22 JOURNAL OF FORESTRY 



tion could well be carried on for several years in advance of the cut- 

 ting of the larger and more valuable stands of timber. 



Judging from the specimens studied, the "deadening" or girdling of 

 the tree is relatively unprofitable as a means of inducing gum produc- 

 tion, since the gum and gum ducts do not form in sufficient abundance 

 to produce a high yield. Furthermore, continuance of this method for 

 much more than one year is prevented by the death of the tree. 



The vertical method of chipping also gave a low yield. But the fact 

 that the narrow (one-half-inch) scars heal quickly might be advan- 

 tageous from a lumbering standpoint. Under present methods of 

 operation a small part of the wood immediately behind the scars, 

 usually becomes discolored (compare figs. 3 and 4 "DC"). In young 

 timber this defect as well as the irregularly arranged wood cells would 

 probably be noticeable later when the wood was cut up. Finally, 

 although growth of the tree may be little retarded, fewxr ducts and 

 consequently less storax was produced as the result of this type of 

 cutting than from the horizontal method. It is possible that chipping 

 with a French hack and broadening the scar from time to time (per- 

 haps twice a year) might increase production by the vertical scar 

 method. 



Almost double the amount of gum was obtained from the horizontal 

 method of scarifying than from either of the other methods discussed. 

 This method stimulated the formation of more wood and more gum 

 ducts, and promised a means of easily obtaining sustained yields 

 through freshening the chipping once or more each year by removing 

 a one-fourth to one-half inch chip as is done weekly in turpentining 

 pines, where the production of gum is characteristically more abundant. 



Streaks should not be cut directly above each other or at least the 

 number so placed should be reduced and they should not be so close 

 together. Groups of streaks might be staggered or otherwise arranged 

 around the tree, leaving between the streaks sufficient continuous por- 

 tions of uncut bark (in total approximately one-third of the circum- 

 ference) to insure free sap movement both upward and downward in 

 contrast to the complete cutting ofi of the downward stream which 

 occurs in the case of girdling. Cups hung to catch the exuding gum 

 would probably be advantageous, especially in the hottest weather. 



The Length of the Ducts. — No material from any of the methods 

 was available on which the total vertical length of the ducts, either 

 above or below the cuts, could be determined. Thev extended more 



