342 Sex Characters in Begonias 



words a disturbance in the regularity of the qualitative cell divisions by 

 which the male and female sex organs are normally differentiated out 

 into different flovv'ers. 



A further stage in abnormality may be the appearance of male 

 gamete bearing organs on female flowers, or more rarely the appearance 

 of female gamete bearing organs on male flowers. 



Finally, a complete ring of stamens, functionally active, may surround 

 the gynoecium of a flower of female type. (PL XVI, fig. 7.) 



This association in the same flower between abnormalities of ac- 

 cessory and of essential floral parts is important because it shows that 

 instability of equilibrium in the primary sex elements carries with it in 

 nearly all cases instability of equilibrium of somatic tissues also. 



The association between sexual instability or hermaphroditism and 

 modification of accessory floral parts is also shown genetically thus: — 

 The Fi seedlings of a cross between a Begonia with double male flowers 

 as the seed parent and a single flowered variety as the pollen parent 

 are for the most part single flowered plants. A certain number, how- 

 ever, show indications of a tendency to doubleness by the presence of 

 one or two extra petals in the male flowers, while others exhibit an 

 elongation of the axis which bears the otherwise normal stamens. In 

 other words singleness is only partially dominant over doubleness in the 

 F^ generation of such a cross. 



Of the seedlings of the F., generation so raised an abnoimal per- 

 centage shows a tendency to hermaphroditism and abnormal flowers. 



It is more difficult by cross fertilization to transfer the ddiible 

 character to female flowers, that is to convert a sex limited character 

 like doubleness in the Begonias, into a specific character. In the female 

 as in the male flower however the earliest indication of sexual instability 

 or hermaphroditism is often the presence of an increased number of 

 pistils and carpellary leaves. Thus in plants (as in animals) any disturb- 

 ance in the structural if not in the functional characters of the primary 

 sex organs is usually associated with changes in the secondary flur.il 

 characters. 



Primarily Male and Primarily Female Flowers. 



The question now arises whether the arrangement and distribution 

 of the male and female sex organs in these hermaphrodite Begonia 

 flowers throw any light upon the central position of the Ciyno(>cinm in 

 our modern hermaphrodite flowering plants. 



