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| 1 Leaves not accompanied by stipules (stipules absent). |
| ..2 Sepals fused into a toothed or lobed tube |
| ..2 Sepals distinct, or slightly fused at their bases |
| 1 Leaves accompanied by stipules (stipules present), these scarious or hyaline and readily apparent. |
| ....3 Fruit a utricle; seed 1 per fruit; petals absent. |
| ......4 Leaves alternate; staminodes petaloid, ovate to oblong; [tribe Corrigioleae] |
| ......4 Leaves opposite (or the uppermost alternate in Herniaria); staminodes not petaloid, subulate; [tribe Paronychieae]. |
| ........5 Stipules inconspicuous; sepals green-margined, obtuse, lacking awns |
........5 Stipules usually conspicuous; sepals white-scarious-margined, hooded or awned |
| ....3 Fruit a capsule; seeds 3-many per fruit; petals present. |
| ..........6 Stem leaves subulate, 1-2 mm long, pectinate-fringed at the base; basal rosette leaves spatulate (usually withering quickly after overwintering; stems wiry, stiff, subdichotomously branched; [of xeric sands on the Coastal Plain from se. VA southward] |
| ..........6 Stem leaves larger, mostly both longer and broader, not pectinate-fringed at the base; basal rosette present or absent; stems either thicker, more flexuous, or not subdichotomously branched; [collectively more widespread]. |
| ............ 7 Leaves appearing verticillate, 10-16 per node, filiform to linear; [tribe Spergulaeae] |
| ............ 7 Leaves opposite or in whorls of 4, linear to ovate or spatulate. |
| ............ ..8 Leaves mostly in whorls of 4, obovate-spatulate, 2-8 mm long; [tribe Polycarpaeae] |
| ............ ..8 Leaves opposite, linear or orbicular, 5-40 mm long. |
| ............ ....9 Leaves orbicular-ovate; styles partly united; [tribe Polycarpaeae] |
| ............ ....9 Leaves linear; styles separate; [tribe Spergulaeae] |