The mushrooms in Agaricus are terrestrial, and have caps that are not brightly colored. At maturity the gills are free or almost free from the stem, and are brown to chocolate brown. The stem breaks away cleanly from the cap. Agaricus species have a partial veil which often forms a ring. The spore print (see bottom illustration) is dark brown.This genus includes some very good edibles (the common "button mushroom" sold in grocery stores is Agaricus bisporus), as well as some mildly poisonous mushrooms; be sure of your identification before experimenting

Identification of Agaricus species often hinges on the bruising reactions of the cap, stem, and flesh--and whether or not the flesh changes color when sliced and exposed to air. One group of Agaricus species "blushes," staining and bruising pinkish or even blood red. Another group stains and bruises yellow. Many (but not all) of the yellow stainers have a strong, phenolic odor, and most of them turn yellow when a drop of KOH is applied. Repeated rubbing of the cap margin will often produce yellow bruising in this group, but the best place to observe the yellow staining is frequently in the flesh in the base of the stem. Most (all?) of the mildly poisonous species belong to the yellow staining group. A third group of Agaricus species does not bruise or stain appreciably-and a few oddballs demonstrate both yellow and reddish staining.