GROWTH IN TREES. 35 
ground was already saturated about the tree. The flower buds were 
beginning to move, but were not so far advanced as some that were 
seen on unirrigated land in the vicinity. The conditions were, in fact, 
as if the plant were growing along a water-course in its natural 
habitat (fig. 12). 
Enlargement began on March 10 and continued at such rate that 
an enlargement of 4 mm. had taken place by April 7, a period of 
28 days (fig. 13). A period of depression and shrinkage, for 5 days 
during a cold storm, was followed by a resumption of growth which 
continued until August 25. Another period of depression ensued, 
but 6 days afterwards enlargement was again noticeable which lasted 
for a week, and other such impulses were displayed in September and 
MAY 5-12 1919 
_ SP 
M. 6PM.12PM 6AM. Mm12PM.GAM, M. GPM12PM.6AM. M. GPM.I2PM.6AM M. 6PM12PMGAM_ M, 6PM. 12PM6AM_M. GPM, 12PM 6AM. 
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Fic. 13.—Dendrographic record of growth for the week beginning May 5, 1919, at a time when 
the daily variations were ata maximum. Relative humidity was low and transpiration was high 
during the midday period, at which time great shrinkage took place. Variations X 10 on a scale 
of 10 mm. 
OCT. 13-20 {919 
M. 6PM 12pm 6AM. M. 6PM 12PM6aM_ M. 6PM.12PM GAM M_ 6PM 12PMG6AM M. 6PM.12PM6aM M. 6PM 12PM.GAM M. 6PM. 12pm 6AM 
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5 
Fig. 14.—Variations in Arizona ash during a final period of slow enlargement near the close of 
the season, October 13 to 20, 1919. Variations 10 on a scale of 10 mm. intervals. 
October (fig. 14); after this equalizing variations of diminishing ampli- 
tude only were seen until leaf-fall occurred about November 17 to 24, 
after which the record was nearly a level line until January. 
The total increase in the diameter of the tree during the season 
amounted to about 26 mm., and a core taken from the trunk below the 
bearings on April 20, 1921, showed a layer of 12 mm. 
This instrument was replaced by a new setting on January 10, 1920, 
with an amplification of 5 times, and the record was a continued level 
line until April, when some equalizing daily variations began which 
were the only changes until June 10. An enlargement now began 
which continued until about July 20 with a depression of the rate in 
the last week in June, which may be coupled with the high temperatures 
and insufficient water supply of that period. Then followed only 
