KEY TO THE SPECIES OF PENINSULAR MALAYSIA, SUMATRA AND BORNEO

1Corolla tube > 4 mm long
1'Corolla tube < 4 mm long
2Corolla tube densely to sparsely pubescent all over outside
2'Corolla tube glabrous to very sparsely puberulent (then not all over) outside
3Bracts < 1 mm long; leaves mostly oval in shape with equally rounded base and apex; secondary veins obscure above
3'Bracts > 1 mm long; leaves variable in shape but not as above; secondary veins usually visible above, rarely obscure
4Leaves mostly thickly coriaceous with strongly inrolled margins and venation obscure beneath; corollas fairly fleshy
4'Leaves papery to coriaceous, margins flat or weakly inrolled; corollas not fleshy
5Leaves ovate to elliptic, if narrowly so then not pubescent beneath; inflorescence usually glabrous, rarely pubescent; fruit articles 13-28.2 mm long, fruit stalks 3.4-15 mm long
5'Leaves mostly narrowly elliptic or linear, rarely to ovate, usually sparsely puberulent beneath, sometimes only on the midrib; inflorescence puberulent; fruit articles 7.5-10.2 mm long, fruit stalks 1.8-2.1 mm long
6Inflorescence 2.5-9 cm long, usually densely pubescent, rarely to glabrous; fruit articles 17-30 cm long. — Sumatra, Peninsular Malaysia
6'Inflorescence 1-3.5 cm long, only very rarely densely pubescent; fruit articles 6-20(-25.3) mm long. — Widespread in W Malesia
7Corolla bud head 0.35-0.49 of bud length; corolla lobes 1.1-1.2 mm long. — Not in Peninsular Malaysia
7'Corolla bud head 0.18-0.32(-0.42) of bud length; corolla lobes 1.2-3.8 mm long. — Peninsular Malaysia