Common threeseed mercury

Common three-seeded mercury is an annual herbaceous plant. It grows from a taproot, reaching 1/2–2 feet (15–61 cm) tall, and is usually without branches. The central stem can be either covered with fine white hairs or hairless. The lanceolate to lanceolate-rhombic acute leaves are alternate with slightly hairy petioles about 1.5 inches (4 cm) long, bluntly serrated margins, and pinnate venation. Leaves are deep green and somewhat shiny above, light green and mostly hairless below and can be up to 2.75 inches (7 cm) long and 1.5 inches (4 cm) wide. There is a tendency for the leaves to cluster near the top of the stem or stems. A conspicuous, slightly ciliate bract with 5-9 lobes is located where the leaf petiole meets the stem. This bract wraps around the inflorescence, which consists of a green cyathium. The cyathium contains minute staminate and pistillate flowers lacking petals. Male flowers terminate the peduncle with capitate clusters. The flowers consists of 4 tiny golden green upwardly bent sepals, acute to blunt in shape, and many stamens. Female flowers consist of minute green sepals, a hairy tri-locular ovary, and three fringed styles. One seed per locule is produced. The mature pods are tan colored, 1/15" (1.6-1.8mm) long, and deeply lobed. There is no floral scent associated with the flowers.This plant is somewhat unusual in that it has clear sap as opposed to the typically milky sap of other members of Euphorbiaceae.Acalypha rhomboidea is quite similar to Acalypha virginica. The two may be distinguished by the number of lobes on the bracts; the latter has 9-15 lobes whereas the former has only 5-9. Acalypha rhomboidea also resembles young redroot pigweed (Amaranthus retroflexus L.), but may be distinguished from the latter by the flower clusters, bracts, and occasionally bronze-green leaves of the former.