Naiad
in Greek and Roman mythology, one of certain inferior deities, who presided over rivers, wells, springs and fountains, and are represented as young, graceful, and extremely beautiful nymphs, to whom great veneration was paid and sacrifices offered. In zoölogy, one of the Unionidæ. In botany, the order NAIADACEÆ (q. v.). NAIADACEÆ, an order of endogens, alliance Hydrales. It consists of plants living in fresh or salt water. The leaves, which are very cellular, have parallel veins and membranous interpetiolar stipules. Flowers small, often in terminal spikes; the perianth generally of two or four pieces, deciduous or wanting; stamens definite, hypogynous; stigma simple; ovaries, one or more, superior; ovule oblong, erect, or pendulous; fruit dry, one-celled, one-seeded. The naiadaceæ are of low organization. Found in temperate and tropical countries.