Summary:
{See also Small Agaricus Table} Section Minores, presumably. Agaricus purpurellus is a member of the A. diminutivus group with purple-tinged (bright or deep wine-red) cap. The online Species Fungorum, accessed October 10, 2012, gives this species as a synonym of Agaricus dulcidulus Schulzer, but Isaacs(1), who reported A. purpurellus from Washington State, said that he found no material fitting the description of A. dulcidulus.

Cap:
4-4.5cm across, cushion-shaped, convex, finally flattened; deep wine red at disc, whitish ground with light grayish margin, bruises ochraceous; finely appressed fibrils in small batches radiating outward, giving streaked silken look, (Dilly), 4-4.5cm across, wine red at disc, background color of margin light grayish, bruises ochraceous, "fibrils grouped in small batches to create slightly squamulose look", buttons cushion-shaped, (Chariton), 4-4.7cm across, pulvinate [cushion-shaped], becoming convex to broadly convex, disc with obscure, low, rounded umbo, or somewhat flattened-truncate, margin lobed to slightly irregular, exceeding gills; "deep, shining reddish-vinaceous to the margin which is silvery white to light grayish, the disc 13F5-6, Rh., 8E8-9, outward paler, 13B-D2-3, Rh., the margin silvery white, darkening in age to 7A-C9-10, 12B-C2-3, surface where bruised ochraceous, 12K-L7-8"; finely appressed-fibrillose, occasionally obscurely squamulose [fine-scaly] at margin, the fibrillosity usually grouped into fasciculate strands that radiate outward to margin, give cap a streaked silky appearance, disc entire, margin occasionally appendiculate with hanging veil remnants, (Isaacs), 2-4cm across, completely wine-red with purple-colored radial fibrils and scales, (Moser), up to 5cm across, vinaceous brown; fibrillose, with fibrillose margin, (Courtecuisse)

Flesh:
0.3-0.4cm thick, gradually tapering off disc; white becoming grayish, in stem brittle, punky; white to ochraceous, (Isaacs), white, yellowing, (Courtecuisse)

Gills:
pale grayish wine then reddish, (Chariton), free, gradually rounded at cap margin and stem, rather broad, about 0.5-0.7cm, ventricose to arcuate, not reaching cap margin; ''at first "pale grayish-vinaceous", R39, to "light vinaceous fawn", R40, pale rosy, then darkening to reddish-brown or black, 8E-H10'', (Isaacs), deep (Moser), grayish then vinaceous brown (Courtecuisse)

Stem:
3.5-7cm x 0.5cm, equal to having rounded bulbous base; white or pallid, often staining yellowish, sometimes slightly tufted at base, (Chariton), 3.5-6.5 x 0.45-0.65cm, equal in upper part, with a rounded bulbous base about 0.9cm wide, occasionally merely club-shaped, punky inside then hollow at base; pure white at first, then tinted with flesh color, 11B-C2, where handled becoming ochraceous, 12K-L8-9; silky-shining above ring, "streaked-fibrillose-appressed to slightly floccose toward base, the flocculae often breaking up into patches over surface", (Isaacs), club-shaped, in middle about 0.5cm, (Moser), up to 5cm long and 0.5cm wide, white, yellowing, (Courtecuisse)

Veil:
single, thin, white, fleeting, (Chariton), ring superior, sheathing above, flaring at first then becoming appressed to stem, "single, finely cottony-tomentose, often upturned and oblique at first, narrow", (Isaacs)

Odor:
faintly fragrant anise (Chariton), sweet, almond-like, (Isaacs), of bitter almonds (Courtecuisse)

Taste:
sweet, almond-like, (Isaacs)

Microscopic spores:
spores 4.5-5 x 3.5 microns, narrowly elliptic to obovate in face and side views, apiculus obscure, oblique, colorless, guttulation [droplets] obscure; basidia 4-spored, 18-23 x 6-7 microns, clavate, colorless to slightly yellowish in KOH, sterigmata aculeate, about 3-3.5 microns long; cheilocystidia only slightly wider than basidia and difficult to demonstrate, 12-24 x 7-10 microns, clavate, spheropedunculate, occasionally cylindric, (Isaacs), spores 4-5 x 2.5-3.7 microns (Moser)

Spore deposit:
[presumably a dark shade of brown]

Notes:
In addition to the A. purpurellus report from WA by Isaacs(1), a collection from BC by Paul Kroeger was deposited at University of British Columbia. Kerrigan(3) does not mention this species - he does mention a destroyed collection as "the only lilac- or violet-colored Agaricus [italicized] I have seen in North America" but does not assign a name to it. It is also found in Europe.

EDIBILITY

yes, but too easy to confuse with poisonous Inocybe species, (Chariton)