Abstract

INTRODUCTION

The Atractiellomycetes is a class among the rust fungi (Pucciniomycotina), with about 50 species (Aime et al. 2014, Toome-Heller 2016). The presence of saccate probasidia and unique ultrastructural elements (atractosomes), as well as absence of a yeast stage are the main diagnostic features of this group. The Atractiellomycetes encompasses representatives with pycnidioid (Basidiopycnis, Basidiopycnides), gasteroid (Atractiella, Phleogena) and corticioid (Helicogloea, Saccoblastia) fructifications, as well as a number of asexual taxa (Hobsonia, Infundibura, Leucogloea, Proceropycnis) (Bauer et al. 2006, Oberwinkler et al. 2006, Aime et al. 2014, 2018). For now, most of them are considered saprotrophic, inhabiting plant remnants or beetle galleries in decaying wood (Bauer et al. 2006, Oberwinkler et al. 2006), with a few taxa detected in orchid mycorrhiza (Kottke et al. 2010) or associated with tree roots (Bonito et al. 2017). However, the genus- and species-level taxonomy of the class remains extremely poorly resolved, and DNA data available in public repositories are fragmentary. In this paper, we revise the taxonomy of the Atractiellomycetes species producing effused, crust-like (corticioid) basidiocarps currently addressed to the genus Helicogloea s. lat., using morphological and DNA methods.

The genus Helicogloea was described by Patouillard (in Patouillard & Lagerheim 1892) with a single species, H. lagerheimii, based on Lagerheim’s collection from Ecuador. In the protologue, Patouillard compared the new genus with Platygloea and Helicobasidium; however, he overlooked saccate probasidia characteristic for this species and the genus as a whole. This seems to have been a reason to abandon Helicogloea in favour of Saccoblastia, another genus described three years later from Brazil (Möller 1895). Möller introduced his genus for two new species, S. ovispora and S. sphaerospora, with excellent descriptions and illustrations of basidial morphology. He emphasized the importance of saccate probasidia as the main generic feature. Four new species were added to Saccoblastia by Bourdot & Galzin (1909), Coker (1928) and Linder (1929). Bourdot & Galzin (1928) assumed that Möller’s generic description refers to species with floccose basidiocarps, and therefore separated Saccoblastia sebacea, having gelatinous fructifications, to a newly introduced section Saccogloea.

Baker’s study (1936) was a crucial moment in the taxonomic history of the genus. She conducted cytological investigations of all species then addressed to Saccoblastia and showed that they all are microscopically similar. Baker studied the original specimen of H. lagerheimii, the type species of Helicogloea, and proved that it possesses saccate probasidia. Therefore, the genus name Saccoblastia was replaced by the older epithet Helicogloea. Donk (1966) raised objections to such a wide genus concept and proposed to limit Helicogloea to gelatinous species only (i.e. section Saccogloea) while species with floccose, non-hygroscopic basidiocarps were retained in Saccoblastia. Donk’s arguments were accepted by Jülich (1976), Wojewoda (1982) and Kisimova-Horovitz et al. (2000). Phylogenetic studies by Aime et al. (2006) and Bauer et al. (2006) demonstrated that Helicogloea and Saccoblastia sensu Donk are not congeneric and belong to different lineages within Atractiellomycetes. In the latter study, Platygloea vestita was detected as closely related to Saccoblastia. Finally, Aime et al. (2018) introduced two new monotypic genera, Neogloea (typified with Helicogloa variabilis) and Bourdotigloea (typified with P. vestita).

Here we reinstate Helicogloea s. str. with 25 accepted species closely related to the type species, H. lagerheimii, and describe 11 of them as new. Identity of the generic type of Saccoblastia, S. ovispora, is clarified, and this species is transferred to Helicogloea s. str. As a consequence, a new genus, Saccosoma, is introduced to encompass Saccoblastia sensu Donk, i.e. species with arid basidiocarps. Identity of Bourdotigloea vestita and eight related species is discussed, and six of them are described as new to science.

MATERIAL AND METHODS

RESULTS

Phylogeny

The phylogenetic analyses resulted in two trees for nrITS+nrLSU and nrITS datasets (Fig. 1, ​,2).2). The phylogeny derived from the nrITS+nrLSU dataset (1 675 characters, including gaps) (Fig. 1) shows that members of Helicogloea s. lato (as advocated by Baker 1936) are spread among three lineages within the class. In general, these phylogenetic reconstructions follow the results of earlier studies (in particular, Aime et al. 2006, 2018, Bauer et al. 2006) demonstrating that Helicogloea is polyphyletic and Platygloea vestita (= Helicogloea vestita) belongs to the Atractiellomycetes. Most species of Helicogloea s. lat. included in the analyses form a strongly supported clade with a reference specimen of H. lagerheimii, the generic type (Fig. 1, pp = 0.99, bs = 75 %), thus constituting Helicogloea s. str. The single representatives of Leucogloea (L. compressa) and Neogloea (N. variabilis) belong to Helicogloea, too, and therefore we consider these generic names taxonomic synonyms. The second clade is represented by Helicogloea farinacea and its closest relatives (Fig. 1, pp = 1, bs = 100 %). Traditionally, this group was associated with the generic name Saccoblastia. However, we argue below that the latter generic epithet is not applicable to the H. farinacea complex, and a new genus Saccosoma is described to encompass it. Helicogloea vestita and its siblings form a third lineage in the phylogeny (Fig. 1, pp = 1, bs = 100 %) only distantly related to both Helicogloea s. str. and Saccosoma. As a consequence, they are separated into the recently described genus, Bourdotigloea.

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Fig. 1.

Combined nrITS + nrLSU topology from Bayesian analysis showing major lineages of the Atractiellomycetes. Collection numbers are given for all specimens. Support values (Bayesian posterior probability / Maximum likelihood Bootstrap values) are given above the branches. Scale bar shows expected changes per site.

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Fig. 2.

Bayesian phylogram for the nrITS dataset. Collection numbers are given for newly sequenced specimens and accession numbers for additional sequences retrieved from GenBank. Support values (Bayesian posterior probability / Maximum likelihood Bootstrap values) are given above the branches. Scale bar shows expected changes per site.

ITS dataset for the corticioid Atractiellomycetes (972 characters, including gaps) included sequences from 54 fungal samples (Fig. 2). The three major clades (Saccosoma, Bourdotigloea, Helicogloea) are highly supported and the internal topology of these clades is well resolved and support the distinction of 26 accepted species.

DNA data obtained in the present study correspond well to the morphological evidence. All species of Helicogloea s. str. and all but one of Bourdotigloea spp. possess gelatinous, semitranslucent basidiocarps that turn to a vernicose crust after drying, while Saccosoma spp. have sturdier, arid fructifications, unchanged in dry condition (Fig. 3). In microscopic terms, presence of clamps and shape of basidia are of crucial value for recognizing crust-like genera of the Atractiellomycetes. Both Helicogloea and Bourdotigloea spp. are totally devoid of clamps; basidia are variably curved, with a terminal cell bearing a laterally arranged sterigma (Fig. 4, ​,5).5). However, almost all Bourdotigloea species treated below have differentiated cystidia and distinctly coloured (brownish), very thick-walled subicular hyphae, whereas Helicogloea lacks cystidia and hyphal colouration (subicular hyphae are in general less differentiated from subhymenial ones). In contrast, all hyphae in Saccosoma spp. are clamped, basidia are straight (not curved) and their terminal cell bears an apical sterigma (Fig. 6). Sporodochial asexual morphs (Leucogloea, Infundibura) have been so far detected in Helicogloea s. str. only (see Kirschner 2004 for a detailed discussion).

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Fig. 3.

Fructifications of the Atractiellomycetes. A. Helicogloea crassitexta (holotype). B. H. eburnea (holotype). C. H. microsaccata (holotype). D. H. septifera (Spirin 11043). E. H. ovispora (lectotype). F. Bourdotigloea cerea (holotype). G. B. multifurcata (holotype). H. Saccosoma farinaceum (Miettinen 17547). Scale bar = 10 mm.

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Fig. 4.

Bourdotigloea lanea (holotype). A. Basidia, subicular and subhymenial hyphae, hymenial cells. B. Cystidia. C. Basidiospores. Scale bar = 10 μm.

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Fig. 5.

Helicogloea subardosiaca (Pennanen 3668). Subicular hyphae, hymenium, basidiospores. Scale bar = 10 μm.

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Fig. 6.

Saccosoma farinaceum (neotype). Hyphae and basidia. Scale bar = 10 μm.

Even when Bourdotigloea and Saccosoma are separated from Helicogloea, the latter genus shows rather high morphological diversity and divergency of nrITS and LSU sequences. Therefore, we do not exclude that further splitting may become necessary. Fulfilling this task, however, implies much wider sampling of the Atractiellomycetes, especially of asexual taxa, and use of additional genetic markers.

TAXONOMY

Bourdotigloea Aime, Mycologia 110: 144. 2018.

Basidiocarps resupinate, very thin, at first pruinose, then waxy to ceraceous. Hyphae clampless, in many cases rather short-celled and variably inflated. Basal hyphae coloured (brownish), in a few species hyaline, slightly to very thick-walled, 7–19 μm diam, strongly cyanophilous. Subhymenial hyphae hyaline, thin- to slightly thick-walled, often easily collapsing, 3.5–8 μm diam, slightly to moderately cyanophilous. Basidia four-celled, tubular-clavate, straight or somewhat curved, with sharp-pointed, thick sterigmata; probasidia saccate. Cystidia as a rule present, tubular, more or less straight to somewhat sinuous or moniliform, decumbent but often with ascending apical part. Basidiospores cylindrical, fusiform or sigmoid, 12–36 × 4–10 μm, germinating by repetition.

On decayed wood, dead fructifications of other basidiomycetes and plant debris.

Type species: Bourdotigloea vestita (Bourdot & Galzin) Aime.

Notes: This genus is re-introduced here to embrace P. vestita and its closest relatives. The species of Bourdotigloea are morphologically most similar to Helicogloea spp. The latter ones differ in having narrower and not inflated, colourless hyphae, and their basidia bear more slender sterigmata. No differentiated cystidia are detected among Helicogloea species. Moreover, basidiospores of all known Helicogloea spp. (except H. angustispora) are ellipsoid/subglobose or broadly cylindrical, not fusiform.

Nine species are accepted below as belonging to Bourdotigloea. However, actual species diversity in this genus seems to be much higher. According to the protologue (Olive 1953) and later redescription by Bandoni (1956), Platygloea subvestita may also belong to Bourdotigloea, although a presence of gloeocystidia looks confusing. Olive’s description of P. vestita specimens from the southern Appalachians (Olive 1953) does not fit to any species we currently accept. Moreover, two collections from Iowa labelled by G.W. Martin as H. lagerheimii, certainly represent one more species in this complex (treated as Bourdotigloea sp. under Specimens examined). However, we decided to limit our study to existing species names or newly collected and sequenced material. Therefore, we leave these problems until we find new collections of the aforementioned problematic taxa.

Bourdotigloea cerea Spirin & V. Malysheva, sp. nov. MycoBank MB825588. Figs 3, ​,77.

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Fig. 7.

Bourdotigloea cerea (holotype). Cystidia and basidiospores. Scale bar = 10 μm.

