Description from Flora of China
Burshia Rafinesque; Enydria Vellozo.
Herbs perennial, aquatic, submerged or shortly emergent, monoecious or dioecious. Stem soft, few to many branched, rhizomatous. Submerged leaves 3- or 4-whorled, rarely alternate, pectinate, ovate to oblong in outline; segments filiform; emergent leaves smaller, sometimes uppermost ones undivided, reducing to bracts of inflorescence. Inflorescence usually emergent, a terminal spike with flowers 4-whorled, or in axils of emergent leaves. Flowers subtended by a primary bract and 2 bracteoles, sessile, usually 4-merous, minute, lowermost ones female, uppermost ones male, sometimes middle ones bisexual. Male flowers: calyx deeply 2-4-lobed; petals 2-4, boat-shaped, often pink; stamens 2-8, epipetalous. Female and bisexual flowers: calyx tube united with ovary; lobes 4, minute; petals minute, often caducous or absent; ovary (2-)4-celled; style absent; stigmas 4, sessile, recurved, plumose, papillose. Fruit a schizocarp, separating into (2-)4 mericarps. Seed 1 per mericarp.
Myriophyllum has economic importance in the purification of water, as feed for pigs, ducks, and fish, and in polishing wood. The plants are used medicinally to reduce fever and as an antidiarrheal.
Myriophyllum aquaticum (Vellozo) Verdcourt (Enydria aquatica Vellozo) is a commonly cultivated, and nearly naturalized, species in Taiwan, characterized as follows: plants dioecious (only female plants known in China); aerial leaves glaucous or light bluish green; all leaves whorled, never entire, pinnately divided with linear segments; bracteoles subulate with 1(or 2) lateral lobes. This species was possibly introduced by the aquarium trade.
About 35 species: aquatic or wet habitats worldwide, mostly in Australia; 11 species (one endemic, one introduced) in China.