1Plants herbaceous.
1'Plants woody.
2Leaves opposite.
2'Leaves in spirals or distichous.
3Stipules fully amplexicaul, leaving annular scars.
3'Stipules semi-amplexicaul or lateral.
4Inflorescences bisexual.
4'Inflorescences unisexual.
5Receptacle urceolate; leaves with waxy glandular spots at the base of the primary vein beneath.
5'Receptacle (sub)globose, covered with peltate bracts; leaves without landular spots at the base of the vein beneath.
6Plants with prickles, at least on the twigs and/or the leaves.
6'Plants without prickles.
7Inflorescences involucrate.
7'Inflorescences not involucrate.
8Inflorescences sessile; the staminate ones with free stamens among concentrically arranged bracts; the pistillate ones with one flower; stigmas filiform.
8'Inflorescences pedunculate or subsessile; the staminate ones with distinct flowers; the pistillate ones with several to many flowers, or if one-flowered, then the stigmas tongue-shaped.
9Blade always hairy, margin dent(icul)ate; staminate inflorescences open before an thesis; pistillate flowers free or basally connate.
9'Blade mostly glabrous, margin entire; staminate inflorescences closed before anthesis; pisillate flowers connate, the free parts of the tepals conical nr cushion-shaped.
10Pistillate inflorescences with numerous flowers; staminate inflorescences much longer than wide (cultivated).
10'Pistillate inflorescences with 1 or a few flowers, staminate inflorescences almost as long as wide.
11Inflorescences bisexual.
11'Inflorescences unisexual.
12Receptacle cylindric or turbinate; stamens 3, pistillode present.
12'Receptacle globose, or discoid (to turbinate); stamens 1-2(-3); pistillode absent.
13Inflorescences staminate.
13'Inflorescences pistillate.
14Inflorescences with bracts among the flowers.
14'Inflorescences without bracts among the flowers, involucrate.
15Inflorescences with a discoid to globose receptacle, initially covered with peltate bracts.
15'Inflorescences spicate to subcapitate.
16Flowers distinct; stamens 4.
16'Flowers indistinct; stamens less than 4.
17Filaments longer than the perianth; pistillode present; plant often with snines.
17'Filaments shorter than the perianth; pistillode absent; plant without snines.
18Inflorescences in the leaf axils.
18'Inflorescences on leafless branchlets or spurs on the older wood.
19Margin of the receptacle (initially) revolute; blade more or less consoicuouslv hairy, when dry dull and brownish bove.
19'Margin of the receptacle not revolute; blade glabrous or sparsely hairv. when dry usually shining and greenish above.
20Flower(s) embedded in the receptacle.
20'Flowers not embedded (free or connate).
21Inflorescences with one flower.
21'Inflorescences with several to many flowers.
22Inflorescences in the leaf axils.
22'Inflorescences on leafless branchlets or spurs on the older wood.
23Flowers (at least in fruit) pedicellate.
23'Flowers sessile.
24Stigmas 2 and unequally long, or 1.
24'Stigmas 2 and equally long.
25Stigmas filiform to band-shaped; blade more or less conspicuously hairy, when dry dull and brownish.
25'Stigmas tongue-shaped; blade glabrous or sparsely hairy, when dry shining and usually greenish.
26Inflorescences globose-capitate, not involucrate.
26'Inflorescences discoid-capitate, involucrate.
27Uncinate hairs present; inflorescences on older wood.
27'Uncinate hairs absent; inflorescences in the leaf axils.