1Aril divided into segments to or almost to the base
1'Aril entire or laciniate up to halfway or less
2Inflorescences or infructescences paniculate, with scars of basal cataphylls, without apical vegetative bud. Bark of twigs smooth or very finely striate. Fruits 1.5-3 cm long. [Bracteole absent. Leaves not conspicuously brittle when dry.]
2'Inflorescences either 1) simple or furcate, short, (sub)sessile, or panicle-like with peduncle, without basal cataphyll scars and without terminal bud, or 2) compound, consisting of those of the foregoing type distichously arranged on short-shoots, with apical vegetative bud. Bark of twigs usually striate, longitudinally cracked, or flaking. Fruits 1.5-8 cm long
3Inflorescence a compound synflorescence, with apical vegetative bud. Bracteole (female flowers not seen) absent. Fruits 5 cm long, conspicuously pubescent. Crowded linear basal cataphyll scars usually present on innovations. [Leaves brittle when dry.]
3'Inflorescences without apical vegetative bud, rarely present (M carrii, M. hooglandii, M. markgraviana). Bracteole scar on fruiting pedicel present. Fruits of variable size, pubescent or glabrescent. Crowded basal cataphyll scars on twigs usually not present. [Leaves brittle when dry.]
4Aril at apex convoluted or shallowly laciniate. Seed not variegated, not pointed at one end
4'Aril coarsely incised for about the upper 1/3, or ± entire in the Philippines. Seeds usually variegated, often bluntly pointed at one end. [Bracteole absent. Stigma narrowly 2- or few-lobed. Inflorescence paniculate. Monoecious. Leaves brittle when dry, not whitish below.]
5Bracteole absent. Inflorescence paniculate. Stigma minutely 2-lobed (or few-lobed in H. iryaghedhi, introduced). Leaves brittle when dry, lower surface usually not whitish (papillose and whitish below only in H. iryaghedhi).
5'Bracteole present. Inflorescences short, wart- or worm-like, simple or forked, scar- covered, (sub)sessile. Stigma few- to many-lobed. Leaves generally not brittle when dry; lower surface usually ± whitish [venation on upper surface finely reticulate and usually clearly visible, unlike most other genera.]