160 BOTANICAL GAZETTE [SEPTEMBER 
that the process of evolution of one form from another may 
have been very rapid after the development of the nutritive 
region, the coenocentrum. In 4. Portulacae and A. Bltt the 
struggle between sister gameto-nuclei is possibly close, but the 
conditions are quite different in forms possessing a highly devel- 
oped trophoplasmic area in the center of the oosphere, for it 
becomes a matter of much importance which nucleus is the first 
to reach and avail itself of the nutrition. The determining 
factors may be the position of the nucleus, its orientation, or its 
sensitiveness to chemotactic influences. In any event, a nucleus 
which gains more nutrition will contribute its substances to a 
larger fusion nucleus, and consequently leave stronger descen- 
dants to the next generation. Moreover, this action of natural 
selection, aside from furnishing stronger descendants, will foster 
exactly those characters which enabled the parent nucleus to 
prevail in the mother oosphere. In short, a condition obtains 
here which can easily be conceived as one that would conduce to 
a rapid evolution from a multinucleate to a uninucleate oosphere 
through the action of natural selection. It is a manifestation of 
what Klebahn (1899-1900) has termed “‘ Streben nach Einkernig- 
keit der Sexualzellen,” under such conditions that it is possible 
to recognize the cause of the ‘ tendency.” 
A peculiarity, probably a consequence, of the uninucleate 
condition of the oospore of A. Tragopogonis and A. candida 
is the division of its fusion nucleus before the spore passes 
into the winter condition. A series of mitoses rapidly con- 
verts the spore from a uninucleate to a multinucleate struc- 
ture. The division here, as in many of the higher plants, 
may be regarded as the initial step in germination. In the 
species with multinucleate oospores no mitoses occur until the 
long resting period, normally in this case the winter, is passed. 
In such forms, presumably the primitive ones, the intrasporal 
evidence of germination appears when the spore ruptures its 
coat and manifests externally the new activities. It is clear 
that the inception of division in one case is homologous with 
that in the other, and in both it constitutes the commencement 
