75 



the steps to be adopted. We can, as it were, roll out 

 the bark of the tree, as in fig. 27. The line a b repre- 

 sents the line at which the bark has been cut open ; 

 in the second figure is shown the bark which has 

 been rolled out; the lines a b and a' b' were, there- 

 fore, originally joined together; c is the heart wood 

 of the tree. 



Tapping systems can be divided into two main groups : 



1. One in which the bark is cut open over the whole 

 surface of the trunk. 



2. Another in which the surface bark is divided into 

 vertical strips, one or more of which are not 

 immediately tapped. The cut then ends in a ver- 

 tical cut, which we may call the "conductive canal". 



In this group we can distinguish the following types: 



a. Those in which the cuts run in two different 

 directions, lying on both sides of the conductive 

 canal, and terminating in it. 



b. Those in which the cuts run in two different 

 directions and all lie on the same side of the canal 

 in question. 



To the first group, belong the spiral type; to the 

 second, the V-cut, and the herringbone; to a third, the 

 half V-cut, the half spiral, and the half herringbone. 



