*Annual ( ''R. vesicarius'' ) or perennial, mostly very variable herbs, sometimes more than 2 m tall ( ''R. sagittatus'' ). *Leaves spirally arranged, the lower ones mostly in a radical rosette (except ''R. vesicarius'' ), sheathing at base and provided with an amplexicaul ocrea. *Flowers in spurious whorls which are combined in racemes or panicles. *Fruit usually a sharply trigonous samara. Can be cultivated in the tropics at higher altitudes in fertile soil. For good leaf production, the inflorescences should be removed.