This mushroom with the mouthful of a scientific name is sometimes called the "western flat-top Agaricus." A member of the same genus as the cultivated or "button" mushroom, it is poisonous. The odor of crushed flesh is disagreeable, being described as "creosote-like" or "smelling of library paste." A good field mark is the bright yellow staining that occurs when the base of the stem is nicked, although this also happens with the equally poisonous A. xanthodermus. Photographed at the Hoyt Arboretum in Portland, Oregon.
I used to mushroom hunt on the UBC campus. These mushrooms are common there mostly just inside woods where they meet lawns. I have also found xanthodermis there. I am a mushroom eater, so these are frustrating. They are way more common than any other agaricus in both Vancouver and Victoria. Be careful ! The feet on these usually does not yellow at all and they don't always smell strongly of phenol. My cues are two. First, the dark markings on the caps are gray and dingy. There is usually no brown or tan to them at all. Second, when a bit of skin is scratched off the cap, the flesh underneath stains a light sulfur yellow. Of interest to the daring: Amanita muscaria is found all over the lawns around pine and birch trees on the central campus. I dried a lot while I lived there, but I never had the guts to try them. Now I'm too old! LOL
For those interested (discovered this while updating the entry), the name for this has now been updated to Agaricus deardorffensis
