HERMAN H. CHAPMAN 41 



by chance the fires do not run for several seasons, the ac- 

 cumulated debris may cause such a hot fire that a great 

 deal of damage is done. 



Resistance of Trees to Fire. — The amount of damage 

 done to the trees by a fire varies from total destruction 

 down to almost nothing. This depends first, on the nature 

 of the fire, and second, on the resistance of the tree. The 

 living tissue of the tree is its cambium, between the bark 

 and the wood. If this is heated beyond a certain point 

 it is killed. If the cambium around the entire base of the 

 tree is killed, the tree is girdled and dies. The cambium 

 of one tree is probably just as sensitive as that of another, 

 but these cells are protected by the bark and it is here 

 that differences exist. Bark is composed of corky sub- 

 stance which is a non-conductor of heat. The more bark 

 there is and the more corky its consistency, the better 

 will be its protection against fire. Seedlings of all species 

 are very sensitive to fire, and the slightest ground fire will 

 kill most yearling plants. But in two or three years, they 

 begin to develop thicker bark, and some of them may sur- 

 vive a light fire. The seedlings of the southern longleaf 

 pine develop thick bark and at the same time the needles 

 of the crown turn down around the stem, affording addi- 

 tional protection, so that it is no uncommon sight to see 

 these seedlings starting to grow after fires which -scorched 

 off every vestige of foliage. But with most pines, fires 

 occurring every two or three years will absolutely pre- 

 vent young seedlings from getting started. Such condi- 

 tions are found on nearly the whole of the cut-over pine 

 lands of the Lake States. The old forest has been cut, and 

 fires, by preventing the growth of the new crop, have pro- 

 duced a treeless w T aste. Many of these stump wastes have 

 been cut for 40 or 50 years, in which time a second crop 

 of pine would have reached merchantable size. Yet today 

 there is nothing and 100 years from now there will still 



