36 



THE WHITE PINE. 



AREA ACCRETION. 



While the diameter accretion decreases in rate continuously after the juvenile stage, the 

 growth of the areas or layer of wood corresponding to the diameter increments follows by no 

 means the same course. 



After the juvenile stage, which is determined by the formation of a definite crown, and when 

 the diameter has attained at least 6 inches the cross- section area begins to increase in arithmetical 

 progression; a constantly increasing rate prevails until a maximum is attained, which comes 

 between the sixtieth and one hundred and twentieth year, and then continues remarkably uniform 

 for a long period. No decline is noticeable until after the second century has begun. In codominaut 

 au<l oppressed trees the area as well as the diameter accretion move somewhat differently, the 

 maximum rate coming later and lasting a shorter time, the decline following soon after the 

 maximum. 



FORM DEVELOPMENT, OR TAPER. 



Since size of crown and light conditions regulate the amount of diameter growth, it is evident 

 that trees with well-developed free crowns form more wood than those crowded, the dominant more 

 than the oppressed, and those on lawns more than those in the dense forest. Moreover, in these 

 latter the wood is differently disposed along the trunk than in the former. Not only do trees 

 grown in the open throw their energy into branch growth, but the accretion on the bole is laid on 

 in layers, increasing in width from top to base. The result is a more rapid taper than in forest- 

 grown trees, in which each annual layer is wider at the top than at the base of the tree, producing 

 thereby a more cylindrical form. 



The following table exhibits in the measurements of six trees this variation in the width of 

 the same annual rings at different heights, and also in general the mode of diameter growth in 

 these trees. More elaborate tables, showing the diameter growth of White Pine at various heights 

 from the ground for dominant, codominant, and oppressed trees in various parts of its range, 

 together with diagrams, will be found in the Appendix: 



Diameter growth of forett-grown trees at r-arious heights from ground. 



From such tabulations the taper, factor of shape, or form factor, may be derived (see Tables 

 II and V in Appendix), which denotes the deviation of the shape of the tree from a cylinder. 

 This factor varies between 0.40 for the older trees and larger diameters to 0.50 for younger and 



