132 MASSACHUSETTS HORTICULTURAL SOCIETY. 



spread with great rapidity. Its most serious damage was done by 

 its ravages on the roots. It soon wiped out many of the largest 

 vineyards of France and other European countries. For a time it 

 looked as though the whole wine industry of Europe was threatened. 

 The matter was thoroughly investigated, and it gradually became 

 known that certain American vines were comparatively resistant to 

 the attacks of this insect. Someone conceived the idea of grafting 

 European varieties on American stocks. After many failures 

 it was found that if certain strains of Vitis riparia and V. rwpestris, 

 both native American grapes, were used as stocks, that very little 

 trouble was experienced from the Phylloxera. In California 

 growers of European grapes have had the same trouble with prac- 

 tically the same results as regards successful treatment. 



In France great success has been met with by jNIillardet in hy- 

 bridizing the American with European grapes for the purpose of 

 uniting the Phylloxera resisting qualities of the former with the 

 wine producing qualities of the latter. He has also succeeded in 

 combining the above qualities with resistance to the downy mildew. 



This brings us to the question — Is it possible to obtain disease 

 resistance in an individual of one variety or species by grafting on 

 an indi^^dual of another variety or species ? There is some CAidence 

 in the affirmative but the question is at most a disputed one. It is 

 worthy of careful investigation. If such be the case would the 

 induced immunity be transmitted to offspring or to cuttings? If 

 so, then we must admit the existance of graft hybrids, which most 

 plant breeders are not willing to do. 



While comparatively little has really been done in the actual 

 development of disease resistant varieties, enough has been accom- 

 plished to indicate the possibilities. We are able at the present 

 time in certain sections of the country to advise growers of certain 

 crops what varieties to plant in order to insure a crop relatively 

 resistant to some specific disease. 



At first thought there would seem to be almost no limit to the 

 practical results obtainable. There are certain valid objections, 

 however, which stand out prominently and which cannot be over- 

 looked. 



