The Kreetassan glowing lichen was a plant species, a lichen native to Kreetassa. (TNG - Waypoint comic: "Mirror, Mirror, Mirror, Mirror")
History[]
When a living mirror duplicated Doctor Beverly Crusher and Lieutenant Worf of the Federation starship USS Enterprise-D during a routine planetary survey in the 2360s, Lieutenant Commander Data speculated the cause might be an automatic biological function. Data compared based his hypothesis on the glowing lichen of Kreetassa. (TNG - Waypoint comic: "Mirror, Mirror, Mirror, Mirror")