50 BOTANICAL GAZETTE [JANUARY 
and chloroform in which plasmolysis occurred to a much greater 
extent. 
Hence, cytoplasmic streams, nuclear structures, chromatophores, 
and pyrenoids take an active part in the division of cells in Zygnema. 
The streams of granules, collecting where the cell plate is to form, 
marks the beginning; the nuclear changes then proceed, followed 
by division in chromatophores and pyrenoids, while all are correlative 
with the formation of the cell plate. 
It cannot then be said that division of the nucleus, the chromato- 
phores, and the pyrenoids are synchronous. Rather is it true that 
the center of activities of the cell shifts, and with this shifting division 
of the bodies lying in the vicinity occurs. As regards the nuclear 
structures in Zygnema it is apparent that there are no bodies analo- 
gous to the nucleoli found in the higher plants. A large portion of 
the chromatin, or in a few cases possibly all, fuses in the anaphase to 
form one or more bodies corresponding in appearance and position 
to that of nucleoli of higher plants. Instead of waste products of 
chromatin condensing to form one or more bodies in the nucleus, 
the waste products are not separated from the chromosomes, but 
retained in them until after the nuclear membrane disappears in the 
next division. The substances which make up chromosomes and 
nuclear waste products, if such we may rightly regard the nucleoli 
of higher plants to be, are in Zygnema morphologically indistinguish- 
ble. 
The history of chromatin before the formation of the equatorial 
plate may be summarized as consisting of growth, association, and 
condensation of chromatin bodies in groups. These groups may 
be partially coherent, but in no case forma spireme. After equatorial 
plate formation, dissociation into groups follows, continuing until 
the chromosomes reach the chromatophores. 
Although the term chromosome has been used in this account, 
researches as yet incomplete make it exceedingly doubtful whether 
the chromatin bodies in any of the Conjugatae are to be rega 
as at all homologous with chromosomes of higher plants. If we 
restrict the term chromosomes to segments of the tubular spirem,* 
*See MERRIMAN, Vegetative cell division in Allium, Bot. GazETTE 37:178-207- 
pls. 11-13. March 1904. 
