Arenga  

Low shrubs to robust tree palms, solitary or clustered, monoecious usually with unisexual inflorescences, male and female flowering separated in time, pleonanthic or hapaxanthic. Leaves imparipinnate, induplicate; leaf sheath usually disintegrating into a fibrous mesh; petiole slender to very robust; leaflets regularly arranged in one plane or unevenly arranged in several planes, strongly asymmetrical at the base, sometimes with one or two auricles. Flowering acropetal in pleonanthic species, basipetal in hapaxanthic species. Inflorescence enclosed in numerous bracts, branched to first or second order, drooping, unisexual, in hapaxanthic species the female ones produced distally before the male ones. Flowers dimorphic. Male flowers usually with more than 15 functional stamens, and without a pistillode. Female flowers with globose ovary, sessile stigmas and 2–3 locules. Fruit globose to ellipsoidal, often somewhat angled, 1–3 seeded; epicarp smooth, dull to brightly coloured, mesocarp fleshy, with high density of raphide-containing ideoblasts causing skin irritation, endocarp not differentiated. Seed with homogeneous endosperm.

Twenty four species with three varieties in tropical and subtropical Asia to N. Australia. Five species in Thailand.