ClECtTLATlOlT OF SAP. 91 



the upward flow of the crude sap is not prevented, for it 

 passes freely through the unsevered alburnum layers, 

 reaching the leaves as usual, where it is assimilated ; but 

 the descent of the organizable matter can pass no further 

 than the annular incision in the stem ; the result is 

 that none reaches the roots, the latter perish in conse- 



VAKieATED UnSH. 



quence, and the following season the tree is dead — not a 

 bud on either root or branch survives. Those species 

 which are the most obstinate in producing suckers from 

 their roots are readily killed out by so simple an opera- 

 tion as girdling in late winter or very early spring. 



Ringing, or the removal of a ring-like piece of bark 

 ■ from a single branch of a fruit tree, or cane of a Grape- 



