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Key to Bidens
https://fsus.ncbg.unc.edu/main.php?pg=show-key.php&keyid=40536
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). | |
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 | |
9 Involucres usually campanulate to cylindric, sometimes ± hemispheric; disc florets (6-) 10-25 (-60); cypsela faces usually ± striate, sometimes tuberculate; [MD northward, estuarine]. | |
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. | |
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 |