1Pistil 2(-4)-merous. (Exceptionally a few flowers with a 1-merous ovary)
1'Pistil 1-merous
2Fruit wall coriaceous or eggshell-like, rarely more than l(-7) mm thick
2'Fruit wall hard, corky, 3-6 mm thick, the saccate base and the carina of the fruit solid
3Fruits warty, the warts without a distinct apical appendage. (In a few cases this character may be difficult. Try both ways)
3'Fruits not warty, the appendages usually distinctly divided into a broader or thicker basal and a narrower apical part
4At least the upper half of the fruit appendages densely puberulous
4'Fruits glabrous
5Leaf axes densely tomentellous, sometimes glabrescent. Leaflets hairy all over above, soon glabrescent, the midrib sometimes excepted, tomentose on midrib and nerves beneath, densely sericeous in between. Calyx 3 mm high
5'Leaf axes sparsely puberulous to glabrous. Leaflets glabrous above, sparsely sericeous all over beneath, sometimes glabrescent. Calyx up to 1.75 mm high 15. N. melanomiscum 6a. Leaflets mostly widest at about ⅓ above the base; reticulation on upper side dense. Fruits aculeate
5''Leaflets widest at or sometimes slightly below the middle; reticulation on upper side lax. Fruits tuberculate
6Leaflets obtuse to acute; veins reticulate; domatia usually present. Burma, Thailand, Indochina
6'Leaflets tapering into a long and broad acumen; veins especially on the lower side rather distinctly scalariform; domatia absent. Borneo
7Leaves up to 7-jugate. Leaflets usually almost parallel-sided, abruptly rounded at the base, flat when dried. Fruits coarsely warty, the warts ± arranged into longitudinal rows. Malay Peninsula, Sumatra, Java
7'Leaves 2- or 3-jugate. Leaflets with strongly curved sides, tapering to the cuneate base, often curled or rolled up when dried. Fruits densely knobby like a small Pan-danus fruit head, the knobs not confluent. Borneo An unusual form of
8Fruit appendages distinctly puberulous all over
8'Fruits (sub)glabrous or exceptionally with a hair tuft on the tops of the appendages
9Petiolules above grooved. Leaflets symmetrical
9'Petiolules above not grooved. Leaflets slightly falcate.
10Leaflets beneath glabrous or nearly so
10'Leaflets beneath densely tomentose on and along midrib and nerves, distinctly to moderately densely sericeous in between
11Veins and veinlets densely reticulate, above not very conspicuous, beneath inconspicuous. Leaflets drying brown
11'Veins and veinlets on both sides of the leaflets conspicuously ± laxly reticulate. Leaflets drying green
12Twigs and leaf axes (sub)glabrous. Fruit appendages less than 10 mm long. Vietnam, Thailand, Malay Peninsula
12'Twigs and leaf axes tomentellous or puberulous, early glabrescent. Fruit appendages c. 15 mm long. Borneo
13Domatia usually present. Sepals 2-3 mm long. Fruit appendages filiform, c. 7 mm long, sparsely puberulous
13'Domatia absent. Sepals 1-1.8 mm long. Fruit appendages ligulate to strap-shaped, up to 6(-9) mm long, ± densely puberulous
14Domatia present
14'Domatia absent
15Reticulation on the upper side of the leaflets dense
15'Reticulation on the upper side of the leaflets lax
16Fruits up to 2.5 by 1.5 cm, wall up to 1 mm thick, appendages up to 10 mm long. Venation reticulate
16'Fruits up to 6 by 3.5 cm, wall up to 2.5 mm thick, appendages usually more than 10(-20) mm. Venation often tending to scalariform
17Leaves typically up to 6-jugate. Leaflets up to 5.5 times as long as wide, distinctly long- and slender-acuminate, parallel-sided. Fruit appendages sparse, 2-3(-8) mm long, upper part ligulate
17'Leaves 1- or 2-jugate. Leaflets c. 2-3.5 times as long as wide, short- and broad-cicuminate, sides curved. Fruit appendages dense, 8-10 mm long, upper part filiform
18Inflorescences usually truly terminal, not ending in a vegetative bud, infructescenc-es thus also terminal. Fruit appendages ± hair-like or sometimes ± tongue-shaped. Leaflets when dried mostly flat
18'Inflorescences axillary and pseudoterminal, the latter ending in a vegetative bud, infructescences thus lateral. Fruits mostly densely spiny, sometimes knobby. Leaflets when dried often curled or rolled up
19Leaflets pergamentaceous, apex not mucronate, midrib raised above, intercalated veins well developed, venation reticulate. Fruits up to 3 by 2.25 cm, appendages sparse and short, up to 7.5 mm long
19'Leaflets coriaceous, apex usually mucronate, midrib usually sunken above, interca-lated veins mostly inconspicuous, venation tending to scalariform. Fruits up to 6 by 3.5 cm, appendages dense, up to 2 cm long
20Fruit appendages mostly filiform. Leaflets mostly flat when dried
20'Fruit with long spines. Leaflets when dried often curled or rolled up
21Leaflets nearly always hairy below, at least on the midrib
21'Leaflets below glabrous or at most with a few minute hairs along the midrib. 24 23a. Twigs and leaves usually densely though sometimes minutely hairy, rarely glabrous. Inflorescences axillary and/or pseudoterminal
21''Twigs and leaves sparsely hairy to glabrous. Inflorescences mostly truly terminal 10. N. lappaceum 24a. Apical part of the fruit appendages thread- or hair-like, up to 15 mm long. Leaflets rather abruptly ± caudate-acuminate
21'''Apical part of the fruit appendages nipple-like, 1-2 mm long. Leaflets hardly short- and broad-acuminate
22Reticulations of the leaflets minute, not elongated parallel to the nerves. Apical part of the fruit appendages up to 10 mm long, slightly hairy.
22'Reticulations of the leaflets lax, elongated parallel to the nerves. Apical part of the fruit appendages up to 15 mm long, glabrous