Summary:
Features include 1) large size for an Inocybe, 2) a dry, radially silky cap that is straw yellow to yellow ocher with a more reddish orange umbo, varying to almost blackish, or (if the veil is prominent) quite whitish, or (if yellow variants included in concept) even bright yellowish, the cap prone to radial splitting, 3) adnate to adnexed gills that vary from white to grayish buff or pale yellow (or bright yellow if yellow variants included), becoming olivaceous brown, 4) a stem that may be enlarged at the base but not generally bulbous, and is white or pale straw-colored, (or yellow if yellow variants included), on handling or in age usually discoloring yellowish to brownish yellow or even dark brown, 5) odor often strongly spermatic, 6) snuff brown spore deposit, 7) smooth elliptic spores, and 8) absent pleurocystidia and cheilocystidia. |Kuyper(1) considers I. holoxantha Grund & D.E. Stuntz (here Pseudosperma holoxanthum) to be a bright yellow variant of I. rimosa (Bull.: Fr.) P. Kumm (here Pseudosperma rimosum). Matheny(14) in combining Inocybe holoxantha Grund & D.E. Stuntz into Pseudosperma holoxanthum, cite "Phylogenetic (unpublished but released sequence data; paratype sequenced)". |Both Stangl(2) and Kuyper(1) consider Inocybe fastigiata (Schaeff.: Fr.) Quel. a synonym of Inocybe rimosa (here Pseudosperma rimosum). Phillips describes I. fastigiata var. fastigiata below. Phillips also describes I. fastigiata var. umbrinella, and that is also considered by Kuyper(1) a synonym of I. rimosa. On the other hand, Phillips describes I. fastigiata var. microsperma (spores 8-10 x 5-6 microns, small bulb at stem base, and spermatic odor instead of slight farinaceous, found in eastern North America, but Kuyper(1) makes var. microsperma a synonym of Inocybe cookei Bres.).

Gills:
"adnexed; pallid creamy gray, later dull grayish", (Phillips), adnexed becoming sinuate-free, close to crowded, narrower closer to stem, not broad, subventricose; whitish at first soon tinged olive or gray, darker when old, (Kauffman for I. fastigiata), adnexed to almost free, scarcely ventricose, at first brownish-clay-colored, distinctly darker, ferruginescent; edges white-fimbriate, (Kauffman for I. rimosa), attached, close, narrow; whitish when young, becoming grayish then coffee-brown at maturity, (Bessette), adnexed, crowded, narrow; "grayish, tinged with olive, then brownish", edges lighter, (Lincoff(1)), "attached, becoming nearly free, close to crowded, narrow; whitish, becoming olive-grayish to pale brown", (Lincoff(2)), narrowly adnate to almost free, often crowded to very crowded, (40)50-100(115) reaching stem, 1(3) subgills between neighboring gills, gills (0.15)0.2-0.6(0.8)cm broad, very narrow to ventricose; when young white, pale gray to pale yellow, sometimes bright yellow, then grayish yellow to grayish buff or ochraceous yellow, finally yellow brown to olivaceous yellow-brown, "almost always with distinct olivaceous tinges when old", edges "white, sometimes becoming yellow-brown on damage"; edges denticulate-floccose, (Kuyper)

Stem:
3-9cm x 0.4-1.2cm, no bulb, white or pale straw-colored, (Phillips), 4-8cm x 0.4-1cm, equal or widening downward, solid; white or slightly fuscescent [becoming fuscous]; somewhat fibrillose, sometimes twisted, (Kauffman for I. fastigiata), 4-6cm x 0.3-0.6cm, subbulbous at base, round in cross-section, solid, firm; white, scarcely or slightly ochraceous tinged when old; innately fibrillose, mealy at top, (Kauffman for I. rimosa); 4-9cm x 0.3-1.2cm, nearly equal or narrowing slightly downward; whitish, developing yellowish tinges when old; smooth, silky-fibrillose, longitudinally striate, (Bessette), cylindrical or enlarged at base but never bulbous, (Lincoff(1)), 2-12.5(17.5)cm x 0.2-1.1cm, sometimes partly underground, equal to somewhat club-shaped, rarely submarginately bulbous with fringed margin, stem solid, sometimes twisted; whitish, sometimes yellow, discoloring when old and on handling to yellowish or brownish-yellowish, but underground part staying white, sometimes even discoloring to (dark) brown, sometimes hardly discoloring at all; flocculose at top or woolly-hairy in upper part, but sometimes only indistinctly so, "downwards longitudinally white-fibrillose", (Kuyper), powdery at the apex (Trudell)

