2l6 



BOTANICAL GAZETTE 



[march 



by another maximum again in July, and then rapidly diminishing 

 and ceasing altogether. Jost (13) has carried on observations 

 which substantiate those of Friedrich. It is remarkable how well 

 the deductions of these two investigations are brought out in 

 graph I. 



The first optimum is without doubt made at the expense of the 

 reserve food supply. It is not until June and even later that the 

 buUc of the seasonal results of metabolism in the leaves is avail- 

 able. This causes the second optimum, which may occur in July 

 or August. It might be said in this connection that the amount 

 of moisture and the prevailing temperature has been responsible 

 for the results in table G. The meteorological data which follow 



TABLE G 

 Meteorological data, season 1913 



Month 



Mean tem- 

 perature 



Predp. in 

 o.oi in. 



Month 



Jviiy 



August. . . . 

 September . 



Mean tem- 

 perature 



Precip. in 

 0.01 in. 



April 

 May. 

 June. 



SS-4 

 65.0 



1.49 

 3-iS 



.70.4 

 69.6 

 61.0 



1-59 

 1.92 

 3.28 



are the best refutation of that argument. The decUne occurred 

 in three cuttings between the middle of May and the third of 

 July, yet the temperatures prevailing were not "such as to warrant 

 this, nor was there a noticeable decline in the precipitation. My 

 observations agree with those of Friedrich, that there are in white 

 pine at least two periods of ^naximum growth. 



Irregularity of secondary growth in aerial parts 



A thorough treatment of the increase in growth in trees must 

 necessarily be very comprehensive. The study in all its phases 

 is a comparative one, for only by resorting to comparison can any 

 fundamental rules of tree growth be formulated. A comprehensive 

 study should therefore treat comparatively of the growth of (a) one 

 individual during one growing season, (6) of one individual from 

 season to season, (c) of difierent individuals in the same stand during 

 one season, and finally {d) of different individuals not in the same 

 stand. Data bearing on the first, second, and last phases of the 



