Abrac
The roses and lilies are recurring throughout the deck. The Rose of Sharon and Lily of the Valley both symbolically represent Christ in Rosicrucianism. I think for Waite there might also be an implied connection with Shekinah. From his FRC Adeptus Major initiation:
THE PRIESTESS: The Waters of Life are Love. Whosoever wills, let him drink of the Waters of Life freely. I testify that the Rose of Sharon is also that of Shekinah, for the Spirit and the Bride are One, and this is the Life of the Rose.