360 BOTANICAL GAZETTE [MAY 
plant types, or even in different parts of the same plant (striped). 
Thus the difference between the green and white plants in both the 
maternal and Mendelian categories depends upon an invisible 
differentiation process in the cytoplasm of the different cells, which 
influences the course which the proplastids take in their develop- 
ment, and the degree of development reached. One is then led to 
inquire at what stage in the life cycle this differentiation, which 
may be regarded as a physiological process, occurs. In the case 
of the maternal types, the irregular distribution of the green and 
white plant-producing seeds on the ear suggests that it may occur 
in the formation of the egg, or even earlier in the development of 
the ear, because of the frequent presence of irregular patches of 
affected seeds. ‘The occurrence of the differentiation at some stage 
in embryogeny would account for the striped plants, in early divi- 
sion stages for the plants with large areas of the pale green tissue, 
and in the later stages for the plants having smaller amounts of 
such tissue. In the Mendelian types differentiation which is 
. probably of a different kind must occur at sporogenesis, like any 
other Mendelian character. The two types of behavior, the 
Mendelian and maternal, are not in the same category, and as yet 
cannot be explained by a common well substantiated hypothesis. 
It is hoped that further studies of cytoplasmic structure will furnish 
evidence of value in the solution of the problem, and show more 
clearly what phases of the problem are to be definitely assigned to 
the physiologist. 
RELATION OF PROPLASTID TO CHONDRIOSOMES.—One of the 
most outstanding questions arising from the present study is that 
regarding the relation which may exist between the proplastid 
of the foregoing description and the minute cell elements which 
other investigators have described under the name of chondrio- 
somes, mitochondria, etc. There is great confusion at the present 
time concerning the nature and significance of these elements. 
It is plain from a survey of the very extensive literature dealing 
with the cell elements of this general class that the opinions of the 
most competent observers are in conflict on many important 
points. It is probable that cell inclusions of many different kinds 
may have been designated by the term chondriosomes, and whether 
