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1 Pappus present, of 5-60 barbellate bristles; receptable naked (without paleae or well-developed bristles); [tribe Heliantheae; subtribe Eupatoriae]. |
..2 Plant a twining herb, phyllaries and disk florets 4 per head |
..2 Plant stiffly erect to weakly spreading but never twining, phyllaries and disk florets usually > 4 per head. |
....3 Leaves in whorls of 3-7, > 2 cm wide |
....3 Leaves opposite, rarely alternate or whorled, if whorled, < 2 cm wide. |
......4 Achenes (and ovaries) 8-10-ribbed; outer phyllaries longitudinally striate |
......4 Achenes (and ovaries) (3-) 4-5-ribbed; outer phyllaries not noticeably longitudinally striate. |
........5 Heads pink to blue. |
..........6 Phyllaries in 4-6+ series, deciduous |
..........6 Phyllaries in 2-4 series, persistent (or deciduous in Praxelis). |
............ 7 Heads pink (rarely bluish); receptacles flat; florets 18-25 per head |
............ 7 Heads blue; receptacles conic; florets 25-70 per head. |
............ ..8 Bristles ca. 40; florets 25-30; phyllaries 15-25, unequal, deciduous (absence apparent in fruit) |
............ ..8 Bristles ca. 30; florets 35-70+; phyllaries ca. 25, subequal, persistent |
........5 Heads white to cream or, rarely, pale lilac. |
............ ....9 Florets 3-7 per head |
............ ....9 Florets at least 9 per head. |
............ ......10 Phyllaries not strongly imbricate, with the principal ones subequal and sub-biseriate; petioles 0.5-10 cm |
............ ......10 Phyllaries clearly imbricate, in 3+ series; some species epetiolate |
1 Pappus absent, or of scales, setae, or awns; receptacle either naked, or with paleae or well-developed bristles. |
............ ........11 Leaves whorled, linear, < 2 mm wide; head solitary; [aquatic herb growing in shallow stagnant water] |
............ ........11 Leaves opposite (or alternate in part), broader in shape and > 5 mm wide; heads typically not solitary; [terrestrial or wetland plants]. |
............ ..........12 Receptacle naked. |
............ ............ 13 Pappus of 4-10 scales; heads white, pink, or blue. |
............ ............ ..14 Heads with 20-125 florets; leaves serrate; [rarely naturalized aliens in our area] |
............ ............ ..14 Heads with 10-30 florets; leaves entire; [natives, of FL, s. GA, and MS in our area] |
............ ............ 13 Pappus none, or of a few bristles or irregular coroniform lobes; heads green to yellow. |
............ ............ ....15 Heads bright yellow, closely aggregated into corymbiform arrays of flat-topped to dome-shaped glomerules |
............ ............ ....15 Heads greenish or greenish yellow, borne in spiciform, racemiform, or paniculiform arrays. |
............ ............ ......16 Heads in paniculiform arrays, all or most of the heads not subtended by bracts |
............ ............ ......16 Heads in spiciform or racemiform arrays, each 1 (-2) heads subtended by a bract |
............ ..........12 Receptable with paleae or well-developed bristles. |
............ ............ ........17 Heads small, less than 1 cm in diameter at anthesis (the female heads enlarging in Xanthium); disc florets dull white or suffused with green or purple; florets mainly unisexual (either in the same heads and then males central and females peripheral, or in separate female and male heads); female florets 0-8 per head; [tribe Heliantheae; subtribe Ambrosiinae] |
............ ............ ..........18 Heads unisexual; cypselas shed within an indurated bur or “nut” with hooked or straight spines developed from the phyllaries and/or paleae. |
............ ............ ............ 19 Involucre of the female heads with tubercles or straight spines developing from the phyllaries; burs 1-8 mm long |
............ ............ ............ 19 Involucre of the female heads with hooked spines developing from the phyllaries/paleae; burs 10-35 mm long |
............ ............ ..........18 Heads bisexual, with functionally male and female flowers in the same head; cypselas shed individually, not enclosed. |
............ ............ ............ ..20 Heads in paniculiform arrays, all or most of the heads not subtended by bracts |
............ ............ ............ ..20 Heads in spiciform or racemiform arrays, each 1 (-2) heads subtended by a bract |
............ ............ ........17 Heads larger, mostly > 1 cm in diameter at anthesis; disc florets conspicuously white, yellow, pale yellow, or purple; florets mainly bisexual; female florets > 12 per head (except 2-8 in Polymnia). |
............ ............ ............ ....21 Disc flowers maroon-purple; leaves mainly basal |
............ ............ ............ ....21 Disc flowers white, pale yellow, or bright yellow; leaves mainly or strictly cauline. |
............ ............ ............ ......22 Disc flowers bright yellow. |
............ ............ ............ ........23 Involucre of phyllaries not subtended by a calyculus |
............ ............ ............ ........23 Involucre of phyllaries subtended by a calyculus of bracts obviously different in color, texture, and shape than the phyllaries |
............ ............ ............ ......22 Disc flowers bright white or pale yellow. |
............ ............ ............ ..........24 Disc flowers bright white; leaves unlobed or with 2 basal lobes |
............ ............ ............ ..........24 Disc flowers creamy or pale yellow; leaves prominently pinnately lobed, with 5-many lobes |