422 BOTANICAL GAZETTE [JUNE 
nuclei are entirely reconstructed, the new wall is about two-thirds 
of the way across in section, and the nuclei move out to the surface 
of the chromatophore and are making their way back to their new 
position before the remaining part is closed (fig. 34). It would 
seem from this that the presence of the two nuclei is not required for 
the completion of the cell division, but that the material for the new 
wall is there and the process is well begun before they begin their 
migration. It will be particularly noted that the new wall is put 
in at right angles to the old side walls. 
It is clear that the younger end of the new individual will be 
covered partly by the new transverse wall that is becoming pushed 
out into a cone (figs. 11-13) and partly by a portion of the old 
parent cell wall. Where these two portions meet, the so-called 
girdle band appears in certain species, but in the two forms under 
consideration it is soon difficult to distinguish the point of union 
of the old and new walls, although it can be seen in individuals 
recently divided (fig. 8). 
General considerations 
FIscHER (14) has already pointed out the fact that it is due 
to the method of origin of the daughter chromatophores by division 
that the ridges of the chromatophore on either side of the nucleus 
correspond, as each ridge was cut in two when the chromatophore 
divided. It is to be further noted that the division of the chroma 
tophore also explains the continuity of the outer granular layer, 0 
which the streaming occurs, across the region separating the two 
halves of the chromatophore. When the chromatophore is pinched 
into two parts, the constriction process takes place inside this 
granular layer, which is not divided, but is left intact to form the 
outer wall of the ring-shaped vacuole. In Closterium, as see? during 
the daytime, this granular membrane is still continuous, and in it 
occurs the very active streaming movement between the two parts 
of the chromatophore. 
The time relation between the division of chromatophore and 
nucleus in these plants is an interesting one. Closterium as seen 
in the daytime has its chromatophore divided into halves. 
eS, e 
two halves are the result of the chromatophore divisio? of th 