Etymology: Cereus (Lat., adj.) – waxy.

Holotype: Norway, Oppland, Sel, Sagåa Nat. Res., Picea abies, 13 Sep. 2016, Spirin 11057 (O).

Basidiocarps resupinate, 0.03–0.05 mm thick, first pruinose, then semitranslucent, greyish, waxy. Basal hyphae hyaline, slightly to distinctly thick-walled, easily collapsing, (7.2–)8.0–11.0(–11.2) μm diam (n = 20/1). Subhymenial hyphae thin-walled, easily collapsing, (3.3–)3.7–7.0(–7.8) μm diam (n = 20/1). Basidia tubular-clavate, straight or somewhat curved, 53–63 × (5.4–) 5.6–7.0(–8.1) μm (n = 20/1), with sharp-pointed sterigmata up to 8 × 4 μm; probasidia saccate, 26–33 × 10–12.5 μm. Cystidia rare, tubular, more or less straight to somewhat sinuous, 44–121 × 5–6 μm. Basidiospores narrowly fusiform, some more or less sigmoid, (18.0–)18.6–32.8(–36.2) × (4.0–)4.2–7.0(–7.2) μm (n = 32/1), L = 23.53, W = 5.39, Q’ = (3.1–)3.4–5.7(–6.1), Q = 4.41.

Distribution and ecology: Europe (Norway); fallen, decorticated but hard branch of Picea abies.

Notes: Bourdotigloea cerea differs from other species of the genus in having narrow basidiospores and non-constricted cystidia.

Bourdotigloea concisa Spirin & Trichies, sp. nov. MycoBank MB825589. Fig. 8.

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Fig. 8.

Bourdotigloea concisa (holotype): cystidia and basidiospores. Scale bar = 10 μm.

Etymology: Concisus (Lat., adj.) – concise, brief.

Holotype: France, Moselle, Fontoy, dead Stereum rugosum on Alnus glutinosa, 27 Feb. 2011, Trichies 11015 (H, isotype – GT).

Basidiocarps resupinate, 0.03–0.05 mm thick, first pruinose, greyish, then pale ochraceous, semitranslucent to opaque, rather tough. Basal hyphae hyaline to brownish, slightly to distinctly thick-walled, sturdy, (6.7–)7.7–11.9(–12.0) μm diam (n = 30/2). Subhymenial hyphae thin- to slightly thick-walled, easily collapsing, some irregularly inflated, (4.1–)4.3–7.3(–7.0) μm diam (n = 40/2). Basidia tubular-clavate, straight or somewhat curved, 61–87 × (6.2–)6.4–8.2(–8.8) μm (n = 20/2), with sharp-pointed sterigmata up to 11 × 7 μm; probasidia saccate, 25–66 × 11–13 μm. Cystidia abundant, distinctly moniliform, 80–121 × 7.5–12.5 μm. Basidiospores mostly fusiform, (14.1–)15.2–27.2(–27.8) × (5.0–)5.7–8.2(–9.2) μm (n = 90/3), L = 18.67–20.42, W = 6.39–6.86, Q’ = (2.1–)2.2–4.2(–4.6), Q = 2.74–3.15.

Distribution and ecology: Europe (France, UK); fallen branches and logs of deciduous trees (Alnus, Fagus, Salix), occasionally also dead basidiocarps of corticioid fungi (Hymenochaete, Stereum).

Notes: Bourdotigloea concisa is most similar to B. grisea, B. dura and B. vestita. It differs from the two latter species in having distinctly moniliform (bearing multiple, rather regular and pronounced constrictions) cystidia. Moreover, basidiospores of B. vestita are wider. Differences between B. concisa and B. grisea are more subtle: the species can mainly be distinguished due to differently looking subicular hyphae, as well as maximal length of basidia and basidiospores.

Bourdotigloea dura Spirin & V. Malysheva, sp. nov. MycoBank MB825590. Fig. 9.

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Fig. 9.

Bourdotigloea dura (holotype). Cystidia and basidiospores. Scale bar = 10 μm.

Etymology: Durus (Lat., adj.) – hard, tough.

Holotype: Norway, Oppland: Nord-Fron, Liadalane Nat. Res., Betula pubescens, 12 Sep. 2016, Spirin 11054 (O).

Basidiocarps resupinate, 0.03–0.05 mm thick, first pruinose, greyish, then strongly gelatinized, tough, almost invisible in dry condition. Basal hyphae hyaline to brownish, slightly to distinctly thick-walled, sturdy, (7.6–)7.8–13.8(–17.0) μm diam (n = 30/2). Subhymenial hyphae thin- to slightly thick-walled, some irregularly inflated, (4.0–)4.2–8.0(–8.2) μm diam (n = 30/2). Basidia tubular-clavate, straight or somewhat curved, 52.5–80 × (6.1–)6.2–7.6(–7.7) μm (n = 25/2), with sharp-pointed sterigmata up to 6 × 5 μm; probasidia saccate, 23.5–39 × 7–12 μm. Cystidia abundant, tubular-clavate, often sinuose and with several slight constrictions, 80–121 × 7.5–12.5 μm. Basidiospores cylindrical to fusiform, (15.1–)16.7–27.7(–32.3) × (5.6–)5.7–7.4(–10.4) μm (n = 60/2), L = 20.90–21.69, W = 6.16–6.55, Q’ = (2.3–)2.8–4.4(–4.9), Q = 3.34–3.39.

Distribution and ecology: Europe (Norway); rather rotten decorticated logs of deciduous trees (Alnus, Betula).

Notes: Morphologically, Bourdotigloea dura is most similar to B. concisa but it differs in having only slightly constricted cystidia. Bourdotigloea vestita with similarly looking cystidia possesses wider basidiospores.

Bourdotigloea grisea Spirin & V. Malysheva, sp. nov. MycoBank MB825591. Fig. 10.

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Fig. 10.

Bourdotigloea grisea (holotype). Hyphae, hymenial structures and basidiospores. Scale bar = 10 μm.

Etymology: Griseus (Lat., adj.) – grey.

Holotype: Norway, Møre og Romsdal, Nesset, Eikesdalen, Alnus incana, 28 Sep. 2017, Spirin 11629 (O).

Basidiocarps resupinate, 0.03–0.05 mm thick, pruinose, greyish. Basal hyphae hyaline to brownish, slightly thick-walled, sparse, (6.2–)6.3–10.7(–10.8) μm diam (n = 20/2). Subhymenial hyphae thin- or only slightly thick-walled, easily collapsing, some irregularly inflated, (3.8–)4.2–7.7(–7.8) μm diam (n = 20/2). Basidia tubular-clavate, straight or somewhat curved, 61.5–108 × (5.8–)6.0–8.1(–8.2) μm (n = 48/2), with sharp-pointed sterigmata up to 11 × 3.5 μm; probasidia saccate, 28–48 × 10–14 μm. Cystidia abundant, distinctly moniliform, 80–163 × 8–10.5 μm. Basidiospores fusiform, the longest ones sigmoid, (17.2–) 17.8–34.8(–36.6) × (4.7–)5.0–8.2 μm (n = 60/2), L = 21.73–23.93, W = 5.98–6.99, Q’ = (2.2–)2.4–4.8(–5.7), Q = 3.13–3.98.

Distribution and ecology: Europe (Norway); fallen branches and logs of deciduous trees (Alnus incana).

Notes: Bourdotigloea grisea differs from other European species of the genus in having rather poorly differentiated subicular hyphae which are only slightly wider than subhymenial ones. The species is detected twice in an isolated mountain valley in Norway, occurring on alder wood remnants in inundated habitats.

Bourdotigloea lanea Spirin & V. Malysheva, sp. nov. MycoBank MB825592. Fig. 4.

Etymology: Laneus (Lat., adj.) – soft.

Holotype: Norway, Østfold, Aremark, Picea abies, 25 Oct. 2011, J. Nordén 9962 (O).

Basidiocarps resupinate, 0.03–0.06 mm thick, first pruinose, then compact floccose, greyish. Basal hyphae hyaline to brownish, slightly to distinctly thick-walled, easily collapsing, (7.0–)7.4–14.0(–14.2) μm diam (n = 20/1). Subhymenial hyphae thin- to slightly thick-walled, easily collapsing, (4.0–)4.1–6.0(–6.2) μm diam (n = 20/1). Basidia tubular-clavate, straight or somewhat curved, 69–88.5 × (6.0–)6.2–8.2(–8.3) μm (n = 20/1), with sharp-pointed sterigmata up to 11 × 4.5 μm; probasidia saccate, 24–37 × 8–11.5 μm. Cystidia rare, tubular, more or less straight to somewhat sinuous, rarely with several inconspicuous constrictions, 34–86 × 6.5–10 μm. Basidiospores fusiform, some cylindrical, very rarely narrowly ellipsoid, (11.3–)12.4–19.2(–19.4) × (5.0–)5.1–9.1(–10.2) μm (n = 30/1), L = 15.98, W = 7.22, Q’ = (1.6–)1.8–3.1(–3.5), Q = 2.26.

Distribution and ecology: Europe (Norway); fallen, decorticated log of Picea abies.

Notes: Basidiocarps of Bourdotigloea lanea are floccose, while they are gelatinized and of more compact structure in other species of the genus. However, anatomical features and DNA data indicate it is a member of Bourdotigloea. Microscopically, B. lanea is most similar to the North American B. longispora. The latter species has shorter cystidia, smaller basidia and narrower basidiospores.

Bourdotigloea longispora (G.E. Baker) Spirin, comb. nov. MycoBank MB825593. Fig. 11.

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Fig. 11.

Bourdotigloea longispora (lectotype). Cystidia, basidia and basidiospores. Scale bar = 10 μm.

Basionym: Helicogloea longispora G.E. Baker, Mycologia 38: 634. 1946. Lectotype. USA, Oregon, Lane Co., Lorane, Pseudotsuga menziesii, 22 Oct. 1938 Doty 522 (NY00834142, selected here) (MycoBank MBT 383604).

Basidiocarps resupinate, 0.02–0.04 mm thick, semitranslucent or not macroscopically visible, developing as hyphae with basidia inside or under basidiocarps of corticioid fungi. Basal hyphae hyaline to pale brownish, slightly to distinctly thick-walled, sturdy, sparse, 6–12 μm diam. Subhymenial hyphae thin- to slightly thick-walled, (3.0–)3.7–7.3(–8.3) μm diam (n = 20/1). Basidia tubular-clavate, straight or somewhat curved, 41–63 × (5.2–)5.8–7.0(–7.6) μm (n = 20/1), with sharp-pointed sterigmata up to 6 × 3 μm; probasidia saccate, 35–50 × 8–11 μm. Cystidia infrequent, tubular, more or less straight to somewhat sinuous, 34–52 × 6–8 μm. Basidiospores cylindrical-fusiform, some more or less sigmoid, (12.0–)12.8–18.3(–19.1) × (4.9–)5.1–7.3(–7.6) μm (n = 30/1), L = 15.00, W = 5.73, Q’ = (1.7–)2.1–3.1(–3.2), Q = 2.64.

Distribution and ecology: Europe (Russia), North America (USA – North Carolina, Oregon); rotten logs of Pseudotsuga menziesii and Pinus spp.

