Hebeloma leucosarx (Photo: L. Davies)

Taxonomy

Types: SCOTLAND: Loch Loy (approx. 57.58°N, 3.85°W, alt. approx. 10 m a.s.l.) in boreal, mixed woodland under Betula sp. and Salix sp., 25 Sep. 1955, P.D. Orton (Lectotype. herbarium acc. no. K(M)52712, HJB1000002; Isotype. herbarium acc. no. E00076310, HJB1000093). Lectotype designated by Grilli, Micol. Veg. Medit. 22 (2): (2007) page 148.

• arrow_drop_downarrow_drop_upType notes
  The holotype originally designated was a mixed collection.

Homotypic synonyms:

• Hebelomatis leucosarx (P.D. Orton) Locq., Flore Mycologique Vol III - Text. Cortinariales A: 146 (1979) ["1977"]

• arrow_drop_downarrow_drop_upEtymology
  From leuco– (Greek) white and sarc– (Greek) flesh, so white-fleshed.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  Pileus 22–58 mm., e convexo expansus vulgo late obscure umbonatus, senectute planus orbicularis vel ad marginem undulato-lobatus, sordide incarnato-ochraceus vel pallide fulvo-ochraceus, vulgo ad marginem pallidiore vel ad discum obcuriore coloratus, jove pluvio viscidus, jove sicco glaber, ad marginem primo eleganter albo-tomentosus mox glabrescens. Lamellae adnatae, +/- emarginatae, pallide argillaceae vel sordide incarnato-ochraceae (colorem marginis pilei accedentes) postremo argillaceo-luteolo brunneae, confertae, L 40–66 l (1)3(7), ad aciem juventute conspicue albo-floccosae, jove pluvio plorantes. Stipes 25–90 x 3.5–11 mm (infra 5–18), aequalis vel clavato-bulbosus, albus dein praecipue ad basim pallide sordido-ochraceus, primo totus albo-pruinosus dein infra albo-sericeo striatus, e farcto cavus. Caro alba, in cortice stipitis sordide ochraceotincta, intus solum vulnerato leviter decolorans. Odor fortis, raphanoideus. Sapor mitis dein acris. Sporae limoniformibus, punctatae, 9–12(14) x 5,5–6,5 μm. Basidia 4-sporigera 24–30 x 8–9 μm. Cystidia aciei lamellarum +/- clavata 40–60 x 4–6 μm ad apicem (5)7–13 μm; cellulae similis ad apicem stipitis adsunt. Gregarius, ad terram humidam in salicetis betuletisque. A carne plerumque alba, acie lamellarum plorante, margine pilei primo albotomentoso et coloribus insignis.

• arrow_drop_downarrow_drop_upEnglish translation
  Pileus 22–58 mm broad, convex then expanding, often broadly, obtusely umbonate, finally plane and orbicular, or with wavy-undulating margin, sordid pinkish-ochraceous or pale reddish ochre, often with pale margin and darker centre, viscid when moist, smooth when dry, at margin when young with fine white tomentum soon glabrous. Lamellae adnate, +/- emarginate, pale clay then clay-buff or pale pinkish buff (almost colour of margin of pileus) finally clay-buff, crowded L 40–66, l (1) 3 (7),with white flocculose edge conspicuously so when young, weeping in wet weather. Stipe 25–90 × 3.5–11 mm (at base 5–18), equal or clavate-bulbous, white then discoloured pale dirty ochraceous especially in lower part, at first entirely white pruinose then white silky striate in lower part, stuffed then hollow. Context white, tinged ochraceous in flesh of stipe, discolouring slightly in centre only when bruised. Smell strong, raphanoid. Taste mild then bitter. Spores limoniform, punctate, 9–12 (14) × 5.5–6.5 μm. Basidia four-spored 24–30 × 8–9 μm. Marginal cells +/- clavate, 40–60 × 4–6 μm at apex (5) 7–13 μm.; similar cells occur at apex of stipe. Gregarious on damp soil in mixed forest of Salix and Betula. Recognized by the flesh for the most part white, weeping lamellae edge, tomentose margin of young pilei and the unremarkable colour.

