线叶黑三棱 xian ye hei san leng

Stems floating, 30-50 cm, slender. Leaves floating, 25-40 cm × ca. 4 mm, flattened. Racemes 6-16 cm; male heads 2-4; female heads 2-4, relatively widely separated, sessile or lowest 1 or 2 pedunculate. Male flowers: perianth segments spatulate to obtriangular; filaments ca. 5 mm; anthers elliptic, 1-1.2 × ca. 0.5 mm. Female flowers: perianth segments linear to spatulate, serrate-lobate to parted; ovary fusiform, attenuate toward base and forming a short stalk; styles ca. 2 mm; stigmas narrowly elliptic. Fruit fusiform to elliptic, ca. 4 mm. Fl. and fr. Jul-Sep. 2n = 30.

Lakes, streams, swamps; above 1500 m. Heilongjiang, Jilin, Xinjiang [India, Japan; Europe, North America].