Notes: Rather wide and clearly thick-walled, occasionally coloured basal hyphae, inflated subhymenial hyphae, cystidia and fusiform basidiospores of H. longispora support its transfer to Bourdotigloea. Evidently, the species has been overlooked due to tiny basidiocarps often hidden among or under fructifications of other fungi. One recent collection from North-West Russia (Spirin 12192) agrees with the North American material, except slightly shorter basidiospores, (10.7–)10.8–15.6(–17.7) × (5.0–) 5.3–7.4(–7.6) μm (n = 30/1), L = 13.42, W = 6.22, Q’ = (1.7–)1.8–2.6(–3.1), Q = 2.17. For now, we treat it as B. longispora.

Bourdotigloea multifurcata Spirin & V. Malysheva, sp. nov. MycoBank MB825594. Figs 3, ​,1212.

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Fig. 12.

Bourdotigloea multifurcata (holotype). Hyphae, hymenial structures and basidiospores. Scale bar = 10 μm.

Etymology: Multifurcatus (Lat., adj.) – intensively branched in a fork-like manner.

Holotype: Norway, Aust-Agder, Grimstad, Sæveli Nat. Res., Quercus robur (fallen branch) and dead Fuscoporia ferrea, 2 Nov. 2017, Spirin 11785 (O).

Basidiocarps resupinate, 0.03–0.05 mm thick, pruinose, greyish. Basal hyphae hyaline to brownish, slightly to distinctly thick-walled, (9.1–)9.2–18.8(–19.3) μm diam (n = 20/1). Subhymenial hyphae thin- to slightly thick-walled, often distinctly inflated, (4.2–)4.3–7.9(–8.1) μm diam (n = 20/1). Basidia tubular-clavate, straight to clearly twisted, 61.5–85 × (6.2–)6.3–8.3(–9.0) μm (n = 20/1), with sharp-pointed, often bi- or trifurcate and randomly arranged sterigmata up to 15 × 5 μm; probasidia saccate, often twisted, 28–48 × 10.5–16 μm. Cystidia abundant, distinctly moniliform, 60–153 × 6–12.5 μm. Basidiospores cylindrical to broadly fusiform, (15.3–)16.2–32.2(–35.6) × (5.1–)5.2–9.6(–9.7) μm (n = 30/1), L = 22.64, W = 6.51, Q’ = (2.6–)2.7–4.5(–4.7), Q = 3.50, often germinating by bi-trifurcate sterigmata.

Distribution and ecology: Europe (Norway); fallen branches of deciduous trees (Quercus) and dead basidiocarps of polypores (Phellinus s.l.).

Notes: Moniliform cystidia and rather wide basidiospores place B. multifurcata in the difficult B. vestita complex, alongside B. concisa, B. dura, B. grisea and B. vestita s. str. The most striking feature of B. multifurcata is the highly irregular shape and number of sterigmata: they are usually furcate, and up to three separate sterigmata may occur at one basidial cell. This might explain a high variability of basidiospores, also showing multiple germination by fork-like sterigmata.

Bourdotigloea sebacinoidea (L.S. Olive) Spirin, comb. nov. MycoBank MB825595. Fig. 13.

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Fig. 13.

Bourdotigloea sebacinoidea (lectotype). Hyphae and basidiospores. Scale bar = 10 μm.

Basionym: Helicogloea sebacinoidea L.S. Olive, Mycologia 40: 588. 1948. Lectotype: USA, Louisiana, Caddo Parish, Shreveport, dead Exidia glandulosa on branch of Quercus sp., 4 Jul. 1947, Olive (NY00834143, selected here) (MycoBank MBT383605).

Synonym: Helicogloea parasitica L.S. Olive, Mycologia 43: 677. 1951 (nomen superfluum).

Basidiocarps resupinate, hypochnoid, almost invisible by a naked eye. Basal hyphae hyaline to pale brownish, slightly to distinctly thick-walled, easily collapsing, (6.2–)7.0–12.3(–12.7) μm diam (n = 20/1). Subhymenial hyphae thin- to slightly thick-walled, (4.0–)4.2–6.9(–7.2) μm diam (n = 20/1). Basidia tubular-clavate, straight or somewhat curved, ca. 94 × 6–8 μm, with sharp-pointed sterigmata up to 6 × 2 μm; probasidia saccate, 30–46 × 9–11 μm. Cystidia not detected. Basidiospores cylindrical-fusiform, some slightly or moderately curved, 13–23.2 × 4.8–7.3 μm (n = 14/1), L = 17.54, W = 5.86, Q’ = (2.0–)2.1–3.9(–4.3), Q = 3.03.

Distribution and ecology: North America (USA – Louisiana); corticated oak branch and dead Exidia glandulosa.

Notes: The original material of H. sebacinoidea is very scanty although hyphal shape and width, as well as basidia and basidiospores agree with the current generic concept of Bourdotigloea. Hence a new combination. However, cystidia have not been detected in B. sebacinoidea, and it is still uncertain if they are absent or just not properly developed in the single existing specimen. The species deserves further study.

Bourdotigloea vestita (Bourdot & Galzin) Aime, Mycologia 110: 144. 2018. Fig. 14.

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Fig. 14.

Bourdotigloea vestita (Trichies 09017). Cystidia and basidiospores. Scale bar = 10 μm.

Basionym: Platygloea vestita Bourdot & Galzin, Bull. Soc. Mycol. France 39: 261, 1924. Lectotype: France, Aveyron, Bouissou, Genista tinctoria, 24 Dec. 1916, Galzin 21380 (herb. Bourdot 19240) (PC 0706699, selected here) (MycoBank MBT383606).

Basidiocarps resupinate, 0.03–0.06 mm thick, first pruinose, greyish, then pale ochraceous, opaque, ceraceous. Basal hyphae hyaline to brownish, slightly to distinctly thick-walled, sturdy, (6.7–)7.1–11.8(–13.0) μm diam (n = 50/3). Subhymenial hyphae thin- to slightly thick-walled, (3.4–)3.7–7.7(–7.8) μm diam (n = 50/3). Basidia tubular-clavate, straight or somewhat curved, 61–81 × (6.8–)7.0–10.3(–11.6) μm (n = 20/1), with sharp-pointed sterigmata up to 21 × 5.5 μm; probasidia saccate, 25–48 × 9–16 μm. Cystidia rather numerous, tubular, irregularly constricted, 45–109 × 6.5–12 μm. Basidiospores fusiform, rarely long cylindrical and then moderately curved, (14.6–)15.2–30.4(–31.3) × (6.0–)6.1–9.8(–10.3) μm (n = 85/3), L = 21.96–22.55, W = 7.29–7.89, Q’ = (2.1–)2.2–3.9(–4.1), Q = 2.95–3.05.

Distribution and ecology: Europe (France); fallen branches and rotten wood of angiosperms (Alnus, Erica, Genista) and possibly also gymnosperms.

Notes: Bourdot & Galzin (1924) introduced P. vestita based on numerous collections from France and England. Our study shows that they belong to two different species. Therefore, a lectotype is designated here to settle the species identity of P. vestita. Another species present among the authentic material is described above as B. concisa. From other species of the genus, B. vestita differs by wider basidia and basidiospores. Cystidia of B. vestita possess occasional constrictions although they are much less regular and pronounced than in B. concisa, B. grisea and B. multifurcata.

Helicogloea Pat., Bull. Soc. Mycol. France 8: 121. 1892.

Synonyms: Saccoblastia Möller, Botanische Mittheilungen aus den Tropen 8: 16. 1895. Lectotype: Saccoblastia ovispora Möller (selected by Clements & Shear 1931).

Infundibura Nag Raj & Kendrick, Canad. J. Bot. 59: 544. 1981. Type species: Infundibura adhaerens Nag Raj & Kendrick (asexual).

Leucogloea R. Kirschner in Agerer et al., Frontiers in Basidiomycete Mycology: 177. 2004. Type species: Dendrodochium compressum Ellis & Everh. (asexual).

Neogloea Aime, Mycologia 110: 143. 2018. Type species: Helicogloea variabilis K. Wells.

Basidiocarps resupinate, normally thin, rarely addpressed-pulvinate, semitranslucent, waxy to gelatinous. Hyphae clampless, short- or long-celled, usually not inflated, slightly to moderately cyanophilous. Basal hyphae hyaline, slightly to distinctly thick-walled, 2–7 μm diam. Subhymenial hyphae thin- to slightly thick-walled, 2–5 μm diam, slightly cyanophilous. Basidia four-celled, tubular-clavate, straight or curved / twisted, with sharp-pointed, slender sterigmata; probasidia clavate or saccate. Cystidia absent. Basidiospores cylindrical to broadly ellipsoid / subglobose (except H. angustispora with narrowly fusiform basidiospores), 7–30 × 4–15 μm, germinating by repetition.

On decayed wood of deciduous trees and conifers, rarely on other plant remnants (fallen cones or dead palm stems), as well as in or under other corticioid fungi.

Type species: Helicogloea lagerheimii Pat. (selected by Clements & Shear 1931).

Notes: As defined here, Helicogloea embraces 25 species with waxy or gelatinous, semitranslucent basidiocarps and clampless hyphae. Basal hyphae of almost all Helicogloea species treated here are wider than subhymenial ones, and they possess thicker walls. They are, however, colourless, and this feature, as well as absence of differentiated cystidia, differtiates Helicogloea from Bourdotigloea. Saccosoma species have floccose or dense, arid (non-gelatinized) basidiocarps and clamped hyphae, as well as straight (not curved) basidia.

Four species earlier ascribed to Helicogloea have been excluded from the present treatment. According to Baker (1936), H. graminicola (Bres.) G.E. Baker is similar to other species of Helicogloea s. str. but it has clamped hyphae. Moreover, its occurrence on herbaceous stems is untypical for the genus because all species so far known inhabit wood remnants. Helicogloea musaispora Chee J. Chen & Oberw. (2000) from Taiwan have fusiform basidiospores and swollen, rather wide hyphae (7–12 μm diam), and thus it may belong to Bourdotigloea. No pigmentation of basal hyphae nor cystidia were mentioned in the protologue, however, and we feel this species deserves further study. The type material of H. irregularis by Olive (1958) from Tahiti consists of undifferentiated, irregularly thick-walled, partly swollen and somewhat winding but rather narrow hyphae. A hyphal structure of this kind looks different from other Helicogloea species although basidia and basidiospores of H. irregularis are more or less typical for this genus. For now, we exclude this species from Helicogloea. Finally, Helicogloea indica Boedijn (1937) was described as having lunate (strongly curved, tapering to both ends) basidiospores and exceptionally narrow hyphae. These features do not fit the generic concept of Helicogloea accepted here.

