190 



Plant-Breeding 



PM 



POLLEN-GRAINS 

 Pm pM 



pm 



PM 



Pm 



pm 



The ratio of 6.45 : 2.97, instead of 9 : 3 : 4, seems to be 

 chiefly due to the paucity of number treated for hybridi- 

 zation. Doubtless it is no small importance to study 

 the ratio of offspring in F s in the light of the theoretical 

 deduction. But here again the insufficient number of 

 seeds informs us of its inadvisibility. 



In conclusion Emerson says: "The result of most of 

 my own experiments might be explained as due to the 

 mendelian behavior of an allelomorphic pair, Mm presence 

 and absence of mottling, M being visible only in the pres- 

 ence of P." 



Colored forms from white X white and the 9 : 7 ratio. 

 In the case of the sweet peas, Bateson has shown that the 

 formation of color in the flowers can be proved to depend 

 on the coexistence of two complementary factors in the 

 individual. 



He says that the first indication of this phenomenon 



