E. hexandra: annual; forming small, matted, creeping tufts, often under water, the stems 1/2-2 inches long; leaves small, obovate or oblong, tapering at the base; flowers globular, with three rose-coloured petals scarcely longer than the calyx; seeds numerous, appearing beautifully ribbed and transversely striated under the microscope. - Water Pepper. - Margins of pools under water. Fl. July, August.
E. Hydropiper: annual; differs from the last in having sessile flowers, with four sepals, petals, and styles, and eight stamens, a more deeply divided calyx, and fewer and larger seeds. - Margins of pools and in water. Fl. July, August.