CYTOPLASMIC INHERITANCE 221 



contains both kinds, more white granules than green ones 

 may at times get into a cell, and at other times only white 

 granules will get into one daughter cell, so that a white 

 branch arises. 



In other species of plants that have white leaves and 

 branches and green leaves and branches, the cross may 

 give a different result. Thus in Melandrium and Antirrhi- 

 num, green by white gives green F^ (whichever way the 

 cross is made), in F2 there are 3 green to 1 white plant. 

 In this case the results can be explained as due to the 

 action of genes in the chromosome on the production of 

 chlorophyll in the c^^oplasm — an action of such a kind that 



Fig. 103. — Pelargonium that gave rise to a white branch. (After Baur.) 



the granules do not develop green color unless the (nor- 

 mal) gene is present, in single dose at least. In this case, 

 even if the eggs only transmit plastids, the F^ individual 

 from a white-leaved mother by a green-leaved father is 

 green, because the paternal nucleus introduces a gene 

 that causes the green color to develop in the plastids. It 

 is the segregation of the genes in the germ-cells of the F^ 

 individual that leads to the 3 : 1 ratio in Fg, and not the 

 distribution of the plastids as in the preceding case. 



The most peculiar case is that of Pelargonium de- 

 scribed by Baur. White leaves and branches, and green 

 leaves and branches occur on the same plant (Fig. 103). 

 Self-fertilized seeds from each breed true to color of 

 branch. White to green gives a different result, vis., 



