P. pilosa 2n=24 Turner et al. 1962; Watanabe et al. 2007

P. trinervia n=12; 2n=48; n=11, ca 22, 24, ca 24; 2n=12II ref Turner et al. 1962; Grashoff et al. 1972; King et al. 1976; Robinson et al. 1989; Keil et al. 1988

References

Grashoff, J. L., M. W. Bierner, and D. K. Northington. 1972. Chromosome numbers in North and Central American Compositae. Brittonia 24: 379-394.

Keil, D. J., M. A. Luckow, and D. J. Pinkava. 1988. Chromosome studies in Asteraceae from the United States, Mexico, the West Indies, and South America. American Journal of Botany 75: 652-668

King, R. M., D. W. Kyhos, A. M. Powell, P. H. Raven, and H. Robinson. 1976. Chromosome numbers in Compositae. XIII. Eupatorieae. Annals of the Missouri Botanical Garden 63: 862-888.

Robinson, H., A. M. Powell, G. D. Carr, R. M. King, and J. F. Weedin. 1989. Chromosome numbers in Compositae, XVI: Eupatorieae II. Annals of the Missouri Botanical Garden 76: 1004-1011.

Turner, B. L., and M. C. Johnston. 1961. Chromosome numbers in the Compositae - III. Certain Mexican species. Brittonia 13: 64-69.

Turner, B. L., A. M. Powell, and R. M. King. 1962. Chromosome numbers in the Compositae VI. Additional Mexican and Guatemalan Species. Rhodora 64: 251-271.

Watanabe, K., R. M. King, T. Yahara, M. Ito, J. Yokoyama, T. Suzuki, and D. J. Crawford. 1995. Chromosomal cytology and evolution in Eupatorieae (Asteraceae). Annals of the Missouri Botanical Garden 82: 581-592.