GROWTH IN TREES. 



25 



greater than 2 mm. at the upper instrument, differences which might 

 be seen in comparison of different diameters at any part of the trunk. 

 This layer showed a thickness of 4 mm. in the boring on a different 

 radius, on the lower and upper part of the trunk. 



A number of tile pipes were now sunk in the soil in an area around the 

 tree, so that water might be conducted to the absorbing roots and 3,000 

 gallons of water were poured into these holes on July 1, 1920, with the 

 result that an enlargement was visible a day later, which was slightly 



MAY 3 1920 



FIG. 5. Dendrographic records of the changes in the trunk of a Monterey pine made by the two 

 instruments attached to No. 1, as in fig. 4. Record A is from Ihe lower part of the trunk and B 

 from the higher point, for the week beginning May 3, 1920. The sheet is marked into 6-hour 

 periods and the spaces represent 10 mm.; the actual changes in the trunk being X 8. Enlarge- 

 ment and partially equalizing daily variations are displayed. 



28 1320 



JUNE 28 1920 



FIG. 6. Equalizing daily variations of trunk of Monterey pine No. 1 for week beginning June 

 28, 1920. Application of water to soil around roots after 6 p. m. on July 2 was followed by upward 

 course of record lines from both instruments. Variations X 8 on 10 mm. scale. 



greater at the lower instrument (fig. 6). Additional water was given 

 on each of the 2 days following, and enlargement continued at the upper 

 instrument until about August 16. During this period of 16 days an 

 enlargement of 2 mm. in diameter had taken place at the upper 

 instrument, 9 meters above the ground, and of 4 mm. at the lower 

 instrument, 1 meter above the ground (fig. 7). Enlargement at the 

 base continued until September 15, at which time a further thick- 

 ening of 2 mm. had taken place, making a total thickening of 9 mm. 

 at the base. Both measurements were in agreement with borings 

 taken in January and February 1921. Then followed a month of 



