The Manual of the Botany of the Northern United States / Including the District East of the Mississippi and North of North Carolina and Tennessee

by Asa Gray

1. Jussiæa. Petals 4–6. Stamens twice as many. Capsule elongated.

2. Ludwigia. Petals 4 or none. Stamens 4. Capsule short.

[++][++] Calyx-tube prolonged beyond the ovary (scarcely so in n. 3) and deciduous from it. Flowers 4-merous.

3. Epilobium. Seeds silky-tufted. Flowers small, not yellow. Lower leaves often opposite.

4. Œnothera. Seeds naked. Flowers mostly yellow. Leaves alternate.

[+][+] Fruit dry and indehiscent, 1–4-seeded. Leaves alternate.

5. Gaura. Calyx-tube obconical. Filaments appendaged at base.

6. Stenosiphon. Calyx-tube filiform. Filaments not appendaged.

[*][*] Parts of the flower in twos. Leaves opposite.

7. Circæa. Petals 2, obcordate or 2-lobed. Stamens 2. Fruit 1–2-seeded, bristly.