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Species Information
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.
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.
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)
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]
Habitat / Range
open woods(Chariton), gregarious "on needle duff under conifers in open woods", (Isaacs), coniferous woods (Moser), grassy conifer woods (Courtecuisse)
Similar Species
Agaricus diminutivus is more slender and according to Chariton has a stem diameter less than 0.4cm, and a stem length 1.5-2.5 times cap diameter (as opposed to more than 0.4cm and length approximately equal to cap diameter). Agaricus kerriganii (as A. semotus), according to Chariton, has 1) a cap with a fibrillose appearance until very mature (as opposed to having fibrils grouped in small batches to give a slightly squamulose look), 2) background cap color whitish as opposed to light grayish, and 3) a club-shaped stem (as opposed to having an equal to rounded bulbous base), but Isaacs says, "Although A. purpurellus is easily distinguished from A. semotus [now A. kerriganii, editorial addition] by its deep wine-red cap, they are otherwise identical, as far as I know, suggesting that they may be no more than color forms of a single species" (Isaacs, Latin names underlined).
Isaacs(1) (colors from Ridgway(1), Kornerup(2) or Maerz(1)), Chariton(1), Courtecuisse(1)*, Moser(1), Dilly(1), Kerrigan(3) (to say that he does not mention species) References for the fungi
