366 BOTANICAL GAZETTE [MAY 
Chondriosomes of widely different shapes have been observed, 
the commonest forms being the granular mitochondria and the 
rod or thread-shaped chondriokonts. These and other types 
are not looked upon as belonging to distinct classes by plant cytolo- 
gists, but rather as transitional stages between granular elements 
and structures such as chloroplasts, chromoplasts, elaioplasts, etc., 
concerned in the elaborative functions of the cell. In animal cells 
the chondriosomes have been seen to undergo marked changes in 
shape (LEwis and LEwIs 40), but it may be that such changes are 
more gradual in plants. The proplastids in maize are of a single 
uniform shape in the mesophyll cells, being granular in the early 
stages and spherical or ovoid in later ones. Rodlike elements are 
present in the epidermal cells, but not in the cells associated with — 
chloroplast formation. This variation in the size, and the different 
reactions to certain methods of fixation and staining have been used 
by workers as evidence for the existence of different kinds of 
elements which can be distinguished in embryonic cells and which 
perform certain definite functions. Prominent workers maintain 
that plastid primordia can be distinguished from mitochondria at 
all stages in their development (RupoLPH, MorrTieER, DANGEARD). 
This conclusion is based chiefly on size differences and on slight - 
variations in fixing and staining reactions. ‘This contention has 
been supported by the statement that unaltered mitochondria are 
present with the chloroplasts in mature cells, the inference being 
that all the plastid primordia have developed into plastids, while 
the mitochondria remained unchanged. The statements of Mort- 
TIER already cited are noteworthy in this connection. The pres- 
ent study has shown that in maize these small bodies in the 
mature cells are without doubt to be regarded as plastids which are 
for the most part in a very retarded state of development. A 
sufficient number of intermediate stages between the smallest 
ones and mature plastids are present to make it appear certain that 
these bodies do not represent a distinct category unlike the pro- 
plastids of meristematic cells. This question of the possible 
existence of more than one type of initial granule has receiv 
critical attention throughout the present study, and inasmuch as 
the origin of the chloroplasts can be traced backward through 
