In 1840, English botanist George Gardner was traveling in Brazil. One night, he noticed some boys playing with a strange, glowing object. To his shock, he had encountered a bioluminescent mushroom. It's only taken 170 years to find some more.
Neonothopanus gardneri - which is named after its discoverer, although it was originally misclassified as Agaricus gardneri back in the 1840s - isn't the only mushroom that glows in the dark. But it has proven the most fiendishly difficult to find. After Gardner sent a sample of the fungus to Kew Herbarium in England, it pretty much disappeared completely, and it's now thanks to biologists at San Francisco State that we've finally found some more.
Perhaps part of the reason it disappeared for so long is that no one before now could be bothered to look for it. Researcher Dennis Desjardin explains that he and his colleagues had to tromp through the thick Brazilian rainforests in the middle of the night to find the mushroom - that's the only time when its bioluminescence would be easy to spot - which meant constantly bumping into vegetation and trying desperately to avoid bumping into jaguars or snakes.
Desjardin says that digital cameras were crucial in finding the mushroom, as they can effectively be on constant watch over different parts of the rainforest, and they are capable of picking up on bioluminescence that would be too subtle for the human eye. They eventually found specimens in 2009, and they've spent the last two years comparing these finds with other examples of glow-in-the-dark fungi.
So how and why do these mushrooms glow? Desjardin tackles the first half of that question:
"They glow 24 hours a day, as long as water and oxygen are available. But animals only produce this light in spurts. This tells us that the chemical that is acted upon by the enzyme in mushrooms has to be readily available and abundant."
As for why these mushrooms glow...well, it depends on the particular fungus, and even then scientists aren't always sure. For some, it appears that the glow helps attract insects that can take spores away from the mushroom and deposit them elsewhere. However, some mushrooms don't appear built for that function, so it's possible thy're simply trying to attract the enemies of insects that would otherwise eat them...which, considering the insects only found them in the first place because of their weird glow, seems an awfully convoluted bit of adapting on the mushroom's part.