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Key to Citrus

Rutaceae

Citrus

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1 Leaves trifoliolate; fruit densely pubescent, 3-6 cm long
1 Leaves unifoliolate; fruit glabrous, 4.5-25 cm long (except ca. 2.5-5 cm long in C. japonica, which has glabrous fruit).
  2 Ovary with 3- or 4-locular (rarely 6), each of these bearing 3 or 4 ovules
  2 Ovary with (6-) 7-15 locules, each with many ovules.
    3 Petiole not winged, and lacking an articulation at the juncture with the blade; fruit 15-25 cm long, the rind (exocarp) wider than the pulp (mesocarp)
    3 Petiole winged (except C. reticulata, which sometimes lacks wings entirely), and with an articulation at the juncture with the blade; fruit 4.5-15 cm long
      4 Outer petal surfaces and flower buds pink or purple tinged.
        5 Petiole slightly margined; fruit apex with a prominent nipple
        5 Petiole BLANK; fruit apex with a truncate or depressed, sunken nipple
      4 Outer petal surfaces and flower buds white or cream-colored.
          6 Flowers ≤ 25 mm wide, the petals 8-12 mm long; the fruit ≤ 4(-5) cm wide.
             7 Mature fruit with an apical nipple, the rinds green to yellow
             7 Mature fruit with an apical nipple, the rinds orange
          6 Flowers ≥ 25 mm wide, the petals 14-25 mm long; the fruit 3-15 cm wide.
               8 Petiole wings absent, or only present on one side (subequal to or narrower than the petiole width); rinds (exocarp) 1-4 mm thick, not readily adherent and easily separated from the mesocarp (pulp)
               8 Petiole wing on one side usually subequal to wider than the width of the petiole; rinds (exocarp) 5-12 mm thick, adherent and not easily separated from the mesocarp (pulp).