No. 564] STUDIES ON DIFFERENTIAL MORTALITY 



negative cases give a mean ratio of 3.70 while the 29 posi- 

 tive values give 3.75. These substantial averages taken 

 in connection with the number of rather high individual 

 ratios certainly suggest that there are real biological 

 differences between the samples of seeds. One expression 

 of these differences is seen in the fact that in some cases 

 the seeds which survive average heavier and in other 

 cases lighter than in the population from which they 

 were drawn. 



Consider now the weight relations of seeds giving 

 abnormal germinations and those failing to germinate, 

 B-C: 



+ 2.(1 



All differences 



Thus there is a deviation from equality of 7 ± 2.38 

 cases, and this is probably significant. 



For the abnormal germinations N is small; there are 

 only 12 cases in which the difference is over 2.5 times its 

 probable error. These are : 



Plus differences 11 +1.026 ! +7.39 



Minus diiirn-n.'.-, 1 -I >.+-,( ) 



All differences 12 +0.903 +6.58 



In seven series, diff. Emt. > 4. All these are positive; 

 they give a mean of 1.093 absolute and 8.47 relative. 



Thus, apparently, the seeds which germinate abnor- 

 mally are distinctly heavier than those which fail to 

 germinate. 



If now we combine A and B and compare all seeds 

 which germinated with all those which failed, we have: 



For the cases which are 2.5 or more times their prob- 

 able error: 



