THEORY OF PANGENEIC INTERCHANGE 239 



in H, and similarly egg cells Bj and Ji, would be formed from 

 corresponding megaspores. When it came to pollination it 

 would happen in the long run that pollen grains i and 2 would 

 become so distributed by insects or wind, etc., that sperm cell A, 

 would chance to fertilize egg cell Bj resulting in fertilized egg 

 cell Cj", and sperm cell A^ would fertilize egg cell B^, resulting 

 in fertilized egg cell C2. These fertilized egg cells would grow 

 into embryos which finally would become mature plants D j and 

 D,. It will now be noticed that D^ and D2 are unlike the hybrid 

 from which they sprang and unlike either of the parents of the 

 hybrid; and, furthermore, it can be seen from the constitution 

 of the fertilized egg cells C^ and C^ that the offspring of D, and D2 

 produced by self-fertilization are bound to come true to the 

 parental characters, because D^ has nothing but lateral, blue 

 flowers, hairy stems and long leaflets in its blood, and likewise D2 

 has nothing but terminal, yellow flowers, smooth stems and 

 short leaflets. Such organisms are said to be homozygote. 



Given a sufficient number of instances, all possible varieties 

 of interchange of pangenes would take place in E. Let us there- 

 fore now suppose that the interchange of leaflet characters shown 

 in J occurs in the formation of microspores, resulting in sperm 

 cells A3 and A^, and that these by chance came to fertilize the 

 same variety of egg cells shown in Bj and B2, now represented 

 by B3 and B^. Fertilized egg cells C3 and C^, and mature 

 plants D3 and D^ would result. It will be seen in fertilized egg 

 cell C3 that yellow and blue color of flowers, and short and long 

 leaflets are in the blood of D3; but, as will be seen in the original 

 hybrid, the yellow flower and short leaflet characters are domi- 

 nant. Likewise D^ has yellow and blue flowers, and long and 

 short leaflets in its blood. Such organisms as these are called 

 heterozygote. 



Now some interesting comparisons can be made. D, and D^ 

 will come true to seed when self-fertilized, while D3 and D^ 

 will not do this. Under self-fertilization the offspring of D3 will 

 all have hairy stems and lateral flowers, because they are homo- 

 zygote to these characters, but they will show the following 



