LUTHER BURBANK 
fornia black walnut was hybridized with the black 
walnut from the eastern part of the United States. 
These two trees are more closely related species, 
and have diverged relatively little. Doubtless the 
time when they had a common ancestor is rela- 
tively recent as contrasted with the period when 
that common ancestor branched from the racial 
stem that bore the Persian and Japanese walnuts. 
Yet the differences between the walnuts of the 
eastern and western parts of America are sufficient 
to introduce a very strong tendency to variation. 
Indeed, the result of crossing these species was 
in some respects scarcely less remarkable than 
that due to the crossing of the Persian walnut with 
the black walnut of California. 
In this case, as in the other, the hybrid tree 
proved to have extraordinary capacity for growth. 
Indeed, I have never been able to decide as to 
which of the hybrids is the more rapid grower. 
But in the matter of nut production, the discrep- 
ancy was nothing less than startling. For, whereas 
the first-generation paradox walnut produced, as 
we have seen, only occasional nuts, the hybrid 
between the two black walnuts—it was named the 
Royal—proved perhaps the most productive nut 
tree ever seen. 
I have elsewhere cited a tree, sixteen years of 
age, that produced twenty large apple boxes full 
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