A large genus of shrubs, small trees, and herbaceous plants, found exclusively in the New World. With the exception of the two species here described, the introduced species are too tender for all but the mildest parts of the country. Leaves alternate. The flower-heads have no ray florets, and flowers of one sex only are found on a plant. The two following are easily accommodated in almost any soil, and are quite easily increased by summer cuttings. Many of the species have resinous secretions on the leaves and young wood, which give them, in the countries where they grow, a special value as firewood.