Studies of three groups of North American Acalypha (Euphorbiaceae) species
are presented. Acalypha hederacea and A. monostachya have traditionally bee
n separated by plant sexuality and staminate inflorescence length, but exam
ination of specimens from throughout the ranges of these two taxa show that
they do not differ in either character. Acalypha hederacea should be treat
ed as a synonym of A. monostachya. Acalypha lindheimeri and A. phleoides su
pposedly differ in toothing of the bracts subtending the pistillate flowers
and in the shape of the leaf apices. However bract toothing is highly vari
able among these plants and leaf apex shape varies clinally, with numerous
intermediates. Acalypha lindheimeri, based on specimens both geographically
and morphologically extreme, should be treated as a synonym of A. phleoide
s. The A. virginica group has a complex taxonomic history. Taxonomic confus
ion has resulted from emphasis on characters that are unreliable because th
ey show overlapping variation among the taxa. Five species can be distingui
shed based on unambiguous, nonoverlapping characters.