TAIWAN, Nantou county, south from Sun-Moon Lake, near Hua Lien, Lien-Hwa-Chi, 700 m a.s.l., on fallen angiosperm twig, leg. E. Langer, G. Langer, F. Oberwinkler, 10 Jul 1990 (TUB-FO 42565; isotypes in KAS and MSK).

Basidiomata effused, 1–5 cm in extent, membranaceous, discontinuous at the periphery. Hymenial surface minutely odontioid, cream-coloured, between aculei 50–130 μm thick. Aculei peg-like, conical or subcylindrical, entire or slightly penicillate apically, 35–70 μm long, 15–50(–70) μm diam., 8–14/mm. Margin abrupt or somewhat thinning out. Hyphal system monomitic, hyphae colourless, with clamps at all primary septa. Subicular hyphae forming a loose tissue, rarely branched, 3–4(–4.5) μm wide, with slightly thick to thick walls (0.5–1.2 μm thick), with scattered adventitious septa, smooth. Subhymenial hyphae in a dense tissue, richly branched, 2–3 μm wide, thin-walled, smooth or slightly encrusted. Capitate cystidia enclosed, 18–22 × 5.5–8 μm, sometimes with an adventitious septum in stem, thin- to slightly thick-walled. Projecting hyphae in aculei flexuous, apically obtuse, 90–130 μm long, 3–4 μm wide, originating from thick-walled subicular hyphae, with simple and clamped septa, often constricted at septa, walls thickened at base then gradually thinning toward apex, moderately encrusted. Basidioles clavate or bowling pin-shaped, 10–20 × 4.5–5.5 μm. Basidia narrowly utriform, 20–25 × 4–5(–5.5) μm, thin-walled, smooth, with four sterigmata 2–4 × 0.3 μm. Spores narrowly ellipsoid, 5.5–6 × 2.5–3 μm, holotype L = 5.8 µm, W = 2.8 µm, Q = (1.6–)1.8–2.2, colourless, smooth, slightly thick-walled, negative in Mz, acyanophilous, with minute apiculus.

Figure 3. 

Basidiomata of Xylodon spp. A X. exilis (TUB-FO 42565, holotype) B X. filicinus (MSK-F 12369, holotype) C X. follis (FR-0249814, holotype) D X. pseudolanatus (FP-150922, holotype) E X. pseudolanatus (HHB-6925, paratype) F X. vesiculosus (PDD-18112, isotype) G X. lanatus (CFMR HHB-8925, holotype). Scale bars: 1 mm.

The species is known from Taiwan and Nepal. It grows on dead wood of angiosperms, with a preference for small branches and twigs.

from Latin exilis – thin, fine, refers to the small and narrow aculei.

Figure 4. 

Micromorphology of Xylodon exilis (TUB-FO 42565, holotype): A, B vertical sections through basidioma C subicular hyphae D portion of hymenium and subhymenium E projecting aculeal hyphae in MzF projecting aculeal hyphae in 3% KOHG capitate cystidia H basidioles J basidia K basidiospores. Scale bars: 100 μm (A); 20 μm (B); 10 μm (C–J); 5 μm (K).

TAIWAN, Nantou Co., west from Sun-Moon Lake, near Hua Lien, on dead wood, leg. E. Langer, G. Langer, F. Oberwinkler, 26 Mar 1989 (TUB-FO 40734; dupl. in KAS); south from Sun-Moon Lake, near Hua Lien, on fallen angiosperm twig, leg. E. Langer, G. Langer, F. Oberwinkler, 9 Jul 1990 (TUB-FO 42450; dupl. in KAS and MSK); Taichung Co., Shinshe, on fallen angiosperm twig, leg. E. Yurchenko, 2 Apr 2011 (MSK-F 12912); ibid., on fallen liana stem, leg. E. Yurchenko, 2 Apr 2011 (MSK-F 12913); ibid., on fallen angiosperm twig, leg. E. Yurchenko, 5 Jun 2011 (MSK-F 12914); Taipei Co., Wulai, Neidong Recreation Area, on fallen angiosperm twig, leg. E. Yurchenko, 23 Jun 2011 (MSK-F 7381; dupl. in KAS and LE); Miaoli Co., Sanyi, on fallen angiosperm branch, leg. E. Yurchenko, 3 Jul 2011 (MSK-F 7431); ibid., on fallen angiosperm branch, leg. E. Yurchenko, 19 Jul 2011 (MSK-F 7430). NEPAL: Gandaki Prov., Kuldi, Anapurna Trek, leg. L. Ryvarden, 7 Nov 1979 (O-LR 18918/B, dupl. in KAS).

