Clement W. Hamilton, A Revision of Mesoamerican Psychotria Subgenus Psychotria (Rubiaceae), Part I: Introduction and Species 1-16, Annals of the Missouri Botanical Garden, Vol. 76, No. 1 (1989), pp. 67-111
No takes yet. Share an insight, caveat, or question.
Clement W. Hamilton (1989) studied this question.
Synapse has enriched one closely related paper. Consider it for comparative context: