Agaricus californicus

This photo shows a somewhat unusual form of one of the most ubiquitous mushrooms in California. The cap is rarely as broken and crusty as in these samples. Note the yellow staining at the edge of the cap when rubbed. They smell of phenol (an acrid alcoholic odor) and should not be eaten. While not severely poisonous, they can cause diarrhea and vomiting. Beginners will often mistake this species for Agaricus arvensis or campestris. Hopefully, the unpleasant odor that californicus emits when cooked should warn anyone who makes this mistake.