1922] RANDOLPH—MAIZE 359 
size and color in the same cell is characteristic of embryonic cells 
in normal green plants. Since it was in such cells that GREGORY 
reported the presence of the two supposedly different kinds of 
plastids, this interpretation seems to be a more plausible one for 
his observations. Convincing cytological evidence of the occur- 
rence of two distinct kinds of plastids and their segregation to 
different regions of the plant is at present lacking. In view of the 
condition observed in maize, it is clearly evident that visible struc- 
tural differences in meristematic cells cannot be held to account 
for the inheritance and development of chlorophyll patterns. 
All of the plant types, both the Mendelian and maternal, have 
the same initial cell structure, so far as observations have gone. 
It has not been possible to distinguish different kinds of proplastids 
in the youngest cells examined, that is, those of the promeristematic 
tissue of very young stems and the meristematic regions of embry- 
onic leaves. The actually observed differences lie in the subsequent 
behavior of the proplastids with reference to the evolution of 
plastids. 
Whether the proplastids arise by division or de novo, they are 
found to be present in the meristems of all of the chlorophyll types. 
The fertilized eggs of the different strains have not been examined, 
but if they differ as regards their visible cytoplasmic inclusions, 
corresponding differences would certainly be expected in the 
undifferentiated embryonic tissues of these strains; but careful 
examination of such tissues has failed to reveal any differences. 
As already stated, therefore, the differences in such types seem to 
be due to different modes of subsequent behavior on the part of 
proplastids in different plants and in different regions of the same 
plant, rather than to initial proplastid differences in the fertilized 
eggs of the different types. This view is supported by the occur- 
rence of striped plants in the maternal inheritance strain, and also 
in the Mendelian strains which are not here reported. 
It is necessary to account for different kinds of behavior on the 
part of proplastids which are, so far as microscopic examination 
shows, initially alike. Since visible bodies of more than one kind 
cannot be seen segregating, it might be suggested that there is an 
invisible structural difference in the cytoplasm of the different 
