1Corolla lobes in bud strongly twisted to the left, 1.8-9.5 times as long as wide
1'Corolla lobes in bud not strongly twisted, 0.9-1.8 times as long as wide
2Leaves minutely punctate beneath
2'Leaves not minutely punctate beneath
3Inflorescence mostly axillary, shorter than subtending leaves, often minutely puberulent
3'Inflorescence terminal panicles, usually longer than subtending leaves, glabrous
4Corolla tube ≥ 5 mm long, lobes > 6 mm long; 7-11 strong pairs of secondary veins
4'Corolla tube < 5 mm long, lobes ≤ 5 mm long; 7-23 pairs of secondary veins, if ≤ 13 then only weakly distinct from tertiary venation
5Inflorescence 1-3.7 cm long; disk 0.6-0.8 times as long as ovary; tube densely pubescent inside
5'Inflorescence 3.9-13.2 cm long; disk 0.3-0.6 times as long as ovary; tube glabrous or sparsely pubescent only at top inside
6Inflorescence minutely puberulent, mostly axillary
6'Inflorescence glabrous, axillary or terminal
7Inflorescence mostly axillary, if terminal not forming large panicles
7'Inflorescence terminal, sometimes also axillary, forming panicles
8Leaves thickly coriaceous; petiole (1.5-)2-5.2 cm long; corolla lobes 1.7-2.9 mm long
8'Leaves coriaceous to subcoriaceous; petiole 0.5-2.1 cm long; corolla lobes 2.7-8.5 mm long
9Inflorescence robust; leaves mostly narrow elliptic
9'Inflorescence delicate; leaves broad elliptic, oblong or obovate
10Bracteoles on flower pedicels
10'Bracteoles at base of flower pedicels
11Inflorescence delicate; anthers 1-1.3 by 0.3-0.4 mm. — Peninsular Thailand to Malesia
11'Inflorescence robust; anthers 1.1-4 by 0.4-0.8 mm. — Japan and China to Indochina and the Philippines
12Corolla tube 4.7-8 mm long; leaf apex rounded to apiculate
12'Corolla tube 1.2-4.1(-4.7) mm long; leaf apex acuminate, very rarely to apiculate
13Leaves glaucous beneath, secondary veins thin and not prominent
13'Leaves not glaucous beneath, secondary veins prominent or not
14Corolla tube > 5 mm long; leaves 8-14 cm long
14'Corolla tube < 2 mm long; leaves 2.6-10.7 cm long
15Inflorescence < 2 cm long; pedicels ≤ 1.2 mm long
15'Inflorescence > 3 cm long; pedicels ≥ 2 mm long
16Leaf secondary veins arcuate ascending. — Ceram, Ambon
16'Leaf secondary veins ± straight, almost perpendicular to midrib. — Peninsular Malaysia, Borneo