Distribution: Throughout most of the United States
Habitat: Common in slow-moving, often alkaline water, in the Pacific Northwest
Flowers: July - September
Conservation Status: Not of concern
Submerged, dioecious perennials, the stems sparingly branched dichotomously.
Leaves crowded, opposite below and in threes above, 6-15 mm. long and 1.5-2.5 mm. broad.
Staminate flowers solitary in fused bracts on long, slender, pedicle-like structures; sepals 3, greenish, 4 mm. long; petals 3, white, slightly longer than the sepals; stamens 9, the inner 3 on a short tube; pistillate flowers solitary in cylindric, fused bracts on slender, pedicle-like structures up to 15 cm. long; sepals 3, greenish, 2-2.5 mm. long; petals 3, white, equal to the sepals; staminodia 3, tooth-like, 0.5 mm. long; stigmas 3, 2-lobed.
Capsule about 6 mm. long.