How to tell Yellow stainer from Inky mushroom

Cap 5-15 cm across; in young mushrooms firmly hemispherical to squared-off (a characteristic feature — the "square" young cap), later becoming convex to flat. Color white to cream, sometimes grayish-brown in the center. The most characteristic sign — touching the cap or its margin leaves bright chrome-yellow spots, especially noticeable in young mushrooms. The surface is smooth, slightly sticky in wet weather.

Cap 5-10 cm across; in young mushrooms hemispherical to conical-convex, later convex with a low umbo. Color whitish to grayish, with distinct, radially arranged small gray-brown or blackish-gray scales — a hallmark of the species (unlike the yellow stainer, whose cap is smooth). When touched, the cap yellows to chrome yellow, like the yellow stainer's.

Gilled hymenophore — gills free, crowded. When young — pale pinkish-gray, becoming with age dark brown, chocolate-blackish. Spore print dark brown. The gill color is typical of Agaricus — it doesn't help tell the yellow stainer apart.

Gilled hymenophore — the gills are free, crowded. In young mushrooms — pale pink to grayish-pink, with age they become dark brown, chocolate-blackish. Spore print dark brown.

Stem 5-12 cm tall, 1-2 cm thick, cylindrical, with a pronounced bulbous base (a difference from other Agaricus species, whose stems are more even). Color white. The most important diagnostic sign: when cut, the flesh at the base of the stem and in the bulb is bright chrome yellow, often almost neon, and the reaction is fast (10-30 seconds). On the upper part — a white membranous ring, distinct in young mushrooms.

Stem 5-10 cm tall, 0.8-1.5 cm thick, cylindrical, with a bulbous base. Color white. When cut, the flesh in the lower part of the stem turns bright chrome yellow — just like the yellow stainer, the same diagnostic feature. In the upper part — a white membranous ring.

Flesh firm, white in the cap and upper stem, bright yellow at the base of the stem even when undamaged. When cut, THE BASE OF THE STEM TURNS BRIGHT CHROME YELLOW — the main diagnostic sign. The cap yellows too, but more weakly. The smell is distinct and unpleasant — ink, phenol, medicinal ointment, creosote.

Flesh firm, white, turns bright chrome yellow when damaged, in the lower stem and in the flesh of the bulb. Smell distinct and unpleasant — ink, phenol, pharmacy ointment, creosote.

Distinct and unpleasant, with notes of ink, phenol, medicinal ointment, creosote, printer's ink. It comes out when you rub the flesh between your fingers, especially at the base of the stem. This smell is the most reliable sign: no edible Agaricus smells like this.

Distinctly unpleasant, with notes of ink, phenol and pharmacy ointment — like the yellow stainer. It comes out when you rub the flesh.