1Ovary 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)
2Leaflets densely tomentellous at least on the midrib beneath
2'Leaflets subglabrous
3Leaflets ± 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
4Lowermost pair of leaflets not stipule-like
4'Lowermost pair of leaflets stipule-like, attached near the base and much smaller than the others
5Pistil 2- or 3-locular
5'Pistil 1-locular
6Leaflets 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
7Leaflets acuminate at apex; midrib above prominulous; branchlets hollow, inhabited by ants
7'Leaflets rounded at apex; midrib above slightly sunken; branchlets solid, without ants
8Twigs 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
9Margin 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