Bitter Oyster (Panellus stipticus)
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Panellus stipticus is one of the brightest-glowing bioluminescent mushrooms on Earth. These flat fungi, which look like a collection of tiny fans growing on sticks, are a dull shade of yellow-beige during the day, but they transform into dazzling decorations after dark. Bitter mushrooms, as they're commonly called, hail from the family Mycenaceae and genus Panellus, which it shares with other glowing fungi.
Although Panellus stipticus has a global distribution, only some strains of it—specifically, those growing in certain parts of North America—are bioluminescent. They glow from the gills and mycelia (internal threadlike hyphae), and most prominently during spore maturation.