156 REPOET OF THE SECRETARY OF THE 



than results from increased or diminished vigor, is, perhaps, 

 the main question at issue in this discussion. 1 am not aware 

 that there have been experiments instituted for the purpose of 

 definitely settling this point, though it would not be a difficult 

 thing to do. 



The results of my own observations and experience go 

 clearly to show that the stock has an influence in determining 

 every characteristic of the fruit. Although it is not always 

 appreciable, it is often so manifest as to leave no room for 

 doubt. Indeed, I do not see how it can be otherwise. Could 

 we measure the vital forces of the stock and graft respectively, 

 exerted under the changed conditions of a united instead of a 

 separate growth, the question would be a simple problem in 

 mathematics. As it is, we can only determine approximately 

 the relative force of any two varieties in union, from observing 

 carefully the results. 



Probably some kinds of fruit, like the Rhode Island Green- 

 ing apple, have so strongly marked an individuality, are of so 

 positive and marked a type, that the variation from the influ- 

 ence of stock would seldom be appreciable ; while in another 

 variety, like the Rambo, for instance, that is easily varied by 

 conditions, it would always be more or less apparent, and often 

 very strikingly manifest ; and I have not observed any other 

 sort that exhibits so great variation from the influence of 

 stock as this variety, in all the characteristics of size, color, 

 and flavor. 



In order to secure a positive and marked variation, the 

 grafts must be set on trees of such age as to have established 

 a character and individuality of some potency, and the stocks 

 for experiment must discover strongly marked contrasts. 



Yet this variety is not alone. I find those of a more pos- 

 itive character giving every evidence of variation from the 

 influence of stock. The Northern Spy is one of these. 



I have ten trees of root-graft Northern Spy, on which the 

 fruit is always very nearly alike as to size and color, except 



