The genus Cabomba (Cabombaceae) is revised. Five species and three varieties are recognized: C. aquatica, C. palaeformis, C. furcata, C. haynesii and C. caroliniana including var. caroliniana, var. pulcherrima, and var. flavida var. nov. A basic chromosome number of x = 13 is proposed. Special emphasis has been given to pollen and seed morphology as revealed by SEM studies.