Specificity in Fertilization 91 



(b) foreign plants. All the fertilizations with the foreign 

 plants were successful, but the fertilizations with the 

 parents were only partly successful. According to 

 their reaction they could be divided into four groups : 



(A) fertile with both parents. Type bg 



(B) fertile with one (B), sterile with the other parent (G). 



(a) fertile with B, sterile with G. Type bG 



(b) fertile with G, sterile with B. Type Bg 



(C) sterile with both parents. Type BG 



It was found that approximately fifteen of the sixty 

 children belonged to each of the four groups. This 

 should be expected if the inhibitory substance to each 

 parent is transmitted to the children independently. 

 Half of the children will thus inherit the inhibitory 

 substance of one parent and the other half will inherit 

 the inhibitory substance of the other parent. This 

 agrees with the assumption that there are definite 

 determiners for the inhibitory substances in the child- 

 ren which will be transmitted to half of the children. 

 Rather complicated assumptions are needed to explain 

 all the facts observed by Correns on this basis and since 

 the subject is still under investigation we need not go 

 further into the details. 



To us the assumption and experimental support of 

 the idea that self-sterility is caused by the presence of 

 a substance inhibitory to the entrance of a spermato- 

 zoon is important. Should it be possible that the block 



