788 JOURNAL OF FORESTRY 



D. b. h. Number 



(outside bark) per acre 



27 01 



28 01 



29 



30 004 



Table 3. — Xuiiiber of Spruce 14 Inches and Over on s7-3 Acres, Proulix, igi8 



Cutting, by Inch Classes. 



D. b. h. Number Number per 



(outside bark) per acre acre (curved) 



14 3-91 3-47 



15 2.81 2.88 



16 2.17 2.40 



17 1.64 2. 



18 2.25 1.66 



19 1-26 1.34 



20 1 . 26 1 . 



21 59 -74 



22 51 .50 



23 32 .33 



24 16 .20 



25 13 .13 



26 13 .08 



27 0. .05 



28... 05 .04 



29 0. .02 



30 08 .01 



SUMMARY 



Certain conditions were observed and have been demonstrated ta 

 exist on the area studied, which are enumerated as progressive steps in 

 the determination of the character and ukimately the cause of the habit 

 of spiral. 



1. Spiral grain may differ in degree or direction in various portions 

 of a tree bole from the bottom to the top. This is rather the rule than 

 the exception. 



2. Spiral grain may differ in degree or direction from the center to 

 the circumference of an individual tree. This change will be recorded 

 in the bark as well as in the wood. 



3. Young trees predominantly spiral to the left and older trees of 

 larger diameter to the right. The time of this change is closely asso- 

 ciated with the change in the rate of growth, which is common to spruce 

 trees grown in the mixed forest. 



4. An average of about 52 per cent of the 2,372 spruce trees exam- 

 ined are straight enough to pass the airplane specification of i inch of 

 spiral in 20 inches. 



The result of the study made on the distribution of knots shows clear 

 lumber in the outer zone of the butt log only. It is also made obvious 

 that trees less than 14 inches in diameter at breast height are not worth 

 cutting for airplane stock. 



