LUTHER BURBANK 
culties encountered in extracting the meat of the 
nut are too great. Contrariwise, a nut that has a 
shell so thin that it can easily be crushed in the 
fingers is sure to make its way and to be found 
more and more generally on the dinner-table. 
The terms “paper-shell” and “soft-shell” as 
applied to the walnut are interchangeable. There 
are now several varieties of walnuts on the mar- 
ket that are generally classified under one head 
or the other. Their name merely refers to the ease 
with which the nut can be cracked. As to this there 
is great variation among ordinary walnuts, and 
the soft-shell varieties also show a good deal of 
diversity. But the best varieties are so friable that 
they can readily be crushed in the fingers. 
In point of fact, the walnut is so variable that 
it is possible for the plant developer to consult 
his own wishes in the matter of modifying its 
shell, I have developed a variety in which the 
shell became so soft that it could readily be pene- 
trated by the bills of birds; in fact a nut that had 
a mere rim of shell, being thus comparable to the 
stoneless plum. There would be no difficulty in 
maintaining this variety of shell-less walnuts, but 
its thinness of shell was a disadvantage, and I 
found it desirable to breed the variety back to a 
somewhat thicker shell covering, by striking a 
compromise between the old hard-shell varieties 
[36] 
