MENDELISM 19 



Fij which will show all these results is 16, as illustrated in 

 this diagram — 



I 



x D 

 i 



i 



iisi nil iiib nan 



o 



Here you observe 12 dark stripes representing the 

 plants with coloured flowers, and 4 light stripes to represent 

 the white ones. 12 to 4 is the 3 to 1 ratio. There are 

 also 3 tails to every dwarf. So that we get 



9 tall coloured, 

 3 dwarf coloured, 

 3 tall white, 

 1 dwarf white. 



This ratio of 9-3 -yi (9 with both dominant characters, 

 3 with only one such, 3 with the other, and 1 with both 

 recessive characters) is true of any two pairs of contrasted 

 characters. 



I submit that a theory which will explain such a 

 complicated result is most satisfactory. Mendelism — and 

 so far Mendelism alone — has furnished the explanation. 



I will now give you a problem to work out for yourselves. 

 What will be the result of crossing wrinkled yellow seeds 

 with smooth green if yellow is the dominant colour and 

 smoothness the dominant surface ? — 



WY x SG 



The Fj generation will be — what ? — 



SY ( = smooth yellow) 



Suppose a gardener ignorant of Mendelian laws wished 

 c 2 