Description

Description of Hebeloma leucosarx based on 195 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (12) 16–51 (90) mm diameter; shape occasionally umbonate, convex or broadly umbonate, rarely weakly umbonate or strongly umbonate; characters rarely hygrophanous, rugulose, spotting or remains of universal veil; margin characters usually smooth, rarely involute, appendiculate, eroded or wavy; viscosity tacky when moist; colour variation often two color, occasionally unicolour; colour at centre occasionally yellowish brown or ochraceous, rarely umber, cinnamon, clay-buff, brick, dark pinkish buff, warm buff, orange-brown, dark brick, cream, buff-yellow or honey.

  Lamellae: attachment usually emarginate, occasionally adnate, rarely decurrent tooth or adnexed; maximum depth 2–9 mm; number of complete lamellae 50–70; presence of tears often visible with naked eye, occasionally absent, rarely visible with x10 lens; white fimbriate edge usually present, rarely weak or very strong.

  Cortina presence: no.

  Stipe: (19) 28–70 (110) x 3–7 (14) {median} x (3) 5–15 (23) {basal} mm; stipe Q 4.2–17.5; base shape often clavate or bulbous, occasionally cylindrical, rarely subbulbous; floccosity occasionally pruinose, floccose or velute, rarely pruinose at apex, fibrillose, floccose at apex, weakly floccose, none or fibrous; rooting usually no, rarely yes; thick rhizoids at base usually absent, rarely present;

  Context: Texture firm; stipe interior usually hollow, often superior wick, rarely stuffed; stipe flesh discolouring variable occasionally weak; slenderness measure 5.3–36.3; smell often raphanoid, rarely odourless, strongly raphanoid, cocoa or weakly raphanoid; taste occasionally mild or raphanoid, rarely bitter or weakly bitter where recorded.

  Spore deposit colour: usually brownish olive, occasionally umber.

  Exsiccata characters: occasionally rich brown color or dark, rarely pileus blackening, fragile or stipe blackening.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid, occasionally limoniform; colour in microscope occasionally yellow brown, yellow or brown, rarely grey yellow or yellow pale; guttules usually yes, rarely no. papilla variable occasionally weak; Spore Code: (O1) O2 (O3); P0 (P1); (D2) D3.

  Basidia: 24–34 (35) x 6–9 (10) μm; ave. Q 3.0–4.1; spore arrangement 4 spored;

  Cheilocystidia: main shape gently clavate, often clavate-lageniform or clavate-ventricose, occasionally clavate-stipitate or clavate, rarely ventricose, capitate, lageniform, tapering or utriform; special features observed occasionally bifurcate, apical thickening, septa or geniculate, rarely median thickening, clamped septa, branching, solid or yellow contents; cheilocystidia ratios: A/M = 1.41–1.78; A/B = 1.15–2.14; B/M = 0.76–1.33.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 200 μm; ixocutis hyphae width up to 5 μm; ixocutis hyphae encrustation often yes, occasionally no; shape of trama elements beneath subcutis often ellipsoid, polygonal or thickly sausage-shaped up to 21 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 200 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma leucosarx's preferred habitat appears to be mixed woodland. Where only one possible associate was recorded, the most commonly recorded associate was Betula (50.6%) but Picea (16.9%), Pinus (11.7%), Abies (6.5%), Fagus (5.2%), Quercus (2.6%), Tsuga (2.6%), Carpinus (1.3%), Alnus (1.3%) and Salix (1.3%) were also recorded. In these cases the most commonly recorded families were Betulaceae (51.2%), Pinaceae (40.2%) and Fagaceae (7.3%). We have additional records where Corylus (3.1%) and Populus (1.2%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Betulaceae (69.3%), Pinaceae (56.4%), Fagaceae (21.5%) and Salicaceae (14.1%) The growth habit of our collections was often scattered, occasionally solitary and rarely gregarious or caespitose.

  According to our current data, the species is found on multiple continents with collections found in Europe (61.0%), Northern America (36.8%), Temperate Asia (1.6%) and Africa (0.5%). On these continents, 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 (60.8%), boreal forests/taiga (16.9%) and temperate conifer forests (12.7%), specifically including the ecoregions: European Atlantic mixed forests (13.2%). From collector information, it appears collections have been found in the 1.4 Forest – Temperate (45.6%) and 1.1 Forest – Boreal (38.8%) 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 (Scotland, Norway, England, Finland, Denmark, Sweden and Isle Of Man), the Centre (Poland, Belgium, Germany, Netherlands and Austria), the Southwest (France) and the Southeast (Italy). Specimens have been collected from 42.9°N to 69.9°N.

