Sagittaria graminea
Family: Alismataceae
grassy arrow-head
Sagittaria graminea image
Robert W. Freckmann  
Etymology: Sagittaria: from Latin sagitta, "arrow," because of the leaf shape
Plants: erect or floating, perennial, emergent aquatic
Leaves: flat, usually long and narrow and not arrow-shaped
Flowers: white to pink, 3-parted, 1/3" wide; inflorescence of 2-12 whorls of flowers, usually upper flowers male, lower female; blooms July-Sept.
Fruits: dry, flattened seed with toothed wings, beak 0.4-0.7mm longseed drawing
Habitat: swamps, shallow water; in muddy soil