THEORY OF PANGENEIC INTERCHANGE 239 



in H, and similarly egg cells B t and B 2 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 t 

 would chance to fertilize egg cell B t resulting in fertilized egg 

 cell C x ; and sperm cell A 2 would fertilize egg cell B 2 , resulting 

 in fertilized egg cell C 2 . These fertilized egg cells would grow 

 into embryos which finally would become mature plants D t and 

 D 2 . It will now be noticed that D t and D 2 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 t and C 2 that the offspring of D t and D 2 

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

 parental characters, because ~D l has nothing but lateral, blue 

 flowers, hairy stems and long leaflets in its blood, and likewise D 2 

 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 A 3 and A 4 , and that these by chance came to fertilize the 

 same variety of egg cells shown in B t and B 2 , now represented 

 by B 3 and B 4 . Fertilized egg cells C 3 and C 4 , and mature 

 plants D 3 and D 4 would result. It will be seen in fertilized egg 

 cell C 3 that yellow and blue color of flowers, and short and long 

 leaflets are in the blood of D 3 ; but, as will be seen in the original 

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

 nant. Likewise D 4 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 l and D 2 

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



7 o 4 



will not do this. Under self-fertilization the offspring of D 3 will 

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

 zygote to these characters, but they will show the following 



