2.6–3.2 µm, respectively] and subglobose to broadly ellipsoid instead of globose to subglobose (Qm = 1.22 vs 1.05–1.10, and 1.1, respectively). These sporal size discrepancies can be explained by the possible different percentage of (mono-)bisporic basidia on tetrasporic ones between the different collections. In fact, we report below the spore measurements summing the Slovak collections (“P. mutabilis”, which are exclusively tetrasporic) and Italian collections (which are mono-bi-tetrasporic): P. pyrifera+P. mutabilis – spores (2.9–)3.2–3.7–4.2(–5.5) × (2.4–)2.9–3.2–3.6(–4.7) μm (224/5/5), Q = (0.96–)1.05–1.15–1.26(–1.63), V = (10.0–)12.9–20.9–28.8(–65.2) μm³.

In this way the spore values ​​are very close to those reported in the literature. It is also worth to mention, that part of the discrepancies in published microscopic descriptions are due to an underestimation of the importance of the number of spores produced on the basidia.

In Europe P. jamonii Bas, Lalli & Lonati from Italy (Piedmont, Monte Rosa 1300 m, and Abruzzo) (Jamoni and Bon 1996; Bas et al. 2002; Bas 2003) seems to be the macromorphologically closest relative of the present species. It differs, however, by the more elongate clavate to (sub)lageniform, cylindrical or irregularly shaped cheilocystidia (15–43 × 4–10 μm), the presence of a distinct suprapellis of comparatively narrow hyphae, slightly larger and slightly more ellipsoid spores (3.2–4.0 × 2.8–3.5 μm, average Q = 1.10–1.15), and a different KOH reaction of the context of the stipe (green).

Pseudobaeospora basii Adamčík & Ripková from Slovakia has a very similar microscopic structure but its basidiomes lack any purple or lilac tinges (Adamčík and Ripková 2004a). Unfortunately, attempts to sequence its holotype collection (SAV-F:3506) did not lead to obtaining a good ITS sequence to compare to.

Pseudobaeospora dichroa Bas (reported from England and Spain) has a pileus surface turning reddish purplish in KOH; pileipellis of often erect, catenulate hyphae near the centre, sometimes with a thin suprapellis, and towards margin of broad repent hyphae. L = 16–30, l = 3–5; pileus and lamellae with shades of red when dried; spores 3.0–4.0 (–4.3) × 2.7–3.5 µm, average Q 1.10–1.20 (1.25); cheilocystidia 10–45 × 3.5–10 (–17) µm, (often irregularly) clavate to lageniform, sometimes filiform, abundant to sparse or absent, sometimes with violaceous content (Bas 2003; Arauzo 2011a).

Pseudobaeospora laguncularis Bas (reported from England, France, Germany, Spain) is very well characterized by the abundant, very slender cheilocystidia, at present unique in the genus. So far it is also the only species with small, scattered, refractive bodies turning red or red brown in KOH on caulocystidia and cheilocystidia, and sometimes also on the pileipellis, and with distinct, albeit sometimes sparse pileocystidia (Bas 2003; Arauzo 2011a; Clesse 2012). Pseudobaeospora laguncularis var. denudata Bas differs from the type by lacking the suprapellis of narrow hyphae. The collection of P. laguncularis var. denudata here sequenced, coming from the same locality of the type (topotype) [LIP PAM99101004, France, Savoie, Billième, forêt de Lierre, sous Buxus sempervirens L. et Quercus pubescens Willd. sur calcaire, alt. 400 m 10 octobre 1999, leg. Maurice Durand & Pierre-Arthur Moreau, 45.708663, 5.810281, Fig. 4c] is molecularly distinct from all the other sequenced species (Figs 2, 3).

Among the non-European species, P. chilensis E. Horak from Chile differs by tiny, very slender basidiomes, inconspicuous, narrow cheilocystidia, and narrower pileipellis elements (Horak 1964).

Pseudobaeospora wipapatiae from Hawaii, differs in forming deep ruby-colored basidiomes, with a pileus rugulo-striatulate nearly to disk, two-spored basidia, irregularly cylindrical to clavate or irregular in outline, sometimes mucronate, amyloid cheilocystidia, an irregular hymeniderm pileipellis with abundant erect pileocystidia and tissues that initially turn deep ruby then change to lilac grey in 3% KOH (Desjardin et al. 2014).

Agaricus fuscolilacinus Peck from Adirondack Mts. of New York (USA), based on the analysis on type material made by Desjardin (2004), who considers the species to belong to Pseudobaeospora, is distinguished by brownish lamellae, ellipsoid to lacrymoid bigger spores, 4.2–6.8 × 3.2–4.0 µm (on average 5.2 ± 0.6 × 3.5 ± 0.2), Q = 1.2–2.0 (Qm = 1.5 ± 0.2), two-spored basidia, and lack of cheilocystidia.

Figure 8. 

Pseudobaeospora pyrifera . Basidiomes. a AMB 18729; b AMB 18730; c SAV-F:3518 (holotype of P. mutabilis); d–f SAV-F:3524. Photos: a, b by G. Consiglio; c–f by S. Jančovičová.

Figure 9. 

Pseudobaeospora pyrifera , microscopic features (AMB 18730). a, b Pileipellis; c crassobasidia; d hymenophoral trama; e, f cheilocystidia; g caulocystidia; h spores; a, b, e, g in ammoniacal Congo red; c, d, f, h in L4. Scale bars: 20 µm (a, d); 5 µm (b, c, e–h). Photos by L. Setti.

Figure 10. 

Pseudobaeospora pyrifera , microscopic features (collections named as P. mutabilis). Pileipellis. a SAV-F:20580; b SAV-F:20589; c SAV-F:3524. Cheilocystidia; d SAV-F:20580; e SAV-F:20589; f SAV-F:3524. Caulocystidia; g SAV-F:20580; h SAV-F:20589; i SAV-F:3524. Spores; j SAV-F:20580; k SAV-F:20589. l SAV-F:3524; a–l in ammoniacal Congo red. Scale bars: 10 µm (a–f, h–i); 20 µm (g). j–l. Photos by L. Setti.

(missing): ITALY • Piemonte, Monte Rosa, Alagna, bassa valle dell’Orto, about 1300 m, 3 September 1994, leg. P.G. Jamoni (Fungarium Jamoni).

(designated here, MBT10024683): Italy, Abruzzo, San Pietro, Isola del Gran Sasso (TE), 13 September 1995, leg. G. Lalli & G. Lonati (AQUI:10322).

Jamoni and Bon (1996: photo on cover, as form of P. pillodii), Bas et al. (2002: Fig. 1).

Jamoni and Bon (1996: 12–13), Bas (2003: 177–179), Bas et al. (2002: 32–35).

Spores (2.9–)3.2–3.5–3.8(–4.5) × (2.6–)2.9–3.1–3.3(–3.6) μm (64/1/1), Q = (0.97–)1.04–1.15–1.25(–1.52), V = (11.3–)14.4–17.8–21.2(–28.2) μm³, globose to subglobose, wall up to a 0.8 µm thick, smooth, colorless in L4: hilar appendix prominent, 0.8–1 µm long. Basidia 16–18 × 4.0–5.0 µm, tetrasporic, subclavate to cylindrical, sterigmata up to 4 µm long; crassobasidia very rare. Hymenophoral trama regular to subregular, consisting of up to 8 µm wide hyphae, colorless in L4. Cheilocystidia mainly clavate, hardly differentiated from the basidia, but also elongate clavate to (sub)lageniform, cylindrical or irregularly shaped, 25–32 × 8.3–10.3 µm. Pleurocistidia absent. Pileipellis: turning greenish brownish to pale green in KOH; suprapellis formed by broadly ellipsoid to broadly cylindrical elements, often emerging and then pileocystidia-like, sometimes slightly swollen, with rounded apex, smooth, up to 9 µm wide; subpellis slightly aeriferous, consisting of slightly gelatinized, smooth, subglobose to broadly cylindrical, up to 16 µm wide hyphae; pigments light brown, mainly intracellular. Stipitipellis composed of cylindrical, densely septate, up to 3 µm wide, longitudinal and parallel hyphae. Stipititrama of up to 10–12 µm wide hyphae, greenish in KOH. Caulocystidia at stipe apex scattered or clustered, 10–50 × 4–10 pm, filiform to narrowly clavate, subcylindrical or slender and somewhat irregular. Clamp-connections present mainly on the suprapellis hyphae and at the basidia and cheilocystidia bases.

ITALY • Abruzzo, San Pietro, Isola del Gran Sasso (TE), 13 Sept. 1995, G. Lalli & G. Lonati (AQUI:10322, neotype).

Both the holotype (private fungarium, Jamoni) and the isotype collections (L) are missing (Pier Giovanni Jamoni, pers. comm. and Nicolien Sol, Leiden, pers. comm., respectively). The Italian collection studied here (AQUI:10322) was included as part of studied material (paratype) in the protologue (Bas et al. 2002) and is selected as the neotype here.

