R. P. Gregory 



127 



partly a result of this, and the numbers obtained suggest that a coupling 

 of a fairly high order was present. 



(2) Coupling between colour characters. 



With the exception of the mating between " Crimson King " and 

 "Snowdrift," all the experiments in crossing either "Crimson King" or 

 " Orange King " (red, red stigma) with plants carrying the factors for 

 magenta colour and green stigma, have given results which point clearly 

 to the existence of a partial coupling between these factors in gameto- 

 genesis. The results in general show some deficiency of the two 

 dominant characters, magenta and green stigma, as compared with 

 the expected ratio, in each case, of 3 D : 1 R ; the classes consisting 

 of plants having one or both recessive characters are therefore unduly 

 large, and it is necessary to make allowance for this in attempting to 

 compare the observed numbers with the expectation calculated upon 

 various systems of partial coupling. The distribution of the four 

 characters in the offspring possessing fully-coloured flowers and red 

 stems is set out below : 



Constitution of -Fo 



' Orange King ' 



Cross 

 X "Snowdrift" 



" Crimson King " x Rosy Magenta 



"Crimson King"x "Queen Alexandra' 



"Crimson King "x " Ivy-leaf ' 



In these results, that obtained in No. 18/9 stands alone in that the 

 fourth term of the series is distinctly larger than either of the middle 



