308 Douhleness in Stocks 



Sulphur-white Race. 



62 individuals were self-fertilised, but in this case they were not all 

 descended in one line. Their relationship is shown below. 



1 Parent plant {A)^ 



7 Fi Plants derived by self-fertilisation from the parent plant A 



19 F„ „ „ ,, >, 3 of the Fi indiWduals 

 3 Fi „ „ „ „ 1 „ Pi 



1 Parent plant (B)' 



20 Fi Plants derived by self-fertilisation from the parent plant B 



5 Fo „ ,, ,, ,, 2 of the Fi individuals 



5 F3 „ „ „ „ 3 „ F-i 



1 Parent plant (C) 



Total 62 



Families were obtained from each of these 62 individuals and here 

 again doubles occurred in every case (see Table III). It is therefore 

 evident that this race also is wholly composed of eversporting individuals. 

 So much seems clear from the results of self-fertilisation, but it is only 

 on crossing that the real explanation of these results becomes apparent. 



Reciprocal crosses between rf-strains and ?!0-rf- strains afford a con- 

 venient means of separately testing the ovules and the pollen of the 

 (Z-strain, and it is through the different behaviour of such reciprocals 

 that we are enabled to understand the true cause of the eversporting 

 habit. At this point it will be convenient to consider transmission of 

 the double character by the pollen in these two strains'*. 



When the red or sulphur-white was used as the pollen parent in 

 a cross with a pure-breeding {no-d) strain all self-fertilised i^, plants, 

 with three exceptions, produced a mixture of singles and doubles in 

 Fo (see Table IV). In view of all the evidence it is unlikely that any 

 of these three cases really indicates a genuine exception ; each will be 

 fully discussed later (see pp. 309, 310). 



The experiments with the red race were as follows : — 



Pollen from 6 individuals of this race was used to fertilise 10 plants 

 belonging to 4 different pure-breeding strains. The number of seed- 

 parents in each case was as follows: 



iSTo-rf-glabrous cream 4 



,, „ white 4 



„ ,, flesh 1 



„ hoary white (Brompton) 1 



Total ... 10 



' A and B were obtained from different growers. 



- Transmission by the ovules will be dealt with in a later section (see p. 323). 



