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Key to Rhexia

Melastomataceae

Rhexia

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1 Anthers 1-3.5 (-4) mm long, straight to slightly curved.
  2 Petals white (rarely pale lavender); anthers (2-) 3-3.5 (-4) mm long, usually longer than the filaments; [pond margins in sw. GA and Panhandle FL]; [section Rhexia]
  2 Petals either yellow or lavender-rose to pink; anthers 1-2.5 mm, usually shorter than the filaments; [collectively more widespread].
    3 Stem internodes with at least some hairs; leaves oblong, linear, or spatulate; petals yellow; [section Luteorhexia]
    3 Stem internodes glabrous; leaves ovate, suborbicular, or widely elliptic; petals lavender-rose to pink; [section Brevianthera].
      4 Calyx lobes blunt to acute; hypanthium densely glandular-pubescent; surface of seeds irregularly ridged; [of s. GA south to s. FL]
      4 Calyx lobes acuminate-aristate; hypanthium nearly glabrous except along the calyx lobes; surface of seeds pebbled; [widespread in the Coastal Plain from se. VA southward to s. FL and west to e. TX, and rarely inland]
1 Anthers 5-11 mm long, distinctly curved.
        5 Stem nodes and internodes glabrous; stem and foliage blue-green; [section Cymborhexia]
        5 Stem nodes and usually also the internodes hirsute; stem and foliage green; [section Rhexia].
          6 Sepal lobes aristate, the awn-tip 0.5-1.5 mm long, and also with flaring, yellowish, stiff hairs 3-5 mm long
          6 Sepal lobes obtuse to acuminate, not aristate, the hairs shorter and not yellowish or stiff.
             7 Leaves 1-5 (-8) mm wide, linear, linear-elliptic, narrowly oblong, or narrowly spatulate.
               8 Leaves twisted at base, borne in a vertical plane; four stem faces subequal, the angles narrowly winged; mature hypanthium neck shorter than body; calyx lobes 1.5-2 mm long; anthers 4-5 mm long
               8 Leaves not twisted at base, borne more or less horizontally; four stem faces markedly unequal, the angle wings inconspicuous or absent; mature hypanthium neck as long as or longer than body; calyx lobes 2-4 mm long; anthers 5-10 mm long.
                 9 Petals lavender-rose, (1-) 1.5-2.7 cm long; mature hypanthium 10-14 mm long, with glandular hairs; marginal nerves of leaf abaxial surface either absent or obscure and discontinuous; anthers 7-10 mm long
                 9 Petals white to pink (-rose-purple), (7-) 0.9-1.4 cm long; mature hypanthium 6-10 mm long, glabrous or sparsely glandular-hairy; marginal nerves of leaf abaxial surface prominent; anthers 5-8 mm long
             7 Leaves (5-) 7-20 (-35) mm wide, lanceolate, elliptic, or ovate.
                   10 Four stem faces at mid-stem markedly unequal, one pair of opposite faces broader, convex, darker green, the narrower pair concave or flat, pale, the arrangement of broader and narrower faces alternating at each subsequent internode.
                     11 Mature hypanthium 6-10 (-11) mm long, glandular-setose; petals 12-15 (-18) mm long, glabrous on the lower surface; anthers 5-8 mm long
                     11 Mature hypanthium (9-)10-15 (-20) mm long, glabrous or glabrate; petals (18-) 20-25 mm long, glandular-hairy on the lower surface (best seen in bud); anthers 8-11 mm long
                   10 Four stem faces at mid-stem about equal, almost flat, the angles sharp or winged.
                       12 Roots tuberous; stem angles at mid-stem conspicuously winged; hypanthium 7-10 mm long, the neck shorter than the body
                       12 Roots not tuberous; stem angles sharp to narrowly winged; hypanthium 10-13 mm long, the neck as long as or longer than the body.
                          13 Hypanthium 7-9 (-10) mm long; petals 8-12 mm long; seeds irregularly ridged, especially along the crest [of KY, TN, and AL westwards, west of the Appalachians]
                          13 Hypanthium (9-) 10-12 mm long; petals 10-25 mm long; seeds papillate, the papillae in concentric lines [of NJ to SC east of the Appalachians]

Key to Rhexia, Alternate Key: based largely on vegetative characters

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1 Stem internodes glabrous.
  2 Stem nodes as well as internodes glabrous, leaf margins entire or remotely low-toothed apically, glabrous
  2 Stem nodes hirsute, leaf margins toothed, the teeth often tipped with hairs.
    3 Longest leaves 1.5 (-2) cm long, ovate or suborbicular
      4 Leaf apex obtuse to acute, margins subentire to blunt-toothed or serrulate, teeth hairs if present shorter than 1 mm
      4 Leaf apex acute to acuminate, serrulate, the teeth tipped with a hair 1 mm long or slightly longer, the margin appearing long-ciliate
    3 Longest leaves > 2 cm long, lanceolate, elliptic, or ovate.
        5 Rhizomes present, roots not tuberiferous or spongy-thickened
        5 Rhizomes absent, roots tuberiferous or spongy-thickened.
          6 Stem leaves gradually reduced upward
          6 Stem leaves gradually lengthening from the base to mid-stem
1 Stem internodes (and nodes) hirsute or glandular-hairy.
             7 Leaves lanceolate, elliptic, or ovate, broadest at or below the middle.
               8 Four stem faces at mid-stem markedly unequal, one pair of opposite faces broader, convex, darker green, the narrower pair concave or flat, pale.
                 9 Mature hypanthium 6-10 mm long, glandular-hairy; petals 1.2-1.5 cm long, glabrous on the lower surface
                 9 Mature hypanthium 10-15 mm long, glabrous or glabrate; petals 2.0-2.5 cm long, glandular-hairy on lower surface (best seen in bud)
               8 Four stem faces at mid-stem about equal, almost flat, the angles sharp or winged.
                   10 Roots not rhizome-like; roots tuberiferous or spongy-thickened
                   10 Some roots rhizome-like, with adventitious buds; roots not tuberiferous or spongy-thickened.
                     11 Hypanthium 7-9 (-10) mm long; petals 8-12 mm long; seeds irregularly ridged, especially along the crest [of KY, TN, and AL westwards, west of the Appalachians
                     11 Hypanthium (9-) 10-12 mm long; petals 10-25 mm long; seeds papillate, the papillae in concentric lines [of NJ to SC east of the Appalachians]
             7 Leaves linear, narrowly elliptic, or broadest above the middle.
                       12 Plant bushy-branched
                       12 Plant simple below the cymose inflorescence.
                          13 Leaves twisted at base, borne in a vertical plane; four stem faces subequal, the angles narrowly winged
                          13 Leaves not twisted at base, borne more or less horizontally; four stem faces markedly unequal, the angle wings inconspicuous or absent.
                            14 Mature hypanthium 10-14 mm long, with glandular hairs; petals lavender-rose, 1.5-2.0 cm long
                            14 Mature hypanthium 6-10 mm long, glabrous or sparsely glandular-hairy; petals white, 1.2-1.5 cm long