The tree twin of hazel needs to be related to another tree and the 2 possibilities are witch hazel and beech. The witch hazel was not indigenous when the mandala was entered into the book and is therefor a wrong choice. Beech however is chosen because of the similarities between the trees, which would be the first in this Ogham. Most researchers of the Ogham, including Graves, see this Forfeda as meaning the Sea, which represents that which is other or otherworldly. In the story of Manannan, the sea Manannan are one and the same. The Sea does not represent the god. The sea is the god. Other leave it out of the series.
Most writers associate some attributes to the rune, which are:
Magic and ancient knowledge revealed. Letting go of fixed ideas. Learning from past.Other world contact. Faerie realm.
Past wisdom revealed; use past experience. Death and transformation.