12 JOUENAL OF THE ROYAL HORTICULTURAL SOCIETY. 



The Subsequent Generations from the Hybrids. 



The proportions in which the descendants of the hybrids develop and 

 split up in the first and second generations presumably hold good for all 

 subsequent progeny. Trials 1 and 2 have already been carried through six 

 generations, 3 and 7 through five, and 4, 5, and 6 through four, these trials 

 being continued from the third generation with a small number of plants, 

 and no departure from the rule has been perceptible. The offspring of 

 the hybrids separated in each generation in the ratio of 2 : 1 : 1 into 

 hybrids and constant forms. 



If A be taken as denoting one of the two constant characters, for 

 instance the dominant, a, the recessive, and Aa the hybrid form in which 

 both are conjoined, the formula 



A + 2Aa + a 



shows the order of development for the progeny of the hybrids of two 

 differentiating characters. 



The observation made by Gartner, Kolreuter, and others, that hybrids 

 are inclined to revert to the parental forms, is also confirmed by the trials 

 described. It is seen that the number of the hybrids which arise from 

 one fertilisation, as compared with the number of forms which become 

 constant and the progeny of such from generation to generation, is continu- 

 ally diminishing, but that nevertheless they could not entirely disappear. 

 If there be assumed an average equality of fertility in all plants in all 

 generations, and that, furthermore, each hybrid forms seed of which 

 one-half yields hybrids again, while the other half is constant 

 to both characters in equal proportions, the ratio of numbers for 

 the offspring in each generation is seen by the following summary, in 

 which A and a denote again the two parental characters, and Aa the hybrid 

 forms. For brevity's sake it may be assumed that each plant in each 

 generation furnishes only 4 seeds. 



Ratios. 



Generation 



A 



Aa 



a 



A 



: Aa 



: a 



1 



1 



2 



1 



1 



: 2 



: 1 



2 



6 



4 



6 



8 



: 2 



: 8 



3 



28 



8 



28 



7 



: 2 



: 7 



4 



120 



16 



120 



15 



: 2 



: 15 



5 



496 



32 



496 



31 



: 2 



: 31 



n 2"— 1 : 2 : 2"-l 



In the tenth generation, for instance, 2"— 1=1023. There result, 

 therefore, in each 2,048 plants which arise in this generation 1,023 with 

 the constant dominant character, 1,023 with the recessive character, and 

 only two hybrids. 



The Offspring of Hybrids in which Several Differentiating 



Characters are Associated. 



In the trials above described plants were used which differed only m 

 one essential character. The next task consisted in ascertaining whether 

 the law of development discovered in these applied to each pair of differ- 

 entiating characters when several diverse characters are united in the hybrid 



