Probable Base Number for Genus x = 17, 18, 19
H. fasciculata n=18 ref King et al. 1976; n=19 Turner & Flyr 1966
H. schaffneri 2n=ca 36 ref Strother & Panero 2001
H. urenifolia 2n=36 ref Strother & Panero 2001
References
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.
Strother, J. L. and J. L. Panero. 2001. Chromosome studies: Mexican Compositae. American Journal of Botany 88: 499-502.
Turner, B. L. and D. Flyr. 1966. Chromosome numbers in the Compositae. X. North American species. American Journal of Botany 53: 24-33.