Common Name: WATERWEED FAMILY
Habit: Annual, perennial herb, aquatic, freshwater or marine, glabrous or hairy; monoecious, dioecious, or flowers bisexual. Leaf: basal, alternate, opposite, or whorled, generally sessile, generally +- sheathing at base. Inflorescence: axillary, terminal, or scapose, cyme or flowers 1, subtended by +- sheathing, entire or lobed bract; staminate flowers sometimes deciduous, free-floating. Flower: generally radial; perianth 0 or tube 0 or elongate, peduncle-like in flower; sepals (0)3(4), green; petals (0)3(4), white or not; stamens (0)2--many, generally in 1+ series; ovary inferior, chamber 1 or falsely 6--9, placentas parietal, ovules 1--many, style lobes generally 3, linear, lobed or notched. Fruit: achene or berry-like and dehiscing irregularly, linear to spheric, submersed.
Genera In Family: +- 17 genera, +- 130 species: worldwide; some cultivated for aquaria, others noxious weeds. Note: Ottelia alismoides (L.) Pers. is a possibly extirpated alien.
eFlora Treatment Author: Robert F. Thorne, C. Barre Hellquist & Robert R. Haynes
Scientific Editor: Thomas J. Rosatti.

Habit: Perennial herb, rooting at nodes, submersed; dioecious or some flowers bisexual. Stem: slender, generally branched. Leaf: often 2 per node proximally, 3--7 distally, sessile, minutely serrate, midrib abaxially +- smooth. Inflorescence: axillary, sessile or not; flower 1; bract generally notched. Staminate Flower: floating, deciduous or not; perianth tube elongate, slender, peduncle-like; stamens 3--9. Pistillate Flower: floating; perianth tube elongate, slender, peduncle-like; style slender, stigmas 3, lobes 0 or 2. Fruit: cylindric to ovoid. Seed: several, smooth.
Etymology: (Greek: of marshes)
Unabridged Reference: St. John, 1965 Rhodora 67:1--35, 155--180