2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/72357We generalize and reprove an identity of Parker and Loday. It states that certain pairs of generating series associated to pairs of labelled rooted planar trees are mutually inverse under composition.27 pages, 2 figures, contains a discussion of Loday's example (i) (math.CO/0403316, v1). Preprint 649 of the Institut FourierCombinatorics05A15, 05C05, 06A10text