12. Potamogeton wrightii Morong, Bull. Torrey Bot. Club. 13: 158. 1886.
竹叶眼子菜 zhu ye yan zi cai
Potamogeton intortusifolius J. B. He, L. Y. Zhou & H. Q. Wang; P. japonicus Franchet & Savatier; P. mucronatus C. Presl (1851), not Schrader ex Sonder (1850).
Plants perennial, submerged. Rhizome terete, slender. Stems simple or rarely sparsely branched, internodes elongated, terete, ca. 2 mm in diam. Stipules axillary, convolute, large and conspicuous, 2.5-5 cm, membranous, free from leaf base. Submerged leaves petiolate; petiole 1.6-14 cm; blade narrowly oblong to oblong-lanceolate, 8-20(-31) × (0.7-)1.4-2(-2.7) cm, 9-13-veined, with a conspicuous midvein, base rounded or cuneate, margin undulate and minutely denticulate, apex mucronate. Floating leaves usually absent, sometimes present, bright green, often with reddish tinge, oblong to elliptic, 5.2-12.5 × 1.2-2.5 cm, 11-25-veined, base cuneate, apex mucronate. Spikes densely flowered, with many whorls of opposite flowers; peduncles 4-7 cm, thickened upward. Carpels 4. Fruit obovoid, 2-3.3 mm, abaxial keels 3, distinct, with a narrowly winglike midvein; beak short. Fl. and fr. Jun-Oct. 2n = 52.
Lakes, rivers, channels, ponds. Anhui, Fujian, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Yunnan, Zhejiang [India, Indonesia, Japan, Kazakhstan, Korea, Laos, Malaysia, Myanmar, New Guinea, Pakistan, Philippines, Russia, Thailand, Vietnam; Pacific islands].
The species here called Potamogeton wrightii was generally treated under the name "P. malaianus," but the type specimen of P. malaianus Miquel is actually P. nodosus.