PLANTS: Trailing herbs usually with little pubescence. LEAVES: rounded in outline, usually more or less lobed or parted. FLOWERS: solitary in the leafaxils, the pedicels shorter than the subtending petioles; bracts of involucel 3, lanceolate; calyx 5-7 mm long; petals 6-8 mm long, dark orange, drying brick-red. FRUITS: schizocarpic, setose, green maturing black; mericarps 16-22, each with 2 apical spines 1.5-3 mm long, divided by internal partition into 2 cells, each with 1 seed. SEEDS: 1.5 mm long. 2n = 18. NOTES: A monotypic genus occurring from the U.S.to Argentina as well as in the Old World, frequently as a weed, but also becoming established in relatively undisturbed habitats. (Latin modiolus = hub of a wheel, in reference to the form of the fruit).