Hebeloma fusisporum (Photo: I.O. Ibarguren)

Taxonomy

Types: GERMANY: Free State of Saxony, Bleichteiche, Herrnhut (approx. 51.0171°N, 14.7313°E, alt. approx. 330 m a.s.l.) on boggy soil in willow thicket under Alnus glutinosa and Salix sp., 25 Sep. 1976, G. Zschieschang, det: F. Gröger (Holotype. herbarium acc. no. GLM GL11251, HJB1000021).

Heterotypic synonyms:

• Hebeloma cremeopallidum (Esteve-Rav. & Heykoop) Esteve-Rav. & Heykoop, Mycotaxon 61: 212 (1997)
• Hebeloma vaccinum var. cremeopallidum Esteve-Rav. & Heykoop, Cryptogamie Mycologie 11 (1): 24 (1990)

• arrow_drop_downarrow_drop_upEtymology
  From fusiformis– swollen at middle and tapering to each end like a spindle, narrowly ellipsoid, and sporus– spored, to describe the shape of the spores.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  In Lusatia superiore prope pagum “Herrnhut” ad lacus “die Bleichteiche” dictos, in saliceto paludoso cum Alnis glutinosis disperses, valde gregarium. Typus: 25.9.1976, Zschieschang (Holotypus in GLM). Velo nullo. Pileo 1,2-2,2 cm lato, obtuse conico, convexo vel fere semiorbiculari, margine in iuventute anguste inflexo, serius plerumque acuto, admodum unicolore, albo usque pallide cremeo, raro flavido-tincto, nonnumquam paulo subfusco-maculato, leve, plerumque opaco, semper sicco, cutis marginem versus nonnihil fibroso-rimosa. Lamellis subconfertis, L 33-48, l 1-3 (5-7), angustis, usque 4 mm latis, +/- ventricosis, adnexis vel anguste adnatis, rarius circum stipitem sinuatis, in iuventute pallide quasi coffea cum lacte mixta coloratis, senescentibus obscurius griseo-fuscis et carneo-tinctis, cum acie albida et denticulata. Stipite 2,2-4,5 x 0.2-0,45 cm, aequali vel basim versus paulo angustato, haud fusiformi, sub strato albo, fibroso-squamatim dirumpente albo usque cremeo-albo, cum fibrillis brunnescentibus, in summa parte minutissime albofloccoso, e basi aquoso-flaccido, primum sordide fusco, deinde fere nigro. Carne pilei alba, stipitis sicut extrinsecus colorata, sericeo-nitida, serius brunnescente. Odore gravi, Hebeloma sacchariolens in mentem revocante, sapore leviter amarescente. Carposomate in statu sicco dura et fragili. Basidiis angustis, 32-40 x 7,5-9 (10) μm, cum sterigmatibus 5-6 x 2,5 μm. Sporis angustis, plerumque fusiformibus, ad apicem rara papillatis, verruculosis, flavis 12-15,5 (16,5) x 6,2-7,5 μm (Q 1,95-2,45), plerumque plus quam duplo longioribus quam latioribus. Exosporio saepe clare segregato. Cheilocystidiis filiformi-cylindricis vel claviformibus, saepius in dimidio vel ad basim paulo tumidis, nonnumquam curvatis, saepe septatis, fibulatis, 50-80 x 8-11 μm. Caulocystidiis ad apicem stipitis crebris, cheilocystidiis similibus.

