258 BOTANICAL GAZETTE [OCTOBER 
SUMMARY AND CONCLUSIONS. 
In Erigeron the pollen tube passes down a short distance 
into the sac and discharges the male cells, which bore their way 
through the surrounding cytoplasm. One male cell fuses with 
the egg nucleus, the other with the endosperm nucleus. The 
endosperm nucleus, after fusion with the male cell, rapidly 
divides and soon fills the sac with a mass of nuclei. The fertil- 
ized egg remains some time in the resting condition, doing little 
beyond developing a dense membrane and becoming slightly 
larger. The first wall is transverse, as is usual in angiosperms. 
In Silphium the polar nuclei fuse long before fertilization. 
The pollen tube passes down into the sac and discharges two 
male cells. These cells, in some instances, leave a well-marked 
path through the cytoplasm. They retain their coiled form for 
some time after contact with the nuclei with which they ulti- 
mately fuse. One fuses with the egg nucleus, the other with the 
endosperm nucleus. Before fusion is completed they become 
nearly spherical, being slightly flattened on one side. 
I may venture to suggest that the fusion of the ma 
with the endosperm nucleus is a true fertilization, and not a false 
one (“une sorte de pseudo-fecondation ”’), as regarded by Guig- 
nard. May not the two nuclei—egg nucleus and polar nucleus— 
nearest the middle of the embryo sac both be considered 88 
nuclei; and may not one of them, by some means not yet under- 
stood, have an advantage over the other, and so develop a 
definite structure ? May it not be possible that the fusion 
three cells—the polar nuclei and the second male cell—© 
form the endosperm nucleus imparts to that nucleus an ee 
stimulus to cell division, resulting in the rapid cell multiplicat! 
which immediately follows fusion ? 
That both the fertilized egg and the endosperm n ee 
potential sporophytes seems a reasonable view, yet W° ee til 
fronted with the fact of the fusion of the polar nuclei, and at 4 
the meaning of this is made clear we must remain in cpa A: q 
cerning the true significance of double fertilization. : 
le cell 
ucleus af 
