ABSTRACT
Twenty-six genera of the Boraginaceae are found in Africa. The family is eurypalynous, the pollen displaying a wide range of morphological types, each with an aperture type more or less characteristic of a genus or group of related genera. All pollen grains studied are zono-aperturate. Various types of apertures are recognised on the basis of shape. In Lobostemon and Echium the apertures are long, narrow and somewhat sunken compound colpi. In Lithospermum the colpi are basically rhombic in outline. Anchusa, a genus with one native member in southern Africa, is characterised by the presence of an endocingulum. In Heliotropium, Amsinckia, Cynoglossum, Afrotysonia, Lappula and Myosotis the pollen grains are heterocolpate, the simple apertures (pseudocolpi) often longer than the compound apertures. The Boraginaceae display a variety of apertural sculptural elements on the aperture membranes and at the colpus margins. Myosotis, usually regarded as a member of the tribe Eritrichieae (to which Lappula belongs), is distinguished from all other genera of subfamily Boraginoideae in having contorted instead of imbricate aestivation of the corolla, and nutlets with a very small basal attachment scar. Therefore, although the aperture morphology resembles that of the Eritrichieae, the tribe Myosotideae is recognised. Pollen morphology of Trichodesma supports its transfer from the tribe Cynoglosseae to the tribe Trichodesmeae. The pollen of Ehretia (Ehretioideae) and Wellstedia (Wellstedioideae) is rather similar. Suggestions to raise Wellstedioideae to family status are not supported by palynology.
