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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