Elfin Gold is another name for cave moss or luminous moss (Schistostega pennata)—a small plant with reflective, somewhat spherical cells at its tips. Native to the Northern Hemisphere, this moss gives off an eerie gold and greenish glow. The luminosity is caused by the reflection of light from the chlorophyll in the filament growing from the plant’s germinating spore. Most often it forms green mats in caves, or cavities in wood, between rocks, or tree roots. In Japan, the plant has been the subject of numerous books, television shows, newspaper and magazine articles, and even an opera. A national monument to this species is located near the coast of Hokkaido, where the moss grows near a small cave.

Some mosses are decomposers that break down the substrata and release nutrients used by complex plants. Mosses also play an important role in controlling soil erosion, providing ground cover and absorbing water. Mosses can also be indicators of air pollution, as under conditions of poor air quality, few mosses can exist. These organisms are also among the first organisms to invade areas that have been destroyed by a fire or volcanic eruption.