Lactarius xanthogalactus

Lactarius xanthogalactus, commonly known as the yellow-staining milkcap is a poisonous species of fungus in the family Russulaceae. It produces mushrooms with pinkish-cinnamon caps up to wide held by pinkish-white stems up to long. When it is cut or injured, the mushroom oozes a white latex that rapidly turns bright sulfur-yellow. The species is found on the west coast of the United States and grows in the ground in association with hardwood and conifer trees. There are several other "Lactarius" species that bear resemblance to "L. xanthogalactus", but most can be distinguished by differences in staining reactions, macroscopic characteristics, or habitat.
Taxonomy and classification.
The species was first described by American mycologist Charles Horton Peck in 1907.
The specific epithet "xanthogalactus" is derived from the Latin words meaning "yellow" and "milk".
Similar species.
"Lactarius vinaceorufescens" has nearly identical microscopic features to "L. xanthogalactus", but macroscopically it has reddish-vinaceous stains that develop on the cap, gills, and stem. Another lookalike is "L. colorascens", but it may be distinguished from "L. xanthogalactus" by several features: a smaller fruit body; a whitish cap that becomes brownish-red with age and does not spot vinaceous or brown; bitter to faintly acrid latex; and slightly smaller spores. "L. chrysorrheus" is also similar, but it has a whitish to pale yellowish-cinnamon cap with slightly darker spots and grows under hardwoods (especially oak) on well-drained, often sandy soil, and its gills do not discolor or spot vinaceous or brown.
Other superficially similar species include "L. rubrilacteus", "L. rufus", "L. subviscidus", "L. fragilis" and "L. rufulus", but none of these species have the yellow staining reaction characteristic of "L. xanthogalactus".
Habitat and distribution.
The fruit bodies of "Lactarius xanthogalactus" grow scattered or in groups on the ground under conifers and hardwoods between August and January in Washington, Oregon and California.