The species concept of X. lanatus is revised and restricted to specimens with a well-developed woolly subiculum. The distinctive characters of X. exilis are the minutely odontioid basidiomata with peg-like aculei composed of flexuous, encrusted, septate projecting hyphae that are constricted at the septa, embedded capitate cystidia and narrowly ellipsoid spores with slightly thickened walls. Earlier specimens of X. exilis from Taiwan (e.g. Langer 1994, p. 143 for illustration) and Nepal (Hjortstam and Ryvarden 1984) were originally identified as X. lanatus. Hyphae and spores of this species were also depicted by Yurchenko et al. (2013) under the name X. lanatus. These two species and other morphologically similar taxa are compared in the Discussion section below; a key is also presented.

TAIWAN, Nantou Co., Xitou (Shitou) Forest Recreation Area, W slope of Phoenix Mt. Range, 1470 m a.s.l., 23°40'N, 120°48'E, old-growth sparse broadleaf forest, on dead detached rachis of Cyathea sp., leg. E. Yurchenko, 31 Jul 2011 (field No. 38; MSK-F 12869; isotype in KAS).

Basidiomata effused, white, 2–4 cm in extent, farinaceous or pruinose, very loose or discontinuous, odontioid, 30–55 μm thick between aculei. Margin thinning out. Aculei conical or subcylindrical, 40–80 μm long, 15–45 μm diam., peg-like, of loose texture, 8–14/mm. Hyphal system monomitic, hyphae colourless, clamped at all septa. Subicular hyphae in a loose tissue, rarely branched, 2–3 μm diam., thin- or slightly thick-walled, loosely encrusted, under the subhymenium with inflations 5–6.5 μm wide. The largest crystals in subiculum 6–8 μm across, aggregated in clusters 15–18 μm diam. Subhymenial hyphae moderately branched, partly short-celled and slightly inflated, 2–3.5(–4) μm diam., lightly encrusted. Projecting hyphae in aculei richly encrusted, 20–45 × 5–7 μm in encrusted part, with clamped and simple septa, basally thick-walled, then becoming thin-walled, obtuse, sometimes subacute at apex. Cystidia in hymenium thin-walled, lightly encrusted, of three types: (1) subcylindrical, often slightly tapered to apex, numerous, 20–35 × 4.5–5.5 μm; (2) capitate, rare, 26–32 μm long, 3–5 μm wide at base, 2.5–3 μm wide at apex; (3) hyphoid to narrowly ventricose, about 30 × 4.5 μm. Basidioles ellipsoid, ovoid, clavate, 7.5–18 × 4.5–7.5 μm, more or less encrusted. Basidia utriform, (14–)16–20 × (3.5–)4.5–5.5 μm, thin-walled, smooth or sparsely encrusted, with four sterigmata 2–6.5 × 1–1.5 μm. Spores globose to subglobose, 4–5(–5.5) × (3.7–)4–4.5 μm, holotype L = 4.7 µm, W = 4.1 µm, Q = 1.1–1.2, thin-walled, often with one large oil-like globule, negative in Mz, weakly cyanophilous, with minute apiculus.

Figure 5. 

Micromorphology of Xylodon filicinus (MSK-F 12369, holotype): A vertical section through basidioma B subicular hyphae C inflations on hyphae in lower subhymenium D crystals from subiculum E portions of hymenium and subhymenium F bundle of encrusted projecting hyphae G separate projecting hyphae H subcylindrical cystidia J capitate cystidia K hyphoid cystidium L basidioles M basidia N basidiospores. Scale bars: 100 μm (A); 10 μm (B–M); 5 μm (N).

