O. chilca n= 10 + 1 I ref Robinson et al. 1989

O. heptanthus n= 20 ref Robinson et al. 1989

O. lorentzii n= 9 ref Turner et al. 1979

References

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., J. Bacon, L. Urbatsch and B. Simpson. 1979. Chromosome numbers in South American Compositae. American Journal of Botany 66: 173-178.