From 1907 to 1912 Duggar held the chair of plant physiology at Cornell University. In 1912 he became a research professor of plant physiology at Washington University, working with the Missouri Botanical Garden in St. Louis.
From 1907 to 1912 Duggar headed the department of plant physiology at Cornell University. In 1912 he became a research professor in plant physiology at Washington University, where he collaborated with the Missouri Botanical Garden in St. Louis.