How to tell Agaricus haemorrhoidarius from Yellow stainer

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.

The cap of Agaricus haemorrhoidarius reaches 5 to 10 centimeters across. When young it is hemispherical, opening out with age to convex and flat. The surface is covered with numerous flattened, fibrous scales of dark brown, reddish-brown color on a paler background, radiating from a darker center. The scaly, reddish-brown cap is a characteristic feature of the species.

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.

The hymenophore is gilled. The gills are free, not attached to the stem, and very crowded. Their color changes with age: in young mushrooms they are pale pink or grayish-pink, later darkening to chocolate brown and almost black. The spore print is dark brown. The pinkish young gills set Agaricus apart from the white-gilled poisonous amanitas.

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.

The stem is cylindrical, white, 5 to 10 centimeters tall, with a slightly thickened base. In the upper part there is a prominent hanging ring — a trace of the veil. When cut, the stem flesh, like the cap, quickly turns red. There is no volva at the base — an important difference from the poisonous amanitas.

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.

The flesh is white and, when cut, turns red quickly and vividly, taking on a blood-red tint, especially at the base of the stem — hence the name. The taste is mild and pleasant, with no bitterness and a light mushroomy note. The vivid reddening (not yellowing) is a useful feature that distinguishes this species from the poisonous yellow stainer.

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.

The smell is pleasant, mushroomy, with no sharp notes. But if the mushroom smells of ink or carbolic, and the flesh turns yellow (not red) when cut, it is the poisonous yellow stainer, and you must not pick it.