How to tell Horse mushroom from Deadly fibrecap

The cap is 3-10 cm across, hemispherical to convex in young mushrooms, with a broad umbo in the center; it opens out with age. The surface is silky-shiny, with fine radial fibers and flattened scales. At first the color is whitish, cream or ivory; with age and when touched it slowly turns red — first pinkish, then brick-carmine or cinnamon-red. The reddening is most visible along the cap margin and wherever the mushroom is damaged. This is the key diagnostic feature.

Cap 6-20 cm across; in young mushrooms firmly hemispherical to egg-shaped, the margin often rolled under. Later it becomes convex to flat. Color pure white to cream, with subtle yellowish tints in old mushrooms; spots yellow to ocher when touched. Surface smooth, slightly sticky in wet weather, dry and matte in dry weather. Sometimes with fine fibrous scales in the center.

Gilled hymenophore. The gills are fairly crowded, notched where they meet the stem. In young mushrooms they are whitish-pinkish, with age olive-brown to brick-brown. The spore print is olive-brown or tobacco-colored — typical of the whole genus Inocybe.

Gilled hymenophore — gills free, crowded. When young — grayish-white, with a pinkish tinge, becoming with age dark brown, chocolate-blackish. Spore print dark brown.

The stem is 3-10 cm tall and 0.5-1.5 cm thick, cylindrical or slightly widening toward the base. It's whitish to cream, with a pink or reddish-brick tinge (especially in the lower part). When touched and with age it turns red, just like the cap. The surface is lengthwise-fibrous, with no ring. The flesh of the stem is firm.

Stem 6-12 cm tall, 1.5-3 cm thick, thick, fleshy, cylindrical, slightly thickened at the base. Color white to cream. On the upper part — a large membranous double ring with a characteristic "toothed" lower edge (like a cogwheel) — a diagnostic feature of the species.

The flesh is thick and white; when cut, it slowly turns red (not right away: sometimes only after 30 minutes or more), especially in the lower part of the stem. This is an important way to tell it from most Agaricus mushrooms, whose flesh either doesn't change color or turns yellow (though some wood mushrooms, such as Agaricus silvaticus, also redden, so check the gills and spore print too). The smell and taste of the fresh flesh are pleasant, fruity and sweetish — which is exactly what makes it so treacherous.

Flesh firm, meaty, white; when cut it slowly yellows in the flesh of the cap and upper stem. Does not redden (unlike A. silvaticus). The smell is a distinct anise-almond — a characteristic feature of the species.

Sweet and fruity, with notes of ripe pears or apples — unusual for the genus Inocybe, which usually smells spermatic or musty. This appealing aroma + a reddening white cap + the season when edible white mushrooms are being picked = the perfect trap for a beginner forager. Never rely on smell when identifying this species.

Distinctly anise-almond, fruity — the most characteristic diagnostic sign. It comes out when you rub the flesh between your fingers. This smell is one of the most pleasant mushroom experiences in field foraging.