Hebeloma sordescens (Photo: J. Vesterholt)

Taxonomy

Types: DENMARK: NEZ, Kongelunden,Amager UTM UB 47,61 TBU 46 (approx. 55.57°N, 12.57°E, alt. approx. 0 m a.s.l.) on soil under Betula sp., Corylus sp. and Quercus sp., 29 Sep. 1984, J. Vesterholt (84-1371) (Holotype. herbarium acc. no. C JV-84-1371, HJB1000129).

• arrow_drop_downarrow_drop_upEtymology
  From sordidus– dirty-looking, dingy, soiled. Vesterholt says: “the epithet ‘sordescens’ refers to the rather strong degree of discolouring observed on specimens dried under normal conditions”.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  Pileus primum hemiphaericus, deinde minus convexus vel applanatus, 20–50 mm latus, supra viscidulus, cinnamomeus vel aurantio-fuscus, ad marginem laetior vel plane albus. Velum valde fugax. Lamellae emarginatae. Stipes 25–90 x 4–8 mm magnus, ad basem obclavatus ad 13 mm crassus. Sporae amygdaloides vel sublimoniformes, 10–11 x 5–6.5 μm magnae, asperae, manifesto dextrinoides. Cheilocystidia cylindrica, prope bases dilatata. Habitat in terra sub Betula, Quercu, Corylo.

• arrow_drop_downarrow_drop_upEnglish translation
  Pileus hemispherical at first then convex to applanate, 20–50 mm broad, surface slightly viscid, cinnamon to orange-brown, paler at margin to almost white. Velum very ephemerous. Lamellae emarginate. Stipe 25–90 × 4–8 mm, clavate towards base, up to 13 mm thick. Spores amygdaloid and sublimoniform, 10–11 × 5–6.5 μm, roughened, distinctly dextrinoid. Cheilocystidia cylindrical, widened towards base. Terrestrial under Betula, Quercus and Corylus.

Description

Description of Hebeloma sordescens based on 43 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (15) 19–38 (50) mm diameter; shape often convex, rarely umbonate or broadly umbonate; characters occasionally hygrophanous or remains of universal veil; margin characters smooth; viscosity tacky when moist; colour variation usually two color, rarely unicolour; colour at centre often yellowish brown, occasionally cinnamon, sepia or cream.

  Lamellae: attachment emarginate; maximum depth 1–6 mm; number of complete lamellae 42–60; presence of tears absent; white fimbriate edge often present, occasionally weak or very strong.

  Cortina presence: yes.

  Stipe: (23) 24–64 (90) x 3–6 (8) {median} x 3–11 (13) {basal} mm; stipe Q 4.3–15.0; base shape often clavate, occasionally cylindrical, rarely subbulbous; floccosity usually fibrillose, occasionally floccose or floccose at apex; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior often hollow, occasionally stuffed or superior wick; stipe flesh discolouring occasionally yes or very strongly, rarely no; slenderness measure 4.6–25.4; smell often raphanoid, occasionally cocoa; taste bitter or raphanoid where recorded.

  Spore deposit colour: often brownish olive, occasionally umber or greyish brown.

  Exsiccata characters: often pileus blackening, occasionally stipe blackening, rarely fragile or hard.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid, often limoniform, rarely fusoid; colour in microscope occasionally brown or brown yellow, rarely brown pale, yellow or yellow brown; guttules often no, occasionally weak, rarely yes. papilla occasionally yes or very strongly, rarely weak; Spore Code: O2; P0 P1; D3.

  Basidia: 20–33 (35) x 6–9 μm; ave. Q 3.1–4.1; spore arrangement Not recorded;

  Cheilocystidia: main shape lageniform, usually ventricose, occasionally cylindrical, rarely filiform, gently clavate or tapering; special features observed often septa, occasionally clamped septa or slender, rarely apical thickening or geniculate; cheilocystidia ratios: A/M = 0.83–1.16; A/B = 0.49–0.70; B/M = 1.59–2.27.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 175 μm; ixocutis hyphae width up to 7 μm; ixocutis hyphae encrustation yes; shape of trama elements beneath subcutis often angular or oblong, occasionally isodiametric.

  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 sordescens's preferred habitat appears to be coniferous woodland or deciduous woodland. Where only one possible associate was recorded, the most commonly recorded associate was Picea (44.4%) but Betula (33.3%), Corylus (5.6%), Fagus (5.6%), Alnus (5.6%) and Populus (5.6%) were also recorded. In these cases the most commonly recorded families were Betulaceae (38.1%), Pinaceae (38.1%), Ericaceae (9.5%) and Fagaceae (9.5%). We have additional records where Quercus (21.9%), Carpinus (6.2%) and Abies (6.2%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Betulaceae (53.1%), Pinaceae (43.8%), Fagaceae (28.1%) and Ericaceae (6.2%) The growth habit of our collections was usually scattered and occasionally solitary.

  According to our current collections, the species is predominantly found in Europe (97.5%) but also found in Temperate Asia (2.5%). 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 (69.4%) and unknown biome (13.9%), specifically including the ecoregions: Celtic broadleaf forests (16.7%), Sarmatic mixed forests (13.9%), Western European broadleaf forests (13.9%) and Unknown region (13.9%). From collector information, it appears collections have been found only in the 1.4 Forest – Temperate IUCN habitat 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, Denmark, Sweden, Iceland and England), the Centre (Germany, Poland and Austria) and the Southwest (France and Italy). Specimens have been collected from 42.9°N to 69.2°N.

  Within Temperate Asia all our records are from Caucasus (Adygea).

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma sordescens is monophyletic and receives good bootstrap support in the single locus results of all nuclear loci, including ITS, but is paraphyletic as most species in H. sect. Hebeloma in the results of the mitochondrial loci. The species receives high bootstrap support based on the dataset of five loci concatenated. We were able to amplify the ITS from the type of H. sordescens which clearly supports our concept of this species. We are not aware of any sequences published from Europe or outside Europe that are likely to belong to this species.

• arrow_drop_downarrow_drop_upCommentary
  With the persistent presence of a cortina and the lageniform or ventricose cheilocystidia, this taxon clearly belongs in H. section Hebeloma. Within this section, it can be differentiated on the basis of the amygdaloid and limoniform spores, distinctly to rather strongly dextrinoid, the number of full length lamellae always at least 45, the boreal and the non-arctic, non-alpine habitat. The separation from H. clavulipes and H. monticola, the two closest taxa, is based on the larger number of full length lamellae (L greater than 45), the narrow cheilocystidium apex (at most 5 μm) and the exsiccata, which almost always discolours strongly to dark brown or black. Vesterholt (1989) introduced this epithet as a new name for H. testaceum sensu Lange (1938a). Agaricus testaceus Fr. (1838), non A. testaceus Scop., was introduced by Fries (1836–1838), in error, as a superfluous name change for A. subtestaceus Batsch. Batsch’s species (Batsch (1789), plate 198), from mountainous pine forests, is probably a species from H. sect. Velutipes. Lange’s species is a veiled species with stipe becoming “flushed with dingy brownish from base up”. It is described from moist places with Betula. We do believe that Hebeloma sordescens is the same taxon as Lange did have in mind. Striking in this species is the usual (but not always consistent) blackening of the pileus and stipe on the dryer, which often makes the determination very straightforward.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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