12 



On Gametic Coupling and Repulsion in Primula sinensis. 

 By E. P. Gregory, M.A., Fellow of St. John's College, Cambridge, 

 University Lecturer in Botany. 



(Communicated by W. Bateson, F.R.S. Received March 2,— Bead 

 March 30, 1911.) 



In Primula sinensis the short style is dominant to the long style, and the 

 magenta colour of the flower is dominant to the red colour. 



Some years ago a series of experiments was made, in which a red short- 

 styled race was mated with various long-styled plants carrying the factor for 

 magenta colour. In F 2 from these crosses, only three kinds of offspring 

 were obtained, namely : (1) magenta, short-styled ; (2) magenta, long-styled ; 

 (3) red, short-styled. No red long-styled offspring were produced.* This 

 result shows that, in the gametogenesis of the Fx, complete repulsion took 

 place between the factors for the two dominant characters, magenta and 

 short style. 



In another series of crosses which have been made recently, a short-styled 

 race carrying the magenta factor was crossed with two races of long-styled 

 reds. The results obtained in F 2 show that, when the cross is made in this 

 way, a partial coupling occurs between the factors for the two dominant 

 characters. 



One of the long-styled races used in these experiments was a red, with 

 double flowers and green stigmas. In the two F 2 -families raised from 

 the crosses of this race with the short-styled race, the partial coupling 

 observed is almost entirely certainly of the form 7:1:1:7. 



The numbers obtained are : — 





Magenta, 

 short style. 



Magenta, 

 long style. 



Red, 

 short style, 



Red, 

 long style. 



Total. 





33 



32-5 



3 



2-8 



1 



2-8 



10 

 9-0 



47 



47-1 



Expectation? : 1 : 1 : 7 ... 



In these two families there is no indication tbat either of the characters 

 under consideration has any special inter-relation with any other character, 

 the distribution of singles and doubles in the four types of offspring giving 

 the normal ratio 9:3:3:1. The numbers obtained are : — 



* The experiments are described in detail in the 'Journ. Genetics,' 1911, vol. 1, 

 No. 2. 



