682 



Forestry Quarterly 



any measurements made inside the heavier line extending from 6 

 to 3 in Figure 1, i. e., omitting fiber under approximately 50 annual 

 rings from the pith. This curve cannot be taken as an absolutely 

 correct interpretation, however, since in every cross-section the 

 shorter fibers occur in the rings near the pith without regard to 

 the v/idth of the rings. Measurements must be made on very old 

 trees to definitely establish any relation between rate of growth in 

 diameter and fiber length in rings more than 50 years from the 

 pith. 



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Fig. 3. — Annual Ring Designation. 



Douglas fir. Ship. 2, tree 1. Curves showing average rate of growth in radius and 

 fiber length, by rings. The broken line is made from measurements excluding fiber under 

 50 years from pith. 



From Figure 2 there appears to be a relation between growth 

 in height and length of fiber. The curve of height growth is 

 plotted by taking the difference in age between successive discs 

 of 8 feet apart, beginning with disc A. This, of course, means 

 that a greater difference indicates slower growth in height. At the 

 butt the average difference up to 34 feet from the ground is almost 

 4; from 34 feet up to 98 feet the difference averages 2.7; while 

 from 98 feet to the top disc the average difference is more than 7. 

 Up to 34 feet, therefore, it seems that the tree was growing in 



