Lactarius trivialis, also known as the Slimy Lead Lactarius, is an agaric that has a large fleshy cap that is often spotted or faintly concentrically zoned. It has pale gills and stem, exudes white milk, and grows solitary or in scattered groups on boggy soil under coniferous trees and birches. The fungus is most commonly found in Scandinavia.

Cap smooth, greasy, later depressed in the centre, initially purplish violet with darker zones, and later changing to brownish grey or pinkish beige. The flesh is whitish, thick, and brittle. Gills pale cream, crowded and slightly decurrent. Stem may be quite long, pallid with a tint of cap colour and later often hollow. It has no ring. Spore print pale yellow or cream coloured.

Microscopic Features: The spores are hyaline, roughly spherical or elliptical in shape, smooth or with small warts, and are typically ornamented. They have a length of 8.5-10.5 µm and a width of 7-8.5 µm.

Similar species include Lactarius argillaceifolius, which grows in eastern North America under oaks and has gills that stain and age to a brown colour.

Lactarius trivialis on Wikipedia.