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| 1 Stem and inflorescence axis lacking sessile or short-stalked glistening glands (but with spreading or ascending non-glandular hairs). |
| ..2 Stipules deeply incised, half-ovate; hirsute hairs of the stem 3 mm or longer; 0-1 pair of minor leaflets between major; mature fruiting hypanthium as broad as long or broader; hypanthium ridges rarely with eglandular hairs |
| ..2 Stipules toothed, not deeply, half-ovate to half-round; hirsute hairs of the stem 3 mm or shorter; 0-3 pair(s) of minor leaflets between major; mature fruiting hypanthium as long as broad or longer; hypanthium ridges usually with hirsute eglandular hairs |
| ....3 Flowers alternate; fruiting hypanthium 1.9-4.6 mm long; [rare waif] |
| ....3 Flowers subopposite; fruiting hypanthium 7-10 mm long; [common and widespread in much of our region] |
| 1 Stem and inflorescence with glistening glands, these either sessile, or short-stalked, or both (and also with spreading or ascending non-glandular hairs). |
| ......4 Glistening glands of the stem and inflorescence axis short stalked, or both short-stalked and sessile. |
| ........5 Lower inflorescence rachis with mostly erect hirsute eglandular hairs ca. 2 mm long; leaves with minor leaflets in pairs of 1-4 (rarely 0) between each major leaflet pair; roots merely fibrous |
| ........5 Lower inflorescence rachis with mostly ascending hirsute eglandular hairs less than 1 mm long; leaves with minor leaflet pairs 0-1 between each major leaflet pair; roots with fusiform tubers |
| ......4 Glistening glands of the stem and inflorescence axis only sessile. |
| ..........6 Mid-cauline leaves with 5-7 major leaflets; stipules proximally incised or nearly entire |
| ..........6 Mid-cauline leaves with (7-) 9-13 major leaflets; stipules incised along entire margin. |
............ 7 Major leaflets obovate to elliptic, apex obtuse to acute; flowers mostly alternate along inflorescence axis; [Coastal Plain pinelands; e. SC south to c. peninsular FL and west to e. TX] |
| ............ 7 Major leaflets lanceolate to narrowly elliptic, apex acuminate to rarely acute; flowers mostly sub-opposite along inflorescence axis; [bottomlands, marshes; CT west to s. MI and SD, south to FL, TX, the West Indies and Mexico] |