PINUS BANKSIANA IN MINNESOTA 113 



throughout the region in localities suitable for its development, 

 namely on the sandy soils which occur near extensive outcrops 

 of sandstone. 



That no more relics of it occur is to be explained by the theory 

 that fires and competition with deciduous forest trees drove it 

 out of all other locahties, for it could not, Uke the white pine, 

 take refuge on rocky dolomite ledges of the river bluffs, the soils 

 of such places not being favorable for its growth. In the single 

 place where it is still holding out, the soil is too sandy for other 

 native trees to compete with it successfully and moreover fires 

 from the southwest are effectively blocked by high sandstone 

 edges and probably also by the late lying snows of spring on the 

 upper, more abrupt portions of the north-facing hill. 