From the lower mountainous belt in Taiwan, on dead fern rachises.

from Latin filix ‒ fern, refers to the occurrence on dead fern rachises.

Additional specimen examined. TAIWAN, the same locality and the same substrate as holotype, leg. E. Yurchenko, 31 Jul 2011 (field No. 18; MSK-F 12870; dup. in KAS).

The distinctive features of this species are the pruinose, minutely odontioid basidiomata, fascicles of richly encrusted projecting hyphae in aculei and the three types of cystidia. Xylodon filicinus is morphologically similar to X. hyphodontinus, which differs in having projecting hyphae in the aculei that are straighter with more septa, a denser subhymenium composed of short-celled hyphae, short, ventricose cystidioles and spore walls that are slightly thickened at maturity (see Fig. 6).

Figure 6. 

Micromorphology of Xylodon hyphodontinus. LIP GG-MAR 15-127: A vertical section through basidioma B subicular hyphae C excerpt of tramal hyphae to hymenium and projecting hyphae D bundle of encrusted aculeal hyphae E encrustation on projecting hypha in water F encrustation on projecting hyphae in 3% KOHG naked projecting hyphal end H variously shaped hyphal ends J capitate cystidia K portion of hymenium and subhymenium L basidioles and cystidioles M basidiospores. LIP GG-MAR 12-238: N basidia. Scale bars: 100 μm (A); 10 μm (B–L, N); 5 μm (M).

REUNION, Forêt Notre Dame de la Paix, Sentier botanique, 21°15.8'S, 55°36.1'E, 1720 m a.s.l., on angiosperm wood, leg. J. Riebesehl, M. Schröder, M.M. Striegel, 12 Mar 2015 (FR-0249814; isotypes in KAS (as L1040) and MSK).

Basidiomata effused, cream-coloured, about 1–5 cm in extent, soft-membranaceous, continuous, finely aculeate, between aculei 50–200 μm thick; aculei narrowly conical or nearly cylindrical, 80–170 × 20–40(–60) μm, 10–12/mm, fragile, slightly fimbriate at apices, sterile. Margin abrupt. Hyphal system monomitic; hyphae clamped and simple septate, colourless, (1–)2–3.5 μm diam. Subiculum little differentiated, composed of thin- to slightly thick-walled hyphae. Hyphae in aculeal trama mostly parallel, thin- to thick-walled (walls up to 1 μm thick), projecting through aculeal apices and loosely encrusted with crystals about 1–3 μm long in KOH. Subhymenium thickening; subhymenial hyphae moderately branched, thin-walled, smooth. Capitate cystidia numerous, projecting and immersed, in subhymenium, hymenium and aculei, 17–30(–40) × 4.5–9 μm, with 1–2 adventitious septa in stalk, apical cap encased with resinous encrustation 6–12 μm wide, easily dissolving in KOH and Mz, unchanged in CBL. Hyphidial elements common in hymenium, 17–27 × 2.3–3.2 μm. Basidioles pyriform or ellipsoid, 17–28 × 8–12 μm, with granular contents, smooth or slightly encrusted. Basidia utriform or suburniform, thin-walled, smooth, 32–37 × 9–10 μm, with 4 sterigmata 4–6.5 × 1.3–2.3 μm. Spores globose to subglobose, colourless, with homogeneous or granular contents, smooth, inamyloid, indextrinoid, cyanophilous, thin-walled, (7.5–)8–9.5(–10) × 7–8.5 μm, holotype L = 8.6 μm, W = 7.6 μm, Q = 1.0–1.2, outer wall layer sometimes swelling in KOH and CBL, with rounded-triangular apiculus.

Figure 7. 

