Studies on Generic Delimitations on the Four Genera Rotala ammannia, Nesaea and Hionanthera (Lythraceae)- A Historical Survey

A taxonomic resume of the generic concepts involved in Rotala L., Ammannia (Houst.) L., Nasaea Comm. ex Kunth and Hionanthera Fernandes & Diniz, from the time of Linnaeus (1753) to Cook et al. (1974) and detailed descriptions of the four genera, based on gross external morphology and their geographical range, are presented and discussed. The nomenclature and distribution of 30 species undertaken for biosystematic studies are provided. A comprehensive key synthesising characters derived from such multi-directional evidence, is formulated for more rational delimitation of the four genera.