No. 460.] STUDIES ON PLANT CELL.—V. 255 
nomena does not become less by this treatment which certainly 
avoids much confusion of expression. 
There is left for consideration one other group of nuclear 
fusions which may have sexual significance although such is 
not obvious, namely the fusions of polar nuclei in the embryo 
sac of angiosperms and the triple unions of the above with a 
second sperm nucleus which is often called “double fertiliza- 
tion." Several excellent reviews of this subject have appeared, 
notably by Strasburger (:00b), Sargant (:00), Coulter and 
Chamberlain (:03), Mottier (:04a, b), and Guérin (:04). The 
explanation of this phenomenon is likely to rest finally upon 
morphological analysis but at present we are uncertain of the 
homologies of the polar nuclei and the part they play in the 
evolutionary history of the endosperm. The most striking 
theory of the endosperm was proposed by LeMonnier (787) who 
suggested that the fusion of the polar nuclei gave origin to a 
second embryo modified to nourish the normal embryo. One 
of the polar nuclei is always closely related to the egg nucleus 
so that in the triple fusions (the sperm with two polar nuclei) 
we have conditions very close to normal fertilization, the dis- 
cordant element being not the sperm nucleus but the antipodal 
polar nucleus. The triple fusions would seem at first thought 
to be rather favorable to LeMonnier's theory although it is plain 
that with such a diverse mixture of chromatin from three nuclei 
the resultant structure can scarcely be called a sporophyte 
embryo from the very grotesqueness of its make-up. Miss 
Sargant considers the fusion of the second sperm with the 
micropylar nucleus as sexual in character but so complicated 
by the introduction of the antipodal polar nucleus that the 
result is a bizarre structure not strictly comparable to a normal 
embryo. In the final solution of this problem we must know 
whether in phylogeny the sperm and micropylar polar nucleus 
fused first and the antipodal entered into the process later or 
whether the polar nuclei began the habit and the second sperm 
nucleus was drawn afterwards into the activities. Should the 
first possibility be established the sexual nature of the process 
would seem clear while in the second the events would be of 
the nature of asexual nuclear fusions. While we know very little 
