No. 564] STUDIES ON DIFFERENTIAL MORTALITY 



757 



with the 28 given by the field test, as already done for the 

 relative means. The little table gives the results. 



For every variety except Ne Plus Ultra the differences 

 are exclusively or preponderantly negative. For each 

 of the six varieties the general average is negative in 

 sign, although sometimes very low. Such results give 

 additional force to the conclusion that there is a reduction 

 in variability due to a differential mortality. 



V. Recapitulation and Discussion 



1. This paper embodies a portion of the data of a 

 second study of the relationship between seed weight 

 and seed viability in Phaseolus vulgaris. The constants 

 are based on greenhouse plantings in sand of some 46,000 

 individually weighed seeds, chiefly of the pedigrees em- 

 ployed in tlie field experiments. 



Bearing in mind the various sources of error suffi- 

 ciently emphasized in the body of the paper, the follow- 

 ing may be said of the findings. 



2. In general the results of the first study are fully 

 confirmed. In certain particulars, however, the narrower- 

 analysis made possible by the wider materials now avail- 

 able suggests some modification and considerable exten- 

 sion of conclusions. 



3. The statement concerning means was : 



This was all that could then be said, for while many 

 thousands of individually weighed seeds were involved, 

 the number of series was too low to justify analysis into 

 the individual varieties or into groups by age of seed or 

 conditions of growth. Examined in the same manner, 

 these data show in the long run some indication of an 

 increase in the mean weight of the survivors, but no un- 



