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Key to Rorippa

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Show caption*© Jared Gorrell, some rights reserved (CC BY-NC), uploaded by Jared Gorrell
1 Plant a submerged aquatic, rooting from lower nodes; leaves of two forms, the submerged pectinately divided, the emergent simple, sometimes lobed; fruit < 2.5× as long as wide; petals white
1 Plant terrestrial or of wet places, not rooting from lower nodes; leaves of one form, pinnately lobed or simple; fruit > 2.5× as long as wide; petals yellow or pale yellow (or absent).
  2 Plant a rhizomatous, colony-forming perennial; petals (2.0-) 2.8-6.0 mm long; siliques 3-15× as long as wide.
    3 Stems branched at the base, decumbent to ascending; leaf sinuses not reaching the midrib, the lateral segments entire to weakly toothed; siliques 3-6× as long as wide
    3 Stems branched in the upper portions, erect; leaf sinuses reaching the midrib, the lateral segments often sharply toothed; siliques 6-15× as long as wide
  2 Plant a taprooted annual or biennial; petals 0-3.5 mm long; siliques either 2-9 (-10)× or 15-50× as long as wide.
      4 Flowers nearly sessile; petals absent; lower fruiting pedicels 0.5-1.5 mm long; siliques (3-) 5.4-8.5 (-10.2) mm long, (1.4-) 1.8-2.6 (-3.3) mm wide, mostly 3-5× as long as wide
      4 Flowers clearly pedicellate; petals present (or absent in R. dubia); lower fruiting pedicels > 4 mm long; siliques 4-20 mm long, either 2-9 (-10)× or 15-50× as long as wide.
        5 Siliques (7-) 10-40 mm long, 15-50× as long as wide.
          6 Siliques straight, (15-) 25-40 mm long, 0.7-0.9 (-1.0) mm wide; seeds uniseriate
          6 Siliques curved, (7-) 10-24 (-30) mm long, 1-1.5 (-2) mm wide; seeds biseriate
        5 Siliques 2.5-12.5 (-20.4) mm long, 2-9 (-10)× as long as wide.
             7 Siliques (5.2-) 8.5-12.5 (-20.4) mm long, (4-) 6-9 (-10)× as long as wide; leaves deeply pinnatifid, the pinnae themselves toothed, lobed or dissected; seeds 0.4-0.5 mm long, 100-150 per silique
             7 Siliques 2.5-9 mm long, 2-5× as long as wide; leaves serrate, lobed, or pinnately dissected, the pinnae (when present) merely toothed; seeds 0.5-0.9 mm long, 20-80 per silique.
               8 Sepals 0.8-1.8 mm long; petals 0.5-1.8 mm long; stems ascending, decumbent, or prostrate, with more than one stem arising from base of plant; [s. IL westward]
               8 Sepals 1.5-2.4 mm long; petals 1.8-2.5 mm long; stems erect, usually arising singly from base of plant; [widespread in our area]
                 9 Leaves hirsute on the lower surface; stems hirsute usually up to the terminal raceme
                 9 Leaves glabrous on the lower surface; stems glabrous or sparsely hirsute