1 | Leaves in whorls or with occasional opposite pair |
1' | Leaves exclusively opposite |
2 | Corolla doubled |
2' | Corolla not doubled |
3 | Leaves subsessile, blade base subcordate |
3' | Leaves distinctly petiolate, blade base usually not subcordate |
4 | Inflorescence containing empty bracts; anthers sagittate at the base |
4' | Inflorescence without bracts or all bracts with flowers in the axils; anthers cordate at the base |
5 | Corolla tube 4.5-5.2 mm long; inflorescences very delicate; secondary veins 6-9 pairs |
5' | Corolla tube > 7 mm long; inflorescences variable but mostly not very delicate; secondary veins 4-26 pairs |
6 | Sepals not ciliate, 3-14 mm long, leafy and often cordate, or linear but always narrower at the base than in the middle |
6' | Sepals ciliate or not, 0.9-6 mm long, not leafy or cordate, widest at the base |
7 | Stamens inserted in lower half of corolla tube |
7' | Stamens inserted around middle or in upper half of corolla tube |
8 | Leaves papery; cultivated |
8' | Leaves coriaceous; native |
9 | Corolla tube ≥ 24 mm long |
9' | Corolla tube < 24 mm long |
10 | Sepals not ciliate. — Peninsular Malaysia |
10' | Sepals ciliate. — Throughout Malesia (except New Guinea) |
11 | Corolla puberulent on the lobes outside |
11' | Corolla glabrous on the lobes outside |
12 | Leaves thickly coriaceous; sepals 3-6 mm long |
12' | Leaves not coriaceous; sepals 0.9-4 mm long |
13 | Corolla lobes pubescent inside, at least in lower half, often also pubescent outside and at least ciliate |
13' | Corolla lobes glabrous inside or pubescent only at extreme base, mostly not ciliate |
14 | Inflorescence and flowers robust; cultivated |
14' | Inflorescence and flowers not robust; native |
15 | Head of bud in mature corolla bud acuminate or acute; sepals usually not ciliate |
15' | Head of bud in mature corolla bud rounded or obtuse; sepals ciliate or not |
16 | Corolla tube mostly glabrous inside, 3.7-11 times as long as sepals; fruit 2-40-seeded. — Throughout Malesia |
16' | Corolla tube pubescent inside, 8-12 times as long as sepals; fruit 1- or 2-seeded. — Peninsular Malaysia |