12 BULLETIN 255, U. S. DEPARTMENT OF AGEICULTUEE. 



WINDSHAKE AND LIGHTNING NOT THE CAUSE OF PITCH SEAMS. 



The contention that windshake is capable of causing pitch seams 

 in perfect tissues of this tree is not tenable when the facts at hand 

 are considered. If this were true, freely exposed trees should con- 

 tain the greater number of pitch seams, and those in sheltered posi- 

 tions should have few or none, which is not the case. Also, Douglas 



Fig. 6. — A cross-cut showing wound caused in a young tree by the 

 larvce of the Douglas fir pitch moth. Reduced. (Original.) 



fir is generally recognized to be of more tenacious fiber than larch, 

 as is frequently illustrated in timber-sale contracts, which provide 

 for the "butting" of the latter trees over a certain size, on account 

 of depreciation in that part of the tree by " genuine windshake." 

 To the knowledge of the author timber-sale contracts contain no 

 such clause or even a similar clause concerning Douglas fir. "While in 

 the larch, recognized to be subject to windshake, owing to brittleness, 

 the damage by windshake extends but a few feet above the base, in 

 the admittedly tougher Douglas fir the damage from supposed 

 " windshake " frequently runs up to 60 and more feet. " Wind- 



