MENDELIAN HEREDITY 273 



gateds, when self-fertilised, produced altogether 573 

 variegated and 286 green. Now this is a ratio of two 

 to one, instead of the three to one which would be 

 expected in an ordinary case of segregation. It looks 

 like a 1:2:1 ratio shorn of one of its ones. This 

 is what, in fact, it actually is. Dr. Baur examined the 

 seedlings raised from the seeds of a variegated plant 

 very shortly after the germination of the seeds, and 

 found 77 green, 160 variegated, and 51 seedlings 

 which were almost white and entirely destitute of 

 green. These latter possess no chlorophyll, and 

 consequently die. They evidently represent the 

 homozygous condition of the character, the hetero- 

 zygous condition of which is the variegated form. 

 This case, therefore, may be represented thus, assum- 

 ing that the green is recessive : — 



DR X DR 



(variegated) | (variegated) 



[1 DD] 2 DR 1 RR 



[chlorofhyll-less forms (variegated) (green) 



which perish)' 



This particular case of the Mendelian pheno- 

 menon can, therefore, never have originated in the 

 union of pure dominant and recessive homozygous 

 forms, DD and RE, thus : — 



DD X RR 



I 

 DR 



I 



I I I 



1 DD 2 DR 1 RR 



