444 BOTANICAL GAZETTE [JUNE 
A. Zimmermann” found that at the beginning of nuclear divi- 
sion the nucleoli pass out of the nucleus into the cytoplasm, and 
that later in the metaphase of the division they are again taken 
up into the daughter nucleus. He advances the proposition 
“omnis nucleolus e nucleolo.”” This process was observed in 
the pollen mother cells of Lilium Martagon, where the nucleoli 
are said to break up into numerous small granules. Zimmermann 
also observed the extrusion of the nucleoli into the cytoplasm 
in Hyacinthus candicans, Fritillaria imperialis, Equisetum, and 
Psilotum. The extrusion was also found in the primary embryo 
sac nucleus of Lilium Martagon and Fritillaria imperialts, in the 
vegetative cells of the root tips of Victa faba, and in the stem 
tips of Phaseolus communis and Psilotum triquetrum. Rosen™® has 
also found nucleoli in the cytoplasm of the cells of roots of 
- Hyacinthus. Zimmermann’s observations were immediately 
disputed by Guignard, Humphrey, and Strasburger. Hum- 
phrey** considers that the phenomena recorded by Zimmerman 
are the results of manipulation. 
Zimmermann believes that the nucleoli which are thrust out 
into the cytoplasm return again into the daughter nuclei. In 
his last work*s he still thinks that this occurs in some cases, but 
that it may not be universal. He considers that there is 4 
fusion of the nuclei even in the cytoplasm, and I have also 
found that this seems to be the case, although generally no 
fusion of micronucleoli occurs until they have entered the 
daughter nucleoli. Whether the nucleoli are real organs of the 
cell of course still remains an open question, but for the divisions 
that take place in the embryo sac of Lilium Philadelphicum, my 
own study assures ‘me that in the prophase of nuclear division 
the nucleoli give rise to a large number of micronucleoli which 
_are carried out into the cytoplasm, and in the metaphase of the 
** Ueber das Verhalten dex Nukleolen wahrend der Karyokinese. Beitrage 7UF 
Pp g! g Pflanzenzelle 2: 1-35. 1893. Tiibingen. 
*3 Beitrige zur Kenn der Pflanz H Beitr. z. Biol. der Pflanzen (Cohn)- 
7: eek ene _ pea, 2]. 
rash ooepoisan nga Ber. dd. bot. Ges. ra: 1o8—117. 1894. 
i hen Zellkernes. Jena. 1896- 
th 3 ey |? pa Ge 
£ 
a HS 
