Notes on Acalypha (Euphorbiaceae) in North America

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.