Common bonnet or Nitrous bonnet

Cap 2-6 cm across; in young mushrooms bell-shaped or conical with a sharp central bump, becoming convex with age while keeping the same bump. Color gray-brown, darker to dark gray in wet weather, paler to beige in dry weather. The surface is smooth, with fine radial grooves from the margin to the center (the gills show through). The cap margin is thin and often splits in old mushrooms.

Cap 0.5-1.5 cm across, conical or bell-shaped with a sharp little bump, with radial grooves. Color gray-brown, ash-gray, darker in the center. The surface is smooth, slightly damp in rain.

Gills — whitish when young, turning pinkish with age, moderately crowded, with distinctive cross-veins between them. Attachment to the stem notched (adnexed). Spore print white.

Gills — grayish-white, distant. Attachment notched (adnexed). Spore print white.

Stem 5-12 cm tall, 0.3-0.6 cm thick, long, thin, cylindrical, fragile. Color pale grayish-white above, darker toward the base. The surface is smooth. The stem base is often wrapped in whitish, felty mycelium — a characteristic feature of the species on mossy stumps.

Stem 4-7 cm tall, 0.1 cm thick — very thin, threadlike, fragile. Color grayish-white above, darker toward the base. The surface is smooth. The base often has whitish mycelium.

Flesh thin, watery, whitish, more fibrous in the stem. Does not change color when cut. Smell faint; in some populations slightly mealy or radish-like. Taste mild, with a light mealy note.

Flesh very thin, grayish-white. Does not change color when cut. Smell faint, chlorine-bleach — the main diagnostic feature.

Faint; in some populations with a note of flour (like fresh bread) or radish. Not distinctive enough for a confident ID.

Faint, chlorine-bleach, with a note of household cleaner or freshly sliced cucumber. It comes out when you rub the flesh between your fingers.