s 



CLIMATIC CYCLES AND TREE GROWTH 



selected pines in typical areas near Flagstaff, Arizona. Ring measures were 

 made upon several radials about the circuit of the trees and at different 

 heights; branches and roots were included; doubling and failure of ring forma- 

 tion were noted; the tip growth of the central axis of the tree was observed 

 for the various years of the tree's life. The identification of the year of this 

 tip growth is easy to anyone able to identify the adjacent rings. Detailed 

 reports of this investigation will be given elsewhere ] x it is enough to say here 

 that the results exceed our expectation in every respect. The uniformity in 



Radius 



Base 



line 



/^^^\r^^r 



TAD520 30 40 50 60 70 80 90 600 10 20 



Fig. 1 — Circuit uniformity in a prehistoric Douglas fir MLK-127 from 



Northeastern Arizona. See frontispiece and figure 11. 



the trees tested is beyond question. A single illustration of this sort of test 

 is given in figure 1, which shows measures in six different radials distributed 

 about the circuit of a Douglas fir, MLK-127, whose ring sequence is shown 

 in the frontispiece. 



Types of Ring Records. — While such uniformity within a tree is funda- 

 mental, we encounter certain differences in type of record in different trees of 

 a forest. Some records have the rings all essentially of the same size, or 

 presenting slow changes from one size to another depending upon the age 



1 These reports are now in preparation by Dr. Glock, to appear as a separate paper. 



