34G Sex Characters in Begoniaa 



an accessoiy chromosome into one of two alternative gt'iiii cells deter- 

 mines the sex of the individual. At present we are ignorant as to the 

 stage in the growth of the floral parts at which this segregating division 

 occurs. Neither do we know the difference in nuclear or factorial con- 

 .stitution between the primarily male and the primarily female flower oi- 

 whether this difference is of a genetic or a somatic character. 



Primanly Male and Primarily Female In florescences. 



This concef)tion of a flower as primarily male oi- primarily female 

 may also be extended to the Inflorescence. 



In the normal inflorescence of the tuberous Begonia the flower 

 which terminates the floral peduncle is a male flower. A few abnormal 

 examples occur in which on cui-sory examination it appears that a 

 female flower terminates the inflorescence, but careful inspection will 

 show that even in these cases a rudimentary or abortive male terminal 

 flower really exists. If in some varieties with double male flowei-s the 

 inflorescence is apparently entirely composed of one male flower, careful 

 examination will reveal however rudimentary or abortive female flowers 

 in the axils of the bracts of the floral peduncle which carries this flower. 

 Further, in some varieties both in the tuberous and fibrous kinds 

 (e.g. Mrs J. Heal, Beg. Socotrana, Gloire de Lorraine, and others) only 

 male flowers are present. In these cases the inflorescence is not 

 symmetrical and tripartite, but asymmetrical with male flowers given 

 oflf on one side only. In some climbing Begonias the male flowers 

 nonnally appear at the fourth or fifth dichotomous division of the floral 

 peduncle while female flowers appear later at the sixth or seventh 

 division; further, as the male flowers fall early the result is that the 

 inflorescence appears to be composed of female flowers only. The point 

 of physiological and cytological interest about the inflorescence thus 

 becomes (as in the flower) a problem of the relative position of certain 

 organs. In other words the disposition of sex organs in flowers of 

 opposite sex like the disposition of sex organs on a ccmimon floral 

 axis in the hermaj^hrodite flower is a problem of qualitative cell division. 

 In the inflorescence, as in the flower, we find two types : — 



(a.) A male type in which the terminal flower is a male flower and 

 the female flowers are thrown oft' laterally, as in the Begonia. 



(6) A female type in which the terminal flower is a female flower 

 and the male or hermaphrodite flowers are thrown off laterally, as in 

 some caryophyjlaceous plants. 



