Abstract

The meaning of the concept of fusion is discussed in relation with the works of Payer and those of Van Tieghem. It is pointed out that there is a difference, at the theoretical level, between the concept of fusion congénitale as defined by Payer and the concept of concrescence congénitale formulated by Van Tieghem. The former is inobservable by definition, while the latter deals with intercalary growth. For Van Tieghem, anatomy can prove the existence of fusion, even if we do not see it during ontogenesis.We distinguish three complementary methods for explaining the unions of organs: ontogenetic, typological and phylogenetic. We have attempted, not so much to defend one or other of these methods, as to show that they often invoke very different interpretations for the same morphological phenomena. It is probable that only an analysis of the writings of 19th century botanists will clarify the concept of fusion and more generally the epistemology of plant morphology