iQiS] 



BROWN—PINUS STROBUS 



2IS 



The results given in table F are represented in graph i. The 

 abscissas indicate the daily gain and the ordinates the time inter- 

 vening in lo day periods. From the way in which the lines cross 

 and recross, it is evident that average growth intensity and the 

 actual amount of growth which is correlated with it vary between 

 wide limits during different periods. The cambium may be very 

 active for a time, then slacken in its growth, this to be followed 

 again by renewed activity, with a final slump toward the end of 



4 8 1^ I. IS 



Daily gain; one space = J 

 Graph i. — Curves of growth intensity, tree I, 1913 



zo 



the growing season. All the cuttings represent these two fluctua- 

 tions except cutting III, and this departure may be accounted for 

 through the inequahties of growth in closely neighboring parts. 



Two periodic optimums of growth intensity have already been 

 noted by others. Friedrich (7) made observations with the 

 help of cahpers, and found that in both coniferous and hardwood 

 trees there were two periods of growth, one lasting until the end 

 of May, then sinking some until the middle of June, followed later 



