24 JOURNAL OF FORESTRY 



scarifying the trees early in the season (January, February, or early 

 March) before wood formation for the year has begun. In this way 

 the tree is apparently stimulated so that, when wood formation actually 

 begins, resin yielding tissue is formed early. In pines an increased 

 yield from the resiniferous tissue normally present before chipping is 

 also obtained. 



In red gum there are no gum ducts present in the normal unchipped 

 wood but by chipping early in the season it might be possible to induce 

 an earlier formation of ducts and an earlier yield of gum than would 

 result if the scar was cut just at the time when the weather was warm- 

 ing up and wood formation had already begun. In the material 

 studied which was chipped May 30, 1919, wood formation had appar- 

 ently begun to some extent at least. (Note wood formed before the 

 ducts, figs. 1 and 2.) There seems to be a practical confirmation of 

 the advisability of this early scarification in the fact that in this experi- 

 ment from 4 to 6 weeks elapsed before any considerable yield of gum 

 was obtained from the scarified trees. The response to the wound 

 stimulus was slow and until the ducts could be formed no appreciable 

 yield could be expected. A study of material collected through the 

 growing period would show how much time is required for duct 

 formation. Inclement weather would unquestionably retard gum flow 

 and also wood and gum duct formation so that this alone might be a 

 very significant factor. All things considered, however, cutting the 

 wounds on the gum trees early, say in February or March, would be an 

 experiment well worth trying. 



