igis] BROWN— PINUS STROBUS 



207 



that the greatest increase would be in cutting II. However, as 

 this was 30 feet above the ground, it is quite possible that the tissues 

 there had not yet experienced the increase in temperature due to 

 the rise of soil water in the trunk. 



The present investigation gives no reliable data as to where the 

 first phloem activity was manifest. It had occurred throughout 

 the tree on March 29, 1913. The awakening of growth began in 

 this one specimen before the first of April and was not accompanied 

 by cell division. Soil water was apparently largely instrumental 

 in its inception. 



If we refer again to table B for the data for April 12, 1913, 

 two weeks later, we may draw the following interesting conclusions. 

 The greatest diameter increase at this time is in cutting II, where 

 it has been over 100 per cent. In other words, the ascending soil 

 water may have reached the point of greatest growth (because the 

 previous year's ring was widest here) and caused a rapid expansion 

 of the tissues. In cuttings III and IV we find an apparent reversal 

 of the foregoing conditions. Cutting III has increased only 1 1 per 

 cent during the same period, while in cutting IV we find the increase 

 has been 26 per cent. This may be ascribed to two causes, either one 

 or both of which may be responsible. While the increased tempera- 

 tures may have prevailed longer in IV than in III, the amount of 

 reserve food material available was not as great. As a result, 

 growth in cutting IV may have been retarded more than it was in 

 cutting III; or cell division may have occurred in some of the cut- 

 tings and upset the equilibrium. Careful counts were made to 

 find the number of cells in the cambium and last formed phloem 

 in all four cuttings of March 29 and April 12. While slight differ- 

 ences occurred, these were not such as to warrant the conclusion 

 that cell division had taken place between the two dates. The 

 changes which occurred between March 29 and April 12 were 

 due solely to enlargement of cells already present. We must 

 infer then that the apparent contradictions of the figures in table B 

 are due to differences of available food in different parts of the tree. 



Cell division had begun in tree I by April 26. At this time the 

 activity was manifest in cutting I (table C). Here some 8-12 

 tracheids and 2 or 3 new sieve tubes were already formed. Wall 



