KNOT ZONES AND SPIRAL IN ADIRONDACK RED SPRUCE 



789 



Other defects shown by the study still further reduce the available 

 airplane stock. Thirty-three per cent of the 988 trees examined at 

 Cranberry Lake showed evidence of decay. Pitch seams and pitch 

 pockets are prevalent, though actual loss is difificult to compute from 

 these causes. 



Deductions for spiral, decay, pitch seams, and pitch pockets will leave 

 less than 30 per cent of the 12.57 trees shown as stand per acre on 

 Nehasane Park in its virgin condition. Of these only a low percentage 

 of the butt log will be free from knots. These facts presented are suffi- 

 cient to demonstrate the need of action to save the small percentage of 

 high-grade spruce on private holdings from going into pulp wood. 



The physiological cause of this habit of spiral growth seems to lie in 

 the change in rate of growth of the outer zone of wood over the fixed 

 core previously established. Distortion occurs while the cells are in 

 plastic condition, and light is doubtless the factor which determines the 

 direction of torsion. 



Straight-graiiK'tl clear spruce tree split in falling, showing prevalence of knots in tlie heart of 

 all red spruce. The grain of the heart spirals to the left. 



