1go BOTANICAL GAZETTE [MARCH 
surround them. Figs. ro-18 show various stages in the disappearance 
of the staining reaction in the cytoplasmic vesicles. In figs. 10 and 
11 there is a trace of stain; in figs. 12-14 there is no stain in one of 
the vesicles; while figs. 15-18 show vesicles the contents of which are 
indistinguishable from the surrounding clear nuclear sap. Shortly 
after this stage the membranes around the vesicles begin to break 
down and disappear (figs. 19, 20). 
The phenomenon just described seems to be a constant character- 
istic of fertilization in Peperomia sintenisti, as no fusions were observed 
in which cytoplasm was not taken into the nucleus, although more 
than 50 nuclear fusions of this stage were studied. That the phenom- 
enon is not due to shrinkage in fixing is shown by the regular appear 
ance of the other nuclei in the sac, as well as of all parts of the sexual 
nuclei except the sides facing each other at the time of fusion. © This 
view is confirmed by the further development, when by focusing 
the vesicles can be seen to be completely inclosed within the nucleus. 
This is shown in figs. 12, 13, and 15, where one nucleolus is below 
and the other above the vesicle. ‘ 
The growth of any nucleus must be at the expense of material 
obtained from the cytoplasm, and so it is evident that some material 
must pass from the cytoplasm to the nucleus. The phenomenon just 
described, where a vesicle of cytoplasm becomes nucleoplasm, seems 
to show that all of the essential constituents of cytoplasm may . 
changed into nucleoplasm. . 
The presence of the cytoplasmic vesicle within the nucleus gives 
the nucleus a greater surface for the intake of cytoplasm and this may 
be of advantage to it at this stage. 
The membrane around the cytoplasmic vesicle did not disappe@" 
however, before the cytoplasm seemed to be changed to nucleoplasm. 
This supports Lawson’s conclusion that the nuclear membrane |S 
formed by the cytoplasm coming into contact with the nuclear SP» 
for the membrane here as in other fusing nuclei disappears, probably 
by absorption, when nucleoplasm is on both sides of it. LawsoN 
bases his conclusion on the fact that in the reorganization of nuclei 
the nuclear membrane appears at the time that the clear nuclear sap 
appears outside the chromosomes and in contact with the cytoplasm. 
The same thing appears to be true in the case of Peperomia sintenisu 
