MEXDFX'S LAW OF HEREDITY AND HORTICULTURE. 



23 



done, that each heritable character is represented in the germ-cells (both 

 egg-cells and pollen-cells) by a certain determiner or factor. In the 

 particular case we have been considering, the heritable characters are 

 apparently tallness and dwarfness. Each individual plant raised from 

 fertilized seed is the product of its two parents, consequently it is a 

 double structure determined by the coming together of the paternal and 

 maternal factors. 



A pure-bred tall pea, for instance, may be said to be the outcome 

 of the meeting of a paternal factor for tallness with a maternal factor 

 for tallness. Similarly, a pure-bred dwarf pea may be regarded as the 



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Fig. 12. 



-Showing the results obtained by Mendel in crossing Tall 

 AND Dwarf Peas. 



consequence of the meeting of a paternal factor for dwarfness with a 

 maternal factor for dwarfness. On the other hand, a cross-bred 

 between a pure-bred tall pea and a pure-bred dwarf pea may be regarded 

 as due to the meeting of the paternal factor for tallness with the 

 mxaternal factor for dwarfness, or vice versa. Mendel's conception 

 was that when the cross-bred formed its germ-cells (egg-cells and 

 pollen-cells), the factors for tallness and dwarfness separated, the tall 

 factor going into one germ-cell and the dwarf factor into another. In 

 that case the germ- cells of the cross-bred would be of two kmds, and 

 on the average one-half of them would be carrying the tall factor and 



