LUTHER BURBANK 
This wide diversity of form and vigor in the 
first generation hybrids is a rather unusual phe- 
nomenon. As a rule, we have observed that first 
generation hybrids are somewhat uniform in char- 
acter, and that the tendency to wide diversity ap- 
pears in the second generation. Indeed, attention 
has more than once been called to the fact that 
the discovery that such is the tendency among 
hybrids was the one that put me on the track of 
most of my successful plant developments. 
At the time when my experiments in hybridiz- 
ing the Japanese plum and the almond were com- 
menced, there were few, if any, other plant experi- 
menters anywhere in the world who seemed fully 
to grasp the principle that variation occurs in the 
second generation, and that it is by raising large 
numbers of second generation hybrids from which 
to make selection, that the development of new 
and useful varieties of plants may best and most 
rapidly be carried out. 
This principle is so familiar to-day that horti- 
culturists and botanists who refer to it very com- 
monly overlook the fact that the recognition of 
the principle is very recent. 
Twenty-five years ago I found it impossible to 
convince most well known horticulturists and bot- 
anists and biologists—with many of whom I had 
some spirited discussions on the subject—that the 
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