6. Vallisneria , Sp. Pl.: 1015 (1753).
Taxon Description
Perennial submerged herbs. Stems stoloniferous. Roots adventitious. Leaves submerged basal, sessile, linear or strap-shaped, slightly sheathed at base, margin minutely serrulate or entire, veins 3–9, parallel. Plants dioecious. Peduncles long, coiled after anthesis. Flowers actinomorphic, unisexual. Male flowers numerous, minute, shortly pedicellate, clustered together on a central column enclosed by a common spathe, each flower finally breaking free and floating on water surface. Spathe ovoid or ovate-conic, shortly pedunculate. Sepals 3, convex, 1.5–4 mm X ca. 1.2 mm, 2 larger than other; petals 2 or 3, minute; stamens 1–3. Female flowers solitary in spathe; spathe tubular, bifid at apex. Sepals 3. Petals 3, minute. Ovary narrowly cylindric or narrowly triangular-cylindric; ovules numerous; styles 3, bifid. Fruit cylindric or triangular-cylindric. Seeds numerous, oblong or fusiform.
Taxon Statistics
Worldwide 14 species, in tropical and subtropical regions. Two species in Nepal.
Key to Species
1a Male spathe ovate-conic, female spathe with short peduncle and do not coils after fertilization………………………………………………..…….…….. 1. V. natans
b Male spathe ovate, female spathe with long slender peduncle that spirally coils after fertilization ………………………………………………………… 2. V. spiralis
1. Vallisneria natans (Lour.) H.Hara, J. Jap. Bot. 49(5): 136 (1974).
Physkium natans Lour., Fl. Cochinch.: 663 (1790); Vallisneria spiraloides Roxb.
Perennial submerged herbs, 4–11 cm. Rhizomes tuberous. Stems 1.5–2 mm in diameter, smooth. Leaves 3.5–6 cm X 3–5 mm, sessile, linear, ribbon-shaped, apex obtuse, entire or inconspicuously serrulate, glabrous, parallel-sided. Male spathe ovate-conic, 1.5–2 cm X 5–10 mm; female spathe tubular, 1-flowered, does not coil spirally after fertilization. Flowers actinomorphic, unisexual. Male flowers numerous, minute, breaking off and floating on the water surface. Sepals 3, strongly convex. Petals 3, minute or absent. Stamen 1; filaments sometimes 2-lobed at apex, with hairs at base. Staminodes 3, bifid in female flower. Sepals 3, greenish purple, 2–4 mm X ca. 3 mm, apex obtuse. Petals white, minute. Ovary inferior, sessile, linear, unilocular with 3 parietal placentae; styles 3, each 2-lobed with hairs on the inner side. Fruit cylindric, 5–30 cm. Seeds narrowly obovoid, 1.5-2 mm long, glandular hairy.
Distribution: Nepal, Assam-Burma, S Asia, E Asia, SE Asia and SW Asia.
Altitudinal range: 200–300 m.
Ecology: Still or running water.
Flowering: October-November. Fruiting: November-December.
Description of flowers and fruit characters is based on the other floras (Qingfeng et al. 2010), protologue text, and digital image of type (BM000958575).
2. Vallisneria spiralis L., Sp. Pl. 2: 1015 (1753).
Vallisneria pusilla Barbieri ex Bertol.
Perennial submerged herbs, 10–16 cm. Rhizomes tuberous. Stems ca. 2 mm in diameter, smooth. Leaves sessile, linear, ribbon-shaped, 5–20 cm X ca. 1 cm, apex obtuse, margin entire or faintly dentate, glabrous, parallel-sided. Flowers actinomorphic, unisexual. Male spathe ovoid; female spathe tubular, bifid on long slender peduncle that spirally coils after fertilization. Male flowers numerous, minute, breaking off and floating on the water surface. Sepals 3, unequal, recurved, ovate or oblong-ovate. Petals 3, minute or absent. Stamens 1—3, filaments sometimes 2-lobed at apex, with hairs at base. Female flowers: sepals 3, greenish, ovate or oblong-ovate. Petals 3, white, minute or absent. Ovary inferior, sessile, linear, unilocular with 3 parietal placentae; styles 3, each 2-lobed with hairs on the inner side. Staminodes 3 in female flower, each bifid. Fruit cylindric, 5–10 cm. Seeds oblong to fusiform, 1.5-3 mm long, testa membranous.
Distribution: Nepal, W Himalaya, Assam-Burma, S Asia, SE Asia, C Asia, SW Asia; Europe and Africa.
Altitudinal range: 100–300 m.
Ecology: Still or running water.
Flowering: October-November. Fruiting: November-December
Leaves are medicinal (Kumar & Srivastava, 2023).
Description of male flowers and fruit and seeds characters is based on the other floras (Qingfeng et al. 2010), protologue text, and digital image of type (P00486693).