CIRCULATION OF SAP. 91 



the upward flow of the crude sap j^ 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- 



Fig. 42. VARIGATED RUSH. 



quenc^, 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 outjby.-so simple an opera- 

 tion as girdling in late winter or very early spring. 



Kinging^.or the removal of a ring-like piece of bark 

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



