Summary:
Section Arvenses. The presence of this species in the Pacific Northwest requires confirmation. Features include 1) overall robust stature, 2) numerous small scales on cap that are pallid to buff to pale brown, pale pinkish brown, or fawn-colored, often becoming browner or ruddier with age, 3) flesh that is unchanging or bruising slightly yellow, 4) free, close gills that are whitish then grayish or pinkish, then reddish-brown. then chocolate brown or darker, 5) a stem that is smooth or with a few fibrils or scales in its lower part, 6) an ample, flabby ring with brown floccose patches on its undersurface, 7) a strong odor and taste of almond, 8) growth in compost, manure, or rich soil, and 9) dark brown spore deposit. |There is a history of cultivation of this mushroom from the late nineteenth century, and more recently it has been cultivated in North America under the name Agaricus blazei (which is actually a different species) (Kerrigan(5)). |In eastern North America an Agaricus identified as this species has tawny scales like A. augustus, and a shaggy lower stem, but still has similar spore size. |Isaacs'' description is derived from Kauffman (1918) with microscopic characters from an A.H. Smith manuscript: Isaacs comments, "The report of this species from Washington by Hotson & Stuntz was based on the slender form of Agaricus augustus Fr. Zeller (1933, p. 387), however, gives the correct size for the spores of Agaricus subrufescens so that this species apparently does occur in the Pacific Northwest. I have found no Agaricus corresponding to the diagnoses given above, nor is there any material in the University of Washington mycological herbarium that is similar. The small spores and rounded bulbous stipe base should readily separate this species from other taxa in the group." |Kerrigan(5) gives two characters that may be present for Agaricus subrufescens that are unusual in other Agaricus species: a) "a transient concave shoulder or bell-shape to the pileus as expansion in young pilei begins first near the margin", and b) radially oriented folds or "pleats" of the cap. These features are shown in the Kerrigan(1) illustration. |The description of Kerrigan(3) follows that in Kerrigan(1) in large part - significant differences are noted.

Cap:
(6)8-25cm across, round or marshmallow-shaped becoming convex to flat; "fibrils pallid to buff to pale brown, pale pinkish-brown, or fawn-colored, often becoming browner or ruddier with age", "background white to pinkish-buff, often becoming yellow in age or when bruised"; "dry, smooth but with fine flattened fibrils which may break up into minute scales except at center (but in dry weather sometimes cracking into large warts)", (Arora), (6)10-20cm broad, at first cylindric, cylindroconvex, nearly spherical, or irregular, finally flat; background whitish, becoming pinkish-vinaceous-buff when old, fine scales ruddy-brown, or initially more pallid; dry, at first bald to obscurely or innately fibrillose, typically soon becoming minutely squamulose [fine-scaly], the fine scales sometimes rather remote, appressed to scurfy, about 0.1cm long and broad, blunt or irregular, disc shallowly rimose-squamulose [cracked - fine-scaly], (Kerrigan), 8-18cm across, hemispheric then convex, finally flat, becoming wavy and split on the margin; "silky-fibrillose at first, the fibrillose surface soon breaking up to form very numerous, appressed, pale tawny fibrillose scales, disk reddish-brown and not scaly, sometimes rimose, not striate", (Isaacs)

Flesh:
thick, firm; white, no yellow bruising or only very slight, (Arora), up to 1-2cm, thick; white, unchanging or very faintly yellowish near top of stem; in stem slightly lustrous and fibrous, white, slowly developing sordid to salmon-colored tones in lower part when cut, (Kerrigan), rather thin, soft, fragile at maturity; white, unchanging, (Isaacs)

Gills:
free at maturity, close; "whitish becoming grayish or pinkish, then reddish-brown and finally chocolate-brown or darker", (Arora), free, close, up to 0.8-1cm broad; at first white but soon pink or more flesh-toned, finally dark blackish brown, margin may be slightly pallid, (Kerrigan(1)), free, not very remote, crowded, narrow; at first white, then pinkish, finally blackish brown, edge at first minutely white-fimbriate [white-fringed], (Isaacs)

