5. Acalypha rhomboidea Raf. (three-seeded mercury, rhombic copperleaf)

A. virginica L. var. rhomboidea (Raf.) Cooperr.

Map 1653, Pl. 376 a–c

Stems 15–60 cm long, glabrous or moderately to densely pubescent (sometimes in vertical lines) with short, strongly curved hairs, occasionally with a few longer, straight hairs toward the base. Leaves long-petiolate, the petiole slightly shorter than to slightly longer than the blade, much longer than the inflorescence bracts. Leaf blades 1–10 cm long, broadly lanceolate to ovate or rhombic, angled to broadly angled at the base, tapered to a sharply pointed tip, the margins with several (mostly 8–12 on each side) often relatively closely spaced, usually blunt teeth, relatively thin-textured, the surfaces sparsely pubescent with relatively straight, more or less appressed hairs. Inflorescences entirely axillary spikes, 1–3 per node, each with 1–3 basal pistillate flowers below few to several nodes of staminate flower clusters, the tip of the spike not or only slightly extending beyond the bract. Inflorescence bracts 4.5–25.0 mm long, appearing more or less folded longitudinally around the inflorescence, with (5–)7–9(–11) narrowly lanceolate to oblong-lanceolate lobes, the margins sparsely to moderately hairy, often some of the hairs gland-tipped, the outer surface glabrous or sparsely hairy, sometimes some of the hairs gland-tipped, lacking minute, sessile, reddish glands. Fruits 1.5–2.3 mm long, 3-locular, usually 3-seeded (rarely 1 of the ovules aborting), the surface moderately to densely hairy, lacking tubercles or slender projections at maturity. Seeds 1.3–2.0 mm long. July–October.

Scattered throughout the state (eastern U.S. west to North Dakota and Texas; Canada). Banks of streams and rivers, margins of ponds and lakes, bottomland forests, mesic upland forests, and moist depressions of upland prairies; also crop fields, fallow fields, old fields, railroads, roadsides, and disturbed areas.

Cooperrider (1984) pointed out problems in distinguishing A. rhomboidea from A. virginica and treated it as a variety of that species. However, based on his quantitative morphological studies, Levin (1999a) disagreed, noting that not all of the traditionally used qualitative features contained consistent differences between the species but that others served to uniquely differentiate them.