Morphology and taxonomy of Baseonema and Batesanthus (Apocynaceae: Periplocoideae)

Baseonema Schltr. & Rendle and Batesanthus N.E.Br. are endemic to tropical Africa. Baseonema has one species and is found in savannah of eastern Africa while Batesanthus has two species, one new, that inhabit moist forests in central and western Africa. Both genera are climbers and have in common fleshy interpetiolar ridges and unique flowers with corolla tube recurvate, bearing, on the curve, a coronal collar formed by fusion of the coronal feet and nectary lobes. No significant floral differences could be detected between the two genera, however, they differ with regard to pollen apertures (Baseonema with (6–)8–10-porate grains, Batesanthus with 4–6-porate grains). In view of the pollen characters and a preliminary molecular study suggesting that the two genera do not share an immediate common ancestry, we continue to treat them as distinct. The external vegetative and floral morphology of the two genera and their species were studied, which enabled us to resolve the question around the number of species to be recognised in Batesanthus. A new species, Batesanthus pseudopalpus, characterised by hairy corona lobes resembling a spider's palpi, was identified and is herewith introduced.