1 Fertile stamens 4; calyx lobes connate at anthesis for > ½ their length, later separating

1 Fertile stamens 2 (with 2 staminodia without anthers, or with rudimentary anthers); calyx lobes separate, or connate at base for < ¼ the length of the calyx.

  2 Capsule lanceoloid, > 8× as long as its diameter; calyx lobes connate at base < ¼ the length of the calyx

  2 Capsule ovoid to ellipsoid, < 5× as long as its diameter; calyx lobes distinct to the base at anthesis and after.

    3 Leaves thick in texture; leaf blades glandular punctate; seeds ca. 1× as long as wide.

      4 Leaves primarily in a basal rosette, leaves of the stem strongly reduced upward to bracts; capsule (1.8-) 3.4-7 mm long; [primarily of seepage of flatrocks]

      4 Leaves primarily on the stem, not conspicuously reduced upward; capsule 1.4-3.4 mm long; [of stream or river banks]

    3 Leaves thin in texture; leaf blades eglandular; seeds ca. 1.5-3× as long as wide.

        5 Leaves variously shaped, but longer than wide; stems erect, ascending, or prostrate, but not mat-forming; [collectively widespread].

          6 Leaf blades 5-15 mm long; lower leaves (and upper as well) widest at base and rounded or clasping; bracteal leaves subtending flowers much smaller (< 1/2 × as long) than the lower stem leaves; pedicels much longer than the reduced bracteal leaves subtending them; flowers all chasmogamous (opening)

          6 Leaf blades 10-30 mm long; lower leaves narrowed towards the base; bracteal leaves subtending flowers only somewhat shorter than lower stem leaves; pedicels shorter than or somewhat longer than the slightly reduced bracteal leaves subtending them; flowers all or in part cleistogamous (remaining closed).

             7 Pedicels 5-20 mm long; leaves acute to obtuse at the apex; some flowers on a plant chasmogamous; [widespread and in many damp habitats]

             7 Pedicels 1-5 (-10) mm long; leaves obtuse to rounded at the apex; no flowers (usually) on a plant chasmogamous; [tidal shores, VA northwards]