386 
W. B. MCDOUGALL 
Results in 1914 
Acer saccharinum: Growth had already begun at the time of the 
observation on April 28. At that time the leaves were about half 
developed. The trees were through blooming and the fruit, while 
still green, was nearly mature. The branches were growing rapidly. 
The roots grew rapidly and many new rootlets were formed during 
May and June. June was a very dry month and July was still drier, 
so that by the middle of July we were in the midst of a pronounced 
drought. During the fore part of July the rate of root growth grad- 
ually lowered until by July 14 growth was almost at a minimum. 
This very slow rate of growth continued during the rest of July, often 
not more than a millimeter of elongation being detected in a week's 
time, and that only in a few rootlets. On August 6 growth had ap- 
parently entirely ceased and no further elongation could be detected 
during the remainder of August. The soil during this month was 
extremely dry. On August 28, however, it rained all day, and on 
September 8 growth had been resumed. During the remainder of 
September the roots continued to grow slowly. During the greater 
part of October no elongation could be detected, but on October 31 
some growth was detected, and this continued until the end of Novem- 
ber. No growth was detected after December i. The month of 
December was very cold, being several degrees below zero during 
part of the time. 
Tilia americana: The roots had already started growing on April 
28. They grew rapidly during May and June, but after the first of 
July the rate of growth began to lower and by July 28 all elongation 
had ceased. On September 8 some growth was again detected, and 
the roots continued to grow slowly until November 24 after which 
no elongation was recorded. 
Carya laciniosa: As in the above cases growth had already started 
on April 28, and continued through May and June. In July the rate 
of growth diminished and on July 28 it had ceased under both of the 
horizontal plates and under one of the vertical plates. Toward the 
bottom of the other vertical plate, however, the roots were still growing 
and they continued to grow unceasingly throughout the remainder of 
the summer. At no time, when an observation was made, was it 
found impossible to detect some elongation of these roots until after 
November 24. The roots under the other three plates had started 
