Butter cap or Spotted toughshank

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.

Cap 5-15 cm across, firm, fleshy, when young convex with an inrolled margin, becoming with age flat-expanded with a slightly wavy margin. Cap skin smooth, dry, matte. Color when young — pure white to cream, with age it becomes covered in characteristic rusty-red spots and marbling, especially in the center and on damaged areas. Old fruiting bodies are cream-ochre overall with reddish streaks.

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").

Gilled hymenophore — the gills are adnate or free, very crowded, thin, whitish to cream, gradually turning reddish when damaged — a diagnostic trait. Spore print pale pink to cream (a typical Rhodocollybia trait).

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.

Stem 5-12 cm tall, 1-2 cm thick, cylindrical, firm, fleshy, thickening toward the base with a "root-like" extension into the substrate. Color white at first, with age covered in the same rusty spots as the cap. Surface smooth or with lengthwise fibers.

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.

Flesh firm, white, marbled. When cut, it slowly (over 10-30 min) turns cream-reddish — oxidation, a characteristic reaction. Smell faintly mushroomy, taste distinctly bitter and astringent — and this is the main reason it's inedible.

Faint, neutral, mushroomy, nothing distinctive.

Faint, neutral, mushroomy, nothing distinctive.