Lactarius resimus or Blackening brittlegill

Cap 8–20 cm across, convex or flat in young mushrooms, then funnel-shaped. The surface is smooth or slightly sticky, white or creamy white, and may have yellowish concentric zones. The margin is inrolled and fluffy, fringed with white hairs — a hallmark of the species.

Cap 8-20 cm across; in young mushrooms hemispherical to flat with an inrolled margin, later becoming funnel-shaped. Color white when young, turning dirty gray, ash-gray, then blackish to anthracite black with age. The cap darkens when pressed — unevenly in young specimens. Surface smooth, slightly sticky in wet weather.

Gills crowded, narrow, decurrent, white or cream. When damaged they release abundant white milk that doesn't change color in the air (unlike some related species). The bitter milk is the reason soaking is a must.

Gilled hymenophore — the gills are attached to the stem, distant and thick, typical of the genus Russula. In young mushrooms — whitish, when damaged they redden to brownish-black, darkening with age to gray, then black. Spore print white.

Stem 3–7 cm tall, 2–4 cm thick, firm, solid (hollow in old mushrooms), cylindrical or narrowing toward the base. White or slightly yellowish in color, smooth. No ring and no volva.

Stem 4-8 cm tall, 2-4 cm thick, thick, fleshy, cylindrical, relatively short. Color white when young, turning gray, then blackish with age. Surface smooth. No ring.

Flesh firm, brittle, white. When damaged it releases plenty of white, hot milk with a very acrid taste. After proper soaking or salting, the acridity disappears completely.

Flesh firm, fleshy, white when young. When cut, a two-phase reaction slowly unfolds (over 5-10 min): first it reddens to wine-red or bright carmine, then after a few more minutes it blackens to anthracite black. This is the classic diagnostic feature of the species. Faint mushroomy smell.

Smell fresh, pleasant, slightly fruity or with notes of fresh flour. The characteristic “milk cap” aroma, familiar to anyone who has ever salted them — unobtrusive and pleasant even when raw.

Faint, pleasant, mushroomy, with no distinctive notes.