GRAFTAGE GENERAL COXSIDERATIONS I4I 



matter how closely the two kinds of cells may be against 

 each other their contents never mingle to produce a new 

 cell. Every cell is the production by division, of some other 

 cell ; never the product of fusion of two parent cells (Fig. 

 121). The commingling of stock and cion cells is purely 

 physical, not physiological. 



In budding, merely a form of graftage, the layers of 

 new growth are continuous — just as in the graft. A suc- 

 cessful bud graft cut (Fig. 116) shows precisely the same 

 conditions as in grafting, except that the line of demarca- 

 tion is less easy to see. 



The physical strength of unions is often discussed by 

 horticulturists, many of whom claim that this is a point 

 of weakness (201). Others claim that a successful graft 

 union is the strongest point of the stem. Common obser- 

 vation shows that the region of graftage is more or less 

 swollen by the deposition of woody tissue, and cross sec- 

 tions at such points show very close-grained wood. 

 Often when grafts are cut open and dried the tissues 

 check and split less at the junction point than above or 

 below, thus showing extra strength of fibers. Observa- 

 tion also shows that when winds break off branches in 

 old orchards a majority of the fractures occur not where 

 the grafts have been made but at other points. 



Yet grafts do sometimes break even after years of ap- 

 parently healthy growth. \\'hy? Possibly because of 

 physiological unlikeness or aversion (if such a term may 

 be permitted). The wound heals slowly or poorly; loose 

 primary or scar instead of stronger tissue fills the space 

 and weakness follows. Clairgeau pear on quince and 

 domestica plum on peach are familiar examples. But set- 

 ting aside such cases, if stock and cion are congenial to 

 each other and if the cion (or bud) grows at all, the 

 union should be good. Poor manipulation will cause 

 manj^ failures of grafts to grow, but will rarely affect 

 strength of union in grafts which live. All degrees of 

 physical strength may be seen in graft unions from those 