Bourdot & Galzin (1928) and Bresadola (in Coker 1928) believed that S. ovispora, the type of Saccoblastia, is a species with floccose fructifications, i.e. it belongs to the vicinities of S. farinacea and its relatives. Donk (1958, 1966) provided a detailed argumentation for this viewpoint. However, we cannot accept it for the following reasons. First, the protologue of S. ovispora (Möller 1895: 16) certainly refers to a species with hygroscopic, gelatinized basidiocarps almost disappearing in dry condition (“Bei sehr feuchtem Wetter sieht dieser Ueberzug fast schleimig…, bei trockenem Wetter dagegen bemerkt man nur einen lockeren Hyphenfilz, der bei vollständigem Trockenen zur Unsichtbarkeit zusammenfällt”). This description is not applicable to S. farinacea and closely related species with arid basidiocaps almost unchanging in herbarium. Second, S. ovispora was described and illustrated as a clampless species (“keine Schnallen besitzen” – ibid., p. 16) but all hitherto known species with floccose basidiocarps have clamped hyphae. Third, basidia of S. ovispora are characterized as irregularly curved (“unregelmässig hin und hergebogen” ibid., p. 17). To summarize, gelatinous basidiocarps, clampless hyphae and curved basidia of S. ovispora indicate that it belongs to Helicogloea s. str. The species is typified below with the only authentic specimen so labelled and it is transferred to Helicogloea. Kizimova-Horovitz et al. (2000) proposed to select another of Möller’s species, S. sphaerospora, as a lectotype of the genus. This opportunity is precluded by Art. 10.5 of the Code because the lectotypification by Clements & Shear (1931) has priority. Moreover, as Donk (1958) correctly noted, S. ovispora was the main element of Möller’s generic concept.

Diagnostic features of sexual Helicogloea spp. distributed in temperate Northern Hemisphere are summarized in Table 2.

Helicogloea angustispora L.S. Olive, Bull. Torrey Bot. Club 78: 107. 1951.

Lectotype: USA, North Carolina, Macon Co., Highlands, on very rotten frondose stump in a rhododendron thicket, 29 Aug. 1950 Olive (TENN 43272, selected here) (MycoBank MBT383607).

Synonym: Infundibura adhaerens Nag Raj & Kendrick, Canad. J. Bot. 59: 544. 1981 (fide Kirschner 2004).

Notes: Helicogloea angustispora is the only known representative of the genus with fusiform basidiospores strongly reminiscent of Bourdotigloea. However, all other structures (in particular, hyaline, only faintly cyanophilous basal hyphae and rather narrow, curved basidia with regularly arranged sterigmata) are typical for Helicogloea s. str. Kirschner (2004) proved that Infundibura adhaerens is an asexual morph of H. angustispora.

Helicogloea aquilonia Spirin & V. Malysheva, sp. nov. MycoBank MB825597. Fig. 15.

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Fig. 15.

Basidiospores of Helicogloea spp. A. H. sebacea (lectotype). B. H. crassitexta (holotype). C. H. exigua (holotype). D. H. dryina (holotype). E. H. pellucida (holotype). F. H. subardosiaca (lectotype). G. H. aquilonia (holotype). H. H. burdsalii (holotype). Scale bar = 10 μm.

Etymology: Aquilonius (Lat., adj.) – northern.

Holotype: Russia, Leningrad Reg., Boksitogorsk Dist., Vozhani, Populus tremula, 1 Oct. 2016, Spirin 11163 (H, isotype LE).

Basidiocarps resupinate, 0.05–0.1 mm thick, in fresh condition semitranslucent, waxy, in herbarium specimens covered by greyish pruina or almost invisible. Basal hyphae slightly to distinctly thick-walled, (3.2–)3.6–6.0(–6.2) μm in diam (n = 30/2). Subhymenial hyphae thin-walled, rarely slightly thick-walled, easily collapsing, (1.8–)2.2–3.3(–3.5) μm in diam (n = 30/2). Basidia tubular-clavate, straight or curved, 43–74 × (5.1–) 5.2–7.6(–8.1) μm (n = 30/3), with sharp-pointed sterigmata up to 4 × 1.5 μm; probasidia saccate or clavate, 16–37 × 6.5–11.5 μm. Basidiospores broadly cylindrical to broadly ellipsoid, rarely subglobose, ventral side as a rule flat or convex, (8.2–)8.3–12.8(–13.4) × (5.2–)5.5–9.3(–10.3) μm (n = 160/5), L = 9.91–10.93, W = 6.50–8.03, Q’ = (1.1–)1.2–1.9(–2.0), Q = 1.34–1.63.

Distribution and ecology: Europe (Finland, Germany, Norway, North-West Russia); fallen logs and branches of deciduous trees (Fagus, Populus, Quercus, Salix, Sorbus, Tilia).

Notes: Helicogloea aquilonia is morphologically most similar to H. dryina and H. sebacea, and it differs from those species in having wider basidia and basidiospores. Moreover, H. dryina is so far detected exclusively on Picea abies, while H. sebacea certainly has a more southern distribution.

Helicogloea aurea G.E. Baker, Mycologia 38: 635. 1946.

This species was described from Panama (Baker 1946) and recently reported from Costa Rica (Kisimova-Horovitz et al. 2000). According to descriptions, it is a typical Helicogloea species having gelatinous basidiocarps, clampless, narrow hyphae, and rather large, ovoid basidiospores. However, it is the only species in the genus producing conidia directly in basidiocarps (Kisimova-Horovitz et al. 2000) seemingly causing a golden-yellow colouration of its dry fructifications.

Helicogloea burdsallii Spirin & V. Malysheva, sp. nov. MycoBank MB825598. Fig. 15.

Etymology: After H.H. Burdsall, the eminent North American mycologist.

Holotype: USA, Arizona, Santa Cruz Co., Coronado Nat. Forest, Fraxinus velutina, 12 Aug. 1971, Burdsall 6017 (CFMR, isotype H).

Basidiocarps resupinate, 0.03–0.1 mm thick, in fresh condition semitranslucent, waxy, in herbarium turning to hardly visible greyish bloom. Basal hyphae slightly to distinctly thick-walled, (3.1–)3.2–4.8(–4.9) μm diam (n = 20/1). Subhymenial hyphae thin-walled, (2.2–)2.3–3.3(–3.4) μm diam (n = 20/1). Basidia tubular-clavate, straight or curved, 32–50 × (4.8–)5.0–6.0(–6.1) μm (n = 20/1), with sharp-pointed sterigmata up to 8 × 2 μm; probasidia saccate, 21–26 × 7–8 μm. Basidiospores ellipsoid to broadly ellipsoid, ventral side as a rule flat or convex, rarely slightly concave, (7.3–)8.2–11.6(–12.1) × (5.8–)5.9–7.8(–8.2) μm (n = 60/2), L = 9.00–10.02, W = 6.75–6.78, Q’ = (1.1–)1.2–1.9(–2.0), Q = 1.33–1.49.

Distribution and ecology: North America (USA – Arizona, California); fallen logs of deciduous trees (Fraxinus, possibly Umbellularia).

Notes: Helicogloea burdsallii is morphologically most similar to H. aquilonia, and differs mainly by its shorter basidia. According to DNA data, these species are closely related (Fig. 1, ​,2).2). However, ITS sequences of H. aquilonia are different in about 40 bp from that one of H. burdsallii. According to our current knowledge, distribution areas of these species do not overlap.

Helicogloea caroliniana (Coker) G.E. Baker, Ann. Missouri Bot. Gdn. 23: 92. 1936. Fig. 16.

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Fig. 16.

Basidiospores of Helicogloea spp. A. H. terminalis (holotype). B. H. microsaccata (holotype). C. H. sputum (holotype). D. H. lunula (holotype). E. H. lagerheimii (lectotype). F. H. septifera (holotype). G. H. caroliniana (lectotype). H. H. ovispora (lectotype). Scale bar = 10 μm.

Basionym: Saccoblastia ovispora var. caroliniana Coker, J. Elisa Mitchell Sci. Soc. 35: 121. 1920. Lectotype: USA, North Carolina, Orange Co., Chapel Hill, Quercus sp. (in the hollow of a living tree), 4 Feb. 1920, Couch 4078 (BPI 726596, selected here) (MycoBank MBT383609).

Basidiocarps adpressed-pulvinate, easily detaching from the substrate, up to 2 mm thick in dry condition, amber-coloured, semitransluscent, tuberculate. Basal hyphae slightly to distinctly thick-walled, 3–5 μm diam, strongly swelling in KOH. Subhymenial hyphae scattered in extensive gelatinous matter, thin- to distinctly thick-walled, sturdy, (2.0–)2.2–3.8(–4.1) μm diam (n = 20/1). Basidia tubular-clavate, straight or curved, ca. 80 × 6.6–8.8 μm, with sharp-pointed sterigmata up to 6 × 2 μm; probasidia saccate or clavate, 31–50 × 10–14 μm. Basidiospores cylindrical to broadly cylindrical, often slightly curved, (13.0–) 13.2–16.7(–17.7) × (5.2–)5.7–7.5(–8.7) μm (n = 30/1), L = 14.81, W = 6.51, Q’ = (1.8–)2.0–2.7(–2.8), Q = 2.30.

Distribution and ecology: North America (USA – North Carolina); on Quercus sp.

Notes: This remarkable species is so far known only from the type material. It produces large, hygroscopic, exidioid basidiocarps consisting of an extensive gelatinose matrix and embedded, scattered hyphae and basidia. Helicogloea septifera is most similar to H. caroliniana but it does not produce abundant gelatinous matter detectable in microscopic slides and its hyphae are glued together in a dense tissue. Moreover, basidiospores of H. septifera are wider and occasionally septate.

Helicogloea compressa (Ellis & Everh.) V. Malysheva & K. Põldmaa, comb. nov. MycoBank MB825599.

Basionym: Dendrodochium compressum Ellis & Everh., Bull. Torrey Bot. Club 24: 475. 1897.

Synonym: Helicogloea pauciseptata R. Kirschner & Chee J. Chen, Frontiers in Basidiomycote Mycology: 175. 2004.

Notes: Kirschner (2004) proved a connection of this asexual fungus with a Helicogloea species described as H. pauciseptata. He also proposed a new generic name, Leucogloea, for its asexual morph. Our data confirm that L. compressa is a member of Helicogloea as outlined in this study.

Helicogloea crassitexta V. Malysheva & Spirin, sp. nov. MycoBank MB825600. Figs 3, ​,1515.

Etymology: Crassitextus (Lat., adj.) – possessing distinct tissue.

Holotype: Russia, Krasnoyarsk Reg., Ermakovskoe Dist., Sayano-Shushensky Nat. Res., Pinus sibirica, 17 Aug. 2015 Malysheva (LE 312773, isotype H).

Basidiocarps resupinate, 0.3–0.5 mm thick, in fresh condition semitranslucent, gelatinous, tuberculate, in herbarium specimens turning to a smooth vernicose crust. Basal hyphae slightly to very thick-walled, (4.2–)4.4–7.1(–7.2) μm diam (n = 20/1). Subhymenial hyphae thin- to slightly thick-walled, (2.7–) 3.0–4.6(–4.8) μm diam (n = 20/1). Basidia tubular-clavate, often slightly curved, 70–87 × (5.4–)5.8–7.2(–7.3) μm (n = 20/1), with sharp-pointed sterigmata up to 5 × 2.5 μm; probasidia clavate, 17–26 × 6–8 μm. Basidiospores broadly cylindrical to narrowly ovoid, ventral side slightly concave or convex, (12.2–)12.3–15.2(–16.2) × (6.1–)6.3–9.3(–9.5) μm (n = 30/1), L = 13.75, W = 7.37, Q’ = (1.5–)1.6–2.2(–2.3), Q = 1.88.

