158 Plant-Breeding 



twenty-five flowers on round-seeded plants were cross- 

 pollinated in the summer of 1900 with pollen from angular - 

 seeded plants, or vice versa, and that an average of four 

 seeds formed in each pod. With the death of the parent 

 plants the old generation ended, and the 100 seeds that 

 matured in 1900 the year in which the cross was made 

 began the next generation; and these 100 seeds were 

 hybrids. Now, all of these 100 seeds were round. Round- 

 ness in this case was "dominant." (Dominance per- 

 taining to the vegetative stage of the plant of course would 

 not appear until 1901, when the seeds "grow."") These 

 seeds are sown in the spring of 1901. If each seed be 

 supposed to give rise to four seeds, or 400 in all, this 

 next generation of seeds (produced in 1901) will show 

 300 round and 100 angular seeds. That is, the other seed- 

 shape now appears in one-fourth of all the progeny; this 

 character is said to have been "recessive" in the first 

 hybrid generation. If the 100 angular seeds, or reces- 

 sives, are sown in 1902, it will be found that all the progeny 

 will be angular-seeded or will "come true"; and this 

 occurs in all succeeding generations, providing no crossing 

 takes place. If the 300 round seeds, or dominants, are 

 sown in the spring of 1902, it will be found that 100 of them 

 produce dominants only, and that 200 of them behave as 

 before one-fourth giving rise to recessives and three- 

 fourths to dominants; and this occurs in all succeeding 

 generations, providing no crossing takes place. In other 

 words, the three-fourths of dominants in any generation 

 are of two kinds, one-third that produce only dominants, 

 and two-thirds that are hybrids. That is, there is con- 

 stantly appearing from the hybrids one-fourth that are 



