1 | Ovary 3-5-locular; fruits broadly ovoid, slightly lobed, septifragally dehiscent; seeds with a small sarcotesta around the hilum and the basal half enclosed by a cupular arillode (Subg. Synalectryon) |
1' | Ovary 1- or 2-, exceptionally 3-locular; fruits with ± spreading lobes, dehiscent by an irregular calyptra; seeds largely covered by a sarcotesta with only a narrow, lobed, free margin (Subg. Alectryon) |
2 | Leaflets densely tomentellous at least on the midrib beneath |
2' | Leaflets subglabrous |
3 | Leaflets ± acuminate; nerves not distinctly connected; fruit wall hard, inside glabrous |
3' | Leaflets broadly rounded to slightly emarginate; nerves looped and joined; fruit wall pergamentaceous, inside hairy |
4 | Lowermost pair of leaflets not stipule-like |
4' | Lowermost pair of leaflets stipule-like, attached near the base and much smaller than the others |
5 | Pistil 2- or 3-locular |
5' | Pistil 1-locular |
6 | Leaflets entire; fruits usually with only 1 lobe developed, c. 15 by 12.5-15 mm diam., the wall corky, c. 1.5-2 mm thick; seeds with a smooth sarcotesta |
6' | Leaflets nearly always incised; often 2 fruit lobes developed, these c. 8-10 mm diam., the wall woody, 0.5-1 mm thick; seeds with a papillose sarcotesta |
7 | Leaflets acuminate at apex; midrib above prominulous; branchlets hollow, inhabited by ants |
7' | Leaflets rounded at apex; midrib above slightly sunken; branchlets solid, without ants |
8 | Twigs terete to slightly grooved, up to 5 mm thick; petiole halfway along its length up to 2.5 mm thick; leaflets up to 16.5 by 6 cm |
8' | Twigs strongly 5-grooved, 4-10 mm thick; petiole halfway along its length 2.5-8 mm thick; leaflets up to 45 by 17 cm |
9 | Margin of leaflets with some distant teeth mostly only in the upper half; fruits not or only slightly cordate |
9' | Margin of leaflets rather densely serrate-dentate nearly from the base; fruits deeply cordate |