114 A MANUAL OF MENDELISM 



Since the blacks are to the greys and whites together 

 in the ratio 15 : 1, and the last experiment showed the 

 greys to be to the whites in the ratio 3:1, it is clear 

 that we now have a three-pair set of eight groups, as 

 follows : 



That is to say : there are six groups of unseparated 

 " blacks " which, had they been readily separable, 

 would have been separated without doubt. We may 

 take it, therefore, that the two factors X and Z produce 

 approximately the same effect whether they appear 

 together in the same plant or separately, and that the 

 result is still approximately the same even when they 

 are combined in the same plant with Y, the factor which 

 has to do with the production of greyness. 



Professor Nilsson-Ehle carried his experiments into 

 another generation by which the foregoing inference 

 was confirmed, but, as the experiments and the argu- 

 ment are parallel with those in another case we shall 

 take the proof in the other case to stand for both. 



This time the experiments are with wheat grains. 

 The first experiment showed the red colour in red- 

 grained wheat to be dominant to the white colour in 

 white-grained wheat. The following are the necessary 

 details : 



