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1 Flowers 2-merous, the petals white; fruits with uncinate trichomes; leaves opposite, decussate, borne spreading at right angles to the stem, mostly ovate, on petioles mostly 0.5-8 cm long; [subfamily Onagroideae; tribe Circaeeae]
1 Flowers (3-) 4 (-7)-merous, the petals yellow, pink, or white (or absent); fruits lacking uncinate trichomes; leaves alternate (rarely opposite), not decussate, usually ascending or appressed (rarely spreading at right angles to the stem), mostly lanceolate, mostly sessile or subsessile.
..2 Fruit indehiscent; seeds 1-6 per capsule, 1.5-3.5 mm long; [subfamily Onagroideae; tribe Onagreae]
..2 Fruit dehiscent; seeds (10-) 50-many per capsule, 0.3-2 mm long.
....3 Seeds with an elongate coma at one end (wind-dispersed); petals pink or white; [subfamily Onagroideae; tribe Epilobieae].
......4 Leaves all alternate; flowers numerous in a terminal raceme (with small bracts); flower buds reflexed, the flowers held horizontally or ascending; petals 10-20 mm long; stigma 4-lobed; plants 10-30 dm tall
......4 Leaves all or at least the lowermost opposite; flowers few, axillary, or in poorly developed, leafy racemes; flower buds not reflexed, the flowers ascending; petals 2-8 mm long (except 10-15 mm long in E. hirsutum); stigma capitate (except 4-lobed in E. hirsutum); plants 1-20 dm tall
....3 Seeds not comose (gravity-dispersed); petals yellow or absent (rarely white or pink).
........5 Calyx tube not extended beyond the summit of the ovary; sepals persistent on the capsule (rarely deciduous); stamens 4, 8, or 10-14; petals yellow or absent; [primarily of wetlands]; [subfamily Ludwigioideae]