Hebeloma albidulum (Photo: H. J. Beker)

Taxonomy

Types: UNITED STATES: New York: Essex County, Westport (approx. 44.18°N, 73.43°W, alt. approx. 40 m a.s.l.) on litter in woodland, 6 Oct. 1900, C.H. Peck (Lectotype. herbarium acc. no. NYS-F-000133.1, HJB1000451; Isotype. herbarium acc. no. WTU-F-039675, HJB1000308). Lectotype designated by Eberhardt et al., Mycologia 114 (2): (2022) page 346 (MBT10000876).

• arrow_drop_downarrow_drop_upType notes
  We divided the holotype material we received from NYS into two parts: NYS-F-000133.2 [“albidulumA”] and NYS-F-000133.1 [“albidulumB”]. The part labelled “albidulumA” is morphologically from Hebeloma sect. Hebeloma with a partial veil and has small elliptical spores; it most closely resembles H. excedens, with a dark brown colored pileus, a stipe that is never bulbous at the base and usually with velar remnants and with small pale yellow spores. The part labelled “albidulumB” is from Hebeloma sect. Velutipes, where species do not have a partial veil and usually exhibit a bulbous base; microscopically, it has larger spores, more closely matching the size given in the protologue. Thus, “albidulumB” more closely resembles the protologue in all respects and was selected as lectotype. An ITS sequence has been successfully generated from the lectotype, which supports the morphological placement in Hebeloma sect. Velutipes.

Heterotypic synonyms:

• Hebeloma brunneifolium Hesler, Kew Bulletin 31 (3): 473 (1977)
• Hebeloma crustuliniforme f. minus Kauffman [as "minor"], The Agaricaceae of Michigan: 476 (1918)
• Hebeloma exiguifolium Murrill, N. Amer. Fl. 10 (3): 221 (1917)
• Hebeloma simile Kauffman, The Agaricaceae of Michigan: 479 (1918)
• Cortinarius albiceps Murrill, Lloydia 5: 146 (1942)
• Cortinarius fimbriatus Murrill, Lloydia 7 (4): 317 (1945) ["1944"]

• arrow_drop_downarrow_drop_upEtymology
  From albidulus (Latin), meaning ‘whitish’.

• arrow_drop_downarrow_drop_upDiagnosis
  Pileus fleshy, firm, broadly convex or nearly plane, glabrous, slightly viscid when moist, dingy white or grayish white, flesh white; lamellae close, narrow, adnexed, minutely denticulate and white on the edge, whitish, becoming brownish ferruginous; stem equal, firm, glabrous, slightly mealy or pruinose at the top, sometimes slightly bulbous, hollow, colored like the pileus; spores subelliptic, obtuse, .0004-.0005 of an inch long, .00024-.0003 broad [10.2-12.7 x 6.1-7.6 µm]. Pileus 1-2.5 inches broad [25.4-63.5 mm]; stem 1.5-2.5 inches long [38.1-63.5 mm], 2-3 lines thick [5.1-7.6 mm]. Among fallen leaves in woods. Westport. October. This is closely related to the preceding species [Hebeloma album]. The pileus is not a clear white, the stem is hollow and the spores are a little darker in color and shorter and more blunt at the ends.

Description

Description of Hebeloma albidulum based on 70 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (20) 21–60 (70) mm diameter; shape often convex, occasionally broadly umbonate, rarely applanate, umbonate, weakly umbonate or strongly umbonate; characters rarely rugulose or spotting; margin characters usually smooth, occasionally involute, rarely wavy, fibrillose or overhanging pileus; viscosity tacky when moist; colour variation often unicolour, occasionally two color; colour at centre occasionally cream or pale cream, rarely pale pinkish buff, yellowish brown, clay-buff, dark pinkish buff or cinnamon.

  Lamellae: attachment usually emarginate, occasionally adnexed, rarely adnate or decurrent tooth; maximum depth 3–6 mm; number of complete lamellae 50–70; presence of tears often absent, occasionally visible with naked eye, rarely visible with x10 lens; white fimbriate edge usually present, rarely very strong.

  Cortina presence: no.

