The white-rayed species complex ofMelampodium has been treated by various authors as containing one, two, or three species. A re-evaluation of the taxa in this complex by use of Chromatographic profiles of methanolic leaf extracts from numerous populations over the range of the group has revealed three distinct patterns which, along with morphological and ecological data, provide support for the recognition of three species within the group. Distributional analysis of previously and newly reported chromosome counts of 157 plants in 99 populations shows tetraploid races ofn = 20 in bothM. leucanthum var.leucanthum andM. cinereum var.cinereum to be located primarily in central and south central Texas but locally intermixed with diploid races. Interpretation of morphology, meiotic configurations, and chemical profiles confirms that these cytotypes are autopolyploid in origin and should not be given formal recognition. All data are used to interpret evolutionary relationships, and it is believed thatM. leucanthum var.argopkyllum may closely resemble the progenitor of the entire complex.