曲轴黑三棱 qu zhou hei san leng

Stems emersed, erect, 40-55(-80) cm tall. Leaves 45-65 cm × 4-10 mm, upper flattened, lower keeled or trigonous on abaxial side. Racemes 15-17 cm, basally curved; male heads 4-7, distinctly separated from female ones; female heads 3 or 4(-7), relatively widely separated, sessile or lowest pedunculate. Male flowers: perianth segments linear, 2-2.5 mm, serrate-lobate at apex; filaments 3-4.5 mm; anthers oblong, ca. 1.5 × 0.4 mm. Female flowers: perianth segments broadly spatulate, ca. 3 × 1-1.5 mm, serrate-lobate at apex; ovary attenuate toward base; styles short; stigmas 1.5-2 mm. Fruit broadly fusiform, 5-6 mm. Fl. and fr. Jun-Oct.

Shallow water of lakes, ponds, swamps, and streams. Fujian, Guizhou, Taiwan, Yunnan, Zhejiang [India, Indonesia (Sumatra), Japan, Myanmar, New Guinea].