Mythology & Beliefs: Heliades In Greek and Roman Mythology, Heliades were daughters of Helios; mourned for Phaëthon and were changed to poplar trees.
Heliadae in Greek and Roman Biography and Mythology
and HELIADES (Ἡλιάδαι and (*Hlia/des), that is, the male and
female descendants of Helios, and might accordingly be applied
to all his children, but in mythology the name is given
particularly to the seven sons and the one daughter of Helios
by Rhode or Rhodos. Their names are, Cercaphus, Actis,
Macarcus, Tanages, Triopas, Phaeton, Ochimus, and Electryone.
These names, however, as well as their number, are not the
same in all accounts. (Diod. 5.56, &c.; Schol. ad Pind. Ol.
7.131, &c.) It should be observed that the sisters of Phaeton
are likewise called Heliades. (Ov. Met. 2.340, &c.; Apollon.
4.604.) - A Dictionary of Greek and Roman biography and
mythology, William Smith, Ed.
Heliades in Wikipedia
In Greek mythology, the Heliades ("children of the sun") were
the daughters of Helios, the god who drove the sun before
Apollo. According to one source, there were three: Aegiale,
Aegle, and Aetheria. According to another source, there were
five: Helia, Merope, Phoebe, Aetheria, and Dioxippe. The
fourth or sixth Heliades was a son called Helias. Their
possible brother, Phaëton, died after attempting to drive his
father's chariot (the sun) across the sky. He was unable to
control the horses and fell to his death. The Heliades grieved
for four months and the gods turned them into poplar trees and
their tears into amber. According to some sources, their tears
(amber) fell into the river Eridanos. According to Hyginus,
the heliades were turned to poplar trees because they yoked
the chariot for their brother without their father helios'
permission. - Wikipedia