  Stipe: (30) 32–73 (90) x (2) 3–10 (13) {median} x (2) 6–18 (21) {basal} mm; stipe Q 4.6–16.0; base shape usually bulbous, occasionally cylindrical, rarely clavate or subbulbous; floccosity often pruinose at apex, occasionally velute, fibrillose or floccose, rarely floccose at apex or pruinose; rooting no; thick rhizoids at base usually present, rarely absent;

  Context: Texture firm; stipe interior often hollow, occasionally stuffed or superior wick; stipe flesh discolouring usually no, rarely weak; slenderness measure 4.0–26.7; smell often raphanoid, occasionally odourless, rarely strongly raphanoid, weakly raphanoid, farinaceous or soap; taste occasionally raphanoid, bitter, mild or weakly raphanoid, rarely hot where recorded.

  Spore deposit colour: umber.

  Exsiccata characters: hard or lamellae blackening.

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

  Basidia: 19–33 (34) x 5–9 μm; ave. Q 2.9–3.8; spore arrangement 4 spored;

  Cheilocystidia: main shape gently clavate, usually ventricose, often clavate-lageniform or clavate-ventricose, rarely lageniform; special features observed occasionally plaques, bifurcate or many collapsed in exsiccata, rarely geniculate, clamped septa, conglutinate or yellow contents; cheilocystidia ratios: A/M = 1.34–1.74; A/B = 1.15–1.66; B/M = 0.95–1.38.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 120 μm; ixocutis hyphae width up to 7 μm; ixocutis hyphae encrustation yes; shape of trama elements beneath subcutis often ellipsoid or thickly sausage-shaped, occasionally cylindrical, oblong, ovate, polygonal or pyriform up to 20 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 albidulum's preferred habitat appears to be mixed woodland with soil or soil and litter. Where only one possible associate was recorded, the most commonly recorded associate was Quercus (60.0%) but Tsuga (13.3%), Fagus (13.3%) and Pinus (13.3%) were also recorded. In these cases the most commonly recorded families were Fagaceae (77.8%) and Pinaceae (22.2%). We have additional records where Betula (17.0%), Ostrya (3.8%), Carya (3.8%), Carpinus (1.9%) and Tilia (1.9%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Fagaceae (84.9%), Pinaceae (62.3%) and Betulaceae (18.9%) The growth habit of our collections was occasionally solitary or scattered and rarely gregarious or caespitose.

  According to our current collections, the species is found only in Northern America. 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 (78.3%) and temperate conifer forests (13.0%), specifically including the ecoregions: Appalachian-Blue Ridge forests (24.6%), New England-Acadian forests (20.3%), Atlantic coastal pine barrens (11.6%) and Eastern Great Lakes lowland forests (10.1%). 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 Northern America we have records from Northeastern U.S.A. (Massachusetts, New Jersey, New York, Pennsylvania, New Hampshire, Michigan and Ohio), Southeastern U.S.A. (North Carolina, Florida and Tennessee), Eastern Canada (Quebec), North-central U.S.A. (Wisconsin and Minnesota) and South-central U.S.A. (Texas).

• arrow_drop_downarrow_drop_upCommentary
  Within this section of the genus, the most important features appear to be the absence of pleurocystidia, and spores with a strongly loosening perispore, visible even without oil immersion, and average length at most 11.5 µm and width between 6.5 and 7.5 µm. Morphologically Hebeloma albidulum most closely resembles H. celatum and H. quercetorum, none of which have been recorded in North America. Further, while both these species have a loosening perispore, this does not occur as strongly and consistently as is the case for Hebeloma albidulum (P2 rather than the P3 of H. albidulum). We have found no earlier name for this taxon, but there are four later names, three species and a form. For two of them, H. brunneifolium and H. exiguifolium, ITS sequences could also be generated from the types, matching the ITS of H. albidulum, the only differences are in 1–2 bp positions with ambiguous reads in one of the compared sequences. In FIG. 1, H. albidulum is more closely related to the velutipes-complex than it is to members of the quercetorum-complex. (For more information on these complexes, see Grilli et al. 2016; Beker et al. 2016).

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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