Potamogetonaceae is a family of monocotyledonous flowering plants in the order Alismatales, with a cosmopolitan distribution. The APG system (1998) and APG II system (2003) places it in the clade monocots. Their concept of the family includes the plants sometimes treated as family Zannichelliaceae, but to exclude the genus Ruppia. So circumscribed, the family consists of seven genera (notably Potamogeton), totalling about 90 species of perennial aquatic plants. Their leaf blades can be either f… (More on Potamogetonaceae)