NAIAS, in botany: A genus of the monandria order, belonging to the dicotylous class of plants; and in the natural method ranking with those of which the order is doubtful. The male calyx is cylindrical and bifid; the corolla quadrifid; there is no filament; nor is there any female calyx or corolla; there is one pistil; and the capsule is ovate and unilocular.