329 
Though the evidence for partial repulsion rests here upon 
the Single red^ round^ plant which occured in family 61, it is in 
reality much stronger tlian it appears, for the following reason. 
All the plants in the above four families were h o o d e d, i. e., 
lacking in the factor for erect Standard (E), As we have already 
pointed out^) the three factors E. B. and L constitute a series 
such that if any two are brought in to a zygote by different 
gametes repulsion occurs between them. Until the present round 
hooded red plant appeared we had never encountered this 
Kombination in any of our experiments. It cannot therefore be 
regarded as due to a stray seed from another family. And it is 
evident that if the repulsion between any pair of these three 
factors were complete, such a plant could never arise ; for in the 
normal course the ebl gamete could never be formed. Only two 
possibilities therefore are opeu. Either we must look upon this 
plant as an unaccountable mutation, or we must consider that 
the repulsion betweeo B and L is partial. In the light of the 
evidence affreded by the Cretin Sweet Pea we prefer the latter 
hypothesis, and we are inclined to regard the partial repulsion 
between B and L, as of the 1:7:7:1 type. On this hypothesis 
we should expect one red round m every 256 plants (cf. Table II) 
whereas experiment gave 1 in 419. At the same time we 
recognize that the data are not yet sufficient to preclude the 
1 : 15 : 15 : 1 System. It is worthy of note that the coupling 
between B and L is usually on the 7 : 1 : 1 : 7 System, and it 
would be iuteresting if in such cases as these the repulsion and 
coupling System for a given pair of factors should prove to be 
of the same intensity: In most cases this could not be tested 
in practice owing to the very large number of plants required. 
Thus the coupling between erect Standard and blue is on the 
127 : 1 : 1 : 127 System, and if the repulsion were of similar 
intensity we should expect only one hooded red in every 65, 536 
plants. We may however State that in this particular case we 
have grown over 4000 plants without meetmg with a hooded 
red, so that the facts, as for as they go, point to a high inten- 
sity of repulsion for factors exhibiting a high intensity of coupling-. 
It is obvious that the relation can only be worked out where 
the intensity of repulsion is h^w and it may be hoped tliat the 
1^1 Proc. Roy. Soo. 1 11. »j. 7. Ser. B. v(^l. 84. 
