Gassy Webcap

Description

The gassy webcap is a large mushroom with a cap 4–14 cm across, violet and silky-shiny in young fruiting bodies, fading with time to ochre or rusty brown. The cap is often cracked, especially in dry weather. The gills are pale ochre at first, then rusty brown. The stem is thick, bulbous at the base, violet, with a rusty ring or zones left by the cortina. Its rusty-yellow flesh with a bitter taste and an unpleasant, goat-like or fruity smell is characteristic.

It grows from August to October on the ground in coniferous forests, preferably on poor, acidic soils, e.g. in mountain spruce forests and in pine forests. In Poland it is fairly common, and rare in deciduous forests.

What mainly distinguishes it from other violet webcaps is its yellow or saffron flesh, which is not violet, and its rusty-brown gills. Many webcaps are poisonous, and some are deadly poisonous, so you should not collect any violet-coloured mushrooms unless you are certain of the species.

Identification features

Cap

Diameter 4–14 cm; in young fruiting bodies spherical to convex with an inrolled margin, later expanded, sometimes with a broad umbo. Colour pale violet to lilac, silky and shiny, with a silvery top; it quickly fades to greyish yellow, ochre or rusty brown. Surface dry, felty towards the margin; in dry weather the margin and cap often crack radially, and later the surface may break into fine scales. Rusty-brown or brownish remnants of the cortina hang from the margin, and white fragments of the veil may cling to the surface like scabs.

Hymenophore (underside of the cap)

Gills fairly crowded, thick, broadly adnate, often slightly notched, 7–15 mm wide. In young fruiting bodies pale ochre or slightly dirty violet, then yellowish brown, in mature ones rusty brown, dusted with spores; edge paler, crenate.

Stem

Height 5–12 cm, thickness 1–5 cm; strongly bulbous at the base in young fruiting bodies, club-shaped in mature ones, spongy-filled inside. Surface violet, for a long time vivid violet in the upper part above the cortina, gradually fading from the base. Cortina pale pinkish violet, later rusty brown from the spores, forming a distinct ring or zones; the lower part of the stem is covered by a whitish, boot-like sheath that leaves vertical zones.

Flesh

Thick, at first dirty yellowish, later saffron-yellowish to yellowish brown; never violet, except at the top of the stem and at the base, where it is dirty violet. Smell unpleasant, goat-like or fruity (descriptions differ); taste strongly bitter, especially in young fruiting bodies. The flesh should not be tasted.

Spore print and spores

Spore print rusty brown. Spores ellipsoid, 8–9 × 5–5.5 µm, covered with fine warts or dots.

Habitat and distribution

Ecology. Mycorrhizal fungus; grows on the ground in coniferous forests, especially on poor, acidic substrate (siliceous, non-calcareous), e.g. in mountain spruce forests and dry pine forests. Rare in deciduous forests. Absent on calcareous substrate.

Distribution. Northern temperate zone: North America, Europe, Japan. In Central Europe locally common, in Poland fairly common. Not legally protected in Poland.

Fruiting. From August to October (in North America from August to September, on the west coast somewhat later).

What can it be confused with?

• Cortinarius violaceus (violet webcap) — The whole fruiting body, including the flesh, is dark violet; the cap is scaly. In the gassy webcap the flesh is saffron-yellowish, and violet occurs only on the surface and at the top and base of the stem.
• Cortinarius camphoratus (goat cheese webcap) — Gills pale violet, quickly turning rusty; stem longer, with flesh fading at the base; spores longer, warty, 8.5–11 × 5–6 µm; smell sharp, resembling rotting potatoes.
• Cortinarius muricinus — Cap consistently violet or turning rusty from the centre towards the margin; gills blue at first, dirty cinnamon in older ones; stem violet-lilac; spores much larger, 13–15 × 7–8 µm.
• Cortinarius alboviolaceus (pearly webcap) — Fruiting body paler, silvery whitish violet; it is one of the many violet-tinged webcaps of this genus.
• Cortinarius odoritraganus — A rare species with lilac colouring, mentioned as similar to the gassy webcap; the differences require microscopic examination.

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

• The epithet traganus and the Polish name “wonny” (fragrant) refer to the distinct smell; the old Polish names are zasłonak koźli (goat webcap) and zasłonak brodaty (bearded webcap).
• Described by Elias Magnus Fries in 1818 as Agaricus traganus; in 1838 Fries transferred it to the genus Cortinarius.
• Schaeffer's original illustration from 1774, designated as the lectotype, was a mixed one, so in more recent times an epitype was designated: a collection from a dry pine forest in Sweden from 1988.
• The English name “gassy webcap” refers to the strong smell of the fruiting body.