There are caves where ethereal golden-green lights glow on the ground like emeralds. These light displays are from a luminous moss called Schistostega pennata, known as goblin’s gold, a name that conjures up legends of cave-dwelling creatures. But in daylight, the magical green glow vanishes.
The moss is superbly adapted to life in the dark. When its spores germinate they grow filaments that fan out, scavenging for any faint light they can find. Cells on the surface of the moss are covered with tiny lenses that focus any dim light deep down into the bottom of the cells where chloroplasts move around to harvest any pinpricks of light.
The fluorescent green glow of the moss comes from the chloroplasts as they absorb most of the light but reflect green light, while some of the light focused inside the cell is also reflected out.
The moss can grow into huge colonies in the dark and cover cave floors in a luminous green light. And by growing in dark places, it gains a huge advantage by avoiding competition with other plants that cannot survive in such dingy light.