Walters, S.M. et al. (eds) (1984) The European Garden Flora. Vol. II. Monocotyledons (Part II). Cambridge University Press, Cambridge
Description of the genus
Perennial, creeping herb (in ours) and sprawling stems. Cymes simple, stalked, borne in pairs or umbels in a terminal inflorescence. Flowers actinomorphic. Sepals and petals free. Stamens 6, all similar fertile, bearded. Ovary 3-locular with 2 ovules per loculus. Fruit a dehiscent capsule.
Worldwide: 11 species in tropical America, mainly Mexico