2. Echinodorus Rich. ex Engelm. (burhead)

(Fassett, 1955; Rataj, 1975)

Plants annual or perennial, sometimes with rhizomes. Leaf blades linear to broadly ovate-cordate, sometimes reduced or absent in submerged plants. Venation usually with palmate main veins arching from the base of the midrib and rejoining near the apex, these connected by finer, angled veins running parallel to one another. Inflorescences erect or prostrate racemes with whorled flowers, sometimes with a few branches basally, or reduced to umbels. Whorls of flowers with few to several small bracteoles in addition to the 3 larger bracts subtending the flowers. Flowers perfect. Sepals ovate, persistent. Stamens 6 to many, the filaments longer than the anthers, the anthers basifixed or attached to the top of the filaments near the middle of the anther (versatile). Pistils 10 to many, in several series, forming a dense, headlike cluster on the expanded receptacle. Styles attached to ovaries obliquely. Fruits plump, with several ribs or ridges. Forty-seven species, nearly worldwide, mostly in tropical countries.

In addition to their value as wildlife food plants, several species of Echinodorus are cultivated as ornamentals for water gardens and as aquarium plants.