| 1 | Midrib of the lamina prominent above and acumen of the lamina spinulose-dentate, with 1 or 3 teeth; lamina smooth and the margin often spinulose-dentate. — Widespread |
| 1' | Midrib of the lamina impressed above or ± prominent only in the upper part of the lamina and then the lamina usually scabrous; acumen of the lamina not spinulose-dentate or, if apiculate, then in between 2 non-spinulose lobes |
| 2 | Plants usually with thorns |
| 2' | Plants occasionally with thorns |
| 3 | Thorns lateral; acumen of the lamina apiculate and often 2-lobed. — Sumatra, Java, Lesser Sunda Islands |
| 3' | Thorns terminating leafy twigs; acumen of the lamina not apiculate and/or lobed |
| 4 | Plants usually with short-shoots bearing tufts of leaves and/or inflorescences; petiole 0.1-0.4(-0.6) cm long, usually hairy adaxially; acumen of the lamina mostly acute; leafy twigs usually distinctly hairy; tepals of the pistillate flower narrowly ovate, acute. — Malay Peninsula, Java, Philippines, Celebes, Lesser Sunda Islands |
| 4' | Plants rarely with short-shoots; petiole (0.2-)0.4-0.7 cm long, often glabrous; acumen of the lamina mostly obtuse; leafy twigs often subglabrous; tepals of the pistillate flower broadly ovate to suborbicular, obtuse to rounded. — Malay Peninsula |
| 5 | Staminate inflorescences spicate and 1.5-14 cm long; pistillate inflorescences with (1-)2-10 flowers. — Malay Peninsula, Borneo, Philippines, Celebes |
| 5' | Staminate inflorescences capitate or spicate and up to 0.8 cm long; pistillate inflorescences with 1 (or 2) flowers. — Malay Peninsula |
