FERTILITY 



201 



case of primula, which is dimorphic, he found not only 

 that self-fertilization gave less vigorous plants, but 

 that when pollen from a long-styled flower of one plant 

 fertilizes the pistil of another long-styled plant the 

 vigor of the offspring is less than when the same kind 

 of pollen is used to fertilize the pistil of a short-styled 

 flower. The next table gives the detailed results. 



We know now that these two types of plants — long- 

 styled and short-styled - - differ from each other by 

 a single Mendelian factor. We may therefore state 



