Gasteroid fungi in the context of "Agaricomycotina"

In mycology, a volva is a cup-like structure at the base of a mushroom that is a remnant of the universal veil, or the remains of the peridium that encloses the immature fruit bodies of gasteroid fungi. This macrofeature is important in wild mushroom identification because it is an easily observed, taxonomically significant feature that frequently signifies a member of Amanitaceae. This has particular importance due to the disproportionately high number of deadly poisonous species contained within that family.

A mushroom's volva is often partially or completely buried in the ground, and therefore care must be taken to check for its presence when identifying mushrooms. Cutting or pulling mushrooms and attempting to identify them later without having noted this feature could be a fatal error.

The Agaricales are an order of fungi in the division Basidiomycota. As originally conceived, the order contained all the agarics (gilled mushrooms), but subsequent research has shown that not all agarics are closely related and some belong in other orders, such as the Russulales and Boletales. Conversely, DNA research has also shown that many non-agarics, including some of the clavarioid fungi (clubs and corals) and gasteroid fungi (puffballs and false truffles) belong within the Agaricales. The order has 46 extant families, more than 400 genera, and over 25,000 described species, along with six extinct genera known only from the fossil record. Species in the Agaricales range from the familiar Agaricus bisporus (cultivated mushroom) and the deadly Amanita virosa (destroying angel) to the coral-like Clavaria zollingeri (violet coral) and bracket-like Fistulina hepatica (beefsteak fungus).