Veil:
partial veil and ring absent (Bessette), a veil layer often present on cap, and cap margin sometimes subappendiculate; cortina present when young, (very) soon disappearing, leaving no remnants on stem, (Kuyper)

Odor:
slight, of meal, for Inocybe fastigiata var. fastigiata, spermatic for var. microsperma, slight for var. umbrinella, (Phillips), strongly spermatic (Arora), spermatic (Lincoff(2), Lincoff(1)), strong and disagreeable, or lacking, (Kauffman for I. fastigiata), fetid (Schalkwijk-Barendsen), not distinctive for type variety of Inocybe fastigiata, spermatic for I. fastigiata var. microsperma, (Bessette), "indistinct to distinct, rather disagreeable, spermatic", or more as Amanita phalloides, or reminiscent of acorns, (Kuyper), of green corn or spermatic (Miller), "barely perceptible, fungal", (Stangl), acorns, bleach, (Buczacki)

Taste:
none (Lincoff(1)), as odor (Kuyper), mild but do not taste because of toxins (Miller)

Microscopic spores:
spores 9-13 x 5-7 microns, bean-shaped, smooth, pleurocystidia absent, (Phillips), spores 9-12 x 5-6 microns, elliptic in face view, subreniform [somewhat kidney-shaped] in side view, obtuse at both ends, smooth; pleurocystidia and cheilocystidia none, sterile cells saccate on gill edges, (Kauffman for I. fastigiata), 9-11(13) x 4.5-6 microns, pip-shaped, attenuated toward one end, inequilateral, elliptic-suboval, subobtuse at narrow end, smooth; pleurocystidia moderately abundant, 50-65 x 12-18(22) microns, thick-walled, ventricose-sublanceolate above short pedicel, sometimes stouter, obtuse at top, colorless, cheilocystidia numerous, described the same way as pleurocystidia, (Kauffman for I. rimosa), 9-15 x 5-8 microns, elliptic, smooth, (Bessette), spores (9.0)9.5-14.5(15.5) x (5.5)6.0-8.5 microns, smooth, regular, in some collections partly subphaseoliform [slightly bean-shaped]; basidia 4-spored, (a few 2-spored), 26-44 x 10-15 microns, often swollen toward apex; pleurocystidia absent, cheilocystidia (28)30-65(80) x (9)10-22(23) microns, "(broadly) cylindric to (sub)utriform or subclavate, thin-walled, sometimes with yellowish brown contents"; caulocystidia in clusters at apex of stem, similar to cheilocystidia (when stem apex flocculose) or as long catenate hairs with cheilocystidioid terminal element (when stem woolly-hairy) or as a mixture of both types; cap trama "with scarce to abundant refractive hyphae with yellow-brown contents", (Kuyper)

Spore deposit:
snuff brown (Phillips), dull yellow brown (Barron), brown (Bessette), dull brown (Miller), olive-brown (Buczacki)

Notes:
There are collections for either Pseudosperma rimosum (as Inocybe rimosa) or Inocybe fastigiata (Schaeff.) Quel. at the University of British Columbia for BC, WA, and AB, at the University of Washington for WA, OR, ID, CA, CO, MI, and NY, and at Oregon State University for WA, OR, AK, and Argentina. Kernaghan(1) reported P. rimosum (as I. rimosa) from AB. A MA collection was used in Kropp(2). Bearing in mind that Kuyper(1) considered Inocybe holoxantha a synonym of Inocybe rimosa, Kuyper(1) examined collections of I. rimosa (here Pseudosperma rimosum) from Washington (type of I. holoxantha), Austria, Belgium, Czechoslovakia, Faeroes, France, Germany, Italy, Netherlands, Norway, Sweden, Switzerland, United Kingdom (England, Scotland), and Morocco. Inocybe fastigiata var. umbrinella was noted by Phillips for MS.

EDIBILITY

poisonous (Phillips), poisonous, causing gastric distress, (Bessette)

Synonyms and Alternate Names:
Inocybe rimosa (Bull.: Fr.) P. Kumm.