LUTHER BURBANK 
have proved their merit, and are accepted as part 
of the necessary equipment of the plant, not sub- 
ject to the testing process that Mendelism essen- 
tially constitutes. 
Such fundamental structures are, for example, 
the root and stem and leaves and stamens and pis- 
tils of a flowering plant. As to their broad essen- 
tials of form and_ structure, these fundamental 
organs are inherited en bloc, and never jeopar- 
dized by being weighed in the Mendelian scale. 
But the newly acquired characteristics, such as 
details of leaf form, or color of petals, or size and 
quality of fruit—these are matters that are subject 
to modification because they have not as yet estab- 
lished themselves as fundamentally necessary in 
any detail of form or color to the species. These 
fall within the scope of Mendelian testing. 
For hundreds of thousands of years, doubtless, 
the progenitors of plants that now have flowers 
were provided with roots and stems and leaves, 
and with essential reproductive organs, but had no 
blossoms. In comparatively recent times the blos- 
soms were developed. And the modifications of 
color of the blossoms in the case of any given 
species are, as we have found reason to suppose, 
of still more recent origin. 
These modern details, then, and their like, are 
the ones that are subject to variation and that are 
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