226 BOTANICAL GAZETTE [march 



tracheid occurred between a cambial cell and a fully formed 

 (as to size) tracheid, and occasionally here and there in a cutting 

 this was lacking entirely. Again, in the cuttings of September 19 

 of the following year the same condition of affairs existed. While 

 growth as to relative amount had to all purposes ceased, still all 

 indications pointed to the fact that in all four cuttings it was going 

 on, though very slowly. In both cases growth appeared to be most 

 sluggish in cutting III, but no reason can be assigned to account 

 for this fact. 



The data from the preceding paragraph lead to the following 

 conclusions. Xylem formation in tree I continued during two 

 successive years until the last half of September, possibly even as 

 late as October i. Further, it was in evidence throughout a large 

 part of the bole, as cutting I was 38 feet above the ground and the 

 terminal leader extended only 17 feet beyond. Whether it still 

 continued in the terminal leader cannot be concluded from the 

 present investigation. If we correlate these deductions with those 

 previously reached in the paper, the following points are evident: 

 (a) growth intensity falls off first in the upper parts of normal white 

 pine trees, more tardily below; {h) cessation of xylem formation 

 does not follow the same law, but persists sluggishly in all parts 

 of the bole (with the possible exception of the terminal leader) 

 until the latter part of September; (c) the exact time of the end of 

 xylem formation was not determined in the present investigation, 

 but it is safe to conclude that it was practically complete by 

 October i . , 



The results of the present study are contrary to those of Robt. 

 Hartig (9), who says, "Der Abschluss der Zuwachsthatigkeiter- 

 folgt oben entsprechend friiher, als unten." Too much emphasis 

 must not be placed upon this statement, because (i) Hartig made 

 external measurements only, and (2) his results may have been 

 influenced by subsequent phloem formation after xylem formation 

 had ceased. Robt. Hartig avoids the issue in part when he states 

 that cambial activity occurs in the tops of trees in Pinus silvestris, 

 Picea excelsa, and Larix decidua during the months of May, June, 

 and July, and at the base during June, July, and August. While 

 he implies also a cessation of growth, he does not say it in so many 



