A STUDY OF HEART-ROT IN" WESTERN HEMLOCK. 



35 



A pathological survey of sales areas made wHli the object in view 

 of determining the best method of incorporating sanitation clauses 

 or of establishing pathological cutting ages would be an important 

 step toward a practical and effective means of reducing thci total 

 amount of good timber going to waste every year in our forests. 

 Girdling by the ax as a method of removal of infected trees left 

 standing on a sale area is not to be recommended as an effective 

 means of control. If the situation allows of no better method, then 

 the girdling should proceed, the utmost care being exercised in 

 severing all the transporting tissues. The recuperative ability of 

 hemlock in regard to the healing of wounds is very great (fig. 13). 

 Merely cutting a cleft in the outer sapwood, leaving the chip in 



Fig. 13.— Cross sections of grand fir (at left) and western hemlock (at right), showing the result of imperfect 



girdling by the use of an ax. 



place, will not suffice. The wound is very apt to heal, and even if 

 it does not the tree may continue to live for years because the trans- 

 porting tissues have not been actually severed. It is to be remem- 

 bered that the wood of hemlock, owing to its nonresinous nature, 

 probably retains its ability to conduct water and food substances 

 longer than that of many of its associates; hence it will be found 

 necessary to insist upon thorough girdling. Some notable instances 

 of the longevity of even thoroughly girdled hemlocks and firs have 

 come to notice in which the trees continued to live for five to eight 

 years although the bark and part of the wood had been removed 

 entirely around the tree for a foot or more. Trees under the shock 

 of this wounding will sometimes produce as much seed in the year 

 following as during several years of normal life. This point is im- 



