Split fibrecap

Description

The split fibrecap (rysostrzępiak porysowany) is a small mushroom with a cap 2–8 cm across, conical with a sharp umbo, silky and fibrous, straw-brown to olive. The cap margin is radially split. The gills are olive-grey to dirty olive, and the stem is white, frosted at the top, with no ring. The smell is unpleasant, spermatic.

It grows from early summer to late autumn in deciduous and coniferous forests, by roadsides, in parks and gardens, especially on clay and alkaline soils. In Poland it is common, probably the most frequent of the fibrecaps.

It is poisonous and contains muscarine. Brown, conical mushrooms with a split cap margin are best left in the forest, because they are easily confused with other mushrooms.

Identification features

Cap

Diameter 2–8 cm; conical-convex when young, conical with a sharp umbo when older, sometimes flattened with an umbo. Margin straight, radially split, sometimes with white fibrils of the veil. Surface silky, radially fibrous; colour from olive-lemon to brown (descriptions also give straw, rarely whitish), the top usually darker.

Hymenophore (underside of the cap)

Gills notched where they meet the stem, thin, with a pale edge; colour from lemon-olive to dirty olive (descriptions also give pale grey, turning brownish with age).

Stem

Height 4–12 cm, thickness 0.5–1.5 cm, cylindrical, with a small bulb at the base. Surface white, sometimes with an olive tint, distinctly frosted at the top, fibrous in the lower part; scaly in older fruiting bodies. No ring.

Flesh

White with a satiny sheen. Smell of semen (spermatic), taste indistinct. Do not taste it.

Spore print and spores

Spore print ochre-brown. Spores elliptical-bean-shaped, sometimes with a small beak, occasionally irregular; dimensions are given ambiguously ("8.5–10 – 16 × 5.5–7 µm").

Habitat and distribution

Ecology. Mycorrhizal fungus. Grows in deciduous and coniferous forests, along forest roads, in parks and gardens; prefers clay soil and alkaline soils.

Distribution. Europe, North America, Asia, Australia and New Zealand (native to Europe). Common in Poland, probably the most frequent fibrecap in Central Europe. Not legally protected in Poland.

Fruiting. From early summer to late autumn.

What can it be confused with?

• Inocybe sororia — Listed as similar; detailed differences: no data.
• Tricholoma terreum (grey knight) and Suillus granulatus (weeping bolete) — Confusion with these species has been recorded in Israel; the fibrecap has gills turning brownish and a brown spore print, while the knights have a white spore print. Details: no data.
• Other fibrecaps (Inocybe, Pseudosperma) — Most species of this group contain muscarine; telling them apart requires microscopy. No data.

Never rely on a single feature. If you are not sure — do not pick it; show the mushroom to a qualified mushroom expert.

Interesting facts

• Until 2019 the species was described as Inocybe rimosa or Inocybe fastigiata; the genus Pseudosperma was introduced by Matheny and Esteve-Raventós.
• It has more than 50 Latin synonyms.
• It is probably the most frequent fibrecap species in Central Europe.
• Muscarine from mushrooms of this group was identified in the 1930s.