53 



This segregation, or division, concerns both the female cell (egg-cell) 

 and the male cell (sperm cell) so that 50% of each kind of cell possess the 

 factor for black and the other 50% the factor for white. 



When fertilization takes place between the gametes (egg and sperm 

 cells) of the same plant, as they usually do in self-fertilizating species, there 

 are four different combinations possible, thus: 



Egg-cell. Sperm-cell. Progeny. 



1. Black X Black Black 



2. Black X White Brown 



3. White X Black Brown 



4. White White White 

 From the above it will be seen that should all possible combinations 



be effected and should the black and white gametes be present in like numbers 

 the progeny (second generation, F 2 ) shall consist of individuals of which 

 are black, brown and white. If the black and brown are thrown together 

 into a single group there will be established the proportions 3 black-brown; 

 1 white. 



Nilsson-Ehle (56 p. 6) explains the above principle in the following 

 graphical manner: 



BLACK EGG CELL. 



WHITE POLLEN CELL. 



GAMETES OF THE 

 PARENT SORTS. 



d 



HYBRID INDIVIDUAL (BROWN) 

 (1st. Generation) 



GAMETES OF HYBRID 

 INDIVIDUAL. 



PROGENY OF HYBRID INDIVIDUAL 

 (2nd. Generation.) 



FIG. IX. Graphic explanation of the Law of Mendel. 



