Bulb fiber (Inocybe napipes)
- Division: Basidiomycota (Basidiomycetes)
- Subdivision: Agaricomycotina (Agaricomycetes)
- Class: Agaricomycetes (Agaricomycetes)
- Subclass: Agaricomycetidae (Agaricomycetes)
- Order: Agaricales (Agaric or Lamellar)
- Family: Inocybaceae (Fibrous)
- Genus: Inocybe (Fiber)
- Type: Inocybe napipes (Onion fibre)
Hat: Umbro-brown, usually darker in the middle, at first conically bell-shaped, later flat procumbent, with a noticeable tubercle in the middle, naked in young mushrooms, later slightly fibrous and radially cracked, 30-60 mm in diameter. The plates are whitish at first, later white-grayish, light brown at maturity, 4-6 mm wide, frequent, at first adherent at the stem, later almost free.
Leg: Cylindrical, slightly thinned above, tuberous thickened at the base, solid, 50-80 mm high and 4-8 mm thick, slightly longitudinally fibrous, one-colored with a cap, only slightly lighter.
Pulp: White or light cream, slightly brown in the stem (except for the tuberous base). The taste and smell are inexpressive.
Spore powder: Light ocher brown.
Disputes: 9-10 x 5-6 µm, ovate, irregularly tuberous surface (5-6 tubercles), light buffy.
Growth: Grows on soil from August to late October in deciduous forests. Fruiting bodies appear singly or in small groups in damp grassy places, most often under birch trees.
Use: poisonous mushroom.