How to tell Agaricus tabularis 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 tabularis is large — from 6 to 15, occasionally up to 20 centimeters in diameter. When young it is hemispherical, with a thick, inrolled margin; with age it spreads wide and becomes almost flat, like a little table. The surface is dry, smooth or finely scaly, white, cream or with a faint brownish tinge in the center; it may slowly turn yellow when touched. The thick, firm cap gives the mushroom a hefty, sturdy look.

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, then darken to chocolate brown and almost black. The spore print is dark brown. Pinkish young gills are the key feature that sets this 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 short and thick, firm, white, 4 to 10 centimeters tall, often tapering downward. In the upper part there is a firm, whitish ring — a remnant of the veil. The stem may turn yellow when touched. There is no volva at the base — an important difference from the poisonous amanitas. The stocky, thick stem holds up the massive cap well.

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, thick and firm; when cut, it slowly turns yellow or slightly brownish. The taste is mild, pleasant and mushroomy. Thanks to its meatiness, the mushroom holds its shape well during cooking. For the table, choose young, firm specimens with unopened gills.

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 and mushroomy, sometimes with a faint aniseed or almond note. If, however, the mushroom smells of ink or carbolic and the stem base turns bright yellow when cut, it is the poisonous yellow stainer, and you must not take it.