I9I5] 



BROWN—PINUS STROBUS 



209 



It follows from table D that on May 4 cell division was going 

 on in all parts of the bole on the south side of the tree, with the 

 exception of the terminal leader. It was farthest advanced in 

 cuttings II and III, as might be expected, because the last formed 

 annual ring was thicker here than in the basal cutting. 



TABLE D 

 Extent of growth in tree ii, May 4, 1913 



The branch cuttings were made on a branch which ran out 

 some 20 feet in a southeasterly direction at a distance of 13 feet 

 above the ground. Five cuttings were taken at intervals of about 

 4 feet. In cutting I (beginning from the tip) no tracheid formation 

 was evident. In cuttings II and III tracheid formation was in 

 progress, while in IV and V (basal) enlargement of the tissues had 

 occurred, but no cell division. Cell division in the branches was 

 similar to that ia the bole, but more sluggish. It begins back of 

 the branch leader and is most tardy in the base and leader of the 

 branch. Which of the last is the first to exhibit growth depends 

 on the length and vigor of the branch. 



Numerous other observations were made on trees of different 

 ages and different locaUties. It was found that cell division may be 

 in progress some time in the upper portions of a tree while it is 

 totally lacking below. This applies especially in old mature trees 

 in closed stands, where growth is proceeding very slowly. Further, 

 in general cell division first begins on the south side of the tree and 

 in the basal portions. This peculiarity, due apparently to insola- 

 tion, has also been observed in some cases in pitch pine (i). 



It was noted in reviewing the literature on tree growth, that 

 some (14) have attempted to correlate growth awakening with 



