Hebeloma excedens (Photo: L. Davies)

Taxonomy

Basionym:
Agaricus excedens Peck [as "Agaricus (Hebeloma) excedens"], Ann. Rep. N.Y. St. Mus. nat. Hist.: 68 (1872)

Types: UNITED STATES: New York: Saratoga, Saratoga county (approx. 43.0831°N, 73.7846°W, alt. approx. 100 m a.s.l.) on sandy soil in woodland under Pinus sp., Oct. 1870, C.H. Peck (Holotype. herbarium acc. no. NYS-F-001123, HJB1000268; Isotype. herbarium acc. no. WTU-F-039668, HJB1000352).

Heterotypic synonyms:

• Hebeloma agglutinatum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 163 (1983)
• Hebeloma bicoloratum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 166 (1983)
• Hebeloma brunneomaculatum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 52 (1983)
• Hebeloma ellipsoideosporium Hesler, Kew Bulletin 31 (3): 476 (1977)
• Hebeloma evensoniae A.H. Sm. & Mitchel, in Smith, Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 36 (1983)
• Hebeloma kauffmanii A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 56 (1983)
• Hebeloma luteobrunneum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 42 (1983)
• Hebeloma mesophaeum var. bifurcatum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 78 (1983)
• Hebeloma proximum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 173 (1983)
• Hebeloma pseudomesophaeum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 174 (1983)
• Hebeloma pumiloides A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 176 (1983)
• Hebeloma pumiloides var. sylvestre A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 177 (1983)
• Inocybe sterlingii Peck, Bull. Torrey bot. Club 33 (4): 217 (1906)
• Hebeloma sterlingii (Peck) Murrill, N. Amer. Fl. 10 (3): 217 (1917)
• Hebeloma urbanicola A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 181 (1983)
• Hebeloma vatricosoides (Peck) Murrill, N. Amer. Fl. 10 (3): 219 (1917)
• Inocybe vatricosoides Peck, Bull. N.Y. St. Mus.: 67 (1910)

Homotypic synonyms:

• Derminus excedens (Peck) Henn. [as "exsedens"], Hymenomycetineae: 243 (1898)

• arrow_drop_downarrow_drop_upEtymology
  From excedens (Latin), meaning ‘rising above, over-topping, exceeding’ to emphasize the pileus margin extending beyond the lamellae.

• arrow_drop_downarrow_drop_upDiagnosis
  Pileus thin, convex, gibbous, or broadly umbonate, pale alutaceous inclining to russet; lamellae rather broad, close, deeply emarginate, terminating before the margin, minutely eroded on the edge, pallid, then brownish; stem equal, solid, silky-fibrillose, colored like the pileus; spores subelliptical, 1/3500' [7.3 µm] long. Plant 2' [51 mm] high, pileus 1' broad [25 mm], stem 1''-2'' thick [2.5-5.1 mm]. Sandy soil about pine trees. Saratoga. October. Readily known by the thin margin extending beyond the lamellae. It has the taste and odor of radishes.

Description

Description of Hebeloma excedens based on 198 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (8) 17–42 (60) mm diameter; shape often convex, occasionally umbonate or broadly umbonate, rarely papillate, weakly umbonate, applanate or strongly umbonate; characters usually remains of universal veil, rarely hygrophanous, spotting or pubescent; margin characters occasionally involute, smooth, overhanging pileus or fibrillose, rarely appendiculate, reflexed, sulcate or wavy; viscosity tacky when moist; colour variation often two color, occasionally unicolour; colour at centre occasionally cinnamon or yellowish brown, rarely sepia, dark brick, brownish olive, ochraceous, umber, clay-buff, clay-red, orange-brown, pale pinkish buff or greyish buff.

  Lamellae: attachment often emarginate, occasionally adnate or adnexed, rarely decurrent tooth or free; maximum depth 3–7 mm; number of complete lamellae 32–53; presence of tears usually absent, rarely visible with naked eye; white fimbriate edge occasionally present, weak or absent, rarely very strong.

  Cortina presence: yes.

  Stipe: (15) 24–64 (100) x 2–6 (10) {median} x 2–6 (9) {basal} mm; stipe Q 3.8–22.0; base shape cylindrical, rarely tapering or clavate; floccosity fibrillose, occasionally pruinose at apex, rarely floccose or floccose at apex; rooting usually no, rarely yes; thick rhizoids at base absent;

  Context: Texture firm; stipe interior usually hollow, occasionally stuffed; stipe flesh discolouring often yes, occasionally no or weak, rarely very strongly; slenderness measure 2.3–48.5; smell occasionally raphanoid or odourless, rarely strongly raphanoid, weakly raphanoid, cocoa, earthy or fruit; taste occasionally raphanoid, none, mild or strongly raphanoid, rarely bitter or strongly bitter where recorded.

