in botany, a genus of the monoecia polyandria clas. The calyx of both male and female consists of four leaves, and none of them have any corolla: the male has eight stamens, and the female four pistilla; and there are four naked seeds. There are two species, both natives of Britain, viz., the spicatum, or spiked water-milfoil; and the verticillatum, or verticillated milfoil.