Significance of follicle anatomy of Apocynaceae

The pericarp structure of Aganosma, Alstonia, Catharanthus sp., Holarrhena, Ichnocarpus, Parsonsia, Strophanthus, Vallaris and Wrightia sp. distinguished into epicarp, mesocarp and endocarp has been used to put forward their taxonomic and phylogenetic importance. Epicarp is single layered in Catharanthus sp., Ichnocarpus, Parsonsia and Vinca, while in the rest of the genera it is multilayered. Mesocarp is parenchymatous which embeds vasculature and non-articulated laticifers. Endocarp is multilayered and thick walled. Dehiscence of the follicle is marginicidal. A comparison table of follicular features of Apocynaceae, Asclepiadaceae and Periplocaceae is furnished and their features are discussed. A taxonomic key based on follicular fruit characteristic to indentify the genera and species is appended