580 FUNDAMENTALS OF FRUIT PRODUCTION 



readily observed, so among the effects of the cion on the stock those on 

 vigor and form of the stock are most conspicuous. 



Size and Number of Roots. — Daniel/^ working with various Cruciferse, 

 found that in some cases when the cion belonged to a species of greater 

 height than that of the stock it accelerated the growth of the latter and 

 that, when conditions were reversed, an inhibiting effect was exercised. 

 Sahut^^^ stated : "If the cion belongs to a more vigorous species or variety- 

 it stimulates the vigor of the stock. The common hawthorn, grafted 

 with hawthorn bearing double pink flowers, with Sorbier des oiseleurs, 

 Azerolier d'ltalie and the common Rohinia grafted with R. decaisneana, 

 develops much more rapidly. It is the same with the majority of Euro- 

 pean vines [grapes] when grafted on American York Madeira or Rupestris 

 stocks which are less vigorous. If the cion is less vigorous it restrains 

 the vegetation of the stock. The Dwarf peach of Orleans, grafted on 

 peach or almond, and Chinese plums on Damascene or St. Julien [are 

 examples]. It is the same with the majority of European grapes on 

 Riparia or Jacquez." 



Instances drawn from American experience are not lacking. Swin- 

 gle ^'*° states: "Although the Trifoliate is naturally a small tree and of slow 

 growth, when used as a stock its growth is so stimulated that its diameter 

 always continues greater than that of the scion. . . . This form of 

 union wherein the stock slightly outgrows the scion has been noticed also 

 in the case of the loquat grafted on the quince growing at Eustis, Fla. 

 In this case, also, the variety so grafted began to bear when still very 

 young and has borne abundant crops since." Bonns^" confirms the 

 large growth of the trifoliate stock, even while it is exercising a dwarfing 

 effect on the lemon tops worked on it. 



Brown^^ states that the Myrobalan root system is larger than usual 

 if it is worked with peach tops. 



Bioletti and dal Piaz^^ compare Zinfandel and Tokay grapes growing 

 on Rupestris St. George stocks. Here the stocks are cuttings and there- 

 fore even more comparable than most seedling stocks. The greater 

 growth of the Zinfandel top is balanced by a corresponding development 

 of the root system. 



Whether the cause be incompatibility, poor graft union or something 

 else, there is apparently sufficient evidence to warrant the statement 

 that in some cases the cion does influence the stock. Since pruning 

 the top of any tree, regardless of the stock, tends to reduce the root 

 system and since some dwarf trees are kept so only by heading back, 

 the necessity for seeking a mysterious influence is not apparent. A 

 top which will not grow vigorously may be expected to act on the stock 

 as would a heavy pruning; a top which is able to supply the roots with 

 abundant food may be expected to increase their growth. Nevertheless, 

 caution should be exercised against ascribing too much to this effect. 



