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| 1 Calyx strigose, the hairs neither spreading nor uncinate; [mostly of moist to wet habitats]. |
| ..2 Corolla limb 2-5 mm wide; mericarps taller than the style; stems terete; plant not stoloniferous; calyx usually deciduous in fruit, the lobes ≥ as long as the tube |
| ..2 Corolla limb 5-10 mm wide; mericarps not surpassing the style; stems angled; plant often stoloniferous; calyx usually persistent in fruit, the lobes ≤ as long as the tube |
| 1 Calyx with some loose or spreading, uncinate hairs; [of various habitats, mostly dry]. |
| ....3 Corolla limb 5-8 mm wide; perennial |
| ....3 Corolla limb 1-4 mm wide; annual or biennial. |
| ......4 Calyx lobes unequal, 3 lobes shorter than the other 2; corolla white; [native, of dry or moist habitats]. |
| ........5 Fruiting pedicels divergent; fruiting calyx deciduous, 3-10 mm long; inflorescence internodes usually longer than 10 mm; mericarps 1.4-2.2 mm long |
| ........5 Fruiting pedicels more-or-less erect; fruiting calyx persistent, 3-5.5 mm long; inflorescence internodes usually shorter than 10 mm; mericarps 1.2-1.5 mm long |
| ......4 Calyx lobes equal, all 5 the same size; corolla blue (occasionally yellow or white); [alien, mostly of dry disturbed habitats]. |
| ..........6 Fruiting pedicels equaling or generally longer than the calyx |
| ..........6 Fruiting pedicels distinctly shorter than the calyx. |
| ............ 7 Plants floriferous from about the middle upward; style surpassing the mericarps |
............ 7 Plants floriferous nearly to the base; style shorter than the mericarps |