Distribution and ecology: Asia (Russia – Siberia); fallen decorticated log of Pinus sibirica.

Notes: Helicogloea crassitexta is morphologically similar to three other long-spored Helicogloea species, distributed in temperate-boreal Eurasia – H. microsaccata, H. subardosiaca and H. septifera. First two species possess thinner basidiocarps, almost invisible in dry condition, and distinctly narrower, thin- or only slightly thick-walled basal hyphae. Helicogloea septifera is seemingly restricted to angiosperm trees in Europe, and its basidiospores are occasionally septate. One specimen from British Columbia (Wells 3141) sequenced during our study shows a 7 bp difference from H. crassitexta. Morphologically, this collection is identical to three other specimens from British Columbia and California (listed as Helicogloea sp. 1 under Specimens examined). These North-American specimens have much thinner basidiocarps than H. crassitexta, and their basidiospores are clearly narrower than in the latter species, (9.7–)10.0–14.3(–14.8) × (5.1–)5.2–7.3(–7.9) μm (n = 120/4), L = 11.03–12.22, W = 5.78–6.14, Q’ = (1.6–)1.7–2.6(–2.7), Q = 1.80–2.12. Therefore, we refrain from considering them conspecific. This problem should be solved based on other DNA markers.

Helicogloea dryina Spirin & Miettinen, sp. nov. MycoBank MB825601. Fig. 15.

Etymology: Dryinus (Lat., adj.) – wood-inhabiting.

Holotype: Norway, Akershus, Nannestad, Picea abies, 8 Oct. 2011, Svantesson 786 (O, isotype H).

Basidiocarps resupinate, 0.02–0.1 mm thick, whitish or greyish, waxy, sometimes not macroscopically visible, developing as hyphae with basidia inside or under basidiocarps of corticioid fungi. Hyphae thin- or slightly thick-walled, (2.2–)2.3–3.4(–3.8) μm diam (n = 20/1), not differentiated. Basidia tubular-clavate, often clearly curved, 25–68 × (3.1–)4.2–5.5(–5.6) μm (n = 32/3), with sharp-pointed sterigmata up to 5 × 2.5 μm; probasidia clavate, occasionally constricted at the middle part, 23–37 × 5–9 μm (n = 20/2), sometimes strongly reduced and thus difficult to observe. Basidiospores broadly ellipsoid to subglobose, occasionally lacrymoid, some spores distinctly arcuate near apiculus, (7.2–) 7.3–10.2(–10.7) × (6.0–)6.1–7.9(–8.2) μm (n = 120/4), L = 8.38–9.19, W = 6.60–7.11, Q’ = 1.1–1.4(–1.5), Q = 1.18–1.30.

Distribution and ecology: Europe (Finland, Germany, Norway, Sweden); fallen logs of Picea abies.

Notes: Helicogloea dryina is a distinct species due to clearly curved basidia and relatively large, broadly ellipsoid spores. It has often been found inside or under basidiocarps of corticioid fungi, mostly Botryobasidium spp., but no haustorial cells connected with hyphae of the host species were detected. Moreover, H. dryina is able to produce its own, sometimes rather extensive and well-visible basidiocarps. It seems that it is a saprotrophic species using the host tree and that it is facilitated by Botryobasidium and some other corticioid fungi. No parasites are so far recognised among the corticioid members of the Atractiellales. All our records of H. dryina come from coarse spruce logs at an advanced decay stage, and from old natural-like spruce forests. The specimens were collected from September to November.

Helicogloea eburnea A. Savchenko & V. Malysheva, sp. nov. MycoBank MB825602. Figs 3, ​,1717.

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Fig. 17.

Helicogloea eburnea (holotype). Hyphae, conidiophores (scale bar = 10 μm) and conidia (scale bar = 5 μm).

Etymology: Eburneus (Lat., adj.) – ivory.

Holotype: Kenya, Taita-Taveta, Taita Hills, Chawia, decayed hardwood log, 17 Nov. 2017, Savchenko 171127/1127A (H7008830, isotypes LE and EA).

Sporodochia pustulate, gelatinous and soft, white semitranslucent; separate pustules up to 1 mm diam and 400 μm thick, partly coalescing, in herbarium shrinking to a thin, waxy, yellowish film. Internal hyphae with thickened (up to 0.3–0.5 μm) walls, 1.5–2.5(–3) μm diam. Surface hyphae thin- to slightly thick-walled (wall 0.1–0.3 μm thick), 1.5–2 μm diam. Conidiophores irregularly branched, branches generally parallel to the main axis. Conidiogenous cells cylindrical to slightly obclavate, straight or curved, tapering to the apex, with multiple indistinct annellation scars at the top, 12–34 × 1.5–2.6 μm. Conidia subglobose to ellipsoid, smooth, hyaline, slightly thick-walled, (2.8–)2.9–3.7(–4) × (2–)2–2.6(–2.7) μm (n = 30/1).

Distribution and ecology: Africa (Kenya); well-decayed decorticated angiosperm log.

Notes: Helicogloea eburnea is closely related to another asexual species of the genus, H. compressa (see above). Morphologically, they are evidently indistinguishable but differ in their DNA sequences and geographic distribution.

Helicogloea exigua Spirin & V. Malysheva, sp. nov. MycoBank MB825603. Fig. 15.

Etymology: Exiguus (Lat., adj.) – thin.

Holotype: USA, Michigan, Marquette Co., Big Bay, Acer saccharum, 6 Aug. 1974, Burdsall 8162 (CFMR FP-8162, isotype H).

Basidiocarps resupinate, 0.02–0.04 mm thick, in fresh condition semitranslucent, waxy, in herbarium specimens covered by greyish pruina, almost invisible. Basal hyphae slightly to distinctly thick-walled (walls unevenly thickened, up to 1 μm thick), (3.0–)3.2–5.3(–5.6) μm diam (n = 40/2), occasionally inflated up to 6–6.5 μm diam, sturdy. Subhymenial hyphae thin- to slightly thick-walled, (2.0–)2.2–3.3(–3.7) μm diam (n = 20/1). Basidia tubular-clavate, often curved, 29–38 × (3.4–)3.9–5.0(–5.2) μm (n = 22/2), with sharp-pointed sterigmata up to 5 × 1.5 μm; probasidia clavate, 12–33 × 4–5 μm. Basidiospores cylindrical, often slightly curved, occasionally ovoid to narrowly ellipsoid, (6.8–)7.0–10.6(–10.8) × (3.8–)3.9–5.6(–5.8) μm (n = 90/3), L = 7.94–8.99, W = 4.23–4.76, Q’ = (1.4–)1.5–2.4(–2.5), Q = 1.73–2.02.

Distribution and ecology: Europe (France), North America (Canada – Ontario, USA – Michigan); fallen logs of deciduous trees (Acer, Betula, Populus).

Notes: Helicogloea exigua is most similar to H. pellucida and H. sebacea but it possesses distinctly narrower basidiospores and basidia. It seemingly prefers well-decayed wood of deciduous trees although data on its ecology and distribution are still insufficient.

Helicogloea globosa Chee J. Chen & Oberw., Mycotaxon 76: 280. 2000.

Notes: This species was described based on one specimen collected on an unidentified deciduous host in Taiwan (Chen & Oberwinkler 2000). The protologue of H. globosa points towards H. aquilonia. However, the basidiospores of H. globosa were described and illustrated as globose to subglobose, 8–10 × 7–9 μm while they are predominantly broadly cylindrical to broadly ellipsoid in all collections of H. aquilonia studied by us. Moreover, there are no records of the latter species outside of North Europe. Another similar species from Europe, H. dryina, has on average narrower basidiospores and strongly curved basidia, and it occurs exclusively on fallen spruce logs.

Helicogloea inconspicua G.E. Baker, Mycologia 38: 635. 1946.

Notes: This species was described based on a single collection from Columbia (Baker 1946). It was differentiated from H. intermedia due to regularly 1–2-septate basidiospores. However, the reliability of this feature is vague because all other characters fit well to H. intermedia. Further studies are needed to re-confirm the status of H. inconspicua.

Helicogloea incrustans Kobayasi, Misc. Rep. Res. Institute Nat. Resources 17–18: 45. 1950.

Notes: So far, this species is known only from the type locality in Japan (Kobayashi 1950). Rather thick, extensive, gelatinous fructifications, as well as large, 1–3-septate basidiospores point towards possible affinities to H. septifera from Europe. However, basidiospores of H. incrustans are certainly longer and wider than in the latter species. The identity of H. incrustans deserves further study.

Helicogloea intermedia (Linder) G.E. Baker, Ann. Missouri Bot. Gdn. 23: 91. 1936.

Basionym: Saccoblastia intermedia Linder, Ann. Missouri Bot. Gdn. 16: 487. 1929. Lectotype: Cuba, Pinar del Río, Soledad, on moist decaying stump, Sep. 1924, Linder (MO, not studied) (selected by Baker 1936: 92).

Notes: We studied one collection from Panama (FH 00304773) which agrees in all essential aspects with the protologue of H. intermedia (Linder 1929). It has thin, gelatinous basidiocarps, four-celled, slightly curved basidia 60–70 × 8–10 μm, and narrowly ellipsoid or broadly cylindrical, occasionally one-septate basidiospores, (15.0–)15.1–19.8(–21.6) × (7.4–)7.7–9.2(–9.3) μm (n = 30/1), L = 17.54, W = 8.39, Q’ = (1.7–)1.8–2.4(–2.6), Q = 2.09. If our identification is correct, H. intermedia belongs in the vicinity of H. lagerheimii. The latter species, however, produces more extensive fructifications and shorter basidiospores but longer basidia. Identity of H. intermedia versus H. inconspicua must be re-checked based on newly collected and sequenced material.

Helicogloea lagerheimii Pat., Bull. Soc. Mycol. France 8: 121. 1892. Fig. 16.

Lectotype: Ecuador, Baños, Chorrera de Agoyan, rotten branch, Jan. 1892, Lagerheim (FH 00304791, selected by Baker 1936: 93).

Basidiocarps resupinate, up to 1 mm thick, in fresh condition semitranslucent, waxy, greyish, tuberculate, in herbarium specimens turning to brownish vernicose crust. Basal hyphae slightly to distinctly thick-walled, (3.6–)3.9–6.2(–6.7) μm diam (n = 20/1). Subhymenial hyphae thin- to slightly thick-walled, easily collapsing, (2.7–)2.8–4.1(–4.2) μm diam (n = 20/1). Basidia tubular-clavate, straight or curved, 75–114 × 7.5–8 μm, with sharp-pointed sterigmata up to 5 × 2 μm; probasidia saccate or clavate, 29–43 × 8.5–11.5 μm. Basidiospores narrowly ellipsoid to broadly cylindrical, ventral side flat or slightly concave, rarely slightly convex, occasionally 1-septate, (13.1–)13.3–18.2(–19.0) × (6.3–)6.4–9.3(–9.4) μm (n = 32/1), L = 15.33, W = 8.23, Q’ = (1.5–)1.6–2.2(–2.3), Q = 1.88.

Distribution and ecology: North America (USA – California), South America (Ecuador); rotten wood of deciduous trees.

