Plants in Relation to Man 



507 



pea bearing purple blossoms is hybridized with one bearing 

 white blossoms. It does not matter which plant is selected 

 for the pollen, and which for the ovule parent. The plants 

 produced from the cross-fertilized seed inherit the characters 

 of both parents. They are therefore called hybrids. All the 

 plants of this generation bear purple blossoms. The plants of 

 the succeeding generations will repeat both of the original char- 

 acters in a definite mathematical ratio. This ratio will con- 

 tinue through all succeeding generations. It is just because of 



Tall 



Dwarf 



Pure 



SecondHybrid 

 Generation 



ThirdHybrid 

 Generation 



FIG. 158. Diagrammatic representation of the principle of Mendelian 

 inheritance. 



this reappearance of unit characters in the third and succeed- 

 ing generations that desirable characters may be selected and 

 by cross-fertilization be made a permanent variety. In the 

 same way a new variety or an old pure character may be ob- 

 tained from hybrids. 



Dominant and recessive. One of Mendel's experiments in 

 crossing different varieties of peas may be taken to illustrate 

 the important facts and suggest the principle derived from these 



