514 Report of the Depabtmext of Horticulture of the 



chosen were those supposed to be best adapted to the region. 

 Nevertheless the diverse needs of stock and cion as to soil and 

 climate and their diverse behavior as to congeniality, make the be- 

 havior of the vines in the experiment a complicated problem. 

 Table IV gives ratings indicating the vigor of varieties on the sev- 

 eral stocks. There is no way, however, of deciding how much of 

 the thrift of the vines listed depends on adaptability and how much 

 on other factors. 



Congeniality between stock and cion. — There must be congen- 

 iality between stock and cion in successful grafting — that is, top 

 and root must flourish api3roximately as if the cion were grafted 

 on its own roots. Knowledge of the habitats of species enables 

 one to predict very closely whether the varieties of that species 

 will be adapted to soil or climate, but congeniality between varie- 

 ties of different species can be ascertained only by grafting the one 

 on the other. Europeans and Californians have found that there 

 is a great difference in the congeniality of varieties on the several 

 stocks upon which Vinifera grapes are grafted. Without doubt 

 we shall find similar differences in grafting grapes of American 

 species and must ascertain by actual test what the congenialities of 

 varieties and stocks are before running risks by grafting for large 

 vineyards. 



The failures in this experiment teach little as to congeniality 

 for it is of course impossible to say, from the few plants worked 

 with, whether the failures were due to lack of affinity between 

 stock and cion or to poor material or adverse environment. Uni- 

 formly good results with a variety or a stock do indicate con- 

 geniality and adaptability to the conditions in Avhich the vines are 

 growing as well. 



In Table IV the relative ratings given the varieties on the sev- 

 eral stocks and on their own roots show the vigor of the vines and 

 where high ratings are given indicate that stock and cion are con- 

 genial and that both are adapted to their environment. The per- 

 centages are averages of all the vines of the varieties and were 

 taken in 1910 when the vineyard had reached bearing age, when 



