182 LUTHER BURBANK 



the influence of the tomato. The tubers it grew 

 were potatoes and nothing else; their modifica- 

 tions in form and color were obviously due to the 

 lack of their natural protective soil covering. 



But the fact that the vine, handicapped by 

 lack of roots of its own kind, should have been 

 able to transform leaf buds into tuber-growing 

 aerial rootlets furnishes an interesting lesson in 

 the metamorphosis of parts. How the great 

 poet Goethe, who first expounded the theory of 

 metamorphosis of parts, and clearly recognized 

 the fundamental unity of stem and leaf and 

 flower, would have enjoyed the viewing of a 

 spectacle like that! 



Questions of Sap Hybridism 



And for the modern plant developer, the 

 strange compound vines have no less interest, 

 for they suggest a number of questions that are 

 much easier to ask than to answer. 



How, for example, was the leaf system of the 

 potato that grew the aerial tubers to know that 

 tubers were not being formed about its roots in 

 the ordinary way? It did know this, obviously, 

 else it would not have adopted the unprecedented 

 expedient of growing tubers in the air. 



It is easy to speculate, and to suggest, for 

 example, that the potato plant producing an 



