Hebeloma radicosum (Photo: L. Ballester)

Taxonomy

Basionym:
Agaricus radicosus Bull., Herb. Fr.: 160 (1784)

Types: Bulliard, Herb. Fr.: 115 (1784) tab. 160, lectotype (icon) designated by Beker et al., Hebeloma (Fr.) P. Kumm.: (2016) page 405 (MBT203423) FRANCE: Ariege, Ste Croix-Volve (43.1125°N, 1.1644°E, alt. approx. 360 m a.s.l.) on litter in mixed woodland under Castanea sp., 27 Sep. 2007, J. Malaval (Epitype. herbarium acc. no. BR 5020184113490, HJB12099). Epitype designated by Beker et al., Hebeloma (Fr.) P. Kumm.: (2016) page 405 (MBT203428).

• arrow_drop_downarrow_drop_upType notes
  The icon depicts a collection from France: sine loc.

Homotypic synonyms:

• Agaricus radicatus Pers., Synopsis Methodica Fungorum (Gottingen): 266 (1801)
• Pholiota radicosa (Bull.) P. Kumm. ., Der Führer in die Pilzkunde: 84 (1871)
• Dryophila radicosa (Bull.) Quél. ., Enchiridion Fungorum in Europa Media et Praesertim in Gallia Vigentium: 67 (1886)
• Myxocybe radicosa (Bull.) Fayod ., Prodrome d'une histoire naturelle des agaricinés 9: 361 (1889)
• Roumeguerites radicosus (Bull.) Locq., Flore Mycologique Vol III - Text. Cortinariales A: 146 (1979) ["1977"]

• arrow_drop_downarrow_drop_upEtymology
  From radicosus– having a root.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  L’Agaric Radiqueux. Agaricus radicosus. On trouve dans les bois ce champignon en Septembre et Octobre … dans l’état de jeunesse il a la forme d’un œuf, à mesure qu’il avance en âge son pédicule s’allonge au depend de son diamètre et le chapeau augmente de volume … un collet impropre et persistent tient les bords de chapeau lutés contre les parois du pédicule … la superficie du chapeau est seche, unie, tachée sans être peluchée, susceptible d’être pelée … sa chaire est ferme … ses feuillets sont nombreux, frangés; ceux qui sont entiers sont en petit nombre et n’ont pas de decurrence sur la pédicule … pédicule continu, toujours peluché jusqu’au collet et rémarquable par une racine très considerable qui s’enfonce profondément en terre et qui est toujours garnie de longues fibrilles radicales … on trouve souvent vers l’extremité inferieur de sa racine Fig A un ou plusieurs petits champignons de la même espèce. N.B. Les Figures A,B,C,D représentent ce champignons dans tout ses âges. On le voit coupé verticalement Fig D … la couleur des feuillets varie. Il a d’abord une saveur assez agréable: mais un instant après qu’on la mâché il laisse dans la bouche un goût âcre et détestable.

• arrow_drop_downarrow_drop_upEnglish translation
  The Rooting Agaric. Agaricus radicosus. We find this mushroom in the woods in September and October ... when young it has the form of an egg, as it ages its stipe elongates at the expense of its diameter and the pileus increases in volume ... an irregular collar persists at the edges of the pileus and hangs on the cuticle of the stipe ... the surface of the pileus is dry, smooth, stained but not floccose with a cuticle that may be peeled … the flesh is firm … its lamellae are numerous, with a fimbriate edge; complete lamellae are few and are not decurrent at the stipe … the stipe is floccose up to the collar and remarkable for its very considerable root that extends deep into the earth and that is always lined by long radial fibrils … often found towards the lower extremity of its root Fig A are one or more small mushrooms of the same species. NB Figures A, B, C, D] represent the mushroom at all its ages. In Fig D one can see a vertical section... the colour of the lamellae is variable. It has at first a rather pleasant taste: but a moment later after chewing it leaves a bitter and disgusting taste in the mouth.

Description

Description of Hebeloma radicosum based on 32 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (26) 34–94 (113) mm diameter; shape often convex, occasionally broadly umbonate, rarely umbonate; characters remains of universal veil, rarely spotting or scaly; margin characters usually smooth, occasionally involute; viscosity tacky when moist; colour variation usually unicolour, rarely two color; colour at centre occasionally pale cream, cream, ochraceous or dark pinkish buff, rarely pale yellow or buff-yellow.

  Lamellae: attachment usually emarginate, rarely adnate; maximum depth 3–10 mm; number of complete lamellae 58–130; presence of tears often absent, rarely visible with x10 lens or visible with naked eye; white fimbriate edge often present, occasionally weak.

  Cortina presence: usually no, rarely yes.

