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GROWTH IN TREES. 3l 
GROWTH OF THE CALIFORNIA LIVE OAK. 
The California live oak (Quercus agrifolia), which is one of the 
commonest of the oaks of the Pacific slope and in the region of the 
Coastal Laboratory, is a small tree with trunks 25 to 50 cm. in diameter. 
The leaves of one season remain on the tree until those of the next 
season are unfolding, which in this region begins early in February. 
The first indication of awakening activity is the elongation of the 
leafy branches which may occur in some individuals 2 or 3 weeks earlier 
than in others a short distance away. As will be seen from the records 
discussed below, enlargement of the trunk began in March, somewhat 
earlier than in the Monterey pine in the same locality. 
Measurement of this species includes one feature widely different 
from the pines, in that the bark remains alive and turgid until it 
reaches a thickness as much as 5 cm., and it is upon the surface of this 
structure that dendrographic bearings must be taken. The bark 
finally becomes deeply and irregularly furrowed, so that any single 
line around a tree may cross not more than three or four of such 
rifts, which appear to go nearly to the wood, a condition which was 
found in the first tree measured. 
A dendrograph with a floating frame of bario in the shape of a large 
U was mounted on a rectangular frame support and put in place on 
No. 1 of this tree on February 17, 1919. On March 1 a slight increase 
was recorded, but not until March 11 did positive growth begin and 
this continued until the end of May. Temperatures (1 cm. interior to 
the surface of the bark) of 7° to 9° C. were recorded during February 
and March, rising to 14° C. during the growing period. Later in the 
summer records of 18° C. were taken. 
Continuous records were kept and on February 10, 1920, the instru- 
ment was changed to one using a belt of blocks as a support for the 
floating frame of bario. No growth of the tips of the branches had 
yet taken place and temperatures as low as 6° C. were noted on several 
mornings. One record of 9° C. was taken as late as March 30 in the 
growing season. 
The daily variations in this type of tree are very slight, so that the 
record did not vary widely from a level line until March 10, when it 
began to take an upward course which was not slackened until after 
May 5. Growth was again actively in progress by the 18th, to slow 
down again by the 28th, a shrinkage of marked character taking place 
during the following week, followed by quiescence. 
Growth was resumed on June 18, but soon ceased. Another impulse 
between June 22-28, another September 25-28, were observable. A 
decided shrinkage began on September 30, which continued for 7 days. 
An increase took place during the last 10 days in October, and a very 
marked shrinkage began December 1, which continued, with some 
