Final answer:
The Heliades were encased in poplar trees as dryads after Phaethon's death, connecting them to the underworld and sacred knowledge.
Step-by-step explanation:
According to some sources, when the Heliades wept following Phaethon's death, they were encased in poplar trees as dryads. The symbolism behind their transformation relates to the nature of the poplar as a chthonic tree, connecting it to the underworld and the mystical. Associating the Heliades' mourning for Phaethon with the poplar tree signifies that, similar to Bacchic initiates who wore crowns made from white poplar twigs, the Heliades also became protectors of sacred and mystical knowledge tied to the afterlife. According to Greek mythology, when the Heliades wept after the death of Phaethon, they were transformed into poplar trees (c) as dryads. The Heliades were the sisters of Phaethon, and in their grief over the tragic demise of their brother, the gods transformed them into trees. The poplar tree, with its distinctive appearance, became associated with this mythological story, and its leaves were often depicted as shimmering like tears.