He became an associate professor at the Ecole Normale Supérieure and then assistant director at the Collège de France, where he devoted himself to the study of plant physiology. After becoming Professor of Botany at the Sorbonne, he carried out the work for which he is best remembered. This work on phyllotaxis—observing the arrangement of the leaves on the stem of a plant—led to his theory of foliar helices ("helices foliaires"). He carried on other studies on the origin of the petals of certain flowers, and in the history of science. He was particularly interested in the eighteenth century and the botanical knowledge of that period.Trois siècles d'Académie des Sciences" court sur la période 1666-1966
