GROWTH IN TREES. 37 
GROWTH OF A BEECH TREE. 
An instrument with a floating frame of bario of the U-form was 
put in place on a beech tree (Fagus grandifolia) on the grounds of 
Johns Hopkins University at Baltimore on April 16, 1919, about the 
time development of the leaves was beginning. In addition to the 
somewhat irregular daily variations swellings were seen as a conse- 
quence of rains with subsequent shrinkage. Not until May 18, when 
the tree was in full leafage, did some increase show in the record. 
This continued until May 30, after which equalizing variations ensued, 
which continued until mid-July. A week of rains was followed by 
enlargements which continued for a month and had a net total of 
about half that of the spring growth in May and June. 
Now followed a period of regular equalizing daily variations, which 
terminated about September 14. The ensuing enlargement, which 
lasted for 3 weeks, showed a total increase less than in the preceding 
active period. Only equalizing variations were now seen and the in- 
strument was dismounted early in October. The total accretion to 
the diameter amounted to about 4.5 mm. (fig. 15). 
EQUALIZING DAILY VARIATIONS IN DIAMETER. 
The equalizing changes in the trunk are such that the diameter is 
least at midday or in the afternoon, when the temperature of the trunk 
is highest. The difference between the readings of a thermometer 
thrust under the bark in early morning and at noontime is never more 
than 8° C. or at most 10° C., while that in the center of the trunk may 
be no more than a degree or two. » Whatever the temperature might 
be, a rise would tend to expand the woody column. Dendrographic 
and other measurements show a decrease at this time. The trunk is 
seen to shrink at a time when the temperature is highest. It is obvious, 
therefore, that we must look to causes other than a direct temperature 
effect. 
The first possibility to be tested was that of the water relations of the 
bark, and Monterey pine No. 7 was chosen for this purpose. A small 
section of bark and bast was removed from the north side of the tree 
below the instrument, and these two formations were separated and 
placed under the auxographs in the dark room in which swelling liquids 
now stood at 12°C. The results are as below: 
Constituents. Bast. Cork. 
Waterss sssigiene were 12.5 p. et. 0 p. ct. 
HCl .O1N........... 5 20 
NaOH .O1N......... 7.5 15 
Glycocoll .01 M...... 10 10 
