No. 545] SHORTER ARTICLES AND DISCUSSION 



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plants. They mature, 

 proportion of their seeds. 



apparently free from disease. 



Of course, the index numbers may, strictly speaking, be com- 

 pared only among plants of the same variety. The absolute de- 

 sirability of a variety for a particular purpose depends upon 

 many other factors not taken account of in the index number. 

 These numbers can not be used directly and solely as measures 

 of the relative worth of varieties. 



It is hoped that this bean selection index number or some mod- 

 ification of it may be found useful by other workers. It will, at 

 any rate, serve to illustrate further the adaptability of the gen- 

 eral idea of such numbers to a wide range of practical selection 

 work. In the present instance a selection index number is 

 applied to the measurement of the relative worth of different 

 distinct biotypes, rather than in the mass selection of fluctuat- 

 ing variations, in which latter type of work such numbers were 

 shown in our former communication to be useful. 



Raymond Pearl 



University of Maine 



