26 01 ive. Mitotic di vision of tlie nnclei of tlie Cyanopliyceae. 
says (p. 94) „Dieser Knäuel liegt in einer mit wässerigem Kern¬ 
saft erfüllten Kernliölile. Die Ivernliölile wird durch, die Kern¬ 
wandung abgeschlossen, welche eine Hautschicht des umgebenden 
Cytoplasma ist“. In all the Strasburger text books appears 
this same idea with respect to the nucleus. 
Prodeoding on the theory that the lack of the nuclear mem- 
brane was due to the continuous vegetative activity of the cells, 
the writer has tried to produce the membrane by drying up the 
plants and by starving them. Keither of these trials has pro- 
ceeded far enough to warrant any definite conclusions as to tlie 
success of the experiments. Cultures of Oscillatoria tenuis were 
aliowed to lose their moisture slowly, as so often happens to 
these plants in nature. Wlien thoroughly dry, the filaments were 
fixed at once, dehydrated, imbedded and sectioned. Fig. 2 shows 
a section of such a filamenl in which the central body is sorne- 
what overstained. Ko nuclear membrane can liere be seen. The 
visible effect of drying appears to be rather a shrinkage of the 
cytoplasm from the walls, as well as a general contraction of 
the whole nuclear body. It is well known that tlie Cyanopliyceae 
possess a wonderful power of resistance to dessication and other 
adverse conditions.' It would, indeed, be interesting could it be 
definitely proved that, in a dried condition, the nuclei of these 
plants do not themselves enter a special resting state, but that 
they instead continue to carry on as long as possible their mi¬ 
totic changes, only ceasing wlien moisture fails. They could then 
resume at once their interrupted activities on the return to fa- 
vorable conditions. 
The experiment of starving tlie filaments of Oscillatoria by 
leaving cultures for a week and more in the darkness was equally 
unsuccessful in producing a clearly defined nuclear membrane. 
It is probable that the plants were not left long enough in tlie 
dark, for in filaments left there for one week, cyanophycin gra- 
nules were still abundant, thus showing that stored food was 
still to be liad in plenty. Both He gier and Kohl say that tlie 
cyanophycin disappears after a few weeks in darkness. It is 
highly probable, then, that starvation and the consequent Cas¬ 
sation of mitotic activities would not be evident for sonie weeks. 
Even under normal conditions, the nuclei in the vegetative 
filaments of Oscillatoria sometimes seeni to begin, at least, to 
form a resting nucleus. Such appears to be tlie case in tlie 
lowermost cell in fig. 6, in the most of tlie cells in fig, 14, and 
in fig. 16. Such a cross section as is shown in fig. 16 in which 
the nucleus seems to liave a well defined. limitin u membrane as 
well as a sap cavity, was but rarely met with. Usually the cross 
sections appear as shown in fig. 18. I could not, unfortunately, 
make certain of nuclear cavity and membrane in figs. 6 and 14, 
although the resemblance to such structures was indeed very 
striking. 
The absence of a nucleolus in tlie Cyanopliyceae is also given 
by some as proof that the central body is not a nucleus: while 
