Butter cap or Lyophyllum immundum

Cap 3-7 cm across, hemispherical to convex in young mushrooms, becoming flat and spread out with a small bump in the center with age. Color: gray-brown, mousy brown, earthy gray — muted, with no bright tones. The surface is silky-matte and smooth; in wet weather it is slightly darker.

Cap 3-7 cm across, when young convex, becoming with age flat-expanded with a small umbo in the center (a characteristic shape). Cap skin smooth, with a pronounced buttery-greasy sheen in wet weather — hence the name. Strongly hygrophanous: in wet weather — dark chestnut-brown in the center, lighter toward the margin; when dry — light creamy brown, ochre and faded. The margin is even, thin, often with lengthwise striations where the gills show through.

The hymenophore is made of gills. The gills are crowded, thin, notched where they meet the stem. Color whitish to grayish, becoming cream-ocher with age. Spore print white.

Gilled hymenophore — the gills are adnate or free from the stem, crowded, thin, whitish to cream, turning cream-pink with age. Spore print pale pink to cream — a typical trait of the genus Rhodocollybia ("pink Collybia").

Stem 4-7 cm tall, 0.5-1.2 cm thick, cylindrical, slightly thickened in the lower part. Color whitish to cream, with white mycelial down at the base. The surface is lengthwise fibrous, with no ring.

Stem 3-7 cm tall, 0.3-0.8 cm thick, cylindrical, noticeably thickening toward the base (often with a characteristic "root-like" extension into the substrate). Color ochre-brownish, darker toward the base. Surface smooth, with lengthwise fibers. The stem flesh is tougher and more fibrous than the cap's.

The flesh is thin, whitish to grayish, soft. It does not change color when cut. No pronounced smell.

Flesh thin and tender in the cap, tough and fibrous in the stem. Color whitish to cream. Doesn't change color when cut. Smell faintly mushroomy, taste mild, neutral, normally without bitterness.

Faint, neutral, mushroomy, not distinctive. Do not taste it — its safety status is undetermined.

Faint, neutral, mushroomy, nothing distinctive.