| 1 | Stamens 3, staminodes 6. |
| 1' | Stamens 4-15, staminodes absent. |
| 2 | Stamens the same number as petals, stamens epipetalous. |
| 2' | Stamens double the number of petals. |
| 3 | Ovary semi-inferior, calyx obsolete, but pedicel at apex with epicalyx formed by bracteoles; flower-axis thickened, calyx-like. |
| 3' | Ovary superior, calyx (tube and lobes) present; no epicalyx. |
| 4 | Flowers in axillary fascicles. |
| 4' | Flowers in axillary panicles. |
| 5 | Filaments connate to a cylindrical tube including ovary and style. |
| 5' | Filaments free, filiform, adnate to the petals at base. |
| 6 | Flowers in axillary spikes; petals remaining united into a corolla tube in the lower half. |
| 6' | Flowers in axillary racemes or fascicles; petals distinct. |
| 7 | Ovary glabrous; plant indument of simple hairs. |
| 7' | Ovary densely hairy; plant indument of branched hairs. |
| 8 | Petals white-bearded inside. |
| 8' | Petals short-pubescent or glabrous inside. |
| 9 | Flowers in racemes. |
| 9' | Flowers in axillary fascicles. |
