David Starr Jo 7^ dan 



' ' In some directions the strains of heredity are 

 much more unbalanced than in others. An im- 

 pulse from outside forces may bring about new 

 combinations. This is illustrated by De Vries by 

 a ball with many facets, which, if lightly touched, 

 will return to its original position, if vigorously 

 touched will turn over. Burbank once crossed a 

 pole bean {Phaseolus '-cidgaris) with a lima bean 

 Phaseolus liinatiis var. inacrocarpiis) . There was 

 no visible effect in the appearance of the pod or 

 the bean, but, when planted, each bean developed 

 a cotyledon, part of one species and part of the 

 other. The lima bean represented the end of the 

 cotyledon, and was united to the lower part by 

 serrated edges ; below was the smaller and striped 

 cotyledon of the pole bean. The cotyledons 

 finally parted at the joints between the two, the 

 upper portion falling off, as is often the case with 

 grafts which are uncongenial. The forms were 

 tremendously vigorous, but all came back to the 

 common pole or horticultural bean after the second 

 generation, as though it were an uncongenial graft 



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