THE GROWTH OF FOREST TREE ROOTS 
growing again on September 8 and continued to grow, though rather 
slowly, until November 24, after which no growth was recorded for 
any of the hickory roots. 
Quercus alba: The first observations on the oak roots were made 
on May 5. At that time growth had already started. The roots 
grew rapidly until after the first of July and then slowly until July 
28. 0-1 July 28 growth was recorded only in a single rootlet near the 
base of one of the vertical plates. No further growth was detected 
unti September 8 when it was noted that elongation had taken place 
in several roots under the vertical plates. These roots continued to 
grow during the rest of the season, but the first record of growth for 
roots under the horizontal plates was obtained on October 15. After 
this date there was growth under all of the plates until November 24, 
after which no further elongation was detected. 
Results in 19 15 
The results in 191 5 can be stated rather briefly. No observations 
were made on Tilia americana, during this year, for the reason that 
three of the preparations had been destroyed and a fungus had vege- 
tated so freely under the fourth plate that it was considered useless to 
attempt further observation. For similar reasons observations were 
made on only one tree of Acer saccharinum instead of two. 
The first observations for the year were made on March 23. At 
that time the flower buds of the soft maples were opening but no root 
growth was noted on either the maples, hickories or oaks. The first 
positive evidence of growth was obtained on April 5 on maple and 
hickory, and the first growth detected on the oaks was recorded on 
April 13. Warm spring weather began on April 5 and warm rains 
occurred on April 9 and 10. After April 13 the roots grew contin- 
uously as long as observations on them continued. At no time during 
the season when observations were made was it impossible to detect 
growth in the roots of all three species. The last observations were 
made on September 2 when the roots were still growing well. There 
was an abundance of rain throughout the season ; there was no period 
of drought. 
Tables I and II show in abbreviated form the data upon which the 
foregoing summary is based. It will be noted that the glass plates 
are designated by means of a numeral and a letter A or B. In every 
