ASPECT. 27 
and when once cleared tree growth is often difficult to renew 
As proof of the importance of these conditions as affecting tree 
growth we have the commonly observed fact that the south 
and west sides of steep hills and mountains are more likely to 
be bare than any others. This can be very plainly seen on the 
bluffs along the Mississippi River in Minnesota. 
A Western Slope receives the sun’s rays obliquely, but in 
the warmest part of the day, and in this section gets the full 
foree of our hot dry southwest winds. The effect of such an 
exposure on growth is about the same as the southern slope. 
