INFLUENCE OF THE SOIL AND STOCK. 53 



INFLUENCE OF THE SOIL AND STOCK. 



There was much truth in the remark of Bacon, that "the 

 scion overruleth the stock quite, the stock being passive 

 only." The change which takes place when the sap is con- 

 verted into the descending juices, and thence into fruit, is 

 effected entirely by the leaves; that is, when a pear is 

 grafted on a quince, the entire elaboration of the juices 

 is effected by the leaves of the pear, and the perfect fruit 

 of the pear is the result, and not a cross or mixture of 

 the two fruits. Hence the error of the notion formerly held, 

 that the stock might produce a distinct specific change, ana- 

 logous to that in hybrids. 



But although one species, or even variety, cannot be 

 changed to another by the stock which supports it, a slight 

 modifying influence may be exerted by the shade of differ- 

 ence between the sap of one species and that of another. 

 The sap of the quince may exert a sensible effect, small in 

 degree, even after it has undergone the great change which 

 is effected by the leaves of the pear. We accordingly find 

 some sorts of pear improved, and others deteriorated on the 

 quince. 



There is doubtless an analogy in the influence exerted by 

 different stocks, and by different soils. As the earth is 

 colder in summer a few feet below than near the surface, it 

 is highly probable that such soils as variously favor the 

 downward extension of roots, may modify the character of 

 fruits like the changes of seasons. Different trees of the same 

 variety are known to be affected by slight shades of differ- 

 ence, which are often ascribed entirely to the stock, though 

 the soil doubtless has a large share of influence. This view 

 is further indicated by the increased or diminished luxuri- 

 ance of some kinds when growing in a light or .a heavy soil. 

 Different degrees of fertility often produce material effects, 

 both in productiveness and flavor. 



There is no doubt that stocks on which trees are grafted, 

 operate in some degree in a similar way. Some, like a 

 rich soil, assist the more rapid growth of the branches ; 

 others, like a sterile one, retard it ; hence corresponding re- 

 salts on the fruit may be expected. 



Stocks may hasten or retard ripening ; they may affect 

 the size, color, and quality of fruit. The temperature, 



