a 4 
426 BOTANICAL GAZETTE [JUNE 
Summary 
1. Closterium divides from 10 P.M. to 5 A.M., and the new half 
has become practically symmetrical with the old one by 9 pans 
2. Division is dependent upon the storage of a considerable 
quantity of starch in the chromatophore and around the — 
3. The chromatophore divides by a constriction located abou 
a third of the distance out from the middle. This constriction 
is due to the enlargement of a ring-shaped vacuole under the plasma 
membrane. 
4. The resting nucleus of C. Ehrenbergii is made up of a bee 
fine reticulum carrying little if any chromatin in the form of granu “ 
At the center of this reticulum is a large compound nucleolus ma ; 
up of a number of partially fused nucleoli. The resting . 2 
C. moniliferum has essentially the same structure, but the nucleo 
at the center are more completely fused. 4 
5. The spireme is formed outside the nucleolus and apparently 
separate from it. During its formation that body breaks mee 
but it is impossible to decide whether its material goes to the oe 
or is used up for some other purpose. No chromosomes ee 
bodily out of the nucleolus as has been described for S deb ei 
6. The spindle is cylindrical, with broad poles, much resem 
that of Spirogyra. 
in ae telophase a dispireme is formed, and in this then ae 
reappear as small spheres which later partially fuse to form larg© 
masses. 
8. The two daughter nuclei move around the chromstea 
between its ridges, apparently in an amoeboid manner, t0 
new positions. 
9. The new end wall is put across in essentially the same Fe 
as in Spirogyra, that is, by a growth inward from the perlp — 
to. Division in these species of Closterium is at gr she 
night process: the chromatophore divides the first mga! 
nucleus the second night. to 
11. The position . the young transverse wall would seem ” 
: d that 
indicate tHat the pointed ends are secondarily fore? ped 
ucleoli 
anner 
Closterium was originally a filamentous alga, which has 
the habit of breaking up into single cells. 
AGRICULTURAL EXPERIMENT STATION 
: URLINGTON, VT. 
