On Gametic Coupling and Repulsion in Primula sinensis. 13 



Magenta, 

 single. 



Magenta, 



Eed, 

 single. 



Ked, 



Total. 



27 9 



9 2 



47 





Short style, 

 single. 



Short style, 

 double. 



Long style, 

 single. 



Long style, 

 double. 



Total. 



24 



10 



12 



1 



47 



The second long-styled race used was a dark red with red stigmas. In the 

 families obtained from the crosses of this race with the short-styled race, the 

 distribution of the offspring in the four classes is much less simple than in 

 the preceding case ; there is an excess of magentas and of short-styled 

 plants, and the form which the partial coupling takes is not certain. The 

 only family raised from the Fi self-fertilised, containing as it did a large 

 number of plants with colourless flowers, was too small to give any indication 

 of the form of the coupling. The reciprocal crosses between the F! and the 

 recessive parent race give results which are almost exactly intermediate between 

 the expectation based on the series 7:1:1:7 and that based on the series 

 15 : 1 : 1 : 15. It is further to be noticed that in these families there is clear 

 evidence that the factor for magenta is partially coupled, not only with the 

 factor for short style, but also with a third factor, which has the effect 

 of suppressing the development of pigment in the stigma, giving rise to the 

 dominant green stigma. The partial coupling which is shown in this case is 

 of a much lower type than that which obtains between magenta and short 

 style, and, as in previous experiments,* does not exactly conform to any known 

 series. 



The fact that the magenta factor takes part in two systems of coupling, 

 one of which is of an undetermined form, renders the results complex. 

 Further data are required for their complete analysis, particularly in regard 

 to the effect which the two systems of coupling, in combination, may have 

 upon the distribution of the factors for short style and green stigma among 

 the offspring. When the offspring are classified according to these two 

 characters, the numbers observed are irregular, there being an excess of 

 plants bearing the dominant characters. 



* ' Journ. Genetics,' 1911, vol. 1, No. 2. 



