There are certain times when the woods begin to glow. Sometimes they glow so much that people call the Park Service and ask them to send a hazmat team. What they're actually seeing is foxfire. And although we know how it happens, we don't know exactly why.
The picture above is a lovely example of one instance of the phenomenon known as foxfire. It's the jack-o-lantern mushroom, a cheery orange mushroom during the day, that goes ethereal around the gills at night. Taking a jack-o-lantern mushroom into a dark room and letting your eyes adjust and the delicate light from the underside of the mushroom gives you a beautiful look at the ruffled bottom of the canopy.
The picture to the left is also an image of foxfire, and you can see why it sometimes causes people to think they're at the origin site of the teenage mutant ninja turtles. Although it can be pretty, it's not symmetric, it's not readily identifiable, and it occasionally covers entire forest glades. Less overwhelming, but equally unsettling, it shows up in people's woodpiles. This is the work of the honey mushroom. The body of the mushroom is above ground, but its rootlike structures grow underground and up into rotting wood. On dark nights, it looks like the wood is glowing green.
The reaction is the result of a pigment, luciferin, and an enzyme, luciferase. Combine the two in the presence of oxygen and the luciferase obligingly glues two atoms of oxygen to the luciferin. The reaction produces energy, which is released as light. It's the same reaction that lights up the firefly. Unlike the firefly, the mushroom can't turn the process off and on at will, and so glows all the time. During the day or on bright nights, we already see so much light that we don't notice the dim glow of the foxfire.
Although the luciferin reaction is extraordinarily energy efficient, it has to cost the mushroom energy to dispense so much light. Why, then, do the mushrooms do it? No one quite knows. Some people think they serve as warning signals, the same way bright colors on a beetle warn off predators. Others think that they are actually meant to draw insects to the mushroom, which can help spread the mushroom's spores.
I just like to think that fungi have poetic souls.
Top Image: Noah Siegel
Second Image: Bruce McAdam