This taxon was first time provisionally described as a peculiar form of P. pillodii with clamp-connections, cheilocystidia and tetrasporic basidia, from Alpine areas in Piedmont (northwestern Italy) in mixed forests (Alnus incana, Acer, Fraxinus, Fagus, Corylus, and Picea abies) often near Buxus (Jamoni and Bon 1996). It was then formally described as a new species (Bas et al. 2002) based on the previously cited Piedmont collections and a new collection from Abruzzi (Central Italy) and included by Bas (2003) in his European monographic work on the genus.

Both in the multigene (Fig. 2) and ITS analyses (Fig. 3), the neotype collection of P. jamonii is recovered as an independent species. In the multigene analysis, it is sister to a clade formed by P. wipapatiae and P. pyrifera (including P. mutabilis); in the ITS analysis, it is sister to a clade consisting of four environmental sequences of an undescribed probably new species from Portugal. Similarities and differences between this species and P. pyrifera are discussed above.

Figure 11. 

Pseudobaeospora jamonii , microscopic features (neotype, AQUI:10322). a–c Pileipellis; d, e cheilocystidia; f spores; a–f in ammoniacal Congo red. Scale bars: 20 µm (a); 10 µm (b–e); 5 µm (f). Photos by L. Setti.

ENGLAND • Surrey, Mickleham Downs, 19 June 1991, leg. A. Henrici (K(M) 17188).

Karasch (2004: 34 Abb. 6).

Bas (2003: 173–174), Adamčík et al. (2007: 370–372).

Spores (3.3–)3.7–4.0–4.4(–5.0) × (2.7–)2.9–3.2–3.5(–4.4) μm (64/2/2), Q = (1.00–)1.16–1.28–1.41(–1.61), V = (14.1–)15.9–21.5–27.2(–50.1) μm³, globose to subglobose or broadly ellipsoid, walls up to 0.8 µm thick, dextrinoid at maturity, smooth, colorless in L4; hilar appendix prominent, 0.8–1 µm long. Basidia 16 × 4 µm, tetrasporic, clavate, sterigmata up to 2.5 µm long. Hymenophoral trama regular to subregular, composed of globose to subglobose, broadly cylindrical, up to 22 µm wide hyphae, colorless in L4. Cheilocystidia 23–25 × 5–7 µm, thin-walled, poorly differentiated and similar to basidioles. Pleurocystidia absent. Pileipellis: suprapellis cellulodermic/epithelioid, composed of slightly gelatinized, smooth, globose to subglobose, up to 24 × 22 µm elements; subpellis like suprapellis structure but with 21 × 13 µm elements, with rare cylindraceous hyphae; pigments greenish, intracellular. Stipitipellis consisting of up to 4 µm wide, multiseptate, closely packed, longitudinal hyphae. Stipititrama like stipitipellis structure but with up to 12 µm wide hyphae. Caulocystidia 12–22 × 2–7 µm, numerous at stipe apex, single or in small clusters, scattered towards the stipe base, often multiseptate with terminal elements cylindrical to broadly clavate. Clamp-connections rare, scattered.

Specimen examined: SLOVAKIA, Vihorlatské vrchy Mts., ca. 1.5 km SW of the church, old pastures, Strihovce village, terrestrial, on flysh, 18 April 2003, leg. V. Kučera (SAV-F:3516). SWEDEN, Medelpad, Borgsjö, öster om Östby, Örtrik granskog (Medelpad, Borgsjö, east of Östby, Örtrik spruce forest), 3 September 1991, leg. L. Andersson (UPS-F: 623041) (as Pseudobaeospora pillodii).

Pseudobaeospora celluloderma is a well characterized species circumscribed by its minute and slender mycenoid basidiomes which are brightly purple to reddish violet when moist (reminding Laccaria amethystina Cooke), sometimes greyish vinaceous coloured; strongly translucently striate pileus when moist; lamellae concolorous with pileus; pileus surface in KOH pale brownish to pale pinkish-greyish, clamp-connections present (sometimes as pseudoclamps, Bas 2003); cheilocystidia absent or basidiole-like, and an irregular hymenidermic pileipellis (Bas 2002, 2003; Adamčík et al. 2007; Kalinina et al. 2020). It was reported in Europe from Austria, Denmark, England, Finland, France, Germany, Slovakia, Sweden, and Russia (Bas 2002, 2003; Karasch 2004; Courtecuisse and Lécuru 2006; Adamčík et al. 2007; Læssøe 2008, 2012; Hausknecht et al. 2012; Kalinina et al. 2020).

The sequences from two North American collections named P. celluloderma (KU058501, USA North Carolina, ECV5550/TENN 067659) and Pseudobaeospora sp. (KU058500, USA, Tennessee TENN 070699/CCB143666) (Figs 2, 3) are weakly supported as sisters related to the two European collections we have sequenced and studied, and probably represent one or two distinct undescribed taxa.

