LETTERS TO CARL NAGELI, 1866-1873 

 The packets enumerated above contain round and yellow, round and green, 

 angular and yellow, and angular and green seeds from the hybrids ab-\-AB. 

 The round and yellow seeds would be best suited for the experiment. Among 

 them (see experiment p. 15) the varieties AB, ABb, Aab, and AaBb may occur; 

 thus four cases are possible when plants, grown from green and angular seeds, 

 are fertilized by the pollen of those grown from the above mentioned round 

 and yellow seeds, i.e. 



I. ab+AB 



II. ab-\-ABb 



III. ab-{-AaB 



IV. ab+AaBb 



If the hypothesis that hybrids form as many types of pollen cells as there are 

 possible constant combination types is correct, plants of the makeup 



AB produce pollen of the type AB 



ABb " " " " " AB and Ab 



AaB " " " " " AB and aB 



AaBb " " " " " AB, Ab, aB, and ab 



Fertilization of ovules occurs: 



I. Ovules ab with pollen AB 

 II. " ab " " AB and Ab 



III. " ab " " AB and aB 



IV. " ab " " AB, Ab, aB, and ab 



The following varieties may be obtained from this fertilization: 



I. AaBb 

 11. AaBb and Aab 



III. AaBb and aBb 



IV. AaBb, Aab, aBb, and ab 



If the different types of pollen are j^roduced in equal numbers, there should be 

 in 



I. All seeds round and yellow 

 II. one half round and yellow 

 one half round and green 



III. one half round and yellow 

 one half angular and yellow 



IV. one quarter round and yellow 

 one quarter round and green 

 one quarter angular and yellow 

 one quarter angular and green 



Furthermore, since the numerical relations between AB, ABb, AaB, AaBb are 

 1:2:2:4, among any nine plants grown from round yellow seed there should be 

 found on the average AaBb four times, ABb and AaB twice each, and AB 



s-9 



