GRAFTAGE GENERAL CONSIDERATIONS 



143 



stronger than the contiguous parts of the same stems to 

 those incapable of holding themselves in place. 



201. Physical strength of graft unions. From the 

 standpoint of plant anatomy and physiology grafts may 

 1>e weak in several ways. 1, Physical weakness at point 

 of union ; 2, cion leaves may find it difficult to elab- 

 orate sap taken up by stock roots ; 3, stock roots may 

 find difficulty in assimilating plant food elaborated by the 

 leaves ; 4, there may be 

 an interruption in the 

 upward flow of sap due 

 to faulty connection of 

 the xylem (203) vessels 

 at the point of union ; 5, 

 a similar one in the 

 downward flow, due to 

 faulty union of the 

 phloem (202) ; 6, the 

 quantity of sap taken up 

 by the root may be too 

 much or too little for the 

 proper supply of the 

 cion ; 7, the amount of 

 elaborated sap from the 

 cion may be either too 

 much or too little for 

 proper feeding of the 

 stock. 



Concerning these points N. O. Booth of the Oklahoma 

 station has been conducting experiments upon which 

 he has made a progress report from which the following 

 points are taken. Unfortunately, a fire destroyed later 

 material and data, so the preliminary report is obliged to 

 stand by itself. 



Physical weakness is a difficult question because of the 

 variation between different trees and different unions of 

 stock and cion. To test it, the wood of 10-year-old 



127 WEEPING MULBERRY ON 

 ERECT STEM 



