138 THE CHROMOSOMES 



white leaves. If the flowers of the green branches are 

 self-fertihzed, the young plants are green. If the 

 flowers of the white branches are self-fertihzed, the 

 offspring have white leaves and these plants perish 

 for want of chlorophyll. From the checkered 

 branches the offspring may be green, or checkered, 

 or white. 



When a cross is made between the flowers borne 

 by branches that are unlike, the inheritance is purely 

 maternal. For example, if the pistil of a white 

 branch is fertilized with pollen from a pure green 

 plant, only white leaved offspring are produced. 

 The reciprocal cross, the pistil from a green branch 

 fertihzed with pollen from a white branch, gives 

 only green offspring, and these remain green through 

 all subsequent generations. 



Correns points out that these results can be inter- 

 preted if the whitening is due to a sort of disease that 

 is carried by the cytoplasm. The egg cytoplasm 

 carries over the disease to the next generation. As 

 the pollen does not bring in any cytoplasm the 

 disease is not transmitted through the male side. 



Baur points out that in several other plants in 

 which varieties- with leaves marked with white exist, 

 as in Melandrium, Antirrhinum, etc., the inheritance 

 is strictly Mendelian, for the Fi generation is green 

 and the F2 generation is made up of three greens to 

 one marked with white. In these cases the color may 

 depend on a chromosomal factor. But there is a 

 case in Pelargonium that Baur thinks can not be 

 explained in either of the foregoing ways. Here 



