GAERTNERA AND PAGAMEA - GENERA WITHIN THE PSYCHOTRIEAE OR CONSTITUTING THE TRIBE GAERTNEREAE - A WOOD ANATOMICAL AND PALYNOLOGICAL APPROACH

The possible alliance between Gaertnera and Pagamea (Rubiaceae-Rubioid eae), two genera from the Old and New World, respectively, is investig ated on the basis of wood anatomy and pollen morphology. Nowadays, the main point of discussion about the taxonomic position of these genera is whether they belong to the Psychotrieae or constitute a tribe Gaer tnereae characterised by their secondarily superior ovary and sheathin g stipules. Both the wood and pollen of the genus pair are found to sh ow specific features absent in other genera of the Psychotrieae, e.g. parenchyma bands in the xylem and endexine thickenings on the polar si tes of the pollen apertures, Nevertheless Gaertnera and Pagamea share many other characters with the Psychotrieae. Wood and pollen convincin gly demonstrate the very close affinity of the two genera. The sister pair differs in so many features from other Psychotrieae, that Gaertne ra and Pagamea should constitute at least a subtribe Gaertnerinae, for mally recognized here. The general lack of profound studies on the aff inities within the very large tribe Psychotrieae makes further comment s on the taxonomic relationships of the Gaertnerinae difficult.