Agaricus leptocaulis

Cap

(2)5-8.5 cm in diam., acute to hemispherical at first, then convex to spreading, not ombonate if not slightly, with broad ombon, with fibrillose-appressed and scattered scales, light brown to brown hairy, blackening, except to disc, forming fine scabrous scales distally, pale beige, on a whitish ground, becoming lustrous and buff when ripe, slowly fading to yellow when crumpled, margin inrolled at first, sometimes splitting radially

Gills

free, up to 5 mm wide, tight, pinkish then vinous tawny at first, then brown when mature

Stem

3.5-11.5 x 0.8-1.4 cm, equal to subbulbous towards base, slightly rooting, glabrous, narrowly hollow or stuffed, lustrous, white, eventually fading yellow to almost lignicolor

Partial veil

leaving a thin subapical ring, pendent, elastic, smooth above, potentially deeply furrowed at the margin and rough inside, with a thicker neck near the foot, white, remaining pale, or otherwise forming large, thin fragments appendiculates

Flesh

3-5 mm thick, whitish, immutable or becoming sordid to vinous below the disk, white and immutable or becoming slightly yellow towards the base of the foot, slightly vinous in the cavity or the central surface by the bruises and in the apex of the foot

Smell and flavor

indistinct or phenolic odor when dry, and indistinct flavor

Spore

dark brown

Basidia

cylindrical-clavate to tear-shaped, mostly with 4 and often 2 sterigmata, 2-3(3.5) µm long, 15-22 x 5.5-7.5 µm

Spores

ellipsoid, with slightly prominent hilar appendage, without germ pore, dark brown, (4)4.5-5(5.4) x (2.8) 3.2-3.6(3.8) µm, 4, 8 x 3.4 µm on average, Q = 1.41

Cheilocystidia

scattered and common or forming a semi-continuous lamellar ridge and with a few basidia, often shortly clavate to clavate, also cylindrical to subglobose and so sometimes catenulate in pairs, often appressed, (10)15-16(23) x (6)7 -8(9) µm, most cells being basidioid

Pleurocystidia

absent

Pileipellis

in cutis formed of appressed hyphae

Mode of growth

gregarious

Ecology

saprotroph
on mixed forest floor

Period

august to october

Edibility

allegedly toxic

Chemical reactions

- KOH yellow on the cap

Remarks

This agaric is characterized by its slender stature, its silky and pale cap, with dispersed and dark fibrils on a predominantly whitish background, sometimes dark on the disc, its particularly narrow foot, its flesh possibly tinting slightly yellow in the base of the foot or in rhizomorphs, its pendant, elastic ring and its small spores.
The above characters distinguish it from A. deardorffensis.
Its white foot, subequal towards the base, and its immutable velar surface distinguish it respectively from A. placomyces and from A. pocillator.
It can be difficult to separate a smaller, darker form of A. leptocaulis from a larger, paler form of A. placomyces in the field. The use of the microscope becomes necessary.