Some Laws of Heredity 37 



tion, so that Mendel conceived it must be 

 present though hidden. 



■D-R 



I 

 Fi Generation D(R) 



F4 D D I D 2 D(R) I R R . R 



But now what happened when plants were 

 crossed differing in two characters? Mendel 

 found, as before, that in the Fj generation only 

 the dominant characters were apparent, but 

 that in the next generation the recessive char- 

 acters reappeared. Thus pea plants bearing 

 smooth yellow peas were crossed with those 

 having wrinkled green seeds, and aU the peas 

 produced were smooth and yellow. When, 

 now, these were planted and the flowers on 

 the vines were allowed to poUinate freely in 

 the natural way, there resulted peas of four 

 sorts and always in a definite ratio, namely, 