  Within Northern America we have records from Eastern Canada (Quebec and Newfoundland and Labrador), Subarctic America (Nunavut, Greenland and Alaska), Northeastern U.S.A. (New Jersey, Pennsylvania, Massachusetts, Ohio, Rhode Island and New Hampshire), Southeastern U.S.A. (North Carolina and Maryland), Western Canada (British Columbia), North-central U.S.A. (Wisconsin and Minnesota) and Northwestern U.S.A. (Washington).

  Within Temperate Asia we have records from Russian Far East (Tyumen and Kamchatka) and Siberia (Tyumen).

  Within Africa all our records are from Macaronesia (Spain).

• arrow_drop_downarrow_drop_upMolecular results
  Members of the velutipes-complex, namely H. leucosarx, H. velutipes and H. subconcolor, are molecularly very closely related in terms of sequence similarity; H. incarnatulum is only very similar in its ITS. The molecular diversity observed in H. velutipes (Aanen et al. 1999, see also under H. velutipes) also makes the molecular identification of H. leucosarx difficult. In spite of the great similarity, H. leucosarx forms a (unsupported) monophylum in the ITS topology. This is also reflected in the results of BLAST searches against our database, which normally retrieve the correct name. The single copy loci RPB2 and Tef1a are not suitable for identification; neither do the mitochondrial loci allow unambiguous species determination. This is one of the rare cases where concatenation of different loci does not improve species identification. We did obtain sequences from the material that was made lectotype of H. leucosarx (Grilli et al. 2016). Also the assignment of part of the non-lectotype material to H. lutense and thus to H. subsect. Crustuliniformia is supported by ITS data.

• arrow_drop_downarrow_drop_upCommentary
  With its gently clavate cheilocystidia, interspersed with some cheilocystidia that are clavate-lageniform or ventricose and the spores rather strongly dextrinoid, this taxon clearly belongs to H. sect. Velutipes. Within this section, the cheilocystidium ratio B/M being less than 1.35 and the spores rarely a combination of distinctly ornamented, perispore distinctly and strongly loosening and strongly dextrinoid (O3, P2.P3, D4), takes us to the velutipes-complex group and H. incarnatulum, H. leucosarx and H. velutipes. Macroscopically, H. leucosarx most strongly resembles H. incarnatulum and these two taxa have a similar preference for habitat, often in moss with conifers. They are also both relatively slender species. However, microscopically, the cheilocystidia of H. incarnatulum are far more slender and the average apex of the cheilocystidia never exceeds 6.5 μm. The average apex of the cheilocystidia in H. leucosarx ranges from 6.6–8.6 μm and is usually well over 7 μm. Microscopically, we have not found any way to separate H. leucosarx from H. velutipes, however, macroscopically, they are quite different. Hebeloma leucosarx is always distinctly umbonate, with a slender appearance and a dark coloured pileus. Hebeloma velutipes has a much paler pileus colour and a less slender appearance; it too can be quite distinctly umbonate. Also, the exsiccata of these two taxa is quite different: H. leucosarx is always a rich brown colour while H. velutipes has a distinctive pallid matt look to the pileus of dried material. We have little doubt that in the past H. leucosarx has been confused with both H. incarnatulum and H. velutipes. We believe that this species can often be determined in the field, the only possible confusion being with H. incarnatulum. Orton’s original material of this species was mixed. It constituted two taxa: that described here and H. lutense. It appears that his macroscopic description is more in line with H. lutense (although even here there are signs of both species) and his microscopic description fits better with this taxon. Grilli (2007), aware that the collection was mixed, selected as lectotype the portion of the original material that represents this taxon. At the time, never having seen an icon of the material, and hence based only on microscopic data, he believed it was conspecific with H. velutipes. Having generated an ITS sequence from the material, we were able to provide further evidence that this taxon is not conspecific with H. velutipes but represented a taxon with which we were familiar but for which we had no name.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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