XI COUPLING AND REPULSION 129 



obtained durin^^ the past few years, and we now 

 know that the relation between E and L is similar 

 to that existing between B and L. When a cross 

 is made between a plant with erect standard and 

 long pollen, and one with hooded standard and 

 round pollen, the colour being the same in both 

 cases, the F^ plants are all long pollened and erect. 

 In F^, as the appended scheme shows, the four 

 expected classes are produced in proportions which 

 tally closely with the hypothesis that the gametic 

 series produced by the F^ plants is of the nature 

 7 EL \ I El \ I eL \ y el. 



Of the three factors B^ £", and Z, any given pair 

 exhibits the phenomenon of coupling and repulsion, 

 where the plants are homozygous in respect of 

 the third factor. What happens in the case of 

 plants which are heterozygous for all three factors ? 

 There are four different ways in which such plants 

 can be made, viz. : 



BeL X bEl 

 BEl X beL 

 bEL X Bel 

 BEL X bcl 



According to the manner in which they are 



K 



