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1 Plant aquatic, the leaves finely divided into segments < 0.5 mm wide; pappus awns 13-25 (-40) mm long |
1 Plant terrestrial or wetland, but not aquatic, the leaf segments > 0.5 mm wide; pappus awns lacking or present, if present < 10 mm long. |
2 Inner cypselas more-or-less equally 4-angled, thickest near the middle and equally tapered to both ends; ray florets white, pink, or pale yellowish (or absent). |
3 Leaves 2-3× dissected, primary lobes > 20, the ultimate segments rounded to acute, 2-10 mm wide; ray florets pale yellowish |
3 Leaves mostly once- pinnate, primary lobes 3-7, the ultimate segments serrate and acute, 8-50 mm wide; ray florets white or absent. |
4 Ray florets 5-8, the ligule 5-16 mm long; cypselas 2-awned, the awns 1-2 mm long; outer phyllaries (8-) 12 (-16) |
4 Ray florets 0 (or if a few present, the ligule < 3 mm long); cypselas 3 (-5)-awned, the awns 1-3 mm long; outer phyllaries 7-10 |
2 Inner cypselas flattened (if 4-angled, the alternating angles acute and obtuse), thickest toward the tip; ray florets yellow or orange (or absent). |
5 Most leaves simple, the margins dentate to serrate or incised (with 3-7 lobes). |
6 Leaves (except sometimes the lower) sessile; heads usually nodding, at least in age. |
7 Rays absent, or present and 2-15 (-18) mm long; pales (receptacular bracts) with tan or yellow tips; outer cypselas (3-) 5-6+ mm long, inner cypselas 4-8 mm long (the margins ± thickened or winged); pappus of (2-) 4 awns (1-) 2-4 mm long |
7 Rays present, (10-) 15-25 (-30) mm long; pales (receptacular bracts) with orange or red tips; outer cypselas 6-8 mm, inner cypselas 8-10 mm (margins not notably thickened or winged); pappus of 2-4 awns 3-5 mm long |
6 Leaves with a distinct petiole 1-4 cm long (this sometimes winged); heads erect. |
8 Rays 12-25+ mm long; cypselas 2.5-4.5 mm long, the margins not barbed or ciliate |
8 Rays absent or 2-5 (-12) mm long; cypselas (3-) 6-13 mm long, the margins sometimes barbed or ciliate. |
9 Involucres usually campanulate to cylindric, sometimes ± hemispheric; disc florets (6-) 10-25 (-60); cypsela faces usually ± striate, sometimes tuberculate; [MD northward, estuarine]. |
10 Cypselas usually antrorsely strigillose throughout; cypsela angles weak or absent |
10 Cypselas glabrous or sparsely setulose; cypselas angles strong to weak or rarely absent |
9 Involucres campanulate to hemispheric or broader; disc florets (5-) 20-60 (-150+); cypsela faces usually smooth or tuberculate (not notably striate); [collectively widely distributed, in a diversity of wetland types]. |
11 Cypselas ± flattened, sometimes weakly 3 (-4)-angled and 3 (-4)-awned, the faces usually smooth, seldom notably tuberculate; disc corollas 4- lobed, light yellow; anthers usually pale |
11 Cypselas (at least inner) usually ± 4-angled and 4-awned, the faces usually strigose or tuberculate; disc corollas 5- lobed, orange-yellow; anthers usually blackish |
5 Most leaves either 1- pinnately compound, the 3-5 (-7) leaflets petiolulate, or -1-2× pinnately lobed. |
12 Ray florets 0, or rays 1-3, the laminae 2-3.5 mm long. |
13 Calyculus bractlets (2-) 4 (-5), seldom ciliate; disc florets usually 10-20 |
13 Calyculus bractlets (5-) 8-16 (-21), usually ciliate; disc florets 20-150. |
14 Calyculus bractlets (5-) 8 (-10); leaves usually 3 (-5)-foliolate |
14 Calyculus bractlets 10-16 (-21); leaves usually laciniate or pinnatisect |
12 Ray florets (5-) 8-13, the laminae 10-30 mm long. |
15 Cypselas 2.5-4× as long as wide |
15 Cypselas 1.5-2 (-2.5)× as long as wide. |
16 Cypselas 2.5-5 mm long, the margins not winged, barbed, or ciliate |
16 Cypselas (4-) 5-8 mm long, the margins usually barbed or ciliate, and often also corky- winged. |
17 Calyculus bractlets 8-12 (-16), these (4-) 5-7 (-12) mm long; calyculus bractlets glabrous or fine- pubescent on the lower surface; achenes 2.5-5 mm long |
17 Calyculus bractlets 12-21, these (6-) 8-12 (20) mm long; calyculus bractlets usually coarsely short- pubescent on the lower surface; achenes 5-7 mm long |