The Bases of Angiosperm Phylogeny: Palynology

The field of palynology is reviewed in terms of its contributions to angiosperm systematics and phylogeny.Principal pollen characters which are phylogenetically useful at higher taxonomic levels (including aperture type, pollen wall architecture, pollen-unit, polarity, symmetry, shape, and grain size), and their evolutionary trends are examined.Many palynological characters and concepts are subjected to re-examination, particularly in an evolutionaryphylogenetic context.An attempt is made to show how pollen characters correlate with various higher categories of the Takhtajan and Cronquist systems of angiosperm classification and to outline certain phylogenetic trends observed in the pollen of different groups of angiosperms.With some exceptions, pollen morphology is consistent with the levels of relative advancement and the relationships postulated in the Takhtajan and Cronquist systems.Angiosperm pollen grains are clearly divisible into two fundamentally different types (each with its own derivatives ) : heteropolar, bilateral, boat-shaped monosulcate pollen versus isopolar, radiosymmetric, globose tricolpate pollen."Gymnospermous" monosulcate pollen and derivative types (ulcerate, disulculate, etc.) characterize both the putatively primitive dicotyledonous subclass Magnoliidae and the monocotyledons.The six non-magnoliid dicotyledonous subclasses, on the other hand, are characterized by tricolpate pollen and derivative types (tricolporate, triporate, rugate, etc.).Relatively primitive tricolpate pollen is retained by many Ranunculidae, 1J.