 de Candolle was also among the first to recognize the difference between the morphological and physiological characteristics of organs . He ascribed plant morphology as being related to the number of organs and their positions relative to each other rather than to their various physiological properties . Consequently , this made him the first to attempt to attribute specific reasons for structural and numerical relationships amongst organs , and thus to distinguish between major and minor aspects of plant symmetry . To account for modifications of symmetry in parts of different plants , an occurrence that could hinder the discovery of an evolutionary relationship , de Candolle introduced the concept of homology . 
