1. Acalypha L. (three-seeded mercury)

Plants annual (perennial herbs, shrubs, or trees elsewhere), monoecious (dioecious elsewhere), taprooted, with clear sap, pubescent with unbranched, nonglandular and sometimes also gland-tipped hairs; stinging hairs absent. Stems erect, branched or unbranched. Leaves alternate, short- to long-petiolate, the petiole attached at the base of the nonpeltate blade. Leaf blades variously shaped, angled or rounded at the base, angled or tapered to a usually sharply pointed tip, the margins entire or more commonly toothed, often more or less with 3 main veins from the base. Stipules scalelike, 0.5–1.5 mm long, tan to purple or sometimes green, usually shed early, linear to narrowly triangular, often with few to several bristly hairs at the tip. Inflorescences axillary and sometimes also terminal, usually associated with longitudinally folded or concave, persistent, lobed, leaflike bracts, the basic units small clusters of staminate or pistillate flowers, these arranged into spikes or racemes, the pistillate clusters either basal to the staminate clusters in the same spike or in separate terminal spikes. Flowers lacking a corolla and nectar disc. Staminate flowers sessile or nearly so, minute (less than 0.5 mm long), with 4 linear to narrowly triangular sepals (these hairy) and 4–8 minute stamens having short filaments (these free or fused at the very base). Pistillate flowers with 3(–5) minute, linear to ovate sepals, the ovary with 1, 2, or more commonly 3 locules and 1 ovule per locule, the 3 styles separate or fused only at the very base, each irregularly pinnately divided into several slender lobes. Fruits 2- or 3-lobed (except in A. monococca). Seeds ovoid, with a flattened, oblong to narrowly elliptic, small, white caruncle (or this apparently absent), the surface otherwise nearly smooth to shallowly pitted or with small tubercles, dark brown to light gray or tan, sometimes mottled. About 450 species, North America to South America, Caribbean Islands, Africa, Asia to Australia, Pacific Islands; introduced in Europe.

The large genus Acalypha is most diverse in the American tropics. Several species are cultivated as houseplants (and outdoors in warmer regions) for their foliage or inflorescences, especially the paleotropical shrub A. hispida Burm. f. (chenille plant, red-hot cattail), which has elongate pistillate spikes whose fuzzy texture and red coloration is caused by the feathery-branched, red styles.