Pollen diversity in some modern magnoliids

Pollen morphology is summarized for most families of magnoliids, including unpublished observations. This survey explores the extent to which pollen types and possible evolutionary trends in these basal angiosperms can be linked to the results of recent molecular and nonmolecular cladistic analyses. Particular consideration is given to comparing pollen of the ANITA clades-similar to the magnoliid I group-with the eumagnoliid clade (magnoliid II group) within which the monocots are grouped and which is more closely related to higher dicots (eudicots). I conclude that there are no fundamental differences between pollen of the ANITA and eumagnoliid groups. The ancestral angiosperm pollen grain was probably monosulcate with a distal aperture and a homogeneous or partly granular ectexine and possessed an endexine and a two-layered intine with a channeled outer layer, with the latter probably initially restricted to apertural regions.