From the introduction:
"The tribe Eupatorieae forms a major part of the family Asteraceae in the Neotropical Region and has some elements ranging naturally into North America as far as Canada and into the Eastern Hemisphere. The traditional concept of Eupatorium has proven particularly defective, and the concept of the genus has been allowed to degenerate in this century to roughly include most Asteraceae lacking rays, with flowers not yellow, with leaves usually opposite, and with the pappus capillary.
Starting in 1966, and more continuously since 1970, the present authors have provided a series of partial revisions of the Eupatorieae, and an early overview of the revised concept of the tribe was presented in the symposium on the Biology and Chemistry of the Compositae (H. Robinson & King, 1977). The overall project of revising the Eupatorieae has proven vastly more complex than first expected and would probably not have been undertaken if the problems had been foreseen. A final problem has been the obvious success of the tribe in many of the least explored areas of the Neotropics and the continuing arrival in recent years of unexpected and previously undescribed elements that are often distinct at the generic level even by traditional standards.
The revised concept of the Eupatorieae accepts 103 new generic concepts, including some raised from infrageneric levels. Many additional genera such as Ageratina, Ayapana, and Campuloclinium have been resurrected from the synonymy of the traditional concept of Eupatorium. Ultimately 180 genera are accepted in the tribe, genera which we consider to represent the most workable taxonomic units of the tribe, being reasonably equivalent phyletically to what are recognized as genera in other tribes of the Asteraceae such as the Heliantheae."