Parallel evolution of aperture numbers and arrangement in the genera koenigia, persicaria and aconogonon (Polygonaceae)

Pollen of 30 specics representing the genera Koenigia, Persicaria and Aconogonon was examined by light microscopy and scanning electron microscopy. Pollen descriptions are given for each genus. Earlier palynological investigations of each genus are listed. Each of the genera is characterized by a particular surface structure (spinulose in Koenigia, semitec- tate reticulate in Persicaria, and with microspinules in Aconogonon), but the number and arrangement of the apertures varies considerably, showing interesting parallels in the three genera. All three genera follow the pollen evolutionary model called ‘successiformy’. A few evolutionary and phytogeographically interesting intermediates between these three genera are discussed.