The myrtle is sacred to the chthonoi, and hence the myrtle-crown belongs to the Mystai of Demeter as well as to the dead
Rohde establishes that myrtle's sacred status derives from its chthonic consecration, making it the definitive plant-symbol shared between mystery initiates and the dead in Greek religion.
, Psyche: The Cult of Souls and the Belief in Immortality among the Greeks, 1894thesis