The eighteenth-century Swiss naturalist Jean Senebier (1742–1809) is well known for his important contributions to plant physiology. Not only was Senebier a first-rate observer and experimenter himself, he was well in touch with the (observational and experimental) research of his predecessors and contemporaries. Furthermore, he explicitly reflected on observation and experimentation. As arguably the eighteenth century still remains something of a watershed in the history of scientific methodology, it is crucial that Senebier’s methodological chef d’oeuvre (whose second edition approximately counts 1,200 pages, i.e. approximately twice the length of the first edition) receives more attention than it has. There are currently two major lacunae in the state of the art. There are no systematic analyses of his observational and experimental work yet, and there is no systematic study of his L’art d’observer as a whole and its epistemological underpinnings either.