EXPERIMENTS IN THE HEREDITY OF PEAS. 



491 



In the first generation, therefore, the dominance of yellow cotyledons 

 over i^reen was absolute and exclusive, there being no trace of green either 

 without or within the cotyledons. As shortly to be seen, the green colour, 

 though not patent in the first generation, was nevertheless latent, re- 

 appearing in full strength in the second generation, exactly as Mendel 

 demonstrated (Mendel 1865, Bateson 1901). 



Second Generation (F 2 ). 

 DR x DR. 



Fourteen of the dominant yellow hybrids raised in Experiment 1 were 

 sown, and, as previously described, produced 12 hybrid plants which, self- 

 fertilised, gave 1,755 seeds in the second generation. The cotyledons of 

 these seeds were of two distinct colours, yellow and green, both colours 

 being often produced in the same pod ; some pods contained all yellow, 

 but none contained all green. The following is a list of the numbers of 

 each colour produced by the individual plants : 





D 



R 



Expt. 

 2 



Yellow. 



Green. 



23 



10 



3 



27 



9 



4 



26 



9 



5 



374 



129 



6 



11 



9 



7 



134 



37 



8 



57 



17 



9 



205 



50 



10 



284 



110 



11 



84 



31 



12 



71 



26 



13 



14 



8 



Total 



1,310 



445 



Actual ratio 



2-9 D 



: 1 R 



Mendelian ratio 



3 D 



1 R 



Out of the 1,755 seeds of the second generation, 1,310 were yellow 

 dominants and 445 green recessives, giving a ratio of 2*9 D : 1 R, which 

 is close to the 3 : 1 expected by Mendel's law. With regard to the precise 

 nature of the dominant and recessive categories in the above experiments, 

 the character of cotyledon colour is apparently much more simple than 

 that of seed shape, possibly being less influenced by the conditions of life. 



One hundred full- sized healthy seeds of the yellow round Peas were 

 taken at random from Experiments 2, 3, 4, 6, 7, 8, 11, 12, and 13 (those 

 of Experiments 5, 9, and 10 being required for sowing), and when 

 peeled they were all quite indistinguishable in colour from the yellow 

 round hybrid Peas of the first generation, both without and within the 

 cotyledons. Similarly, 50 yellow wrinkled Peas from the same experi- 

 ments were indistinguishable both in colour and in shape from the pure 

 yellow wrinkled Peas of the ' British Queen ' grand-parent. The wrinkled 



N" 2 



