Parthenium (P. hysterophorus L.), an annual herb, is a native of West Indies, Tropical, South and North America (Arny, 1897; Castex et al., 1940; Rao, 1950; Rollins, 1950; Fernald, 1970; Dale, 1981; Haseler, 1976; McClay, 1984). It finds its first reference in Species Plantarum and classified in the family Asteraceae (Compositae), tribe Helianthea, sub-tribe Ambrosia Dhawan (1994). It has very close affinities with Ambrosia and Hymenoclea (Castex et al., 1940). P. conifertum and P. bipinnatifidum (Nath, 1981). The diploid number of chromosomes in Indian species has been reported by Hakoo (1963) to be 18(2n =18) and haploid number is to n =9.