206 Mendelian Inheritance in Bryonia diuica 



Experimentally, the nine $ plants obtained from this cross were all 

 without bloom. 



(6) S«(F,) X ,S's(i*'i) 



I 



1 I 



\SS : 2."?s : Iss 



r^ 



3 no blooin : 1 bloom 



In actual experiment, the nineteen ? plants obtained from this 

 cross are recorded as follows : 



TABLE I. 



No bloom Slight bloom Uloom 



14 2 3 



14 : 5 



Thus absence and presence of bloom on the berry behave as a pair of 

 allelomorphs and segregation of a typical Mendelian kind occurs in the 

 F^ generation. 



The fact that there is variation in the amount of bloom in F., 

 plants suggests however that the matter may not be so simple as is 

 represented above, and that more than one factor may be involved. 



B. Number of carpels (6). 



Tile ^ flowers of the two varieties ditfer in several details of struc- 

 ture, of which the most notable affects the number of placentae on the 

 ovary wall, and the correlated number of stigma-branches. 



The $ flowers of variety B have 3 stigma-branches and 3 placentae 

 with 3 gi'oups of ovules ; those of variety G have 2 stigma-branches 

 and a corresponding number of ovule groups. (Figs. 1, 2, 3, 4.) Minor 

 differences atfecting size and shape of the corolla have been ignored in 

 this investigation : the number of carpels concerned in the formation of 

 the pistil as indicated by the number of placentae and of stigma- 

 branches is the feature to which attention has been specially devoted. 



The internal morphology of the ovary of Bryony is peculiar, and 

 need not be discussed here beyond a statement to make clear the 

 nature of the differentiating features. 



Owing to the distribution of the vascular tissue associated with 

 the placentae, the ovaries in transverse section give an appearance of 



