Summary:
Inocybe variabillima is distinguished in the field by 1) a silky shining cap with a dark brown prominent umbo and a paler margin, 2) persistently white gills, and 3) a slender, satiny stem turning brown at the base, (Grund). Microscopic characters include angular, scarcely nodulose spores and broad, fusiform-clavate cystidia, (Grund). Inocybe astoriana Murrill and Inocybe ochraceoscabra Atk. are given by Kauffman(4) as synonyms of Inocybe decipientoides Peck. Inocybe globocystis Vel. is given by Stuntz(1) as a synonym of Inocybe decipientoides Peck. Inocybe decipientoides Peck and Inocybe acystidiosa Kauffman are given by Nishida(2) as a synonym of Inocybe variabillima Speg. Inocybe curvipes P. Karst. may actually be the correct name. The description here is derived from Stuntz(1).

Cap:
1-3.5cm across, bell-shaped becoming expanded, convex, finally depressed at center, always with a prominent mammiform umbo; dark brown at the umbo, elsewhere buff or brownish ocher or fawn, "wood brown" [Ridgway(1) color], the margin sometimes almost cream color; innately radially silky, smooth, and satiny-shining, sometimes becoming rimulose to rimose [finely to coarsely cracked] toward margin, the umbo staying bald, sometimes a few appressed squamules [fine scales] between center and margin

Flesh:
in cap thick at center, thin elsewhere, firm, white, unchanging; in stem fragile, white in upper part, some becoming brown in lower part

Gills:
"adnexed to squarely adnate, often uncinate, subdistant, sinuate, narrowing towards margin", rather broad, 0.3-0.4cm broad; "at first white, long remaining so, becoming gradually pale grayish brown, finally brownish ochraceous"; white becoming gradually pale grayish brown then brownish ochraceous, edges white; edges fimbriate [fringed]

Stem:
4-5cm x 0.5-0.7cm, usually narrowing downward, solid or stuffed in lower part, base never bulbous; pallid to cream color in upper part, in lower part buff at first, becoming dark brown at base sometimes with obscure vinaceous tinge; satiny-shining, often spirally twisted, white-pruinose at top

Veil:
persistent remains of copious white cortina on upper part of stem

Odor:
strong spermatic

Microscopic spores:
spores 8-11(13) x (4.5)5-7(8) microns, varying from slightly angular to having 6-10 round, low, inconspicuous nodules; pleurocystidia abundant, 43-72(78) x 16-30(36) microns, mostly 55 x 20 microns, "mostly inflated-fusiform-clavate above a long slender pedicel", varying in size and shape, sometimes almost mucronate, "varying from rather thin-walled to thick-walled laterally or apically", cheilocystidia abundant, densely crowded along sterile edges, similar to pleurocystidia, sterile cells [paracystidia] "few, large and clavate, closely resembling the immature cheilocystidia except for their thin wall"; gill trama "loosely woven, extremely heterogeneous, with all sizes and shapes of cells, from enormous inflated-fusiform ones to small, slender connective tissue", "lactifers occurring frequently, especially in the subhymenium"

Spore deposit:
[presumably close to brownish ochraceous]

Notes:
Inocybe variabillima has been found at least in WA (Stuntz), WA, OR, MA to MD, (Kauffman), CA (Nishida), AK (Miller), and NS (Grund). There are collections from BC at the University of British Columbia (as I. decipientoides).

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Synonyms and Alternate Names:
Inocybe acystidiosa Kauffman
Inocybe astoriana Murrill
Inocybe decipientoides Peck
Inocybe globocystis Vel.
Inocybe ochraceoscabra G.F. Atk.