1905] WHITPORD—FORESTS OF FLATHEAD VALLEY 119 
est influence the wind has on trees is to increase the transpiration, 
and they more than any other form of vegetation are subject to the 
drying effects of winds. Indeed so important does SCHIMPER (pp. 
542-555) think this factor that he considers it influential in bringing 
about the prairie condition. Below is given the mean monthly and 
annual wind velocities for the three stations. Again, there are no 
data for Columbia Falls, but the amount of wind is probably not 
very different from that at Kalispell. The figures are in kilometers 
per hour. 
TABLE Iv. 
Jan. | Feb. | Mar.|April | May | June | July | Aug. |} Sept.) Oct. | Nov.) Dec. |Ann’] 
Kaiepell, ... 500d 4.4) 7.7| 9-5] 10.4] Io.0] 10.1] 10.0] 9.6{ 9.0; 8.2] 7.2] 7.2) 8.8 
Marquette............] 17.3] 16.1] 16.7] 15.4] 16.2] 12.6] 13.8] 14.2] 16.2] 18.0] 17.7] 18.0] 15.9 
Seattle I10.3| f1.%| 16.6) TOcd|) OS] Geol 7:6f 6-6) 7.4) Svcl id. 1) 20.7; 6-39 
As shown from these figures, one of the remarkable facts about 
the Flathead valley is the absence of excessive wind. It is believed 
that this, coupled with the rather low mean monthly temperature for 
the summer months, is what makes possible so luxuriant a forest, 
with a rainfall of about 500™™. In passing from the east side of 
the Rocky Mountains into the Flathead valley, the decrease in the 
amount of wind is very noticeable. Thus, Kipp on the east side of 
the Rocky Mountains has a normal rainfall of 512™™, yet it has no 
tree growth. Although there are no data to show that there is more 
wind here than in Flathead valley, the fact is very apparent to one 
who has been in the two regions. It is believed that the excessive 
winds prevent the growth of trees, in spite of the fact that there is a 
rainfall of about 517™™, or nearly as much as at Columbia Falls. 
Compared with Marquette the wind velocity of Seattle is low. 
This would again favor a more luxuriant vegetation in the latter 
region than in the former. 
SUNSHINE. 
The more light, other things being equal, the more work trees 
can do. On clear days more food is manufactured than on cloudy 
days. This process can go on, as has been shown, during the non- 
growing season when the temperature is not too low, though the 
