Summary:
Section Pluteus. Features are 1) a medium-sized, robust, umbonate cap that is whitish with a brownish to grayish center, has small fibrils and scales, may be areolate [cracked like dried mud], and may be viscid, 2) crowded, free, white gills, 3) white stem that may have darker fibrils especially near the base, 4) pinkish spore deposit, 5) sometimes sweet odor, and 6) microscopic characters that include elliptic spores, metuloid pleurocystidia with wall 1.6-2.2 microns thick, the pleurocystidia not numerous, with 2-3 apical hooks, cheilocystidia in most cases spheropedunculate, and absent clamp connections. Justo(4) comment, using the term intermediate cystidia to indicate those near the gill edge, "In contrast to the great variation in external appearance, the microscopic characters of Pluteus petasatus are rather constant and can be helpful for identification. P. petasatus can be separated from other taxa without clamp-connections in the pileipellis by the combination of: basidiospores relatively short and narrow (on average, 6.1-7.0 x 4.2-4.8 um); intermediate cystidia predominantly fusiform and without apical hooks; cheilocystidia usually scattered and not forming a continuous strip; pileipellis with a gelatinous matrix at least in the most external part." (Justo(4), with Latin name italicized and Greek letter mu in place of u in um). Breitenbach(4) give Pluteus patricius (Schulz.) Boud. sensu Singer, Moser as a synonym of Pluteus petasatus (Fr.) Gillet non sensu Rick., and Justo(4) give P. patricius (Schulz.) Boud. as a synonym. But Banerjee(3) describe Pluteus petasatus (Fr.) Gillet and Pluteus patricius (Schulz.) Boud. separately, P. patricius having a brown-squamulose cap rather than a relatively smooth viscid cap, pleurocystidia that are hooked and thick versus unhooked and thin, and cylindric-clavate rather than spheropedunculate cheilocystidia.

Cap:
4-15(20)cm across, convex or becoming broadly umbonate to flat when old; "whitish with a brownish to grayish center or with darker (brown to grayish brown) fibrils or scales", margin usually whitish; usually not viscid, (Arora), 8-20cm across, convex to almost flat when old; "white with grayish tints, usually gray or grayish brown over the often areolate disc"; dry, bald with small, often appressed squamules [fine scales], (Bessette), 4-8(12)cm across, convex to flat, umbonate; pale whitish umber to occasionally off-white; bald, finely radially striate up to center by innate fibrils, "occasionally breaking up into areolate scales", "shiny or subviscid when young, later often dull", sometimes viscid with separable cap cuticle, (Banerjee)

Flesh:
fairly thick and firm; white, (Arora), firm, soft; white, (Bessette), dull white in cap, shiny white in stem, (Banerjee)

Gills:
free at least when old, crowded, broad; "whitish for a long time, then eventually pinkish", (Arora), narrowly free, close at first, subdistant when old, broad; pure white becoming deep pink when old, (Bessette), arcuate, close, 1-2 tiers of subgills; white when young, later pale pink to pink, edges colored as faces; edges even, (Banerjee), free, ventricose, up to 1.5(2.0)cm broad, crowded; "white when young, later pink"; "with even, or white, flocculose edges", (Justo)

Stem:
4-10cm x 0.7-3cm, equal or swollen in upper part or in the middle, firm; whitish or discoloring in lower part when old, sometimes streaked with fibrils, (Arora), 6-8cm x 0.6-1.2cm, equal; "dull white except at the base which may have some mottled brown stains"; dry, bald, may appear furrowed at base, (Bessette), (4.5)7-11(14.5)cm x (0.5)0.8-1.5cm, equal or widening downward, solid; "white, innately brown fibrillose at base", (Banerjee), 3.0-20.0cm x 0.5-2.0cm, cylindric, "with slightly broad base"; white; "smooth or with longitudinal brown or gray-brown fibrils, especially near the base", (Justo)

Veil:
absent

Odor:
mild or radish-like (Arora), not distinctive (Bessette), "strongly sweet and unpleasant, sweet-raphanoid or indistinct", (Justo)

Taste:
not distinctive (Bessette), similar to odor or indistinct (Justo)

