You might think that Candlesnuff Fungus (Xylaria hypoxylon) got its common name from its physical resemblance to a candle but no!
This tiny fungus is, in fact, bioluminescent – in a very very dark place it can be seen to emit light because, as Pat O’Reilly explains on his First Nature website (one of my go-to places for fungi identification), the phosphorus that accumulates within the mycelium reacts with oxygen and other chemicals in the fungus. Pat goes on to say that you really need night-vision goggles to see such weak luminescence or take a long-exposure image. Must try that some time!
Candlesnuff is an extremely common wood-rotting fungus that can be seen all year round in its various stages of growth. Though the fruiting bodies start out black at the base and white on top, they will eventually blacken all over and, from a single stem, they often develop multiple branches at the top.
Another member of the Xylaria genus is Xylaria carpophila, Beechmast Candlesnuff. It looks very similar to normal Candlesnuff but it is incredibly tiny and only grows on the rotting seeds of Beech trees (known as beechmast).