208 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



occur in a greater or less proportion among the seedlings derived from 

 black walnut trees which stand in the vicinity of English walnuts. 

 These seedlings are those which grow into the extremely vigorous trees 

 seen here and there in the State and it is certainly to be expected that 

 an English walnut upon such a root would have some unusual vigor. 

 This we have found to be the case, by grafting upon the hybrids which 

 appear here and there among the black walnuts and by planting out 

 such trees for future observation. We cannot yet say that every tree 

 upon a first-generation Paradox root will have this unusual vigor but 

 so far as our observation has gone such trees have a general tendency 

 toward such a habit. Figs. 26, 27 and 28 illustrate a case of this sort, 

 these being Placentia Perfection trees grafted at the same time, of uni- 

 form size when planted in the orchard and planted adjacent to one 

 another under uniform conditions. The tree on the Paradox root in 

 Fig. 26 is fully twice as large as the one upon the English root, and 

 decidedly larger than the one upon northern California black. That the 

 production is proportionate to the size is shown by the crop of 1911, 

 when the Paradox root tree produced 18J pounds, that upon California 

 black 12J, and that upon English 9 pounds. English walnut grafts 

 unite readily with the Paradox root, which is a very desirable feature 

 from the nurseryman's standpoint. It is not probable, however, that 

 this root will ever be largely used by the general nurseryman, since only 

 a comparatively small and very uncertain percentage of hybrid trees 

 develops in the nursery, extra work and care are required to keep 

 separate the trees on these roots from those on the straight black and 

 only one who is something of a specialist and who is able to make a 

 special effort to obtain and segregate these roots can expect to make a 

 regular practice of growing trees upon them. For such trees he must 

 obtain a greater price than that received for those on ordinary roots, 

 in view of the extra expense and care necessary to produce them. 

 Good Paradox roots are especially well adapted to light, dry, or rather 

 sandy soils, as this hybrid is particularly vigorous under such condi- 

 tions as compared to any of the ordinary walnuts. On the other hand, 

 trees of the same nature have sometimes shown themselves likewise 

 resistant to an excess of moisture. It is, therefore, likely that the 

 exceptional vigor of this root enables it to withstand any unfavorable 

 condition to a considerable extent. It is to be expected, theoretically 

 at least, that Paradox trees containing eastern blood would be better 

 for wet- land than those consisting of English and California black. 

 Much remains to be done, however, in testing out various combinations 

 and especially in testing the seedlings of various individual trees 

 under various conditions. The whole question of the value of hybrid 

 roots is indeed one concerning the progeny of individual, special trees 



