Brown Roll-Rim

Paxillus involutus, commonly known as the Brown Roll-Rim, is a widespread ectomycorrhizal fungus found in forests and woodlands, often in association with birch, and pine. It has a distinctive brown, velvety cap that is convex when young, but becomes funnel-shaped as it matures, with the edges typically curling inward (hence the name "roll-rim"). The cap surface can vary in colour from yellow-brown to olive-brown. The gills are decurrent, meaning that they run down the stem, and can change from pale to yellowish-brown. When damaged, the gills bruise brown. The stem is sturdy and often the same colour as the cap. Despite its abundance and previously being consumed as an edible mushroom, P. involutus is now known to be highly toxic. Consumption can lead to severe autoimmune reactions and even kidney failure, as it contains a compound that triggers haemolytic anaemia by destroying red blood cells. It remains a crucial organism in forest ecosystems due to its mycorrhizal relationships, helping trees with nutrient uptake while benefiting from plant-derived carbohydrates.