26 GROWTH IN TREES. 
reversible variations with some slight increases on both places on the 
trunk following a rain on October 14. Again some increases occurred, 
beginning on November 16. Similar period of increase occurred in 
December. No actual seasonal or winter shrinkages of the stem at 
either point could be detected. 
Very interesting occurrences of this sort, however, were observed in 
connection with rains. On April 15-16, December 21-23, 30-31, 
a continuous enlargement of the trunk took place which would be 
wholly or almost wholly lost on the sunny day following. 
de iad aie 6PM 6AM 6PM 6AM GPM. BAM. 6PM 6AM 6PM 6AM SPM 6am 
Dp 
6PM 6AM 6PM. 6AM 6PM 6AM 6PM. 6AM 6PM 6AM 6PM 6AM. 6PM. 6AM. 
a 5 |_—+— | [sd LL 
o_ a Le 
A 
Fig. 7.—Dendrographic record of the variations of lower and upper parts of trunk of Monterey 
pine No. 1 at end of period affected by irrigation. 
The present record is closed on January 27, 1921, at which time the 
staminate flowers were nearly mature and the terminal buds were 
beginning to swell, and some actual enlargement of the trunk had 
begun and was still in progress on January 31. 
During 1920 the basal part of the trunk had shown a total enlarge- 
ment of nearly 9 mm. in diameter, and the section 8 meters from the 
ground about 6mm. The accretion of 1920 appeared in borings at the 
base of the tree as two layers in two cores 5 and 4 mm. in thickness, 
when measured at the end of January 1921. The outer layer may be 
taken as representing accretion following irrigation, which, it may be 
suggested, may have been largely in the phloem. The borings at the 
higher point showed two layers, 4 and 2 mm. in thickness. 
Awakening of buds took place several weeks before enlargement of 
the trunk began in 1919 and 1920, but in 1921 growth of both kinds 
was apparent the last week in January, nearly two months earlier than 
the observed dates of enlargement of trunks in previous years. 
The variations of a younger tree were sought by the attachment of 
an instrument to Monterey pine No. 6 on February 12, 1920. This 
tree may be identified as beginning in 1904, as it made a second layer 
of wood in its first year and shows the extra formations in 1907 and 
1918. The floating frame of the instrument was of invar, the levers 
being set at first to amplify 5 and later to 15 times. The trunk had a 
diameter of 18 cm. and the first discernible enlargement was on 
