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| 1 Calyx immediately subtended by 1-3 pairs of bracts; [tribe Caryophylleae]. |
| ..2 Calyx 20-40-nerved |
| ..2 Calyx 15-nerved |
| 1 Calyx lacking subtending bracts. |
....3 Sepals 25-62 mm long; calyx lobes longer than the calyx tube, the lobes as long as or longer than the corolla lobes; [tribe Sileneae] |
| ....3 Sepals (1-) 10-28 (-40) mm long; calyx lobes shorter than the calyx tube, the lobes much shorter than the corolla lobes (except Gypsophila). |
| ......4 Styles 2; fruit valves 4; petals appendaged or not; [tribe Caryophylleae]. |
| ........5 Sepals 1-5 mm long, the commissures between the sepals scarious. |
| ..........6 Leaves lanceolate to ovate, (1-) 2-20 (-35) mm wide; plants few-branched, or if diffusely-branched, only in the upper half of the plant's length |
| ..........6 Leaves linear, 0.2-2 (-3) mm wide; plants diffusely branched from near the base upwards |
| ........5 Sepals 7-25 mm long, lacking commissures. |
| ............ 7 Calyx tubular, 20-nerved; petals appendaged; perennial |
| ............ 7 Calyx ovoid, 5-nerved; petals not appendaged; annual |
| ......4 Styles 3-5 (or 0 in staminate plants); fruit valves 3, 4, 5, 6, 8, or 10; petals generally appendaged; [tribe Sileneae] |
| ............ ..8 Plant glabrous; calyx glabrous, narrowly funnelform, dilated above the midpoint; petals pink; stem with glutinous zones on upper internodes |
| ............ ..8 Plant glabrous or pubescent; calyx glabrous or pubescent, either tubular (nearly the same diameter through its length) or broadened below the middle (flask-shaped); petals white or pink (rarely absent); stem lacking glutinous zones (except S. antirrhina). |
| ............ ....9 Styles mostly 3; capsule with 3 or 6 teeth; calyx tubular or campanulate at anthesis, not greatly inflated (except in S. vulgaris) |
| ............ ....9 Styles mostly 5; capsule with 5 or 10 teeth; calyx tubular at anthesis, becoming strongly inflated later in S. dioica and S. latifolia. |
| ............ ......10 Petal limbs deeply divided into 4 linear segments; [or, former Lychnis section Uebelinia] |
| ............ ......10 Petal limbs unlobed, emarginate, or shallowly 2-lobed. |
| ............ ........11 Leaf blades with dense silky white hairiness; flowers bisexual; [or former Lychnis section Agrostemma] |
| ............ ........11 Leaf blades variously pubescent, but not with silky-appressed pubescence; [Silene section Melandrium] |