Micromorphology of Xylodon follis (FR-0249814, holotype): A vertical section through basidioma B subicular hyphae C vertical section through aculeus D lower and apical part of aculeal hyphae with adventitious septa E encrusted aculeal hyphae in water F partially dissolved crystals on aculeal hyphae in 3% KOHG capitate cystidia H portion of hymenium J vesicular basidiole K capitate encrusted cystidia and their detached resinous caps L basidia and basidiospores M basidiospores in 3% KOHN basidiospores in water O basidiospores in CBL. Scale bars: 100 μm (A); 10 μm (B–N).

The species is so far known from Réunion (Mascarene Archipelago) and inhabits dead wood.

from Latin follis ‒ bag or bubble, referring to shape of the spores, basidioles and capitate cystidia found in this species.

Additional specimen examined. REUNION, Forêt de Bébour, 1328 m asl., leg. E. Langer, G. Langer, E. Hennen, 20 Mar 1998 (KAS-GEL 4951; dupl. in MSK).

This taxon differs from other Xylodon species by its unusually large basidia, large globose basidiospores with walls that swell in KOH and CBL and numerous simple septa as well as clamps on the hyphae. The swelling of spore walls was observed in some spores; spores were unaffected in water mounts. The hymenium has a granular appearance visible under 100× magnification because of the resinous cap developed on the capitate cystidia. The resinous caps are observed only in CBL and are easily detaching in squash preparations. Intermediate forms in morphology of hyphidia to capitate cystidia and of capitate cystidia to pyriform basidioles were frequently observed.

BELIZE: Cayo District, Mountain Pine Ridge, on corticated hardwood branch, leg. K.K. Nakasone, 24 Nov 2001 (CFMR FP-150922; isotypes in KAS and MSK; ex-type culture CFMR FP-150922-sp; ex-type ITS sequence MH880220; ex-type 28S sequence MH884909).

Basidiomata effused, membranaceous, cream-coloured, 1–6 cm in extent, odontioid with conical aculei 50–120 μm long and 25–65 μm diam. at base, 8–14 aculei/mm. Subiculum between aculei very loose, minutely porulose, 100–150 μm thick. Margin pale cream-coloured, abrupt or diffuse, up to 2 μm wide. Hyphal system monomitic, hyphae clamped at all primary septa, colourless. Subicular hyphae little branched, mostly thick-walled, 2.5–4 μm diam., smooth or scarcely encrusted. Subhymenial hyphae richly branched, thin-walled, 2–3.5(–4.5) μm diam., smooth or slightly encrusted. Aculei consisting mostly of projecting hyphae. Projecting hyphae moderately flexuous, (3–)3.5–5 μm diam., slightly thick-walled, loosely encrusted, clamped at septa. Capitate cystidial elements found mostly in subhymenium and subiculum, scattered to frequent, terminal or lateral, smooth, thin- to thick-walled, aseptate or with adventitious septa, (8–)15–30 × (4.5–)5–6.5(–8.5) μm. Basidioles clavate to subcylindrical, sometimes slightly tapering to apex, 7–22 × 4–5 μm. Basidia cylindrical, sometimes slightly constricted, 16–30 × 4–4.3 μm, thin-walled, smooth, with four sterigmata about 2.5 × 0.2 μm. Spores narrowly ellipsoid to oblong, 5–6(–6.3) × (2.5–)3–3.5 μm, holotype L = 5.5 μm, W = 3.2 μm, Q = 1.7, thin- or slightly thick-walled, colourless, smooth, with minute apiculus, inamyloid, indextrinoid, weakly cyanophilous.

Figure 8. 

Micromorphology of Xylodon pseudolanatus. CFMR: FP-150922 (holotype): A vertical section through basidioma B subicular hyphae C vertical section through aculeus D detail of subicular hyphae and hymenium E, F projecting aculeal hyphae in 3% KOHG projecting aculeal hyphae in water H projecting aculeal hyphae in MzJ capitate cystidia in hymenium K basidioles L basidiospores. CFMR: HHB-6925: M capitate cystidia in subiculum N basidia. Scale bars: 100 μm (A); 10 μm (C–K, M, N); 5 μm (B, L).

South-eastern USA and Central America, on dead wood of angiosperms.

