Plant-Microbe Interactions, Volume 2 Volume 1 of this series has made its appearance and dealt forcefully with important current topics in the field of plant-microbe interactions. We believe that the quality of those chapters was high and should serve as a focal point for the state of the art as well as an enduring reference. Volume 2 builds upon these accom­ plishments. Chapter 1 discusses the fascinating lipo-chitin signal molecules from Rhizo­ bium, aspects regarding their biosynthesis, and the basis for host specificity. These molecules are a cardinal example of how microorganisms influence plant development and stimulate speculation that they have identified a previously unknown aspect of plant hormone activity. Chapter 2 continues the discussion of Rhizobium by considering the trafficking of carbon and nitrogen in nodules. Al­ though the ostensible advantage of nodules to plants is the fixation of atmos­ pheric nitrogen, the actual process involved in supplying reduced nitrogen to the plant host is complex.