Cortinarius britannicus
Cortinarius britannicus is a species of webcap. It is known only from Scotland, where it was found on clay soil among mosses under beech. The species produces small, purplish mushrooms. Along with five other British webcaps, "C. britannicus" was selected by Kew Gardens as a highlight of taxa described by the organisation's staff and affiliates in 2020. Taxonomy. "Cortinarius britannicus" was described in a 2020 research note in the journal "Fungal Diversity" by Kare Liimatainen and Tuula Niskanen. The description was based on a collection made by Dave J. Savage in 2017 in Olrig Wood, Caithness, Scotland . The specific name refers to Britain, as this is where the species was first found. Phylogenetic analysis placed the species in "Cortinarius" subgenus "Telamonia" and section "Bicolores". The species formed a sister group with "C. cystidiobicolor". "C. britannicus" was one of over 150 botanical and mycological taxa described by staff or affiliates of Kew Gardens in 2020. In a year-end round-up, Kew scientists selected ten highlights, one of which was six newly described British "Cortinarius" species: "C. britannicus" described from Caithness; "C. scoticus" and "C. aurae" from the Black Wood of Rannoch; "C. subsaniosus" from Cumbria; "C. ainsworthii  from Brighton; and C. heatherae" from Heathrow Airport. In a press release, Kew identified "Cortinarius" species as "ecologically important in supporting the growth of plants, particularly trees such as oak, beech, birch and pine" and playing "a key role in the carbon cycling of woodlands and providing nitrogen to trees". Description. "Cortinarius britannicus" mushrooms have a cap that is wide and a low convex shape. The cap is a greyish purple and hygrophanous. The edges of the cap have whitish fibrils. The adnex gills are medium spaced. They are brown with paler edges. The stalk is long and thick at  apex. It is cylindrical to somewhat tapering downwards. Silky, whitish fibrils cover a greyish purple base. The stem has a white universal veil, which forms incomplete girdle-like structures on the stem. The gills have no distinct odour. Microscopic characteristics. The almond-shaped basidiospores measure 8 to 9 by 5 to micrometres (μm), averaging 8.6 by 5.6 μm. The spores have a depression above the hilum, and are moderately warty, especially at the apex. The spores are moderately to strongly dextrinoid, meaning that they stain reddish to reddish-brown when Melzer's reagent or Lugol's solution is applied. The  basidia are 26 to 35 by 7 to 10 μm. They are roughly club-shaped, sporting four sterigmata. The flesh in the gills is made up of rusty-brown hyphae. They are moderately covered with spot-like encrustations. The pileipellis surface is pale, consisting of more or less parallel hyphae that are 5 to 13 μm wide with zebra-like incrustations. Lower hyphae are rusty brown, 25 to 30 μm wide, with abundant zebra-like incrustations. Similar species. "Cortinarius" section "Bicolores" contains species that produce similar but much larger mushrooms. "C. britannicus" can be distinguished from other members of the  subgenus by its combination of small-sized, purplish-coloured mushrooms and almond-shaped, medium-sized spores. Ecology. The species is known only from Britain, where it was found on clay soil among mosses under beech ("Fagus"), specifically a European beech.