Notes: The description above is based on the type specimen only. Helicogloea lagerheimii is undoubtedly congeneric with other species treated here under Helicogloea s. str. A specimen from California (BPI 719891) used in DNA studies is morphologically almost identical to the type material, having basidiospores (13.1–)13.7–16.9(–17.2) × (7.2–)7.6–9.1(–9.2) μm (n = 30/1), L = 15.49, W = 8.33, Q’ = (1.6–)1.7–2.0(–2.1), Q = 1.86, although it possesses shorter basidia, up to 80 μm long. Newly collected and sequenced specimens from Ecuador are needed to designate an epitype for H. lagerheimii.

Helicogloea lunula Spirin & V. Malysheva, sp. nov. MB825604. Fig. 16.

Etymology: Lunulus (Lat., adj.) – lunate.

Holotype: New Zealand, Wairarapa, Pigeon Bush Res., decorticated branch, 1 Jan. 2006, Paulus & Steer (PDD 88360).

Basidiocarps resupinate, extensive (covering several cm), 0.1–0.2 mm thick, waxy-gelatinous, whitish-greyish, opaque. Basal hyphae slightly to distinctly thick-walled, (4.8–)5.1–9.2(–9.7) μm diam (n = 20/1), often rather short-celled and sometimes constricted at septa. Subhymenial hyphae thin- to slightly thick-walled, (3.2–)3.4–5.3(–5.4) μm diam (n = 20/1), mostly rather short-celled, some bearing several constrictions at the terminal part (moniliform). Oil droplets abundant in slides made in CB. Basidia tubular-clavate, often curved, 39–62 × (5.0–)5.1–6.7(–7.2) μm (n = 22/2), with sharp-pointed sterigmata up to 6 × 3 μm; probasidia saccate or clavate, 16–21 × 6.5–9 μm. Basidiospores cylindrical, often distinctly curved, (12.0–)12.6–15.7(–16.0) × (4.8–)4.9–6.1(–6.2) μm (n = 30/1), L = 13.95, W = 5.32, Q’ = (2.2–) 2.3–2.9(–3.0), Q = 2.63.

Distribution and ecology: New Zealand; fallen decorticated branch.

Notes: Helicogloea lunula produces rather extensive basidiocarps with opaque (not semitranslucent) hymenial surface. They are gelatinized, however, as in other species of Helicolgoea s. str. Distinctly curved basidiospores and a presence of moniliform hyphal ends in hymenium are good diagnostic features of this species.

Helicogloea microsaccata V. Malysheva & Spirin, sp. nov. MycoBank MB825605. Figs 3, ​,1616.

Etymology: Microsaccatus (Lat., adj.) – bearing small-sized probasidial sacs.

Holotype: Russia, Primorie, Ussuriisk Dist., Ussuri Nat. Res., deciduous tree (fallen branch), 15 Aug. 2011, Malysheva (LE 262936, isotype H).

Basidiocarps resupinate, 0.03–0.06 mm thick, in fresh condition semitranslucent, waxy, in herbarium specimens almost invisible. Basal hyphae thin- to slightly thick-walled, (3.1–)3.3–5.2(–6.2) μm diam (n = 20/1), easily collapsing. Subhymenial hyphae thin- or slightly thick-walled, (2.3–)2.4–3.9(–4.0) μm diam (n = 20/1). Basidia tubular-clavate, often curved, 53–73 × (6.1–)6.2–8.2(–8.3) μm (n = 21/1), with sharp-pointed sterigmata up to 6.5 × 2.5 μm; probasidia saccate or clavate, 15–27 × 7–11 μm. Basidiospores cylindrical to broadly cylindrical, often slightly curved, more rarely ovoid, (10.4–)10.8–15.2 × (6.1–)6.2–9.3(–9.5) μm (n = 30/1), L = 13.08, W = 7.42, Q’ = (1.5–)1.6–2.0(–2.2), Q = 1.77.

Distribution and ecology: East Asia (Russia – Primorie); fallen hardwood branch.

Notes: Helicogloea microsaccata is morphologically most similar to H. subardosiaca, and it differs from the latter primarily by its shorter basidia and smaller probasidial sacs. Moreover, H. subardosiaca is a European species known exclusively from coniferous hosts while H. microsaccata has been detected in East Asia on hardwood. DNA data show that these species are not closely related.

Helicogloea ovispora (A. Möller) Spirin, comb. nov. MycoBank MB825606. Figs 3, ​,1616.

Basionym: Saccoblastia ovispora A. Möller, Botanische Mittheilungen aus den Tropen 8: 16. 1895.

Lectotype: Brazil, Santa Catharina, Blumenau, rotten wood, Möller 767 (HBG, selected here) (MycoBank MBT 383610).

Basidiocarps resupinate, up to 1 mm thick, semitranslucent, waxy, well visible in dry condition. Basal hyphae slightly to distinctly thick-walled, (5.0–)5.1–7.2(–8.2) μm diam (n = 20/1). Subhymenial hyphae thin- to slightly thick-walled, (2.8–)2.9–4.1(–4.2) μm diam (n = 20/1). Basidia tubular-clavate, straight or curved, 79–100 × 8–10.5 μm, with sharp-pointed sterigmata up to 5 × 2 μm; probasidia saccate or clavate, 23–56 × 10–12 μm. Basidiospores cylindrical to broadly cylindrical, often slightly curved, occasionally 1–3-septate, (14.8–)15.0–20.2(–23.8) × (7.9–)8.0–11.1(–11.8) μm (n = 30/1), L = 17.29, W = 9.30, Q’ = (1.5–)1.6–2.1(–2.2), Q = 1.87.

Distribution and ecology: South America (Brazil – Santa Catarina); still corticated logs and branches.

Notes: The only authentic specimen of Saccoblastia ovispora collected and labelled by Möller survived in herbarium HBG (Friedrichsen 1977). It was studied by us and served as a source of the description above. Möller (1895) presented the basidiospore dimensions of S. ovispora in a somewhat confusing manner, and this probably was a reason for Baker (1936) and Lowy (1971) to consider it conspecific with H. lagerheimii. In the protologue, Möller (1895: 18) stated that basidiospores of S. ovispora still attached to sterigmata have dimensions 13 × 7–8 μm, while mature, detached spores reach up to 26 × 10 μm. The concise diagnosis provided in the end of his book (ibid., p. 162) refers to juvenile basidiospores only. Our measurements given above are based exclusively on mature basidiospores.

Later records of S. ovispora were published by Rick (1933, 1958). We studied duplicates of his collections kept in FH (treated as Helicogloea sp. 2 in Specimens examined). They are thinner than the lectotype, 0.02–0.05 mm thick, almost invisible in dry condition, and they possess distinctly narrower basal hyphae, (3.6–)3.8–5.2(–5.7) μm diam (n = 20/1). Basidiospores in Rick’s collections are not septate, (14.7–)15.3–22.2(–22.6) × (6.3–)7.0–10.0(–10.1) μm (n = 40/2), L = 19.78–20.01, W = 7.77–8.49, Q’ = (1.8–)1.9–3.1(–3.5), Q = 2.39–2.56, i.e. they are somewhat narrower than in H. ovispora sensu typi. This indicates that Rick’s material belongs to yet another, seemingly unnamed Helicogloea species. We leave this problem for later study.

Helicogloea pellucida Spirin & V. Malysheva, sp. nov. MycoBank MB825607. Fig. 15.

Etymology: Pellucidus (Lat., adj.) – semitranslucent.

Holotype: Russia, Nizhny Novgorod Reg., Lukoyanov Dist., Razino, Alnus glutinosa (fallen log), 10 Aug. 2016, Spirin 10610 (H, isotype LE).

Basidiocarps resupinate, 0.05–0.1 mm thick, in fresh condition semitranslucent, waxy, in herbarium specimens covered by greyish pruina, almost invisible. Basal hyphae thin-walled, (3.2–)3.8–4.6(–4.9) μm diam (n = 20/1), easily collapsing. Subhymenial hyphae similar, (2.0–)2.2–3.7(–3.8) μm diam (n = 20/1). Basidia tubular-clavate, slightly curved or twisted, 31–40 × (3.8–)4.2–5.4(–5.8) μm (n = 20/3), with sharp-pointed sterigmata up to 4 × 1.5 μm; probasidia clavate, 15–20 × 5–7 μm, occasionally 1–2-septate. Basidiospores broadly cylindrical to narrowly ellipsoid, sometimes lacrymoid, ventral side as a rule flat or slightly concave, (7.2–)7.3–10.8(–12.0) × (4.1–)4.6–6.4(–6.6) μm (n = 140/5), L = 8.58–9.24, W = 5.19–5.51, Q’ = (1.3–)1.4–2.0(–2.1), Q = 1.56–1.75.

Distribution and ecology: Europe (Norway, Russia, Ukraine), North America (Canada – Ontario, USA – Massachusetts, North Carolina); fallen logs of deciduous trees (Alnus, Fraxinus, Malus, Populus).

Notes: Thin-walled hyphae throughout the basidiocarp and rather narrow basidiospores make H. pellucida differ from the similarly looking H. sebacea and H. aquilonia. Basidiospores of H. exigua are cylindrical, often more distinctly curved, and they are even narrower than in H. pellucida. Basidial width can also help in identification of these four species although its value is limited to fresh or recent material.

Helicogloea sebacea (Bourdot & Galzin) Spirin & Trichies, comb. nov. MycoBank MB825608. Fig. 15.

Basionym: Saccoblastia sebacea Bourdot & Galzin, Bull. Soc. Mycol. France 25: 15. 1909.

Lectotype: France, Allier, St. Priest, Cerasus (?) (very rotten wood), 26 Nov. 1908, Bourdot 5882 (PC 0706732, isolectotype S F21004, selected here) (MycoBank MBT383611).

Basidiocarps resupinate, 0.05–0.1 mm thick, whitish or greyish, waxy. Basal hyphae slightly to distinctly thick-walled, (4.1–)4.2–5.4(–6.1) μm diam (n = 20/2). Subhymenial hyphae thin- or slightly thick-walled, (2.1–)2.2–4.3(–4.7) μm diam (n = 22/2). Basidia tubular-clavate, often moderately curved or twisted, 27–48 × (5.1–)5.2–6.8(–7.3) μm (n = 33/3), with sharp-pointed sterigmata up to 9 × 2.5 μm; probasidia clavate to saccate, 19–30 × 6–9 μm. Basidiospores broadly cylindrical to narrowly ellipsoid, ventral side as a rule concave or flat, (7.3–)7.6–12.8(–13.2) × (5.0–)5.1–7.3(–7.5) μm (n = 210/7), L = 8.95–11.39, W = 5.78–6.26, Q’ = (1.3–)1.4–2.2(–2.3), Q = 1.54–1.83.

Distribution and ecology: Europe (Denmark, Estonia, France, Germany, Russia, Ukraine), Asia (Russian Far East), North America (USA – Ohio, South Carolina, Tennessee); fallen and rather rotten logs of deciduous trees (Acer, Betula, Fagus, Fraxinus, Quercus etc.).

