410 BOTANICAL GAZETTE [JUNE 
being apparently a chromatophore filled with large quantities of 
starch. The difference in external appearance between those cells 
which are dividing and those not dividing is very striking; the 
individuals whose pyrenoids only showed a thin shell of starch - 
and in whose pale green chromatophore there was practically no 
stroma starch were never found dividing, while those whose pyre- 
noids were surrounded by thick pieces of starch and whose dark- 
green chromatophore contained an abundance of free starch were 
the ones found in division. 
Fixation was in Flemming’s weaker solution, half-strength, 
although other fluids were used. This solution caused some shrink- 
age, but as this was principally in the ends of the chromatophore, 
it did not affect the phenomena of the nuclear and cell division 
that were occurring principally at the middle of the cell... When 
the organisms had been brought into the paraffin in which it was 
desired to cut them, the previous changes of alcohol, paraffin, etc., 
having been made by pipetting off the liquid above the Closterium 
lying at the bottom of the vial, the vial containing them was held 
in ice water for a few minutes. The glass could then be broken 
away and the layer of paraffin containing the plants sectioned. 
Staining was largely with the triple stain, although iron-hema- 
toxylin was used to a limited extent. After fixation in the Flem- 
ming solution all the nuclear and cytoplasmic structures take 
differential staining very easily. 
In addition to the sectioned material, whole amounts were 
stained with iron-alum-hematoxylin, gradually transferred to 
glycerin from the water, and mounted in glycerin. 
The same species, which I consider to be Closterium Ehrenbergii 
and Closterium moniliferum, whose vegetative cells were described 
in my previous paper (27), were found dividing. In my first series 
of fixations (May 2) both of these were very abundant, but in all 
my later attempts I succeeded in getting only C. Ehrenbergit in 
division in quantity, the C. moniliferum having in the meantime 
largely disappeared. As my later fixations were the richer in 
divisions and were the ones upon which I have depended for the 
larger part of my work, it was found possible to work out the pro- 
cess in all detail in sections in C. moniliferum, although I was able 
