The fact that the activity of the vascular cambium can be traced very precisely in its mature derivatives suggests that this meristem ought to be a useful system in which to study the control of developmental phenomena. On the other hand, its relative inaccessibility to direct manipulation and to observation are obstacles to the kind of experimentation that has been so profitable in the case of the shoot apex. It is perhaps not surprising, therefore, that there has been very little experimental work dealing with the control of developmental patterns in the cambium, while at the same time such phenomena as seasonal activation have received considerable attention. There has also been a great deal of interest in the participation of the cambium in wound reactions and healing and in the establishment of tissue unions in grafts of various types, both areas of considerable applied significance. The relatively few studies that have dealt with fundamental aspects of development in the cambium, together with information that may be extracted from a number of applied investigations, give strong indications that the experimental approach could be as valuable a tool in the understanding of cambial problems as it has been in the case of the terminal meristems.

CAMBIAL INITIATION

The initiation of cambium from the primary procambial tissues, although intensively studied from the structural viewpoint, has not been investigated experimentally to the same extent.