violet webcap

Cortinarius violaceus has a convex (becoming broadly convex, umbonate or flat) cap of 3.5–15 centimetres (1+3⁄8–6 in) in diameter with an incurved margin. It is dark violet to blue-black in colour, and is covered in fine, downy scales. This layer on the cap is known as the pileipellis, which is either classified as a trichoderm—parallel hyphae running perpendicular to the surface and forming a layer 6–22 μm wide—or rarely an ixocutis, a layer of gelatinized hyphae 2–11 μm wide. The cap surface, unlike that of many other Cortinarius species, is neither sticky nor slimy, though it is occasionally greasy. The stipe, or stalk, is 6 to 18 cm (2+1⁄3 to 7 in) tall, and 1 to 2 cm (3⁄8 to 3⁄4 in) thick. Due to its swollen, bulbous nature, the base of the stipe can sometimes be as wide as 4 cm (1+1⁄2 in). The stipe is a similar colour to the cap, and covered in wool-like fibrils; purple mycelium can be present at the base. Younger specimens feature a veil, but this vanishes quickly. The flesh is violet, but darker below the pileipellis and in the stipe. The flesh has a mild taste, indistinctly reminiscent of cedar wood, with a slight, pleasant smell, also reminiscent of cedar wood. The gills are dark violet, changing to a purplish-brown with age. They have an adnate connection to the stipe, and can be very dark in older specimens. …

Cortinarius violaceus is found across North America, Europe and Asia. Although widespread, it is not common anywhere in Europe, and it is listed as endangered in the British Isles. Cortinarius violaceus is a rare component of subarctic areas of western Greenland. In Europe, it grows in deciduous woodland during autumn, especially among oak, birch and beech, but is also found on occasion with conifers. It is also occasionally known from treeless heathland, where it is associated with bracken. The species favours acidic soil. Cortinarius violaceus forms mycorrhizal associations with several species of tree. In this symbiotic relationship, the fungus gains carbon from the plant and supplies it with beneficial minerals. In Nordic countries, its hosts include white birch (Betula pubescens), silver birch (B. pendula), European aspen (Populus tremula) and rarely European beech (Fagus sylvatica). No records of association with oak (Quercus) are known from this region. Brandrud reported that what he described as spp. hercynicus grew with Picea abies, generally in more alkaline soils and along with mosses of the genera Hylocomium and Pleurozium, and, in moister areas, big shaggy-moss (Rhytidiadelphus triquetrus), as well as the buttercup-family shrub Hepatica nobilis. …

Cortinarius violaceus are sometimes considered inedible, and sometimes considered edible, but not choice. Instead, the primary appeal of the species to mushroom hunters, according to Arora, is its beauty. Its similarity to some other (inedible or toxic) webcaps renders it risky to eat. The taste after cooking is reportedly bitter. The colour of C. violaceus hasn't been recorded for conversion into a dye, unlike that of some other Cortinarius species, such as C. sanguineus and C. semisanguineus. The colour is caused by an elusive pigment that has been difficult to isolate; its identity was not known until 1998. This is an iron(III) complex of (R)-3′,4′-dihydroxy-β-phenylalanine [(R)-β-dopa]. It dissolves in water, turning the liquid dark purple before fading to blackish-grey. C. violaceus fruiting bodies contain around 100 times more iron than those of most other fungi. Cortinarius violaceus extract demonstrates an inhibitory activity against cysteine protease.