1900] DOUBLE FERTILIZATION IN COMPOSITAE 255 
of the endosperm nucleus is very constant in size. Many meas- 
urements of the egg nucleolus of &. Philadelphicus were made, 
and in only one instance did it vary from 5.4 M. 
The male cells were not observed in the microspores, and 
no pollen tubes were found except in the embryo sac. When 
the pollen tube (¢, fig. 3) enters the sac, the synergids rapidly 
disintegrate, so that by the time fertilization is effected only 
fragments of their nuclei are visible. One male cell fuses with 
the egg nucleus, and at the time of fusion (fg: 3) cannot be 
distinguished from the egg nucleus. The other male cell fuses 
with the nucleus which is formed by the union of the polar 
tuclei, the product of this second fusion being the definitive or 
endosperm nucleus. 
No male cells were observed in the pollen tube, or in the 
embryo sac before fertilization, so that nothing can be said con- 
os their previous appearance. The pollen tube, after it has 
discharged the male cells, usually contains two bodies of irregular 
7g Vig. 3), which stain intensely with cyanin. They were 
ae in preparations of Lilium. These bodies may be 
plete <a for male cells, especially after fusion 1s come 
althon b othing could be determined concerning their origin, 
of th és its possible that they may have come from a division 
€ tube nucleus, since that still remains to be accounted for. 
age ¥ brief rest the definitive nucleus divides, and in the 
oes examined the cell plate was invariably par- 
the last tj longer — of the sac. The endosperm nuclei, after 
ized eg <a division, are usually multi-nucleolate. The fertil- 
ening ae. the meantime shows little change, except a thick- 
eater the : wall and a slight enlargement ; also it moves dows 
of the syn aig of the sac. At this stage scarcely any traces 
_ Inthe sea a; . ae i the cell plate 
i usually es lvision of the endosperm nuclei the a Be 
per nucle; .  . to the long axis OF the sac. be : a 
Mictopy| esulting from this last division move towat S 
Vaca ar end of the sac, and, occupying the place made 
nt b 
# ARC ay nergids, lie a little above and close against the 
