"8 BOTANICAL GAZETTE [JANUARY 
are formed, which grow and divide. No case of amitosis was 
observed. The mitoses in the cell do not take place simultaneously, 
so that every stage in the division is shown even in a single section 
of the cell. 
The presence of definite chromatophores or plastids has been a 
matter of discussion among various workers on H. reticulatum, 
but in this new form numerous plastids lie in contact with one 
another in the middle part of the cytoplasm. The plastid in its 
earlier stages has an irregular platelike or spindle-like form, and 
it is denser in the outer region than in the center. A most interest- 
ing and important feature in the new form is that the plastids 
per POO 
Fic. 3.—Mitotic figures of various Fic. 4.—Stages showing the forma- 
stages.— X 1500. tion of pyrenoids from plastids.— X 159°- 
have two functions, one to produce characteristic pyrenoids and 
the other to form reserve starch grains. 
The formation of pyrenoids from the plastids is as follows. The 
plastid at first is more dense in the outer part than in the center; and 
then it increases in size. A deeply staining portion differentiated 
from the plastid first appears in the center of the body as a small 
dot, during the growth of the plastid. As the general outline of 
the plastid grows, the dot also grows, and finally the body of the 
plastid reaches its full size and assumes a somewhat spherical oF 
slightly angular form; the dot inside also enlarges and assumes 4 
spherical or slightly angular shape. Thus there is established the 
