Layering 



A small stream of water, uncontrolled, flows 

 on without making any attempt to overcome 

 obstacles ; but if we arrest its course the 

 accumulated water will be able to force its 

 way through the barrier. This also happens 

 with the sap. As long as it can travel un- 

 impeded in its natural course it will not turn 

 out of its way in spite of the moisture of the 

 surrounding earth, and unless the weakness of 

 the wood and bark offers very favourable 

 conditions it will not waste its energy in 

 producing roots. But if the natural course 

 of the sap is arrested it will develop ad- 

 ventitious roots in order to continue its inter- 

 rupted progress. The same result is achieved 

 by removing a ring of bark from the buried 

 part. The arrested sap forms an excrescence 

 above the cut in the bark, from which roots 

 are produced. 



Now for the application of these theoretical 

 principles. If the wood is close and refuses to 

 submit to the methods of simple layering, the 

 branch that is to be layered is strangled with 

 a wire and tightly compressed without break- 

 ing the bark. The wire must be placed above 

 a shoot and about the middle of the buried 

 part. This method of layering is called 

 wiring. 



175 



