| 1 | Flowers always borne on bare older branches, and organized in a condensed cluster on short leafless lateral shoots; perianth cup-shaped, 5-7-lobed; ovary (fruit) stipitate. Fruit a dry, flat, winged samara. Embryo straight. |
| 1' | Flowers axillary, or rarely borne in a condensed capitate thyrse on older branches (Gironniera celtidifolia); perianth 4-5-lobed, with the lobes free from one another except for their base; ovary sessile. Fruit a fleshy drupe. Embryo variously curved. |
| 2 | Leaves triplinerved at base, or if pinnately nerved the stipules do not leave a circular scar around the node; lateral nerves less than 5 pairs. |
| 2' | Leaves pinnately nerved; lateral nerves more than 5 pairs; stipules free but overlapping each other, in falling leaving circular scar around the node |
| 3 | Stipules intrapetiolar, connate |
| 3' | Stipules extrapetiolar, free. |
| 4 | Female flowers borne in condensed, multiflowered raceme. Perianth of male flower induplicate-valvate. Fruit compressed, elliptic lens-shaped in cross-section |
| 4' | Female flowers solitary in the axils of leaves or borne in a cymoid cluster of 2-3. Perianth lobes of male flowers imbricate. Fruit faintly 3-5-angular in cross-section. |
| 5 | Male flowers borne in a 2-3-flowered cymoid inflorescence or in a much-branched paniculate, subterminal inflorescence. Female flowers borne in a racemose cluster of 2-10 or in a ♂♀, much-branched racemose inflorescence; staminodes mostly present. Cotyledons broad, variously folded or curved |
| 5' | Male flowers organized in a condensed, multiflowered raceme. Female flowers always solitary or rarely borne in a 2-3-flowered racemose, ♂♀ inflorescence; staminodes always absent. Cotyledons narrow, incurved |
