Summary:
The combination of a gray, fibrillose cap, a cottony persistent ring, and an association with willow is distinctive. The features include 1) a light gray, dry cap that is radially fibrillose, 2) notched to adnate or adnexed, close, light gray to white gills, 3) a white, silky-fibrillose, dry stem, 4) a white membranous, cottony, persistent ring, 5) a farinaceous odor and taste, and 6) growth under willow. It is rare.

Cap:
2-3.5cm across, obtuse or soon obtusely bell-shaped, margin incurved at first, becoming expanded or umbonate; when young dull gray overall or gray with a bluish cast along margin, changing when old to more or less dark avellaneous; "dry, appressed-fibrillose, the fibrils sometimes forming appressed scales", margin cottony at first, frequently split radially, (Shanks), 2.5-6.5cm across, obtuse to convex with an incurved margin when young, expanding to convex, convex-umbonate, flat-convex or more or less flat, margin often wavy; very pale grayish buff to light medium gray, when overmature often dingy buff with the edge becoming dull golden yellow, occasionally virgate [radially streaked] in places where the fibrils are darker gray; "dry, radially fibrillose, the fibrils often appearing slightly interwoven", occasionally with scattered minute fine scales, the disc rarely areolate - fine-scaly, "the buttons often with a fine whitish reticulum of fibrils", (Ovrebo)

Flesh:
watery drab gray when moist, pallid when faded, (Shanks), 0.2-0.8cm thick; light gray when young, nearly white when mature, in stem white, (Ovrebo)

Gills:
adnate, close; "white, tending to stains greenish yellow"; edges even, (Shanks), sinuate but occasionally adnate or adnexed, close, subgills numerous but not in distinct tiers, gills 0.2-0.7cm broad; light gray when young, becoming nearly white first near the stem and on the edge and finally overall, becoming dingy golden at cap margin when overmature, not discoloring; edges entire, (Ovrebo)

Stem:
4-6cm x 0.3-0.6cm, slightly widened in lower part; whitish or near the top pale gray; "with appressed white fibrils or zones for some distance below the ring", silky at top and more or less bald at base; "annulate from the submembranous to fibrillose remains of a copious veil", (Shanks), 3-7cm x 0.5-1cm, equal or slightly club-shaped, "the base rounded or abruptly tapered", stem solid; "white overall, occasionally discoloring yellow where bruised"; peronate [sheathed], silky-fibrillose above the ring, silky-fibrillose or with belts of dull and shiny fibrils below the ring, (Ovrebo), hollow (Schalkwijk-Barendsen)

Veil:
stem with a ring "from the submembranous to fibrillose remains of a copious veil", (Shanks), persistent, flaring, cottony-membranous ring that when old is often appressed to stem, the reticulate fibrils on the cap also likely to be part of the veil, white, discoloring yellow, (Ovrebo), "woolly to almost membranous ring" (Moser), "small fibrillose ring, which often disappears", (Schalkwijk-Barendsen)

Odor:
farinaceous (Ovrebo, Shanks), slight (Schalkwijk-Barendsen)

Taste:
farinaceous (Ovrebo, Shanks)

Microscopic spores:
spores 4.8-6.7 x 2.9-4.3 microns, elliptic to narrowly elliptic, smooth, inamyloid, colorless; basidia 4-spored, 22 x 5.8-6.2 microns, clavate; pleurocystidia and cheilocystidia absent; clamp connections absent, (Shanks), spores 4.8-5.7 x 2.9-3.8 microns, elliptic to oblong, smooth, thin-walled; basidia 4-spored, 20-26 x 5.7-6.7 microns, clavate, colorless; pleurocystidia and cheilocystidia absent; clamp connections absent, (Ovrebo)

Spore deposit:
white (Ovrebo)

Notes:
It was reported by A.H. Smith from WA (according to Shanks and the Shanks description is based on his). Ovrebo examined collections from ON, QC, MN, VT, France and Sweden. There is a Sylvester Mielczarek collection from BC deposited at University of British Columbia and annotated by Paul Kroeger. Bessette(5) say it is widely distributed in North America and shows photographs from CA and QC. Schalkwijk-Barendsen reported it from AB under conifers, although her description differs in several details from that of Ovrebo.

EDIBILITY

Synonyms and Alternate Names:
Armillaria cingulata (Fr.) Quel.