In a number of recent biology meetings, plant growth factors have been a favorite topic. One may ask if a new colloquium devoted to the metab olism and the activities of cytokinins, considered at the molecular level, was really necessary and will add anything important to the previous contributions. As a matter of fact, the primary purpose of the organizers, of the French National Center of Scientific Research, and of the National In stitute of Agronomic Research which sponsored the colloquium was less the edition of a proceedings book than the desire to bring together a number of scientists...