Shrubs [trees], monoecious [dioecious], glabrous [hairy, hairs simple]; branching phyllanthoid. Leaves persistent, alternate, simple, scalelike on main stems, well developed on ultimate branchlets; stipules persistent [deciduous]; blade margins entire. Inflorescences unisexual, staminate proximal, few-flowered fascicles or flowers solitary, pistillate distal, flowers solitary. Pedicels present. Staminate flowers: sepals 6, connate throughout [connate basally to most of length], with scales at rim of calyx tube [near bases of lobes]; petals 0; nectary absent; stamens 3; filaments connate; connectives not extending beyond anthers; pistillode absent. Pistillate flowers: sepals persistent, 6, connate basally; petals 0; nectary absent; pistil 3-carpellate; styles 3, distinct, 2-fid. Fruits capsules. Seeds 2 per locule, rounded-trigonous; seed coat fleshy, smooth; caruncle absent. x = 13.
Introduced; Fla., Asia, Indian Ocean Islands, Pacific Islands, Australia, introduced also in West Indies, Africa, tropical and subtropical regions.
Species 10–30 (1 in the flora).
Breynia exhibits phyllanthoid branching (G. L. Webster 1956–1958), with well-developed leaves and flowers produced only on the deciduous ultimate branchlets and scalelike leaves on all other stems (referred to as main stems in this treatment). Like Glochidion and some Phyllanthus species, Breynia has a pollination mutualism with the moth genus Epicephala (reviewed in A. Kawakita and M. Kato 2009); see the discussion under 7. Glochidion for more information. Breynia is difficult taxonomically, hence the wide range in the number of species recognized within the genus.
Some Breynia species are grown as ornamental shrubs in tropical and subtropical areas; B. disticha is the most common and widespread.