16. Potamogeton octandrus Poiret in Lamarck, Encycl., Suppl. 4: 534. 1816.
南方眼子菜 nan fang yan zi cai
Hydrogeton heterophyllum Loureiro; Potamogeton asiaticus A. Bennett; P. hubeiensis W. X. Wang, S. C. Sun & H. Q. Wang; P. javanicus Hasskarl; P. limosellifolius Maximowicz ex Korshinsky; P. miduhikimo Makino; P. octandrus var. miduhikimo (Makino) H. Hara.
Plants annual or perennial, in fresh water. Rhizome inconspicuously present or absent. Stems filiform, terete, ca. 0.5 mm in diam., sparsely to densely branched; nodal glands absent; dormant buds axillary, narrowly fusiform, with 1-3 acerose leaves. Leaves dimorphic; stipules axillary, convolute, 4-13 mm, membranous, free from leaf base, decaying early, green or greenish brown when dry. Submerged leaves alternate, sessile, linear to filiform, 2-6 cm × ca. 1 mm, 3-veined, lacunae conspicuous along midvein, midvein not thickened toward leaf base, attenuate toward apex in upper 1/4 of their length, apex acuminate. Floating leaves petiolate, usually alternate, approximately opposite just below peduncle; blade opaque, elliptic or oblong to oblong-ovate, 1.5-2.5 cm × 7-12 mm, leathery, 5-7-veined, base rounded, apex acute or obtuse. Spikes densely flowered, with 4 whorls of opposite flowers; peduncles 1-1.5 cm. Carpels 4. Fruit obovoid, 1.5-2.5 mm, abaxial keel indistinct to distinct, obtuse to minutely undulate-toothed, with a short beak to 0.3 mm. Fl. and fr. May-Oct. 2n = 28.
Ponds and channels, usually in slightly acid water. Fujian, Guangdong, Guangxi, Hainan, Hebei, Heilongjiang, Hubei, Hunan, Jiangsu, Liaoning, Nei Mongol, S Shaanxi, Shandong, Sichuan, Taiwan, Yunnan, Zhejiang [Bangladesh, India, Indonesia (Java), Japan (including Ryukyu Islands), Korea, Malaysia, Myanmar, Nepal, New Guinea, Russia, Thailand, Vietnam; Africa, Australia].