'-2('> Olive. ^IKot i«' divisloii ol" tlic miclci nf llic ( 'yanopliyceae. 



says (p. 1)4) „Dieser Knäuel liegt in einer mit wässerigem Kern- 

 siift erfüllten Kernhöhle. Die Kernhöhlo wird durch die Kern- 

 wandung abgeschlossen, welche eine Hautschicht des umgehenden 

 ('vto})lasma ist". In all the Strasburger text books a])jx'ai-s 

 this same idea with respect to the nucleus. 



Proceeding on the theory that the lack of the nuclear mem- 

 brane was due to the continuous vegetative activity of the cells, 

 the writiu- has tried to produce tho meml)rane by drying up tlie 

 plants and by stai'ving theni. Neithor of these trials has pro- 

 ceeded far enough to Warrant any dehnite conclusions as to tlie 

 success of the experiments. Cultures of OsciUatoria tenuis were 

 allowed to lose their moisture slowly, as so often happens to 

 ilieso plants in naturo. When thoroughly dry, the lilaments were 

 tixed at once, dehydrated, imbodded and sectionod. Fig. 2 shows 

 a section of such a lilament in which the central body is some- 

 what overstained. No nuclear membrane can here be seen. The 

 visible effect of drying appears to be rather a shrinkage of tlie 

 cytoplasm from the walls, as well as a general contraction of 

 tlie whole nuclear body. It is well known that the CyaiiopJ/ycean 

 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 

 tliey instead continue to carry on as long as possible their mi- 

 totic changes, only ceasing when moisture falls. They could then 

 resume at once their interrupted activities on the return to fa- 

 vorable conditions. 



The experiment of starving the lilaments of OsciUatoria 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 the 

 dark, for in filaments left there for one week, cyanophycin gra- 

 nules were still abundant, thus showing that stored food was 

 still to be had in plenty. Both Hegler and Kohl say that the 

 cyanophycin disappears after a few Aveeks in darkness. It is 

 highly probable, then, that starvation and the consequent ces- 

 sation of mitotic activities would not be evident for some weeks. 



Even under normal conditions, the nuclei in the vegetative 

 lilaments of OsciUatoria sometimes seem to begin, at least, to 

 form a resting nucleus. Such appears to be the case in the 

 lowermost cell in fig. 6, in the most of the cells in fig. 14, and 

 in fig. 16. Such a cross section as is shown in fig. IG in which 

 the nucleus seems to liave a well defined, limiting 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, unfortunatel}^, 

 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 the CyanopJiyceae is also givon 

 by some as proof that the central body is not a nucleus; while 



