1922] RANDOLPH—MAIZE 361 
any particular body falls under this class depends upon the defini- 
tion employed. 
The present study has shown beyond a doubt that plastids 
develop from minute primordia in the different types of maize 
under consideration. What has so far been determined regarding 
the nature of these primordia and the relation which they may 
bear to chondriosomes must be regarded as insufficient to warrant 
an extended critical review of this question. It is planned to 
continue the investigation of this point. . Nevertheless a brief 
comparison with the observations of other investigators who have 
devoted special attention to the chondriosomes may contribute 
something toward a solution of this puzzling problem. 
The development of plastids from granular primordia has been 
observed by many workers, but there is a wide diversity of opinion 
as to the relation of the primordia to other cytoplasmic inclusions. 
One group of workers maintains that plastids arise from chondri- 
osomes (mitochondria) which are permanent cell organs, and which 
correspond to similar bodies described in animal cells (Maximow, 
Pensa, Lewitskt (41), GUILLIERMOND, EMBERGER). GUILLIER- 
MOND (24-34), as a result of many researches on plant cells, believes 
that plastids arise from rodlike mitochondria (chondriokonts) and 
differ from the latter only in size and to a certain extent in chemical 
constitution. Twiss (56) reports that in fixed and stained root 
tip cells of Zea Mays an unbroken series from globular, ellipsoid, 
or short rod-shaped mitochondria to mature plastids can be traced 
from the embryonic region backward, and concludes that mito- 
chondria are normal constituents of the cytoplasm. He believes, 
however, that the evidence for the division of the mitochondria, 
as well as that for their function in heredity, is inadequate. 
EMBERGER (18) reported that there are two kinds of bodies (young 
plastids and mitochondria) present in the cells of certain plants, 
which differ slightly in size and staining intensity; both are to be 
classed under the general term mitochondria. Other workers 
hold that the plastids do not come from chondriosomes, but from 
bodies distinct from them (48, 50, 52, 53, 54). A third group of 
workers (TISCHLER, VON DERSCHAU, etc.) contend that the plastids 
are ultimately of nuclear origin, since they arise from chromatic 
