108 



these trees were painted with white lead to prevent drying out as 

 much as possible. Figure 9 shows the condition in June of the fol- 

 lowing year. In the lower of the two cuts here shown the outer sur- 

 rounding bark has been removed, and the area of cambium and 

 xylem exposed at the time of tapping is indicated by the two streaks 

 of white paint. The size of this region as compared with surrounding 

 area is obviously several times smaller. Figure 10 shows a portion 

 of a smaller tree photographed a year after tapping when callus for- 

 mation had apparently just begun. Removal of the hard outer bark 

 showed a large triangular-shaped dead area of exposed wood. Injury 

 and exposure of the cambium obviously involves not only that por- 

 tion which is immediately injured at the time of tapping but in ad- 

 dition a considerable surrovmding area. As a consequence, callus 

 formation must begin a considerable distance back from the border 

 of the original cut underneath the bark, as is shown in Figure 10. 

 If. on the other hand, the chiclero moderates the depth of tapping, 

 and the cambium is not exposed to drying, callus formation begins 

 very shortly in the incisions. 



Another destructive result of the machete-spiral method of tap- 

 ping is that on the side of the tree where the oblique rows of cuts 

 intersect, a panel or zone is formed which is traversed by a zigzag 

 line or channel of cut bark (Figs. 2 and 3) . Each oblique row makes 

 an acute angle where it intersects the one below and above, and as 

 a result this panel includes a large number of acute angles. If the 

 cuts are deep and injure and expose the cambium, and if subsequent 

 drying out at the angles is severe, the bark of the entire zone may 

 sometimes slough off, leaving bare an irregular panel running the 

 entire length of the bole, as is shown in Figure 11. Such exposed 

 areas require many years for healing, and in the meantime wood 

 borers and fungi may get in and destroy large regions of xylem and 

 cortex. Figure 12 shows a tree that has been killed by wood borers 

 subsequent to injurious tapping. 



The ultimate death or recovery, rate of healing and bark re- 

 newal, however, are not dependent entirely on the depth and method 

 of tapping. The age, condition, and reaction of the tree itself play 

 a signficant role. Individual trees which have been carefully tapped 

 may show signs of severe injury and ultimately die, while others 

 which have been bled very severely may readily recover. This is well 

 illustrated in Figures 11 to 13. Although the tree shown in Figure 11 



