Summary:
Collybia cirrhata is distinguished by 1) small size, 2) a cap that is whitish becoming orange-brownish, 3) adnexed, crowded, white gills, 4) a whitish, thread-like stem with white mycelial threads at the base, and 5) growth on old mushrooms or sometimes on humus or well decayed wood.

Cap:
0.5-1cm across, initially convex then flat, slightly depressed, often with a very small central nipple; "white, reddish brown at center, or ochreous"; surface slightly silky, "often broken up concentrically when mature", slightly grooved, (Lincoff), 0.3-1.1cm across, convex with inrolled to incurved margin. becoming convex to flat or slightly depressed on disc, with downcurved to straight margin when old; subhygrophanous [somewhat hygrophanous], whitish, becoming grayish orange when watery or old, typically with faint pink flush when fresh; dry to moist, bald to somewhat canescent [hoary], translucent-striate at margin, (Halling), 0.2-1.2cm across, convex becoming flat, occasionally slightly depressed when mature, "often shallowly papillate to broad umbonate", margin either slightly inrolled or straight when mature; hygrophanous, white at margin, light warm tan at center, spotted at disc or fading uniformly to margin, becoming uniformly colored as it fades; dry-matte, opaque, slightly powdery, margin when moist is striatulate for one quarter to one half of the radius, grooved-undulate at edge, fraying when old, (Lennox)

Flesh:
very meager; white, (Lincoff), very thin, whitish (Halling), thin, rather soft and fragile; colored as cap, (Lennox)

Gills:
adnexed, crowded, unequal, separate from stem when mature; white, (Lincoff), adnate to slightly arcuate with tooth, close to subdistant, narrow to moderately broad, thin; whitish to pinkish buff, edges colored as faces; edges even, (Halling), arcuate, broadly adnate to slightly sinuate, narrow, about 0.1cm broad, thin, subdistant, 20 reach stem, 3 tiers of subgills; white or pallid, (Lennox)

Stem:
2.5-5cm long and about 0.1cm wide, whitish, rather filiform [thread-like], "supple with powdery surface that extends to the base in a tuft of interwoven fibrils", (Lincoff), 0.8-2.5cm long and 0.1(0.2)cm wide, equal to slightly widened downward, flexible but not fragile, becoming hollow; whitish to grayish orange; faintly pubescent in upper part, more so downward, nearly strigose toward base, often branched at base into rhizomorph-like strands or with plentiful white mycelium, (Halling), 1.2-2.5cm long and 0.1cm or less wide, equal, "outline often rather wavy, especially in the lower half, flexuous", solid; colored as disc or darker, pale warm buff, somewhat more reddish toward base when old; powdery-pubescent in upper part, becoming tomentose in lower part, "strigose with white, bristle-like rhizomorphs near the substratum", (Lennox)

Odor:
none (Halling)

Taste:
none (Halling), none or farinaceous (Lennox)

Microscopic spores:
spores 4-5 microns long and about 2 microns wide, elliptic, smooth, (Lincoff), spores 4.8-6.4 x 2-2.8(3.5) microns, oboval to elliptic or slightly subcylindric in face view, elliptic to sublacrymoid [somewhat tear-shaped] in side view, smooth, inamyloid, acyanophilic; basidia 4-spored, 17.5-21 x 4.8-5.6 microns, clavate to subclavate, not siderophilic; pleurocystidia and cheilocystidia absent; cap cuticle "a poorly differentiated layer of repent, radially arranged, mostly cylindric hyphae, often with a subgelatinous matrix above", cells 2.8-6.4 microns in diameter, "smooth, thin-walled, with scattered, short diverticulate branchlets"; clamp connections present in all tissues, (Halling), (5)5.5-7.5 x 2.5-3.5 microns, elliptic to cylindric, smooth, inamyloid, colorless, thin-walled, contents homogeneous, (Lennox)

Spore deposit:
white (Lennox)

Notes:
Collybia cirrhata has been found at least in WA, ID, AK, NC, Finland, Sweden, Switzerland, and the UK, (Hughes), and OR (Kauffman). It also occurs in CA (Desjardin) and there are collections from BC at University of British Columbia. It also occurs elsewhere in North America, Europe, and Asia.

EDIBILITY

Synonyms and Alternate Names:
Microcollybia cirrhata (Pers. ex Pers.) Lennox