ON THE PRIMARY AND SECONDARY SEX CHAR- 

 ACTERS OF SOME ABNORMAL BEGONIA 

 FLOWERS AND ON THE EVOLUTION OF 

 THE MONOECIOUS CONDITION IN PLANTS. 



By C. J. BOND. 



PART I. 



My attention was first directed to the problem of Sex Dimorphism 

 in the Begonias when noticing that certain flowers in which the process 

 of Sex Differentiation was incomplete were almost invariabl}^ accom- 

 panied by an abnormal or supernnraerary Floral Bract. This accessoiy 

 and asymmetrical Floral Bract occurs on the pedicle which bears the 

 abnormal flower. It seems to mark the situation in the growth of the 

 flower stalk where under normal conditions the Male and Female Sex 

 Organs are segregated out into flowers of opposite sex. (PI. XVI, fig. 1.) 



The importance of this abnormal floral bract lies in the indication it 

 affords of the fact that the differentiation of the Sex Character is a 

 matter of qualitative cell division in somatic as well as in germinal 

 cells. 



The next point is that partial or complete failure to undergo quali- 

 tative cell division in these abnormal flowers is associated with abnor- 

 mality of another kind. This secondary abnormality may take the form 

 of modification in, or increased number of accessory floral parts, or 

 elongation of the staminal axis with increased number of stamens, or 

 petallody of stamens (doubleness in the male flower). In the female 

 flower it may take the form of an increased number of carpellary leaves, 

 as indicated by an abnormal number of ovarian loculii, or (by failure of 

 these carpellary leaves to close) an exposed condition of the ovules, a 

 partial return in fact to the Gymnospermous condition. 



Any of these changes may afford the earliest indication in male and 

 female flowers respectively of a distuibance of sex equilibrium, in other 



