Key to the Foetid Russulas in North America 
[ Basidiomycetes > Russulales > Russulaceae > Russula . . . ]
by Michael Kuo
Any number of Russula species could be said to have a "foetid" odor. A quick search through Russula literature renders species that smell "of shrimp or crab," "of cooked apples," "of old wine-casks," "rancid, cheesy, or oily," "disagreeable," "odd," and so on. One group of russulas, however, is characterized by a smell that ranges from sweetly waxy or spermatic, to strongly fragrant and reminiscent of maraschino cherries or benzaldehyde. This group, taxonomically speaking, is subsection Foetentinae of section Ingratae in the genus Russula. The key below treats the mushrooms in this subsection, rather than any russula than could conceivably be described as having a foul smell.
The major species among the foetid russulas are fairly easily distinguished without a microscope on the basis of close observation, taste, and odor. However, in a few instances a microscope is probably needed to be sure of identification. As is usually the case in mushroom identification, you will fare much better if you have collected fresh specimens representing several stages of development.
I do not recommend any of the species below for the table. Some are probably edible, but a few are occasionally reported to poisonous. And besides, given the characteristic odors of these mushrooms (and the fact that many of them taste acrid or waxy), they are probably best avoided.
