House, Alisoun Valentine2016-01-192016-01-192016http://hdl.handle.net/10539/19326A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2015.External pollen grain morphology has been widely used in the taxonomy and systematics of flowering plants. The eurypalynous family Acanthaceae is a notable example of a group where these pollen diversities have proved useful in determining relationships between taxa. However, internal pollen wall features have received far less attention due to the difficulty of examining the underlying exine from which the external sculpturing is derived. Consequently, internal wall features have thus far not been used in formulating existing classifications. A new technique involving precise cross sectioning or slicing of pollen grains at a selected position, using a focused ion beam-scanning electron microscope (FIB-SEM), was used on 39 species of Acanthaceae to examine the internal pollen wall structure and identify features of potential systematic relevance. Five basic internal wall structures were described in this study. The study also showed that similar external pollen wall features may have distinctly different underlying structures.enAcanthaceae.Pollen--Morphology.Pollen--Development.Thesis