DOUBLE FLOWERS AND SEX-LINKAOE 

 IN BEGONIA. 



By W. BATKSON, M.A., F.R.S., and IDA SUrrOX, 

 Student in the John Innes Horticultural Instxtution. 



(With Plate VIll.) 



Begonias are monoecious plants, having thrir flowers armngcd in 

 axillary cymes. In normal plants the flower which terminates each 

 dichasium is a male ; and, in the simplest arrangement, njwn either side 

 of this stands a female. For one or both of these females may b<' 

 substituted a continuation of the inflorescence, which again at each 

 dichasium ends in a male, this system being indefinitely repe^ited. 



Since doubleness affects only those flowers which stiind terminally, 

 being that is to siiy in normal plants males, an investigation of the 

 inheritance of this condition offered attractions, as being not unlikely 

 to throw light on the genetics of sex. In passing it may be remarked 

 that since a female flower can be replaced by an inflorescence, wherejus 

 a male flower is not thus replaceable, from these morphological relation- 

 ships we are led to infer that the female flower contains something that 

 the male hjis lost. The male flower may be thus compared to a reces- 

 sive, dropped out of the inflorescence which can be produced further in 

 the heterozygous state. 



The investigation wjis begun in 1908 by fertilising the normal female 

 flowers of double Begonias with pollen from singles of unknown origin. 

 Subsequently further crosses were made between doubles and a horti- 

 cultural strain of singles which was declared to have bred true for some 

 generations. The results have been full of complications such that, 

 after many years work, it has become evident that no simple factorial 

 scheme is f<jllowed, and that segregation in regard to single and double 

 flowers must in these plants be a process liable to considerabhj irregu- 

 larity. In general the single is a dominant as Bond also found. T\\v 

 recessive doubleness reappears in F^y but the numerical proportion of 

 F^ doubles is low and fluctuates widely. There are many transitional 

 forms, which render accurate classification and enumeration impossible, 



