Hyperacanthus

Abstract: Genipa in Madagascar currently comprises 11 species of Rubiaceae. These species do not belong in the New World genus Genipa (Gardenieae) but instead should be placed in Old World genera belonging to the tribes Gardenieae and Octotropideae. Six species can be confidently placed in the genus Hyperacanthus (Gardenie ae), and the appropriate new combinations are made. Five species belong to the tribe Octotropideae but can not be unequivocally placed in genera at the present time and consequently no combinations are proposed. Three new types of placentation are recorded in Hyperacanthus, which broaden the morphological characterization of the genus. These placentation types are apparently unique within Rubiaceae and perhaps even within Asterideae. Species descriptions, additional material examined, distribution, ecology and conservation asses sments are given for each of the six new combinations in Hyperacanthus.

Abstract: Hyperacanthus ambovombensis is described as a new species, and represents a new generic record for Madagascar. The affinities of H. ambovombensis to the African species of Hyperacanthus (H. amoenus and H. microphyllus) are discussed.

Abstract: The characterization of Hyperacanthus is discussed and a key to the Gardenieae-Gardeniinae of Madagascar is provided. Hyperacanthus grevei is described as a new species for Madagascar.