What is "psalacantha"

In Greek mythology, Psalacantha was a nymph of the island Icaria. According to Ptolemy Hephaestion, she fell in love with Dionysus and promised to help him win the love of Ariadne on condition that he satisfy her own desires as well. Dionysus refused and Psalacantha went on to advise Ariadne against him, whereupon the god became enraged and changed Psalacantha into a plant known as psalakanthos. Later, he repented and decided to commemorate Psalacantha by having the plant worked into Ariadne's wreath, the one that was changed into the constellation Corona Borealis.