I] and its Consequences 15 



resultant seeds are F^, showing the dominant character 

 yellowness or roundness, but the seed-skins are maternal 

 tissue. Such F^ seeds grow into F^ plants and bear F.. 

 seeds which show the typical mixture of dominants and 

 recessives in the pods (Fig. 3). In each case Mendel's 





YR 



J I? f J J I ii 





<i^ cfw 



f 



Yk 



YK> 



Fig. 3. Inheritance of seed-characters in Pea. The seed of a green 

 round variety fertilised by pollen of a yellow wrinkled variety are 

 yellow and round (i^). The reciprocal cross would give the same 

 result. Two pods of P^ seed borne by the ^i plant are shown. There 

 were 6 yellow round, 3 green round, 3 yellow wrinkled, i green 

 wrinkled. 



observations have been substantially confirmed by later 

 observers, and the operation of similar processes has now 

 been recognized in a long series of most diverse characters 

 in both animals and plants. 



Consequences of Segregation : Homozygote and 

 Heterozygote, 



Before considering the various extensions of Men- 

 delian research, it may be well to indicate in general terms 

 the chief significance of the facts. The first conception 

 to which we are led is that of unit-characters, units 

 because they may be treated as such in the cell-divisions 

 of gametogenesis. It is evidently upon some process of 



