3. Najas , Sp. Pl.: 1015 (1753).
Taxon Description
Annual submerged herbs. Roots adventitious. Stems fragile, much branched, rooting at proximal nodes. Leaves submerged, subopposite or pseudo-whorled, sessile, linear, 1-veined, sheaths variously shaped at base, apex acute to acuminate, margin toothed; stipules absent. Plants monoecious or dioecious. Spathes absent in N. graminea and present in N. minor. Flowers actinomorphic, unisexual, minute, solitary or few in leaf axils. Male flowers: perianth 2-lipped, peduncle short elongating at anthesis, membranous. Stamen 1, anther sessile or subsessile, 4-loculed. Female flowers sessile. Ovary 1-loculed; ovules basal, 1; style terminal, 2–4 branched. Achene elliptic-oblong. Seeds fusiform to obovoid without endosperm.
Taxon Statistics
Worldwide 36 species. Two species in Nepal.
Key to Species
1a Stems sparingly branched distally. Leaves ascending. Fruit oblong with fusiform apex ………….……………….………..……….…….………….…… 1. N. graminea
b Stems profusely branched near apex distally. Leaves recurved. Fruit linear-ellipsoid, narrowed and slightly curved at apex…………..………… 2. N. minor
1. Najas graminea Delile, Descr. Egypte, Hist. Nat. 2: 282 (1813).
Caulinia graminea (Delile) Tzvelev; Najas graminea var. delilei Magnus.
Annual submerged herbs, 20–30 cm. Roots adventitious. Stems sparingly branched distally,internodes 0.5–2 cm, without prickles. Leaves ascending, 1–2.9 cm X 0.5–1 mm, sheath 1–1.5 mm wide, apex deeply auriculate, margins minutely serrulate, teeth 40 per side, midvein smooth. Spathe absent. Flowers actinomorphic, unisexual, 1–2 per axil. Male flowers in distal axils, stamen 1; filament 2–3 mm; involucre beaks 4-lobed, 1–1.5 mm; anther 4-loculed, ca. 1.5 mm. Female flowers ca. 3.5 mm. Styles ca. 1 mm, stigmas 2-lobed.Ovary 1-loculed, ovules basal, 1. Fruit an achene, oblong, 1.7–2.5 X 0.4–6 mm, fusiform. Seeds ellipsoid-oblong, 1.5-2.4 mm, areoles hexangular or rectangular.
Distribution: Nepal, Assam-Burma, S Asia, E Asia, SE Asia, C Asia, SW Asia; Europe, Africa and Australasia.
Altitudinal range: 300–2400 m.
Ecology: Ponds, paddy fields, usually in still or slow-moving water.
Flowering: June─July. Fruiting: August─October.
2. Najas minor All., Auct. Syn. Meth. Stirp. Hort. Regii Taur.: 3 (1773).
Najas dichotoma Roxb.
Annual submerged herbs, 11–20 cm. Roots adventitious. Stems profusely branched distally, internodes 0.8–3.5 cm, without prickles. Leaves usually recurved, 0.9–2.9 cm X 0.5–1 mm, sheath 1–1.5 mm wide, apex truncate to auriculate, margin conspicuously serrulate, teeth up to 15 per side, apex acute, midvein smooth. Spathe with a short neck, with brownish spine cells at apex. Flowers 1–2 per axil, actinomorphic, unisexual. Male flowers in distal axils, 2–3 mm, involucre beaks 4-lobed. Stamen 1; filament 1–1.5 mm; anther 4-loculed, ca. 1.5 mm. Female flowers distal to proximal, ca. 2 mm. Ovary 1-loculed; ovules basal, 1; styles 1–1.7 mm; stigmas 2-lobed. Fruit an achene, linear-ellipsoid, narrowed and slightly curved at apex, 2–3 X ca. 0.5 mm. Seeds narrowly ellipsoid, 1.7-2.7 mm, areoles fusiform.
Distribution: Nepal, Assam-Burma, S Asia, E Asia, SE Asia, N Asia, C Asia, SW Asia; Europe and Africa.
Altitudinal range: 700–1000 m.
Ecology: Ponds, lakes, paddy fields and channels.
Flowering: June─July. Fruiting: August─October.