1Stems succulent, armed; leaves usually absent
1'Stems not succulent, usually unarmed (if armed, then leaves present); leaves present
2Carpels 1-several, distinct, ovule 1 per carpel, or carpels 2 or more, united in a compound ovary with as many locules and ovules as carpels
2'Carpels always 2 or more, united in a compound ovary, ovules more than 1 per carpel
3Leaves alternate; inflorescence not subtended by a involucre; tepals free, not petaloid
3'Leaves often opposite; inflorescence often subtended by a conspicuous involucre; perianth connate in a petaloid tube simulating a corolla
4Leaves succulent; ovary superior or inferior
4'Leaves usually not succulent; ovary superior
5Perianth with only tepals, not petaloid
5'Perianth with sepals and petals, or sepaloid bracteoles and tepals
6Perianth greenish, herbaceous; filaments free
6'Perianth scarious, dry; filaments connate below in a tube
7Sepals or sepaloid bracteoles 2
7'Sepals 4 or 5
8Herbs or subshrubs; ovules 2-several; fruit a capsule
8'Vines; ovule 1; fruit indehiscent
9Leaves alternate, opposite or whorled; petals absent or inconspicuous; ovary with 2-several locules
9'Leaves opposite; petals usually present, conspicuous; ovary with 1 locule