66 BREEDING 



to be dominant over the green in every case. The 

 second hybrid generation was distributed over 258 

 plants, and consisted of 6,022 yellows and 2,001 

 greens ; a very close approximation to the three -to- 

 one ratio. Mendel gives the distribution of yellow 

 and green seeds on ten plants in his paper ; it was 

 as follows : — 



Of the total number of individuals (i.e. seeds) which 

 composed the second hybrid generation (namely, 

 6022 + 2001 = 8023) only 519 yellow- cotyledoned 

 ones were tested : 166 produced yellows only, i.e. 

 were pure dominant yellows ; 353 produced yellows 

 and greens in the ratio of three to one, i.e. were 

 hybrid yellows. In other words, 519 of 8023 seeds 

 (which contained the second hybrid generation) were 

 sown, 166 gave rise to plants which produced yellow 

 seeds only, 353 gave rise to plants which produced 

 yellow seeds and green seeds in the ratio of three to one. 



We will now proceed to a consideration of the 

 mode of inheritance of the shape of the cotyledons 

 in Pisum. The pair of characters in this case is 

 round (which is dominant) and wrinkled (which is 



