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| 1 Achene sessile in the base of the perigynium; perigynia 3.2-6 mm long; sterile shoots with leaves 5-10 mm wide; [either alien and rarely naturalized in our area, or native and rare]. |
| ..2 Perigynia 3.2-4.8 mm long, abruptly narrowed to a short stipe; [native, of northern hardwoods forests in the Mountains of NC and VA] |
| ..2 Perigynia 5-6 mm long, sessile; [alien, rarely naturalized in our area] |
| 1 Achene on a stipe 0.5-1.5 mm long; perigynia (4.5-) 5.6-8.0 (-10) mm long; sterile shoots with leaves 2-8 mm wide; [native, collectively common and widespread in our area]. |
| ....3 Internodes between the perigynia mostly 1.0-1.5 mm; sheaths of the pistillate bracts puberulent at the mouth. |
| ......4 Perigynia glabrous, (5.2-) avg. 6.2 (-7.7) mm long |
| ......4 Perigynia puberulent, (6.4-) avg. 7.2 (-8.1) mm long |
| ....3 Internodes between the perigynia mostly 2.0-4.0 (-6.0) mm; sheaths of the pistillate bracts glabrous at the mouth. |
| ........5 Perigynia puberulent, (5-) avg. 7 (-9) mm long; pistillate scales usually with the midrib excurrent as a short awn |
| ........5 Perigynia glabrous, (4.5-) avg. 5.6-7 (-10) mm long; pistillate scales usually with the midrib terminating below the apex, not excurrent. |
| ..........6 Perigynia (6-) avg. 7.0 (-10) mm long, broadest below the middle, tapering with straight or slightly convex sides to a conspicuous beak with a hyaline tip; pistillate scales obtuse; [of swamps, bogs, and other moist to wet habitats, nearly throughout our area] |
..........6 Perigynia (4.5-) avg. 5.6 (-7) mm long, broadest near the middle, tapering with concave sides to a short beak lacking a hyaline tip; pistillate scales acute to acuminate (the lowest sometimes aristate); [of dry to moist upland forests and openings in the Mountains] |