| 1 | Trees or (not climbing) shrubs. |
| 1' | Climbing shrubs, or lianas, sometimes with tendrils. Flowers unisexual or functionally so. |
| 2 | Sepals essentially free at least in their upper ¾ and imbricate. |
| 2' | Sepals connate into a cup-like calyx, its upper free part (or lobes), if any, short and not imbricate. |
| 3 | Flowers bisexual. |
| 3' | Flowers unisexual. (Petals connate below.) |
| 4 | Petals free, valvate, or subimbricate in their upper part. |
| 4' | Petals connate below into a tube, their upper part free and valvate in bud. |
| 5 | Filaments free, fixed to the very base of the petals. Leaves with a layer of rounded to star-shaped appressed scales underneath at least in the young state. |
| 5' | Filaments adnate for almost their entire length to the lower tubular part of the petals. Scales absent. |
| 6 | Flowers unisexual (or functionally so). |
| 6' | Flowers bisexual. |
| 7 | Drupe ovoid-ellipsoid or oblongoid, without a fleshy lateral appendage. Flowers in rather short cymes. |
| 7' | Drupe laterally compressed (almond-like). |
| 8 | Drupe without a fleshy lateral appendage. Flowers in spikes (very rarely in panicles composed of spikes, or almost fascicled). |
| 8' | Drupe with a thick fleshy, laterally borne, practically entirely adnate appendage. Flowers in cymes. |
| 9 | Disk unilateral, thick-squamular. |
| 9' | Disk absent. |
| 10 | Filaments glabrous. Fleshy appendage of drupe covering two pronounced ribs of the endocarp. |
| 10' | Filaments with apical, longish, club-shaped hairs at least in the fertile stamens. Prominent ribs under the appendage of the drupe less pronounced or absent. |
| 11 | Ovary with a lateral swelling which in the fruit developes into a thick succulent appendage. Disk absent. |
| 11' | Ovary and fruit without such an adnate appendage. Disk whether or not present. |
| 12 | Connective surpassing the anther cells as a marked glabrous apiculus. Outer part of the endocarp finally spongious-corky and deeply irregularly lacunose. Disk absent. |
| 12' | Connective, if any, hardly or not surpassing the anther cells. Outer part of the endocarp fibrous, slightly ribbed or grooved lengthwise, or smooth outside. |
| 13 | Peduncle of inflorescence with numerous small knob-like bracts which form alveoles. Stigma peltate. Disk absent. |
| 13' | Peduncle quite smooth. Stigma small, subcapitate or point-like. Disk ± cup-shaped. |
| 14 | Inflorescence usually terminal. Anthers glabrous. |
| 14' | Inflorescence axillary. Anthers with an apical tuft of penicillate hairs. |
| 15 | Flowers sessile. Petals up to 6 mm, free to almost the base. Stigma point-like at the top of the ± attenuate (sometimes shortly style-like) part of the ovary. |
| 15' | Flowers 1-2 mm pedicelled. Petals (12-) 13-15 mm, free in the distal part only. Stigma small on one side of the inverted, i.e. cup-like distal part of the ovary. |
| 16 | Leaves opposite. |
| 16' | Leaves spirally arranged. |
| 17 | Anthers broadly club-shaped to subglobular, many-celled, with numerous pollen-bearing alveoles. |
| 17' | Anthers, as usual, with 2 cells. |
| 18 | Flowers in elongate spikes or spike-like racemes, these solitary or sometimes composed to panicles. |
| 18' | Flowers in peduncled heads or umbels, these solitary or composed to racemes or panicles. |
| 19 | Leaves markedly prominently tessellate on both faces. Sepals persistent. Albumen absent; cotyledons thick-fleshy. |
| 19' | Leaves with rather lax and but slightly raised reticulation. Sepals absent. Albumen thick, ruminate; cotyledons foliaceous. |
| 20 | Style absent, i.e. stigma sessile, thick-peltate. |
| 20' | Style (very) shortly thick-columnar, with 2-4 stigmatic lobes. |
