NATURE OF PLANTS 



139 



from one another in one or more factors. If now one of the 

 hybrid four-o'clocks is crossed with the pure white, one half of 

 the resulting offspring will be pure white and one half pink 

 like the original hybrid. The reason for this variation in the 

 offspring will be apparent by studying the diagram, Fig. 86.4. 

 Here we see that each parent (RR and WW) produced gametes 

 having the same color factor as itself and when two gametes 



<$r*V-rR W 



/^- -"\ 



Gametes of l 



/ \ 



mmmvW Wj 



/ A 



Cfemttts ^ ^\ > 



<? mX/Si&( W ) ( yy 



FIG. 86A. Diagram showing distribution of the factors for red (K) and 

 for white (W) in the cross of the red and white four-o'clock; and the subsequent 

 cross of the pink hybrid with the white form. 



derived from these parents unite the resulting hybrid (RW) 

 must contain the color factors of both parents. Note, however, 

 that the hybrid produces gametes like those of the parents, i. e., 

 gametes with the red factor or with the white factor. This is 

 due to the fact that in the formation of the gametes there is a 

 separating out of the factors so that the gametes are never 

 hybrid. They only contain the factors of one or the other of 

 the original parents. The lower part of the diagram shows how 