Microscopic spores:
spores (5.0)5.6-7.6(8.4) x 3.8-5.4 microns, oblong-elliptic to broadly elliptic, hilar appendix not prominent; basidia 4-spored, (15)20-33 x 5-8.4 microns; pleurocystidia 45-70(90) x 10-14(20) microns, mostly of Pluteus cervinus - type, somewhat narrowly fusoid-ventricose, rigid, wall 1.6-2.2 microns thick, apex with 2-4(5) apical prongs, few with additional 1-2 lateral hooks, all pleurocystidia colorless, cheilocystidia infrequent, 30-65 x 12-18 microns, "mostly sphaeropedunculate, occasionally some fusoid-ventricose"; cap cuticle "a trichoderm made up of mostly colorless or rarely brown, elongate repent hyphae with rounded ends, end cells obtuse- to round-ended"; clamp connections absent on cap cuticle hyphae, (Banerjee), spores 6-10 x 4-6 microns, elliptic, smooth; pleurocystidia with long necks and horns, (Arora), spores 6-8 x 4-5 microns, elliptic, colorless, thin-walled; basidia 4-spored, 25-30 x 7-8 microns, clavate, thin-walled, colorless; pleurocystidia and cheilocystidia frequent, protruding, 50-70 x 13-19 microns, thick-walled, fusiform, usually with 1-3 horns; clamp connections absent, (Bessette), spores 5.5-8.0(9.5) x 3.5-5.5(6.0) microns, elliptic or broadly elliptic, "more rarely oblong", sometimes oval "or slightly constricted in the middle"; basidia 4-spored, 15-35 x 5-12 microns, "clavate, some with median constriction"; pleurocystidia frequent all over gill faces, 45-95 x 10-25(30) microns, metuloid, "fusiform, narrowly fusiform or narrowly utriform with 2-3 apical hooks, some fusiform and without apical hooks (usually entire, sometimes poorly developed), sometimes this later [? latter] type is predominant, some with small lateral hooks", colorless, with up to 3 microns thick wall, intermediate cystidia (near gill edge) "in most collections predominantly fusiform and without apical hooks, often with small lateral hooks, some similar to the pleurocystidia but smaller and/or with thinner walls"; gill edge sterile, cheilocystidia "in most collections scarce and scattered, more rarely forming a well-developed strip", 30-70 x 10-25 microns, "clavate, narrowly clavate or spheropedunculate", colorless, thin-walled; cap cuticle "a cutis or ixocutis", with terminal elements 80-135 x 6-15 microns, individual elements cylindric, "some strongly tapering towards apex", colorless "or filled with brown intracellular pigment", "with thin, smooth walls", "in most collections a gelatinous matrix is present at least in the most external part", with embedded hyphae 2-5 microns wide, "some with irregular outline"; stem cuticle a cutis, hyphae 5-20 microns wide, cylindric, colorless "or with brown intracellular pigment", "with thin, smooth walls"; clamp connections absent on cap cuticle hyphae, in some collections on stem cuticle hyphae but very scarce, (Justo)

Spore deposit:
pinkish to deep flesh-color (Arora), pink (Bessette), "pink to pinkish brown" (Justo)

Notes:
Pluteus petasatus appears on foray lists for BC and WA and its distribution is described as widespread (but infrequent) throughout North America by Bessette(1). There are collections from BC labeled as this species at the University of British Columbia. There are collections from WA, AK, and MT labeled as this species at the University of Washington. It has been reported from ID by Andrew Parker, pers. comm., and it occurs in CA (Desjardin, Justo). Banerjee(3) examined collections from IL, KY, MI, MS, NY, TN. Justo(4), who include Pluteus patricius, Pluteus magnus, Pluteus curtisii, and Pluteus australis as synonyms, examined collections from CA, FL, IL, LA, MA, ME, MI, MO, SC, TN, WI, Argentina, Spain, Russia, Japan, and Papua-New Guinea, and included collections in the molecular study also from ON, Mexico, Czech Republic, and Mongolia.

EDIBILITY

good, and firmer and meatier than Pluteus cervinus, (Arora)

Synonyms and Alternate Names:
Pluteus patricius (Schulzer) Boud.?