Agaricus placomyces

Cap

4-13 cm in diameter, conical to conical-cuboid then convex to broadly convex, subspread at the end, slightly oblong, dry, smooth and pale to dark grey-brown, especially dark at the disc, breaking up into fine appressed fibrous scales , or in patches when dry, often entirely radially semirimose when ripe, on a whitish to pinkish base when moist, fleetingly bright yellow when crushed when young and fresh, margin long curved, sometimes appendiculate with velar remnants

Gills

free, broad, tight, pale at first, briefly pink or not, then gray, chocolate brown at the end, entire bones

Stem

5-12(15) x (0.4)0.8-1.5 cm, subequal, keyed towards base to moderately or strongly bulbous to 2-3.1 cm, inserted into substrate on lower quarter , hollow, finely fibrous-longitudinal appressed, lustrous, white, sometimes becoming yellow when crushed

Partial veil

very elastic, leaving a thin, pendent, supramedial, persistent ring, very large, double, sometimes toothed at the margin, white, underside twisted and becoming brown, sometimes exuding brown droplets when closed, spotted-discolored when dry, or more coarsely twisted and with granular remnants or scales of the general veil, white then yellowish to dark at the margin and during desiccation

Flesh

thick, 5-8(10) mm thick, fairly firm, white, often unchanging or becoming squalid near the stem at maturity. becoming bright yellow in the base of the foot

Smell and flavor

often unpleasant odor, moderately phenol or inky, more strongly in the base of the foot, also rarely disc candy, and indistinct to slightly unpleasant flavor

Spore

dark brown

basidia

cylindrical-keyed, with 4 sterigmata up to 3 µm in length, 15-21 x 6-9 µm

Spores

ellipsoid, smooth, without distinct germ pore and with prominent hilar appendage, (4.5)5-6(7) x (3)3.5-3.8(5) µm, 5.5 x 3.6 µm in medium

Cheilocystidia

quite abundant, often subglobose to ovoid, 11-19 x 8.5-12 µm, often non-emergent

Mode of growth

scattered or gregarious

Ecology

saprotrophic
on deciduous and mixed forest floors, often in polluted areas, small, heavily trafficked woodlots, city lawns, flower beds, disturbed areas in the presence of trees, etc.

Period

July to September

Frequency

occasional

Edibility

toxic

Chemical reactions

- KOH yellow on the cap

Remarks

This agaric exudes yellowish to brownish droplets from the underside of its partial veil, visible when the latter still covers the blades. These droplets, however, may be absent or dried up. In the latter case, the veil is often discolored, the brownish droplets having produced brownish spots.
A. pacillator, a possible species in Quebec, differs in its abruptly bulbous stem, its partial veil without droplets, its unspotted-discolored dry ring, without dark scales at the margin, and its cap ± scaly outside the disc.
A. placomyces is virtually identical to A. molleri which has slightly larger basidiomes. The latest studies by Kerrigan et al (2005) indicated that A. meleagris and A. praeclaresquamosus were synonyms of A. molleri.
A. placomyces is one of the few inedible species of the genus in Quebec.