FURTHER NOTES ON THE EFFECT OF EXPOSURE ON 

 WHITE PINE SEEDLINGS 



By E. A. ZiEGLER 



Since the earlier experiments (See F. Q. Vol. XII, pp. 31-33) 

 in exposing White pine seedlings to determine the amount of dry- 

 ing out they may safely undergo, a new series of tests was made in 

 the Pennsylvania State Forest Academy nursery at ]\Iont Alto 

 during the fall of 1913 and summer of 191-1. Mr. Thomas C. 

 Harbeson, of the class of 1914, carried out the tests as a thesis 

 assignment in a very painstaking and accurate way, and the re- 

 sults are taken from his manuscript. 



Since the earlier experiments noted above applied to exposure 

 on an average sunny day. an effort was made to examine the effect 

 of differing weather conditions. In the earlier sunny day experi- 

 ments the loss became marked beyond an exposure of forty min- 

 utes, the data of the two experimenters being corroborative. 



The outline in the latest experiment provided for three series of 

 exposures as follows. 



Series I. On a calm sunny day. 

 Series II. On a calm cloudy day. 

 Series III. On a sunny day with high wind. 



These series cover the general weather conditions met with in 

 planting seedlings, excepting the rainy day when the loss due to 

 exposure is at the minimum. If the limits of exposure are estab- 

 lished for the less favorable weather conditions, they obviously 

 will be safe for the more favorable conditions. 



The trees for the three series were taken from the seed beds 

 in the fall and heeled in over winter, thus diff'ering from the 

 earlier experiments where the trees were taken from the seed bed 

 in the spring immediately before exposing and planting. To 

 study the eft'ect of fall and spring exposure on heeled-in seedlings, 

 each of the above three series was subdivided into : 



a) A single fall exposure with no spring exposure 



b) A single spring exposure 



c) A fall exposure and a second exposure in the spring. 



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