Myriophyllum limosum Hectot ex Candolle.

Plants mostly monoecious, rarely with bisexual flowers. Perennation by clavate turions. Stem robustly branched or unbranched, 50-150 cm; internodes often shorter than leaves. Submerged leaves 4-6-whorled, pectinate, narrowly ovate in outline, 3-5 × 1.5-2.5 cm; segments in 10-20 pairs, filiform, 1-2.5 cm. Inflorescence a terminal spike of 4-whorled flowers, 7-20 cm; bracts pectinate or absent. Male flowers: bracteoles lanceolate-lobed; calyx broadly campanulate, ca. 1 mm, 4-parted nearly 1/2 of way to base; petals white or greenish, obovate, 2-2.5 mm; stamens 8. Female flowers: bracteoles pectinate, 1-5 × as long as flower; calyx tubular, shortly lobed; petals greenish or white, minute. Fruit 4-loculed, subglobose, ca. 3 mm; mericarps smooth or sparsely verrucose along margins. Fl. and fr. Apr-Sep.

In its terrestrial form this species may fully develop as small plants, with few leaf segments, and often set fruit better than the aquatic form.

Stagnant waters, lakes, ditches, slow streams, occasionally drying ponds; near sea level to 3500 m. Throughout China [Africa, Asia, Europe, North America].