262 TRANSACTIONS OF THE 
for the seasons of 1909 to 19138, inclusive, with the precip- 
itation records for Missoula, the author concludes that 
the current growth is conditioned by the rainfall of the 
preceding growing season, namely, April to September, 
inclusive. This theory is supported by the argument 
that, in view of the fact that the main growth of trees 
is completed during the early part of the growing season, 
the season’s growth must be largely dependent upon the 
nutritive substances which are elaborated and stored 
mainly in the buds and the extremities of the main shoot 
and branches during the preceding growing season. The 
author contends that the greater the supply of moisture, up 
to an optimum amount, the greater is the reserve of stored 
food and consequently the more vigorous are the shoots 
of the following season. The work of Pearson® at the 
Fort Valley Forest Experiment Station in northern 
Arizona is somewhat contradictory of Kirkwood’s con- 
clusions. Pearson’s results, based on 95 carefully selec- 
ted saplings and covering the period from 1909 to1917 
inclusive, clearly show that the April and May precipita- 
tion is most important in determining the amount of 
height growth and presumably also the amount of avail- 
able moisture in the soil during the period in which height 
growth actually occurs. 
Brewster,’ after correlating 153 measurements of 
height growth in western larch (Larix occidentalis) with 
temperature, relative cloudiness, and precipitation records 
at the Priest River Forest Experiment Station in northern 
Idaho for 1912 to 1916 inclusive, concluded that the 
most favorable conditions for rapid height growth in that 
region are produced by a combination of temperatures 
somewhat above average, coupled with a high percentage 
of clear days, with a normal amount of precipitation 
evenly distributed in the form of good rains at intervals 
8Pearson, G. A. The Relation Between Spring Precipitation 
and Height Growth of Western Yellow Pine Saplings in Arizona. 
Journal of Forestry 16: 677-689. 1918. 
Brewster, D. R. Relation Between Height Growth of Larch 
Seedlings and Weather Conditions. Journal of Forestry 16: 861- 
870." T9138, 
