Reciprocal Influence of Scion and Stock. 285 



tive. We may assume that the initial protoplasm of all the indi- 

 viduals of a species is identical. We may also consider that 

 while the origin of a variety involves a certain change in the na- 

 ture of the protoplasm, this change may be limited to a very 

 restricted region, involving often only the protoplasm controlling 

 certain local structures or functions, as for example, the color or 

 flavor of the fruit, shape of the leaf, etc., while the rest of the 

 protoplasm making up the plant remains unchanged. When 

 by means of a graft the protoplasm of two such varieties becomes 

 continuous it is only to be expected that formative substances 

 and influences should pass freely from one to the other. Many 

 seeming illustrations of this occur. Some fruit trees, e. g., Can- 

 ada Red apple, which have a naturally straggling habit become 

 compact when grafted to more compact stocks. Many late varieties 

 are known to mature their fruit earlier when grown on certain 

 other stocks. Twenty Ounce apple, for example, ripens much 

 earlier on the Early Harvest stock than on its own. Often the 

 influence of the stock is to increase the actual reproductive tend- 

 ency, as is seen in some citrus fruits which become more pro- 

 ductive when grafted to Citrus trifoliata than on their own roots. 

 The increased acidity of apples grown upon wild crab stock is an 

 illustration of the same thing, all seeming to indicate that sub- 

 stances 01 influences of some sort, that concern certain functions 

 in the stock pass into the scion and produce similar results there. 



One of the most striking of all influences of this sort and one 

 used extensively in practical operations is the remarkable in- 

 fluence of the stock upon the fruiting condition of the scion. 

 Seedlings of the tree fruits are often many years in coming into 

 fruit. Certain apples, for example, if grown as seedlings, or 

 from grafts on seedling roots, do n:>t bear until they are ten 

 or fifteen years old, or even older, but when a scion from one of 

 these seedlings is grafted to an old bearing tree it comes into 

 fruitfulness at once. The breeder dees not wait the long time 

 necessary for his seedlings to come to fruit but he grafts them 

 at the end of the first year to bearing trees and they come into 

 fruit immediately. On the other hand if a twig from a bearing 

 tree is grafted back to a seedling its bearing will be delayed many 

 years. 



