PLANT: Spiny shrubs or trees. LEAVES: on new long growth petioled soon deciduous in dry weather, the petioles in part remaining as a spine when the leaf falls; secondary leaves sessile or nearly so, borne in fascicles on short shoots in axils of spines. INFLORESCENCE: terminal spikes, racemes, or panicles. FLOWERS: red, yellow, white, or purple; sepals 5 free; petals 5 united into a cylindrical tube; stamens 10-15(-23), adnate to corolla tube; pistil 3-carpelled, the ovary superior, 3-loculed. FRUITS: 3-valved capsules. x = 12. NOTES: 1 genus; sw US; Mex.