Common three-seeded mercury

Description

Acalypha rhomboidea (common three-seeded mercury, rhombic three-seeded-mercury, rhomboid mercury, copperleaf, rhombic copper-leaf, three-seeded-mercury, ricinelle rhomboide,diamond threeseed mercury; syn. Acalypha urticifolia Raf., Acalypha virginica L. forma intermedia Millsp., Acalypha virginica L. var. rhombifolia Riddell, Acalypha virginica L. var. rhomboidea (Raf.) Cooperr.) is a plant in the spurge family, Euphorbiaceae. The species name rhomboidea means "diamond-shaped", and describes the leaves. Common three-seeded mercury is an annual herbaceous plant. It grows from a taproot, reaching 15–60 cm (1⁄2–2 ft) 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 4 cm (1+1⁄2 in) 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 7 cm (2+3⁄4 in) long and 4 cm (1+1⁄2 in) 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 four 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, 1.6–1.8 mm (1⁄16–5⁄64 in) long, and deeply lobed. Acaena is a genus of about 60 species of mainly evergreen, creeping herbaceous perennial plants and subshrubs in the family Rosaceae, native mainly to the Southern Hemisphere, notably New Zealand, Australia and South America, but with a few species extending into the Northern Hemisphere, north to Hawaii (A. exigua) and California (A. pinnatifida). The leaves are alternate, 4-15 centimetres (1.6-5.9 in) long, and pinnate or nearly so, with 7-21 leaflets. The flowers are produced in a tight globose 1-2 centimetres (0.39-0.79 in) in diameter, with no petals.