From Greek pseudo- – false, refers to its similarity to X. lanatus.

USA: Alabama, Escambia County, 3 miles east of Flomaton, on bark of Taxodium distichum (L.) Rich. (CFMR FP-103492), on bark of Quercus sp. (CFMR FP-103500), leg. A.S. Rhoades, 1 Nov 1952; Florida, Marion County, Okalawaha River, on dead inflorescence of Sabal palmetto (Walter) Lodd. ex Schult. & Schult. f., leg. H.H. Burdsall, Jr., 3 Aug 1972 (CFMR HHB-6925; dupl. in KAS and MSK); Louisiana, Baton Rouge, on Melia azedarach L., leg. C.J. Humphrey & C.W. Edgerton, 29 Aug 1909 (CFMR FP-5519).

The diagnostic features of this species are the minutely odontioid hymenophore, bundles of sparsely to moderately encrusted hyphae, projecting from aculeal apices, embedded capitate cystidia, cylindrical basidia and narrowly ellipsoid basidiospores. Some hymenial elements in this species are intermediate in morphology between basidioles, capitate cystidia and hyphal ends. Xylodon pseudolanatus can be distinguished from similar species in the key below (see Discussion).

This new combination is based on the phylogenetic analyses of the ITS and 28S sequences as well as morphological study of specimens, including the holotype of O. hyphodontina. Originally, the collections from Martinique and French Guyana were identified as O. ambigua, but the molecular data clearly show that these collections are embedded in Xylodon (Figs 1, 2). Although H. ambiguum is the oldest name for this taxon, it cannot be transferred to Xylodon because the name is preoccupied by X. ambiguus (Peck) Kuntze (= Veluticeps ambigua (Peck) Hjortstam & Telleria). Odontiopsis ambigua, P. sphaericosporus and O. hyphodontina were recognised as conspecific by Hjortstam (1987, 1991). Odontiopsis hyphodontina is the next oldest name and is chosen to represent this taxon. As O. hyphodontina is also the type of Odontiopsis Hjortstam & Ryvarden, Odontiopsis concomitantly becomes a synonym of Xylodon.

The newly generated ITS and 28S sequences of X. hyphodontinus hold comparable positions in a clade that includes three distinct lineages in both phylogenetic trees (Figs 1, 2). Specimens KAS-GEL9222 from Kenya and LIP GG-GUY13-044 from French Guyana each represent distinct lineages from the third lineage of LIP GG-MAR15-127 and LIP GG-MAR12-238 from Martinique. As species in Hyphodontia s.l. can be readily distinguished with ITS or 28S sequences, these three lineages should result in the recognition of three different species. However, we were not able to identify any definite morphological differences amongst the lineages in comparison with the holotype material from Tanzania. Cultures are not available for these specimens, thus intercompatibility tests are not possible. As a result, we decided to treat all three lineages as X. hyphodontinus at this time.

Odontia vesiculosa G. Cunn., Transactions and Proceedings of the Royal Society of New Zealand 86(1): 75 (1959) nom. inval.

NEW ZEALAND: Otago, Alton Valley, Tuatapere, leg. J.M. Dingley, Feb 1954 (PDD-18112 – holotype).

Cunningham (1959) described this new taxon as Odontia vesiculosa G. Cunn. Earlier, Odontia vesiculosa Burt was used for another species (Povah 1929). Consequently, Odontia vesiculosa G. Cunn. is an illegitimate name and a new name is required for this taxon (see Art. 6.11, 7.4 and 58.1 in Turland et al. 2018).

Below is a description based on the isotype of X. vesiculosus (CFMR).

