Abstract: Hygrophila madurensis (N. P. Balakr. & Subram.) Karthik. & Moorthy is an overlooked endemic swampweed of Tamil Nadu hitherto reported only from the Alagar Hills and Narthamalai, Eastern Ghats. The present report is from outside its type locality and deserves phytogeographical significance. Detailed description, images, ecology and distributional notes are provided.
Fig.:Hygrophila madurensis(N. P. Balakr. & Subram.) Karthik. & Moorthy: A, Flowering twig; B, Calyx; C, Stamens; D, Ovary; E, Capsule; F, Seed close up.