GROWTH IN TREES. 



39 



These swellings were concluded at the end of 3 days, the course of 

 enlargement being much as has been previously described. The 

 record of the variation in size of the trunk during this period showed 

 that the woody trunk made a daily variation practically equivalent to 

 that of the entire tree. 



These results show that the cork in one instance was impervious to 

 water and remarkably so to the other solutions. The bast, of course, 

 takes up water readily and is easily penetrated by other solutions, 

 especially the hydroxid and ammo-acid. These results may be taken 

 to indicate the possibility of some transpiration through the bark, 

 although this matter was not tested, directly. On May 22 a dendro- 

 graph was attached to a tree about 35 cm. in diameter, standing on 

 the north-facing slope north of the laboratory, for the purpose of 



_JUNE Zl I92Q 



Fio. 16. Dendrographic record of Monterey pine No. 7, to show relative amount of variation 

 In outer and inner parts of trunk. The record for the week beginning May 24 ia for the entire 

 trunk, the bearings being taken from an inner thin layer of cork. All other records are from 

 bearings taken from the woody cylinder internal to that of 1918. The range of the daily variation 

 of the inner cylinder is seen to be less in the earlier part of the season and to decrease with the 

 season, as shown in the record for the week beginning August 30. A slight increase was seen in the 

 week beginning October 4. Variations are X 25 on a scale of 10 mm. intervals. 



measuring the relative expansion of the cork and cambium layers and 

 of the wood. The plan was to attach the instrument to the tree entire 

 and to obtain the record of the daily course of change, and then strip 

 off the bark and growing layer and place the contacts of the instrument 

 on the trunk itself. The trunk was seen to be undergoing daily 

 equalizing variations with no growth in progress. Pine No. 6, a few 

 meters distant, was still showing some accretion, but with a steadily 

 lessening rate. 



