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|1 Leaves monomorphic, all leaf blades 1-3 cm long, 0.2-2 cm wide; achenes (pistils) 10-20 per head; stamens 6 or 9; petals 1-3 mm long; scapes 5-10 cm tall, erect|
|1 Leaves multimorphic, plants with one or more leaf type (differently shaped emersed, submersed, and floating leaves), usually at least some leaves 5-20 cm long, 3-15 cm wide; achenes (pistils) 40-250 per head; stamens ca. 21; petals 6-12 mm long, scapes 20-120 cm tall, erect or arching/reclining.|
..2 Scapes arching and rooting down at maturity; veins of the sepals papillose-roughened
|..2 Scapes rigidly erect at maturity; veins of the sepals smooth.|
|....3 Stamens 9-15; plants to 70 cm tall|
|....3 Stamens 21; plants to 200 cm tall|