PERIODICAL literature; 741 



best width is between 3 and 5 centimeters, which can be 

 scraped easily and is not covered too quickly by the callus. 

 Resin production ceases as soon as the wound is closed. 



(d) Exposure. There is no apparent difiference in yield 

 from the different sides of a tree, but direct sun on the cut 

 causes it to dry out quickly and thus hinders resin production. 



(c) Number of wounds. There is no objection to four 

 cuts on the same tree at once. How many more may be made 

 is not known. 



(/) Tools for cutting. A strong garden knife or prvming 

 knife is all that is needed. The wound consists only in peel- 

 ing off a long strip of the bark without injuring the wood. 



(g) Choice of trees to work. Only those from which bark 

 cuts and strips off easily should be worked. 



3. Gathering the resin, (a) Time to gather. Production continues 

 to the end of September or early in October if the weather is warm. 

 The resin may be gathered after production ceases, or, if there is no 

 danger of its being stolen, it may beieft until the following spring. A 

 considerable quantity of resin is produced the second year, and should 

 be harvested the same fall, during warm weather, because in cold 

 weather it becomes so brittle as to fly all around when scraped. Not 

 only is much lost in this way, but it injures the eyes of the workers. 



4. Yields. From sample plots cut in 1916 and harvested in May, 

 1917, the yield per cut varied from 18.35 grams for cuts i meter long 

 by 5 centimeters wide to 35.04 grams for cuts 2 meters long by 5 centi- 

 meters wide, or, roughly, .035 gram per square cm. The resin was 

 gathered again in October, 19 17, and the total yields for the year (two 

 crops) averaged o.i gram per square cm. 



5. Effect on health of tree and quality of wood. In case of pine, the 

 resin impregnates the wood below the wounded surface and prevents 

 drying and the entrance of fungi. It does not do this in the case of 

 spruce, since the wound aft'ects only the bark and the layer of new 

 wood, where there are no vertical resin ducts and few horizontal ones. 

 Little resin exudes, but the face of the cut is dampened by sap and 

 becomes a fertile breeding ground for fungi. The wood below the cut 

 dries out clear to the heartwood, and the substitution of air for water 

 in the cells allows the entrance of wood-destroying fungi. Moreover, 

 small checks produced by drying also favor the entrance of fungi. 

 Discoloration of the wood with fine mycelium in the parenchyma tissue 

 of the medullary rays and tracheids follows, often as early as the 

 second summer. In the earliest stages the wood is not particularly 



