NOTE ON GAMETIC liEDU PLICATION IN PISUM. 



By CAROLINE PELLEW, 



Minor Student of the John Innes Horticultural Institution. 



It was shown by Vilmorin and Bateson^ that when a normal 

 culinary pea having tendrils {T) and round seed {R) is crossed with 

 the " Acacia " variet}^ in which the tendrils are represented by leaflets 

 {t) and the seed is wrinkled (?^), partial coupling between T and R 

 occurs in the gametes of F^. The numbers suggested that the system 

 of coupling was 63 : 1. Further investigation of a number of plants of 

 similar composition derived (in various generations) from this cross 

 fully conj&rm the earlier results. From round seeds the numbers 

 obtained were 1466 tendrilled, 20 acacia, on the expectation 63 : 1 

 system being 14-71 : 15. 



From wrinkled seeds the numbers were 15 tendrilled and 564 

 acacia, the similar expectation being 18 : 561. 



Only seeds of which the starch had been microscopically determined- 

 were used for these results. This precaution is necessary because not 

 very rarely occasional seeds of each class may on external appearances 

 be referred to the wrong class. It should be mentioned that the round 

 and ^vrinkled seeds, thus determined, though all the offspring of plants 

 heterozygous for these characters, were selected independently of each 

 other. 



In these experiments the crosses were in the form TR x tr, and the 

 coupling was 



Q^TR :lTr :ltR: 6Str. 



Subsequently crosses were made in the form Tr x tR, a tendrilled 



1 Proc. Roy. Soc. 1911, 84 B, p. 9. 



2 By the method introduced by Gregory, R. P., New Phyt. n. 1903, p. 226. 



