Foxfire is a natural phenomenon sometimes visible at night in forests. It's caused by bioluminescent fungi in special conditions—usually on rotting bark. Foxfire is caused by a range of different species of fungi, though Armillaria mellea appears to be the most common source. This particular species emits a bluish-green glow, like glow in the dark toys. I've also come across reports of redish lights, however, which are most probably caused by other species. List of species which may cause bioluminescence: Armillaria mellea, Armillaria ostoyae, Collybia tuberosa (luminescent sclerotia*), Mycena chlorophos (Mycena chlorophanos), Mycena citricolor (Omphalia flavida), Mycena rorida (luminous spores), Omphalotus olearius (Clitocybe illudens, Omphalotus illudens, Jack-o'-lantern), Panellus stipticus (North American, not Eurasian, only), and Pleurotus nidfformis (Ghost Fungus). Source, e.g. sari.ac.uk; note also that Bioluminescence in Fungi says that the "bioluminescent ability occurs in 25 different phyla many of whichare totally unrelated". There are some illustrations of Mycena chlorophos glowing at the Springbrook Research Centre, and Luxgene (at bioart.co.uk) has several illustrations of species that cause foxfire:
http://inamidst.com/lights/foxfireenjoy!
:hi: