GROWTH AND MORPHOGENESIS IN THE CANADIAN FOREST SPECIES: VI. THE SIGNIFICANCE OF SPECIFIC INCREMENT OF CAMBIAL AREA IN PINUS RESINOSA AIT.

Analysis of the growth of four trees from contrasting situations is extended to include the specific increment of cambial area, which is a measure of multiplicative growth of the cambium. This is found to correspond to radial growth, as measured by ring width, in the upper portion of the main axis and in the branches. Like ring width it exhibits the effects of intratree suppression and of a change from a condition of suppression to one of open growth. In the branches it is dependent on the position of the branch at the time of ring formation, and in those branches that are near the top of the crown, corresponding internodal rings show a higher specific increment of cambial area than those that are suppressed by overlying whorls. It is concluded that the factors controlling multiplicative growth of the cambium are essentially the same as those controlling radial growth.