Figure 12. 

Pseudobaeospora celluloderma , microscopic features (UPS-F 623041). a–c Pileipellis; d cheilocystidia; e crassobasidia; f spores; a–f in ammoniacal Congo red. Scale bars: 10 µm (a, b, d); 15 µm (c); 5 µm (e, f). Photos by L. Setti.

SPAIN • Catalonia, Girona, La Selva, surroundings of Mas de Llagostera (UTM 31 T 0480 4622), 200 m, on acidic, humus-rich soil above granite, in forest with Pinus pinaster, Quercus suber, Arbutus unedo and Erica arborea, probably saprobic, 6 November 2002, leg. J. Carreras & M. Tabarés, (BCN SCM B-4742).

Arnolds et al. (2003: 69), Arauzo (2011a: 24, 26), Gisotti et al. (2021: fig. 1).

Arnolds et al. (2003: 66–68), Arauzo (2011a: 23, 25), Gisotti et al. (2021: 123–125).

Spores (4.0–)4.5–4.8–5.2(–5.4) × (2.9–)3.5–3.7–4.0(–4.2) μm (64/1/1), Q = (1.10–)1.21–1.31–1.40(–1.51), V = (19.7–)29.2–35.2–41.3(–48.0) μm³, broadly ellipsoid to ellipsoid, slightly amygdaliform in side view, walls up to 0.8 µm thick and dextrinoid at maturity, smooth, colorless in L4, hilar appendix prominent, 0.8–1 µm long. Basidia 21–25 × 6.5–8.0 µm, some with up to 1 μm thick wall (crassobasidia), tetrasporic, rarely bisporic to monosporic, clavate, sterigmata up to 4.5 µm long. Hymenophoral trama regular to subregular, composed of up to 12 µm wide cylindrical to inflated hyphae, colorless in L4. Cheilocystidia 15–30(–34) × 3–7(–11) µm, rare, scattered, basidiola-like to irregularly cylindrical, lageniform, sometimes lobed to furcate. Pleurocystidia present, very rare, similar to cheilocystidia but bigger, up to 56 × 12 µm. Pileipellis: suprapellis (at the pileus centre) a transition between trichoderm and epithelium consisting of loosely entangled ascending and erect pluriseptate hyphae, terminal elements broadly cylindrical, clavate to subglobose, up to 18 µm wide; towards the pileus margin it tends to become a cutis with repent hyphae; pigment abundant, brownish grey, bluish, intracellular and encrusting (extracellular), green in KOH; pileitrama consisting of up to 8 µm wide cylindrical hyphae. Stipitipellis consisting of 2–4 µm wide, multiseptate, parallel, cylindrical hyphae. Stipititrama similar to the stipitipellis structure but with 3–6 µm wide hyphae. Caulocystidia 10–70(–80) × 3.0–7 µm, filiform, sinuous, often multiseptate, sometimes irregularly lobed and furcate. Clamp-connections present everywhere.

ITALY • Liguria, Pegli (GE), 95 m, in an area of shrub-like Mediterranean vegetation with Pinus pinaster Aiton, Arbutus unedo L., Erica arborea L., Cistus salvifolius L., and Quercus ilex L., on poor acidic soil with serpentine bedrock, in the needle litter of P. pinaster, 6 December 2016, leg. D. Gisotti & F. Boccardo (GDOR:M3986).

The species was originally described from Spain (Arnolds et al. 2003; Arauzo 2011a) and then recently found in Liguria, Italy (Gisotti et al. 2021). Pseudobaeospora cyanea is clearly distinguished from the other species by a unique combination of features such as a bright bluish-purple pileus, pale lamellae and stipe, a trichodermic structure of the pileipellis (with inflated elements), green reaction of the pileipellis to KOH and well-developed cheilocystidia (Arnolds et al. 2003). Our microscopic analysis of the collection studied by Gisotti et al. (2021) (GDOR:M3986) revealed the presence of rare pleurocystidia which were not recorded by previous authors. Pleurocystidia were so far only reported for P. aciculifera Voto & Soop (Voto and Soop 2018), and P. taluna (Craig et al. 2023), two species of the southern hemisphere. Both Spanish and Italian collections were made in Mediterranean areas in winter, viz. Mediterranean hills with Pinus pinaster, Arbutus unedo and Erica arborea (Arnolds et al. 2003), and an area of shrub-like Mediterranean vegetation with P. pinaster, A. unedo, E. arborea, C. salvifolius, and Q. ilex (Gisotti et al. 2021), respectively. The morphology of the Spanish and Italian collections compared was completely consistent.

