This slimy, purple mushroom belongs to the genus Cortinarius. With about 2,000 species, it’s the largest genus of mushrooms in the world. Mushrooms in this genus have partial veils, or cortinas – webs of tissue that cover and protect the spore-producing gills. They also have rusty brown spores.
While it is relatively simple to recognize that a mushroom is in this genus, identifying the species can be difficult. Two identical-looking species, C. iodes and C. iodeoides, are found in the Northeast; both are purple and have slimy caps. Mycologists distinguish them by the size of their spores. For those more daring than I, there is a taste test – the slime on C. iodeoides is said to be more bitter than that of C. iodes.
Both species have a mycorrhizal relationship with oaks. The fungi help the tree absorb water and nutrients while the tree provides sugars and amino acids to the fungi. It is estimated that about 85 percent of plants depend on mycorrhizal relationships.