Summary:
Section Subrutilescentes. Agaricus subrutilescens has a dark purple-brown cap and a shaggy white stem. It is distinguished from similar scaly forms by the definite vinaceous color; also notable is the greenish staining with KOH, known in Agaricus only from this species and a similar one in the southeastern United States.

Cap:
5-15(20)cm across, convex or with a somewhat flattened top, becoming broadly umbonate to flat or with an uplifted margin; "covered with brown to purple-brown or wine-colored fibrils or fibrillose scales (sometimes only at the center) on a white to dingy background"; dry, (Arora), 7-13(20)cm across, at first narrowly convex to convex, later often broadly convex, or sometimes conic-convex to narrowly truncate, finally nearly flat, sometimes with slight, broad umbo; fine scales at first colored dark brown, becoming more reddish-brown, when old more drab, background whitish, becoming dingy; "dry, innately fibrillose, sometimes remaining so, or becoming shallowly fibrillose-areolate, more usually becoming appressed-fibrillose-squamulose", the fine scales extensive, about 0.3-0.8cm long and 0.2-0.4cm wide, pointed, sometimes slightly scurfy, (Kerrigan)

Flesh:
firm; white, not staining when bruised, (Arora), up to 1-1.5cm thick; white, unchanging, in stem white and unchanging, (Kerrigan)

Gills:
free at maturity, close; whitish then pinkish then pinkish brown then chocolate brown or blackish brown, when pinkish usually bruising brighter rosy pink when cut, (Arora), free, close, up to 0.8cm broad; pallid then pink, bruising rosy color, then dark blackish brown, (Kerrigan(1))

Stem:
5-20cm x 0.5-2(4)cm, equal or wider below, stuffed or hollow, often fragile when old; above the ring smooth and white or reddish, below the ring sheathed with soft cottony white scales that break up into fibrillose patches when old or wear away, (Arora), 8-17cm x 0.5-1.5(3)cm, equal or sometimes club-shaped, or rarely somewhat ventricose [spindle-shaped], base fairly deeply rooted in litter; white, except top part initially pink; at first sometimes obscurely finely floccose zonate in upper part, becoming smooth or with fine striations, covered in lower part with abundant fibrils that fall off, (Kerrigan(1)), base aging brownish (Chariton)

Veil:
membranous, white, forming a thin, usually superior, skirt-like ring on stem, (Arora), veils "forming a thin, entire, pendant (or pendant-upturned and appearing peronate), subapical (rarely to median), white annulus, upper surface smooth or finely striate", lower surface fibrillose-floccose, with a thin, narrow band formed of universal veil, universal veil also forming well developed layer of deciduous fibrils on lower part of stem, (Kerrigan(1))

Odor:
mild or slightly fruity (Arora), fruity / spicy after exposure (Kerrigan(1)), pleasant (Phillips)

Taste:
pleasant (Phillips), mild and pleasant (Miller)

Microscopic spores:
spores 4.5-6 x 3-4 microns, elliptic, smooth, (Arora), spores (4.1)4.9-5.4(6.4) x (3.0)3.1-3.8(4.1) microns, elliptic, dark brown, hilar appendix not prominent, germ pore not evident; basidia 4-spored, 14-20 x 6-7 microns, clavate, sterigmata 2-4 microns long; cheilocystidia not abundant, scattered, 10-17 x 8-12 microns (occasional cells to 40 x 17 microns), clavate, ovoid, or spherical, gill margin composed primarily of cells oriented parallel to margin, nearly sterile, (Kerrigan(1))

Spore deposit:
chocolate brown (Arora)

Notes:
The holotype is from OR. It has been found at least in WA, OR, and CA (Isaacs who says it is commoner in the south part of the range). There is a collection from BC by Paul Kroeger deposited at the University of British Columbia.

EDIBILITY

yes, but severe gastric upsets in some (Arora)