In the multigene analysis (Fig. 2) the most closely allied species is P. lilacina X.D. Yu, Ming Zhang & S.Y. Wu from China (Wu et al. 2017), which is distinguished by a pileus surface pale mauve, colonial buff when old, smaller spores 2.5–3.5(–4.5) × 3–5(–6.5) μm, cheilocystidia absent, and pileipellis hyphae not changing color in 5% KOH.

Pseudobaeospora pallidifolia Bas, A. Gennari & Robich from mossy coniferous forest in Tuscany (Italy) so far known only from the type locality, is similar to P. cyanea by the dark pileus with paler margin strongly contrasting with whitish to pinkish cream lamellae and the pale stipe, but differs by lack of cheilocystidia, and comparatively large and more elongated ellipsoid spores 4.4–6.4 × 3.3–4.4 μm, Q = 1.30–1.40 (Bas et al. 1997; Bas 2003).

Figure 13. 

Pseudobaeospora cyanea , microscopic features (GDOR M3986). a, b Pileipellis; c hymenium (basidia and cheilocystidia); d basidia; e spores; f hymenophoral trama; a–f in ammoniacal Congo red. Scale bars: 20 µm (a, b, f); 10 µm (c); 5 µm (d, e). Photos by L. Setti.

Pseudobaeospora calcarea was described from Switzerland occurring among and on mosses [mainly Hypnum cupressiforme Hedw., Dicranum scoparium Hedw., Hylocomium splendens (Hedw.) W.P. Schimp., and Pleurozium schreberi (Brid.) Mitt.] in coniferous woods (Pinus sylvestris with Quercus pubescens). It was placed into the informal Albidula group as circumscribed by Bas (2003), encompassing species with white to pale buff basidiomes, clamp-connections, absent cheilocystidia and pileipellis without inflated elements. This species differs from all others of this group by a very acrid taste, a negative reaction with KOH (no yellow discoloration) and the absence of clamp-connections in most of the trama and pileipellis hyphae (Clémençon and Ayer 2007). Adamčík and Jančovičová (2011) described P. terrayi, a minute, not moss-associated species from Slovakia, which was included in the Albidula group due to the white basidiome colour, despite the presence of cheilocystidia. The species was distinguished from P. calcarea by very small basidiomes (pileus 5–8 mm wide versus 7–20 mm), more distant lamellae (L = 11–18 versus 16–28), a mild taste, an occasional presence of an unpleasant fishy smell, a yellowish-greenish discoloration in 5% KOH, presence of cheilocystidia, which are somewhat basidia-like, but often broader and sometimes with distinctly thickened walls and/or incrusted surface, and clamp-connections present in all tissues.

In our ITS analysis (Fig. 3) three collections of P. calcarea, including a specimen from Switzerland (LIP PAM06090111), and two collections of P. terrayi (holotype included, SAV-F:3317) were found intermixed with each other in a strongly supported clade (PP 1.0, ML BP 92%), suggesting a possible conspecificity of P. calcarea and P. terrayi. Unfortunately, the holotype and isotype collections of P. calcarea (kept at LAU) have not been declared available for molecular analysis (Patrice Descombes, personal comm.). Multigene analysis is essential also to confirm that variability within this clade in the ITS region does not correspond to more than one species as documented in P. pillodii and P. deceptiva complex.

P. calcarea : SUISSE, Grisons, Alvaneu-Bad, ripisylve à Alnus incana, 1 September 2006, leg. Pierre-Arthur Moreau. 46.66591, 9.64329, (LIP PAM06090111). P. terrayi: SLOVAKIA, Laborecká vrchovina Mts., ca. 1 km NE of Svetlice village, the riverside meadow extensively used as pasture, on ground among ca. 15–30 cm tall herbal vegetation composed of Achillea millefolium L., Agrimonia eupatoria L., Agrostis capillaris L., Dactylis glomerata L., Daucus carota L., Festuca pratensis Huds., F. rubra L., Jacea pratensis Lam., Leontodon hispidus L., Lotus corniculatus L., Pimpinella saxifraga L., Plantago lanceolata L., Poa pratensis L., Thymus pulegioides L., Tithymalus cyparissias L., Trifolium repens L., Veronica chamaedris L. and Viola hirta L., 458 m, coord. 49°11'12.9"N, 22°02'55.8"E, 23 Oct 2007, leg. J. Terray (SAV-F:3317 holotype); Kremnické vrchy Mts., Tajov, pasture W of the village centre, 24 October 2020, leg. S. Adamčík (SAV-F:20813).