Summary:
Section Denudata subsection Crustuliniformia. Features of the Hebeloma crustuliniforme group include a smooth, viscid, pallid to pie-colored cap, adnate or notched brown gills, absent veil, and radish odor, but there are several species fitting this description that can only be differentiated microscopically and undescribed species are likely. Beker(1) say (with Latin names italicized), "Our own personal experience of examining herbarium material labelled H. crustuliniforme is that it is likely to represent almost any medium to large species from either H. sects. Denudata or Velutipes." |The term ''Hebeloma crustuliniforme group'' as used here indicates a similarity in appearance among members rather than the genetic relatedness implied when the term ''Hebeloma crustuliniforme clade'' is used. Aanen(1) use a third term, ''Hebeloma crustuliniforme complex'', consisting of Hebelomas lacking a partial veil, lacking a rooting stem, with weeping gills, lacking a loosening perispore on the spores, and having less ornamented spores relative to other veil-less Hebelomas. A combination of morphology, molecular studies and intercompatibility tests were used to delineate the complex. 20 intercompatibility groups were identified, 3 of them later proving to be genetically less related to the others. |A somewhat narrower Hebeloma crustuliniforme complex is further discussed in Eberhardt(1) along with other members of Hebeloma section Denudata subsection Crustuliniformia (subsection Denudata). Eberhardt(1) distinguish 9 species from Europe in the Hebeloma crustuliniforme complex: H. crustuliniforme (Bull.) Quel. emend. Vesterh., U. Eberh. & Beker, H. aanenii, H. geminatum, H. alpinum, H. eburneum, H. louiseae, H. minus, H. pallidolabiatum and H. salicicola. [Unpublished research indicates the presence of H. crustuliniforme, H. aanenii, and H. geminatum in the Pacific Northwest (H. Beker, pers. comm.)]. |Other members of Hebeloma section Denudata subsection Denudata included from Europe are H. helodes (also found in the Pacific Northwest according to the unpublished research), H. aurantioumbrinum, H. luteicystidiatum, H. lutense, H. perexiguum, and H. pusillum. These were separate in molecular study, but the key to this subsection uses the following characters: habitat (association with Salix or Dryas or not), cap coloring (uniform or bicolored), the number of gills that reach the stem, and details of spores and cheilocystidia. |Hebeloma crustuliniforme has been commonly identified as such in the Pacific Northwest. According to Trudell(4), one apparently common Pacific Northwest species that has been misidentified as H. crustuliniforme is H. incarnatulum (see that description and the SIMILAR section of this description). H. incarnatulum is closely related to H. velutipes rather than H. crustuliniforme in the Boyle(1) molecular study.

Cap:
3-11cm across, convex or broadly convex with inrolled margin, becoming flat to obtusely umbonate or with an uplifted margin when old; "whitish to buff, pale tan, or crust-brown (usually darker toward center and paler at margin)"; viscid when moist, smooth, margin naked, (Arora), margin often lobed (Phillips), 3-7(9)cm, convex with inrolled margin at first, becoming broadly convex or flat, when old the margin spreading or uplifted; cream color gradually becoming pale to moderately dark alutaceous, often darker on the disc; bald, viscid, appearing varnished when dry, "margin opaque and even and remaining white-pruinose for some time", (Smith(15))

Flesh:
thick; white, (Arora), firm, thick on disc, tapering abruptly near margin; white, (Smith(15))

Gills:
emarginate, maximum breadth 0.4-0.8cm, 60-100 gills reaching stem, droplets usually visible to the naked eye; edge white-fimbriate, (Beker), adnate or notched, "crowded (often appearing to slightly overlap one another)"; "pallid when young, becoming watery brown and finally dull brown"; "edges white and minutely scalloped, often beaded with water droplets in wet weather and brown-spotted when dry", (Arora), bluntly adnate becoming adnexed, close to crowded, narrow becoming moderately broad; "pallid when very young, soon pale avellaneous and finally clay-color"; edges white-crenulate [white-scalloped] and often beaded with drops of moisture, (Smith(15))

