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.