DRY-KOT OF INCENSE CEDAE. 41 



Besides the trees shown in Table VIII, there were seven on the 

 intermediate area and five on the optimum area with slight wounds 

 which appeared to have resulted from lightning; but an absolute 

 determination was impossible. The meager basis in this table shows 

 practically an equal number of lightning-scarred trees in the two 

 localities. 



BREAKING BRANCHES. 



Incense cedar does not prune itself easily even when growing in a 

 dense stand, a fact attested by the persistence of the lower limbs. 

 In time, however, some of the lower branches die and break off. The 

 dead stubs then offer a point of entrance for heartwood-destroying 

 fungi ; the spores lodging in the dead wood may germinate, develop, 

 and the fungous hyphse pass through the bark and sapwood of the 

 tree into the heartwood by way of the pin knot. The pin knot in 

 this case plays exactly the same rdle as an open wound, but it must 

 be remembered that the area for lodgment of a fungous spore on a 

 pin knot that is not healed over is exceedingly small in comparison 

 with other types of wounds. On the other hand, there are normally 

 from several to many open pin knots on each tree, and every tree, 

 throughout all but the earliest years of its life, is thus exposed to 

 inoculation by fungous spores through these open pin knots. Many 

 of course heal over, but others take their places. 



OTHER CAUSES. 



Besides the causes of wounds already discussed, there are a few 

 others of minor importance. 



Strong winds will occasionally break off branches or tops, or over- 

 throw entire trees, particularly those weakened by a bad open fire 

 scar in the butt. The thick foliage of incense cedar collects a very 

 heavy weight of wet snow, often causing the tops and branches of 

 young trees especially to break off. Sometimes a falling tree will 

 rake off the limbs and part of the bark of a neighbor. Such injuries 

 are usually superficial unless very large branches have been broken 

 off or the bark has been torn away from the trunk over a considerable 

 area. 



Man is at times directly responsible for certain wounds. It is quite 

 a common sight along a newly constructed road to see bark torn off, 

 often rather high on the trunk, where the tree has been struck by a 

 flying rock from a powder blast. Some wounds result from blazing 

 trees to mark a boundary line or trail, but they are usually small and 

 rapidly heal over. 



Broken or dead tops, the cause of which is often impossible to 

 determine, are not at all rare. Trees with these injuries comprised 

 6.9 per cent of the total number on the intermediate area and 7.1 

 per cent on the optimum area. 



