Summary:
Lepiota atrodisca is recognized by its unusual grayish-black scales. Other features include a white scaly cap, free, close, white or creamy gills, a white, smooth, dry stem, a membranous ring with a white upper surface and brownish underside, often with black edge, a white spore deposit and dextrinoid spores. Genetic data suggest that there are more than one taxon under this name in California and they likely belong to the genus Leucoagaricus, (Siegel(2)).

Cap:
1-5(6)cm across, oval or convex becoming broadly umbonate or flat, the margin sometimes uplifted when old; white with flattened black, gray, or greenish gray scales or fibrils, "the center usually darker (blackish)"; dry, (Arora), 2-5.5cm across, hemispheric, subconic to flat-expanded, umbonate; "mouse gray" in young specimens, becoming finally "sooty black", umbo squamulose [finely scaly], surface breaking into small fibrillose scales the same color as umbo but appearing gray because of the white surface in between; "margin sometimes almost striate, cuticle slightly splitting and receding at margin", (Zeller), 1-5cm across, convex becoming flat then uplifted, margin inrolled at first; dark grayish brown to almost black on disc, toward margin the fibers colored somewhat lighter; disc "unbroken with flattened fibers", toward margin "hairy or with flattened fibers or fibrous scales", cuticle pulled back from the edge when old, (Sieger)

Flesh:
thin; white, not bruising, (Arora), thin; white, unchanging, in stem white, (Zeller), white and sometimes becoming dingy when old but not staining when touched, (Sieger)

Gills:
free, close; white or creamy, (Arora), free, ventricose, 0.3-0.5cm broad; edges slightly serrate, (Zeller), free, close or somewhat distant, in two tiers, near stem often with forks, cross walls, or both; edges finely fringed, (Sieger)

Stem:
2.5-10cm x 0.3-0.7cm, "usually slender but sometimes rather stout", widened somewhat at base; white or discoloring slightly with handling; smooth, dry, (Arora), 5-12cm x 0.3-0.5cm, slender, equal to widening somewhat downwards, hollow stuffed with fibrils; white, finally sordid where touched; smooth, (Zeller), 1-11.5cm x 0.1-0.7cm, the base enlarged, stem stuffed becoming hollow; white sometimes bruising brown; smooth, rarely powdery, (Sieger)

Veil:
membranous, forming a fragile, sleeve-like, white or black-edged ring at or above middle of stem, or sometimes disappearing, (Arora), ring "membranous, white above, brownish below with a blackish margin, superior, persistent", (Zeller), ring "flares up like a collar and hangs down like a skirt", usually persistent, pale on upper surface, light brown on lower surface, frequently with a blackish lower margin, (Sieger)

Odor:
none (Zeller), unremarkable (Sieger)

Taste:
pleasant (Zeller), unremarkable (Sieger)

Microscopic spores:
spores 6-8 x 3-5 microns, elliptic, smooth, dextrinoid, (Arora), spores 7 x 4 microns, elliptic-oval, smooth; cheilocystidia clavate, not particularly characteristic, (Zeller), spores 6.3-7.9 x 3.1-4.7(5.65) microns, oval to elliptic and tapered, thick-walled, without germ pore, pale brown or pale reddish in Melzer''s reagent; pleurocystidia absent, cheilocystidia "clavate, cylindric, or ventricose, sometimes encrusted"; cap cuticle "filamentous trichodermium, often tangled and appearing loosely interwoven and sometimes flattened, the cells septate and elliptic or cylindric with ends that may be constricted or Y-shaped", (Sieger), spores 6-7.5 x 3.6 microns, broadly elliptic in face view, inequilateral in side view, pale yellowish to rusty brown in Melzer''s reagent; pleurocystidia none, cheilocystidia 16-48 x 4.8-9.5 microns, cylindric to narrowly clavate; cap cuticle a tangled trichodermium, the terminal cells of the trichodermial hypha scarcely differentiated (merely tubular); clamp connections absent, (Smith, H.V.)

Spore deposit:
white (Arora, Zeller)

Notes:
It has been found at least in OR (Zeller) and CA (Desjardin). There are collections from BC at the University of British Columbia, collections from OR at Oregon State University, and a collection from ID at the College of Idaho.

EDIBILITY

unknown, do not experiment, (Arora)