328 Plant Life and Evolution 



The plants resulting from the round seeds of the 

 second generation, however, are not all alike, but 

 some will produce round seeds while others show 

 the wrinkled seeds, and the proportion in which 

 these are produced will be three plants with round 

 seeds to one plant with the wrinkled seeds. The 

 offspring of the latter, or recessive type, will breed 

 true, but of the three-quarters with the round seeds 

 only one-quarter are pure dominants, breeding true, 

 while the offspring of the other half are hybrids, 

 dividing in the next generation in the same ratio, 

 three dominants to one recessive, and so on. This 

 behavior implies that the sex cells are either pure 

 dominants or pure recessives, and when fusing in 

 crossing will produce either pure dominants, re- 

 cessives, or hybrids between the two, the proportion 

 following closely the law of probability. 



Professor Bailey explains the law as follows: 

 " Differentiating characters in plants reappear in 

 their purity and in mathematical regularity in the 

 second and succeeding hybrid offspring of these 

 plants; the mathematical law is that each character 

 separates in each of these generations in one-quarter 

 of the progeny and thereafter remains true. In 

 concise figures it is expressed as follows : iD : 2DR : 

 iD. iD and iR continuing true, but DR breaks 

 up again into the dominants and recessives in the 

 ratio of three to one." 



The Mendelian law has been applied to a good 

 many cases of inheritance in both plants and ani- 



