214 Mendelian Tnhentance in Bryonia dioica 



These results are exhibited in Table VI. 



The following conunents may be made on the recorded figures and 

 on the interpretation suggested for them : 



(1) Since any one plant in successive seasons shows practically the 

 same ratio of two-carpellary to three-carjjellary ovaries, this ratio must 

 presumably be of a definite fixed value and must be determined by a 

 certain definite combination of factors, i.e. it is not due to any appre- 

 ciable extent to the action of environmental conditions. 



(2) The wide range in value shown in this ratio among the plants 

 of a family such as F^ x F^ (Table IV, p. 212) indicates that more than 

 one factor is probably concerned. On quite other grounds this seems 

 likely to be the case. 



It is probable, for instance, that tendencies towards reduction in 

 number of ovules and reduction in number of carpels may be 

 simultaneously manifest in certain groups of plants, especially in 

 Sympetalae (7). 



In the case under discussion it may be that a factor concerned with 

 the number of placentae in the ovary interacts with another which 

 determines the number of ovules produced, the two sets of factors 

 being jointly responsible for the condition found in the mature 

 ovary. 



The action of two factors has been hypothesised in order to show 

 the kind of explanation which may be attempted, without prejudice to 

 the employment of more than two factors. 



Many more plants than those available would be required in order 

 to determine this point. 



