genial, and if the graft or bud grows at all, the union will nearly 

 always be good. Poor manipulation will often cause the failure 

 of a large percentage to grow, but it seldom affects permanently the 

 strength of the union in those grafts which live at all. 



GENERAL ESTIMATE 



Two questions emerge from the foregoing discussion. The scien- 

 tist asks what effect these observations have on the philosophy of 

 graftage. The practical fruit grower asks how these facts bear on 

 his work of grafting trees. The writer does not believe it is neces- 

 sary for every fact to be theorized, nor yet that it should be given an 

 immediate practical application. The notions of graft unions hith- 

 erto entertained by most horticulturists have been, for the most part, 

 merely theories, more or less incorrect, and these incorrect theories 

 were the less excusable because the facts were so abundant and so 

 easily to be seen. It is hoped that the simple observations of this 

 bulletin may help to clarify the common views of graftage. No 

 direct application to the practice of graftage will be attempted here ; 

 but it may be said parenthetically that this department has in hand 

 several lines of experiments bearing on the practical aspects of 

 grafting and budding. 



In conclusion we may re-state briefly the points developed: 

 (i) In hardwood graftage the cion and the stock never grow to- 

 gether. 



(2) Neither do the new layers of wood grown from the cion and 

 stock respectively unite. Instead of this, under normal conditions, 

 they are produced in perfectly continuous layers. 



(3) In the case of imperfect unions the continuity of the new 

 growth is more or less interrupted by the deposition of a certain 

 amount of loose scar tissue such as serves in the healing of wounds. 



(4) These conditions make the graft union mechanically weak. 

 All degrees of mechanical strength may be observed in graft unions, 

 ranging from those (a large number) which are stronger than the ad- 

 jacent parts of the same stems down to such as are incapable of 

 even holding themselves in place. 



(5) Incidentally it has been judged that weakness of unions re- 

 sults nearly always from physiological incompatibility of the cion 

 and stock, and very seldom from faulty manipulation in the original 

 setting of the graft. 



