Summary:
Clitocybe dilatata is common, distinguished from other Clitocybe species by its whitish caps, growth in clusters on disturbed ground, and white spore deposit. Trudell(4) call this mushroom Clitocybe connata (Schumacher) Gillet. The online Species Fungorum, accessed October 25, 2018, gave the latter name as a synonym of Leucocybe connata (Schumach.) Vizzini, P. Alvarado, G. Moreno & Consiglio. Bigelow(5) says that Clitocybe cerussata var. difformis (Fr.) Bres. is a synonym. The Index Fungorum, accessed October 25, 2018, listed Clitocybe dilatata P. Karst., Clitocybe cerussata (Fr.) P. Kumm. and Clitocybe cerussata var. difformis (Schumach.) P. Karst. as synonyms of Clitocybe phyllophila (Pers.) P. Kumm. MycoBank, accessed October 25, 2018, is different, not connecting C. dilatata, C. phyllophila, and C. connata to each other. By whatever name, it is common in the Pacific Northwest.

Cap:
2-15cm across, convex to flat or often somewhat misshapen, margin incurved, often becoming wavy; gray becoming white or chalky-white sometimes with buffy areas; dry, smooth, (Arora), 1.5-15cm across, convex at first with inrolled margin, becoming flat with margin broadly decurved [downcurved] or nearly horizontal, the margin eventually very undulate [wavy] and sinuate, occasionally elevated, disc soon gibbous [humped] or umbonate, when old broadly and shallowly depressed, usually deformed from adjacent caps; gray becoming whitish with translucent watery buff areas in wet weather, chalky-white in dry weather; finely matted fibrillose under lens, finally canescent [hoary] near margin and radiate fibrillose on disc, margin not striate, (Bigelow)

Flesh:
firm; white to grayish, (Arora), thick on disc, firm; gray to whitish, (Bigelow)

Gills:
adnate to decurrent, close; whitish to buff, (Arora), adnate to short-decurrent, becoming moderately decurrent, close to crowded, narrow to broad, up to 1cm broad, forked at times; whitish to faintly yellowish, near "cartridge buff" to "pale pinkish buff"; not interveined, (Bigelow)

Stem:
5-12cm x 0.5-3cm, equal or widened below, fibrous, often curved; whitish; fibrillose, (Arora), 5-12cm x 0.7-2.8cm, central or somewhat eccentric, equal or the base somewhat widened, bases joined at times, solid or becoming hollow, fibrous, usually flattened, often curved; colored as cap but base stained sordid with bruising; fibrillose furfuraceous to fibrillose striate, at times minutely squamulose at base, when old the fibers forming reticulations (networks) in places, (Bigelow)

Odor:
mild (Arora), none (Bigelow)

Taste:
"typically somewhat sour or disagreeable" (Arora), "somewhat sour and disagreeable" (Bigelow)

Microscopic spores:
spores 4.5-6 x 3-3.5 microns, elliptic, smooth, basidia lack siderophilous granules, (Arora), spores 4.5-6(6.5) x 3-3.5 microns, elliptic, smooth, inamyloid, cyanophobic; basidia 2-spored or 4-spored, 20-26 x 4-6.5 microns; [pleurocystidia and cheilocystidia presumably absent]; clamp connections present, (Bigelow)

Spore deposit:
white (Arora, Bigelow)

Notes:
Collections were examined from BC, WA, OR, ID, YT, AK, (Bigelow(5)).

EDIBILITY

probably poisonous, thought to contain muscarine, (Arora)

Synonyms and Alternate Names:
Clitocybe cerussata var. difformis (Fr.) Bres.?
Clitocybe cerussata var. difformis (Fr.) Bres.