38 LUTHER BURBANK 



fornia black walnut was hybridized with the 

 black walnut from the eastern part of the United 

 States. These two trees are most closely re- 

 lated species, and have diverged relatively little. 

 Doubtless the time when they had a common an- 

 cestor is relatively 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 wal- 

 nut 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 de- 

 cide as to which of the hybrids is the more rapid 

 grower. But in the matter of nut production, 

 the discrepancy was nothing less than startling. 

 For, whereas the first-generation Paradox wal- 

 nut produced, as we have seen, only occasional 

 nuts, the hybrid between the two black wal- 

 nuts it was named the Royal proved perhaps 

 the most productive nut tree ever seen. 



