MAREOTIS (Arabic Mariut)  , the most westerly of the lakes in the Delta of Egypt . On the narrow strip of land separating the lake from the Mediterranean the city of Alexandria is built . (See EGYPT; and ALEXANDRIA.) MARE'S-TAIL, in botany, the popular name for an aquatic herb known botanically as Hippuris vulgaris (natural order Haloragaceae) . It grows on margins of lakes, ponds and similar localities, and has a submerged stout creeping rootstock from which spring many-jointed cylindrical stems bearing numerous narrow leaves close-set in whorls . The minute greenish flowers are borne in the leaf-axils . Like many fresh-water plants it has a wide distribution, occurring in arctic and temperate regions in the northern hemisphere and reappearing in antarctic South America .