Biology and Philosophy 18: 249–284, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands. Plants and the Conceptual Articulation of Evolutionary Developmental Biology FRANCISCO VERGARA-SILVA * Laboratorio de Genética Molecular y Evolución Departamento de Ecología Evolutiva Instituto de Ecología UNAM; México D.F. 04510 México 1. Introduction A considerable number of biologists and a growing number of philosophers of biology are currently participating in an enthusiastic discussion of the role of developmental processes in the determination of evolutionary pattern and the phenotypic aspects of biodiversity. The main themes of this discussion are not original, 1 but most people concerned with the history of evolutionary biology – for professional reasons or otherwise – acknowledge that their current, renewed relevance is inevitable. On one hand, the existence of the molecular biology techniques that have led to the results that nowadays form the experimental core of studies in evolutionary developmental biology 2 was not even imagined when the questions first arose; on the other, an appro- priate conceptual integration between ontogeny and evolution was never fulfilled within the paradigmatic theory in the field, the Modern Synthesis (see, for example, Gilbert et al. 1996; Amundson 1998, 2001). Arguably, disagreements with the latter claim 3 and associated issues related to models of epistemological change in evolutionary biology will continue to be the main focus for philosophers and historians, regardless of the taxonomic affinity of the organisms from which the developmental-genetic data are collected (see, for instance, Robert 2001; Griffiths 2002; Love, this issue). However, since the concepts and experimental facts that give evo-devo its individuality as a scientific discourse come from the study of developmental mechanisms, it is * Current address: Department of Physiological Botany, Evolutionary Biology Centre, Uppsala University, Uppsala 75236, Sweden.