Notes: Helicogloea sebacea was described from the southern part of France based on several collections (Bourdot & Galzin 1909). The best-preserved specimen is selected here as a lectotype. Later Bourdot & Galzin (1927) also introduced a subspecies subardosiaca which we consider a separate species (see below). The type material of Helicobasidium inconspicuum (described from Austria – Höhnel 1908) fits our concept of H. sebacea although it possesses distinctly thick-walled hyphae throughout. The identity of this taxon deserves further study; however, even if it proves to be a good species, H. inconspicuum cannot be combined to Helicogloea, due to the existence of another species with the same epithet (see above).

Helicogloea septifera Spirin & V. Malysheva, sp. nov. MycoBank MB825609. Figs 3, ​,1616.

Etymology: Septiferum (Lat., adj.) – bearing septa (referring to a presence of septate basidiospores).

Holotype: Norway, Nord-Trøndelag, Grong, Sanddøla, Ulmus sp., 13 Jul. 1977, Holten & Siversten (H, isotype TRH 22196, paratypes with the same collecting data – TRH 9167, TRH F16554).

Basidiocarps resupinate, 0.5–2 (3) mm thick, in fresh condition semitranslucent, whitish or greyish, gelatinous, in herbarium turning to perceptible, pale ochraceous or brownish vernicose film, hymenial surface often tuberculate. Basal hyphae slightly to moderately thick-walled, (3.4–)4.1–6.1(–6.4) μm diam (n = 30/2). Subhymenial hyphae thin- to slightly thick-walled, (2.6–) 2.7–4.4(–5.0) μm diam (n = 40/2). Basidia tubular-clavate, slightly or distinctly curved, 56–101 × (6.7–)6.8–9.0(–9.2) μm (n = 40/2), with sharp-pointed sterigmata up to 10 × 5 μm; probasidia saccate or clavate, 18–52 × 6.5–10 μm. Basidiospores broadly cylindrical to narrowly ellipsoid, ventral side as a rule concave or flat, occasionally 1–2-septate, (10.8–)11.1–16.2 × (5.8–)6.2–9.1(–9.5) μm (n = 110/4), L = 13.09–14.67, W = 7.14–7.92, Q’ = (1.4–)1.5–2.3(–2.6), Q = 1.84–1.94.

Distribution and ecology: Europe (Norway, Russia), North America (USA – Iowa); recently fallen logs and thick branches of deciduous trees (Alnus, Betula, Populus, Sorbus, Ulmus).

Notes: Roberts (2002) reported and described this species from Norway as H. caroliniana. We studied the type material of the latter species and found it distinctly different from our specimens from Europe (see remarks under H. caroliniana). Basidiocarps of H. septifera are normally rather thin (0.5–1 mm) and look the same as in many other species of the genus. Pulvinate and abnormally thick basidiocarps are infected by a pucciniomycete Achroomyces chlamydospora (Roberts 2002) whose presence most probably causes this unusual fructification growth. The same phenomenon occurs in some Botryobasidium species infected by Spiculogloea spp. (Spirin et al. 2016). So far, A. chlamydospora was known only from the type locality in Norway. Here it is reported from two new localities in the country; in one case, the host species was H. aquilonia.

Helicogloea sputum Spirin & V. Malysheva, sp. nov. MycoBank MB825610. Fig. 16.

Etymology: Sputum (Lat., noun) – spittle; in metaphoric sense, “sputum” also refers to a thin layer of some substance.

Holotype: Norway, Vestfold, Larvik, Jordstøyp i Kvelde, Populus tremula, 19 Oct. 1995, Andersen (O F-90728).

Basidiocarps resupinate, 0.05–0.07 mm thick, in fresh condition semitranslucent, waxy, in herbarium specimens almost invisible. Basal hyphae thin- to slightly thick-walled, (3.4–)3.6–5.8(–6.0) μm diam (n = 20/1). Subhymenial hyphae thin-walled, (2.3–) 2.4–4.2(–4.7) μm diam (n = 20/1). Basidia tubular-clavate, often curved, 52.5–71 × (5.6–)6.0–8.7(–9.2) μm (n = 20/1), with sharp-pointed, occasionally bi- or trifuracte sterigmata up to 12 × 3.5 μm; probasidia clavate, 34–47 × 7–10 μm. Basidiospores broadly cylindrical to ellipsoid, more rarely ovoid, (12.1–)12.2–15.6(–16.2) × (6.2–)6.3–8.3(–8.8) μm (n = 30/1), L = 13.82, W = 7.17, Q’ = (1.5–)1.6–2.3(–2.6), Q = 1.94, occasionally germinating by bifurcate sterigmata.

Distribution and ecology: Europe (Norway); fallen decorticated log (Populus).

Notes: Very thin basidiocarps and rather short basidia occasionally bearing bi- to trifurcate sterigmata help to separate this species from other European long-spored species, i.e. H. septifera and H. subardosiaca.

Helicogloea subardosiaca (Bourdot & Galzin) Donk, Persoonia 4: 213. 1966. Figs 5, ​,1515.

Basionym: Saccoblastia sebacea ssp. subardosiaca Bourdot & Galzin, Hyménomycètes de France: 5. 1927.

Lectotype: France, Aveyron, Causse Noir, Pinus sylvestris, 9 Dec. 1910, Galzin 7868 (PC 0706709, selected here) (MycoBank MBT383612).

Basidiocarps resupinate, 0.05–0.2 mm thick, in fresh condition semitranslucent, greyish, waxy, in herbarium turning to almost invisible vernicose film. Basal hyphae slightly thick-walled, (3.7–)3.8–5.2(–5.3) μm diam (n = 40/4). Subhymenial hyphae thin- to slightly thick-walled, (2.3–)2.7–4.4(–4.7) μm diam (n = 80/4). Basidia tubular-clavate, slightly twisted or curved, 60–110 × (5.2–)5.7–7.6(–7.9) μm (n = 30/3), with sharp-pointed sterigmata up to 15 × 3.5 μm; probasidia clavate, 20–43 × 6–9.5 μm. Basidiospores cylindrical to narrowly ellipsoid, ventral side as a rule concave (especially in longest spores), more rarely flat, (10.7–)10.8–18.0(–18.4) × (5.2–)5.7–8.5(–9.0) μm (n = 140/5), L = 12.22–14.71, W = 6.50–7.11, Q’ = (1.5–)1.6–2.5(–2.6), Q = 1.76–2.19.

Distribution and ecology: Europe (Finland, France); fallen decorticated conifer logs (Pinus sylvestris, possibly also Picea abies).

Notes: Helicogloea subardosiaca is a long-spored, conifer-dwelling species distributed in Europe, appearing very late in the season. Morphological differences of H. subardosiaca from other similarly looking species are discussed under H. crassitexta. While restoring H. subardosiaca as a species, Donk (1966) claimed he studied collections of this species from Sweden although he did not specify in which herbarium they were being kept.

Helicogloea terminalis L.S. Olive, Bull. Torrey Bot. Club 81: 331. 1954. Fig. 16.

Holotype: USA, North Carolina, Macon Co., Highlands, Betula sp., 14 Aug. 1952, Olive (NY 00834144, studied).

Notes: The species is known so far from the type specimen collected in North Carolina (Olive 1954). Basidiocarps are very thin, inconspicuous, consisting of a few, parallel, terminally ascending hyphae (2.8–)3–4.0(–4.4) μm diam and bearing saccate probasidia 33–54 × 6–9 μm. Basidia four-celled, about 40 × 5–7 μm, arising both laterally or terminally from probasidia. Chen & Oberwinkler (2000) argued that terminal origin of basidia from probasidial cells precludes an affinity of H. terminalis to other Helicogloea species. After studying the type specimen, we conclude that this is an artefact most probably caused by extreme thinness of the basidiocarps. A presence of “normal” basidia developing from probasidia laterally in the type of H. terminalis supports our idea. Basidiospores of H. terminalis are broadly cylindrical, often slighlty curved, (11.6–) 12.0–15.3(–16.0) × (5.0–)5.1–7.1(–7.2) μm (n = 30/1), L = 13.82, W = 6.06, Q’ = (1.9–)2.0–2.7(–2.8), Q = 2.30. Thin basidiocarps and basidiospore shape and dimensions place H. terminalis in a difficult species complex containing also H. microsaccata and H. subardosiaca. However, none of these species possess terminally arising basidia, and they all have well-differentiated subicular hyphae. New, sequenced specimens are needed to define a proper place for H. terminalis within the genus.

Helicogloea variabilis K. Wells, Mycol. Res. 94: 835. 1990.

Notes: This species was described from Brazil based on single collection (Wells 1990). Morphology as well as DNA data confirm that it belongs to the genus Helicogloea s. str.

Saccosoma Spirin, gen. nov. MycoBank MB825611.

Basidiocarps resupinate, thin to rather thick, arid, floccose to dense, white to cream-coloured. Hyphae clamped, thin-walled to distinctly thick-walled, 3–8 μm diam, slightly cyanophilous. Poorly differentiated cystidia present in one species. Basidia four-celled, tubular-clavate, straight; probasidia narrowly saccate to clavate, simple or bifurcate. Basidiospores narrowly ellipsoid to subglobose, 6–23 × 5–15 μm, with blunt, prominent apiculus.

Type species: Saccosoma farinaceum (Höhn.) Spirin & K. Põldmaa.

Notes: The genus is introduced here to replace Saccoblastia sensu Donk (1966). Morphologically, it differs from both Bourdotigloea and Helicogloea s. str. in having non-gelatinised, arid, perceptible basidiocarps consisting of rather loosely interwoven, clamped hyphae. Hyphae are more or less uniform, not differentiated between subhymenium and subiculum as in Bourdotigloea and Helicogloea, except S. contortum. In contrast to Helicogloea spp., basidia in Saccosoma are straight, not curved, with a terminal cell bearing an apical (but occasionally somewhat asymmetric) sterigma.

Saccosoma album (Burt) Spirin, comb. nov. MycoBank MB825612.

Basionym: Septobasidium album Burt, Ann. Missouri Bot. Gdn. 13: 332. 1926.

Notes: Couch (1949) re-described and illustrated this species and moved it to Helicogloea s. lat. Morphological features and DNA data confirm that it is a member of Saccosoma. It is so far known only from New Zealand.

Saccosoma contortum (G.E. Baker) Spirin, comb. nov. MycoBank MB825613.

Basionym: Helicogloea contorta G.E. Baker, Mycologia 38: 634. 1946.

Basidiocarps resupinate, appearing as small, cream-coloured, soft, floccose patches, later fusing together and reaching up to 3 cm in diam, adnate, densely floccose, 0.07–0.1 mm thick; margin arachnoid. Hyphae thick-walled, 3–5 μm in diam in basal part, strongly coiled and 1.5–2.5 μm diam in subhymenium. Basidia 40–50 × 7–9 μm; probasidia narrowly saccate to clavate, thin-walled, 30–40 × 7–9 μm. Basidiospores ovoid to broadly ellipsoid, (10.3–)10.9–14.0(–14.7) × (8.1–)8.2–10.2(–11.0) μm (n = 30/1), L = 12.35, W = 8.90, Q’ = (1.2–)1.3–1.5(–1.6), Q = 1.39.

Distribution and ecology: North America (USA – Iowa, Florida); wood remnants of deciduous trees (Liquidambar, Quercus) and palms.

Notes: Coiled hyphae and rather short basidia differentiate S. contortum from other species in the genus. No DNA sequences have been available for this species so far.

