1. Zannichellia palustris Linnaeus, Sp. Pl. 2: 969. 1753.
角果藻 jiao guo zao
Pelta palustris (Linnaeus) Dulac; Zannichellia palustris subsp. pedicellata (Wahlenberg & Rosén) J. D. Hooker; Z. palustris var. pedicellata Wahlenberg & Rosén; Z. pedicellata (Wahlenberg & Rosén) E. M. Fries.
Stems 3-20(-50) cm, 0.3-0.5 mm in diam. Leaves 2-10 cm × 0.3-0.5 mm, apex acuminate; sheaths usually free from leaf base, stipuliform, membranous, evanescent. Anthers 0.6-1 mm; filaments ca. 3 mm. Carpels usually 3 or 4. Fruitlet often curved, reniform to semilunate, 2-2.5 mm, abaxially remotely cristate-dentate, long beaked. Fl. and fr. spring to autumn. 2n = 12, 24, 28, 32, 36.
Fresh or brackish water. Anhui, Hebei, Heilongjiang, Hubei, Jiangsu, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Taiwan, Xinjiang, Xizang, Zhejiang [cosmopolitan].
The specimens with stigma obliquely peltate, fruitlets reniform, and pedicel 4-6 mm are described as Zannichellia palustris var. pedicellata. But specimens from China are variable in the shape of the stigma, characters of fruit, and degree of stipitation. Because of this, the plants are here regarded as forming a single variable species.