Permanent tetrads originated in two major lines: the xylopioids, corresponding to part of Walker's Fusaea subfamily but excluding Fusaea, with granular structure and a nexine of fused granules; and the annonoids, corresponding to Walker's Annona subfamily, with columellar structure and a complexly foliated nexine. The single grains of Isolona are secondarily derived from tetrads. Sulculate pollen arose in both monosulcate and inaperturate lines. The genus Polyalthia, which has unusually diverse pollen, appears to be polyphyletic. Columellar structure originated in smooth monosulcates with granular structure, leading to the malmeoids, and in forms with larger, irregular granules, in the disulculate Polyalthia group and possibly the annonoids.