The genera Eichhornia Kunth (∼8 spp.), Heteranthera Ruiz et Pav. (∼13spp.) and Pontederia L. (∼6 spp.) have pantropical distributions;Monochoria Presl. (∼7 spp.) occurs in Africa, Asia and Australia;Scholleropsis H. Pers. (1 sp.) occurs in Africa and Madagascar, andHydrothrix Hook. (1 sp.) is endemic to Brazil, occurring mainly inthe northeast region (Hooker, 1887; Cook, 1996). The centre ofdiversity of the family is in the Neotropical region, where four gen-era and about 25 species are found