E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Features include 1) a grayish, fibrillose-scaly cap, 2) free, close, white gills, 3) a white stem that is bald to silky, 4) a membranous, white ring, 5) habitat in cultivated ground, 6) a white spore deposit, and 7) dextrinoid spores. The macroscopic description, derived from Smith(15), is directly from the original Oregon description of Zeller (apart from habitat).

Leucoagaricus barssii is found at least in OR (Smith(15) and collections at Oregon State University), and according to Sieger(1) in WA as well. Vellinga mentions material from CA, and her concept includes synonymous taxa from Europe. There is a collection from WA at the University of Washington and a collection from BC at the University of British Columbia.

Cap:
4-15cm across or more, nearly round to convex, becoming broadly convex to flat or umbonate; covered with fine, flattened, gray to brownish gray, radiating fibrils, center often darker; dry, sometimes becoming scaly when old or in direct sunlight, (Arora), 7-15cm across, nearly spherical to ovoid, then convex to flat-expanded, obtusely umbonate to subumbilicate [somewhat umbilicate], "sometimes splitting radially at margin"; "smoke-gray to drab, with darker, fuscous or cinnamon-drab umbo"; dry, covered by fibrillose, fuscous scales, (Smith from Zeller, but Smith also calls the cap "drab to cinnamon-drab or nearly wood brown")

Flesh:
fairly thick; "white to grayish, not staining when bruised", (Arora), "thick at disk but very thin toward margin"; white at first then sordid, (Smith)

Gills:
free, close; "white or staining dingy yellowish to brownish", (Arora), free, close but not crowded, 0.7-1.6cm broad, unequal, narrower near stem; white, changing to slightly stramineous [straw-colored]; edges even, (Smith)

Stem:
5-13cm x 0.5-2.5cm, equal or more often swollen in lower part, but with tapered base (no bulb); white or stained brownish, (Arora), 8-12cm x 0.8-1.8cm in upper part, almost equal (1-1.5cm in lower part), stuffed then hollow; white; bald or silky above and below ring, (Smith), whitish, when handled discolors brownish, (Trudell)

Veil:
"membranous, white, forming a superior, collarlike ring" that may be movable and may drop off, (Arora), ring "formed from veil and outer layer of stem, white, collar-like, persistent, superior, often movable at maturity", (Smith), somewhat fragile, may leave a ring or remain attached to cap margin; when formed the ring is whitish on upper side and brownish on lower side, (Trudell)

Odor:
not remarkable (Sieger), pleasant (Smith)

Taste:
not remarkable (Sieger), pleasant (Smith)

Microscopic spores:
spores 7-11 x 5-6 microns, elliptic, smooth, dextrinoid, (Arora), spores 7.5-9 x 4.5-5 microns, elliptic to suboval, rusty-reddish brown in iodine, with a somewhat thickened wall and a small apical pore; basidia 4-spored, 18-22 x 7-8 microns, clavate, yellowish in iodine; pleurocystidia not seen, cheilocystidia abundant, 20-30 x 10-16 microns, "vesiculose, clavate or broadly fusoid-ventricose to mucronate", colorless, thin-walled, and readily collapsing, (Smith), spores 7.6-9.1 x 4.6-5.7 microns, elliptic to oblong, some with straighter adaxial than abaxial side, dextrinoid, metachromatic in Cresyl blue, congophilic, without germ pore; basidia 4-spored, 20-28 x 7.0-8.5 microns; some pleurocystidia, close to gill edge, similar in size and shape to cheilocystidia, cheilocystidia producing sterile gill edge, 23-48 x 9-12 microns, narrowly clavate, cylindric with narrowed pedicel, colorless; clamp connections not seen, (Vellinga)

Spore deposit:
white (Arora, Smith)