(Fomitopsis officinalis, Polyporus officinalis, or Fomes laricis), a fungus of the family Agaricaceae that parasitizes the trunks of larches, nut pines, and sometimes other conifers. The perennial fruiting body is hoof-shaped, becoming almost cylindrical as it ages; it is massive, measuring up to 60 cm long and 20 cm wide. The tissue is white or yellowish. Purging agaric contains agaric acid. The mushroom was formerly used as a laxative and, sometimes, in soaps.