in Hybridisation 353 



the parental forms, the two others present combinations 

 between the conjoined characters A, a, B, b, which com- 

 binations are hkewise possibly constant. Four classes 

 appear always twice, and are constant in one character and 

 hybrid in the other. One class appears four times, and 

 is hybrid in both characters. Consequently the offspring 

 of the hybrids, if two kinds of differentiating characters are 

 combined therein, are represented by the expression 



AB -\-Ab + aB + ab-\- 2ABb + 2aBb + lAaB 



-\-2Aab + /\AaBb. 



This expression is indisputably a combination series in 

 which the two expressions for the characters A and a, B 

 and b are combined. We arrive at the full number of the 

 classes of the series by the combination of the expressions : 



A-^ 2Aa + a 

 B + 2Bb + b. 

 Expt 2. 



ABC, seed parents ; abc, pollen parents ; 



A, form round ; a, form wrinkled ; 



B, albumen yellow ; b, albumen green ; 



C, seed-coat grey-brown. r, seed-coat white. 



This experiment was made in precisely the same way as 

 the previous one. Among all the experiments it demanded 

 the most time and trouble. From 24 hybrids 687 seeds 

 were obtained in all : these w^ere all either spotted, grey- 

 brown or grey-green, round or wrinkled"*. From these in 

 the following year 639 plants fruited, and, as further 

 investigation showed, there were among them : 



* [Note that Mendel does not state the cotyledon-rolour of the first 

 crosses in this case; for as tlie coats were thick, it could not have been 

 seen without opening or peeling the seeds.] 



C. H. 23 