  Spore deposit colour: occasionally brownish olive, yellowish brown or clay-buff, rarely cinnamon.

  Exsiccata characters: Not recorded.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape ellipsoid, usually ovoid, rarely cylindrical; colour in microscope occasionally yellow pale, grey yellow, yellow or yellow brown, rarely brown pale or very pale; guttules often no, occasionally weak, rarely yes. papilla no; Spore Code: O1 (O2); P0; D0.

  Basidia: (16) 19–33 (36) x 5–9 μm; ave. Q 3.0–4.7; spore arrangement 4 spored;

  Cheilocystidia: main shape lageniform or ventricose, occasionally cylindrical, rarely pyriform, clavate-stipitate or clavate-lageniform or clavate-ventricose; special features observed often septa, occasionally many collapsed in exsiccata, rarely yellow contents, basal thickening, sparse, branching, geniculate, median thickening, plaques or thick content in neck; cheilocystidia ratios: A/M = 1.00–1.44; A/B = 0.54–0.88; B/M = 1.39–1.89.

  Pleurocystidia: usually none seen, rarely only close to lamella edge.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 120 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation usually yes, occasionally no; shape of trama elements beneath subcutis usually cylindrical, occasionally ellipsoid, thickly sausage-shaped or isodiametric up to 16 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 95 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Where only one possible associate was recorded, the most commonly recorded associate was Pinus (42.1%) but Picea (17.8%), Salix (13.1%), Betula (7.5%), Populus (6.5%), Tilia (6.5%), Quercus (2.8%) and Abies (1.9%) were also recorded. In these cases the most commonly recorded families were Pinaceae (62.1%), Salicaceae (21.6%), Betulaceae (6.9%) and Malvaceae (6.0%). We have additional records where Tsuga (2.9%), Alnus (1.7%) and Larix (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 Pinaceae (69.2%), Salicaceae (30.2%), Betulaceae (14.5%) and Fagaceae (12.8%) The growth habit of our collections was occasionally gregarious or scattered and rarely caespitose or solitary.

  According to our current collections, the species is predominantly found in Northern America (99.5%) but also found in Europe (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 (33.8%), temperate conifer forests (30.3%) and boreal forests/taiga (26.8%), specifically including the ecoregions: Atlantic coastal pine barrens (21.2%). From collector information, it appears collections have been found in the 1.4 Forest – Temperate (46.3%) and 1.1 Forest – Boreal (24.5%) 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 Northern America we have records from Northeastern U.S.A. (New York, New Jersey, Ohio, Michigan, Pennsylvania, Massachusetts and Indiana), Subarctic America (Northwest Territories, Yukon, Alaska and Greenland), Eastern Canada (Quebec, Newfoundland and Labrador, Ontario and New Brunswick), Northwestern U.S.A. (Colorado and Wyoming), Mexico (Mexico), Southeastern U.S.A. (North Carolina and Tennessee), Western Canada (British Columbia and Manitoba), North-central U.S.A. (Minnesota) and Southwestern U.S.A. (California).

  Within Europe all our records are from the Southwest (France).

• arrow_drop_downarrow_drop_upCommentary
  This species belongs within Hebeloma sect. Hebeloma, given the small ellipsoid to ovoid pale yellow spores and the ventricose to lageniform cheilocystidia. Morphologically H. excedens is similar to H. mesophaeum and H. pascuense. Peck believed that the pileus margin extending beyond the lamellae was a character that enabled this taxon to be identified in the field. It is unlikely that the character is sufficient for field identification, nor is it always present, but it does appear to help with separation from H. mesophaeum. The normally very pale yellow spores in KOH under the microscope also help separating the two species as we currently interpret them. Hebeloma excedens as understood here is very rare in Europe, absent from the true arctic and alpine habitats, and much more common in the eastern half of North America than H. mesophaeum. As shown in Eberhardt et al. (2021x), Cripps et al. (2019) and Eberhardt et al. (2021a) in pruned quasimedian networks, based on ITS, H. excedens can be separated from all other taxa, but not from H. mesophaeum. As far as possible, molecular and morphological data support the synonymizations made here. The separation between H. excedens and H. mesophaeum is currently not well supported, but we prefer to keep them separate as we gather further information with regard to these taxa.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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