230 BOTANICAL GAZETTE [march 



of this sort, because the transition from early to late wood is always 

 very gradual, and it is difi&cult to distinguish the first formation 

 of late wood tracheids. Larch should prove much more satis- 

 factory for this study. But in spite of the difficulties mentioned 

 above, it was obvious that late wood formation was in evidence in 

 tree I on August 5, 191 2, and on August 13 of the following year. 

 On each of these dates all four cuttings showed some traces of it, 

 and, further, it appeared to be slightly more advanced in cuttings I 

 and II than in the ones taken lower on the bole. This was to be 

 expected from what has been previously said; late wood forma- 

 tion begins first in the upper portions of the bole. 



Primary growth in aerial parts 



Some attempt was" made in the investigations to secure reliable 

 data concerning the elongation of aerial parts. A sample plot of 

 0.05 acre was laid off on May 3, 1913, in the vigorous young white 

 pine stand mentioned previously. It included 115 trees which 

 ranged from 4 to 11 years. The soil was of medium thickness, 

 underlaid by sandstone and shale; exposure was open. All the 

 trees were seemingly vigorous. 



The trees were first examined on May 3 as to elongation of 

 aerial parts. At that date elongation had already begun in all the 

 trees on the plot, which varied from 0.5 to 2.5 inches. Greatest 

 elongation had occurred in the terminal leader, while it was less 

 pronounced in the slower growing lateral branches. The leaf 

 fascicles were in evidence, Uut had as yet attained no appreciable 

 length. 



Observations corresponding to the above were subsequently 

 made on May 30, June 17, and July 4 of the same season. Accurate 

 measurements of the terminal leader and of the preceding year's 

 growth for 50 trees were made in each case and the results collected 

 in table L. The average growth of the preceding season is con- 

 sidered as the mean of the average preceding year's growth as found 

 on May 30, June 17, aijd July 4. It is to be observed that the last 

 vary slightly, as no attempt was made to select the same 50 trees 

 on each date. The measurements are given in inches and fractions 

 of inches. 



