The chapters in this book are centered around the structure of tissues, an intermediate and neglected level between overt morphology and biochemistry, and will be of great interest to all those engaged in attempting to understand the principles behind plant development. The author's purpose is to predict what should be looked for on a molecular level so as to account for observable forms. Each chapter deals with a defined problem such as the role of hormones as correlative agents, tissue polarization, apical meristems and cell lineages. The final chapter develops an alternative approach to the problem of the specification of biological form, that of "epigenetic selection."