102 BREEDING 



3. Green round — 



(i) Pure to colour and shape . . 1 

 (ii) Pure to colour but not to shape . 2 



3 



4. Green wrinkled — 



Pure to colour and shape , . 1 



It will be observed that there is only one pure 

 breeding representative of each of the four categories 

 yellow round, yellow wrinkled, green round, and 

 green wrinkled. 



The ratios in the above may be arrived at by 

 multiplying together the ratios in which the parti- 

 cular characters which make up each combination 

 occur separately, having regard to the question 

 whether the character is in a pure or hybrid state. 

 Thus, when a yellow is crossed with a green the 

 second hybrid generation is composed as follows : 

 1 pure yellow, 2 hybrid yellow, 1 green, in every 

 four ; and the second hybrid generation from a cross 

 between a round and a wrinkled has the following 

 composition : 1 pure round, 2 hybrid round, 1 

 wrinkled, in every four, on the average. The com- 

 bination of these six classes will, therefore, occur in 

 the following ratios : — 



[1. Yellow round] — 



Pure yellow and pure round . 1x1 = 1 



Pure yellow and hybrid round . 1x2 = 2 



Hybrid yellow and pure round 2x1 = 2 



Hybrid yellow and hybrid round 2x2 = 4 



—9 



