Heredity 189 



obtained in the FI generation, 65 mottled. In F 2 genera- 

 tion there were 113 mottled, 52 self-colored, and 70 

 white, that is, in the ratio of 6.45 : 2.97 : 4 instead of 

 9:3:4. 



In the F z generation he secured the following results : 



1. All white seeds produced white seeds. 



2. 7 mottled gave 22 mottled, 19 self-colored, 11 white. 



3. 2 mottled yielded 13 mottled, 13 self-colored. 



4. 4 mottled bore 5 mottled, 5 white. 



5. 2 mottled produced 6 mottled. 



6. 5 self-colored gave 63 self-colored. 



7. 9 self-colored yielded 80 self-colored, 29 whites. 

 For the purpose of explaining the above, Emerson adopted 

 the formula of Shull. 



1. P and p for the factor presence and absence of pig- 

 ment. 



2. M and ra for the factor presence and absence of 

 mottling. 



3. Pm = self-colored. 



4. pM = white. 



5. PM = mottled. 



Thus he considers a self-colored variety containing the 

 factor for pigment and having no factor for mottling. 

 The white variety lacks the factor for pigment, but has 

 the factor for mottling. The mottled form is originated 

 by the presence of two factors, for the pigment and 

 mottling. 



If we follow these formulae, we must confer to the F\ 

 generation the following gametic composition, PpMm, 

 since FI hybrids will produce 9 mottled, 3 self-colored, 

 and 4 white for the F 2 generation as seen on page 190 : 



