Violet Webcap

Description

The violet webcap is a striking fungus with a cap 4–15 cm across, intensely blue-violet in youth with a slight metallic sheen, later dark violet to brownish. The surface is dry, velvety and finely scaly. The gills are dark violet and turn brown with age as the spores ripen. The stem is club-shaped, with a swollen base, just as dark violet, and the flesh is violet and smells faintly of cedar.

It grows from August to October on the ground, most often in deciduous and mixed forests under beech and birch, singly or in small groups. In Poland it is rare and found mainly in the mountains, and on the Red List it is in the "vulnerable" category.

It is distinguished by the very dark, almost black-violet colour of the whole fruiting body and by its brown spore print. In the genus Cortinarius many species are poisonous and some are deadly poisonous, so a dangerous mistake is easy to make. Because of its rarity it is best to observe and photograph it rather than collect it.

Identification features

Cap

Diameter 3.5–15 cm; convex, broadly convex with age, with a broad umbo or flat, with an inrolled margin. Young caps are intensely blue-violet with a slight metallic sheen, dark violet to blue-black, in older specimens brownish with a violet tinge. Surface dry, granular, velvety, covered with fine downy scales; not sticky, at most occasionally slightly greasy. The cap cuticle is usually a trichoderm.

Hymenophore (underside of the cap)

Gills broadly adnate to the stem, broad, spacing from distant to moderately close. Colour from dark violet in young fruiting bodies, through violet-brown, to dark brown in older ones. Gill edges fringed with fine hairs (visible with a hand lens).

Stem

Height 6–18 cm, thickness 1–3 cm, club-shaped, with a distinctly swollen bulbous base (up to about 4 cm). Solid in young fruiting bodies, hollow inside in older ones. Surface scaly or covered with woolly fibrils, dark violet, almost black in dry weather, similar in colour to the cap. In young specimens surrounded by a cortina, which soon disappears; violet mycelium may be present at the base.

Flesh

Violet, darker beneath the cap cuticle and in the stem. Odour faint, pleasant, cedar-like; taste mild, slightly cedar-like. The flesh should not be tasted. Alkalis (KOH) stain the flesh red, acids greenish.

Spore print and spores

Spore print brown to rusty brown. Spores almond-shaped to ellipsoid, rough, finely warted, 11.5–15 × 7–9 µm (descriptions give different ranges). In C. hercynicus the spores are broader and more rounded.

Habitat and distribution

Ecology. Mycorrhizal fungus. In Europe it occurs mainly in deciduous and mixed forests, under beech, birch (including Betula pubescens, B. pendula), aspen, and in Central and Southern Europe also with hazel; rarely under conifers. Coniferous forms (hercynicus) grow under spruce and pine, usually on more alkaline soils, among mosses. Usually on acidic soils; fruiting bodies solitary or in small groups, sometimes in rings, often near rotting wood. The pigment colouring the fruiting bodies is an iron(III) complex with (R)-β-dopa; the fruiting bodies contain about 100 times more iron than most fungi.

Distribution. Northern Hemisphere: Europe, Asia, North America (where it is more often found under conifers), also western Greenland; related species have been described from Central and South America, Australia and Oceania. Nowhere in Europe is it common. In Poland it is rare, found mainly in the mountains; on the Red List of Plants and Fungi of Poland (2006) it is in category V (vulnerable). It is not under species protection in Poland. It appears on lists of threatened species in, among others, Belgium, Germany, Denmark, England and the Netherlands; in Slovakia it is protected.

Fruiting. From August to October (summer–autumn).

What can it be confused with?

• Cortinarius traganus (Polish: zasłonak wonny) — Gills ochre, later rusty brown, flesh saffron-ochre, unpleasant odour of acetylene; it is not violet-black.
• Cortinarius hercynicus (Polish: zasłonak hercyński) — Sometimes treated as a subspecies of the violet webcap; grows under spruce and pine, has broader spores and less massive fruiting bodies.
• Cortinarius cotoneus — Listed as similar; no data on the differences.
• Entoloma bloxamii and Entoloma parvum (Polish: dzwonkówki) — Listed as similar; no data on the differences. Species of the genus Entoloma have a pinkish spore print, not a brown one.
• Lepista nuda (wood blewit, listed in the catalogue as Clitocybe nuda) — It has a pale, pinkish spore print (brown in the webcap), paler gills and no cortina; the flesh is not dark violet. It usually grows in leaf litter, also outside forests.

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

• Described by Carl Linnaeus in 1753 as Agaricus violaceus, one of the few fungal species named in his Species Plantarum.
• It is the type species of the genus Cortinarius; if the genus were split, the violet species would keep this generic name.
• The pigment of the fruiting bodies, an iron(III) complex with (R)-β-dopa, was identified only in 1998; the fruiting bodies contain about 100 times more iron than most fungi.
• It is the only webcap with large cystidia both on the edges and on the faces of the gills, which makes identification under the microscope easier.