1917] MOORE—CONIFEROUS FORESTS 153 
The decomposed humus was found to be neutral; the raw humus 
showed an acidity of o.002 normal, and the mineral soil an acidity 
of 0.00017 normal by CovILLE’s method. Yet by the TRuoG method 
the raw humus was strongly acid, and the mineral soil of medium 
acidity. Tests at the end of the growing season showed only a 
small diminution in acidity. 
The measurements showed that the growth of both fir and 
spruce was most rapid on the mild humus, effectually disposing of | 
the theory that acidity is required by fir, or favors the fir against f 
the spruce. In fact, the difference in rate between the neutral 
and acid cultures was greater in fir than in spruce, indicating that 
spruce withstands acidity better than fir. Growth of both fir and 
spruce on the mineral soil was slightly more rapid than on the raw 
humus, except that toward the end of the season some of the spruces 
on the raw humus began a second growth period which enabled 
them to pass those on the mineral soil. White pine also did 
better on the mild humus than on the mineral soil; on the raw 
humus there were not enough trees of this species for erie 
conclusions. | 
The duration of the period of growth in length for the different : 
species is interesting. Fir began elongating on June 1, and stopped ct 
on July ro, 40 days later; spruce and pine began on June 5, and 
did not stop until August Bese 10 aae eee ee 
_ long as that of fir. Some of the spruce on the raw owed 
a second growth period lasting until August 303 disk get 
its shorter growing period, is a faster growing tree than spruce. : a 
An examination of the root systems of the different species on — 
the different soils, made at the end of October, revealed a oe 
