186 CYTOPLASMIC INHERITANCE 
again there are mosaic branches, white branches, and 
also green branches. Flowers on green branches 
crossed with flowers on white branches give mosaic 
plants, irrespective of which way the cross is made. 
A self-fertilized flower from a green branch gives rise 
to a plant with purely green leaves. If a flower from 
a checkered branch is self-fertilized it produces a 
checkered plant. If a flower from a white branch is 
self-fertilized it gives rise to a white plant. 
Baur suggests tentatively, the following hypothesis 
to explain the case of Pelargonium. The green color 
of this plant, like that of all flowering plants, is due 
to chlorophyll grains and these grains multiply, 
supplying all the cells in generations that subse- 
quently arise with their quota of grains. In the 
white parts these grains are defective in the sense 
that they fail to produce the green color, but retain 
their power of multiplying. If now it is assumed 
that the pollen as well as the egg may transmit some 
chlorophyll grains the results can be explained. For, 
in the division of the cells that contain both green 
(normal) and white (abnormal) grains there will 
arise at times an unequal distribution of the grains, 
and in extreme cases two kinds of branches may arise, 
one with green and the other with white grains. The 
hypothesis calls for transmission. through the cyto- 
plasm of the pollen as well as through that of the 
egg cell. Baur states that until this fact can be 
established the interpretation must be uncertain. 
