The poisonous Jack-O-Lantern fungus, Omphalotus olearius (formerly known as either Omphalotus illudens or Clitocybe illudens) is most often found growing in clusters at the base of old, rotting, hardwood tree stumps. Smaller groups may sometimes be found growing from buried roots.
It should be fairly obvious from the image where this fungus gets its common name – it is bright orange, like the pumpkin used to make Jack-O- Lanterns. However, another reason for the common name is not as obvious from this image. This fungus glows in the dark! When viewed at night, an eerie greenish luminescence may be seen emanating from the gills on the underside of this fungus.