Elatine orthosperma Düben, E. spathulata Gorski, Elatine hydropiper L. subsp. gyrosperma Fr. and E. triandra Schkuhr var. callitrichoides Nyl. are lectotypified, and an epitype is selected for the lectotype of E. spathulata. The synonymizing of E. spathulata with E. hydropiper is supported. — Flora Nordica Notes 36.