Basidiomata effused, odontioid, membranaceous, with a densely odontioid, ochraceous hymenial surface. Margin mostly abrupt, some parts thinning out. Hymenophoral aculei cylindrical to conical, acute apically, 130–350 μm long, 60–150 μm diam. at base, 4 per mm. Subiculum 100–150 μm thick, minutely cracking. Hyphal system monomitic; hyphae clamped at all primary septa. Subicular and tramal hyphae thick-walled (wall up to 1.5 μm), 2.5–4 μm wide, often with narrow lumen, smooth, colourless, looking faint yellowish in mass due to refractive walls. Subhymenium well developed; hyphae richly branched, thin- to slightly thick-walled, yellowish in mass. Aculei bearing skeletal-like, naked or poorly encrusted, immersed hyphal ends and variously encrusted, thick-walled, projecting hyphae in bunches, 3.5–5 μm wide. Capitate elements common, as lateral branches on tramal or subhymenial hyphae, (25–)30–55 × 6.5–10.5 μm, thin- to thick-walled, aseptate or with 1–2 adventitious septa. Basidioles clavate, subcylindrical, utriform. Basidia utriform to subcylindrical and clavate, 15–22 × 4–5 μm, thin-walled, smooth, with four sterigmata ca. 2 × 0.5 μm. Spores ellipsoid to narrowly ellipsoid or short cylindric, 5.3–6.3(–7) × 3–4 μm, holotype L = 5.9, W = 3.4, Q = 1.8 (n = 22), with adaxial side flat to convex, smooth, thin-walled, colourless, with minute apiculus, inamyloid, indextrinoid, acyanophilous.

This species was considered conspecific with Xylodon lanatus from North America (Burdsall and Nakasone 1981, Wu 1990, Gorjón and Greslebin 2012), but we observed significant morphological differences. For example, in X. vesiculosus, the basidiomata have a denser, tough-membranaceous texture compared to the soft woolly basidiomata of X. lanatus. In addition, the aculei in X. vesiculosus are larger and the basidia are thin-walled in contrast to the smaller aculei and basally thick-walled basidia found in X. lanatus (compare Figs 9, 10). See Discussion for a key to X. lanatus, X. vesiculosus and allied taxa.

Figure 9. 

Micromorphology of Xylodon vesiculosus (PDD-18112, isotype): A vertical section through basidioma B subicular hyphae C excerpt of tramal hyphae to hymenium and skeletoid hyphae D bundle of projecting aculeal hyphae E smooth and variously encrusted aculeal hyphae F capitate cystidia G portion of hymenium and subhymenium H basidioles J basidia K basidiospores. Scale bars: 250 µm (A); 10 μm (B–J); 5 μm (K).

Figure 10. 

Micromorphology of Xylodon lanatus (CFMR: HHB-8925, holotype): A vertical section through basidiomata B subicular hyphae C vertical section through aculei and hymenium D projecting hyphae in 3% KOHE projecting hyphae in MzF capitate cystidia G basidioles H basidia J basidiospores. Scale bars: 500 μm (A); 20 μm (C); 10 μm (B, D–H); 5 μm (J).

Xylodon niemelaei (Sheng H.Wu) Hjortstam & Ryvarden, Synopsis Fungorum 26: 28 (2009)

≡ Hyphodontia niemelaei Sheng H. Wu, Acta Botanica Fennica 142:98 (1990).

Xylodon rhizomorphus (C.L.Zhao, B.K.Cui & Y.C.Dai) Riebesehl, Yurchenko & Langer, Mycological Progress 16(6): 649 (2017).

≡ Hyphodontia rhizomorpha C.L.Zhao, B.K.Cui & Y.C.Dai, Cryptogamie, Mycologie 35(1):92 (2014).

Molecular and morphological analyses demonstrate that the three taxa listed above are very similar. The 11 samples of X. niemelaei, 3 of X. rhizomorphus and 3 of X. reticulatus formed a strongly supported clade (99 BS, 1 PP) in the ITS phylogram (Fig. 1). In addition, three samples representing two of the species are found in a strongly supported clade (100 BS, 1 PP) in the 28S tree (Fig. 2), differing in only one position in the associated alignment.

