326 PLANT HYBRIDIZATION BEFORE MENDEL 



"We then have, summarizing the results of the two successive cultures : 



400 hybrid seeds of N and B. 



25 B 



37-5 N ,,.^B 



(Diagram inserted.) 



De Vries further adds : 



"l have, thus far, studied two other successive generations of these 

 same hybrids. They have repeated each time the same phenomenon of 

 disjunction. 



"I have obtained the same results with the hybrids of sugar maize and 

 of starchy maize, in which the endosperms are visibly hybrid at the 

 same time as the embryo." {ih., p. 847.) 



He then states a general conclusion as follows : 



"One may condense the ensemble of these results by supposing that 

 the two antagonistic qualities, dominant and recessive, are disposed in 

 equal parts, in the pollen as in the ovules. 



"if one calls D the grains of pollen or the ovules having a dominant 

 character, and R those which have the recessive character, one may rep- 

 resent the number and nature of the hybrids by the following repre- 

 sentative formula in which the numbers D and R are equal : 



(D + R) X (D + R) = D2 + 2DR + R2 



"This amounts to saying that there will be 25 per 100 of D, 50 per 100 

 of DR and 25 per 100 of R. 



"The individuals D will have the dominant character pure, having in- 

 herited it from the father and from the mother. In the same manner, 

 the individuals R will have the recessive character pure, while DR will 

 be hybrids. These will carry the dominant character apparent and the 

 recessive character latent. 



"One will not be able to distinguish the 25 per 100 D from the 50 per 

 100 DR, except by a second culture." {ib., p. 847.) 



De Vries' final conclusion is : 



"The ensemble of these experiments puts then In evidence the law of 

 the disjunction of hybrids, and confirms the principle I have enunciated 

 upon the specific characters considered as distinct units." {ib., p. 847.) 



The next paper to be considered is ; 



