THE ROOT SYSTEMS OF FRUIT PLANTS 603 



Maynard^"^ rccommonds working Bosc, a notoriously poor growing 

 pear, into tops of strong growing varieties such as Ansault, Clapp or 

 Flemish Beauty. In sections particularly subject to pear blight, how- 

 ever, these particular frame stocks would not be advisable. Maynard 

 stated in 1909 that Kieffer had been recommended for this purpose but 

 had "not been successfully tried in the eastern states." 



It should be recorded, perhaps, that double working was advocated 

 many years ago, for increasing the quantity and quality of fruit. Graft- 

 ing in itself was supposed to have this effect and it was thought as voiced 

 by Noisette, i''2 i\^^i ^}^g more the operation was repated the greater 

 would be the improvement. In more recent times, however, the tendency 

 has been to use double working for more specific purposes, or not at all. 

 Here again, as in so many cases, distinction must be made between the 

 effects of the process itself and the effects of the material used in the 

 process. 



PEDIGREED TREES 



Observation commonly shows much individual variation between 

 the trees in an orchard that has been planted and tended with the purpose 

 of providing conditions as uniform as possible. Furthermore, these 

 differences extend to practically every feature of the tree growth and 

 they are often extreme. Naturally this has suggested the possibility 

 of perpetuating by vegetative propagation the favorable variations. 

 There has been much discussion on this question and on the value of 

 the so-called " pedigreed " trees that are grown from cions cut from indivi- 

 duals of unusual excellence. In many cases very little actual evidence 

 has been available and opinions have been based on an assumed analogy 

 between a vegetatively propagated tree and a sexually reproduced animal 

 or on theoretical considerations. 



Some Results with Citrus Fruits. — Shamel and some of his associates 

 have clearly demonstrated that in a number of the varieties of citrus 

 fruits there is a large amount of bud variation that is of real significance. 

 A number of intra-variety strains have been isolated, propagated and 

 have "bred true," if such an expression can be used for the vegetative 

 propagation employed in the citrus fruits. 



The following quotations from the reports of Shamel and his associates will 

 make clear the results of their investigation: "Thirteen important strains [of 

 Washington Navel orange] have been found in the investigational performance 

 record plots. "^^^ 



"Twelve important strains of the Valencia variety have been found and 

 described :"^^^ "The lowest percentage of off type tree, i.e. marked variations 

 from the best or Washington strain, found in commercial orchards have been 

 about 10 per cent., and the highest about 75 per cent., of the total number of 



