XVI International Botanical Congess

Monosulcate more or less columellate, pollen, usually resulting from successive cytokinesis, is systematically and numerically the most widespread monocotyledonous type. The Palmae (Arecaceae) belong to a minority of monocotyledonous families in which simultaneous cytokinesis occurs. Of the six subfamilies comprising the Palmae, successive cytokinesis is almost exclusive within subfam. Calamoideae, and is exclusive in the monotypic Nypoideae, and occurs sporadically in subfam. Coryphoideae and Arecoideae. Otherwise simultaneous cytokinesis is the rule, rather than the exception. Monosulcate pollen can, however, derive from either type of cytokinesis, and is widespread and frequent in all subfam. except Nypoideae, accounting for about 70% of palm taxa. Apart from variants of monosulcate, 13 other aperture types have been described for palms, although they are rare. These additional aperture types can be separated into those associated with successive, and those associated with simultaneous cytokinesis. Examples are shown, and their value in phylogeny discussed. The incidence of similar palynomorphs in the pre Quaternary are considered in relation to the evolutionary history of the Palmae.