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Key to Vernonia

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1 Leaves basally disposed (the larger leaves in a basal rosette or in the lower half of the stem, the leaves strongly reduced in size upwards); [mainly Coastal Plain and adjacent areas of inland provinces]
..2 Larger leaves basal, borne flat against the ground; larger leaves (21-) 60-75+ mm wide
..2 Larger leaves basally disposed, mainly on the lower stem; larger leaves 2-25 mm wide.
....3 Larger leaves 5-25 mm wide; leaf L:W ratio 3-17.
......4 Phyllary tips subulate.
......4 Phyllary tips acute to rounded (sometimes minutely apiculate), the narrowest short acuminate.
........5 Leaves 2-8+ mm wide; lower leaf surface scabrellous with awl-shaped, appressed hairs; plants 2-3 (-5) dm tall; [FL peninsula]
........5 Leaves (5-) 12-25 mm wide; lower leaf surface glabrate, with awl-shaped hairs sunken in pits; plants 4-8 (-10+) dm tall; [AL westwards to OK and TX]
....3 Larger leaves 2-4 (-8) mm wide; leaf L:W ratio (8-) 12-30 (-60+).
..........6 Flowers 8-15 per head; outer phyllaries 1.4-3.9 mm long, their tips acute to acuminate; involucres 4.0-6.0 mm high; [wc. and se. GA south to c. peninsular FL and west to s. MS]
..........6 Flowers 16-30 per head; outer phyllaries 1.8-7.2 mm long, their tips acuminate to long acuminate; involucres 5.0-10.0 mm high; [wc. and se. GA northeast to s. NC].
............ 7 Flowers 16-19 per head; outer phyllaries 1.8-4.8 mm long, their tips acuminate to long acuminate; involucres 5.0-7.0 mm high; [wc. and se. GA northeast to s. NC].
............ 7 Flowers 20-30 per head; outer phyllaries 3.9-7.2 mm long, their tips long acuminate; involucres 6.5-10.0 mm high; [wc. and se. GA northeast to c. SC].
1 Basal rosette absent; [collectively of a wide variety of habitats].
............ ..8 Phyllary tips subulate to filiform, at broadest at least acuminate.
............ ....9 Involucres 11-15 mm in diameter; phyllaries (50-) 60-70+; florets 50-100+
............ ....9 Involucres 4-8 (-11) mm in diameter; phyllaries 22-46 (-60+); florets 10-45 (-65).
............ ......10 Leaf L:W ratio 8-20 (-30+); leaves (2.5-) 8-12+ mm wide; plants 3-5 (-8+) dm tall; [OK, TX, westwards]
............ ......10 Leaf L:W ratio 2.5-6+; leaves (5-) 10-45 (-70+) mm wide; plants 4-30 dm tall; [collectively widespread east of the Mississippi River].
............ ........11 Middle cauline leaves 0.1-1.8 cm wide; plants 3-11 dm tall; [Coastal Plain of GA and SC, pinelands].
............ ........11 Middle cauline leaves 1.2-7.5 cm wide; plants 4-35 dm tall; [collectively widespread east of the Mississippi River, of various habitats, but not typically in Coastal Plain pinelands].
............ ..........12 Pappus whitish to yellowish, 30 outer bristles intergrading with 30+ inner bristles; leaf blades 2.5-3.5 (-4)× as long as wide
............ ..........12 Pappus brown to purple, 20 outer scales contrasting with 30-40+ inner bristles; leaf blades (3.3-) 4-6× as long as wide
............ ..8 Phyllary tips acute to rounded (sometimes minutely apiculate), the narrowest short acuminate.
............ ............ 13 Broadest leaves on a plant < 10 mm wide; leaves (even the broadest) 7-50× as long as wide.
............ ............ ..14 Lower leaf surface glabrate and pitted (with awl-shaped hairs in the pits); flowers 9-15 per head; [mainly Ouachita Mountains, of AR and OK]
............ ............ ..14 Lower leaf surface densely silky tomentose; flowers 12-29 per head; [TX and extreme sw. AR]
............ ............ 13 Broadest leaves on a plant > 10 mm wide; leaves 2-10× as long as wide (at least the broadest <7× as long as wide).
............ ............ ....15 Undersurface of leaf glabrous or nearly so, with pits (best seen at > 10× magnification) containing awl-shaped hairs or glands
............ ............ ....15 Undersurface of leaves conspicuously scabrous or pubescent, lacking pits.
............ ............ ........17 Leaf undersurfaces scabrous with appressed awl-shaped hairs, with few or no resin glands.
............ ............ ..........18 Heads with 13-30 flowers; leaf blades linear-lanceolate, 10-30 cm long, 1.2-7.5 cm wide, 4-10× as long as wide; involucre 2.3-5.5 mm wide; phyllaries 1.2-3.1 mm wide
............ ............ ..........18 Heads with 9-20 flowers; leaf blades elliptic to oblanceolate, 6-20 cm long, 1.2-5 cm wide, 3-5× as long as wide; involucre 2.0-4.0 mm wide; phyllaries 0.9-1.8 mm wide
............ ............ ........17 Leaf undersurfaces with curled, erect hairs, and with conspicuous resin glands.
............ ............ ............ 19 Heads with 30-55 florets; involucres (6-) 7-10 mm high, 5-9 mm wide
............ ............ ............ 19 Heads with (15-) 20-25 (-35) florets; involucres 4-6.7 mm high, 4-7 mm wide.
............ ............ ............ ..20 Flowers mostly 23-34 per head; inner phyllaries with tips recurved, pubescent on the inner surface; [mainly Ozarkian]
............ ............ ............ ..20 Flowers mostly 17-27 per head; inner phyllaries loosley spreading, glabrous; [mainly Plainsian, also weedy and adventive]
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