Vallisneria spiralis, an aquatic plant belonging to the monocotyledonous order Hydrocharidaceae, and native to Southern Europe. It is commonly grown in freshwater aquaria in England for the sake of its long grass-like leaves. These are very transparent, and, under the microscope, exhibit very distinctly the rotation of the cell-sap. The plant is dioecious, the male flowers, which are borne on short stalks at the bottom of the water, breaking off and floating to the surface before the stamens burst, whilst the female flower-bud is carried up on the long, rapidly-growing, spirally-coiled penduncle, from which the plant is named. The spiral coiling adapts it to variations in the water; and after fertilization the peduncle coils up, and the fruit ripens at the bottom.