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Key to Heteranthera

Pontederiaceae

Heteranthera

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1 Plant producing only sessile leaves, these linear, 1-6 mm wide, > 10× as long as wide.
  2 Inflorescences 1-flowered; perianth yellow, radially symmetrical; [widespread in our region]
  2 Inflorescences 2-10-flowered (opening each day); perianth mauve, bilaterally symmetrical; s. TX near the coast, westwards and southwards]
1 Plant producing linear to oblanceolate sessile leaves, and also petiolate leaves, reniform, orbicular or oblong, 0.7-2× as long as wide.
    3 Inflorescences 1-flowered; perianth either radially or bilaterally symmetrical; leaf blades mostly 1-2× as long as wide.
      4 Base of petiolate leaf blades cuneate to truncate; leaf apex acute to obtuse; perianth radially symmetrical or nearly so; vegetative stems elongating only in water deeper than 5 cm; perianth tube 15-45 mm long
      4 Base of petiolate leaf blades truncate to cordate; leaf apex obtuse to rounded; perianth bilaterally symmetrical; vegetative stems commonly elongating; perianth tube 11-29 mm long
    3 Inflorescences 2-16-flowered (opening each day); perianth bilaterally symmetrical; leaf blades mostly 0.7-1× as long as wide.
        5 Inflorescences 5-16-flowered, the axis elongating well beyond the spathe tip, thus many of the flowers borne well beyond the spathe; perianth lobes lavender to purple; [s. IL, s. IA, se. NE south to MS, LA, and s. TX; rarely adventive eastwards, as in n. AL and c. NC]
        5 Inflorescences 2-8-flowered, the axis mostly enclosed in the spathe, only 0-2 flowers of the flowers borne outside the spathe; perianth lobes white to pale lavender; [collectively widespread in our region].
          6 Second node above the base of the inflorescence < 5 mm long; hairs on the lateral filaments purple; leaves rounded-oval; [Coastal Plain, s. NJ south to ne. NC]
          6 Second node above the base of the inflorescence > 5 mm long; hairs on the lateral filaments white; leaves reniform; [widespread in our region]