Stem:
6-15cm x 1.5-4cm, equal or with an enlarged base; "white, but often staining or aging yellow", base often staining yellow to yellow-orange but flesh in base not staining bright yellow when cut; "smooth or with a few fibrils or scales below the ring", (Arora), 8-15cm x 1.5-2.5cm in upper part, 2-4cm wide at base, equal or slightly bulbous, stuffed-hollow becoming hollow, "base shallowly to deeply rooted in soil or organic matter", subtended by copious white mycelial strands several centimeters long and 0.1-0.3cm wide; stem white, becoming somewhat yellowish to tawny when bruised or when old; subglabrous [nearly bald] in upper part, covered in lower part with short, erect, largely deciduous fibrils, (Kerrigan(1)), "white, becoming yellowish when incised, similar to tawny when bruised or in age", (Kerrigan(3)), 7-15cm x 1-1.5cm, widening downward, twice as thick in lower part, varying from club-shaped to more or less abruptly bulbous, stuffed then hollow; white; almost bald above the ring, floccose-fibrillose to subscaly [somewhat scaly] toward base, (Isaacs)

Veil:
"thick, membranous, white, usually with patches (often obscure) on underside", forming a superior skirt-like ring, (Arora), veils forming a thick, broadly flaring, pendant, supramedian, white ring, upper surface nearly smooth, margin thick, double, dentate [toothed] or twice-dentate, or covered below with torn, floccose, cuboidal patches about 0.2-0.4cm square, lower surface very finely striate at first due to separation of fibers from stem surface, later floccose, universal veil also leaving short, erect fibrils on stem below ring that fall off, (Kerrigan(1)), annulus elastic (Kerrigan(3)), "The elastic veil, which usually remains attached to the pileus margin during expansion, stretching while the lower layer breaks up into a large number of small cottony floccules, is a fairly consistent feature of the species", (Kerrigan(5)), ring "very voluminous, reflexed, double, rather distant from the apex of the stem, smooth and white above, with soft, floccose, pale tawny scales below, becoming dark from spores", (Isaacs)

Odor:
strong sweet like almond extract, especially when young, (Arora), strongly almond (Kerrigan(1)), when crushed, strong of almonds, (Isaacs)

Taste:
strong of almond extract (Arora), of green nuts (Isaacs), like almonds or not distinctive (Bessette)

Microscopic spores:
spores 5.5-7 x 4-5 microns, elliptic, smooth, (Arora), spores (5.3-5.6) 6.1 (6.8-7.5) x (4.1) 4.4 (4.5-4.9) microns, elliptic, dark brown, hilar appendix not prominent, germ pore not evident; basidia 4-spored, 15-18 x 6 microns, cylindroclavate, sterigmata 2-3 microns long; cheilocystidia fairly abundant, forming a nearly continuous band, 5-22 x 4-8 microns, ''subglobose, elongate, "dumbbell-shaped", or various, catenulate or not'', (Kerrigan(1)), spores for North American material (4.9)5.4-7.8(8.6) x (4.0)4.2-5.2(5.6) microns, elliptic, size variable, sometimes bimodally distributed, this possible associated with spore-number variation; basidia predominantly 4-spored but frequently 2-spored or 3-spored, (Kerrigan(3)), spores 6-7 x 4-5 microns, elliptic, dark chocolate brown in KOH; cheilocystidia abundant, 8-12 microns in diameter, cells 10-15 microns long and somewhat inflated; no clamp connections seen, (Isaacs)

Spore deposit:
chocolate brown (Arora)

Notes:
Agaricus subrufescens was reported from BC by Lowe and by Davidson, but these reports would need confirmation. Kerrigan(1) gave it as rare for CA. Kerrigan(3) described the species based primarily on California specimens, but fruiting season was given as "during warmer wet weather (late summer, e.g.) into November (Oregon)". It may be that the OR reference represents another author''s observation. Murrill gave the distribution as NY to MI and southward, and Kauffman mentioned these two states.

EDIBILITY

yes, for most people, (Arora, Kerrigan(3))

Synonyms and Alternate Names:
Pholiota fulvosquamosa Peck