An agaric is a type of fungal fruiting body characterized by the presence of a pileus (cap) that is clearly differentiated from the stipe (stalk), with lamellae (gills) on the underside of the pileus. "Agaric" can also refer to a basidiomycete species characterized by an agaric-type fruiting body. An archaic usage of the word agaric meant 'tree-fungus' (after Latin agaricum); however, that changed with the Linnaean interpretation in 1753 when Linnaeus used the generic name Agaricus for gilled mushrooms.
Most species of agarics are classified in the Agaricales, however, this type of fruiting body is thought to have evolved several times independently, hence the Russulales, Boletales, Hymenochaetales, and several other groups of basidiomycetes also contain agaric species. Older systems of classification place all agarics in the Agaricales, and some (mostly older) sources still use "agarics" as a common name for the Agaricales. Contemporary sources now tend to use the term euagarics when referring only to members of the Agaricales. "Agaric" is also sometimes used as a common name for members of the genus Agaricus, as well as for members of other genera, for example, Amanita muscaria is sometimes called "fly agaric".
- "Gilled Mushrooms" at AmericanMushrooms.com
- "Evolution & Morphology in the Homobasidiomycetes" by Gary Lincoff & Michael Wood, MykoWeb.com