CHAPTER XXXI 

 THE RECIPROCAL INFLUENCES OF STOCK AND CION 



Grafts between certain plants are successful; in many other cases the 

 results range from partial success to utter failure. Sometimes there is 

 immediate failure to unite; sometimes the grafts unite but the death of 

 either cion or stock — generally the cion — occurs in a short time; again 

 the grafted parts may unite but there will be an ultimate failure in stock 

 or in cion. On the other hand, as with apricot on plum and on peach in 

 New York, plants may live a considerable time and function fairly well, 

 under favorable conditions, without a very successful union of stock and 

 cion and it is only an untoward incident, such as a high wind, that reveals 

 the defective union. Sometimes a certain combination can be made 

 with one kind of graft and not with others — the approach graft frequently 

 succeeds when others fail. Finally, though a certain combination of 

 stock and cion may be successful it is not inevitable that a reciprocal 

 combination will succeed. 



The capricious occurrence of successful and of unsuccessful combina- 

 tions in grafting follows no well defined law. Jost^^ states the cases 

 must be accepted as they occur; they are not to be explained. DanieP" 

 explains most of them by the degree of correspondence of "functional 

 capacity" of stock and cion, i.e., that there must be, for a successful 

 graft, a certain relative similarity, qualitatively and quantitatively, in 

 their requirements for water and food and in their general habits of 

 growth. 



Botanical relationship, as understood by closeness in the system of 

 classification, is a fair guide to probable congeniality but it is by no means 

 infallible. Horticultural varieties of exogenous plants generally may be 

 intergrafted freely, species somewhat less so, genera only occasionally 

 and families only rarely. Nevertheless, the pear and the apple form a. 

 less congenial combination than the pear and the quince though the 

 pear is more closely related to the apple than to the quince. Sahut^^^ 

 states that the pear works on quince more readily than Portugal quince 

 on quince. 



THE CONGENIALITY OF GRAFTS 



Shoots of potato succeed better on Datura and Physalis than on 

 many species of the genus Solarium. According to Sahut^^s Carriere 

 grafted Garrya elUptica Dougl. on Aucuha japonica, thus uniting members 



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