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1 Floating aquatic with swollen, inflated stems
..2 Prostrate perennial; leaves with 3-19 leaflets; stipules basifixed; loment articles separated by a joint and also an isthmus; calyx campanulate; [of dry, sandy or of disturbed areas].
....3 Leaflets with 2-4 longitudinal nerves; mature fruit stipe 1.5-3 mm long
......4 Loment sinuses notched relatively symmetrically on either side, to about 2/3-3/4 the width of the segment; [FL peninsula]
........5 Mature fruit stipe 12-25 mm long; corolla (10-) 12-15 mm long; fruit segments 5-7 mm long, 4.5-6.5 mm wide; paired bracts subtending each flower toothed (rarely entire); standard greenish-yellow with distinct dark-red veins; leaflets 6-25 mm long, 2-5 mm wide
..........6 Paired bracts subtending each flower entire (rarely toothed); leaflets 2.5-13 mm long, 1-2.5 mm wide; fruit segments 4-5 mm long, 3.5-5 mm wide
..........6 Paired bracts subtending each flower toothed (rarely entire); leaflets 6-25 mm long, 1.5-4 mm wide; fruit segments 5-6 mm long, 5-6 mm wide