Stem:
2.5-11.0(11.5)cm x (0.6)0.7-2.0cm at mid-stem, 0.8-2.0cm wide at base, cylindric or clavate, occasionally even bulbous, not rooting and no mycelial cords; surface floccose, (Beker), 4-13cm x 0.5-1.5(2)cm, usually equal except enlarged base, solid; "white or tinged cap color"; fibrillose, top "powdered or with flakes or granules", "base sometimes with white mycelial threads", (Arora), 4-7cm x 0.6-1cm thick, solid, equal or base more or less abruptly widened and surrounded by copious white mycelium; stem white; top furfuraceous, fibrillose downward or when old sometimes lacerated, (Smith(15))

Veil:
cortina absent (Beker), absent (Arora)

Odor:
raphanoid [radish-like], sometimes strongly, (Beker), distinctly radish-like, (Arora), usually strongly radish-like, but odor may be faint, particularly if fruitbodies have stood for a time before being collected, (Smith(15))

Taste:
"mild to weakly bitter, often raphanoid" (italicized), (Beker), bitter (Phillips), radish-like or more spicy, (Smith(15))

Microscopic spores:
spores (9.2)9.6-13.5(14.9) x (5.4)5.5-7.2(7.7) microns, average length 10.8-12.2 microns, average width 6.1-6.7 microns, amygdaloid [almond-shaped], yellow to yellow-brown or pale brown under the microscope, usually guttulate, at most weakly papillate; basidia 4-spored (rarely 2-spored), (26.5)26.7-36.8(40.2) x (6.8)7.4-9.8(10.5) microns; cheilocystidia (22)29-86(105) x (3.9)4.9-10.3(13.4) microns wide at apex, (1.9)2.4-6.2(7.4) microns wide at middle, (1.9)2.4-7.5(7.9) microns wide at base, "mainly clavate-stipitate or spathulate-stipitate, occasionally gently clavate or clavate-lageniform" (italicized), occasional characteristics "median thickening, septate (sometimes clamped), sinuate" (italicized), pleurocystidia none; caulocystidia similar to cheilocystidia, up to 90 microns long, sometimes multiseptate, (Beker), spores 9-13 x 5.5-7.5 microns, elliptic or almond-shaped, smooth or minutely rough; cheilocystidia abundant, (Arora), spores 9-11.5 x 5.5-7 microns, inequilateral to somewhat almond-shaped, "very minutely punctate or appearing smooth under ordinary magnifications", pale tawny when revived in KOH; basidia 4-spored, 32-34 x 7-8 microns; pleurocystidia none; cheilocystidia abundant, 50-70 x 6-8 microns, thin-walled, narrowly clavate to cylindric or when old almost filamentous; gill trama homogeneous, hyphae colorless (in KOH) and subparallel; cap trama homogeneous beneath a thin gelatinous pellicle of narrow (3-4 microns wide), colorless hyphae with abundant clamp connections, (Smith(15))

Spore deposit:
brownish olive (Beker), brown (Arora), rust-brown (Phillips), yellow-brown to brown (Miller)

Notes:
Unpublished research indicates that Hebeloma crustuliniforme occurs in BC, WA, OR, and CA (Henry Beker, pers. comm.). Collections designated as Hebeloma crustuliniforme are indicated by Smith(15) for Washington, Oregon, and Michigan, and by Arora(1) for CA, but these identifications should be treated with caution. Beker(1) wrote [as quoted above], "Our own personal experience of examining herbarium material labelled H. crustuliniforme is that it is likely to represent almost any medium to large species from either H. sects. Denudata or Velutipes." There are collections labeled Hebeloma crustuliniforme from British Columbia at the University of British Columbia and the Pacific Forestry Center. Beker(1) examined collections from Cyprus, Denmark, France, Germany, Macedonia, Netherlands, Portugal, and the United Kingdom.

EDIBILITY

poisonous, causing mild to severe gastrointestinal distress, (Arora), clinical effects in European accounts are similar to those produced by muscarine but some gastrointestinal effects are also present, (Smith(15))