18 THE BEAVER 
! * 
ir 
et 

Fic. 7. Map or Nort America SHOWING DISTRIBUTION OF BEAVER AND OF 
THE ASPEN 
map. It is the most widely distributed tree in North America. The genus Betula, comprising the 
various species of birch, is found ‘over most of this same are ) ssl- 
bly found farther south than the aspen, though not extending as far into the northwest. In the north 
certain species of birch are important food trees o 
Pacific Coast regions are of no importance whatever. : 
This map is reproduced by courtesy of the Biological Survey, U. S. Department of Agriculture. 
