740 JOURNAL OF FORESTRY 



cut, since the warmth of the day can then exert its influence on the 

 flow before the cooler temperatures of night check it. 



(lo) Indications were that in general the best yields came from the 

 thriftiest trees, although this was not true in all cases. 



(ii) If the yield during the season kept up as well as it started, he 

 figured that he should get 3.3 kg. per tree, or, with about 350 trees per 

 hectare, at least a ton (metric) of resin per hectare. 



Tubeuf discusses the working of spruce for turpentine, which has to 

 follow methods somewhat different from those used for pine. The 

 resin of the spruce is almost all from the secondary, or pathological, 

 ducts formed as a result of wounds to the bark and cambium. These 

 ducts are formed in the first layer of the callus which grows over the 

 wound and in the new annual ring adjacent to the edge of the wound. 

 They follow injury by frost, lightning, and drought cracks, as well as 

 other wounds. Much of the resin in wild stands is due to injuries by 

 game. The yield is small the first year and greatest the second after 

 wounding, so that the first harvest is made at the end of the second 

 year. 



The following points are noted : 



(i) Choice of stand to zvork. 



(a) Age. Only stands to be cut at the end of two years 

 should be worked. Thick-barked trees should not be worked. 



(b) Situation. Middle elevations, warm coves, and warm 

 soil give better yields than high rocky sites on cold soils. 



(2) Wounds. 



(a) Time of wounding. Should be done when the bark 

 slips, or during ]\Iay and early June. On cold sites, at high 

 elevations, in the shade, in dense stands, cutting should be 

 done later than on more favorable sites. There is as much as 

 three weeks' difference between north and south slopes in the 

 same locality. 



(b) Length of wound. The yield is proportional to the 

 length ; two meters is the most convenient length to work 

 from the ground (cuts run vertically up and down the tree). 

 It is usually not convenient to run the cuts clear to the ground, 

 because of the necessity of stooping to gather the resin. 



(c) Breadth of wound. A comparatively narrow wound 

 is as good as a wide one, since the yield depends on the length 

 rather than on the breadth of the cut. Narrow cuts do not 

 dry out so quickly, and more can be made on one tree. The 



