The genus Erythroxylum, best known for the species Erythroxylum coca  L., from which commercial cocaine is derived, contains ca. 230 species of tropical trees and shrubs, of which about 180 are found in the Western Hemisphere. These neotropical species were the focus of intense systematic and ethnobotanic study by Dr. Timothy Plowman for about 15 years until his untimely death in 1989. Because of his work, the Field Museum is the most important repository in the world of research collections and literature pertaining to the classification of this important genus. Plowman collected over 700 specimens of the genus from South America, and the Field Museum collection contains over 5,000 specimens collected worldwide.

Although Dr. Plowman succeeded in publishing about 50 scientific papers on Erythroxylum during his short career, he never was able to complete a treatment of the genus for Flora Neotropica. He did, however, leave behind massive data resources.