GRAFTAGE GEXEKAL 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 ma}- 

 be weak in several ways. 1, Physical weakness at point 

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

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

 find difliculty 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 X3-Iem (203) vessels 



at the point of union ; 5, 



a similar one in the 



downward flow, due to 



faulty union of the 



phloem f202) ; 6, the 



quantity of sap taken up 



liy the root ma}' 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 diflicult question because of the 

 variation between different trees and different unions of 

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



-WEEPING MULBERRY ON 

 ERECT STE.M 



