Douglas Fir Fiber 683 



height at a medium rate, from 34 to 98 feet at a rapid rate, and 

 from 98 to 154 feet it was growing more and more slowly in height. 

 The dot-dash line in the curve indicates the reciprocal of the rate 

 of growth in height. Comparing this condition with the average 

 fiber length at various heights, it will be seen (Fig. 2), that the 

 fiber length is short at the butt end, but increases to a maximum at 

 42 feet from the ground ; from 42 feet to the top there is a steady 

 decrease which is, apparently, more rapid after about 90 feet 

 from the ground. While it appears from this that the more rapid 

 the growiih in height the longer will be the fiber, it must be taken 

 into account that the fiber measured at any particular height 

 from the ground may have been formed long after the growth in 

 height had passed this point. Here again further determinations 

 must be made before the relation between fiber length and growth 

 in height can be positively established, although the indication is 

 that the greater the latter the greater will be the former. 



In the tree as a whole the fibers in the first year's growth, i. e., 

 in the annual ring surrounding the pith, show the shortest figures 

 for length. From the first year to about 50 years (see Figs. 4, 5 

 and 6 as average examples), the increase in the length of fiber is 

 very rapid each year, but after the fiftieth ring from the pith the 

 length in any given cross-section seems to be comparatively con- 

 stant. In some cases the rings nearer the bark show a slight 

 increase of decrease. Comparing the average of all measure- 

 ments made in each annual ring, as stated in Table I and as illus- 

 trated in Figure 3, it is found that there is apparently a very rapid 

 increase up to about 100 years from the pith, and then a constant 

 slight increase in the length of the fibers to the periphery. The 

 true condition is shown better in the curve which includes only 

 mature wood, i. e., over about 50 years from the pith, than in the 

 general curve of all figures, since the data from which this general 

 curve was obtained when averaged gives too much weight on the 

 short fibers in the disc containing the lesser number of annual 

 rings. The method of choosing points for measurement as shown 

 in Figtue 1 explains the reason for this. In the curve of mature 

 wood it is seen that the fiber reached very nearly its full length at 

 50 years, rather than 100 years from the pith, and the increase to 

 the periphery is constant but small and growing smaller till in the 

 very outermost rings it is practically nil. 



The final average of all fibers measured is 4.46 mm, the average 



