344 BOTANICAL GAZETTE [MAY 
NORMAL GREEN STRAIN 
Detailed attention will be given to the development of elnual 
in a normal green plant, and in the consideration of the other types 
emphasis will be placed on the points in which such types differ 
from the normal plants. 
APPEARANCE IN EMBRYONIC CELLS.—The youngest stages 
examined were those found in the cells of the promeristematic 
region of seedlings 36-48 hours after germination. This region 
occupies the apex of the stem, and is composed of undifferentiated 
parenchymatous cells which are actively undergoing division in 
all planes. In undifferentiated tissue in all cases the observations 
were made on subepidermal cells. In such cells the cytoplasm 
contains minute granules which may clearly be seen without the 
aid of special staining methods (fig. 1). These granules appear 
in the living cell as refringent globules, which are constantly 
changing their position in the cell as a result of cytoplasmic stream- 
ing; this movement seems to be a constant and characteristic 
feature of actively dividing embryonic cells. The size of these 
bodies is variable. In the promeristematic region they are rarely 
more than 1 uw in diameter, and careful observation reveals a 
closely intergrading series between these and other smaller ones 
lying just within the lower limit of visibility. Whatever their 
size, these bodies always appear sharply distinct from the homogene- 
ous cytoplasm in which they are imbedded, and in this material 
cannot be interpreted as granular constituents of the cytoplasm 
itself. At this early stage the cytoplasm appears to be entirely 
free from other accumulations which might be confused with these 
small bodies. 
Appearances which might be interpreted as division stages are 
frequently seen, both in the living cells and in fixed and stained 
preparations. In the living cells a condition which strongly 
_ suggests division by a simple constriction and bipartition of these 
bodies is frequently noted, but their extremely minute size oe 
their constant movement make it impossible to follow a single 
granule for a sufficient length of time to obtain direct evidence for 
its division. Moreover, chance association and separation are of 
frequent occurrence, especially in cells displaying active cyto- 
