| General Information |
| Distribution | Native to North America from Canada to Mexico and Central America.In the Hawaiian Islands,
naturalized on
Kaua`i, O`ahu, Maui, Hawai`i. First collected 1991.
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Habit
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Aquatic perennial herbs 2-15(-20) dm tall, arising from stout, tuberous rhizomes.
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Leaves
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Leaves erect, submerged ones, if present, linear and ribbon-like,
emersed ones with blades sagittate, lateral lobes as long as terminal one, linear or ovate-deltate, 2-20 cm long, 0.5-12 cm wide, terminal lobe deltate to ovate-deltate or linear, 3-25 cm long, 0.7-35 cm wide, apex acuminate to subobtuse, petioles 20-70 cm long.
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Flowers
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Flowers unisexual (and the plants monoecious or dioecious), lower flowers pistillate, upper ones staminate, and usually with some perfect flowers in the middle, or rarely all flowers perfect, scapes few, 15-70(-90) cm long, shorter than or slightly longer than leaves, each with 2-7 verticils of flowers, pedicels 0.5-6 cm long, bracts 2-3 per flower, papery, lanceolate to deltate, 0.5-1(-1.5) cm long, usually gibbous; sepals ovate, 5-10 mm long; petals white, very broadly elliptic, 1-2 cm long, abruptly narrowed into a claw.
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Fruit
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Achenes 2.5-4 mm long, dorsal margin winged, beak stout, extending at a right angle from the body, 0.5-1.5 mm long.
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Chromosomes
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2n = 22
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Contributor
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David Lorence
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