MORTALITY OF WHITE-PINE AND RED-PINE PLANTATIONS 315 



The greater part of the precipitation in June came during the latter 

 part, and no doubt is the direct cause for the continuance of height 

 growth to the middle of July, whereas it ordinarily ceases early in the 

 month. 



Investigations by H. P. Brown- (1912-1913) of the growth of white 

 pine show very similar results, though the period of height growth ter- 

 minates sooner than in the case of the trees for the season of 19 15. 

 The conclusions derived from those investigations are, first, that the 

 cessation of growth in the length of shoots of white pine occurs during 

 the early part of July, and, second, that the elongation of the leaves 

 does not cease until around the middle of August. 



The longer period during which height growth occurred during 19 15 

 is no doubt directly due to the abundant rainfall of this season. Al- 

 though the rainfall throughout July was exceedingly heavy, the in- 

 herent qualities of the stock cause the height growth to fall off and 

 later cease, regardless of the amount of rain. 



The temperature was below normal except for April. For this 

 month it was seven degrees Fahrenheit above normal, and with ade- 

 quate moisture was extremely favorable for the establishment and de- 

 velopment of the planted stock. While the temperature was below 

 normal for the other three months, there were no protracted periods of 

 cold weather, and the range was much above that necessary for the 

 growth of the young pines. The few degrees registered under normal 

 for May, June, and July have had. apparently, a negligible effect, so 

 far as retarding height growth. 



In conclusion, the uniformity of the periods of height growth of all 

 grades of healthy stock of both species shows clearly the extent to 

 which temperature and rainfall influence this growth. 



Very little can be proved with the three-year white pines, since their 

 physical condition when planted was so poor that such conclusions can- 

 not be drawn. 



When rainfall and temperature are close to normal during the grow- 

 ing season, good height growth of young pines will take place in this 

 locality. Heavy rainfall has a more })ronounced effect than high tem- 

 perature, and is of particular influence in prolonging the growth of pine 

 transplants beyond its normal period of height growth. Tlowever, con- 

 clusions from this study would show that growth of the leading shoot 

 will cease around the nn'cldle of Tulv. no matter how abundant the rain- 



'' Brown, H. P., 1014 : "Growth Studies of Forest Trees — PitniA- strohus." 

 Thesis for Dcj^rcc of Doctor of Philosophy in Botany, Cornell ITniversity, 1014. 

 (Unpuhlishrd.') 