Xylodon niemelaei was described and illustrated in detail by Wu (1990) and Langer (1994). It is characterised by a poroid hymenophore, embedded and hymenial capitate cystidia, small, subulate or fusoid hymenial cystidia and encrusted hyphal ends mainly developed at the pore edges but sometimes also in other areas. At the morphological level, the bladder-like embedded cystidia and hyphal encrustations appear identical in X. niemelaei (Langer 1994), X. rhizomorphus (Zhao et al. 2014) and X. reticulatus (Chen et al. 2017). Spore size and spore quotient overlap in these three species. Xylodon rhizomorphus occurs in south-western China, whereas X. reticulatus occurs in Taiwan and Japan. Xylodon niemelaei is reported also from these three countries and furthermore from Réunion, Africa and South America (Langer 1994), but the last two reports require morphological and molecular confirmation.

Xylodon niemelaei – REUNION: Forêt Mare-Longue, on dead stump of angiosperm wood, leg. J. Riebesehl, M. Schröder, M.M. Striegel, 12 Mar 2015 (FR-0249846, dupl. as L1087 in KAS); on lumber, leg. J. Riebesehl, M. Schröder, M.M. Striegel, 12 Mar 2015 (FR-0249174, dupl. as L1077 in KAS); on brown-rotten wood, leg. E. Langer, G. Langer, E. Hennen, 21 Mar 1998 (KAS-GEL 4998); Forêt Notre-Dame de la Paix, on dead wood of Monimia rotundifolia Thouars, leg. E. Langer, 11 Mar 2013 (FR-0219860, dupl. as L0002 in KAS); on dead angiosperm wood, leg. J. Riebesehl, M. Schröder, M.M. Striegel, 10 Mar 2015 (FR-0249811, dupl. as L1031 in KAS); on white-rotten wood, leg. E. Langer, G. Langer, E. Hennen, 19 Mar 1998 (KAS-GEL 4904); Le Petit Tampon, on dead wood, leg. J. Riebesehl, M. Schröder, M.M. Striegel, 9 Mar 2015 (FR-0249225, dupl. as L1007 in KAS); Piton Mont Vert, on dead wood, leg. J. Riebesehl, M. Schröder, M.M. Striegel, 18 Mar 2015 (FR-0249178, dupl. as L1172 in KAS); Plaine des Fougères, on dead wood, leg. E. Langer, 12 Sep 2013 (FR-0249744, dupl. as L0698 in KAS); Sentier de Takamaka, on white-rotten wood, leg. J. Riebesehl, M. Schröder, M.M. Striegel, 26 Mar 2015 (FR-0249289, dupl. as L1269 in KAS).

Based on both molecular data and morphology, we place the taxa X. bubalinus and X. chinensis in synonymy under X. spathulatus. In our phylogenetic analysis of ITS sequence data, the recently described X. bubalinus (4 collections) and X. chinensis (2 collections) from China form a well-supported clade with X. spathulatus (4 collections) from Europe (97 BS, 1 PP) that is sister to X. apacheriensis (Fig. 1). Within this clade are several subclades, with very low bootstrap support (<55), thus subspecies or varieties cannot be identified. The 28S rRNA gene analysis also supports conspecificity between X. chinensis and X. spathulatus (99 BS, 0.65 PP) (Fig. 2). Xylodon spathulatus has three main diagnostic features: prominent (1–2 mm tall) aculei of varied shape, numerous apically acute cystidia with 1–4 slight constrictions and capitate cystidia with a resinous cap. It is described and illustrated by Eriksson and Ryvarden (1976) and Langer (1994). Minor morphological variation amongst the three taxa was observed. For example, X. chinensis has ventricose cystidia, similar to those in X. spathulatus, but they are sometimes septate at the constrictions. Distinctly ventricose cystidia were not observed in X. bubalinus, which instead had hyphoid or subulate cystidioles (Wang and Chen 2017, Fig. 2f). Encrusted hyphal ends at apices of the aculei in X. bubalinus and X. chinensis are typical of those in X. spathulatus. Resinous caps enclosing capitate elements are often absent as in the case of X. bubalinus, X. chinensis, X. spathulatus KAS-GEL2690 (from Germany) and X. spathulatus MSK-F 12931 (from Russia). Spore shape and size are similar amongst the three taxa and the spore quotient 1.3–1.4(–1.5) overlaps (Eriksson and Ryvarden 1976, Wang and Chen 2017, Chen et al. 2017). A few spores in X. chinensis were up to 6 × 5 μm and may be due to better climatic conditions. The description of X. spathulatus is modified to include variable aculei from conical and subulate to distinctly spathuliform and the variable presence of cystidia with resinous caps, mucronate apices and a submoniliform type that are aseptate with more or less blunt apices. Thus X. spathulatus is a highly variable but distinctive species that is widely distributed from northern Europe (Eriksson and Ryvarden 1976) to southern China (Chen et al. 2017) and has a preference for old-growth forests (Dvořák et al. 2017). Reports of X. spathulatus from North and South America (Ginns and Lefebvre 1993, Hjortstam and Ryvarden 2007b) should be confirmed by molecular sequence data.

