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TEXTBOOK OF ZOOLOGY 



The seeds that resulted from the cross were collected and planted. 

 To the amazement of the investigator they produced nothing but tall 

 peas; peas as tall as the original tall parents. Dwarf ness seemed to 

 be lost and tallness was certainly dominant. A less thorough investi- 

 gator might have called his experiment finished and have proclaimed 

 as a rule, the fact that a trait can disappear when it is crossed with 

 its opposite. But not so with the patient monk. He pollinated these 

 plants with their own pollen and planted another generation. This 



Fig. 426. — Diagrram to show the result of crossing tall and dwarf peas. The 1:2:1 



ratio appears in the F2 generation. 



time three-fourths of the plants were tall and one-fourth of them 

 were as short as the original dwarf parents. Not being ready even 

 yet to formulate a law, he self -pollinated his plants for several more 

 generations and got results that required his best mathematical skill 

 to interpret. The dwarf peas produced only dwarf peas. Of the tall 

 peas, one-third of them (constituting one-fourth of the whole num- 

 ber) produced tall peas without deviation, but the other two-thirds 

 (half of the whole number) produced stock that repeated the produc- 



