3. Vallisneria L., Sp. Pl. 1017. 1753. Gen. Pl. ed. 5. 446. 1754; Benth. & Hook. f., Gen. Pl. 3: 451. 1883; Hartog, Fl. Males. 1(5): 387. 1957.
Submerged, dioecious, stoloniferous, glabrous, short-stemmed, perennial herbs with fibrous roots. Leaves radical, sessile, linear, ribbon-shaped, parallel-sided, entire or faintly dentate, obtuse. Flowers unisexual, female solitary, males numerous. Male spathe ovoid, 3-fid at the tip, shortly pedunculate. Male flowers pedicellate, minute, breaking off and floating on the water surface; sepals 3, ovate or oblong-ovate, petaloid; petals 3, minute or absent; stamens 1-3, anthers didymous; pistillode absent. Female spathe tubular, bifid on long slender peduncle that spirally coils after fertilization. Female flower: sepals and petals as in the male; ovary inferior, sessile, linear, unilocular with 3 parietal placentae; styles 3, each 2-lobed with hairs on the innerside; staminodes 3, each bifid. Furit linear, cylindric, 5-10 cm long, included within the spathe. Seeds oblong to fusiform, with membranous testa.
A genus with 2-3 species, distributed in tropics, subtropics and warm temperate regions in the Old as well as in the New World. Represented in Pakistan by the following species.