Xylodon spathulatus – CZECH REPUBLIC: Zofinsky National Park, on dead deciduous wood, leg. M.M. Striegel, 16 Sep 2015 (KAS-MMS 7224); GERMANY: Baden-Wurttemberg, Bad Waldsee, on dead wood of Picea abies (L.) H.Karst., leg. E. Langer, G. Langer, 15 Oct 1992 (KAS-GEL 2690); SWEDEN: Gästrikland, Island Torrö, on dead wood of Betula sp., leg. K.H. Larsson, 29 Sep 1988 (GB KHL 7085, dupl. in KAS); RUSSIA: Udmurtia, near Izhevsk town, on Sorbus aucuparia L., leg. V.I. Kapitonov, 7 Aug 2012 (MSK-F 12931).

We undertook a thorough morphological analysis of the specimen FR-0249200 (Réunion, Plaine des Fougères, on fallen angiosperm twig, leg. E. Langer, 12 Sep 2013), because it provided the first sequences of X. cystidiatus. We are confident that FR-0249200 is X. cystidiatus, although we detected minor differences from the descriptions in David and Rajchenberg (1992) and Langer (1994). Some of the differences we noticed include: (1) the encrusted cystidia in FR-0249200 are mostly thin-walled with finer crystals; (2) the spores in our specimen were slightly broader 5–6 × 3.5–4.3 µm (L = 5.4 µm, W = 3.9 µm, Q = 1.4) than in published records 5–6 × 3–4 µm. Photographs of the basidioma (Fig. 11) and drawings of the microscopic features (Fig. 12) of FR-0249200 are provided for future identifications.

Figure 11. 

Basidioma of Xylodon cystidiatus (FR-0249200). Scale bar: 1 cm.

Figure 12. 

Micromorphology of Xylodon cystidiatus (FR-0249200): A subicular hyphae B crystals from dissepiment in 3% KOHC crystals from dissepiment in MzD portion of hymenium and subhymenium E hyphal endings from dissepiment edges F encrusted cystidia in 3% KOHG encrusted cystidia in MzH smooth basidioles and cystidioles J encrusted basidiole (in Mz) K basidia L basidiospores. Scale bars: 10 μm (A–K); 5 μm (L).

ARGENTINA, Prov. Bonariae, Videla Dorna, on Salix babylonica L., May 1972, Deschamps et al. (BAFC 31920 – holotype).

ARGENTINA, Tierra del Fuego, Dpto. Ushuaia, Estancia El Valdéz, on Nothofagus pumilio (Poepp. & Endl.) Krasser, 4–5 Mar 1996, A. Greslebin (BAFC 50036 – holotype).

ARGENTINA, Tierra del Fuego, Parque Nacional Tierra del Fuego, Río Pipo, on Nothofagus sp., 7 Nov 1998, A. Greslebin (BAFC 50037 – holotype).

TAIWAN, Taipei, Kungliao, on rotten angiosperm branch, 25 Nov 1990, Y.F. Lin (TNM Lin 90202 – holotype).

NEW ZEALAND, Auckland, Hauhangaroa Range, Taupo, on decayed decorticated wood of Dacrydium cupessinum Sol., Mar 1953, J.M. Dingley (PDD 12513 – holotype).