The posting below on Herbaria-L alerted me to this book:
Rios, M., M.J. Koziol, H. Borgtoft Pedersen & G. Granda (Eds.). 2007. Plantas útiles del Ecuador: aplicaciones, retos y perspectivas/Useful plants of Ecuador: Applications, challenges, and perspectives. Corporación Sociedad para la Investigación y Monitoreo de la Biodiversidad Ecuatoriana (SIMBIOE). Quito, Ecuador. 652 pp.
I should think that many historians of natural history and especially of medicinal plants, whether or not they have a special interest in Latin America, would be interested. At $33US for 650pp, it's a bilingual bargain.
Karen