Shrubs, usually dioecious, sparingly hairy to glabrescent, hairs simple. Leaves often clustered on axillary short shoots; blade glabrescent. Inflorescences: staminate paniclelike or racemelike thyrses, or fascicles on short shoots; pistillate fascicles on short shoots or flowers solitary. Pedicels present or absent. Staminate flowers: sepals 4–10, sometimes weakly differentiated in 2 whorls; nectary intrastaminal, lobed; stamens 4–10. Pistillate flowers: sepals 5–13, sometimes differentiated in 2 whorls; nectary lobed. Fruits capsules. Seeds oblong, ovoid, or pyriform, with one flattened radial surface if 2 seeds develop per locule, otherwise both radial surfaces rounded, seed coat dry, smooth or wrinkled near hilum. x = 12.
sw United States, n Mexico.
Species 5 (3 in the flora).
In addition to the three species treated for the flora area, Tetracoccus includes two Mexican species, T. capensis (I. M. Johnston) Croizat from the extreme tip of Baja California Sur and T. fasciculatus (S. Watson) Croizat from the Chihuahuan Desert.
|1||Leaves alternate and clustered on short shoots, blades 2–12 mm; staminate flowers in fascicles on short shoots; filaments glabrous; pistillate pedicels 1–3 mm; pistils usually 3-carpellate; seeds 1(–2) per locule, both radial surfaces usually rounded.||Tetracoccus hallii|
|1||Leaves whorled, opposite, or subopposite, not clustered on short shoots, blades 15–30 mm; staminate flowers in paniclelike or racemelike thyrses; filaments villous basally; pistillate pedicels 6–15 mm; pistils usually 4-carpellate; seeds (1–)2 per locule, usually with one flattened radial surface.||> 2|
|2||Leaf blades ovate to broadly elliptic, margins prominently serrate-dentate; staminate inflorescences congested paniclelike thyrses; pistillate sepals 8, in 2 series, greenish.||Tetracoccus ilicifolius|
|2||Leaf blades oblong or oblanceolate to linear, margins entire or remotely serrulate; staminate inflorescences sparingly branched racemelike thyrses; pistillate sepals 7–13, in 1 series, red.||Tetracoccus dioicus|