Auraicept na nÉces and the Ogham Tracts

The tract does not insist on trees. In the Book of Ballymote text (Calder, 1917) the letters are named 'secundum alios' after Fénius Farsaid's noblest scholars and, by others, after forest trees 'metaphorically'.

George Calder, Auraicept na n-Éces (Edinburgh, 1917), p. 275, translating the Book of Ballymote, fol. 309a

Medieval Irish scholars' primer whose Ogham tract names the ogham letters and links them to trees.

Sources1 source

Primary source

George Calder (ed. and trans.), Auraicept na n-Éces: The Scholars' Primer, being the texts of the Ogham tract from the Book of Ballymote and the Yellow Book of Lecan (Edinburgh: John Grant), 1917, p. 275 (Book of Ballymote, fol. 309a)That the Ogham tract derives the letter-names from trees only 'secundum alios', beside a derivation from the noblest of Fénius Farsaid's twenty-five scholars; that b, birch, stands first because ogham was first written on birch; and the chieftain, peasant and shrub tree groups.
it is from the trees of the forest that names were given to the Ogham letters metaphorically