1Flower buds pubescent at base. [Ovary pubescent. Fruits ellipsoid, 2.5 — 4 cm long, pubescent. In male the flowers in dense clusters, strongly fragrant.] — Cultivated, originating from Sri Lanka
1'Buds glabrous (pubescent at base in H. hirtiflora and H. triandra)
2Leaves membranous, often with irregular whitish blotches. Fruits globose, 1.5-2 cm diam., glabrous; pericarp 1-2 mm thick; seeds globose. [Perianth 2-lobed; ovary glabrous.] — Riverine or marshy, usually near the coast
2'Leaves of different consistency, usually not blotched. Fruits and seeds ellipsoid. — Plant not coastal
3Perianth 2-lobed. Leaves with dots beneath (dots not to be confused with smaller punctation of different origin, lens!)
3'Perianth 3- (or 4-)lobed. Leaves with or without dots beneath
4Leaves coriaceous, 10-20(-28) cm long, finely pubescent beneath. Twigs 2-6 mm diam. Fruits 1.5-2.2 cm long, with persistent perianth. — Peat swamp or padang forest
4'Leaves membranous or thinly chartaceous, 5-12 cm long, glabrous beneath. Twigs 1.5-2 mm diam. Fruits 1-2 cm long; perianth not persistent. — Mixed forest.
5Ovary and fruits (at least at base) pubescent. Leaves with persistent indumentum beneath
5'Ovary and fruits glabrous (fruits almost glabrous in H. triandra). Leaves glabrous or pubescent beneath
6Twigs 2-5 mm diam. Leaves 9-27 cm long, lower surface without dots. Fruits with hairs 0.5 mm long or less. — Thailand, Peninsular Malaysia; specimens from Sumatra not seen
6'Twigs 5-8 mm diam. Leaves 20-36 cm long, with dots beneath (lens!). Fruits with hairs 2 mm long
7Leaves with dots beneath (lens!). Lateral nerves generally flat or sunken above
7'Leaves without dots beneath. Nerves either raised or flat to sunken above.
8Leaves usually with persistent indumentum beneath (sometimes glabrescent), and with both dots and dashes (lens!). Twigs conspicuously hollow. Fruits 4-7 cm long, the perianth generally persistent
8'Leaves glabrous or glabrescent beneath, with dots, not with dashes. Twigs not conspicuously hollow. Fruits variable
9Bark of twigs pale, greyish to straw-coloured, contrasting with blackish petiole. Leaves dispersed in 3-5 rows. [Female flowers and fruits not known.] — Sumatra (N Aceh); at c. 1300 m
9'Bark of twigs brown, not contrasting with petiole. Leaves distichous (or in 3 rows in H. glabra, p.p.)
10Fruits (4.5-)5-8 cm long, pericarp 10-20 mm thick
10'Fruits 1-2.5 cm long, pericarp much thinner
11Twigs 1.5-2 mm diam. Leaves 5-12 cm long. Fruits 1.1-2 cm long
11'Twigs 2.5-4(-6) mm diam. Leaves (8-) 12 cm long or more. Fruits 1.8-2.5 cm long
12Leaves distichous. — C & N Sumatra
12'Leaves distichous or in 3 rows. — S Sumatra, Mentawai Is., north to Simeulue I., Java
13Leaves with persistent indumentum beneath. Fruits with persistent perianth.
13'Leaves glabrous or glabrescent beneath. Fruits with persistent perianth or not
14Hairs harsh, older leaves scabrous beneath. [Fruits 1-1.4 cm long.]
14'Hairs softer; older leaves not scabrous beneath
15Twigs 5-8 mm diam.; leaves 20-40(-70) cm long. Leaf bud with hairs 0.5-1 mm. Fruits 3.8-5.5 cm long
15'Twigs 3-5 mm diam.; leaves 13-21 cm long. Leaf bud with hairs 0.2-0.3 mm long. Fruits 2-3 cm long
16Lateral nerves flat or sunken or but faintly raised above. Colour of lower leaf surface generally greyish brown, not much contrasting with upper surface
16'Lateral nerves distinctly raised above. Colour of the lower leaf surface bright brown or chocolate, contrasting with the upper surface
17Twigs 1.5-3 mm diam. Leaf bud, twig apex, and young inflorescences with woolly hairs 0.3-0.7 mm. Leaves 5-9 cm long
17'Twigs (2-)3-10 mm diam. Leaf bud, twig apex, and inflorescences 0.1-0.3 mm long. Leaves more than 10 cm long
18Leaves distichous, matt on drying caused by minutely wrinkled upper surface. Bark of twigs straw or brown
18'Leaves distichous or in 3-5 rows; not particularly matt, upper surface not finely wrinkled. Bark of twigs pale, grey-brown or straw, contrasting with the blackish petiole
19Leaves elliptic-oblong to oblong, olivaceous-brown above. Stem grey-brown, not much contrasting with petiole. Fruits brown on drying, 2.2-3 cm long, perianth persistent
19'Leaves elliptic-oblong to lanceolate, dark olivaceous above. Stem pale, ± yellowish brown, rather contrasting with the petiole. Fruits blackish on drying, 1.5 cm long, perianth not persistent
20Leaves distichous or in 3 rows. Fruits 2.5-3.5 cm long, with the perianth persistent. Pedicel articulated (best seen in male flowers).
20'Leaves in 3-5 rows. Fruits 3-5.5 cm long, perianth not persistent. Pedicel not articulated
21Perianth 4-lobed. Pedicel not articulated. Fruits 8-9 cm long. [Flowers known only from the remnants persistent under the young fruits.]
21'Perianth generally 3-lobed. Pedicel articulated. Fruits up to 6.5 cm long.
22Twigs ± angular, with lines or ridges
22'Twigs terete or faintly angular, neither lined nor ridged
23Buds pubescent (known only in male flowers). Fruits 5-6 cm long. — N Sumatra
23'Buds glabrous. Fruits 2-4 cm long
24Twigs 1-3 mm diam. Leaves membranous, midrib beneath late glabrescent. Fruits 2.3-2.4 cm long
24'Twigs 2-5 mm diam. Leaves chartaceous. Fruits 1.9-6.5 cm long
25Leaf bud and inflorescences with hairs 0.1-0.2 mm long. Midrib beneath early glabrescent. Fruits 4.5-6.5 cm long
25'Leaf bud and inflorescences with hairs 0.1-0.6 mm long. Midrib often late glabrescent. Fruits 1.9-3.5 cm long. — Variable; 3 varieties based on fruit size