Saccosoma farinaceum (Höhn.) Spirin & K. Põldmaa, comb. nov. MycoBank MB825614. Figs 3, ​,6,6, ​,1818.

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Fig. 18.

Basidiospores of Saccosoma spp. A. S. farinaceum f. alniviridis (Kotiranta 13179). B. S. farinaceum (neotype). C. S. floccosum (holotype). Scale bar = 10 μm.

Basionym: Helicobasidium farinaceum Höhn., Sitzungsb. Kaiserl. Akad. Wissenschaften Math.-Naturwiss. Klasse Abt. I 116: 84. 1907.

Neotype: Russia, Nizhny Novgorod Reg., Lyskovo Dist., Makarievo, dry branches of Salix sp., 11 Aug. 2015, Spirin 9099 (H, selected here) (MycoBank MBT383613).

Synonyms: Saccoblastia pinicola Bourdot & Galzin, Bourdot & Galzin, Bull. Soc. Mycol. France 25: 15. 1909. Lectotype: France, Aveyron, Millau, Causse Noir, Pinus sylvestris (fallen branches), 10 Nov. 1908, Galzin (herb. Bourdot 6939) (S F-21016, selected here) (MycoBank MBT383614).

Stypinella killermannii Bres. in Killermann, Denkschr. Baierischen Bot. Gesellsch. Regensburg 15: 34. 1922. Lectotype: Germany, Bayern, Passau, Pinus sp. (manufactured wood), Sep. 1919, Killermann (BPI 726593, selected here) (MycoBank MBT383615).

Basidiocarps orbicular, adnate, appearing as small, cream-colored, rather dense, farinaceous patches, a few mm diam, later fusing together and covering several cm, up to 0.5 mm thick; margin floccose-pruinose, gradually thinning-out. Hyphae thin-walled or with distinct walls (wall up to 0.5 μm thick), (2.8–) 3.0–6.3(–7.2) μm diam (n = 200/10). Basidia 71–140 × (7.3–) 7.8–13.2(–13.8) μm (n = 190/11); probasidia narrowly saccate to clavate, occasionally furcate, thin- to slightly thick-walled, 28.5–81 × 10–17.5 μm, occasionally with 1–3 adventive septa. Basidiospores broadly to narrowly ellipsoid, rarely ovoid, (11.6–) 12.0–20.1(–20.6) × (8.1–)8.2–14.5(–15.8) μm (n = 377/12), L = 14.46–17.92, W = 9.56–13.08, Q’ = (1.1–)1.2–1.7(–1.8), Q = 1.31–1.58.

Distribution and ecology: Europe (Austria, Denmark, Estonia, Finland, France, Germany, Norway, Russia, Sweden, Ukraine, United Kingdom), North America (Canada, USA); still attached thin branches, rarely recently fallen logs of deciduous trees (Acer, Corylus, Fagus, Fraxinus, Populus, Quercus, Salix, Ulmus) and more rarely conifers (Abies, Picea, Pinus).

Notes: Höhnel (1907) described this species as Helicobasidium farinaceum based on single collection from Austria. It was almost forgotten until D.P. Rogers (in Martin 1944) studied the type and concluded it is the same species as Saccoblastia pinicola. Rogers moved H. farinaceum to Helicogloea, in accordance with the genus concept introduced by Baker (1936). It seems that Höhnel’s original specimen does not exist anymore: it could not be located in FH and our request to W remained unanswered. Therefore, the only source for judging H. farinaceum sensu orig. is its protologue. Höhnel’s description referred to a pale-coloured, non-gelatinized, resupinate fungus of fine-granular, mealy consistence (“feinkörnig-mehlig”) and possessing clamped hyphae. These statements preclude Helicogloea s. str. Basidiocarps of H. farinaceum were described as initially patch-like, then fusing together and gradually thinning-out in marginal areas (“fleckenartig, dann zu ausgebreiten Überzügen zusammenfliessend, dünn…, gegen den Rand ganz allmählig verlaufend”). These features, together with microscopic characters (diameter of hyphae, width of basidia and dimensions of basidiospores) are crucial for our understanding of this species, and they correspond to recent collections used in the present phylogenetic studies. One of them is designated here as a neotype of H. farinaceum.

Morphological study reveals a considerable variation of S. farinaceum. In particular, specimens collected from coniferous hosts produce abundant bifurcate probasidia and on average larger basidiospores. However, ITS sequences show only negligible differences between collections from various host trees and geographic regions. Therefore, S. farinaceum is accepted here in a wide sense, i.e. including S. pinicola, although we cannot preclude that it contains several cryptic species.

The protologue of Platygloea laplata (Lindsey 1986) and its redescription by Hauerslev (1999) suggest it may be a synonym of S. farinaceum. Lindsey described P. laplata as growing on living basidiocarps of Peniophora nuda and supposed it was parasitic. One of our collections of S. farinaceum came from living and sporulating fruitbodies of Aleurodiscus grantii. However, no specific cells (haustoria or appressoria), characteristic for parasitic heterobasidiomycetes, were detected in this collection, and they were not mentioned in descriptions of P. laplata. Therefore, we consider their growth on other fungi merely coincidental.

Specimens macroscopically identical to S. farinaceum but having wider hyphae and larger basidia and basidiospores than S. pinicola were collected in subalpine forests of Eurasia and North America. They all came from branches of shrub-like alders (Alnus viridis group). No certain differences were detected in ITS region between them and S. farinaceum s. str., and therefore these specimens are redescribed here under an older name (forma alniviridis) introduced by Bourdot (1932).

Saccosoma farinaceum f. alniviridis Bourdot, Bull. Soc. Mycol. France 48: 204. 1932. Fig. 18.

Synonym: Achroomyces sibiricus Hauerslev, Mycotaxon 72: 467. 1999. Holotype: Russia, Magadan Reg., Tenkinsky Dist., Madaun, Salix arbutifolia, 14 Aug. 1995, Corfixen (C 31369, studied).

Basidiocarps resupinate, appearing as small, cream-colored, soft, floccose patches, later fusing together and reaching up to 1 cm diam, adnate, densely floccose, 0.1–0.2 mm thick; margin arachnoid. Hyphae thin-walled, easily collapsing, some twisted, (3.5–)4.1–7.3(–7.8) μm diam (n = 60/3). Basidia 100–150 × (9.4–)9.5–13.4(–15.3) μm (n = 40/2); probasidia narrowly saccate to clavate, often tortuous or constricted, many bi- or trifurcate, thin- or slightly thick-walled, 42.5–76 × 10.5–15.5 μm. Basidiospores ovoid to broadly ellipsoid, (14.6–)15.4–23.6(–26.8) × (10.2–)10.4–15.7(–17.0) μm (n = 110/4), L = 17.15–19.66, W = 12.44–13.30, Q’ = (1.1–)1.2–1.7(–1.8), Q = 1.36–1.53.

Distribution and ecology: Europe (Austria, France, Italy, Switzerland), Asia (Russian Far East), North America (US – Washington); still attached dry branches of shrub-like alders (Alnus viridis group, one record on Salix arbutifolia).

Notes: Further phylogenetic studies with other genes should clarify the taxonomic status of this ‘form’. Morphologically, it is very distinctive if compared with S. farinaceum.

Saccosoma floccosum V. Malysheva & Spirin, sp. nov. MycoBank MB825615. Fig. 18.

Etymology: Floccosus (Lat., adj.) – floccose.

Holotype: Russia, Lipetsk Reg., Krasnoe Dist., Olenii Nat. Park, Quercus robur (fallen branches), 30 Sep. 2016, Volobuev (LE 313308, isotype H).

Basidiocarps very soft, floccose, easily detaching from the substrate, cream-colored, covering a few cm, up to 0.2 mm thick; margin arachnoid. Subicular hyphae differentiated, sparse, slightly thick-walled, 5–7 μm diam. Subhymenial hyphae thin-walled, easily collapsing, (3.0–) 3.2–5.0 (–5.1) μm diam (n = 40/2). Basidia 54–79 × (6.0–)6.1–7.4(–7.8) μm (n = 26/2); probasidia saccate to clavate, not furcate, thin-walled, 13–30 × 7–10 μm. Basidiospores narrowly lacrymoid to subfusiform, (8.8–)9.0–13.8(–14.2) × (5.1–) 5.2–8.0(–8.2) μm (n = 60/2), L = 10.47–11.97, W = 6.64–6.71, Q’ = (1.4–)1.5–2.0(–2.1), Q = 1.56–1.81.

Distribution and ecology: Europe (Russia); thin fallen branches of conifers (Picea) and deciduous trees (Quercus).

Notes: Soft, detaching basidiocarps, as well as narrow basidiospores help in identification of this species.

Saccosoma globisporum (S.H. Wu & Z.C. Chen) Spirin, comb. nov. MycoBank MB825616.

Basionym: Helicogloea globispora S.H. Wu & Z.C. Chen, Karstenia 45: 195. 2000.

Notes: Saccosoma globisporum was described from Taiwan (Wu & Chen 2000). According to the description, it is most similar to S. sphaerosporum and differs from the latter species in having larger basidiospores.

Saccosoma medium (Spirin et al.) Spirin, comb. nov. MycoBank MB825617.

Basionym: Saccoblastia media Spirin et al., Synopsis Fungorum 33: 28. 2015. Holotype: St. Helena, Scotland Research Station, on hardwood, 3 Feb. 2014 Ryvarden 49436 (K, isotype – H).

Notes: This species was described in Spirin et al. (2015). Saccosoma medium is the only species of the genus having cystidia although they are infrequent and rather poorly differentiated.

Saccosoma sphaerosporum (Möller) Spirin, comb. nov. MycoBank MB825618.

Basionym: Saccoblastia sphaerospora Möller, Botanische Mittheilungen aus den Tropen 8: 20. 1895.

Neotype: Costa Rica, Puntarenas, Coto Brus, Las Alturas, 2 Dec. 1996, Kisimova-Horovitz 222-vi (USJ 55489, not studied) (selected and illustrated by Kisimova-Horovitz et al. 2000: 551).

Basidiocarps effused, corticioid, cream-colored, rather dense, covering a few cm, up to 0.3 mm thick; margin pruinose. Hyphae slightly to distinctly thick-walled, 3–5 μm diam. Basidia 36–62 × 4.4–5.4 μm (n = 20/2); probasidia saccate, thin-walled, 13.5–20 × 6–8 μm. Basidiospores subglobose to globose, (5.3–)5.8–7.2(–7.7) × (5.0–)5.2–6.7(–7.4) μm (n = 60/3), L = 6.32–6.67, W = 5.85–6.27, Q = 1.07–1.08.

Distribution and ecology: South and North America (Brazil, Costa Rica, Mexico, USA – Florida); still attached or fallen, mostly corticated branches of deciduous trees.

Notes: This species is described, illustrated and discussed in detail as Saccoblastia sphaerospora by Kisimova-Horovitz et al. (2000). The latter authors reported basidiospores of the Costa Rican specimens as globose, 8–10 μm diam, whereas they are distinctly smaller in collections from Mexico and Florida studied by us. These differences may indicate that S. sphaerosporum is a species complex.

ACKNOWLEDGEMENTS

REFERENCES