118 BOTANICAL GAZETTE [FEBRUARY 
TABLE IIT. 
Stations Jan. | Feb. | Mar./April | May | June} July | Aug. | Sept. Oct. | Nov.] Dec. 
Kalispell 16.4] 21.2] 21.5] 30.3] 23.1] 26.1] 44.0] 41.2] 22.1] 25.0] 17.6] 14.6 
Marquette 16.5] 16.4] 19.7] 23.7| 27.0] 27.0] 27.6] 23.3] 22.3] 10.8] 17.5] 17.4 
Seattle 16.0] 20.7] 25.0] 29.2] 28.9] 30.9| 32.6] 29.6) 24.5] 18.4] 15.6] 15.5 
prairie condition there and on the west side of the Flathead valley. 
It must be emphasized, however, that the saturation deficit is of 
great importance only in connection with the amount of water avail- 
able in the soil. Ifthe ratio of the water obtained by the tree from 
the soil to that given off is 1: —1, then the tree is in no danger of 
desiccation; if, however, the ratio is —1:1 or 1: 1, the tree is in danger 
of desiccation. From this it will be seen that if there is in the 
soil plenty of water that the tree can obtain, there will be tree growth 
though less luxuriant, even though the saturation deficit is high. 
This accounts for the existence of trees along streams even in prairie 
regions. 
A comparison of the atmospheric deficits of Marquette and Seattle 
reinforces what was said concerning the rainfall of these two regions. 
It will be seen that both have a fairly low atmospheric deficit during 
the winter months, thus decreasing the possibility of transpiration 
at a time when the ground is cold. In the Puget Sound region the 
comparatively high temperature renders greater transpiration more 
likely than in the Marquette region, but this is offset by the fact that 
the temperature of the soil is no doubt warm, thus rendering avail- 
able for absorption some of the great amount of water that reaches 
the soil in the form of rain during these months. 
Again, a comparison of the atmospheric deficit data for the five 
growing months of the year shows a uniformly higher deficit for 
Seattle than for Marquette. This coupled with the fact that Mar- 
quette has a rainfall of 414™™ during these months against 2027” 
for Seattle makes deciduous forests possible in the former region, 
but not in the latter. 
VELOCITY OF WIND. 
Another climatic factor that is likely to play a part in the dis- 
tribution of the forest is the velocity of the wind. Perhaps the great- 
