Symbolism, Imagery, Allegory
After Flamineo murders his brother, and the hour of his own death approaches, he meets the ghost of his old pal, Brachiano. Brachiano's ghost is holding a bowl of lilies with a skull set in them, and throws dirt on Flamineo—meaning that he'll be in the grave soon. Flamineo cries out:
What 's that? O fatal! he throws earth upon me.
A dead man's skull beneath the roots of flowers! (5.4)
The skull hidden beneath flowers is a symbol of death lurking within life. Death always waits at the end—it's the awful reality, "the skull beneath the skin" (as T.S. Eliot put it), that always stands behind the appearances of life. Like "The White Devil" in the title, it's an evil hidden behind a false show of pleasantness—a skull hidden beneath flowers, a devil hidden behind a veil of pure white.