CENTROSOMES DURING EARLY FERTILIZA- 
TION STAGES IN PREISSIA QUADRATA 
Bv MARGARET GRAHAM 
Hunter College 
(WITH PLATE 8) 
The problem as to the behavior of the centrosome during cell 
and nuclear fusion cannot be said to be settled for either plant or 
animal cells and from this standpoint I am engaged in an investiga- 
tion of the processes connected with fertilization in Preissia 
quadrata (Scop.) Nees. 
My material was collected from gorges around Ithaca and 
prepared for sectioning at Cornell University. I am indebted to 
Professor G. F. Atkinson for the privileges of the botanical 
laboratory there, where for several years I experimented with 
methods of handling the plants and with various killing reagents. 
I also acknowledge the privileges of the laboratory in the Cornell 
Medical College at Ithaca. The material was killed in the field 
in a modified Flemming solution. The sections were stained and 
studied at the botanical laboratory at Columbia University and 
were examined by Professor R. A. Harper, to whom I am indebted 
for a critical examination of my stained preparations. 
Dr. Osvaldo Kruch (оо) observed many eggs of. Riella Clau- 
sonis with one antherozoid in the cytoplasm. He also observed 
that both nuclei before fusion were approximately of the same size. 
Fusion of the pronuclei was not observed, nor were astral rays and 
centrosomes. Since this article by Kruch no other has appeared 
on fertilization in the liverworts. 
I shall describe here only the stages after the egg has been 
penetrated by the antherozoid and when the pronuclei are already 
near together. During this stage the cytoplasm of the egg of 
Preissia quadrata is plainly made up of two zones. ‘The inner zone: 
is granular with rounded bodies forming a dense aggregate that: 
lies in masses around the pronuclei and among the rays of the? 
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