  Stipe: (35) 39–112 (115) x 6–21 (24) {median} x (6) 7–22 (25) {basal} mm; stipe Q 3.4–9.5; base shape often clavate, occasionally tapering, rarely bulbous or cylindrical; floccosity usually floccose, occasionally pruinose at apex, rarely fibrous; rooting yes; thick rhizoids at base absent;

  Context: Texture firm; stipe interior usually stuffed, occasionally hollow; stipe flesh discolouring often yes, rarely very strongly or no; slenderness measure 2.2–11.9; smell usually marzipan; taste mild where recorded.

  Spore deposit colour: often umber, occasionally brownish olive.

  Exsiccata characters: rarely dark or lamellae blackening.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid; colour in microscope often brown or yellow brown; guttules yes. papilla no; Spore Code: O3 (O4); P2 P3; D3 D4.

  Basidia: 23–32 (35) x 5–8 μm; ave. Q 3.3–4.3; spore arrangement 4 spored;

  Cheilocystidia: main shape clavate-lageniform or clavate-ventricose, often cylindrical, occasionally ventricose, gently clavate or clavate-stipitate, rarely capitate-stipitate, clavate or lageniform; special features observed often irregular, occasionally clamped septa, geniculate or septa, rarely branching, rostrate, short, bifurcate or sinuate; cheilocystidia ratios: A/M = 1.20–1.92; A/B = 0.75–1.41; B/M = 1.27–1.68.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 400 μm; ixocutis hyphae width up to 5 μm; ixocutis hyphae encrustation often yes, occasionally no; shape of trama elements beneath subcutis ellipsoid, often isodiametric, occasionally cylindrical, oblong or thickly sausage-shaped up to 20 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma radicosum's preferred habitat appears to be mixed woodland or deciduous woodland with decomposed litter. Where only one possible associate was recorded, the most commonly recorded associate was Fagus (56.2%) but Quercus (12.5%), Carpinus (6.2%), Betula (6.2%), Castanea (6.2%), Salix (6.2%) and Pinus (6.2%) were also recorded. In these cases the most commonly recorded families were Fagaceae (75.0%), Betulaceae (10.0%) and Pinaceae (10.0%). We have additional records where Corylus (11.1%), Picea (11.1%), Abies (11.1%) and Alnus (7.4%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Fagaceae (77.8%), Betulaceae (22.2%), Pinaceae (22.2%) and Salicaceae (7.4%) The growth habit of our collections was often solitary, occasionally scattered and rarely caespitose.

  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 (76.7%) and temperate conifer forests (13.3%), specifically including the ecoregions: Western European broadleaf forests (20.0%), European Atlantic mixed forests (13.3%) and Cantabrian mixed forests (13.3%). 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 Centre (Germany, Belgium, Poland and Czech Republic), the Southwest (Spain and France), the North (England, Scotland and Norway) and the Southeast (Italy). Specimens have been collected from 39.4°N to 59.4°N.

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma radicosum forms a monophylum in all single locus analyses and we have not observed any intraspecific variation that could point towards undetected species within Europe. The ITS of the epitype of the species has been obtained and supports our conclusions. The isolated position of H. radicosum within the genus implies that the species can easily be identified by molecular data within the context of European species. In Eberhardt et al. (2020b), it was shown that H. sagarae, currently only known fron Japan, is a sister species of H. radicosum, and are the only know species of H. sect. Myxocybe.

• arrow_drop_downarrow_drop_upCommentary
  Within Europe Hebeloma radicosum seems phylogenetically, and even morphologically, somewhat isolated. With its membranous ring, the distinctly rooting stipe and the marzipan-like smell this species is usually instantly recognisable in the field. For this reason, as mentioned above, we rarely receive collections of this taxon from forayers and consequently we have less information about its distribution than we would like. Much has been written about its possible association with nests and latrines of various animals. There appears little doubt that it favours nitrogen enriched soils. Other species described from Australia and Japan also appear to favour such habitats and we await further study to see how closely related these taxa are. Hebeloma radicosum has a consistent appearance with its often spotted and scaly glutinous pileus (particularly in humid conditions) and stipe with annular ring and often concentric scales down to the base of the stipe. The smell is also usually distinct and fairly strong. Microscopically, it has cheilocystidia that are less consistently uniformly cylindrical than members of H. sect. Scabrispora; indeed they are very irregular and can vary from cylindrical to ventricose or clavate-stipitate and almost everything in-between! Bulliard did not select any material as holotype for this taxon. However his illustration serves as an excellent lectotype. In order to ensure a precise application of the name of this taxon, we have designated an epitype; we have chosen a collection from France.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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