• arrow_drop_downarrow_drop_upEnglish translation
  In the upper Lausitz region near Herrnhut, at the lake “die Bleichteiche”, in marshy Salix forest with Alnus glutinosus in large groups. Veil absent. Pileus 1.2–2.2 cm broad, obtusely conical, convex or indistinctly umbonate, with narrowly inflexed margin when young, later very frequently acute, entirely unicoloured, white to pale cream, rarely with a yellow tinge, sometimes weakly brownish spotted, glabrous, frequently opaque, always dry, epicutis near margin somewhat fibrous-rimose. Lamellae subcrowded, L 33–48, l 1–3 (5–7), narrow, up to 4 mm broad, more or less ventricose, adnexed or narrowly adnate, rarely emarginate, pale milky-coffee when young, later greyish brown and flesh-coloured with white, denticulate edge. Stipe 2.2–4.5 × 0.2–0.45 cm, equal or somewhat narrowed at base, not fusiform, with whitish to cream-coloured, disrupted fibrillose-squamulose covering on a whitish background, fibrils turning brown with age, in upper part minutely white-floccose, with watery, weak basal part, which is sordid brown at first, later turning blackish. Context white in pileus, in outer part of stipe coloured, silky shiny, later turning brown. Smell heavy, reminiscent of that of Hebeloma sacchariolens, taste slightly bitter. Basidiomes in dry state hard and fragile. Basidia narrow, 32–40 × 7.5–9 (10) μm with sterigmata 5–6 × 2.5 μm. Spores narrow, frequently fusiform, rarely papillate at apex, warted, yellow, 12–15.5 (16.5) × 6.2–7.5 μm (Q 1.95–2.45), frequently more than two times longer than wide. Perispore often distinctly loosening. Cheilocystidia filiform-cylindrical to clavate, often slightly swollen in the middle or at base, sometimes curved, often septate, clamped, 50–80 × 8–11 μm. Caulocystidia abundant at apex of stipe, similar to cheilocystidia.

Description

Description of Hebeloma fusisporum based on 37 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (7) 10–26 (60) mm diameter; shape often convex, occasionally umbonate, rarely broadly umbonate or strongly umbonate; characters rarely spotting, hygrophanous, rimulose, tomentose or remains of universal veil; margin characters usually involute, rarely reflexed; viscosity tacky when moist; colour variation unicolour; colour at centre often cream, rarely pale cream, honey, warm buff or pale yellow.

  Lamellae: attachment often emarginate, occasionally adnate, adnexed or free; maximum depth 2–6 mm; number of complete lamellae 23–52; presence of tears often absent, occasionally visible with naked eye, rarely visible with x10 lens; white fimbriate edge often absent, occasionally present or weak.

  Cortina presence: no.

  Stipe: (10) 18–48 (100) x 2–4 (8) {median} x 2–5 (7) {basal} mm; stipe Q 5.0–17.5; base shape often cylindrical, occasionally clavate, rarely tapering; floccosity occasionally fibrillose or none, rarely fibrous, floccose at apex, pruinose at apex, tomentose or velute; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior usually hollow, often stuffed; stipe flesh discolouring often yes, rarely no or weak; slenderness measure 10.1–55.0; smell sacchariolentia, often sweet, rarely cocoa; taste often bitter or weakly bitter where recorded.

  Spore deposit colour: often greyish brown or umber.

  Exsiccata characters: occasionally pileus blackening or stipe blackening, rarely lamellae blackening, dark or hard.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape usually fusoid, often amygdaloid, rarely limoniform; colour in microscope often brown, rarely grey yellow or yellow brown; guttules often yes, occasionally no. papilla often weak, occasionally no; Spore Code: O3 (O4); P2 P3; D3 D4.

  Basidia: (27) 28–42 (44) x 6–9 μm; ave. Q 3.4–5.4; spore arrangement 4 spored;

  Cheilocystidia: main shape often gently clavate, occasionally clavate, cylindrical or clavate-stipitate, rarely clavate-lageniform or clavate-ventricose, balloon-shaped, tapering, utriform or ventricose; special features observed occasionally septa, clamped septa or irregular, rarely many collapsed in exsiccata, apical thickening, bifurcate, median thickening, rostrate or short; cheilocystidia ratios: A/M = 1.17–1.85; A/B = 1.33–2.32; B/M = 0.71–1.14.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 50 μm; ixocutis hyphae width up to 7 μm; ixocutis hyphae encrustation often yes, occasionally no; shape of trama elements beneath subcutis ellipsoid or thickly sausage-shaped up to 30 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 100 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma fusisporum's preferred habitat appears to be willow thicket with boggy soil. Where only one possible associate was recorded, the most commonly recorded associate was Salix (86.4%) but Betula (4.5%), Alnus (4.5%) and Corylus (4.5%) were also recorded. In these cases the most commonly recorded families were Salicaceae (88.0%) and Betulaceae (12.0%). We have additional records where Populus (10.0%), Picea (6.7%) and Quercus (3.3%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Salicaceae (86.7%), Betulaceae (23.3%) and Pinaceae (6.7%) The growth habit of our collections was usually scattered and occasionally solitary.

