Acalypha

1. Leaves cordate at the base; pistillate flowers in terminal spikes.

A. ostryifolia

1. Leaves tapering to the base; flowers all in short axillary inflorescences.

2. Petioles of larger main stem leaves 2–6 (–10) mm long, usually shorter than the pistillate bracts; widest leaves 6–11 (–15) mm wide, mostly widest near the middle.

A. gracilens

2. Petioles of larger main stem leaves 10–60 (–80) mm long, usually clearly longer than the pistillate bracts; widest leaves 12–42 mm wide, mostly widest below the middle.

3. Bracts beneath pistillate flowers mostly with 7–9 lanceolate to ovate lobes, glabrate or with a few gland-tipped hairs; blades of well-developed leaves usually less than twice as long as their petioles.

A. rhomboidea

3. Bracts beneath pistillate flowers mostly with at least 10 narrowly lanceolate lobes, bearing long straight hairs (and sometimes a few shorter gland-tipped ones); blades of well-developed leaves at least twice as long as their petioles.

A. virginica

All species found in Acalypha

Acalypha gracilensTHREE-SEEDED MERCURY 
Acalypha ostryifoliaTHREE-SEEDED MERCURY 
Acalypha rhomboideaTHREE-SEEDED MERCURY 
Acalypha virginicaTHREE-SEEDED MERCURY 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 12, 2017. http://www.michiganflora.net/genus.aspx?id=Acalypha.