MENDEL'S EXPERIMENTS 7 



(a) The hybrids' progeny consist of four groups. 



(b) These four groups are to each other numerically 

 in the ratio 9:3:3:1. 



(c) Each group contains equal numbers of true- 

 breeding individuals. 



But it has to be observed, in addition, that, since the 

 dominant and recessive characters which form a pair 

 cannot both appear upon the same plant, the characters 

 borne by the four groups of hybrids' progeny represent 

 all the possible combinations of the four parental 

 characters taken two at a time. The following scheme, 

 in which the continuous lines show the possible com- 

 binations and the dotted lines the impossible, will make 

 this clear : 



Round Yellow Wrinkled Green 



In the experiment in which the original parents 

 differed in three pairs of characters, one had round seed 

 with yellow albumen and coloured seed-coat while the 

 other had wrinkled seed with green albumen and white 

 seed-coat. Thus one carried three of the dominants 

 dealt with in the first series while the other carried the 

 three corresponding recessives. The result of the cross 

 was 687 hybrid seeds, all of which were round with 

 yellow albumen and coloured seed-coats. From these 

 687 seeds, 639 plants were grown which were found to 

 consist of eight different kinds bearing the characters 

 given in the following table and standing to each other 

 numerically in the proportion 27:9:9:9:3:3:3:1. 

 The first character named in the table refers to shape 



