LEMNA, in botany, a genus of the monocæcia diandria class. The calix of both male and female consists of one leaf; neither of them have any corolla; the female has one stylus, and the capsule consists of one cell. There are four species, three of which are natives of Britain, viz. the trifulca, or ivy-leaved duck's-meat; the minor, or least duck's-meat; and the polyrhiza, or greater duck's-meat.