6 GEORGE P. BURNS 



absorption and assimilation and Pagnoul says that in the shade 

 the nitrogen salts cannot be used. 



The data on white pine show no such great differences in 

 nitrogen content in the no-shade and full-shade trees. White 

 pine seedlings contain only about three times as much nitrogen 

 when grown in the full-shade. 



The data given in this paper indicate that the explanation 

 of the differences in size and chemical composition of the three 

 groups of trees must be sought along the line of photosynthesis 

 and assimilation rather than along the line of absorption and 

 transpiration. 



