FIG. 301 TREATED INJURIES NORMALLY HEAL; UNTREATED ONES DECAY 

 A, Cross section of trunk, showing parts; a, heart- wood; b, sapwood; c, cam- 

 bium; d, bark; e t corky outer bark. B, Scar beginning to heal rapidly at the sides. 

 C, Scar three-fourths healed. D, Cross section of "blaze" on quaking aspen. 

 Note decay at ax cut. Line indicates proper shape of cavity to excavate. E, Scar 

 from cut limb fully healed. F, Opening to decayed area in log. Only a shell of 

 sound wood. 



