No. 545] SHORTER ARTICLES AND DISCUSSION 305 



V = Relative yield. The percentage which Y is of the weight in 

 grams of the whole plant. This factor measures the 

 degree to which the plant transforms its food materials 

 into seeds rather than into foliage parts. 



P = Number of pods per plant. 



B =: Mean number of beans per pod. 



D = Disease-maturity index. The percentage which the number 

 of perfectly matured beans free of disease (anthrac- 

 nose) is of the total number of beans originally set in 

 the pods. This measures the degree to which the per- 

 formance of the plant in seed production approaches 

 its promise in that regard. It does not separate disease 

 resistance from earliness and completeness of maturity, 

 but from a purely practical standpoint this is not essen- 

 tial. By making separate counts of diseased and imma- 

 ture beans it would be possible to take account of each 

 of these factors by itself. It must be understood further 

 that the separation of diseased beans is not absolutely 

 complete. Only those are counted as diseased which 

 show to the unaided eye evidence of anthracnose infec- 

 tion. It has not been found feasible as yet to get a 

 simple and satisfactory measure of the degree of attack 

 of other bean diseases. Hence, for the present, only 

 anthracnose is being taken account of specifically in 

 the selection index number. 



These variables are combined in the following bean selection 

 index number: 



FP+ BV 

 5(100 - D)' 



The values taken by this index number for a particular strain 

 of Old-fashioned Yellow Eyes are shown in Table I. 



From the table it is clear that the index may take a rather 

 wide range of values, depending upon the character of the plant. 

 Further, the value of the index is obviously not unduly influ- 

 enced by any particular variable. The high index values seem 

 clearly to indicate the plants which are the best, taking all 

 things into account. This, of course, is the goal sought. 



It is of interest to note the values taken by the index in the 

 case of a bean of quite different type, namely, a white field 