  According to our current collections, the species is found only in Europe. On the continent, collections has been found in the WWF biomes The World Wildlife Fund (WWF) have divided the world into 867 terrestrial ecoregions. The ecoregion here is estimated by mapping from the GPS coordinates of the collection using data made available by Dinerstein et al (2017). Use this webtool to explore the ecoregions visually or see a full list of current ecoregions on Wikipedia. temperate broadleaf & mixed forests (73.0%) and mediterranean forests, woodlands & scrub (10.8%), specifically including the ecoregions: Celtic broadleaf forests (21.6%), European Atlantic mixed forests (13.5%), Iberian conifer forests (10.8%) and Sarmatic mixed forests (10.8%). From collector information, it appears collections have been found in the 1.4 Forest – Temperate (62.5%), 5.4 Wetlands (inland) – Bogs, marshes, swamps, fens, peatlands (16.7%) and 5.3 Wetlands (inland) – Shrub dominated wetlands (12.5%) IUCN habitats We map from the collector's description of the habitat to the International Union for Conservation of Nature (IUCN)'s definition using a standardised set of rules. Please see this page for a full list of IUCN habitats.. Within Europe we have records from the North (Norway, Scotland, England, Denmark, Isle Of Man and Wales), the Southwest (Spain and France) and the Centre (Belgium and Germany). Specimens have been collected from 40.7°N to 59.6°N.

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma fusisporum is closely related to H. ischnostylum. In the analyses of all genes tested the two species form a well supported clade. Not all of the tested genes separate the two taxa. In particular the ITS does not separate between them, whereas both of the mitSSU regions V6 and V9 do retrieve species clusters corresponding to the morphological species clusters. Although H. fusisporum does only receive bootstrap support in the V9 result, its sister clade, H. ischnostylum does, in both the V6 and V9. There is not sufficient data for Tef1a and RPB2 to see patterns emerging, but there are indications that RPB2 may not separate the two taxa, either. We obtained the ITS from the type of H. vaccinum var. cremeopallidum which supports the synonymization with this species. We are not aware of any ITS sequences published that are likely to belong to either H. fusisporum or H. ischnostylum.

• arrow_drop_downarrow_drop_upCommentary
  The smell associated with Hebeloma fusisporum immediately places it in H. sect. Sacchariolentia. The spore width, on average less then than 7 μm, means it can only be H. sacchariolens, H. ischnostylum or H. fusisporum. Hebeloma fusisporum has fusoid spores (Q > 1.8) and a pileus colour that is always white to ivory (other than through ageing); H. sacchariolens has average spore Q less than 1.8 and is usually two-coloured with brownish tones in the centre. With regard to H. fusisporum and H. ischnostylum, for a long time we believed this to be one species with a large spore range in size. Since ITS never showed up any significant difference, we never questioned this until our molecular studies of other loci showed there to be a difference, and it was then immediately apparent that there were significant morphological differences. Hebeloma fusisporum and H. ischnostylum can be separated in various ways. The easiest way is on the spore size, where H. fusisporum has spores on average longer than 12 μm, while H. ischnostylum has spores of maximum average length at most 12 μm. The spores of H. fusisporum are almost always wider, the basidiomes are generally more slender and the epicutis is thinner (range 25–50 μm as opposed to 120–185 μm for H. ischnostylum). We should mention the difficulty in measuring the spores (particularly the width) of these taxa; with the perispore strongly loosening in many spores it is easy to overestimate the width of the spores by failing to exclude the loosening perispore from the measurement. Hebeloma fusisporum can occasionally have a tomentose or cracking pileus, which leads to confusion with H. odoratissimum (and H. ischnostylum), but these taxa can be readily separated on both macroscopic and microscopic characters. For H. fusisporum, as for H. ischnostylum, the tomentum rarely persists and disappears with age. Hebeloma fusisporum together with H. ischnostylum are the only members of H. sect. Sacchariolentia that often have drops on the lamella edge; these two species also have the most defined cheilocystidia of any taxon within this section and they are usually easy to find. While the lamella edge is not completely sterile, it does appear to have sterile areas along its edge where the cheilocystidia are clearly packed together.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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