In seven chapters, the formation of new roots on the existing framework of older roots (lateral rooting), and the formation of adventitious roots from other plant organs are considered. Lateral rooting and the branched structures it forms are essential ifplants are to extract water and inorganic nutrients efficiently from the soil. Lateral roots are also thought to be a source of hormones needed by the shoot system. On the other hand, adventitious rooting lies at the heart of a huge industry concerned with the vegetative propagation of desirable plant material, mostly from cuttings. But adventitous roots have another dimension, as highly diverse but functional organs of intact plants. This much neglected subject is also considered in this volume.