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THE AMERICAN NATURALIST 



[Vol. XLIX 



tion, the axial position of pods being dominant. The posi- 

 tion of pods or flowers influences plant habit in this man- 

 ner: when flowers are formed at the growing- tip of a 

 main stem or branch, such a stem or branch must neces- 

 sarily cease to elongate; on the other hand, if no flowers 

 or fruits are formed at that point it may continue to grow 

 indefinitely. 



The habit of all the varieties of beans can be accounted 

 for easily with only these three character pairs. In 

 Table I the varieties here concerned have been grouped 

 according to the probable presence or absence in them of 

 the characters mentioned. 



I have designated the axial position of the pods as A, 

 the terminal position by a; long plant axis by L, short 

 by 1 ; a long axis was shown to be dominant over short in 

 some of Mendel's crosses of beans (1). I have designated 

 circumnutation by T and its absence by t, as, judging 

 from Emerson's statements, and according to my own 

 observations twining habit is dominant. The possible 

 combinations of these characters are as follows : 



rpe a comprises the pole beans, as the vines are of 

 t length, both on account of long axis and not being 



